Developing an Inexpensive MAF system.

perfecto951 · 02-25-2004, 08:05 AM

So we just sent away for a LABjack data acquisition device, it should be here by this weekend. I’m kind of irked about the price of MAF packages (Sometimes going over 2K). My friend and I have decided to make a MAF setup for my 951.

Another friend who has a 3rd gen RX-7, just got a NA Z32 parts car. We are going to strip it of anything we could use on my pal’s 300zxTT, and I’m going to take the MAF sensor.

So we are going to measure the voltages the stock AFM gives out, and compare them to the voltages the Nissan MAF gives out. The my friend is going to write a temporary program that we can use on his notebook, it will just process the voltages from the Nissan part and send a translated version of those voltages to the DME. Once we get the software working right we are going to make a hardware box version that translates just like software.

Piping and filters won’t be a huge problem, I know a guy in town that does pipe bending and he should be able to weld all bungs on for the vacuum lines.

Basically what I want to get out of this is a little more throttle response, because I’m honestly not satisfied with the way it responds right now. We may or may not get much horsepower out of this.

I’m sure we are going to run into 1000 problems, but I don’t see why it shouldn’t work. My only worry is the air temperature sensor; I don’t think that Nissan MAF has a sensor. The best I can figure is to trick the DME into thinking its one temperature (i.e. 72^) all the time. I’ve heard that the air temperature sensor is for a smooth start, which isn’t necessary – I wouldn’t think.

If anyone has any ideas, please let me know. There probably plenty I’m not thinking about. If you have any links or other resources let me know too. This should take us a few weeks, but I will keep everyone posted as we make progress. If everything works out, and we can make a stable product, you’d better believe it will be offered for a considerable amount less than other MAF systems…..and pelican part members will, of course get a discount!

Wish us luck.

ae1969 · 02-25-2004, 08:23 AM

Why bother using a used MAF....

If you want cheap there are a few alternatives.... Ford brand new MAFs are cheap. Also PRO-M makes some that are pretty cheap and can at least give you some idea on sizing.....

Ideally you want the temp sensor on the MAF as well. I guess if you dont have variances in cold start temps you may be able to get away with the 'fooling' trick....

You have to figure out what you want at the end? If you want a larger turbo later on this MAF you rig will probably be useless. The idea is to size the MAF to your turbo..

jp944 · 02-25-2004, 08:26 AM

I have a used ARC2 that I'll be selling in a week or two, if you're interested.

jp

perfecto951 · 02-25-2004, 09:13 AM

Quote:

Originally posted by ae1969
Why bother using a used MAF....

If you want cheap there are a few alternatives.... Ford brand new MAFs are cheap. Also PRO-M makes some that are pretty cheap and can at least give you some idea on sizing.....

Well, the point of using this Nissan one is because it's free. And we don't exactly have the capitol to buy a properly sized MAF. If we could even get it to work then that would be something to look into for sure.

Zero10 · 02-25-2004, 09:03 PM

I would definately be interested in hearing about this.
The air temperature sensor is not just used for starts. It is used all the time while the engine runs, to determine the air density.
perhaps it would be possible to wire in an air temperature sensor, perhaps from the original AFM? I don't think that would be too hard.
You are probaby going to run into 2 things. The values for the AFM will probably be different, and the scale will probably be different. You will need to take quite a few measurements to determine the exact conversions.
Another thing to consider, is a MAF has a hot wire sensor, right? So you will probably need to power the hot wire some way, perhaps just a switched +12V from the ignition?
Take some time and investigate this entire project.
If the sizing of the nissan MAF is completely wrong, then this is not worth doing, it will produce more problems than it could possibly solve.
However, if the MAF is the right size/oversize, then it will probably be alright. The piping should be the easy part.
Best of luck to you on the project.

perfecto951 · 02-26-2004, 05:09 AM

wow. thanks!
i didn't even think about taking the sensor from the original AFM. i just need to find it, take it out and stick it behind the nissan MAF. I figure the nissan part should be perfect, if anything it will be oversized. Those MAFs are good up to like 600hp....after that they run a dual MAF setup and divide the value by two.

I'll probably end up forking over the cash for a properly sized one if that doesn't work out.

Does anybody have a link to PRO-M's site?

SoCal Driver · SoCal Driver's Garage

Make sure the temp sensor is before the MAF's heated element in the air flow.

perfecto951 · 02-26-2004, 11:14 AM

I didn't even think of that. i had no idea the hotwire was actually hot! keep the comments coming, you guys have helped me out an immense ammont already!

SoCal Driver · SoCal Driver's Garage

IIRC MAF's use a venturi to meter the air flow across the heated element. The design of the venturi cross section must relate to the volume and intake air flow for the engine it's used on.

Then maybe it's all done with mirrors.

Mirrors.... hmmm....

fast924S · fast924S's Garage

If I where you try to come up with some type of could air intake when you bend the tubing, That would be sweet. The only other problem I see is 1 without the ATS (air temp sensor) You may be running rich or lean all the time. Also with the less restrictive MAF setup ur gonna have to get more fuel inot the engine to take advantage of this, When I converted to a HUNTLEY RACING stage 2 MAF kit I had to bump up the fuel pressure and adjust fuel injecter pules to get everything just right, If you need to know what wires I jumped into let me know I will take a look at my car for u.

fast924S · fast924S's Garage

Also it will help you tune your kit if you can get your hands on a A/F sensor, Or just take a look at the voltage output of the 02 sensor

perfecto951 · 02-27-2004, 10:43 AM

yeah. i already have a larger FPR, and i figure the stock injectors should be able to supply enough fuel for a basic maf setup.

does anybody have any information on the stock temprature sensor in the AFM? If i can find a sensor with the same tolerances and sensitivity then that may also work. i know where i can get a 924 AFM, think it's the same sensor?

Zero10 · 02-27-2004, 05:14 PM

Erm... Probably not the same sensor, althought I could be wrong.
One's an audi engine, the other's a porsche. So one is audi electronics, the other porsche. Either way the sensor itself is probably bosch, but will probably have different sensitivity or resistance.

Good point about the hot wire. I don't know how much it heats the air, but I bet the temp sensor would pick it up.
I think the adjustable FPR would be sufficient to supply enough fuel for the increased air flow. It's not like it's a stroker kit or something.

I suppose I could take a couple measurements on my sensor, although I could only check it at 2 or 3 temperatures for you (it's off the car right now, so throw it in the fridge, inside, etc...)
Unless somebody else has the numbers handy.
I don't know exactly how to check it, but I don't think it's too complicated.

350HP951 · 02-28-2004, 05:39 AM

It can be done for about 550 dollars with new parts. Question is why bother, you can buy used MAF kits for that much money all day and they come with proper software, etc.

You need:
MAF Sensor
J-pipe
Fuel Controller (ARC-2 is fine)
AIT

That is pretty much all you need.
If you want to buy one, I have a MAF setup I might be willing to part with.