WTF is causing this lean 1st gear?
Thread Starter
Moderately Differentiated
iTrader: (4)
Joined: Nov 2004
Posts: 27,408
Likes: 0
From: Maryland
WTF is causing this lean 1st gear? power enrichment table is per RPM. I am commanding a lean 12.12 due to the meth. I am loooking to see a 11.7 to 11.8ish here, NOT 12.5!!!!! Why only in first gear am I battling to get this afr in line. if I richen the pe vs rpm in this area the higher gears will go real rich, obviously so. Why is 1/2 shift (or really first gear) such a bastard? I have my meth on at 3.5#'s of boost right now. I have the rpm switch on all times. So at this spot (12.5:1) my meth indicator lights are on, so pump is working, meth is flowing (supposedly). It fattens up after the shift. Hope you can see this pic.
Last edited by dewmanshu; Jun 6, 2006 at 12:37 PM. Reason: made pic larger
Kinda hard to see the graph...what's your commanded vs. WB reading? Curious to know if you are commanding 12.5 or if that's just what you are getting. Also, does it do the same thing when the meth is turned off??
Thread Starter
Moderately Differentiated
iTrader: (4)
Joined: Nov 2004
Posts: 27,408
Likes: 0
From: Maryland
Originally Posted by muncie21
If your commanded vs. actual is off above 4K RPM, I'd say you either have a small air leak or your MAF is off at the Hz setting.
My maf hertz is 11291 at the 12.5 spike. And in second gear at 11250 hertz I am getting what I am trying to get, 11.7. A small air leak could very well be a possibility in my left bank. By why would it only affect my reading in first gear?
Thread Starter
Moderately Differentiated
iTrader: (4)
Joined: Nov 2004
Posts: 27,408
Likes: 0
From: Maryland
I just notice my timing dips off right around the same time the afr comes back to norm. At 1.04 g/cyl I am commanding 20*. At 1.12 I am commanding 19*.
Hmmm.
also, my injector (ms) is 1ms different between being 12.5afr and 11.8afr. That seems to be a big difference as well.
@ 12.5 AFR (1st gear) and 5898rpm the injector ms is 16.7 and 17.0. Dyn air is 1.04 g/cyl and maf is 11291hertz.
@ 11.7 AFR (2nd gear) and 5873rpm the injector ms is 17.7 and 18.0. Dyn air is 1.12 g/cyl and maf is 11611hertz.
Hmmm.
also, my injector (ms) is 1ms different between being 12.5afr and 11.8afr. That seems to be a big difference as well.
@ 12.5 AFR (1st gear) and 5898rpm the injector ms is 16.7 and 17.0. Dyn air is 1.04 g/cyl and maf is 11291hertz.
@ 11.7 AFR (2nd gear) and 5873rpm the injector ms is 17.7 and 18.0. Dyn air is 1.12 g/cyl and maf is 11611hertz.
Last edited by dewmanshu; Jun 6, 2006 at 12:52 PM. Reason: more info
The graphs are actually readable now...thanks. Here are some random thoughts that may help....and maybe not.
==Fueling==
Is it possible that your fuel pressure goes down momentarily when punching in from first? Put a gauge on it and find out.
You may also want to lower the conditions to go into PE, then do some pulls in first and see if commanded vs. actual AFR is RPM dependent or load dependant. Also try driving steady at like 3500 (check to see if AFR is smooth) then punch it and see if you have the lean spot you see when you go from a start.
The injector PW doesn't really make sense. If the PW goes down, you'd expect less fuel to be going in, not more...I.E. running leaner at lower pulse width, not richer....unless you fuel pressure isn't stable.
==Airflow==
The initial in-rush of air could be confusing the MAF. MAFs aren't accurate during sudden throttle transitions. First gear would be the worst, cause you would be going from 40-50kPa to 100+, rather than 80 to 100 like when you shift.
You can test if the MAF is to blame by putting the car in SD mode and then checking your AFRs. You may have to dial them in, but what I'd be looking for is a trend of first gear running leaner than commanded.
Then of course there is the air leak issue. I've currently got a lean surge in bank 2, that only happens at 2000 RPMs. Pretty sure it's an airleak, but haven't been able to pin it do
wn yet.
==Fueling==
Is it possible that your fuel pressure goes down momentarily when punching in from first? Put a gauge on it and find out.
You may also want to lower the conditions to go into PE, then do some pulls in first and see if commanded vs. actual AFR is RPM dependent or load dependant. Also try driving steady at like 3500 (check to see if AFR is smooth) then punch it and see if you have the lean spot you see when you go from a start.
The injector PW doesn't really make sense. If the PW goes down, you'd expect less fuel to be going in, not more...I.E. running leaner at lower pulse width, not richer....unless you fuel pressure isn't stable.
==Airflow==
The initial in-rush of air could be confusing the MAF. MAFs aren't accurate during sudden throttle transitions. First gear would be the worst, cause you would be going from 40-50kPa to 100+, rather than 80 to 100 like when you shift.
