Fixed Vane vs Variable Geometry Turbochargers...
04-19-2016, (Subject: Fixed Vane vs Variable Geometry Turbochargers... ) 
Post: #1
Fixed Vane vs Variable Geometry Turbochargers...
There is a culture out there hell bent of removing the VG (Variable Geometry) turbo's form these modern diesel engines. That culture is the same one that spreads bad EGR deletes like a disease amongst the ECM tuner community!. It is Big-Name Big Dollar EGR Delete Companies and all the other piss poor "Tuner" companies that push these so-called "Stage 1" and "Stage-2" type of EGR deletes. Power mods and such!.

I want to address this properly, and thoroughly once in for all,... It is the debate over "Fixed turbo's" vs "VG (Variable Geometry) turbo's" and the truth behind WHY they make their claims.

Fixed Turbo's vs Variable Geometry Turbo's ...

The question I posed was why someone would want to do such a thing to one of these modern diesel engines? ...

To put this into better perspective, Diesel engines run on fuel and air both, and to make the power needed to move heavy loads, they need "Charge Pressure" and "Charge Flow", or Turbo-Boost, as its called. All of these things need to be controlled precisely, and the better control you have over these things, the more efficient you make the engine overall. The differences are a LOT, not a little, and can make the difference between getting 5 mpg or 8 mpg under the same exact load conditions, or 600 Horsepower vs 1000 Horsepower before an engine will overheat and/or fail.

Operating a turbocharger outside of its high efficiency zones (rpm range of best efficiency) can have some serious disadvantages. The engine will become a lot less fuel and/or power efficient. In rpm ranges that are too low for the turbocharger, the engine does not produce enough exhaust flow to push it along well, and in rpm ranges that are too high, the turbo has to deal with excess exhaust flow in some way so that it does not over-spool or over-boost the engine.

Lets first look at lower rpm ranges ...

When your sitting at idle and you press the fuel pedal to get you going, the engine needs both fuel and air to get it going. In the case of a big diesel engine, that positive boost pressure assists in making that power by providing extra compression and oxygen. Here is where you encounter the first differences between a fixed style turbo vs a VGT. A fixed turbo will only spool up when higher exhaust flow hits it. This means that the engine has to start reving up and producing power to push it along.

The turbo "reacts" to this and produces boost to help it along as a result. the problem lies in that to get the engine going, you have to pour in more fuel. More fuel requires more air, but the turbo is not providing it yet. This in turn makes it more difficult for the engine to get up an going. It is known as turbo lag, and sort of make for a "catch-22" type of scenario. More power requires more boost, and to make more boost, you need to be making more power. the only way to overcome this lack of boost is to pour more fuel into the engine than normally necessary to overcome it. this can be so bad on some engines, that they have to fuel the cylinders so much, they produce black smoke, and a lot of unburnt fuel to get them going until the turbocharger catches up and provides enough assist. This is a very inefficient process, especially for someone who does a lot of start-stop with their vehicle.

How can this be fixed??

With a Variable Geometry turbocharger...

A VG turbocharger can be adjusted on the fly. They have such a wide range of adjustment, that the exhaust at idle alone can be used to spool them up (known as pre-spooling). As soon as the computer sees the accelerator pedal move, it can command the turbo to close its vanes and spool up quickly, providing boost right away. This allows the engine to produce power with less fuel and prevents the "black smoke at take off" scenario.

Clearly the VG turbo has the advantage.

What about high at rpm and torque???...

At higher rpm and power requirements, the engine starts to make more exhaust than the turbocharger needs. If not dealt with, it causes the turbocharger to over-boost the engine (providing too much oxygen). This causes the fuel to burn to quickly and violently, or simply too early. This lowers the amount of energy going to the flywheel. this is known as detonation as it gets severe enough. It also has the effect of "getting in the way", restricting the high exhaust flow, as so much is not needed any more to make it provide proper boost. Here is how each of these devices deal with this...

A well designed fixed-vane turbo will have a waste-gate to vent this extra exhaust flow. It is usually adjusted based on air the pressure it is producing. A fixed-vane turbo will start to open this waste-gate and bypass the turbine wheel that drive it. Newer turbos do this very efficiently and effectively.

All turbochargers absorb heat, and all turbochargers transfer that heat into their faces and into the intake air they are producing. One advantage that a fixed turbo has is that the extra heat deflected away from the turbo itself due to the waste-gate opening means less heat transfer into the intake side. It also means cooler internal operating temperatures. This is something that can be an advantage at high engine output in high engine load applications, where the engine is worked hard for extended periods of time.

But it is better ??...

A VG turbocharger with its adjustable vanes can and will have a more precise control of bypassing exhaust gas that is not needed. It clearly is programmable for all situations, including bypassing hot exhaust gas that it does not need. The difference though, is that ALL the exhaust gas flows through the turbocharger even if its vanes are open. The turbine absorbs less heat when it is bypassing, but not nearly at the rate a fixed-turbo will. The housing also stays hotter too, making for higher internal temperatures inside the turbo. Combine that with a lot more moving parts, and it becomes clear that a VG turbocharger by design at high engine outputs can certainly have a shorter lifespan.

Anything with moving parts in it will inherently have more thing to go wrong over time when under high stress. My own experience is that WITH a VG turbocharger, heat is the enemy, but that does not mean they are bad. It simply means that heat must be managed properly for them to live a long life. It is not unusual to get 500-600k miles out of one, vs 800k miles form a fixed turbo. There are always exceptions, but that seems to be the trend. I have seen VG turbochargers make it past 900K miles and fixed turbos make it past a million.

