09-07-2016, 08:08 AM
Join Date: May 2005
Location: Chantilly, VA
Total Cats: 1,469
Running the ideal gas law in a very non-ideal environment is a great way to have a multitude of tuning problems, like: cant start when its hot, or horrible idle when it's hot, or it's too rich when it's cold, on top of having a completely worthless ve fuel table.
******* listen to me when i say: zero out the MAT corrections table completely by setting it all to 100%.
Tune your fuel map without any temp corrections.
Your EGO should have enough authority to keep AFRs in check for little swings in temps. If you notice on very hot days, the car is fatter or EGO is pulling fuel then tune the MAT Corrections Table to keep EGO from having to work to keep the AFRs in check. Similarly, if you're rich on cold nights, or when winter hits, you can tune the lower end of the scale to add in some fuel
I just tuned an N/A car this weekend. Average intake temps are 160°F, on the 90°F day we tuned, they would hit 190°F. If I used the "ideal" curve, MS would be removing 20% of fuel from the fuel map. That's insane.
I would then have to over compensate the fuel table by adding 20% to my VE Table during my tuning, and as soon as intake temps were lower, the table would be completely fubared and unusable and warm-up would be adversely rich and shooting raw gas and flames out the exhaust. So then I'd go and reduce my ASE and WUE so it wasn't so rich warming up on a cold morning -- and the next time the car got warm and i tried starting it, it would be very lean during warmup and worse as I drove... See the problem yet?
No? Okay, if I was tuning a boosted car it would be worse. Since the first days of MS2 the MAT corrections have been fucked. I tried very hard to have the MS developers change the code, but the best I could get was them to change the MAT corrections table to what it is today, instead of having to run an inverse table just to negate the built in ideal curve.
Fun Fact: Turbos create heat. Even with a really good IC, you should be seeing increased intake temps.
When you're in boost, you want to add fuel to: slow the burn, decrease cylinder temps, and increase knock threshold -- crazy concept.
The ideal gas law curve in the MAT Corrections -- as deezum posted -- ensures the MS PULLS fuel as your adding boost/heat into the intake. It only gets worse as your IC heatsoaks and AITs increase more. This is very dangerous.
That table needs an RPM decay, as well as a MAP threshold so you can basically disable it above a certain RPM and/or kPa value. There's no reason you should blindly be pulling fuel based on estimated intake temps, when you should be using closed loop fueling anyway. It's ******* dumb to try to pull fuel arbitrarily, just so EGO control puts it back in.
cliff notes: if you really hate yourself, and hate sound advice, use the ideal gas curve.
Last edited by Braineack; 09-07-2016 at 08:23 AM.