Too much timing advance..?

[Tyler_Baker]

Just finished breaking in my motor, and began to tune my 50trim. I have a EPROM with 750cc/2GMAS compensation, SAFCII, Pocketlogger, check my profile for complete mod list. My peak timing at WOT is at 29 degrees @ 6000 rpm, I have tired retarding the CAS sensor to lower the timing but have been unsucessful. I am stumped why my timing is being advanced so much, if anyone has any possible solutions to this problem please let me know.

Edit: I was told to hack the 2GMAS when running this ECU: side, bottom honeycomb removed, and screw backed out. I know airflow effects timing, could this be a possible reason why my timing is advancing?

 

[Tyler_Baker]

Here is the log 2nd + 3rd Gear Pull
RPM Knock Timing Temp
4938.0 0.0 26.0 187.0
5063.0 0.0 26.0 187.0
5188.0 0.0 27.0 187.0
5375.0 0.0 27.0 187.0
5594.0 0.0 28.0 187.0
5750.0 0.0 29.0 187.0
5938.0 0.0 30.0 187.0
6094.0 0.0 29.0 187.0
6219.0 0.0 29.0 187.0
6375.0 0.0 28.0 187.0
6500.0 0.0 28.0 187.0
6625.0 0.0 27.0 187.0
6719.0 0.0 26.0 187.0
6813.0 0.0 26.0 187.0
6906.0 0.0 25.0 187.0
7063.0 0.0 26.0 187.0
7125.0 0.0 26.0 187.0
7219.0 0.0 26.0 187.0
7250.0 0.0 25.0 187.0
7375.0 0.0 27.0 187.0
7375.0 0.0 27.0 187.0
7531.0 0.0 28.0 187.0
7688.0 0.0 45.0 187.0
7219.0 0.0 36.0 187.0
6750.0 0.0 35.0 187.0
6688.0 0.0 31.0 187.0
4719.0 0.0 29.0 187.0
5000.0 0.0 28.0 187.0
5125.0 0.0 27.0 187.0
5188.0 0.0 27.0 187.0
5219.0 0.0 26.0 187.0
5281.0 0.0 27.0 187.0
5281.0 0.0 27.0 187.0
5375.0 0.0 27.0 187.0
5438.0 0.0 28.0 187.0
5500.0 1.0 28.0 187.0

 

[98spydert]

Why don't you want that much timing advance? There's no knock sum

 

[Tyler_Baker]

Why don't you want that much timing advance? There's no knock sum

I hear ya man, that was exactly what I thought too. Except my car is really slow with that amount of timing. I read this thread which makes sense...

http://www.dsmtalk.com/forums/showthread.php?s=&threadid=115192&highlight=timing+optimum+fuel

This section caught my eye, and I feel relates to my problem

"Show me a datalog graph coupled with a dyno chart that has timing over 30* on a 4G63 engine at WOT. Then show me the same car at 21*.

We've seen hundreds of references of the fastest DSM's in the past and what timing they were running.

I'm simpy refering to what timing range has proven to be the best and that apparently gives us the Maximum Combustion Pressure on the piston top at the right time on the power stroke. This maximizes power. Wonder why the huge power is made on pump gas with VERY low timing advance? It is this concept, instead of maximizing the combustion process for emissions purposes. Now take a more stable race fuel and add a few degrees on top of what you run for pump gas.

I can personally say that over 30 degrees is bad news for your dsm at WOT. I've seen it, fought it and dealt with it. You can feel the loss in power in your ass, it's not rocket science, pull out enough air signal and see for yourself if you don't believe me."

 

[98spydert]

I figured that would be true, I've just never read it before.
That's wierd that you are getting that much timing advance considering you're not hacking up the MAF signal using a AFC for injector compensation. I would have thought you'd have the opposite problem flowing that much air and letting the ECU see it. Does you're TPS hit 100% or close to it?

 

[Talonman]

He is using an safc2 and big 750 cc injectors with a 50 trim. The amount of airflow he's reporting is low (considering he's only running a 50 trim and using 750cc inj's) and the ecu is looking at mid range fuel trim maps and uses the appropriate timing for the airflow reported. Id get a set of 660s instead and I bet you'll run normal timing advance. What are your current safc settings for the log above?

 

[98spydert]

He is using an safc2 and big 750 cc injectors with a 50 trim. The amount of airflow he's reporting is low (considering he's only running a 50 trim and using 750cc inj's) and the ecu is looking at mid range fuel trim maps and uses the appropriate timing for the airflow reported. Id get a set of 660s instead and I bet you'll run normal timing advance. What are your current safc settings for the log above?

