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      04-13-2012, 02:50 PM   #1
Kalud's Avatar

Drives: e92 335i
Join Date: Jun 2010
Location: Canada

iTrader: (0)

Exclamation n55 custom tuning thread

Hello everyone interested in fine-tuning their tune.

I sincerely hope we can keep tune wars out of this thread. The data here is valid for any tune.

First of all, I am NOT a professional tuner, I am an enthusiast. Still quite picky on details and I've made extensive logging of my car in the last year. I've made many tests and tweaks and have now exactly what I want. I also helped some forum members here and there.

You should still trust more your tune vendor than me, and maybe shoot them a log from time to time for comments.

eyim1988 sent me a PM couple days ago. He feel he doesn't run enough boost, boosting ~11psi on his boost gauge. He asked me if he should be able to run 15.5-16psi safely.

Car specs: catless downpipe/intake/Procede

I asked for a log of a 3rd gear pull from low rpm till as high as possible with those parameters:

CAN DBW Throttle
CAN Actual AFR Bank 1
Boost Control Set Point
CAN Actual Ign Adv
CAN DME Boost Actual
Boost Control DC
Inlet Air Temp
Now, my analysis. Again, I don't pretend to know everything, I am analyzing with my experience and I am not a professional.

In short, too little octane (looks like 91) to run stock timing advance with that boost level (about 12psi).

Boost reach target correctly (target is 12 currently, we can have a look to settings later but he needs to address the timing curve first). No sign of boost leak or any other boost related problem.

IAT (inlet air temperature) is quite high, its 100% normal and all stock 335i suffer that problem in warm climate (well, by warm I mean anything above 32F) because compressing air (turbo) warms it, the more you compress and the less efficient the compressor is, the more it heats up. To remove heat there is an intercooler that is designed for stock boost level so it heatsock rapidly. Anything above 90 / 100 F is high (I don't know the exact DME's threshold but its around that) and reduce performances (the DME reduce its boost and advance target). An upgraded intercooler would help a lot. Best solution is methanol+water injection but its not necessary a route everyone want to use. Meth will reduce IAT often bellow ambient (bellow 75F in his case probably) and also increase the effective octane of the fuel like running race gas all the time.

Ignition Advance curve: The DME is right now protecting (quite well don't worry) his engine by listening to knock sensors and it retards timing ignition, red circles on the log. Given he probably don't have access to 93 or 94 octane and he's not using meth right now he should increase your ignition correction % factor to apply a global constant ignition retard over the stock advance curve to avoid constantly running on the edge of knock.

At this point I don't suggest he raises boost as it will make think worse (higher IAT and more pressure so more prone to knock).

He can try race gas, he'll get a super nice advance curve (no knock event), more boost and a lot more power. But in a daily basis I don't think its possible to run race gas unless he don't mind the price. I suggest we start tweaking the tuning for what is available normally (using map1) and then tweak map2 for race gas use (race, quarter mile, etc...)

I think many would benefits from those explanations that's why I started a new thread with his example, many could chime in, give ideas and learn in the process, including myself.

Now, if that would have been a JB4 user he could have PMed / emailed Terry or Mike and get personal assistance, probably real quick too. Vishnu tuning support is harder to get rapidly unless you have an issue and call directly (Robert will help you rapidly) but Shiv is busy as hell for some time now with the single turbo.

I for sure would appreciate more forum presence from them but its not the case. In the end, I appreciate the fact that we can log and tune the parameters, with the help of others we can actually do a terrific job that would cost a lot of $$ in professional tuning sessions on a dyno, and not everyone want simple plug and play generic power without additional control. I am an enthusiast and that love that whole tuning thing, logging, tweaking is part of the fun.

Also I wish I could test the Cobb AP on my car for comparison but its not available so right now the Procede and JB4 are the only available tune that we can actually tweak and "tune" to our specific car / conditions our self.

For comparison, here is a log I have of a timing curve on 94 octane, no meth, no intercooler, no intake, just Procede+catless downpipe and 15psi:

And this is 16.5psi + meth only:


3rd gear pull:

partial 4th gear: