Rich after Flash

[GHuggins]

It's not the purge.... It's due to the ecm having to relearn and back calculate everything from temp parameters. If you notice when you do a restart, your intake valve temp restarts somewhere right around coolant temp then immediately starts counting back up. I imagine all temp parameters are doing the same thing - injector, intake and so on until the 10 to 15 minute idle period has passed. I also noticed that it typically waits and "fine tunes" it's own calculations until after you have atleast free revved it a little or ran it through the gears once, then it will settle in one place. At that time you can ussually reset your fuel trims and start your datalogging. I also can not emphasize enough on the importance of allowing it to go through atleast 1 or 2 cold start to operating temp idles sitting still without load after final programming. Will save on any unforseen restart issues durring temp cycles down the road...

All programmers (Including OE, SCT, Diablo & HP that I can confirm) have this issue... It's just a relearn that it unfortunately has to go through. AND as previously stated, the closer the tune gets, the less time it seems to take. The worst I've had it was 15 minutes, so I try to let it idle that long, run it through the gears, come back to stop then start datalogging. I've also noticed it's way worse in VE setup vs combined. If it's a starter tune, I datalog in open loop as it's not as temp calculation sensitive right from restart, then durring closed loop tuning use the wait period if that would help anyone...

NOW with all that being said I did just have one really kick my butt where 3" aftermarket non heat shielded exhaust was installed on a corvette and while on the dyno after about mid morning it would start boiling or super heating the gas in the tank causing the purge to pull in excess vapors throwing things off. Was able to get a fan blowing across under the tanks to cure that. Never the less it also got exhaust wrap and tank insulation afterwords... BUT this is the only time purge has been an issue.

[SPRAYED 01]

I uploaded a new ve table to my SD 3 bar setup last night. Drove 20 miles and it still hasn't reset. Did a couple wot blasts today and I still don't think it's back. Had the drivability ve really nice now it's telling my in off 6-9% at idle and light throttle cruising. Do you need to relearn fuel trims even when tuning in open loop?

[Michael_D]

It's not the purge.... It's due to the ecm having to relearn and back calculate everything from temp parameters. If you notice when you do a restart, your intake valve temp restarts somewhere right around coolant temp then immediately starts counting back up. I imagine all temp parameters are doing the same thing - injector, intake and so on until the 10 to 15 minute idle period has passed. I also noticed that it typically waits and "fine tunes" it's own calculations until after you have atleast free revved it a little or ran it through the gears once, then it will settle in one place. At that time you can ussually reset your fuel trims and start your datalogging. I also can not emphasize enough on the importance of allowing it to go through atleast 1 or 2 cold start to operating temp idles sitting still without load after final programming. Will save on any unforseen restart issues durring temp cycles down the road...

All programmers (Including OE, SCT, Diablo & HP that I can confirm) have this issue... It's just a relearn that it unfortunately has to go through. AND as previously stated, the closer the tune gets, the less time it seems to take. The worst I've had it was 15 minutes, so I try to let it idle that long, run it through the gears, come back to stop then start datalogging. I've also noticed it's way worse in VE setup vs combined. If it's a starter tune, I datalog in open loop as it's not as temp calculation sensitive right from restart, then durring closed loop tuning use the wait period if that would help anyone...

NOW with all that being said I did just have one really kick my butt where 3" aftermarket non heat shielded exhaust was installed on a corvette and while on the dyno after about mid morning it would start boiling or super heating the gas in the tank causing the purge to pull in excess vapors throwing things off. Was able to get a fan blowing across under the tanks to cure that. Never the less it also got exhaust wrap and tank insulation afterwords... BUT this is the only time purge has been an issue.

That is the most informative thing I ever seen written on this subject. Your hypotheses sounds solid to me. Thank you for taking the time for that post!

[openwheel25]

I also would like to thank you for taking the time to post this information. I have a question about looking a temps. Can you watch the valve temps and wait for them to stabilize to know it is through with it's running rich? It would be nice to know that it has completely stopped and when to know to start paying attention to the data. Thanks again for you write up. You are the first person to know that all programmers have the same problem. It is so big of a problem that I was willing to switch to a different programmer.

