BIG CAM TUNING ON LT1. Let's talk idle tuning

[GHuggins]

I had to drop the Virtual Torque below where I would normally have set it, then ramped up the MAF. Then I did a cold start idle for 3 minutes, drove the car and it seemed to be better. Then let the car sit, did another mostly cold start and short drive. By the third cold start the car passed the throttle learn as the code(which doesn't set a CEL) was no longer listed when I pulled the codes. The car idled with positive timing. I flashed the Virtual Torque back but only pulled the MAF down just a little bit and the car has been fine since. This particular car has the LTFT enabled and they range from -8%-13% or so depending on weather. It isn't where I would normally leave the MAF, but its working for this car.

So the same thing I do minus the MAF adjustment.

Other things for what they're worth - I've found the airmass and map side of the torque models need to match as closely as possible - at least for a very good controlled idle and drivability. I find shifting the models off of current airmass and map readings works really good to keep the model around stock then tweaking it from there for startup and control. If you're dealing with an auto and idling at negative torque you can wind up with clutch slippage going off idle, especially for reverse so it's key to adjust idle torque to where it's slightly above or around 0 if that low of a torque is necessary. Density table dial in is a must to keep torque and fueling balanced or rather the same at all times. I've had some interesting looking density tables, but they fixed a lot of problems - even with stock injectors being involved. Still don't have it to 100%, but I have the best resulting method pretty much figured out as I've got logs where the averaged fuel correction for PE or regular fuel trims don't change more than 1% from 0 error no matter the outside or engine temp - pretty happy with that...

So use the really negative torque model and a skewed maf setting to get timing back then readjust from there.

[TriPinTaZ]

So the same thing I do minus the MAF adjustment.

Other things for what they're worth - I've found the airmass and map side of the torque models need to match as closely as possible - at least for a very good controlled idle and drivability. I find shifting the models off of current airmass and map readings works really good to keep the model around stock then tweaking it from there for startup and control. If you're dealing with an auto and idling at negative torque you can wind up with clutch slippage going off idle, especially for reverse so it's key to adjust idle torque to where it's slightly above or around 0 if that low of a torque is necessary. Density table dial in is a must to keep torque and fueling balanced or rather the same at all times. I've had some interesting looking density tables, but they fixed a lot of problems - even with stock injectors being involved. Still don't have it to 100%, but I have the best resulting method pretty much figured out as I've got logs where the averaged fuel correction for PE or regular fuel trims don't change more than 1% from 0 error no matter the outside or engine temp - pretty happy with that...

So use the really negative torque model and a skewed maf setting to get timing back then readjust from there.

Yup, I always apply my Virtual Torque adjustments to the MAP tables as well. When forcing the idle learn, I just do a standard number like minus 100 in the first 2-3 columns and then interpolate to the right 1-2 columns. This usually shifts things enough for the learn to complete.

[GHuggins]

Force the learn/reset then tune. I like it. Will try on the next one

Problem is - this will work for the first, but then tweaks always seem to require more driving to know for sure it will stay there. Be nice if there was a setting we could change for this?

[TriPinTaZ]

Force the learn/reset then tune. I like it. Will try on the next one

Problem is - this will work for the first, but then tweaks always seem to require more driving to know for sure it will stay there. Be nice if there was a setting we could change for this?

I agree, there are definitely tables we don't have access to that could help too. And if the car ever loses power, IE battery disconnect, you have to flash the throttle learn file again to make it learn and then flash it back to your normal file.


I know we can search and find tables in HPTuners with some legwork, but I'm not motivated to find it. Well more like I don't have the time to.

[JASON11WS6]

Some good reading here. I'm gonna need to read it a couple of times to let it all soak in. This last tune seemed to jump around a bit more. Do you think from here we raise the maf around 10% and see if that brings the torque numbers back up?

Also, to be clear on what I'm considering a big cam. The cam specs are 240/252 on a 112lsa It chops even through the negative timing, so all we need is positive timing and it'll sound just fine.

[GHuggins]

I say lets try it. This one has a torque model that should idle somewhere around -40ish. Your maf was already adding 5 in that last log, so I added 15% to it. Since you have a manual, if you like it - you can continue to run this torque model or put the previous torque models idle regions back in - either/or...