I have the stock L98 MAF that has the usual mods done to it. Screen' removed,fins knocked out. How much HP can it support? I assume it's flowing around 730-750cfm.

Thanks

KelvinM

 

730-750 CFM

That pretty much sums it up. It supports the airflow that a 750 CFM carb supports. Horsepower can go a long way with that...but you need the cam/heads/displacement/intake and tuning to make it all work regardless.

 

I guess what I'm struggling with is this. Take a typical 350 with a good set of heads and a cam to match. Wouldn't it's cfm requirement at full throttle exceed 750cfm? I would think it would need around 1200-1400cfm @ WOT.

So are you saying that 750cfm should be fine for an engine that's capable of 500-600HP? I'm just trying to understand the correlation.

Thanks

KM

 

You wont even be able to pull in 1000cfm anyway on a 350.

750 is plenty on the 350. Now to get 500-600hp out of one youll have to use juice, or some forced induction that would push that much air into it. 500hp is reachable (crank) with the right combo but 600 would be hard w/o juice or SC/turbo.

 

Two converging lines of thought, assuming normally aspirated and no nitrous.

1) The MAF of a modified L98 probably maxes out at 750cfm. The MAF from an LT1 can flow 1000cfm with a plastic (granatelli?) housing. These flows are, by convention, measured on a bench with a set vacuum (often 4in water). Just as you wanted a carb to be slightly oversized so the flow you need will be at less vacuum for higher volumetric efficiency, you would like the throttle body, MAF, Air Filter, etc to be perhaps 10% larger in capacity than your engine will flow so as to increase volumetric efficiency. The limiting factor is usually the Air Filter itself. Remember also that this is dry flow- no fuel vapor is present, unlike a carb, so a 750cfm MAF is equivalent to an 800 cfm carb (14:1 AF ratio).

2) Calculating the engine air flow is a straightforward formula involving cubic inches, rpm, and volumetric efficiency. For a 383 at 7000 rpm, with good headers( VE100%), the number comes out close to 850 cfm. For a 350 at 6000rpm the number is about 680cfm. Less than you would guess. For super/turbocharging the VE must be modified according to the boost. Nitrous injection is usually in the intake manifold, so the calculations for the MAF, Throttle Body, and Air Filter do not change. (The cylinder head ports and valves calculations do change markedly, as does the exhaust system).

So the modified L98 is pretty good for a 350, and a modified LT1 will work for a hot 383 or more. Again, the Air Filter or its plumbing is often the critical restriction.

 

Okay, so a modified L98 MAF can flow up to 750cfm. But how much of that airflow can it actually measure and signal to the ECM, and how much of the signal can the ECM interpret? If what I keep hearing is correct, it isn't possible to use all of that 750 cfm with the stock electronics.

 

This is where a lot of folk switch to speed density......the older maf systems can "see" a max airflow of 255gps. My 406 at lower altitude maxes at 255 at about 4500rpm.
Yes you can still run it-you need a wideband to adjust the F/A ratio vs rpm at wot to "band-aid" it. Then it'll work fine.
However a lot of folk (at that other site) get pretty huffy and say that's not the correct way......
I'll have to see where it maxes out now with the SC.......