No boost......no power

[Rawze]

(03-13-2020 )Roysbigtoys Wrote:  ...
Do I go with the stock turbo he offers or the modified one?
...

He has made a few modded turbo's for the isx where he uses a different cold-side impeller. It has some changes to it that possibly could improve the turbo's response, but at what costs to the AR ratio, etc.. is still unknown. The feedback from the few people he has made them for is nothing but speculative claims and I don't tend to trust this type of thing as proof of an improvement at all, as every turbo he has done this to,.. the old one was bad and there is no comparison basis (nor any real measurable data) at all on any of those trucks.

Mr. Hag said he is going to, at some point, said he will do some comprehensive testing and measurements of a turbo on a truck that there is nothing wrong with. I told him to look specifically at A/R (exhaust pressures) vs. intake manifold pressures, and heat soak of the manifold, etc. ... Then have this mod done, then do the tests again to see what changes actually happened while only replacing the one impeller alone to see the real differences.

-- I saw a New Zealand turbo company try this same types of mods back several years ago with Holset turbo's and they could not get any real measurable gains whatsoever out of it when comparing healthy turbo to healthy turbo on same engine under came conditions no matter how hard they tried. They thought they had some gains,.. truck made more boost pressure that it did before when turbo was set to same position%... but the A/R also went up,.. and when they adjusted the turbo positioning back down achieve the same exact pressures to get the right fuel-air-mix again... they lost efficiency,.. or it became exactly the same again.. There were no actual gains whatsoever (and sometimes negative results) when apples were compared to apples.

I.E.> Unless I see some actual data showing the differences, and not some claims by people who had a bad turbo to begin with,... then I have zero trust in it till then.

I was at his shop recently, looked at the differences in impeller design ... they are indeed different and at a glance, it would seem an improvement ... but then you start considering what the exhaust side turbine has to do to push that thing (where most of the efficiency loss always occurs), and then the need to slow down the turbine to get back to the same exact intake pressures again,... and all speculation one would assume, just by looking at it, goes quickly out the window. Only testing would reveal if the exhaust pressures were indeed improved, as it is that side of the turbo that is the one that dictates totally,.. what will happen good or bad... Not the intake.

Generally, improving the impeller design of a turbo leads to either a higher A/R ratio, or a lower one. Withing the area/realm of all other things mostly optimized already ... impeller changes that lower A/R ratio is often a power improvement, where changes that leat to a higher A/R usually results in an efficiency improvement at the cost of power handling. Also, the lower the overall A/R (bigger turbo with more air flow), the less responsive the turbo becomes on its exhaust side, the less fuel efficient it becomes, and the more it is able to handle higher power levels with less internal/manifold heat absorption. The higher the A/R, the more responsive it becomes, the more fuel efficient it becomes, but lower overall power capacity starts to set in.

There is little to no such ting as one size that can do BOTH. The more modern VG turbo's vastly improve this fact and greatly lessen this issue (hence why anyone would be dumb enough NOT to use VG turbo these days for most applications) ... but even within the realm of VG turbo's where it is greatly lessened ... this issue of "one size cannot do both, handling higher power and higher efficiency in all scenarios" still exists. -- Hence there are many different sizes of turbo's out there, including VG's that vastly narrow this problem.

-- looking at it in a different perspective...

At the end of the day ...


GIVEN THIS SCENARIO: If an engine needs exactly 30 psi of boost(intake) pressure to achieve a proper fuel-air-mix at a certain RPM and torque output ...

2 things need to be seen to conclude an actual improvement. otherwise, you are only fooling yourself because all you did was either A). Improve the overall power capacity at the expense of some efficiency,.. or B). Improve efficiency at the expense of overall power/capacity.

This would totally and completely dictate if a different impeller desing would help or hinder someone. - Someone with a lot of power consumption is going to suffer extra head and power losses if the turbo suddenly handles less overall power/capacity,... and someone who has all things fuel efficient and does not use a lot of power will suffer suddenly the turbo can handle more power/capacity (that is not needed / ever used), but it did so at the expense of some fuel efficiency.

-- Knowing wicht way it swings after this type of mod happens is the key to making that proper decision and knowing if there will actually be something that can help (or hinder) someone based on thier own individual needs.

For an actual improvement across the board to happen though ... that is the difficult part. BOTH things at the same time need to happen.

- here are the 2 things that needs to be tested/measured to find out the actual results (referring back to the given the 30 psi scenario mentioned above)...

-- What was the exhaust resistance (exhaust pressure vs intake pressure), both before and after, during that same 30-psi intake pressure, same rpm, same power output.

-- What was the live fuel consumption, both before and after, during that same 30-psi intake pressure, same rpm, same power output.

-- What were the manifold temps (heat soak), both before and after, during that same 30-psi intake pressure, same rpm, same power output.

-- Those are the exact questions that need to be answered to solve this instead of blind guessing and people's feelings.

I.E.>>

-- If it improves only power/capacity,.. guys with big power will brag about the impeller mod.. and guys with high fuel mileage and low power requirements will complain about it costing them fuel.

-- if it improves efficiency at the cost of power/capacity... guys with big power will complain their turbo does not last as long, run hotter, etc .. and guys with high fuel mileage and not big power requirements will brag about it and claim it is great.

Knowing what your needs really are, and knowing a definitive answer to what the changes result in,.. are the key to it all. -- AND if the impeller designer has gotten that lucky as he$ll and improved the overall, both in power/capacity AND efficiency together... YOU HAD BETTER PATENT THE HOLY F#CK OUT OF YOUR DESIGN AND BUILD YOUR OWN MULTI-MILLION DOLLAR TURBO COMPANY REAL FAST! as that is every engine manufacturers dream!. Somehow you have beaten the millions and millions of dollars poured into research by all the engine makers, and your onto something really big!. - That or you need to approach Holset and tell them of your discovery and sell it to them for a few millions and retire. Achieving both at once = more efficient engine = lowered emissions == a whole cascade/host of improvements to any engine maker downstream.

(this is what has been rattling around in my own head on this any ways).