FAST startup surging

[BigBird R/T]

On a FAST WP.Can anyone shead some light on this startup log? It surges (high rpms - low rpms) and will smooth out after its warm. Weird runtime #'s and ATM correction. What is ATM correction?
Thanks.......

 

[norbs]

I opened the log file and its all corrupt with crazy numbers? Maybe reload it?

 

[BigBird R/T]

Thanks for checking my problem Norbs. I will do another log on start.
Which sensors should I include in the log to give us the most info for after start run?

I found from reading the old C-Com manual that the ATM Corr (%) is used in the Alpha-N mode and since I had it in the dash I logged, maybe it corupted the file?
Thanks for the help.

 

[norbs]

You need to log the following: You want the car to be so that its not too rich or too lean that it doesn't stall.


rpm
kpa
coolant temp
o2 correction
actual fuel ratio
cts correction
aft correction (cant log that on a gen 7 since they thought its not important)
iac position
ignition timing
ve

 

[callmeebryan]

Your log shows o2 correction at -92%?!? Your car cant be running THAT rich.

You shouldnt be running closed loop at idle either. 14.0 in closed loop at idle will make the car hunt alot... atleast thats my experience with my buick. I see that you have a 360ci v8...

Too much timing at idle IMO.... run no more than 30.

Your VE map is a mess! You need to go through and clean that up a bit. Check out the 3d view of the fuel map by pressing "G" with the VE table open.

Heres a setup file. Try this out....i changed a bunch of things.

I want you to log a cold start up and let it warm up.... log with the following parameters.

RPM, Map (kPa), IAC position, Coolant, Air Temp, TPS, Battery, Spark, Inj DC, O2 Corr %, BPW, MAP (psia), Actual A/F, Target A/F, Fuel #'s/hr, ESC Rtd, CTS correction, ATS correction, Aft Correction.

Post your results afterwards. Let me know how it goes.

 

[BigBird R/T]

Can't find IAC POSITION in the dash setup. All I have is IAC D,P,PD and TARGET.

 

[callmeebryan]

Can't find IAC POSITION in the dash setup. All I have is IAC D,P,PD and TARGET.

Target

 

[BigBird R/T]

Thanks Norbs, Thanks CMB.
I'll do another log tomorrow when the truck is cold and post the log. By the way it's a supercharged 360 Dakota truck that runs low 7's 1/8ths, low to mid 11's 1/4. It's a fun grocery getter.
Also CMB, with the ccom wp I can only log 14 sensors at a time. You requested 19 but I think I know which are the most important.
Thanks guys.

 

[callmeebryan]

Thanks Norbs, Thanks CMB.
I'll do another log tomorrow when the truck is cold and post the log. By the way it's a supercharged 360 Dakota truck that runs low 7's 1/8ths, low to mid 11's 1/4. It's a fun grocery getter.
Also CMB, with the ccom wp I can only log 14 sensors at a time. You requested 19 but I think I know which are the most important.
Thanks guys.

Alright then do the essentials for the purpose of finding out your problem.

RPM, Map (kPa), IAC position, Coolant Temp, Air Temp, TPS, Spark, Inj DC, O2 Corr %, Actual A/F, Target A/F, CTS correction, ATS correction, Aft Correction.

 

[MSDGN]

I'm curious about this also as my car hunts on a cold startup...only does it for about 20 seconds then idles fine...

 

[callmeebryan]

I'm curious about this also as my car hunts on a cold startup...only does it for about 20 seconds then idles fine...

Ive been experiencing it too.... im sure you have a B2B aswell. I havent heard of XFi users having this problem, it just seems to occur with the B2B guys. Not really sure why just yet as ive only had a few months time with the FAST, but i've already gotten pretty good at it.

I have been able to bring the hunt to a VERY MINIMAL 200rpm oscillation for the first 15-20 seconds or so, after that it idles at 850 +/- 25. The after start hunt only seems to happen when the car is up to normal operating temperatures. Cold starts are flawless. I have it set to idle at 1250rpm when its cold, then it slowly decreases to 850 by 140*F.

I have found that richening up the mixture in open loop idle helps tame the Normal temp after start hunt. My car idles at around 13.0-13.5 in open loop and its real smooth. I have also found that my car loves right around 30* timing at idle. Less than that, it makes my cam sound like its more aggressive than it really is.

MSD, do you mind doing 2 logs for me? I'd be glad to take a look at it for ya. Take a cold start log.... have it start before you turn the key and let the car warm up to normal temps. Log the same parameters as i stated above. For the second log, start the car after it is warmed up, again start the log before you crank it, and let this one go for about a minute.

