Gutted my MAF today.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Gutted my MAF today. (bjankuski)
A 4mph loss of trap speed is about a 40hp drop; on a basically stock L98 that's about 17%!! You could boost fuel flow about 12% (going from 44psi to 55psi) with an AFPR but not that much.
I'm wondering if some of this observed difference is due to the electronics since they were not the same MAF. TPIS showed air flow goes from 529cfm to 711cfm with screens out and to 750cfm with fins removed. That's only a 5% bump in air flow due to fins removed. Even if it's not seen by the sensor it wouldn't account for the 17% power loss (unless of course the power drop isn't linear in this range of air/fuel??).
Nevertheless, you raise an iteresting point here. This is why tuning with an AFPR and/or reprogramming the fuel curve is needed even with a MAF.
A recent dyno pull showed an A/F ratio of 12.6-12.8 at WOT in 3rd gear, with my AFPR set at 47-48psi, stock CALPAC and gutted MAF (no fins). The car dynoed at 247rwhp or about 300 at the crank which is about right for FP increase and stock injectors. I haven't taken MAF air flow readings with the scanner nor done the math to see if they compute to 12.6-12.8 ratio but that would be an interesting test to see if my MAF is reading correctly.
The reason that more air could drop power is that in this case it's not measured air (like false air) so the ECM, at WOT, can't add enough fuel to maintain the max power ratio. What was stated above is that, though more air flows through the gutted MAF, less would be going through the central sensor tube. Even if this is the case, my dyno data shows that it can be easily compensated by a rather small fuel pressure adjustment.
So Scorp, you're OK with the fins in the MAF untill you get near that limit of air flow but it woun't hurt to remove em now.
I'm wondering if some of this observed difference is due to the electronics since they were not the same MAF. TPIS showed air flow goes from 529cfm to 711cfm with screens out and to 750cfm with fins removed. That's only a 5% bump in air flow due to fins removed. Even if it's not seen by the sensor it wouldn't account for the 17% power loss (unless of course the power drop isn't linear in this range of air/fuel??).
Nevertheless, you raise an iteresting point here. This is why tuning with an AFPR and/or reprogramming the fuel curve is needed even with a MAF.
A recent dyno pull showed an A/F ratio of 12.6-12.8 at WOT in 3rd gear, with my AFPR set at 47-48psi, stock CALPAC and gutted MAF (no fins). The car dynoed at 247rwhp or about 300 at the crank which is about right for FP increase and stock injectors. I haven't taken MAF air flow readings with the scanner nor done the math to see if they compute to 12.6-12.8 ratio but that would be an interesting test to see if my MAF is reading correctly.
The reason that more air could drop power is that in this case it's not measured air (like false air) so the ECM, at WOT, can't add enough fuel to maintain the max power ratio. What was stated above is that, though more air flows through the gutted MAF, less would be going through the central sensor tube. Even if this is the case, my dyno data shows that it can be easily compensated by a rather small fuel pressure adjustment.
So Scorp, you're OK with the fins in the MAF untill you get near that limit of air flow but it woun't hurt to remove em now.
Pro
Joined: Apr 1999
Posts: 740
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From: Chelmsford, MA USA
Re: Gutted my MAF today. (scorp508)
I've been curious about this too. I've read that you can pick up about 180cfm more over stock. But I don't want to tweak my origianal MAF. So I've been checking the bone yards for one. '86-88 305/350 Camaros, Firebirds and of course vettes should have the same MAF. No luck yet in finding one.
Bob
Bob
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
