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Blow through or draw through Mass Air Flow sensor location?

Discussion in 'The Blower Bistro' started by robert presti, Nov 15, 2018.

  1. robert presti

    robert presti Member Established Member

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    I have a car that was draw through at one time. Someone changed it to blow through, I have been working at getting it better. No luck there and thinking about trying to go back to a draw through MAF location. This is a built engine and long tube headers making over 12 psi with a D1SC. My issues are MAF add counts fluctuating 50-100 at near no throttle, and runaway idle with near stock IAC values.
     
  2. DSG2003Mach1

    DSG2003Mach1 Well-Known Member Premium Member Established Member

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    what car is it on?

    I wouldn't go back to draw through, blow through is better all around imho. Where is the maf located? It might just be in a bad spot.

    might just need a solid tune
     
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  3. Brutal Metal

    Brutal Metal Well-Known Member Established Member

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    ^ OR the MAF transfer curve is off in the tune. And yes you don't want the MAF location on a blow through setup at a bend in the piping.. Mine is 18 inches in front of the throttle body.
     
  4. blownstang4.6

    blownstang4.6 Active Member Established Member

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    For draw thru the maf is located between the filter and blower. For blow thru it should be located between the intercooler and throttle body preferably closer to the throttle body. You do not want to have a bend right in front of the maf. You have a very basic setup. If you're tuner know what they are doing either setup should work perfectly fine.
     
  5. robert presti

    robert presti Member Established Member

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    It is in the straightest shot between the front of the tire and the throttle body. A little over 10 inches straight before and after. What helped the wild MAF fluctuation a lot was increasing the blow off valve size. had a 20mm recirculating valve and then added a 50mm valve as well. As is the car can run pretty good with that kind of fluctuation, but the idle problems aren't satisfactory. The car in blow through has the IAC fed on the forced air side right now. Is there a check valve that should be in there? That is what I would do if in a draw through configuration to stop the boost leak only the other way around though, to use one to stop excess air from entering the IAC. So much of the IAC is tuned out to prevent the run away idle that the car has problems cold and I live where there are massive swings in temperatures. My friend has a draw through 2 valve mustang that made 540 rwhp and he is draw through and never had any idle or stalling issues. My car made 600 at 6300 and they thought it would have been 670 at 7000 or so but didn't have the fuel pumps to support . Draw through at that time and the air temperature function moved from the MAF to a separate sensor, which seems to be the major reason they try to push blow through.
     
  6. 1996MysticSnake

    1996MysticSnake Active Member Established Member

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    What bov do you have and what spring is in it?

    Sent from my Pixel 3 XL using Tapatalk
     
  7. robert presti

    robert presti Member Established Member

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    TIAL Q 2psi after the intercooler maybe 1.5- 2 feet from the MAF.
     
  8. old01cobra

    old01cobra Member Established Member

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    That's your issue right there. The BOV needs to be between the Blower and the intercooler. Having a BOV that close to the MAF will definitely affect readings. I put mine as close to the blower as possible. Another perk is why run hot compressed air through your intercooler and vent it... Its like a preglow system for you intercooler lol always keeping it preheated. Keeps intake temps down also when its vented prior to the intercooler..
     
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  9. 1996MysticSnake

    1996MysticSnake Active Member Established Member

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    Yep agreed my tial q is right before my intercooler.

    Make sure you have the pink supercharger spring in it.

    Sent from my Pixel 3 XL using Tapatalk
     
  10. robert presti

    robert presti Member Established Member

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    Today I did some work to the super charger pipes. I put the recirculating/ blow off valve in front of the intercooler instead of after and I can't believe how well this car ran today... though that was not the only change, but I think the one that has it running and driving somewhat like a bone stock Mustang. No tune change yet . The only thing is the vent to atmosphere valve is super loud now. Not sure how much of that has to do with it now being on the drivers side vs the passenger side, or if the intercooler helped somehow with that. At the moment I'm glad I tried this rather than reverting to draw through for the MAF.
     
    Last edited: Jun 22, 2019
  11. old01cobra

    old01cobra Member Established Member

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    Yup its normal... My tial makes the cobra hiss down low and between the shifts and on down shifts LOL. The way a cobra actually sounds. So fitting. Its completely normal your venting the supercharger to atmosphere threw a controlled leak in the charge piping she's going to be noisy.... Glad you got her running right now go get it tuned before rainy season turns into snow its apparent we are not going to have a summer in the Midwest this year.
     
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  12. slo984now

    slo984now AKA 01yellerCobra Established Member

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    My Tial 50mm was tucked in the fender well behind the fog light. It was really loud, but I liked it. I had people changing lanes and rolling up windows on the freeway. And if someone pissed me off I'd build a couple pounds of boost and when I got next to them let off the gas so it would dump next to their window. It was funny to watch them jump.
     
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  13. robert presti

    robert presti Member Established Member

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    That's where mine is and it is fun at times and at others not with a stick shift. I have to go way out of my way to keep it quiet and it is a sound here people aren't used to.
     
  14. robert presti

    robert presti Member Established Member

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    I did so me research on that and many thought having it after would be better for power. And what made sense there was probably killing my drivability There might be a slight edge in all out racing having the blow off valve after the intercooler, but in my opinion and experience no gain would be worth the trade off if you drive the car any where other WOT all the time.
     
  15. robert presti

    robert presti Member Established Member

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    So after changing the pipes and location of the recirculating/ blow off valve to pre intercooler I now have a MAF add count variation of around 10 max. Going back to the start we see 100 max. Could a real tuner have made this car run good with the mechanical short comings in the set up? I don't think so . Better than I could maybe ... If we build our car right they will just be better in so many ways vs tuning work a rounds.
     
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