Give me those two logs and your gct. :smile:

 

[BigBird R/T]

Here are the .gct and .log files from this evenings start up. Hope it can help. Its not that cold here (85) but in COLD weather it's worse. Thanks..........

 

[callmeebryan]

Here are the .gct and .log files from this evenings start up. Hope it can help. Its not that cold here (85) but in COLD weather it's worse. Thanks..........

Your IAC readings are way too high for a good idle. My IAC readings at idle dont exceed about 30. Yours are up in the 90's. Whats your IAC readings during a warmed up idle? If it is more than 30, then you need adjust that idle screw (open that butterfly a bit) in order to bring the IAC value down... As a general rule, i like to say that you want your engine to be able to run without the IAC 150-200rpm below your normal idle speed. That way, you are only using your IAC to make very small adjustments(if any at all) at idle. It shouldnt be making HUGE drastic adjustments. After you do this, make sure you go in to the IAC parameters and change the "MAX TPS for idle(%)" to +1 of the new TPS idle reading.

Something weird is going on... your A/F is going from 13.0 to almost 16.0.... and the 16.0's are happening with ve's in the high 50's. Its all over the place. :frown:

I've tinkered with a bunch of things and i want you to try this again. Same logging procedure, same parameters. MAKE 2 LOGS THIS TIME... log the car for 3 minutes from a dead cold (coolant temp) start. Let the car warm up completely... THEN i want you to shut the car off, start a new log that is now 30 seconds long, and start the car when its hot with it logging. Be sure to start the log a couple seconds before you start the car.

We'll fix your idle dont worry

 

[MSDGN]

No I don't have B2B...have XFI...the hunting only happens on cold start...on warm starts it idles fine...I've tried adjusting the Start IAC Pos vs Coolant Temp table but it didn't help...

 

[callmeebryan]

No I don't have B2B...have XFI...the hunting only happens on cold start...on warm starts it idles fine...I've tried adjusting the Start IAC Pos vs Coolant Temp table but it didn't help...

How does your AFR look on a cold start up?

 

[BigBird R/T]

CMB, I warmed the engine up this evening and checked the IAC. It was at 37 or so and adjusted the plates to achive the target rpm of 800-850. The IAC was then at 20-21. Opening the plates further only raised the rpms (1200 or so) and would not lower the IAC....? The idle TPS is still about the same (14-15) so left it set at 16. Damn, I feel like I'm learning something.
Anyway, the engine is hot now so will do the cold start logging tomorrow evening with the new gct file (if I get home early). I would take this to PM ing but guess it could be helpful to any new FAST tuners if it's alright with you. I'm going to swallow my pride and admit I'm a newbee even though I've had this system about 5 years now. Thanks.............

 

[Fuelie Nova]

I say leave it up and let us learn. I watch for this post daily.
Tg

 

[callmeebryan]

CMB, I warmed the engine up this evening and checked the IAC. It was at 37 or so and adjusted the plates to achive the target rpm of 800-850. The IAC was then at 20-21. Opening the plates further only raised the rpms (1200 or so) and would not lower the IAC....? The idle TPS is still about the same (14-15) so left it set at 16. Damn, I feel like I'm learning something.
Anyway, the engine is hot now so will do the cold start logging tomorrow evening with the new gct file (if I get home early). I would take this to PM ing but guess it could be helpful to any new FAST tuners if it's alright with you. I'm going to swallow my pride and admit I'm a newbee even though I've had this system about 5 years now. Thanks.............

The reason your IAC wouldnt go down below 20-21 is because your idling at 15% TPS.... in your throttle follower map (which designates IAC position according to TPS from 0 to ~30) you'll notice at 15% your IAC position is set for about 20.... that means it will never go below that number. Since you are idling at 15%, put the green line to "0" from 0-13% and then have it increase linearly to a max of 40@45%(the right side of the chart).

I do not mind helping people out at all. Im only 20 years old but i sure have come a long way in the past few years. Im just passing along knowledge to fellow buick enthusiasts . I too learn new things every day.

Looking foward to seeing the log tomorrow.

 

[Fuelie Nova]

Im just passing along knowledge to fellow buick enthusiasts . I too learn new things every day.

What about chevy lovers that lurk here to learn? :biggrin:
Tg

 

[BigBird R/T]

Looking foward to seeing the log tomorrow.

Here is the log and gct files I did this evening. If you need any further info just hollar. (hollar) Texas for "just ask"