Re: Air Flow Meter vs Turbo

["Michel Drainville" <MDrainville@xxxxxxxxxxx>]

Ron, you're right by saying that Downing is using a different fuel pressure
regulator. In fact , they are using what is called a rising rate fuel
pressure regulator. It raises the pressure of fuel accoring to the pressure
of the intake manifold in a factor of 4:1 or so. Aftermaket ones have ratio
that can be adjusted as well. I'll have one in my installation, it is a
necessity.

What I meant, is if there is a need for more fuel, it's because there is
more air going in. You say that the ECU needs to be remaped for the new
volume of air coming in, but if that new volume can't be measured because
the flap is at it's maximum by 1psi of boost, what can be done?
This is my concern, since the AFM almost max out in NA form.

I know there is alot of engineering going into the development of a kit,
but that doesn't mean it can't be done at home. It's a question of using
common sense I think. Going slowly, monitoring AF ratio, injector duty
cycle, AFM signal, and the most important, knock.
Spending 50% of the value of the car on a Downing kit or 100% of the value
for a Mosselman turbo kit doesn't sound like a good move to me.
And buying stuff already made is not as fun as building it myself :-)

Michel Drainville






I'm no expert here, but I think that you are looking at this the wrong way.

You don't want to have the AFM put out twice the voltage for twice the air.

What you need to do is remap the engine computer so that it puts out the
necessary amount of fuel for the NEW amount of air that will be coming in
at
various AFM voltage readings.

According to Downing Atlanta:

http://www.downingatlanta.com/da_superchargers_info_new.htm

They are using a supercharger (not a turbo), and provide a different fuel
pressure regulator for boosted fuel enhancements.  There are alot of other
things they engineered to make this work properly.

Doing this on your own won't be possible.  There's alot of engineering that

goes into developing these systems.  Who knows, they may even trash a few
engines in the development process!  It'll be better in the long run (and
more cost-effective) to go with a proven kit, like Downing Atlanta.




Ron Buchalski
BMWCCA #76387
1995 E36 M3
1993 E34 525iT
1999 Mazda Miata







>
>Date: Thu, 24 Oct 2002 09:38:44 -0400
>From: "Michel Drainville" <MDrainville@domain.elided>
>Subject: Air Flow Meter vs Turbo
>
>To the Air Flow Meter experts on the list, and others,
>
>I'm in the process of installing a turbo on my M42 engine. It's not a kit,
>I'm doing it from scrath.  Before
>starting the installation, I decided to measure some signals to have a
>reference, before/after.
>
>This morning, I checked the AFM. With the engine stopped, I get a voltage
>ranging from 0.26 for a closed flap,
>and 4.89 for a completly opened flap.I then tried the car on the road. At
>idle it's around 1V, cruising is around 2.9 to 3V, and at WOT at 6300 RPM
I
>got 4.65Volts.
>
>I'm wondering what will happend when the turbo will push more air in.
Let's
>say I run at maximum 7.5 pound of
>boost, it's 50% more air, right?  By doing some reverse math, I figure
that
>to obtain 5volts, I only need to run
>at 1.xxx psi.
>
>Am I missing something?  The Downing Atlanta supercharger running 5-7 psi
>uses the stock AFM.  Also the turbo
>companies making kits for 318s and Z3 use the stock AFM, and pretty sure
>the stock chip also.
>
>So, is it because the AFM doesn't give a linear signal, toward the end of
>the movement of the flap, the spring
>tension is greater??
>
>Do I need to recalibrate my AFM? I hope not.
>
>
>Any help will be appreciated.
>
>Michel Drainville
>91 318ic (turbo... on day)


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