A person could clearly contend that a fixed turbo has the advantage,.. that is,.. if it can be tuned to provide the same efficiency at those same high outputs. -- Hence the "big-power" "big-ego" crowd swearing by them so heavily.

So... the argument rages over them... Which one is clearly better? -- that will likely never be solved, I see both sides of this story.

I have seen people switch from one to the other, and some have switched back again. So far, the results are always the same when someone does this. those results are also always based on how someone sues their equipment. the people who don't use a lot of power, and don't want to push their engine into the high torque regions for hours on end always say the same thing...

People who drive with fuel savings in mind and don't push their trucks hard...

With a fixed turbo, the is the low end response sucks when taking away from a traffic light. To overcome it, they have to program it to dump in a lot of fuel and make smoke, and that keeps their oil darker and sooty. That or just put up with a lot of lag and no soot. There is little to no middle ground really. Some have played with their turbo and engine adjustments to minimize it and strike a balance, but it is never nearly as good as a VG turbo can do. Once the engine gets going, the fixed turbo can be made to be very very close in efficiency to the VG. The engine brakes though for the cummins kinda sucks and is weak in comparison. That they do not like at all.

With the VG, the low end response is great and the oil in the engine stays cleaner. The vg can be programmed in a much wider range of rpm to provide better engine response and overall that provides better fuel mileage. For a truck that is not driven hard, where fuel mileage is top priority, it is night and day. This is so much so, that the difference is thousands of dollars a year in many cases. This is especially true with trucks that have a lot of stop and go or lighter lower torque requirements. It more than makes up on savings than the cost of replacement of a VG vs fixed by 4 or 5 times over. It just has no comparison and puts money in the bank in the fuel savings alone.

People who drive with big power, big egos and high torque demand...

I like to brag about my fixed turbo and all the modifications I have done. Look at me and my big bad-ass 600+ hp truck and how fast I can take that hill. I get just the same or better fuel mileage than I had with the VG, maybe even better... << Of course what they don't understand or say is that the way they drive and push the equipment around IS the problem in itself. They were pushing it hard before, and they continue to do so. Why would they see any losses? -- They are demanding power and torque at a high rate, and their fuel mileage sucks so badly that they don't see the losses at the bottom end.

With the VG, it was holding me back. It was just too small and I couldn't get more power out of it without high EGT's. Burned up 3 of them in 400k miles because I was just abusing them, over-spooling them, and pushing them beyond their flow and temp ratings. For them and their thinking, everyone else on the planet should be the same way... they have somehow convinced themselves that "bigger is better" and no one is going to tell them otherwise.


Personally, I like my +2 mpg above what a fixed turbo could do on my own truck. this is because fuel mileage is above all with me. that is what makes or breaks my profit margin above all else too. The difference in power on the truck with the VG turbo allows for a much better response through BOTH the low AND high rpm ranges, making it much easier for the engine to do its job of moving heavy loads. Having good power in ALL rpm ranges, and not just one narrow band, or above a certain range has large advantages of its own. So, to put it bluntly,... The difference between a fixed vein turbo and a VG turbo is HUGE when it comes to overall fuel savings if your not pushing the crap out of the engine. The adjustably of a VG vs fixed is like comparing the chalk writing on a cave wall to a pen and paper. ... Sure they can convey the same message, but the pen and paper is vastly superior when your not a cave-man towards how you drive your truck and engine.

No matter how you tune a Fixed type turbo, or how you set it, it will only ever be 100% efficient at a narrow engine RPM range. You find yourself becomming a slave to this after a while and then the costs of re-gearing the truck to get it there start to become feasible. More expense that is not needed when you have a VG. Fixed turbos are great for a generator where the engine turns the same RPM no matter what, or for a truck that has to work at 80-90% engine load in higher rpm's all day long and heat is an issue. -- But for a highway truck out on the freeways under varying conditions?,... In my book,, I say forget it!. That is the technology of yesteryear,.. and it is not something we should look back towards, nor consider any more. Engine technology has far surpassed the days of "fixed vane" turbos in a modern truck.

But... But ... What about Reliability!?... Fixed Turbo's LAST LONGER!!!

I have heard this argument so many times it makes me sick!,... It is the brainwashing of the bad delete companies out their hands down, and it has no merit at all when proper methods are used during and after custom tuning and/or a delete (Assuming you live in a country where it is legal). VG turbo's are far superior in their operation, the efficiency they provide, and far Superior in producing raw power when needed too!,.. BUT they are also more complex. Because of this, there are a lot more moving parts that can fail, making their lifespan shorter than that of a fixed-vein turbo. Like mentioned above, the more moving parts to something, it is more likely to fail, and there are more things to wear out. Because of this, We must consider the cost of these things, and their replacement/reliability vs what we want to do. VG turbo's typically last about 400 - 600k miles if cared for, vs a fixed turbo that might last 800 - 900k miles. On a highway truck moving goods from here to there,... The fuel savings and efficiency of a VG turbo alone, pay for their replacement several times over, so there is no question as to which one is Superior, even in worse case scenarios.

No one "Wants" to break down,.. or replace an expensive VG turbo,.. I understand that, so what I recommend is that people care for their VG turbo's properly. Installing gauges into the dash of the truck to help them minimize boost requirement and to keep turbo temps down via a pyro gauge will maximize the life of a VG trubo, and allow for a long lifespan form one, but even if you do not do this,.. they still last a long time, and I have seen many that make it 800 or 900k miles before replacement when not abused.