[GHuggins]

Unfortunately, I know of no way to 100% tell whether or not it's through with it's rich after flash issue. I DO know that if it sits long enough to completely cool down and was started atleast once before shut down, it should automatically be cleared out. I just find it best to give it it's 15 minutes and run it a little to be 90+% sure.

Sorry couldn't be more help.

[schpenxel]

I have had this problem basically any time I'm running closed loop.. I don't know why, but the fuel trims always go high at first.

I can drive the car a while, turn it off, start it, and fuel trims will be close to where they were when I turned it off

If I drive a while, turn if off, flash it, then start it, fuel trims go 8-10+% for a while.

Don't ask me why.. but I've tried it over and over and over, and it does it every single time, even with the evap system disconnected.

A good 30 minute drive of varying loads usually gets it back down to normalcy.

[openwheel25]

I have another question, While tuning WOT have you noticed this being a problem in the WOT areas. When renting dyno time for WOT tuning it would be expensive to wait fifteen minutes or so every time it is flashed. I have had my car on the dyno and it seemed like this problem didn't effect WOT. But, I was naïve to this problem when I had it on the dyno. I didn't do many WOT pulls because when tuning the drivability the rich after flash made me think I had a mechanical problem and I took it off the dyno and removed the intake and heads looking for a problem before I discovered that it was a pcm problem. So I have been tuning the drivability on the street. Waiting after flash and letting it cool down. I would like to do WOT on a dyno for safety but, if this problem is also in WOT it might take all day to tune WOT renting a dyno by the hour could be expensive not to say if I can find a dyno that will let me spend all day.

[GHuggins]

Unfortunately it effects it durring WOT if the ecm is adding fuel to ltft's as well. Have you ever noticed how your wot fuel air fuel ratio can and will change just in the course of 3 to 4 back to back dyno pulls? I always do atleast 3 back to backs to get an average.

If you put it into open loop and reset fuel trims via scanner output controls, it's not as bad due to the fact that ltft's won't effect it and it gets very close to what your commanding. To be 100% I do the wait out and yes it takes forever to tune right.

[Force]

Does this happen with an E40 ecm? Mine is VE tuned and then tuned using the Maf all in open loop and I have not noticed any great amount of rich running after a flash. It might run rich for a minute but I thought it might be the temp sensor in the PD blower manifold copping heat soak and effecting fuelling. The truck stays in open loop once tuned. So is it only with the E38 and E67 ecms?

[GHuggins]

Doesn't effect open loop as bad as hinted in my last post. In fact, I do open loop tuning data collection without waiting for the clear out time to help save time. Seems to effect all ecms and vehicles, but certain ones are definately worse than others in regards to the time it takes to clear out and how much it will throw the fuel trims off such as when you add boost to originally NA vehicles, it seems to take longer. I was personally wondering if on top of the relearn if it wasn't some sort of safety protocol the manufacturers put in the background of their more high performance ecm based vehicles. A safety measure if you will since they go rich afterwords. I've also noticed even the Fords do this with SCT, but nowhere near as bad as the gm's. Ever had a mustang on the dyno you just flashed, wait 5 to 10 minutes for it to warm up then do 3 pulls and watch the fuel trims completely change afterwords? I've even had it so bad on the Fords, that I've had to reset KAM after driving them for 20 minutes to get ltft's right. Basically they all do it. Just some are worse than others. It's just once you know what to watch for, you can see it happening easier. Relearn combined with safety combined with who really knows what?

[schpenxel]

I was going to say basically the same.. it doesn't seem to make as much of a difference while running in open loop

It seems like a combination of temperatures that are calculated (not measured) being reset and having to work their way back to where they'll normally be, and the fuel trim "learning" starting on the rich side and working down.

Or I'm just crazy and seeing things.

[Force]

Thank you for the info. it is all very helpful.

