Lots of threads lately about ..................
If I cam it .................................................. how will it idle
If I go to a different maf ............................... how will it idle
If I go to different inj's ................................. how will it idle
If I go too low with lsa ................................. how will it idle
Restrictor iac plates
TB blades with holes
We could go on & on!
Everybody is looking for that ever elusive ............ Stable Idle
I thought it might be helpful to start a thread with a focus on idle issues and why the pcm is not happy with the things it sees from its various sensors.
When at idle, lots of things are going on from the pcm's perspective to try and give us a stable idle. We won't go into a lot of detail here as it has all been said before. Here are just a few of those main things that come to mind.
1) Fuel mixture is monitored with input from O2's and the pcm will change it + or - as needed.
2) Spark is monitored and changed by the pcm as needed.
3) Air flow is monitored with input from iac and as it changes, idle speed is changed + or - by the pcm as needed. The pcm has various air flow values at various rpm points at and around a very low 640 rpm.
I thought I would point out stuff like this just to show how all these things and more come into play when at idle
or
at a close to closed throttle cruise around town.
Now we go and install all those hot rod parts on our car.
Look at #3! With my car, it won't even think about an idle of 640 rpm. That means all the values in the pcm are now inaccurate due to my increased rpm idle.
Look at #3! With an increased idle, the spark is now gonna be different.
Look at #1! We gotta have upgraded inj's/maf. We now have a maf transfer that is all hosed which in turn hoses up the load which in turn hoses up our fuel mixture.
Look at #1! We put LT's on our car and the O2's get moved a good bit farther away from the heat. Think that could cause us a prob from time to time?
It is true ........................
The pcm does have the adaptive strategy which can learn about those upgrades and give us some help
but
it does have limits and can only adjust within a range.
If we need more adjustment than it can deal with, mechanical adjustment on our part may not be enough to help.
We got all this kinda stuff going on and since each combo is a bit different, we should be able to see how it is not cut & dry, black & white or the same for each combo as far as how the car is gonna behave (drivability)
Heck ... Even if we built two identical combos ............................
We very well could get different results due to the complexity of everything. No pcm, iac, pair of O2's, set of inj's, tb, maf, intake, cam, etc can be identical.
Yet our first tendency is to look at each others combo and expect the same drivability results.
While our focus here is on idle, please remember this ...........
If we have an unstable idle
We also have an unstable cruise (buck, surge, etc)
Here is another thing to consider that can be so misleading.
Cobra and GT Stangs have a very different pcm. Each one deals with mods from a totally different perspective. I myself did not pay much attention to this issue until recently.
This should be at least considered, when trying to duplicate advice or tuning efforts from one type car to the other.
The things above and more are what a Pro Tuner deals with when we take our car to him. All those values in the pcm are still set for a STOCK STANG when he first gets the car. He simply adjusts those stock values to match the changes caused by our upgraded mods. Thats why your drivability can be fixed when you take your car to the Pro Tuner.
One more thing to consider and I'm done here.
We have seen those who say .................................
"I got my drivability issues fixed by a mail order chip!"
How this happens is kinda like this ...................................
Whatever values need to be changed, if he can get half way close, the adaptive may be able to handle the rest and drivability can be improved.
Bottom Line here is .............
There is everything to be gained from trying mechanical tuning adjustments and nothing to be lost from trying this method to tune.
HOWEVER
If those mechanical adjustments don't work ..............
The things above are just too far outta whack and need to be corrected.
btw ....... Joe I was 50 50 on which forum to post this thread. Please move it elsewhere if you think it will be of more help to the members.
Grady
If I cam it .................................................. how will it idle
If I go to a different maf ............................... how will it idle
If I go to different inj's ................................. how will it idle
If I go too low with lsa ................................. how will it idle
Restrictor iac plates
TB blades with holes
We could go on & on!
Everybody is looking for that ever elusive ............ Stable Idle
I thought it might be helpful to start a thread with a focus on idle issues and why the pcm is not happy with the things it sees from its various sensors.
When at idle, lots of things are going on from the pcm's perspective to try and give us a stable idle. We won't go into a lot of detail here as it has all been said before. Here are just a few of those main things that come to mind.
1) Fuel mixture is monitored with input from O2's and the pcm will change it + or - as needed.
2) Spark is monitored and changed by the pcm as needed.
3) Air flow is monitored with input from iac and as it changes, idle speed is changed + or - by the pcm as needed. The pcm has various air flow values at various rpm points at and around a very low 640 rpm.
I thought I would point out stuff like this just to show how all these things and more come into play when at idle
or
at a close to closed throttle cruise around town.
Now we go and install all those hot rod parts on our car.
Look at #3! With my car, it won't even think about an idle of 640 rpm. That means all the values in the pcm are now inaccurate due to my increased rpm idle.
Look at #3! With an increased idle, the spark is now gonna be different.
Look at #1! We gotta have upgraded inj's/maf. We now have a maf transfer that is all hosed which in turn hoses up the load which in turn hoses up our fuel mixture.
Look at #1! We put LT's on our car and the O2's get moved a good bit farther away from the heat. Think that could cause us a prob from time to time?
It is true ........................
The pcm does have the adaptive strategy which can learn about those upgrades and give us some help
but
it does have limits and can only adjust within a range.
If we need more adjustment than it can deal with, mechanical adjustment on our part may not be enough to help.
We got all this kinda stuff going on and since each combo is a bit different, we should be able to see how it is not cut & dry, black & white or the same for each combo as far as how the car is gonna behave (drivability)
Heck ... Even if we built two identical combos ............................
We very well could get different results due to the complexity of everything. No pcm, iac, pair of O2's, set of inj's, tb, maf, intake, cam, etc can be identical.
Yet our first tendency is to look at each others combo and expect the same drivability results.
While our focus here is on idle, please remember this ...........
If we have an unstable idle
We also have an unstable cruise (buck, surge, etc)
Here is another thing to consider that can be so misleading.
Cobra and GT Stangs have a very different pcm. Each one deals with mods from a totally different perspective. I myself did not pay much attention to this issue until recently.
This should be at least considered, when trying to duplicate advice or tuning efforts from one type car to the other.
The things above and more are what a Pro Tuner deals with when we take our car to him. All those values in the pcm are still set for a STOCK STANG when he first gets the car. He simply adjusts those stock values to match the changes caused by our upgraded mods. Thats why your drivability can be fixed when you take your car to the Pro Tuner.
One more thing to consider and I'm done here.
We have seen those who say .................................
"I got my drivability issues fixed by a mail order chip!"
How this happens is kinda like this ...................................
Whatever values need to be changed, if he can get half way close, the adaptive may be able to handle the rest and drivability can be improved.
Bottom Line here is .............
There is everything to be gained from trying mechanical tuning adjustments and nothing to be lost from trying this method to tune.
HOWEVER
If those mechanical adjustments don't work ..............
The things above are just too far outta whack and need to be corrected.
btw ....... Joe I was 50 50 on which forum to post this thread. Please move it elsewhere if you think it will be of more help to the members.
Grady