If an engine is used in some form of competition, where engine efficiency were completely traded away in exchange for raw power, and over-boosting was used to achieve it at the expense of shortening the life of the engine,... IE. A diesel 'Drag-Racing' competition or 'Tractor Pull Contest', in wish case there were absolutely no regard for fuel consumption or efficiency whatsoever,... A fixed vein turbo might make the difference between surviving the pull long enough to get the trophy, or stalling out half way down the track with a failed turbo that has absorbed more heat. I certainly get that,... and I get the fact that there is something to be said about increased reliability,... but at the same time,.. a VG in that same situation can be programmed to NOT over-pool, and NOT over-boost like mad,.. placing the engine in a higher power band overall, giving that driver the edge to push the limits beyond what his competitors can achieve with their old-school ways. Having the proper charge flow allows for far greater power than simply stuffing more and more air into an engine. It actually makes power fall off if it is too much, so a VG will STILL WIN against a fixed turbo in competition!.

No matter how you look at it,.. No matter what you have been told, or brainwashed to believe,... in the case of a turbocharger,... and trying to make a living with your equipment,.. A VGT is still the way to go. All one has to do is care for it properly and they will last a long time, and not let you down!.

So Why the Brainwashing??? ...

Those big-name Big-Dollar brain butcher delete companies (names not mentioned but everyone knows them) who try to brainwash and dupe their customers into buying non-vg turbos to replace their VGT's do so out of sheer ignorance and for higher profits!. All those companies, and many more, ALWAYS claim that VGT's are junk, so I have chosen to respond to this properly, and with detail for others who are, or have considered such a thing...

First of all,... Sadly enough,... Those same companies who claim these things, ABSOLUTELY DO NOT KNOW HOW TO PROGRAM A VG TURBO AT ALL!> ... YUP,... you hear me right,.... I will repeat myself!!!,... Those same "Big Name" companies have absolutely no clue how to program a VG Turbo, or do it properly!. If they did, then they would have come to the same conclusions a long time ago. Custom ECM tuning, and competition/power tuning should in fact, at the very LEAST, involve 3 basic things. It should involve adjusting the fueling, the injection timing (the engine timing), AND the air... Only all these companies,.. well,... must have forgotten about the air,... or do not understand that precise control of air pressure (charge pressure) and air flow (charge flow), are as important as the fuel itself!.

Since they do not re-program, or worse,.. many of them actually disable its functionality,.. after making other modifications to an engine, like changing the fueling, timing, and/or the intake and exhaust components, makes them operate incorrectly, and can destroy, or shorten their life-span in a hurry. Because of this, and the fact that they most likely do not understand how to do it properly, they instead, fall back to the archaic methods of a fixed-vein turbo to get the engine to operate again in a somewhat reliable manner... Only a bit of efficiency is lost,.... and a bit of the performance is dulled,.. and all the other negative things that a fixed type turbo is going to be notorious for, will start showing its face.

What they essentially do is knock the engine back into the stone age out of sheer ignorance, claiming that it is the only way to make one of these modern engines reliable, when in fact they are only hiding the fact that they themselves are the ones responsible for destroying that nice VG turbocharger that is capable of MUCH higher efficiency,.. and most of the time, higher engine power output than the fix-turbo they are trying to sell you. ... It is their way of telling you outright, that they do NOT know how to program a modern diesel engine worth a damn!, nor understand what it takes to make one operate efficiently!.


Here is an all to familiar scenario,... This should spell out clearly, why people end up at places like puke delete companies , etc... it is sad indeed!...

An Old-school style truck O/o is ready for a new truck. We will call him Joe for the sake of this scenario. Joe is a successful chap with money to burn, but he knows that he now needs to upgrade his truck for both better fuel efficiency, and because his truck is worn to the bone, ready for an over-seas auction, where he can still fetch a good penny for it. Knowing much about older engines, he goes shopping for a new truck. After some limited research, he decides to buy a new aero-cab peterbuilt with an ISX CM871. He likes the idea of the advertised 'Stronger' engine brake, and presumably better pulling power than the other brands of motors, so he buys one.

300,000 miles later, his EGR and DPF start giving him a fit, and his EGR cooler cracks. He finds out the hard way, that the EGR components only have a 250k warranty, so he shells out a few thousand to the dealer cursing under his breath about it. 3-weeks out of the shop, and its down again. This time, its a new DPF for a couple thousand more. 2 months go by, and guess what. Engine derate for the EGR valve. Problem after Problem it seems, from this EGR crap, with no end in sight. He knows if he doesn't do something, he is going to go broke, or perhaps worse, loose his long time, well paying customers. One day, he hears some Ill-begotten super-trucker brag how one of those big-name companies who advertise heavily can remove all that crap, solving his problems.

He calls them up, and after a few e-mails and legal wavers, he sends them his ECM. At this point, he cannot afford so easily, the after-market turbo that they heavily suggest for an additional $6,000 with mounting kit, so he only does the ECM for now. 4 days later, he installs the new ECM and hollows out his DPF, etc. throwing away all the EGR junk, welding the pipes shut. At first he is utterly impressed, WoW, such power, but the fuel mileage is nothing to bag about. Well, he thinks to himself, at least the downtime is over and my engine is relia......,POOOW!,.....His turbo EXPLODES internally, putting him on the side of the road. He thinks to himself, WoW, those Big-Name Delete guys were not kidding when they warned me about my junky VGT, they called it outright!. He thinks to himself,.. (but in reality,.. THEY PROGRAMMED IT TO EXPLODE but joe does not know this),.. but wait,...they want another 6k, and they are closed for the holiday.

