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Old 01-13-2005, 05:48 PM   #1
root
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Default Why not put the MAF in the throttle body?

Why not put the MAF in the throttle body and use it in combination with the MAP? You'd get better intake temp readings so you wouldn't have to worry about heat soaked intercoolers messing with things. And if you wanted an atmospheric BOV, you could use one since the air could be vented before hitting the MAF.
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Old 01-13-2005, 05:51 PM   #2
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The MAF is not designed for this. Part of the problem of the MAF design is that it is a hot-wire system, and any contamination on this will ruin the sensor.

Ever looked at the inside of your IC?
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Old 01-13-2005, 05:56 PM   #3
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Quote:
Originally Posted by Geek Guy
The MAF is not designed for this. Part of the problem of the MAF design is that it is a hot-wire system, and any contamination on this will ruin the sensor.

Ever looked at the inside of your IC?
What contamination? Is oil getting injected into the air via the turbo? I've looked in my IC but it seemed clean, course it is relatively new.
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Old 01-13-2005, 09:35 PM   #4
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MAF can't be after the turbo, air won't be accurate when under boost. Under WOT air flow in, and let go peddle air force other way out of bov. So only infont of turbo, constand air flow one way. But I think temp. reading after the IC is good idea.
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Old 01-13-2005, 09:44 PM   #5
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Hmmm... Good point. Although immediately after the throttle butterfly it should only ever go in one direction, yes? When you lift the throttle it would close the butterfly and cut off the MAF from the pressurized air to be vented. So maybe put it there? Although I guess the butterfly isn't going to close 100% or the engine would die.
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Old 01-14-2005, 07:28 AM   #6
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ive always wondered about this myself...

...especially after my IC charge pipe popped off numerous times, and killing my engine. if the MAF was in the TB, i wouldve been fine, just no boost.

i always figured the turbo must mess it up with compressing the air or something related to that. it would just be too easy that way.
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Old 01-14-2005, 07:29 AM   #7
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It'd just need to be recalibrated with a boost-based correction factor. Some aftermarket turbo kits have it there. Weird, but it can be done.
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Old 01-14-2005, 08:02 AM   #8
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Quote:
Originally Posted by SaabTuner
It'd just need to be recalibrated with a boost-based correction factor. Some aftermarket turbo kits have it there. Weird, but it can be done.
That's why I was saying to have the MAF in conjunction with the MAP. The ECU could alter the reading of the MAF based on the pressure read by the MAP. Or would it not be quite that simple?
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Old 01-14-2005, 10:18 AM   #9
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Air Mass does not change with boost, we use hotwire sensors all the time after turbo on many cars. Biggest problem is that the sensor will not read correctly because of the difference in the maf housing diameter itself which decides how much air gets sampled for measurement. The sensors are temp compensated so that will not be a problem unless the air temp gets over 250 or so. This could be made to work but the only benifit would be that you could vent the BOV to atmosphere and some improved spool up time
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Old 01-14-2005, 11:01 AM   #10
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Haven't the DSM guys been playing with post turbo MAF's? I have not been folowing thier results lately. But like what was said above the MAF (MASS air flow) does just that measures the MASS of the air not the volume. The thing I would be worried about is melting the sensor or tube if you run your compressor way out of the efficiency island.

TMS
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Old 01-14-2005, 11:50 AM   #11
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Quote:
Originally Posted by TheMadScientist
Haven't the DSM guys been playing with post turbo MAF's? I have not been folowing thier results lately. But like what was said above the MAF (MASS air flow) does just that measures the MASS of the air not the volume. The thing I would be worried about is melting the sensor or tube if you run your compressor way out of the efficiency island.

TMS
They have been fot a couple years now and with great success. They use something called a MAF translator. It uses a GM 3" or 3.5" MAF sensor hooked to a box with fuel controls. They work very well, decrease spool up and allow a BOV to vent to atmosphere. One problem with useing them on these cars though is there is not s sufficient place to mount them. DSM use them mounted in the upper intercooler pipe that goes from the IC to the TB. There is no such pipe on a wrx unless you have a FMIC. That would be a required upgrade for this system to work.

