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Thread: My twin supercharged tbi 350 miata build

  1. #1
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    My twin supercharged tbi 350 miata build

    let me catch everyone up on this.

    over the past 2 years, i had been swapping a chevy 350 into a mazda miata [funds held me back, but eventually i got it done]..... caught fire in the process but it didn't stop me. i blew the engine up at the racetrack, rebuilt it, and now were are back in action with a different chassis.

    SO, after slight research and talking with Dave W; i am going to be building a twin eaton m90 [thunderbird supercoupe superchargers] tbi chevy 350. The plans are to port them and if calculated correctly; should run about 18PSI. i will be running a single 2in-1out intercooler, a methonal/water injection system when the car hits boost, and e85 to TRY to prevent detonation on a 10:1 engine. chevy 350's are a dime a dozen at my pic-a-part....... so, if it blows, just gonna keep trying until we get it straightened out.

    ill be running a 454 throttle body with 454 injectors, i am also running a twin belt setup..... v-belt for crank, waterpump, and power steering; then a 5-rib belt found on early vans for the alternator, waterpump, crank, and both superchargers...... i have 2 timing belt idlers from my miata that i am using for the non-ribbed side as idlers to get the belt to go where i want, then im using a tensioner somehow to obviously put tension on the belt. the superchargers have 8 rib pulleys, but the 5 rib belt fits right over them no probelm.

    the engine itself is a GMPP crate 350/285-300hp...... i slapped vortec heads on during the rebuild and the shortblock is the exact same as the GMPP crate 350/330hp, so theoretically it should be the GMPP crate 350/330hp now. It's an 880 block with 4 bolt main and 1 piece RMS. The car already blows off the tires through 4th gear, but still, power is power :D time to grab some slicks lol.

    The trans is a bone stock WC t5 from a v6-fbody. it's held up so far, no issues...... stock 10.5in clutch.

    rear end is a stock miata 4.10 [7inch ring gear]...... it will be upgraded to a 2.8 thunderbird IRS rear with factory five racing axles, however, im going to have to relocate my lower shock mount for the axles to fit.

    custom driveshaft.
    custom TBI wiring.... re-worked my harness on here awhile back
    PCM - 16196395 - pretty sure dave and i talked about this computer being capable of boost...... can someone please clarify?

    there is a LONG road ahead, but it will all be worth it. I am shooting for 450whp.

    this is my car after 2 years













    but i needed to get something safer, so i am building a different chassis with a roll cage; just in case.

    in the meantime. enjoy
    https://www.youtube.com/watch?v=4ZvIvqdXKoI

    https://www.youtube.com/watch?v=XDSE2km69F8






    I started building and eventually finished the trans tunnel...... don't hate on the flux core welder haha. It does the job, just ALOT of cleanup.















    I also tac welded plates in the driver compartment on the firewall to patch the wholes that I won't be using.





    far from perfect, but far from bad too. think im done with the underside..... i know there's imperfections but its good enough for now.... i can always give it some love later on.

    Last edited by Shawn1989; 02-22-2015 at 09:14 PM.

  2. #2
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    Man that's going to be a sweet build!! Great work so far, that's going to be a fun little toy. Just be careful with slicks on the rear axle...you prob already know but that thing will be a grenade waiting to go off when it starts hooking up. I've been through a few on my toy, lol. I love the E-85 for high octane also, that's what mine is running on. Just watch your tuning different times of the season as if you buy it at the fuel pumps it changes actual alcohol percent with season changes of the year so some tuning for different times of the year will be required especially with forced induction. My toy runs on a carb though with nitrous so it might be a hair more sensitive to change that superchargers. Just make sure you get the tensioner set tight with the 5 rib belt so they don't spin on ya under boost. Can't wait to see how it turns out

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    God gave me a gift at the junkyard today.






    now I just need 1 more lol

    oh yeah dave, there is a vacuum bypass on the inlet of the blower
    Last edited by Shawn1989; 02-23-2015 at 05:38 PM.