Crap!, I need a turbo now!. Well, trying to convince himself that it might just have been coincidence, he gets a new VGT from the dealer. Now he is another $3,700 in the hole after towing, etc., but he got his load delivered. At this point, he is now cursing and hating this 'Red Motor' for more reasons than he can count. Doubtful of its reliability now, he is paying very close attention to how it operates. His idle is rough, and it sounds 'Air-Ish', almost like the engine fan is on, but not as loud. He is also noticing that it overheats easily, and that it just does not 'like' all the extra power that big delete company gave it even though he told them he did not want it turned up, so he drives it more carefully, avoiding it.

A few months later, late at night on a lonely stretch of road, out of no where,...POOOW,...SCEEEEECH!!!!,...His new VGT has failed again!!!,...Well, at least it has a warranty right,...?, he calls the dealer and gets towed again. They replace his turbo AGAIN, claiming it must have been a bad RE-MAN. Joe, at this point is doubtful, but he accepts it. Well, at least this time it was free. Now, really babying his truck, avoiding all that power they supposedly gave him, he is set on saving the money for that after-market, supposedly, indestructible turbo. A month goes by, then 2. Perhaps it was just a bad RE-MAN. A heavy load or 3, still running strong, but man, its easy to overheat that motor now.

Then one hot summer day, A tall mountian, he crests, and throws the jakes on high because he knows he is heavy. Down he goes, the motor holding back that 80,000 lbs,...1300, 1400, 1500 RPM's,.....1600, 1650, 1680,....its settling out,...ok, I will let it stay up and hold where it s,...... ;;;;;,. ..wha?,.... ,...BAM,.....BAM,.....BAM,.....BAM,... ,...he slams on the brakes,...white smoke boiling out the stack,...he smokes to a stop,....BAM,.....BAM,.....BAM,...he shuts it down. Another shop, another problem. What a !#$@%%@ Q!#@%$@% Q#$@%#$^%#% junk!!! 'Red Motor' [email protected]$$@$@!!!!, as the mechanic shows him the photo off the boroscope of his cracked head, spouting "It dropped a valve,... You can see where it touched the top of the piston, and it cracked the head"... "You need a new head".

There is still an extended warranty on the engine, so the mechanic grabs a camera to take photos of the broken valve spring, only,...there is no broken valve spring. Several hours over the phone and several e-mails later, he finds that there are reports of several motors doing this with no apparent mechanical reason. Cummins engineering claims it is due to turbo over-spin as the cause and are not sure why. They send an engineer from their labs. A day later, as the engineer is digging inside the ECM with Calterm, "Yup, sure enough,...your Big-Boy delete has the engine brake tables set to 99%, and there is no control of the VG turbo position any more....It killed the head due to excess exhaust back-pressure.,...Oh,...Look,...your turbo is actually programmed to self destruct! ... It is also set to not give any alarms, as well as being programmed to spin 60% faster than is recommended... ...... ........he droves on,..."...

Like a ton of bricks,...Joe now realizes,...looking back at that conversation with that big-name company,...It is clear now why they want you to buy their turbo,...They already knew yours was going to self destruct.... ... They programmed it that way,....

WHY THOSE ROTTEN @$!$# !#$!q$# #@$!$# #$!$# [email protected]#%@%@%@%%^@^@$@$%@$!!!!!!!!.....BUT,..BUT Oh, crap!!! now I can't undo this,...all my parts are gone!,...and my DPF too!,[email protected]$[email protected]$v !#$!34 !#$$#!! 'Red motor' !#$@%#@%..............What do I do now?...

He thinks to himself that he must bow his head and eat the cost of that 'Super-Turbo' they claim to sell to fix this now,...or do I?...Perhaps it won't work,...Maybe it will,... I must now do something, and I feel trapped in their net now, having to rely in them to get me right again...."and oh yea",..The engineer looks at joe,..."This voided your warranty... Have a nice day"...As he leaves.

Several months later, 2 more turbo's, and another cracked head, Joe gets the 'Super-Turbo' Borg Werner kit for another $6,000 out of sheer desperation, and sends his ECM to them again for another $2500 bucks so that they can change ONE SINGLE PAREMETER to allow the retrofit. His truck has suffered much, but he is now happy after all is done. He has now, no engine brake and his engine lost fuel mileage, but not a lot. Maybe only its down .4 from where he had EGR, and .7 from after EGR, but thats only if he drives it in its now, very distinct, 'Sweet Spot', just like his old pre-EGR, Pre-VGT motor had. Now he is looking at spending another $3,000 for re-gearing the truck, so that it will match that fixed turbo "sweet-spot" to improve it a little,...and maybe a Scangauge, micro-blue,...and all the other old school, waay overpriced other mods too... Perhaps some day he will see 7 - 7.5 mpg out of it after all the mods, who knows... When actually if someone had simply programmed the engine and turbo correctly,.. he would have never had problems, and would be sitting at 8+ mpg... But joe will never know it,.. because those big-name delete companies have brainwashed him good by now.


Where did Joe go wrong AFTER his new truck purchase?...


Well, It is obvious that he was caught up in the all to familiar endless cycle of 'DPF nightmares'. Some education and a regular 'EGR Tune-up' on his part, would have likely kept him Away from all the delete stuff to begin with. It would also have kept his costs and downtime at a minimum,... but he chose to instead to throw his problems at someone else. Perhaps he would have never done the delete to begin with?,...Who knows. Regardless, Just like most,... Everyone gets tempted by the prospect of 'More Power' and/or 'Better Fuel Economy' via a 'Delete', ... After-all that is what those guys advertise,... so I will move onward,...

