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Since my cam job, I've always had a "MAF only" tune. Going to upgrade my intake again and top end (CNC ported heads, FAST 92, LS2MAF...etc) so decided to finally do things the "right way" and tune my VE table with SD only, followed by retuning MAF with my new LS2 MAF, all this for preparation for the upcoming changes so I have a better tuning starting point. After a couple of days of tuning VE (SD open loop), I thought I was on point everywhere with AFR error being less than 2-3% on most of my VE where it mattered. WOT AFR was a damn near perfect 12.4-12.7 all the way, this was two days ago. Today (a cooler morning), I relogged to fix a specific lean tip in area and to my surprise my entire map was richer, some areas by an entire AFR point (WOT for example was now between 11.4-11.7). This is a large swing! I'm a little frustrated because my pulls were on point 2 days before, and the pulls were never done with a heatsoaked motor.
So now, I'm doubting if I even tuned my VE correctly by tuning it on a warmer day. Should I leave it and just proceed to doing the MAF portion as is or should I retune VE once again?
Yes, the IAT in the MAF because it came with it integrated in the LS2 MAF. I still have my older IAT too; the old IAT sits on the air bridge of my K&N Cold Air Intake, closer to the TB. See the picture.
Last edited by turabo87; May 27, 2020 at 11:49 AM.
For what it's worth, took a drive out today to lunch with much warmer weather than this morning, and the AFR %error was less. Much closer to target again with only about 3% rich from target AFR, including WOT.
Are you tuning with trims? Or just the WB?
What year is the car?
I'm tuning open loop, so no trims at all. I'm tuning with WB AFR, datalogging AFR% error of actual AFR vs commanded AFR. Using datalogging techniques I got from Goat Rope Garage in YouTube. My C5 is a 99.
Aaron, the LS2 IAT sensor uses the same data as the earlier separate IAT.
The 99 uses the smaller VE (secondary) table in SD. I assume that is the one you are tuning?
I recently tuned a 99 truck, I actually tuned the big table, then transferred the appropriate data to the small table. Worked well.
I have both primary and secondary VE tables. Every single time I do a change from my datalogs, I apply the changes to both tables to avoid issues. So every time I flash the tune, I always double check to have both tables share the same VE values.
I'm kind of tempted to start all over the VE tuning, staring by putting all the "Charge Temperature Bias" values to 1.0 on the entire Bias table, and then going from there to see if it helps (I currently have the Charge Temperature Bias tables with all stock values). Sucks because I would've just wasted 4 days of tuning if I go this path.
Heck, I'm tempted to just stop all together tuning until I put the new heads and intake in anyway. I feel I'm kind of wasting my time anyway if I'm going to put heads in the next month. I just never tuned VE since I put my cam last year, so I thought it would be good learning and make a good starting point before putting on heads.
Last edited by turabo87; May 28, 2020 at 10:05 AM.
FWIW I didn't touch the IAT bias tables for mine (they are called slightly different things since I use EFI Live...I think we are talking about the same table(s)) and it's been fine year round.
Yea I'm talking about the IAT vs ECT bias table. I bring this up bc after a heat soak (car parked after driving for a while and I turn car back on say 15 mins later), as the IAT shoots up my AFRs lean out, and as the heat soak diminishes after driving and getting some airflow, the AFRs go back to normal. It's always done this, and what I've read is that the charge bias tables being change to 1.0 on all values solves this issue but a complete retune of the VE is required again.
I bring it up bc I wonder if it's related to the same AFR swings I see with different ambient temperatures (cool morning vs hot day)
According to EFILive, value of 1 means charge air temp = CLT.....doesnt sound like a real solution at all.
I think hot starts will always have this issue to some extent with speed density, at least that's been my experience tuning a few SD setups.
- try to put the IAT sensor in such a spot where it is outside the engine bay/away from heat and the surrounding material doesn't radiate as much heat into the sensor. Looks like yours is already outside the bay somewhat and is plastic around it, so I don't know if you can improve upon this much. heatsoak is worse for someone like who has a metal tube now going into the TB (supercharged) and the IAT sensor is sitting right there above the radiator in a metal tube. I actually have a spot to put it in the intercooler as well, but I ended up just keeping it in the pipe.
- fuel trims are my savior until it cools off.
- I think heat soak is a similar but slightly different issue than just having fueling errors at different temps. EFIlive has a simple 2D table that is VE correction vs IAT, makes it easy to deal with small issues like youre seeing with different temps.
You ideally want to tune the VE table in a single session at the same temps etc. Dealing with heatsoak and other issues you should try to address with other tables (if possible).
After a few days of more logging and retuning reiteratively, I think it was partly my fault that I might have dialed in my WOT with a partially heat soaked IAT. I've been leaning out the WOT part little by little. Tuning SD in certain areas I find it to be very difficult, specifically some transient areas. I was able to tune my VE map to about 90-95% good within a day or two, but it's been weeks now to get the last 5%. I find it so damn hard to get the last 5% of the tune dialed in without messing up other areas that are already dialed in. I'm still rich in some tip in and acceleration areas, and ended up with some weird peaks and valleys on the WOT trajectory especially on low RPMs 1500-3000. I wonder if this is normal for some NA cammed cars. I'll try to take a picture of how my VE map looks.
I had a similar issue. I found that my timing was changing day to day. The car was nearly perfect one day, then rich as hell the next. It had switched over the low octane tune. Much less timing, could not burn the fuel.
Just another thing to check. See if you timing is where it should be, or low octane, or a blend of high/low.
I had a similar issue. I found that my timing was changing day to day. The car was nearly perfect one day, then rich as hell the next. It had switched over the low octane tune. Much less timing, could not burn the fuel.
Just another thing to check. See if you timing is where it should be, or low octane, or a blend of high/low.
Thanks, but no my timing has been consistent. I've checked KR and I'm at 0.0. Randomly I might see 0.1-0.2 degrees pulled at some tip in scenarios, but it's mostly super consistent. 93 octane here everyday.
Also, my spark timing table values are identical for consistency (low octane table = high octane table)
Alright, keeps getting weirder. So my driveablity areas are perfectly on point. Only WOT is still rich. The more fuel I remove from the VE WOT area of map, the richer the WOT becomes. I'm stumped. Still between 11.5-12.0 AFR. I'm getting tired of thing. WOT fueling is supposed to be the easiest thing to tune and it's kicking my ***. I might call it a day on Speed Density tuning, and switch back to MAF only. MAF is so much more consistent.
Weather is rainy here today so might not be able to log WOT. I did however find part of my issue. Looks like my AFR wideband math was a bit off, by 0.3 points when compared to my AFR gauge. So my datalogs were showing 0.3 leaner than what the AFR gauge was actually showing, so every time I looked at my AFR gauge while on a pull it was always richer than expected. Now that my AFR math actually matches my gauge, I'll datalog when I have a chance.
Well got it to the dyno today to have it baselined before I put my new heads and I was able to dial it in the WOT.
I was actually on my way in the right direction, it just needed a little more of leaning out but my AFR was super flat, so I guess I did a good job on my street tuning. First pull was at between 11.8-12.1. Second pull I leaned it to 12.5 and was rock solid between 12.3-12.6.
Made healthy 385whp SAE. AFR between pull 1 (my Speed Density street tune) and pull 2 leaned to 12.5. Best pulls on STD Best pulls on SAE
Open Loop VE SD Tuning: Chasing my tail
