REP airflow related?

[O1Z06]

Guys,

I really need some help with this one. The pcm is going into reduced engine power mode during fast changes in airflow. For example, if your in the burn out box and modulating the throttle by bliping, then it will throw the code. It only happens when it is a large or sudden change like when the tires break loose. 5th gear pulls above 512 grams/s seem ok, 4th gear pull when the tires are spinning and above 511 grams/s it will do it.

So my question is this airflow tune related (scale VE and IPW) or the physical throttle body (thinking blade is stuck).

14014

[O1Z06]

I scaled inj PW at 0kPa gauge and VE starting at 100 kPa absolute on up. Took 20% out and so far so good. I also noted that grams/s is still maxed so it must have been because of grams/cyl causing the PCM to safe fail.

[joecar]

So is g/cyl that exceeds some table causing REP, or is g/cyl rate of change excessive causing it...?

I don't see any g/cyl/s tables, altho this is just a factor of g/s.

[O1Z06]

Initially I thought it was the rate of change, but just scaling would not reduce the rate of change. All tables + C6101 and C6202 are maxed out. The scans showed 512 grams/s which is why I was thinking that was the problem. Dynair is still over 512 grams/s but now clyair is 20% less.

I went through all tables but couldn't find anything. Is it just a hard coded limit?

[Gregs]

are you getting code p1514?

[O1Z06]

That is a good question. Reason being because I never checked while the engine was in REP. After I shut it down on the side of the road or wherever, while waiting a few minutes for the pcm to reset, I checked and didn't have a code. If it happens again I will check before shutting off.

Is p1514 an airflow or etc code?

[O1Z06]

I found this in the archive.


Check dynamic airflow.

If you are over 2.32 g/cyl you will get a 1514 no matter what you do to the 1514 table.

Drop your IFR and VE table by an equivelent amount (say 10 or 20%) and that will drop the dynamic airflow. If you still bang the limiter, go another 10%.

I have had the same problem on a 427 with a ProCharger F1R. I was getting a 1514 at 4000 RPM. It has 750cc RC injectors so my original IFR table started at 83 lbs/hr."

So then I checked your g/cyl on your log and it hit 2.45 when you had the issue (see attached pic).

I think it has to do with reaching the internal limits of what the pcm is programed to calculate, also when I loaded your file it said some of values were out of range on the boost ve, either way this would be worth a start.

[joecar]

O1Z06, good find, do you have a link to where that came from....?

[O1Z06]

Thank you. Sure, here is the link.

P1514 and no reason (http://forum.efilive.com/showthread.php?5024-p1514-and-no-reason&highlight=p1514)

Since this is a problem with GM's code and not a configurable table, I heard this just effects a handful of operating systems. Since I am running 02020005, should I go back and try my old 02040003?

If you scale the values by a percentage and it is not enough, be careful because just scaling back again from the previous result is not an additive amount. You have to go back and scale from the original amount.

For example if you scale 100 by 20% you get 80. But if you scale 100 by 10% you get 90 and scaling again by 10% you get 81. So effectively that is 19%. Throw some VE tweaks in between the rescale and then it gets really confusing knowing the total amount reduced. It's best to make a spreadsheet and calc your estimate cylair. If I would have known 2.32g/cyl was the limit, I would have tuned that into my base tune. 2.32g/cyl is around 650hp so you can use that as a general guide too.

I just heard a Fosters commercial on TV, now I'm thirsty :beer:

[joecar]

lol, yes, drink more beer (it is much healthier for you than soda) :cheers: