L8 APEKS

Hey gang,

I was just curious about this topic. I am finding TONS of vehicles that use MAF setups in all sorts of shapes and sizes, from 50 to 100mm.

So what makes the aftermarket 944 conversions cost $1000, when you can buy an MAF for 50 bucks?

What else would be involved (parts, labor, calibration?) in making a DIY MAF conversion? Does anyone know? This just seems like an easy junkyard project, or am I way off here? Help! Thanks!

L8 APEKS

BTW, this was specifically in regards to N/A cars.

But come on...say this can be done for, I dunno, 500 bucks. If it honestly nets the ~12hp I've heard about, that's not that bad. Cheaper than an exhaust system and better results!

Bueller?

adrial

You're paying for R&D...

You basically need a MAF sensor, chips and a piggyback.
Chips is the big question mark...they cost next to nothing if you can do them yourself but a few hundred $$ if you need someone to do it for you. Piggyback will be around $300-$400...more if you want something that comes with tech support for the 944/951...

You need the chips because the piggyback can only be used for small changes...whereas using a MAF in place of the AFM requires big changes.

Sam Lin

The sensor's flow vs voltage chart needs to be the same as stock, aka the "calibration." If you just plug in another, the voltages and resulting fuel lookup tables will be all wrong. That requires either a custom calibrated MAF (ideal choice) or a voltage massager ("Maf tuner") in line.

The best choice? Get Lindsey's Stage1 MAF and fit it yourself - they've gone through the hassles of getting a sensor custom calibrated so it's plug and play, you just need to plumb it, and no need to pay the money they're charging when you can do it for far less locally on your own. You'll be driving out the door for under $300 when all's said and done.

Sam

Bryan

A stock "flapper door" air flow meter sends two signals back to the ECU. The angle of the flapper door, and the temp of the incoming air. The ECU uses these two values to compute the mass or the incoming air.

An air mass meter sends one signal - the mass of the incoming air. So the ECU doesn't perform an air mass calculation.

To put a MAF in a car where the ECU is expecting the two signals from the flapper door air flow meter is therefore somewhat complicated. The easiest way would be to always present a constant temp signal via a fixed resistor, then alter the MAF output to match the range the ECU is expecting from the flapper door potentiometer. In theory, since the MAF automatically compensates for air temp, this would work. But it would take a while to get working and debug. And not having to hassle with it is worth $1000 to enough people to make it a viable business proposition.

Bryan

Matt H

Use temp sensor from stock AFM to overcome this problem. You can use a generic MAF (provided its flow is close), with an ARC 2. Anything can be done if you know enough about the DME/AFM and computers.
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Sam Lin

Lindsey's MAF has the temp sensor integrated as well, plug and play.

Sam

L8 APEKS

I found a universal kit from Split Second that includes:
A/F ratio meter
MAF sensor
MAF wire loom
Choice: ARC2 A/F ratio calibrator -or- programmable signal calculator (via laptop interface)
Instructions
Filter

Price is $737 (ARC; 4 adj. *****) or $855 (PSC; laptop programmable)

It seems to me that ALL of these items could be found for less, right? And as long as you were able to figure out the pinouts for any given MAF, aren't they all the same more or less? Would just about any MAF work?

Getting one from EBay for 50 bucks already saves you $200 off the price of their kit...their MAF's are $235 (3" round inlet) and $250 (3.5" flanged inlet).

So how cheaply can this be done, and what parts would you choose? Looking at their photo of the kit, there doesn't seem to be all that much involved. Maybe this is do-able?

Bryan

I might screw around with installing an air mass meter in my S2 engined 944 this summer, actually. I have a couple spare 928S4 air mass meters around, which it turns out are probably perfectly fine. So theoretically if I:

1. Measure the resistance of the (flapper door) air flow meter temp sender at, say, 70 degrees

2. Buy a resistor of this value

3. Use it to bridge the two pins of the ECU that get the air flow meter temp signal

4. Measure the resistance of the air flow meter flapper potentiometer when closed, then all the way open.

5. Power up an air mass meter on the workbench and blow some air through it and get a ballpark idea of the range of resistance it puts out.

6. Talk to some of my electronic whiz friends and see what it takes to convert the air mass meter resistance range to the air flow meter resistance range.

7. Breadboard it up.

8. Install it and rig up the air mass meter in place of the air flow meter

9. Try to start the car and drive it.

I'm not sure how well the 928S4 air mass meter will work since they're not accurate at small air flow rates and the smallest 928 engine that had an air mass meter was 4.7 liters. The S2 engine is 3 liters. So it might take 2000 rpm or so until the thing even starts working.

I'd like the S2 engine to have the razor sharp throttle the LH-jet 928s have, and I think you need an air mass meter to get it. Any more power is just gravy.

We'll see what happens.

Also, since the air mass meter automatically compensates for air temp, I don't think you want a variable temp signal coming in to the ECU as well. Hence the fixed value resistor.

I can then use different resistor values to shift the air mass value up and down until the engine runs perfectly.

In theory.

Radio Shack here I come.

Bryan

Bryan

Thinking more...

The assumption I am making is that the output of the air flow meter and air mass meter are both the same shape when graphed.

If you graphed the output of the afm from 100cfm airflow to 1000cfm airflow (just picking numbers at random here), is the air flow meter's output linear? What about the air mass meter? I bet they're not the same. And they would need to be for this to work. So I bet there's some non-trivial circuit design necessary to make this work, which is why there's not some simple method for doing this that everyone knows about, and instead very expensive kits for doing it.

Bryan

L8 APEKS

Well, expensive or not...I've still seen a HUGE variance in price!

$1500 vs $750 ?!

If there was a way to duplicate the Split Second package with used parts, you should theoretically be able to build that kit for $500.

Instead of their MAF, would a generic MAF from a Mustang work?

Instead of their A/F controller, would an Apex'i AFC or HKS AFR work?

Matt H

Arc2 - I can give you the name of someone who has a used one for sale.
MAF - it is a Maf for a Ford (that is why you need the converter plug), at least my Huntely one is from a Ford and SS was making those.
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L8 APEKS

Matt,

Thanks so much. So it seems maybe *ANY* old Ford MAF may even be what they are selling, since they are pretty universal? There are a bunch of 75mm units on EBay, all from 50-150 bucks.

As far as the ARC2...I would honestly rather use an Apex'i S-AFC if possible. It seems like it has more programmable points (every 500 rpm), where the ARC2 has only 3 generic settings via the ***** (low, mid, high range). Also, the S-AFC has a digital readout and push-button operation, which I prefer to the *****.

Do you think the S-AFC would work? It seems like it serves the same basic function.

If so...then this whole thing can be done for about 400-450 bucks.

Sam Lin

SAFC is FAR more powerful than the ARC2.

Sam

Matt H

I dont know about the S-AFC, not familiar enough.

I also dont know if ANY ford Maf will do, cheap as they are you might try two-three and sell the other.
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