I know that the MAF can only read up to 255g/s of air flow, or somthing like that. I am thinking of building a miniramed 350 and want to know how far I can go while keeping my MAF. A custom PROM would be burned for it along with AFR190's and a descent sized cam to match. I'd like to keep my MAF and not have to go SD. What are your thoughts? Is it possible?

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"Though I cruise through the valley of Rice I shall fear no turbo, for torque art with me."
--Cullan Hooley
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1985 IROC-Z w/T-tops, 305 out and 350 L98 TPI engine in, Hooker Super Comp Headers, 3" Hooker Super Comp Cat-Back, 3" CatCo Cat, Rebuilt TH700R4 with Shift kit, 2,800RPM Torque Converter, 3.73 Richmond gears, Auburn differential, Accell SuperCoil, Accell 8mm racing wires, BBK AFPR, Homemade Ram-Air (thanks to Andris Skulte), MAF screens removed, Dropped A/C, Dropped A.I.R, TB coolant bypass, Hurst Dual-Gate Shifter, SLP Air Foil, K&N filters, Holley performance fuel pump, Spohn Subframe Connectors, Re-located Spohn Lower Control arms, and more to come.

 

I don't believe a 350 has enough cubes, even at 100% VE to max the MAF sensor. I may be wrong, but you arn't going to have any probs with the maf.

 

Actually some other folks and myself have done some calc's and figured out that 255 gm/s = approx 462 cfm. Using 100% VE, you would reach the ECM's 255 gm/s limit at around 4500 rpm(on a 350 cid motor). Dropping the VE to 90%(quite doable with a well setup MR, the limit is reached at around 5100 rpm. In either of the above cases, you would likely be at WOT before reaching the ECM's limit, which means the ECM is no longer relying on the MAF input.

 

According to TPIS the MAF system is good for up to 550 hp with the proper burn prom.

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1987 IROC w/T56 and a 377 MR in the works

 

Now if they could just figure out how to burn a PROM - lol. By the way, I have talked with individuals running a 350ci motor (fully upgraded, heads, cam, intake, etc) who are maxing out the ECM limit of 255g/s.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

When they are reading 255, is that a transient response(sudden throttle opening) or a continuous reading? Is this under WOT, or partial-throttle?

Just curious.

 

I guess it appears that SD is the unaviodable alternative. On a side note: What exactly happens when you max out the MAF? Check engine light? Stumbling?

 

When I hit the 255 reading it con't to pull, no light, no stumbling; if I didn't have diacom linked I wouldn't even know it. It only maxes at WOT and upper rpms. But I could probably obtain more power due to it only estimates after 255gm/sec.


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86 406

 

About how much power are you making now? I'm curious to how much MAF can support.


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82 Camaro:
350
Erson cam, ported heads,Comp Cams 1.6:1 rocker arms
Edelbrock Performer RPM intake, Holley 600
Crane Hi-6 ignition, Accel supercoil
TH350 tranny with 2500 stall.
Eibach Pro Kit
SLP 1 3/4" headers

 

The whole thing about the MAF is somewhat a misnomer. The limit is not MAF based. Its ECM based. The ECM uses an 8bit value. 8bit values have a maximum of 255. This is the 255g/s limit. The LT1 F-bodies used a 16bit value which provides a limit well above what any engine might need.

Those guys who are maxing out the MAF hit the ECM limit somewhere in the 4000+ RPM range. This is on a naturally aspirated 350ci engine. You can expect to hit this limit sooner with a bigger engine and/or forced induction. The reason that you don't necessarily feel a power loss is that the MAF calibration has a power enrichment table based on RPMs. Thus, at WOT the ECM will add/subtract fuel at various rpms INDEPENDENT of the MAF. This is how us PROM programmers 'fudge' the MAF system. If the 255 limit is encountered at 4000+ RPMs then that is ok. Since you are really only at 4000+ RPMs at only WOT then this WOT Power Enrichment table can be used to supply the extra fuel.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

mcconahay37... you quoted the wrong guy. I believe you were referring to the post by drive it. But I would also like to ask the same qeustion your asking to see just how far the MAF has been pushed, or to be more technically correct, the ECM.

 

To try and answer your question.... I'm not pushing the limits compared to other folk; I stayed conservative with my cam 222 and 226 at .050 on a 114 lsa.(Gotta pass Calif. smog!) On a hot day on a dynojet dyno before I started my own chip tuning-as in it was way too lean\too advanced, and audibly (painfully sounding) pinging and knocking: It was putting out 290rwhp and 425 ft lb rwtq. I've since done quite a few other mods along with real tuning. (diacom and burn my own!) Ive found big SOTP difference, so I'm looking foward to next years hot rod power tour to run free dyno's again!



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86 406