He's not compensating with the AFC, just tuning with it. read:

I have a EPROM with 750cc/2GMAS compensation

 

[kpt4321]

Moving the CAS will not change the timing that you see on the datalogger. It will, however, change the overall timing. Datalogger timing assumes 5 degrees of advance base, unless you have a pocketlogger and have set it elsewhere.

First of all, we need some more details about your ECU. Where did it come from? Who programmed it? What does it supposedly have as options?

What are your settings on the SAFC?

What is the ECU showing for airflow Hz? What about injector pulsewidth/IDC? Have you gotten a wideband on the car yet? What do the fuel trims say?

 

[Tyler_Baker]

Figured out the problem, it was right under my nose. When I put the motor in I forgot to set the base FP, it was running with 43psi at idle. Because the FP was so high I had to lean the AFC out, thus taking airflow signal away, and then the ECU would advance timing. So I set the base timing to 5 degrees, and idle at 850, and FP to 38 psi. Now I don't have to lean the AFC on the high map nearly as much, so my ECU sees more air and doesn't advance timing. The car rips to redline, and the boost feels so smooth. Here is a 2nd gear pull after I adjusted the car.

RPM Knock Timing
4344.0 0.0 29.0
4438.0 0.0 28.0
4563.0 1.0 28.0
4656.0 1.0 27.0
4813.0 1.0 27.0
4938.0 0.0 26.0
5031.0 0.0 25.0
5188.0 0.0 25.0
5313.0 0.0 24.0
5469.0 1.0 24.0
5688.0 0.0 24.0
5813.0 0.0 24.0
5969.0 0.0 24.0
6125.0 0.0 24.0
6250.0 0.0 23.0
6344.0 0.0 22.0
6500.0 0.0 22.0
6656.0 0.0 21.0
6719.0 0.0 20.0
6844.0 0.0 20.0

 

[Tyler_Baker]

Moving the CAS will not change the timing that you see on the datalogger. It will, however, change the overall timing. Datalogger timing assumes 5 degrees of advance base, unless you have a pocketlogger and have set it elsewhere.

First of all, we need some more details about your ECU. Where did it come from? Who programmed it? What does it supposedly have as options?

What are your settings on the SAFC?

What is the ECU showing for airflow Hz? What about injector pulsewidth/IDC? Have you gotten a wideband on the car yet? What do the fuel trims say?

Eprom with a keydiver chip. 750cc/2GMAS compensation, No Fuel Cut, 9000RPM rev limit, 850rpm idle, Enhanced closed loop operation, Octane value reset. This bin file was used on a 2GMAS/750cc/20G Car, and was programmed by my buddy Bryan.

AFC settings were @ 43psi: -22% on the high map which switches on around 21 psi of boost.

The AFC settings are @ 38 psi: -6% on the high map.

I'll log airflow on my safc next time I do a log. I have not had my car on a wideband, but plan to sometime in the near future. With the adjusted FP my trims are 102 % Low Mid 105% high 98%.

 

[diambo4life]

Figured out the problem, it was right under my nose. When I put the motor in I forgot to set the base FP, it was running with 43psi at idle. Because the FP was so high I had to lean the AFC out, thus taking airflow signal away, and then the ECU would advance timing. So I set the base timing to 5 degrees, and idle at 850, and FP to 38 psi. Now I don't have to lean the AFC on the high map nearly as much, so my ECU sees more air and doesn't advance timing. The car rips to redline, and the boost feels so smooth. Here is a 2nd gear pull after I adjusted the car.

RPM Knock Timing
4344.0 0.0 29.0
4438.0 0.0 28.0
4563.0 1.0 28.0
4656.0 1.0 27.0
4813.0 1.0 27.0
4938.0 0.0 26.0
5031.0 0.0 25.0
5188.0 0.0 25.0
5313.0 0.0 24.0
5469.0 1.0 24.0
5688.0 0.0 24.0
5813.0 0.0 24.0
5969.0 0.0 24.0
6125.0 0.0 24.0
6250.0 0.0 23.0
6344.0 0.0 22.0
6500.0 0.0 22.0
6656.0 0.0 21.0
6719.0 0.0 20.0
6844.0 0.0 20.0

Bingo. I was gonna say the low airflow # the ECU was seeing was the reason your advanced timing was too high. You could have easily blown your head gasket or worse if you had kept on running the car like that.

 

[kpt4321]

AFC settings were @ 43psi: -22% on the high map which switches on around 21 psi of boost.

The AFC settings are @ 38 psi: -6% on the high map.

Then you are running WAY richer than you were before. That change in fuel pressure equates to a change in fuel flow of about 6% (less), yet you richened the mixture up ~16%. That means you're now running way richer than you were.