Base Timing

[ahm700]

I have a question on base timing. I was looking around on the net and found this responce on a forum to base timing. Has anyone else tried this or heard of it? I am getting ready to set my timing so wondering if i should stay with the 4 6 or go to 6 6.

found that if you key both cams at 6 degrees that it runs better, instead of setting it to 4, and 6. With injection timing set at 4 degrees,

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[Rawze]

You have been reading a bunch of nonsense and listening to morons on the injection thing. Setting BTDC timing on an isx that high (17+ or worse,.. 23+) will cause detonation and you will be looking at cracked pistons in no time. Sounds like it is coming directly from the mouth of some redneck pickup truck tuner who knows little to nothing about a 15-litre modern diesel engine. 17+ and/or 19+ is more like the info for a small old-school yanmar engine or some other tiny thing that does injection on the intake. Those numbers are definitely for a very different, smaller engine.

Next, setting the static timing from 4 to 6 on the injector cam is something else all together than that. Personally, I would not do so. It is never a good thing to try to "fool the ECM" in attempts to make things run differently. You end up with unpredictable cylinder pressures and the ECM will see it and try its damnedest to correct the mistake on a constant basis thinking the injectors are running hot. The end result will be the ECM correcting the timing to compensate for the error. It is not going to just sit back like a dumb shi#t and ignore the fact that it detects a firing angle incorrectly and that exhaust pressures, etc. are out of whack from the cam out of adjustment. It is not such a simple device at all and it uses multiple sensors in combination to detect such things. the actual final injection timing might be somewhere very different than the 2 degrees you have shifted the cam by.

[ahm700]

Ok thanks that's why i asked. I am still learning myself. To bad that 90% of things you read or see is just crap. I know some of the cummins were set at 6 6 so thought there might be something to it.

[Rawze]

(09-16-2016 )ahm700 Wrote:  Ok thanks that's why i asked. I am still learning myself. To bad that 90% of things you read or see is just crap. I know some of the cummins were set at 6 6 so thought there might be something to it.

YES, many of the CM870's are set 6-6 and some are 6-7 and even 4-4 and 6-4. They were still trying to get emissions standards right with that engine, and it changed based on serial number sequence. BUT they also had programs set for those offsets for that serial number range to go with it. -- Another reason you can't just take an ISX program and put it into another engine blindly.

I have nothing against someone trying to get a bit more efficiency out of their engine, experimenting, etc. but the most difficult way is to go down the road towards "fooling the ECM". it will fight everything you do tooth and nail,.. The easiest way is to actually simply tell it you want something different instead. It takes all the guess work and instability out of the equation.

[Marajin]

(deleted engine soi values)..
8+ BTDC under any kinda medium to heavy load conditions is really inching into the danger zone for an ISX 870/871 and you are pushing your limits at that number. 17+ is way out of proportion on them. Even at idle, as you move the final BTDC above 8 or 9, they start to real sound sloppy and valve seat wear rate goes way up. Even 10-11 at only highest rpm ranges is pushing at low torque only. under heavy torque,.. it is much less forgiving where 7+ is pushing things.

This info goes far beyond simple opinion. Seen far 2 many blown engines, heads, crack pistons over the years and what the program was set at.

[Unilevers]

6/6 on a 4/6 engine works - but is fooling it. i DO NOT recommend it because you literally are guessing at timing, and the numbers 4 and 6 MEAN NOTHING for actually injection timing they are just the angle of the wedge vs some reference line. Going to 6 from 4 does not advance the timing 2 degrees, it is more than that. Also if you wedge a 4/6 engine at 6/6 and are sloppy with the setting you are riding the edge of what the ECM sees as acceptable timing. It will throw a cam/crank sensor out of whack code and derate you to almost nothing because it sees too far a spread between the cam and crank.

it also screws up when someone proper goes to tune that engine. Tweaking SOI and fueling for what its supposed to be and then actually finding out later that it was mechanically advanced can be troublesome and have catastrophic failures if not caught early.

simply put - wedge the dam thing what its supposed to be. If you want to play with timing tell the ECM to do it, not fool it!

[Rawze]

(09-19-2016 )Unilevers Wrote:  6/6 on a 4/6 engine works - but is fooling it
...
simply put - wedge the dam thing what its supposed to be. If you want to play with timing tell the ECM to do it, not fool it!

Very well put.