MAF

[Barry E. King]

I have an 83mm ProM airmeter in a 3.0L Mitsubishi 3000GT VR4 (twin turbo).
It is supposedly calibrated for 1000 cfm.  I also have larger blowers (404
cfm @15 psi each) but drivability (primarily off boost of course) is not an
issue.  20 psi boost performance is astounding.  The stock MAS was much much
smaller and with the new one I am sure that other areas are now the
restriction.

I would think that if this 3.8 will ultimately see a turbo a larger MAF is
doable.  75mm-77mm is being done on 2.0L DSMs mind you they are running much
higher boost.

The trick is being able to tune for it.  I am using the TRE MASC for this
purpose http://www.teamrip.com.  Works great so far.  The MASC comes in two
flavors, just the computer (adjusts frequency of the input signal from the
factory MAS) or computer + ProM airmeter.  In the latter configuration it
converts the voltage from the ProM to a frequency the stock ECU can
understand and adjusts the frequency to affect mixture changes.


Regards,

Barry
Not affililated with TRE other than as a customer ;)

> -----Original Message-----
> From: owner-diy_efi at efi332.eng.ohio-state.edu
> [mailto:owner-diy_efi at efi332.eng.ohio-state.edu]On Behalf Of Greg
> Hermann
> Sent: Monday, November 02, 1998 8:20 PM
> To: diy_efi at efi332.eng.ohio-state.edu
> Subject: Re: MAF

> 170 Gm/sec works out to 300 cfm (and about 205 HP) (at sea level), which
> works out to 84% or so VE--on the low side, which indicates a lot of
> restriction from the MAF!  If the thing only has a 25 mm diameter throat,
> your MAP at WOT can only get up to about 12.0 or 12.5 psia. (Basically ,
> the MAF is throttling the engine!) Going to a much bigger MAF could
> definitely help things, to the tune of another 6 to 12% power at the top
> end. Doesn't much matter where you put corks in a system, things don't
> really get freed up until you pull out the last cork. No way a 25 mm
> orifice is NOT a serious CORK on a 3.8 l. engine---with one carb
> barrel per
> cylinder (Webers) SIX 30 mm venturis would be pretty restrictive on a 3.8
> l. 6 cyl.--I once built a Jag 4.2 (6) which ran FINE with SIX 42 (!) mm
> chokes (one in each of the six bores of its 3 (48 mm throttle) Webers). If
> one cannot run a MAF with a FAR bigger hole in it than this one (like at
> least 60 mm) without getting "driveability problems", it is time to either
> throw the  MAF's away and go with MAP injection, or go back to (GOOD)
> carbs!!!>
>
> Regards, Greg