Decel question, 32B & Tunerpro RT
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Joined: Mar 2004
Posts: 79
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From: SF Bay Area, California
Car: '87 Corvette Convertible
Engine: 421 CID, Superram, LPE219, AFR 195s
Transmission: Built A4
Axle/Gears: D44 w/ 3.07s
Decel question, 32B & Tunerpro RT
I'm helping a friend with his modified 383 in an 88 Corvette. I've got idle and part throttle C/L fueling looking pretty darn good, but it's got a discrepency during decel I don't quite understand. On occasion (not always) the BLMs will swing between 120ish and 138 depending on what fuel cell it's in (see attached screenshot). Even though that's not too too bad, it bugs me & I'd like to learn how to work it.
This 32B definition is rather limited and there's no applicable DFCO/decel constants to work with such as what I'd find in 6e; and there are no BLM cell boundries in the def file to adjust. If you look at the attached log, you'll notice the airflow (12+ GPS) and load are very close to being the same in these two areas, the only appreciable difference are the declining RPMs as the car decels.
My thinking is to recalibrate the MAF tables in the lean area even though the airflow is the same as where I'm rich; then maybe give it some timing to bring the richer BLMs back into line since they're more than likely to get worse. Am I on the right track here? The only other thought I had was to get into the BPW vs Load table, but frankly I'd rather not.
Any thoughts would be greatly appreciated!
This 32B definition is rather limited and there's no applicable DFCO/decel constants to work with such as what I'd find in 6e; and there are no BLM cell boundries in the def file to adjust. If you look at the attached log, you'll notice the airflow (12+ GPS) and load are very close to being the same in these two areas, the only appreciable difference are the declining RPMs as the car decels.
My thinking is to recalibrate the MAF tables in the lean area even though the airflow is the same as where I'm rich; then maybe give it some timing to bring the richer BLMs back into line since they're more than likely to get worse. Am I on the right track here? The only other thought I had was to get into the BPW vs Load table, but frankly I'd rather not.
Any thoughts would be greatly appreciated!
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Joined: Sep 2007
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Re: Decel question, 32B & Tunerpro RT
Under decel you're typically operating at very small pulse widths, when decelerating outside of DFCO.
I would look at the low pulse width injector offset table and add some fuel between approx. 1.5 and 2 ms. Looks like your ok around 1 ms, but too lean in the vicinity of 1.5 ms.
I would look at the low pulse width injector offset table and add some fuel between approx. 1.5 and 2 ms. Looks like your ok around 1 ms, but too lean in the vicinity of 1.5 ms.
Thread Starter
Junior Member
Joined: Mar 2004
Posts: 79
Likes: 0
From: SF Bay Area, California
Car: '87 Corvette Convertible
Engine: 421 CID, Superram, LPE219, AFR 195s
Transmission: Built A4
Axle/Gears: D44 w/ 3.07s
Re: Decel question, 32B & Tunerpro RT
Thanks for weighing in tequilaboy! Unfortunately this definition is fairly limited; aside from AE and Async related tables the only thing it has is a BPW vs Load table and the resolution isn't real good on that one.
I think I'll use this as a last resort, but fortunately for us the problem isn't too bad as it only passes thru these rich and lean areas sporadically and then it's for just a short period of time. Aside from that, it's within 4 BLM counts either way under load.......so it's not a significant problem at all.
Happy Easter & thanks again!
I think I'll use this as a last resort, but fortunately for us the problem isn't too bad as it only passes thru these rich and lean areas sporadically and then it's for just a short period of time. Aside from that, it's within 4 BLM counts either way under load.......so it's not a significant problem at all.
Happy Easter & thanks again!
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