His biggest mistake on the delete, was to pay someone good money for an ECM tune that clearly was set up to cause turbo and other eventual failures. A good Custom tune would have had the turbo operate correctly, and within its limits. Would his VGT have failed?,... eventually,... but not for another 300k+ miles or more, as a function of normal wear. VGT turbo's are well known to have a shorter lifespan than non VG's, they simply wear out from constant VG ring movement. The EGR itself accelerates this process, so removing the EGR, if mapped correctly, the turbo will last just as long, or perhaps longer than a fixed type turbo any ways.

He did in fact get a BAD delete,... Those companies leave you with only one option in the end... A turbo that is not controlled by the ECM. This patches the problems in the bad delete, but at the cost of fuel mileage, engine efficiency, and power. Sure they turned up the power of the engine with the ECM,.. but that power is difficult for it to achieve with that now fixed turbo. A well calibrated VGT turbo on a highway truck will easily improve fuel mileage by as much a 2 mpg, and can provide reliable power well beyond the range of that Borg-Werner Big-Boss crap of a turbo they sell.

This brings me now to the bold statement of "Why someone would want to do something so absolutely stupid". A VGT vs non-VG Very easily yields more than 1-1.5 MPG than a non-vg in its same place on highway vehicles, because RPM, load conditions, and speed, are always changing. A VGT compensates for ALL of this, as well as reducing back-pressure fluctuations greatly, resulting in MUCH higher engine efficiencies. IT IS THEREFORE IMPOSSIBLE for a non-VG turbocharged engine to keep up with this, under varying conditions. A pre-EGR, pre-VG engine (ie. Gliders), CANNOT HOLD A CANDLE to a Custom tuned, efficiently programmed VGT Engine with its VG turbo!.


Screw you and your ignorant pre-egr, pre-VG Brain-washig Glider-kid junkyard trucks!!!!

I will replace my holset at 600+k and smile quietly, counting my profits.

It seems that I have a strong dislike for a few of the 'Super-Tuner' shops out there,...I suppose it is because I have revealed their bad practices to the world, and the more I, and others discover, ... The more the average truck owner, considering such things, should be aware of, and concerned about.

I ask for nothing in return, nor am trying to promote myself, or any products. I just like to help other truck owners, nothing more,... and am well known on several other trucking and ECM editing forums to be the loudmouth that reveals all the bad practices and dirty secrets that they do not want others to know about... I am disliked by just about all of the 'Super-Tuner' multi-million rip-off shops, and know it. Some have even offered to pay other forums to shut me up, and others continually threaten this site and what I say because the truth hurts their bottom dollar!.

To them, I have become the one guy who has begun to make them accountable for what they do through educating other truck owners, and it is beginning to hurt their business. I do voice a strong opinion about it at times, but not with an intent of argument. That is where I stop short. I only wish others to learn and discover for themselves, what I have seen, so they can form their own opinion. I have hard evidence, backing what I say toward them,... but I will not post it directly, It would give them an excuse to try and sue me for giving their horribly bad programming away,...

That is WHY I made my own forum,... So that I can post my opinions and information, and it not get deleted like it did over on TTR, and other places!,... and after all this time,.. after several years now, of me revealing their bad ways,.. and bad things they do,... They STILL HAVEN'T CHANGED THEIR WAYS!!!,.. It is sad indeed how these places make so many millions off of truckers and their trucks,.. butchering their engines,... all the while telling them lies!.

It truly makes me sick to my stomach when I hear another O/O brag about them,.. or see their trucks lined up at the truck shows,.. or see someone trying to justify all the money they wasted with those clowns,.. telling themselves that it is "ok"....




- I would not even consider driving a truck with a flat nose,.. or a fixed-type turbocharger! --- I actually want to turn a profit for what i do, and could absolutely care less what the equipment looks like. To me it is simply a truck designed to move freight in the most efficient manner possible, so that it makes me as much money as it can that I can take home and keep!. There is no profit any more in a flat nose,.. or chrome rims and hood scoops,.. and there is no money in old-out of date tech non-vg engines designed to drink fuel at a rapid rate!.--- So as far as I am concerned,... they can ALL go to the junkyard where they belong,.. or to a museum where old farts can brag about the days when fuel costs 3 cents a gallon or whatever it was back then! -- I live in the 21'st century and I am proud of it,.. and I will do what it takes to be profitable above looking good any day. that is what makes me happy,.. and NOT some Dinasuar of a truck with a flat chrome front end that was designed in the 1850's, and a turbo that was designed for a generator!.

And for those who disagree and have old junk trucks they pour endless fuel money into ----



User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
 Thanks given by: Dedicated07 , vasyaha
04-19-2016, (Subject: Fixed Vane vs Variable Geometry Turbochargers... ) 
Post: #2
RE: Fixed Vane vs Variable Geometry Turbochargers...
I feel better now . For awhile I thought you never gonna write like that again.
04-19-2016, (Subject: Fixed Vane vs Variable Geometry Turbochargers... ) 
Post: #3
RE: Fixed Vane vs Variable Geometry Turbochargers...
I had an idea like this for a while.
I think I't would be the best of every world. Not for most, I assure you, but for my truck that only sees seasonal local work and competition use, I think it would be cool. Best of all worlds. Quick spool and response of the vgt, but the high charge flow of a large fixed vane. Should allow to be able to relax the sliding ring in the vgt, lowering back-pressure, yet still provide a large cfm of air without over spooling anything.
Just theory anyway