[edge04]

I was going to say basically the same.. it doesn't seem to make as much of a difference while running in open loop

It seems like a combination of temperatures that are calculated (not measured) being reset and having to work their way back to where they'll normally be, and the fuel trim "learning" starting on the rich side and working down.

Or I'm just crazy and seeing things.

want to be clear here (if that's possible). I have experienced the rich after flash. I drive in all different conditions for 10-15 mins and key off and back on it seems to have re-learned. But are we saying that it does or does not impact open loop tuning. You and GHuggins say "as bad" and I have read elsewhere not at all. Does it impact open loop at all?

[schpenxel]

want to be clear here (if that's possible). I have experienced the rich after flash. I drive in all different conditions for 10-15 mins and key off and back on it seems to have re-learned. But are we saying that it does or does not impact open loop tuning. You and GHuggins say "as bad" and I have read elsewhere not at all. Does it impact open loop at all?

I can only give my opinion since I haven't tuned tons of cars.. and my opinion is it does still impact it, but only long enough for the intake valve temp reading to get back up to where it would normally be. You'll notice it resets after a flash and starts at engine coolant temp, then works its way up as you drive the car. When I'm tuning in open loop I usually just drive until the IVT reading is to a point where it stabilizes and is near where it was prior to the flash.. and then start logging

[edge04]

I can only give my opinion since I haven't tuned tons of cars.. and my opinion is it does still impact it, but only long enough for the intake valve temp reading to get back up to where it would normally be. You'll notice it resets after a flash and starts at engine coolant temp, then works its way up as you drive the car. When I'm tuning in open loop I usually just drive until the IVT reading is to a point where it stabilizes and is near where it was prior to the flash.. and then start logging

can you log IVT in the scanner? can probably figure that one out but lazy right now

[10_SS]

I can only give my opinion since I haven't tuned tons of cars.. and my opinion is it does still impact it, but only long enough for the intake valve temp reading to get back up to where it would normally be. You'll notice it resets after a flash and starts at engine coolant temp, then works its way up as you drive the car. When I'm tuning in open loop I usually just drive until the IVT reading is to a point where it stabilizes and is near where it was prior to the flash.. and then start logging

If you go WOT right away after flashing, does IVT jump up to where it normally is? Or at least jump up fast? That may explain why some people say the richness goes away after going WOT...

[schpenxel]

can you log IVT in the scanner? can probably figure that one out but lazy right now

yes you can log IVT

If you go WOT right away after flashing, does IVT jump up to where it normally is? Or at least jump up fast? That may explain why some people say the richness goes away after going WOT...

It goes up faster the harder you drive, not sure how fast though. and there may be other things that have to "reset' like that.. that's just one that I've noticed

[edge04]

is the rich after flash associated with all ECM's? If someone know which do and which don't that would be good to know. Thanks

[Michael_D]

I have fought with this phenomena on my E38 equipped car for two years now. If you are calibrating in closed loop, either STFT or LTFT, forget it. There is no rhyme or reason to when this will occur, how long it will take to get into ‘normal’ mode, or how many times you may have to stop/start the engine. I have not found any pattern that is repeatable. All you can do is just drive around and monitor your trims. It has been so bad at times, that I just park the car and let it sit overnight. Then start it the next morning and all is good….. It is beyond aggravating.

But, I did have enthusiastically fantastic results calibrating in open loop a couple weeks ago. Others may have different results, but I’d suggest trying it. When you put the ecm into open loop, kill all the OL fueling multipliers. Open all the tables, and change the entire tables to “1”. Then just use your wide band. The last time I did this, I probably flashed a dozen calibrations and did not see any funky rich-after-flash issues whatsoever. It was wonderful.

[409Jake]

I had a 2014 ZL1 a couple weeks back that was the worst. I was in open loop the entire time and had the rich issues after each flash, no matter what changed on the tune. I would run it for awhile, shut if off, run it again, go wot a couple times, pulled the battery, ran around with foil on my head and never found the quick fix lol. Hopefully one of us tracks it down one of these days .