You can test if the MAF is to blame by putting the car in SD mode and then checking your AFRs. You may have to dial them in, but what I'd be looking for is a trend of first gear running leaner than commanded.
Then of course there is the air leak issue. I've currently got a lean surge in bank 2, that only happens at 2000 RPMs. Pretty sure it's an airleak, but haven't been able to pin it do
wn yet.
Trending Topics
Thread Starter
Moderately Differentiated
iTrader: (4)
Joined: Nov 2004
Posts: 27,408
Likes: 0
From: Maryland
Good idea on the MAF...I'll try SD. I really want to blame this on the MAF.
On the injector pw, i may have mistyped, but it does stay low while the AFR is too lean and it does go up as the afr goes richer.
On the injector pw, i may have mistyped, but it does stay low while the AFR is too lean and it does go up as the afr goes richer.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Originally Posted by dewmanshu
@ 12.5 AFR (1st gear) and 5898rpm the injector ms is 16.7 and 17.0. Dyn air is 1.04 g/cyl and maf is 11291hertz.
@ 11.7 AFR (2nd gear) and 5873rpm the injector ms is 17.7 and 18.0. Dyn air is 1.12 g/cyl and maf is 11611hertz.
@ 11.7 AFR (2nd gear) and 5873rpm the injector ms is 17.7 and 18.0. Dyn air is 1.12 g/cyl and maf is 11611hertz.
Thread Starter
Moderately Differentiated
iTrader: (4)
Joined: Nov 2004
Posts: 27,408
Likes: 0
From: Maryland
Originally Posted by SSpdDmon
Just by those facts alone, I'd say you need to increase the MAF around 11250Hz and 11375Hz. You're still 250Hz (2 cells) away from where you were in second gear when you took that reading.
Well it did with normal shifting. At 5900. But shifting at 6250 it hit 12.3. I am done testing this, it's go fry something. It's is 12+ for only 2 seconds. 2 seconds too long.
I guess I'll go SD for a quick spin and just eliminate the MAF to see if that helps. I just hate doing WOT with a 1bar map/ve and no maf above 4k. I'll bump my ve table up by 15% in the high rpms.
You know, looking at my 2 runs I just did I see the Injector PW follows the what gear I am in. 16 to 17 ms in first gear. Then 17 to 18 in second gear. and then 18 to 19 in third.
Why is this. More importantly...where can I command more pw in first? LOL
Everybody who has a radix and a return fuel system...what do you have for your values in the Injector Flow Rate vs KPA VAC?
Why not just up the MAF in the areas where you're lean? 2% for everything above 9625 is going to throw off the areas that were right. You do know how to log MAF % Error, right? Say at a given Hz (12125), you log an average commanded afr of 12.0. Your wideband reports an average of 12.5. 12.5/12.0=1.04. Then, you just increase 12125Hz by 4%...or 2% if you want to prevent "overshoot." Rinse & repeat.
Thread Starter
Moderately Differentiated
iTrader: (4)
Joined: Nov 2004
Posts: 27,408
Likes: 0
From: Maryland
Throw off? Sure but real quick I can see if the plus % across the range gets the job done. Just trying to hit the cells that IMO aren't for sure the trouble areas because looking through the scan (exported to excel and sorted) the range does get shorter and even over lap every so often. So, that's my insane rationale. LOL The % increase didn't help my cause. At least now I know it wouldn't be because I increased the wrong area.
Nevertheless, question for ya, I am guessing fixing the spot in the MAF curve that would help this would make for a horrible spike in the maf. Isn't that against common tuning practices, at elast concerning the maf.
Nevertheless, question for ya, I am guessing fixing the spot in the MAF curve that would help this would make for a horrible spike in the maf. Isn't that against common tuning practices, at elast concerning the maf.
Thread Starter
Moderately Differentiated
iTrader: (4)
Joined: Nov 2004
Posts: 27,408
Likes: 0
From: Maryland
Originally Posted by SSpdDmon
You do know how to log MAF % Error, right?
bigger injectors may be needed there but your allways going to be leaner in lower gears, tune in 4th, or tune for what kind of driving your doing, if your allways at 5800rpm in 1st gear then worry about your lean spot, but if your going to be on the gas for a while like drag racing or highway runs its going to be different... I drop around .1afr per gear, so 1st seems lean but its only there for a second and there isnt a hard load on the engine like higher gears...
Thread Starter
Moderately Differentiated
iTrader: (4)
Joined: Nov 2004
Posts: 27,408
Likes: 0
From: Maryland
Good point, certainly understand I can get away with the leaner afr in the lower gears due to less load. But, I am a truck...it does weigh 5400, and it's more than .25 a gear. That's my worry. It's such a big difference. I am going to go 2 bar. I imagine I shoudl be able to tackle this alot easier with pe and be. Just curious if this is something in th etune I should be worried about. Doesn't seem to be the maf to me now.