Attached File(s)Image(s)
04-19-2016, (Subject: Fixed Vane vs Variable Geometry Turbochargers... ) 
Post: #4
RE: Fixed Vane vs Variable Geometry Turbochargers...
I don't know why? Probably experience!? But the key to ingenuity is SIMPLICITY !!!
04-19-2016, (Subject: Fixed Vane vs Variable Geometry Turbochargers... ) 
Post: #5
RE: Fixed Vane vs Variable Geometry Turbochargers...
(04-19-2016 )Rig Wrench Wrote:  I had an idea like this for a while.
I think I't would be the best of every world. Not for most, I assure you, but for my truck that only sees seasonal local work and competition use, I think it would be cool. Best of all worlds. Quick spool and response of the vgt, but the high charge flow of a large fixed vane. Should allow to be able to relax the sliding ring in the vgt, lowering back-pressure, yet still provide a large cfm of air without over spooling anything.
Just theory anyway

i want one!

User's Signature: 52 41 57 5a 45 20 53 4d 45 4c 4c 53
04-19-2016, (Subject: Fixed Vane vs Variable Geometry Turbochargers... ) 
Post: #6
RE: Fixed Vane vs Variable Geometry Turbochargers...
Look like it is from a 6.4/6.7 powerstroke with a twin turbo set up. I have the 6.4 and like the setup low boost when none is needed but mash the pedal and hold on
04-19-2016, (Subject: Fixed Vane vs Variable Geometry Turbochargers... ) 
Post: #7
RE: Fixed Vane vs Variable Geometry Turbochargers...
My idea was to use the stock he551 and spin that into maybe an S500 or hx80???? QSX injectors, and cut pistons one i gotta pull the head off. Lol. I think it would be awesome with the adjustability of the cm871. Haven't seen a compound setup with a vgt on a big truck yet
04-19-2016, (Subject: Fixed Vane vs Variable Geometry Turbochargers... ) 
Post: #8
RE: Fixed Vane vs Variable Geometry Turbochargers...
(04-19-2016 )Erics diesel Wrote:  Look like it is from a 6.4/6.7 powerstroke with a twin turbo set up. I have the 6.4 and like the setup low boost when none is needed but mash the pedal and hold on

Yea. I think this is an ATS setup for a dodge pickup. Theory is the same though
09-19-2017, (Subject: Fixed Vane vs Variable Geometry Turbochargers... ) 
Post: #9
RE: Timing Actuator Closing Delay
(09-18-2017 )2strokeforever Wrote:  Could the reduced restriction of the WG turbo be the sole contributer?


The exhaust turbine of the he551ve is not a significant restriction on a 600 hp engine...

Hoping to not hurt any feelings here, but heres what I think, and it does explain why people are seeing better mileage with the non variable turbo

The he551 compressor is too small for full load, running too hard for good efficiency... The hx60 is bigger and runs in the sweet spot when pulling hard which translates into less power required to spin the compressor and less heating of the air that is being compressed

My narrow minded point of view Is that you dont need or want boost till your egts are getting near max, so in my eyes building boost quicker at low load is not a good thing

Some people are confused as to why the isx comes with a variable turbo, its not for reduced lag or less backpressure....
It was sized so they can add backpressure at will to force the exhaust to flow through the egr and into the intake

It would be impossible to do that if the turbo were sized properly and made more boost than backpressure, it wouldnt flow the right direction

My trucks he551ve turbo is most efficient at 1200 to 1300 rpm (real world testing )

My 550hp truck flows 105lb/min which is .8 kg/second, now look at this handy compressor map from cummins
Holy shi#t were completely off the map
With the he400 were off the map at 1300rpm

Unfortunately cummins dosent publish effiency lines, so we will steal a very similar one from garrett so we can better understand

Notice in the center there are little numbers, that is the percentage of efficiency... Notice at low boost middle of the chart its 80% thats great (if you are 1200rpm ith your foot to the floor)
Now lets go to full throttle 1500rpm 105lb/min 38lbs boost (pr 3.75)
Were off the map somewhere near the 60% range or worse. Its a double whammy because that 40 percent loss dosent just go away, it drags you down more because it shows up as a increase in intake manifold temperature

{image removed, not representative of what is described}

Now here is a pretty close map to the he400 compressor, find me 105lb/ min on this one at pr 3.75
Hell find it at 50lb/ min and pr 2 (1500rpm 14lbs boost), wait its no good there either....

{image removed, not representative of what is described}

{**Content removed by protection bot** - suspected advertising.}

(09-18-2017 )2strokeforever Wrote:  ...
Hoping to not hurt any feelings here, but heres what I think, and it does explain why people are seeing better mileage with the non variable turbo

That statement is very misleading and for most people, has been proven to be, is, and would be untrue. There are cases where there are exceptions so it will always remain a debate with 2 sides.

Your post seems to follow the typical "salesmans pitch" through bent data and a skewed opinion and it misleading as a whole. it is a tactic that people who love to troll others use and will be watched closely if it continues. I was simply tempted to just delete the post but I will respond to it instead out of professional cutesy for now. I likely already know there is no reasoning with someone who is hell bend on their views if all they are here to do is troll my forum in sophisticated ways.

So that is a NO, my feelings don't get hurt,.. I just don't tolerate mis-leading information masked as fact. It is no different than the stuff you find on Internet sites selling products, where the sellers are hell bent on their data and findings =,.. yet when someone else attempts it,.. it never seems to quite pan out.

I reject that kind of stuff real quick around here and consider it the same as those "aligned fuel molecules" running around in fairy-dust land after you buy that gimmick product that is nothing but a magnet shoved into a piece of pipe.

