First 6.7 Tune, looking for advice.

[bill1977]

16835Hi, new to the forum and new to the 6.7 truck is a 2008 crewcab 6.7 standard, twin disc 650hp clutch, 5 inch turbo back, intake, fuel plug.

looking for a performance/race tune. near the stock fuel limits. planning on lift pump soon.

I know the tune is a mess. try not to laugh any ideas on a direction to go would be great.

also im used to duramax where you can command certain boost. do the vane position tables decide boost?

thanks for all the help.

[2007 5.9]

Pretty agressive pulse and timing...do you have studs and EGR deleted? Stock Turbo?

[bill1977]

EGR is completely deleted, stock studs and turbo, truck is not a daily driver and never is loaded.

its a little smokey but not bad. am I at the limits before studs and lift pump?

was hoping to get a little more out of it first.

[2007 5.9]

Smoke is mostly from timing, and your running the upper end of what I'd consider safe for stock bokts

[bill1977]

thanks for the replys. I guess I wont add anymore then, I'll just do my best to clean the tune up a little.

[30 RUM]

Giving it a quick look, have you logged your rail? With out a lift pump and stock CP3, I think you may getting close to max duration before rail starts to drop.

[bill1977]

I have not logged but I dont belive the rail is droping, I'll double check though. was thinking of lowering timing a bit to reduce smoke a little in higher throttle areas.

any ideas on fuel pressure? I notice maxes out at 180 but tables go to 185, is there any gain there? possibly a small amount more pressure and slightly less duration?

also ive raised maximum vane position is this a good idea? im used to duramax where I command more vane position for more boost

[computerjlt]

$5 says you're never hitting targeted rail pressure.

Every 6.7 i've done even with tame fuel and timing i've had to tweak the duty cycle tables for rail pressure

[2007 5.9]

$5 says you're never hitting targeted rail pressure.

Every 6.7 i've done even with tame fuel and timing i've had to tweak the duty cycle tables for rail pressure

Thats a interesting observation...wonder why that is. Cant say that in the prob 1,000 tunes Ive done, have I had to mess with DC tables to get desired rail when my pulse isint too aggressive.

[computerjlt]

Thats a interesting observation...wonder why that is. Cant say that in the prob 1,000 tunes Ive done, have I had to mess with DC tables to get desired rail when my pulse isint too aggressive.



hmmm this concerns me then...

I honestly haven't done many 6.7 cummins so far on my dyno. They were all mostly stock minus some induction mods and deletes. 2 were pushed into the 400whp range. I've yet to go over 2800us of fuel and 45% on the timing calculator under the highest load cells.

I don't have any logs or calibrations with me to look to give exact numbers and examples but base duty vs. actual was always off (which is understandable as dodge relies on their PIDs to keep it close). on all trucks the max duty cycle table would limit the DC of the high pressure solenoid before desired rail pressure of 180Mpa was reached.

i know I didnt have to add much to the base duty and then bump up the max duty a bit farther (I'm thinking 20% IIRC) for the PID loops to have enough room to keep desired vs. actual rail pressure within a few percent.

[2007 5.9]

You may put those tables back to stock, and log actual vs desired rail (not DC) and I bet you don't have much issue hitting target rail.

Simply making the assumption that based on visuals that rail is limited without logging, may be causing you unnecessary tune changes and issue.

[computerjlt]

thats where i first noticed the problem was in rail pressure... let me find some logs

actual vs. desired rail pressure wasn't hitting thats when i noticed duty cycle. made some small changes and now it hits.

it could be coinincidence that all the trucks have factor lift pumps and old filters. you're probably used to trucks with nice lift pumps and or new filters

[computerjlt]

here are screen shots from the last truck i did. 07.5 6.7 stock fuel system with intake turbo back and deletes.

the initial run was pretty short but it still didnt hit rail pressure. the next run was longer but almost instantly hit desired rail pressure and held pretty well. the only change i made was adding about 20% to the base duty table. I didnt touch the max duty like i thought i had.

17061


17062

[2007 5.9]

Well to be fair in the first screenshot you were commanding 180MPa and the in the second you were commanding 167MPa...that alone will provide a better chance of achieving target rail when your running a 2800uS pulse on a stock fuel system.

[computerjlt]

this is true. but even then it never hit it in the first log.

i'll do more testing the next time i have a 6.7 on the rollers and see what happens