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Thread: DOHC swap

  1. #1
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    DOHC swap

    Ok guys i have started gathering parts for my swap. My question is since the early sc's have 30 lb injectors can i use the MAF off of an sc since the injectors on my motor are 30 LB injectors. Would this eliminate needing to order a custom MAF ?

    Thanks
    Lee

  2. #2
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    you gonna get two more 30's to go in the DOHC? I think you'll need a computer for it and then a tune. The DOHC's had 19's or 24's if I recall.
    Scott Long
    1992 SC 5-speed
    Black on black leather, lowered, 18x9 Chrome Saleens...

  3. #3
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    Doesn't matter, Lee. You STILL need to get it tuned. Unless you leave the factory injectors and use the factory MAF.

    That "calibrated MAF" noise? It avoids a tune, but it can cause other problems down the road, since so much of what the computer does outside of WOT/open loop kind of depends on "OK, we're flowing 437 CF/min of air, that's going to take 75% duty cycle, and I need to advance timing 20 degrees, and ... " and using a calibrated MAF can screw the rest of it up.

    RwP

  4. #4
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    Maf

    The cobra motor that is going in the car already has 30 lb injectors 8 of them. Can i use an early model SC stock MAF since the early sc had 30 lb injectors ? This motor will be controlled by a 94 4.6 pcm with a flash from blue oval performance. Thats why i wanna know if i use the MAF off the early model SC can i just have the pcm flashed to that MAF and be good to go.

    Thanks
    Lee

  5. #5
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    I'm no expert but it seems to me that the stock 55mm maf would be very restrictive on a V8. Having said that I await the lessons from the more informed members.

  6. #6
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    I was thinking the same thing. Why not let it breath and put a proper sized MAF on it? If it will need a tune anyways why bother with a stock 55mm or 70mm SC MAF? Put at least a 76mm MAF on it.

    Its gonna need all the help it can get to get that car moving. No torque having 4.6L DOHC..... (I know they make between 285-300 ft lbs but those engines are slugs down low even in lighter Mustang Cobras. Why do you think people put 4.56 gears in the damn things?) They do pull well above 4000 rpms though.
    Last edited by Scott Long; 01-20-2013 at 05:23 PM.
    Scott Long
    1992 SC 5-speed
    Black on black leather, lowered, 18x9 Chrome Saleens...

  7. #7
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    Stock Injector size on the DOHC is 24# injectors - good up to 350HP on a naturally aspirated setup.

    You can use ANY MAF .. as long as its calibrated to the PCM, but the stock 89-93 SC MAF is sort of small, smaller than the 94/95 - the MAF isnt tuned to the injectors, the PCM is tuned for the MAF and the Injector size. You need a tune regardless.

    According to the FRPP technical article on properly sizing fuel system components ..

    You should be using 42# injectors for applications up to 465 HP on a roots supercharged setup - this is at 90% Duty cycle. The 94/95 SC uses 36# injectors stock - so 30# on a DOHC with a SC isnt the most ideal setup. Difference being 8 injectors vs. 6 .. but you definately need more fuel supply.

    Fuel pump needs to be at least 155 lph on a setup making at least 440 HP on a NA setup - forced induction is going ot be decreased, depending on how much PSI the SC boots at, a 255 LPH at 40 PSI may only supply 200 LPH at 58 PSI fuel rail pressure ( 40# + 18# boost - again depends how much boost youre making, but forced induction requires more fuel supply from the pump )

    MAF sizes - if the 89-93 SC is a 55mm MAF for up to 275 HP level, the 94/95 with the 70mm MAF is good up to 350 HP .. the 80mm MAF like off a Mustang GT is good for 425 HP - so if youre making more than that you might need to step up to the 90mm MAF like off a Lightning which supports up to 540 HP.


    - Dan
    Last edited by Ddubb; 01-20-2013 at 05:27 PM.

  8. #8
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    You have to use a MAF capable of handling the HP level you hope to achieve. I suggest an 03 Cobra or Lightning MAF.