That being understood up front (I.E. your post is worded more as a sophisticated form of trolling more than a discussion) ...

An engine close to, or under full operating loads, where it may start to reach or exceed operating capacity of one turbocharger vs another is the only places where the differences you are referring to will normally be seen. IF YOUR OWN EXPERIENCE does not match this,.. then YOU/THEY HAD SOMETHING SET WRONG when you had the VG/ smaller turbocharger on it at lower/average operating load torque levels.

I know of several people who HAVE switched from VG turbochargers that were dialed in correctly and VERY EFFICIENT ALREADY! to non-VG turbochargers and every bit of what they do that is not under higher torque/power loads were measurably LESS EFFICIENT!. - Every one of them LOST fuel mileage on average under varying load conditions, though some of them got their trucks very close after much tweaking. The problem is that when they got them really close, a loss in engine response at lower rpm ranges resulted. The only way to overcome lag wioth no control of the turbo is to add excess fuel to push it along at low rpm. There is no longer the option to adjust positive pressure (no more VG), and when doing this. Adjusting the enigne to provide a better response produces unburnt fuel to go along with that better response. I. E. -- less efficiency until it can catch up to itself again or get up to a region in rpm range where it can be overcome.

The bigger the turbocharger, the more of a problem. It is because it takes more positive flow to get it spooled up. Its efficiency ratio (like in that chart you provided) is a direct reflection of this and you can see it fall off sharply at the bottom end unlike the smaller turbo's.

I.E. -- One size can never fit all.

Not everyone is hell bent on making 600+hp out of their engines and having to apply it to the road for long durations. For those that do,.. I am not in complete disagreement they alternatives may work better for them when using their equipment in these ways, or taking it outside of factory designs,.. but to profess such things in a lesser context as a blanketed statement is outright wrong and nothing but a sales-pitch.

If your statement here was even slightly correct then there would be no way in hell that my own truck WITH ITS HE551VE VG TURBOCHARGER would have gotten the 8.3 mpg to the fuel pump 2 days ago between Seattle, Wa and Chatanooga, Tn loaded 79,960 lbs gross with a load of onions!, running it at 58-60 mph. Hell, even the scale house in Wa said I was at 33,997 lb on the back tandems of the trailer.

(09-18-2017 )2strokeforever Wrote:  The he551 compressor is too small for full load, running too hard for good efficiency... The hx60 is bigger and

At 600hp factory torque curve, AT OR CLOSE TO FULL OPERATING LOAD ONLY, the HX60's higher flow capacity will match, and even could possibly outshine a 551VE, but only by small amounts. they did design it to handle a wider range of rpm than other brands, and it is a good match to a 15 litre ISX, but to claim it is more efficient overall is a lie. in a limited range of rpm, and only in its "sweet spot" as you have put it. Not because the 551 is too small for the job.

-- Problem is,.. most people who haul freight on the highways DON'T OPERATE THEM AT FULL/HIGH OPERATING LOAD FOR HOURS ON END!. They drive down the roads at 28-38% operating loads long term and at a wide range of operating rpm and torque. This totally negates any slight gains on the upper end that one would see. Your statements are consistent with someone who only tortures their equipment with high operating loads consistently, and this forum is NOT about power and all the crap thinking that goes with it.

That is why I disagree.

This forum is about saving money, and making a profit with your equipment, not butchering, torturing, and adding power + all the crap that goes with it.

(09-18-2017 )2strokeforever Wrote:  ...
My narrow minded point of view Is that you don't need or want boost till your egts are getting near max, so in my eyes building boost quicker at low load is not a good thing

It seems to be exactly that.. unfortunately, a limited view.

- What makes efficient combustion is the proper final crank angle(angle of peak cylinder pressure), the proper fuel air mixture and homogenization of that mix, its volatility, the proper oxygen level, and its burn length. The "air" (charge flow) has a proper "Q" (quiescent point) in all torque ranges and rpm ranges and in a turbocharged diesel engine, it is always a positive pressure value (meaning some slight assist in positive pressure) through all those ranges needs to occur. It is not a car engine that simply uses boost on occasion to overcome its vacuum at the intake. How much positive pressure is a delicate balance. Believe me,.. I spent several years going down the roads in a multitude of driving conditions and terrain to perfect those ratios in my own equipment,.. guess what -- It would not have been possible to achieve such extreme high efficiencies if I HAD NO CONTROL OF THE TURBOCHARGER!.

(09-18-2017 )2strokeforever Wrote:  ...
Some people are confused as to why the isx comes with a variable turbo, its not for reduced lag or less back-pressure....
It was sized so they can add back-pressure at will to force the exhaust to flow through the egr and into the intake

It would be impossible to do that if the turbo were sized properly and made more boost than back-pressure, it wouldn't flow the right direction

Another mostly untrue statement.

IT IS IMPOSSIBLE!!! -- For ANY TURBOCHARGER WHATSOEVER!! ---- ANY!!!!--- to produce MORE POSITIVE PRESSURE than the pressure driving it!. -- If it were,.. you would be able to make a perpetual motion machine out of one and you would solve the worlds energy problems for the rest of eternity!!!

Your statement HERE is SO INCORRECT IN SEVERAL WAYS it is NOT EVEN FUNNY! -- It seems to point towards sheer trolling arrogance more than anything else, hence my statements above.

Here is a decent reference on turbocharger efficiency vs exhaust heat and charge flow for those who want the correct answers instead of some moron of a troll who is good at twisting words and mis-leading others ...

