E70 starting issues.

[Spamby]

I guess I have been sitting on this one for a while. The issue is tolerable but I am getting annoyed now.

Having some issues with cold start and warm start on my E70 tune. Also some other oddities, at least to me, since this tune.

Background:
2008 STi
Stage 2
ID 1000?s
DW 65c

Car was tuned by Cobb-Plano on their dyno via AP. Tuning was done when the temps were in 70-80 degree range.

Cold start / cold temps (below 40)

Takes a few start/die cycles. Cranking time is about 5-10 seconds each. Engine fires hits about 1k rpm and then dies immediately. Usually fires and stays running on the third try. Engine fast idles and all is good. However, releasing of the clutch (engaging it in neutral I.e. pedal out) may cause the engine to bog and the idle to wander for about 10-20 seconds.

Cold start / warm temps (above 50ish) Cranking time is about 5 seconds or less. Engine fires and idles normally.

Warm start / warm or cold temps. (within an hour or two after driving) This one is tricky.
Sometimes she fires immediately, less than 5 seconds cranking. Other times she takes, what seems to be, a longer time of cranking to fire, maybe to 10 seconds or it might not fire and then you have to restart and she?ll catch. Usually after the engine catches there may be a slight after burn, or a pop from the exhaust. Usually she goes into a faster than normal idle, 1000-1300 rpm, until you give input to the throttle. Engine temps show to be near operating or halfway there.

I have seen temps here from 14* to 105* degrees since the addition of ethanol. Basically, starting is inconsistent when compared to gasoline in all temp ranges and when the engine is at various temperatures.
However, driving and performance has remained consistent and very good.

I have read some issues regarding starting issues and ethanol and the fixes for them, ranging from block heaters to altering start fueling and warm up enrichments. However, they all seem to be related to cold starting and not warm starting. Seeing as I have two temperature type issues, what say you tuning gurus?

 

[HolyCrapItsFast]

The two issues may be unrelated to each other... or not :lol:

Ethanol has a lower evaporation rate than gasoline but you should never see start issues with E on a warm engine. The fact that it cold starts on warm days says to me that it is not the typical cold start issue normally seen during cold starts but it is something else like vapor lock. I have seen this a number of times on hot starts with both E and Gasoline.

As far as the cold start issues on cold days... welcome to the club. Essentially since the fuel can not properly vaporize in temps below 60* you have to help it along by adding more fuel during crank AND to get that fuel to atomize. Few tuners actually know how to do this correctly and when people use E they often overlook what is needed to get it to start correctly in cold weather.

When planning your E conversion you need to not only plan your pump and injectors correctly but you also need to plan your tune to bump up the pressure. The strategy is to select the smallest injector for the power goals you expect to achieve. In most stage two applications 850cc will do just fine. Then increase the base pressure. This will do two things... A) it will increase the static flow of the injector and you can easily achieve 1000CC from an 850CC injector. And B) it will allow the fuel to atomize properly at lower IPW's and during crank. The other reason I suggest selecting the smallest possible injector is because you want your resulting Injector Pulse Width to be as large as possible with out going past 95% IDC on the coldest day. This will help drastically with idle, and low end drivability.

If I were you I would take it back to cobb and see if they will do a re-tune and maybe you can discuss some of this with them. In our E85 write up I discuss the tables to tune for cold start issues such as this. http://www.igotasti.com/vBforum/showthread.php?205-All-about-E85. Another thing you can do is get a block warmer and be done.

 

[Td_d]

There are also newly uncovered warm start up and post start related tables that one needs to also tweak when upgrading injectors, since they add too much fuel being tuned for the stockers.

 

[HolyCrapItsFast]

There are also newly uncovered warm start up and post start related tables that one needs to also tweak when upgrading injectors, since they add too much fuel being tuned for the stockers.

You mean there is more? ) I was perfectly happy with the ones the had. Lol.

 

[Spamby]

Yes. Aware of E's cold start issues. Just kinda pisses me of that on occasion I have to crank it slot when it's warm.
I had thought about the vapor lock issue. Seeing as how I have random difficulties starting when the motor is warm. Vapor lock would have to be solved by me as this wouldn't be tune related.
The cold issue? I had planned for that and actually I see that I am having a much easier time than some.
Cobb did it and they should correct it if they are at fault. Only problem is they are 4 hours away. I'll give them a yell next week and pick their brains. Hopefully we can do something via email rather than driving there again.
I wish I would have learnt myself an edumacation in tuning. Lol

 

[Td_d]

You mean there is more? ) I was perfectly happy with the ones the had. Lol.

Chuckle.. Yeah. There are tables that deal with cranking on warm restart (where things can get mad rich - these tables are the reasons) tables that deal with how enrichment decays over time post cranking, and also initial airflow and load tables (I.e reference assumptions before the sensors start providing legitimate data).

The rabbit hole goes deep, Kimosabi :lol:

 

[Spamby]

Chuckle.. Yeah. There are tables that deal with cranking on warm restart (where things can get mad rich - these tables are the reasons) tables that deal with how enrichment decays over time post cranking, and also initial airflow and load tables (I.e reference assumptions before the sensors start providing legitimate data).

The rabbit hole goes deep, Kimosabi :lol:

Geebus. and I thought dropping acid and watching Alice in Wonderland was frightening!

Is there anything I can do? Say if Cobb can't resolve this or if I am just feeling frisky and want to take this on as a learning experience?
I assume the tune is locked due to it being via AP?

 

[Td_d]

Not sure about the tune being locked, but likely I would think.

The COBB speed density implementation (and I think now in general) also have these tables. The easiest way to disable this logic is to set the ECT thresholds much higher than possible.