High Flow MAF revisited - (Porsche 928 voltage MAF)

[Mark Romans]

Regarding installing a larger MAF sensor. Bruce is right, there is more to
it than just installing a larger MAF.  The code only recognizes up to 255
grams/sec.  So even if you get a maf that will read 500 grams/sec the ecm
won't.  There are probably some people on this list who could write a patch
to make the ecm recognize 510 grams/sec but I am not one of them and it
would take a tremendous amount of time.

Installing a later model gm freq maf is really involved too, the 165 ecm
using 89 code doesn't recognize freq or over 255 grams/sec so there are
several issues involved.

I suspect that if one is really serious it would be easier to convert to 730
ecm or Speed Pro FI with wide band and be done with it.

Mark
-----Original Message-----
From: Thomas Matthews <tmatthew at stny.lrun.com>
To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
Date: Sunday, January 16, 2000 6:01 AM
Subject: Re: High Flow MAF revisited - (Porsche 928 voltage MAF)


>I figured that it would take a lot of messing around to get it right...
>But are they similar in their non linear response?
>Now if someone had the table of 89 MAF voltage to GPS, then could compare
>the linearity of the two sensors, and fudge the tables in the ECM to
>compensate for the difference- I would guess that would leave you pretty
>close.
>I guess the real answer would be to build a straight F/V converter, and
flow
>the 2 sensors to build a response curve of each, CFM /vs voltage, but I
have
>no access to a flow bench...
>SLP used to sell the 3.5 Bosch MAF with a translator, FYI... If anyone had
a
>contact at SLP or one of these translators that they could reverse
engineer,
>that would be a quick solution, but then we're still stuck with the Bosch
>part... but it has been proven to work.
>I have a totally virgin NIB Bosch MAF, and I'll purchase a LT1 sensor, if
>the rest of us can come up with time on a flow bench, a translator, and the
>voltage to GPS table in the 89 165 code...
>Any takers?
>Tom
>
>----- Original Message -----
>From: "Bruce Plecan" <nacelp at bright.net>
>To: <gmecm at efi332.eng.ohio-state.edu>
>Sent: Sunday, January 16, 2000 8:27 AM
>Subject: Re: High Flow MAF revisited - (Porsche 928 voltage MAF)
>
>
>> Either sensor has the common trait, of not being linear.  Look at K
>Kelly's
>> chart.
>> There ain't no way some simple little V/F or F/V or combination there of
>is
>> going to do what you want, acurately.  One other option, rewrite the
code,
>> ya right, like that is easy.  Or use a Microprocessor, and do it right..
>> If some one who is really good with code had enough info., that would be
>> doable (and with a tad more work we could have a MAP to MAF or MAF to
MAP)
>> converter.  Now, the last option would be clever, IMHO.
>>   Grumpy
>
>