The design of a variable geometry turbocharger FIRST AND FOREMOST is for improved engine efficiency through a wider operating range vs fixed. -- YES, the ECM DOES have the ability to use it to increase back-pressure on the exhaust, but it does so at the cost of making MORE OXYGEN and excess pressure into the cylinders as it does so. It has been found that it is not until SOMEONE SCREWS UP THE EGR FLOW AND PUTS A BLOCK PLATE IN that is starts demanding the exhaust back-pressure be increased unnecessarily to force gases to the intake because it is now CONFUSED!. It will it resort to making back-pressure simply to supply the EGR circuits if it is not corrected properly.

(09-18-2017 )2strokeforever Wrote:  ...
My 550hp truck flows 105lb/min which is .8 kg/second, now look at this handy compressor map from cummins
Holy shi#t were completely off the map

Where did you get this number??

15 ltr engine @ 40 lbs boost, and moist, dense air = roughly 0.54 kg/s

To get to 105, you would have to be pushing 58 lbs boost!. That or running more than 2600 RPM!.

Realistically, for example, the CM2350.... 1800RPm, 33lbs boost / AT 600 HP... = roughly 0.49 kg/s. This places the He451VE right at its upper edge of recommended range according to the cummins chart you just posted. I have measured MYSELF, comparing the exhaust back-pressure sensor to the intake pressure sensor 2.8 - 2.9:1 efficiency rating of the 451VE and guess what --- IT MATCHES THE CHART YOU POSTED EXACTLY,.. PLACING IT SQUARELY IN THAT EXACT SPOT!!!. -- did they under-size it? -- NOT REALLY according to THEIR OWN DATA. - BTW: the 451VE is in actually between the HE400 and HE 500 series on that chart and is fairly new.

Would the HE551VE be better suited at 600HP and only 32 lbs boost? -- YES,.. You can see that in the chart as well,.. but it starts to fall short by the time you get to the HX60. It still falls in place, but on the VERY BACK EDGE of its efficiency range. In fact, if I owned a truck with a CM2350 engine and I just simply hated a VG turbo and didn't care at all about fuel mileage because I lived in a country where I simply could not get parts for it, or i was torturing the engine and wanted better heat flow out of the engine to increase component longevity ... My second backup choice would be a HE500 series for a 600-hp cm2350. It clearly is better suited for that operating range. The only reason for considering an HX60 on that model engine would be if it were being used under high demand conditions,.. then the HX60 would be more lenient of heat flow,.. but not really efficiency gains above the 500 series. It is anyone's speculation as to why the red maker supplies the Cm2350 in foreign countries with the Hx60 on them already (like aussie land where they tend to torture their engines) but I would put a good bet on that fact alone. It is after-all inside the operating region they recommend. It could just simply have been a matter of compatibility/ease of manufacture considering it is already used on older model engines. Only they, in their engineering dept. can answer that,,. not you or I.

When it comes to the CM870, 871 and its 36-39 lbs of boost,.. more pressure and more flow is required to make the same HP!!!. This is because of a lower compression ratio among other things. A larger turbo with more flow capacity is required than that of the newer engine. If I were to apply the formulas to the CM871 that I own,.. at 450HP where mine is set to,.. The HE451VE would actually be slightly more efficient in fuel mileage. -- I have already had thoughts of trading turbos with the 451VE if I have to replace mine again just to confirm this.

WHAT HAS BEEN CLEARLY MISSED IS --- It is NOT about turbo size alone... An engine requiring LESS BOOST PRESSURE does not need as much umph out of the turbocharger. Period, and the more you over-size it,.. VG OR NOT!, the more you loose efficiency when all that extra umph is not needed.

--- Even the 600HP engines with larger CAC units at a full 2,000 rpm are not set in their programming to demand more than 0.61 kg and that is the upper extreme. Typical for a 550 at 1800 rpm is 0.55 kg/s at best.

EVERYTHING you have spewed onto my forum shouts that the team of engineers at the red engine maker GOT IT WRONG!?? -- and that you have it figured out for them? -- EVEN WHEN THE DATA YOU POSTED POINTS CLEARLY AT WHAT HEY DID WAS NOT WRONG!!!??? --- Maybe you should go offer to fix their mistake for a few million dolors eh? -- Maybe their engine can gain a bit more MPG? -- And they can beat their competitors out of the market in engine sales with this fairy dust of an idea???? -- Sorry, but I live in reality here on planet earth.

-- It is clear to me now that you are looking to "sell everyone" on this fictitious world of some kind of VG turbo efficiency nightmare, possibly to sell and justify what you do to others? -- But I am not about to buy into it, not one bit. I consider it trolling at best, or indirectly phishing for information.

If you really think you can put a non-vg turbo on a truck that is breaking 8mpg fully loaded to 80,000 lbs and gets 16+ mpg bobtail and beat ITS EXISTING HE551 VG TURBO with more than 580,000 miles on the turbo already,.. your more than welcome to fly out of Canada where you are at with a brand new one (and any mounting hardware needed) so that we can put it on my truck. I will have my wife drive it for a month or so and she will be able to tell right away. My fuel mileage software is sensitive to one tenth accurately all 48 states, especially now that is has 1.1 mil miles of comparison data to bank itself on from each state to each state individually. -- Otherwise,,.. you had best step on soft ground because I get tired of repeating myself on this subject over and over.

The rest of what you blastered onto my forum with is just too ridiculous to comment on.

-- I will kick you off here if you don't play nice,.. I know who you are and the "other" auto forum you came from. Sorry, but I don't promote a bunch of hyped synthetic data meant to spread mis-information.

User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
 Thanks given by: Dedicated07 , the missing link , HotRod

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