Do a search on dsmtuners.com or dsmtalk.com to find the company that makes them. They are actually a muscle car based company from Michigan I believe.
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Old 01-14-2005, 12:10 PM   #12
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Quote:
Originally Posted by subieworx
They have been fot a couple years now and with great success. They use something called a MAF translator. It uses a GM 3" or 3.5" MAF sensor hooked to a box with fuel controls. They work very well, decrease spool up and allow a BOV to vent to atmosphere. One problem with useing them on these cars though is there is not s sufficient place to mount them. DSM use them mounted in the upper intercooler pipe that goes from the IC to the TB. There is no such pipe on a wrx unless you have a FMIC. That would be a required upgrade for this system to work.

Do a search on dsmtuners.com or dsmtalk.com to find the company that makes them. They are actually a muscle car based company from Michigan I believe.
I can see putting the MAF between the turbo and IC. But again I would worry about it melting as the MAF would be right at the compressor outlet. This MAF translator thing does it just alter the MAF voltage. Or is the DSM MAF frequency based. If all you need is to offset the MAF voltage then you could do that with a Utec or Xede. This might be a good project for the summer if I ever get my car back.

TMS
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Old 01-14-2005, 12:23 PM   #13
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Quote:
Originally Posted by TheMadScientist
I can see putting the MAF between the turbo and IC. But again I would worry about it melting as the MAF would be right at the compressor outlet. This MAF translator thing does it just alter the MAF voltage. Or is the DSM MAF frequency based. If all you need is to offset the MAF voltage then you could do that with a Utec or Xede. This might be a good project for the summer if I ever get my car back.

TMS
Not exactly sure of the specifics of the thing. I know the translator just allows the DSM's to ditch their MAS and go witht he GM MAF.
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Old 01-14-2005, 02:07 PM   #14
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Quote:
Originally Posted by root
You'd get better intake temp readings so you wouldn't have to worry about heat soaked intercoolers messing with things.
The others have listed good reasons to keep the MAF pre-turbo. In a production car, the main thing would be oil contamination of the MAF. The MAF needs the air temp at the MAF sensor to calculate the air flow. Having an additional temp sensor post IC would allow the ECU to compensate for heat soak. Or you could just add a FMIC.
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Old 01-16-2005, 03:14 AM   #15
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I've tuned cars with the MAF translator on DSM's.. they run fine with it. But as for MAF sensors near the throttle body, i personally don't think it's a good idea. Airflow is not in one direction first of all and second the temps would be waaay off.
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Old 01-16-2005, 05:07 PM   #16
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how (and when) does air flow back out from the manifold through the tb?
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Old 01-16-2005, 05:31 PM   #17
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No i'm saying when the throttle plate closes, if it was before the plate or after, well either way i don't think it would be good for temps.
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Old 01-16-2005, 06:03 PM   #18
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Wouldn't it be better to know the temp at the throttle body as opposed to before the turbo? Aren't we more concerned with the temp of the air in the cylinder? Between the turbo and the intercooler, there are a lot of variables that alter the air temp after it was measured at the current MAF location.
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Old 01-16-2005, 06:07 PM   #19
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Yes but those same variables are the ones that make it hard (Depending on which system you use) to accurately tune.
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Old 01-18-2005, 03:43 PM   #20
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Quote:
Originally Posted by subieworx
They have been fot a couple years now and with great success. They use something called a MAF translator. It uses a GM 3" or 3.5" MAF sensor hooked to a box with fuel controls. They work very well, decrease spool up and allow a BOV to vent to atmosphere. One problem with useing them on these cars though is there is not s sufficient place to mount them. DSM use them mounted in the upper intercooler pipe that goes from the IC to the TB. There is no such pipe on a wrx unless you have a FMIC. That would be a required upgrade for this system to work.

Do a search on dsmtuners.com or dsmtalk.com to find the company that makes them. They are actually a muscle car based company from Michigan I believe.
You don't need to search far. We are the company that makes MAF Translator for the DSM's and many other cars. Full Throttle Speed, also a vendor here. We are working on a new much more powerful version that will work on the Subaru. We also make our Scanmaster scan tool for many cars including the Subaru version we just introduced here
Mike Licht
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