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Discussion Starter #1 (Edited)
VPC vs Dual MAFs, now new MAF idea

The VPC vs dual AFM thread got me looking very carefully at the S-AFC instructions. Apprently you can tell it to use two AFMs, and to add the values before sending the signal to the ECU.

I kept looking and discovered something. Tell me if I am right or wrong. You can use a different kind of AFM, and the S-AFC will "translate" the signal back to the stock type for your ECU. You can set the input AFM type and output AFM type differently. Right? So you can use almost any type of AFM with the S-AFC, and it will still work if you set it correctly (set the IN as the AFM you choose, and the OUT as the stock style Pressure-1 sensor)?

Please don't tell me it's a bad idea, or ask why I'd want to use a AFM other than the stock MKIV one. Just want to know it it is doable. I'm planning something here.
 

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This sounds like a cool idea. If you find out that it works, let me know...
 
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Discussion Starter #3 (Edited)
I talked to Apex'i tech support and Powerhouse racing.

Apex'i: You cannot mix MAF types. But since I discovered that the stock MKIV MAF is a "hot-wire" type sensor, and the replacement sensor I had in mind is also a "hot-wire," I may still be in buisness.

Powerhouse: Said they tried this using large Ford hot-wire sensors, and couldn't get it working well. I have since discovered that Ford sensors have a voltage curve that is expotential in relation to airflow, where GM MAF sensors are linear. The GM sensor I had in mind can read up to 1000CFM of air as well (about 620RWHP with conservative estimates). If you want to pay more and get it customized, readings up to 1000HP are easy.

Some other reasons I like the GM LS1 MAF:

1. Cheap: $100 brand new
2. Placement: You can mount it as a blow-through, between the intercooler and throttle body. Been done before with great success. This also means a open blow off valve is fine, as the MAF will be placed after the blow off valve. This has been done on Grand Nationals as well as twin-turbo LS1 vehicles.


Right now I am waiting for a spec sheet on the MKIV MAF sensor. I already got the specs on the GM sensor. I should know by tomorrow if this will work.
 

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Let us know how this works out as I am very interested and this sounds like a very good solution if you can get it to function flawlessly in that location.

Adam
 

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AnArKey, I've thought about this as well, but since I'm only BPU I haven't had any reason to look into it further.

You say the MAF can be mounted after the turbos. Are you absolutely sure about this? It seems like oil from the turbo seals would coat the hot-wire over time (but then most turbo seals are probably in better condition than mine). I'm assuming you know that most temp sensors on MAFs don't respond quickly enough to a rise in temp from boost right?
 
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Discussion Starter #6
All I can speak of is this particular GM LS1 MAF sensor. It responds as fast as you can move the air and never had problems. If your turbos are puking oil, then maybe you should mount it before them. Either way works, but for open blow off valves right before the throttle body is nice.
 

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Thanks AnArKey, it really was about time someone looked into this. If it meters 620rwrhp, do you know how much it flows? ie the stock MAF can read 500rwhp, but becomes a small restriction around 400rwhp.
 
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Discussion Starter #8
Well from a purely visual standpoint, the GM 3" sensor flows MUCH better than the stock MKIV MAF. MUCH more flow area. Plus if you want, you can also get a 3.5" GM LS1 MAF, for the same price. That's for if you want to run it before the turbo like usual. You can even get a custom one in 4", with flow capacity and metering up to 1000HP for about $350-$400.

The 3" just fits better in front of the throttle body. For some reason, air flow restrictions make a huge difference on the intake side of the turbo, while on the pressure side it isn't that bad. Ever wonder why the intake to a big turbo is 4", but the output only 2.5"?
 

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AnArKey said:
For some reason, air flow restrictions make a huge difference on the intake side of the turbo, while on the pressure side it isn't that bad. Ever wonder why the intake to a big turbo is 4", but the output only 2.5"?
I think thats the same reason exhaust tips are larger than the rest of the piping - temperature. The hotter a gas gets the easier it flows. Of course higher pressure gas could flow better as well since the velocity is lower, I don't know.

If/when I go single, I'm probably going with a T78. I was considering a MAF bypass or dual MAF. I'd like to know how much power your car makes with this setup when its done.
 

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I was wondering why I've never seen a MAF infront of the TB before. Then it hit me - LS1s have a drive-by-wire throttle. We have a cable throttle and IAC valve, which needs to be connected to the intake after the MAF. Of course the PCV can be removed completely, so that doesn't matter. Does hurt the idle a little when you do that, I guess ajusting the throttle plate would fix it.
 
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