    No Ford MAF is calibrated to any injector size. They are all calibrated for a set maximum airflow.
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  9. #9
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    Quote Originally Posted by Ddubb View Post
    MAF sizes - if the 89-93 SC is a 55mm MAF for up to 275 HP level, the 94/95 with the 70mm MAF is good up to 350 HP .. the 80mm MAF like off a Mustang GT is good for 425 HP - so if youre making more than that you might need to step up to the 90mm MAF like off a Lightning which supports up to 540 HP.


    - Dan
    Pretty sure it was 92+ that had 70mm MAF. But still even if he is running it n/a it would be around 300 hp engine at the crank so he will need bigger than 55mm MAF. If it has 30's in it the fuel should be good but I'd go with at least a 76mm MAF. Like Dave said though a Lightning MAF is a good choice and they are even cheaper you can get them for like $75 since they are plastic.

    http://www.ebay.com/itm/2001-04-F-15...c2ed33&vxp=mtr

    adapter:
    http://www.superchargersonline.com/i...480d610993ff46
    Last edited by Scott Long; 01-20-2013 at 05:30 PM.
    Scott Long
    1992 SC 5-speed
    Black on black leather, lowered, 18x9 Chrome Saleens...

  10. #10
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    Maf

    Ok i got it. I was just talkin about the sensor itself but if the MAF will be taken care of with the PCM cal than im not gonna worry about it. Ill just pick one up off a cobra and flash the PCM to match. According to the chart here http://oldfuelinjection.com/?p=38
    the 30 lbs are good to 61 horse per cylinder or 490 HP. I wont have that much power im thinkin with the M90 thats on it it will probably boost about 10-12 psi so i think ill be around like 400 crank horse power. Im not tryin to argue with anyone just tryin to get an understanding so its all in order when i start this project.

    thanks Scott thats awesome. Im gonna order those now.

    Thanks
    Lee
    Last edited by Lee Billing; 01-20-2013 at 05:38 PM.

  11. #11
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    The Sensor inside the MAF is calibrated to the MAF housing - you cant just swap the sensor, you need the correct sensor + MAF housing combination.

    The fuel injector sizes on that website you referenced are for a NA setup .. when you supercharge the engine you basically double the volumetric efficiency of the engine requiring larger injector sizes than you would with a non supercharged setup.


    - Dan

  12. #12
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    get a ford 90mm MAF. Get computer flashed for that. It will work for you and not be a restriction
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  13. #13
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    Quote Originally Posted by Lee Billing View Post
    Ok i got it. I was just talkin about the sensor itself but if the MAF will be taken care of with the PCM cal than im not gonna worry about it. Ill just pick one up off a cobra and flash the PCM to match. According to the chart here http://oldfuelinjection.com/?p=38
    the 30 lbs are good to 61 horse per cylinder or 490 HP. I wont have that much power im thinkin with the M90 thats on it it will probably boost about 10-12 psi so i think ill be around like 400 crank horse power. Im not tryin to argue with anyone just tryin to get an understanding so its all in order when i start this project.

    thanks Scott thats awesome. Im gonna order those now.

    Thanks
    Lee
    Those are the best prices I've found on MAF's. I just got an 80mm C&L or I would have bought one of those.

    I didn't realize you were supercharging it. Are you making a custom manifold or how is the M90 mounted to the DOHC?
    Scott Long
    1992 SC 5-speed
    Black on black leather, lowered, 18x9 Chrome Saleens...

  14. #14
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    Maf

    Check out this thread.
    http://www.sccoa.com/forums/showthread.php?t=128525

    I was gonna sell it until a few of the guys here talked me into puttin it in my 94 SC. I found a 80 MM MAF on ebay for 40 bucks so i picked that one up. It is used but im tryin to save a little money and not break the bank on this project. the trans on the engine i thought was a t45 but with further inspection it is a tr3650 which is superior to the t45.

    Thanks
    Lee

  15. #15
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    Oh yeah I remember seeing it listed for sale. Glad you are going to keep it. Once you get it in and running, then you can port the blower and overdrive it. I'll be interested to see the finished product. Should be sweet. Are you going to put the manual in there?

    $40 for an 80mm MAF is a hell of a deal.
    Scott Long
    1992 SC 5-speed
    Black on black leather, lowered, 18x9 Chrome Saleens...

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