Maf Type?

Discussion in '1994 - 1995 Specific Tech' started by bayellowstang, Jan 14, 2014.

  1. Hi guys, it's been a while since I have been on here posting anything. I have been enjoying the car not being broke. Now I am getting ready to start a turbo install and have a few questions.

    Is there a way to tell if a MAF is a blow-thru? I have a PRO-M 80mm. It is just a big open hole with no sensor showing.

    My other question is are all aftermarket fuel pressure regulators boost referencing?
  2. its a draw thru
  3. If you tune with the wideband, it doesn't make a bit of difference which it is (blowthrough or drawthrough). I've been running a drawthrough ("regular") PRO-M MAF for several years now on my turbo '95 without any issues whatsoever. I think it only really matters if you're counting on its calibration to be spot-on for your injectors on a naturally aspirated combo. Since your turbo will need to be tuned, you can run whichever you want as a blowthrough (assuming that's what you're doing since it's the most common). I don't believe there's any physical difference between the two -- though you'll want to make sure your housing can handle the pressures you're looking to make. Probably zero concern at 10psi, the practical max for a stock-block.
  4. The only physical difference is that blow-through elements are designed specifically for the heat ranges associated with turbos or SCs.

    MAF elements operate by heat. As the air blows past the element, it varies the resistance of that element. That in turn, is read as a signal for the EEC to use in calculating how much air is flowing through the housing.

    Draw through elements tend to be more accurate at low throttle settings. The resolution of the meter is higher. I have seen what I consider to be exceptions. There are however, draw through style MAFs that can be "pegged" by the heat generated from a power adder. PRO-M and a few other manufacturers anticipate these kinds of conditions and leave enough room to handle the additional temps.

    Were it my build, I would buy a quality draw-through piece like jozefsz has done. The two key factors in a MAF for a street car are resolution, and consistency. Pro-M has a a great reputation for both. There are other vendors as well. Shop carefully.

    On the fuel regulator... I can't think of a single reason why it would need to be able to reference boost. Are you thinking of a Fuel Management Unit (FMU)?
  5. Thanks for the input guys. I figured it was a draw through. I think I am going to go with one of the new PMAS MAF's that has the IAT sensor built into it. That way I can kill 2 birds with one stone and not have to install the IAT sensor in the intake runner.

    As for the fuel regulator, everything I have been reading says that it should reference boost and add 1PSI of fuel for each PSI boost. I talked to the kit maufacture and he said the same thing. He also said the stock regulator will handle around 10# of boost and be good for 600hp so I may replace the aftermarket one I have with a new stock replacement. No need for adjustable anyways since I tune it myself.
  6. The integrated IAT's are nice, personally I like to keep it separate as those are known to fail (and a lot cheaper to replace as a separate unit). If you're installing a kit it probably has the IAT provisions already so you'll end up needing to plug it and also go with a different pigtail for the MAF itself. So that sounds like more hassle to me.

    You're right that all vacuum-operated fuel pressure regulators will "reference boost" to a degree. Noobz is right, that term usually doesn't mean too much outside of the FMU world. Theoretically however much boost you make will increase your pressure the same amount to overcome the resistance the fuel injectors now feel (and likewise when you're drawing vacuum decreasing the pressure at the rail). Took me a while to realize vacuum is inHG while boost is typically PSI, so up from 0 (at boost) you'll see 1:1, down from 0 (at vacuum) you'll see a smaller pressure decrease for each inHG of vacuum (but still 1:1 when using psi for both measures).

    Personally I'd get a good quality adjustable -- while the diaphragm in the stock unit can probably handle up to 10psi ok, I think it's a pretty weak little unit and if you pop the diaphragm at full boost you'll see a sudden drop in fuel pressure which could be catastrophic. You're right that you shouldn't ever need to use it (though I'm using it to cheat my injectors up a size by running a higher pressure at the rail which you could do too once you realize even 10psi isn't enough! -- FYI your signature says 30lb injectors, that's not going to be nearly enough for 10psi... I'm cheating my 36lb'ers Bosch 4-pin injectors up to 42 running at 55psi which is just about right for 10psi.).

    When you get around to tuning, you're welcomed to my tune. 42lb injectors, 10psi, PRO-M MAF, otherwise largely stock. You'll want to tune for up to 200% load and have full-boost AFR's in the high 10's or low 11's. And lots of other stuff you're welcomed to.
  7. Well I finally started it Saturday.

    I bought 60lb injectors for future use.

    I would love to look at your tune. I tuned it with the 30's and new heads and everything but I'm a little nervous tuning with boost. I have a 6lb spring in the wastegate, I don't want to risk breaking anything.

    I still need to get a boost gauge and some one way check valves for the evap can and the brake booster.

    Thanks for all the info.
  8. The first thing I would get is a wideband controller. At the end of the day, it's all about AFR's not fuel pressure. See here .
  9. Sent my tune to you for your inspection. :) There are a few areas to change a little bit for boost but it's nothing too bad at all.
  10. Along with the turbo I finally installed my LC-1 wideband too. I geuss I need to update my sig now. LOL
  11. i see no sig...
  12. HMM that's weird. I know I have one set up, I just edited it. I don't see it either.

    I need to get a pipe made to split the 3.5" into dual 2.5" pipes then to my cat back. I could probably not run mufflers as quiet as it is with just the down-pipe but it will be nice for it to be quieter.