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    Grabbed the handy dandy angle grinder and cut some square tubing to make a tensioner bracket; then drilled some holes for the tensioner to fit. Came out pretty good.

    Going to weld a nut on the backside to hold it all together.


    As for mounting it, I'm going to weld it to the sbc adjustable alternator bracket. Shouldn't be an issue because the audi alternator I'm using is fixed; so that bracket is just there for support of the alternator and idler.
    Last edited by Shawn1989; 02-24-2015 at 03:53 PM.

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    Ran to Home Depot to grab a piece of stock so I can start making mounts for the chargers.
    Hooked it up in the vice and began bending..... The result:






    I still need to drill holes where it sits on the exhaust manifold.



    After that I grabbed an old miata front sway bar; chopped the ends off and they fit perfectly on the heads.









    Then I grabbed 1/4 steel and began chopping what the Chargers will actually sit on..... I need to make a duplicate:



    For now, that's it; there should be an update tonight. Got a few gussets to cut and quite a few holes to drill, then I need to start lining everything up and tac/welding everything together.


    I also am going to make a plate that will mount to 2 bolts on each of the Chargers snouts to hold them together

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    keep updating.nice work

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    Well I got one side pretty much done and I started on the other side.

    Last edited by Shawn1989; 02-25-2015 at 07:12 PM.

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    Going a different route on the belt setup.
    I will be running 3 belts instead of 2; I need to pick up another tensioner.



    Bondo, seam sealer, and paint for the next week.




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    very crazy, very cool. keep up the good work.

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    Nice work so far. Looks like it's going to be a little screamer.

    Years ago I rode in a car with twin Ford 3.8 superchargers and it was amazing. Not for speed, not for power, but for the noise! Those twin chargers screamed. The owner said he had trouble picking up races because people could hear the twins making noise and just didn't want to try. Well, he didn't actually say it, he shouted it to me as we cruised down the street. It was a fun car though and at the time it was a great representation of what a DIY guy could do with efi and some used parts.

    It took a bit to dig up a photo. The builder is Bob Ward. The photo is from around '99 or '00.

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    It's funny how you bring him up. i was searching literally for a month trying to find him. LUCKILY i got ahold of him on thirdgen and found him on asphault playground. He is informing me that i should ditch the twins and just find a single m112 or m122.

    I am still going to do the m90's just due to the fact of it looks awesome...... hopefully dave can get it running flawless; if so, im going to throw the whole engine, pcm and twin supercharger setup on craigslist and try to get an ls1 out of it.
    I just have no idea what i should ask for it....... yes, it will be cleaned up and painted.

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    I believe Bob used the 7749 and $58 from the Syclone / turbo Sunbird. It's workable code but some people have found it takes a bunch of time to get some of the transitions worked out such as switching from decel to accel. Even if the car wasn't that fast, it had a cool factor that's tough to match. I agree that a single, properly sized SC might be more fun and easier to tune.

    Regardless, you're going to have a cool car when done.

    You might also want to check out a turbocharged TBI Cavalier that used to be on v6z24.org. Username was 1redry. Car was built (IIRC) without an ecm that was boost specific. IIRC he made decent HP numbers for a mild car.

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    Quote Originally Posted by 1project2many View Post
    I believe Bob used the 7749 and $58 from the Syclone / turbo Sunbird. It's workable code but some people have found it takes a bunch of time to get some of the transitions worked out such as switching from decel to accel. Even if the car wasn't that fast, it had a cool factor that's tough to match. I agree that a single, properly sized SC might be more fun and easier to tune.
    Yeah, i have no clue about the computer stuff. I can wire it all up but when it comes to tuning, i'm at a loss, hence why Dave is in the picture.
    I am running a 16196395 PCM that was previously tuned by eagle mark. Unfortunately, he can't guide me anymore. I don't see how a single supercharger will be any different than twins..... turbo's most definately, but superchargers are belt driven so a projected RPM will be the same every single time [single or twins] rather than a turbo which will fluctuate.

    Quote Originally Posted by 1project2many View Post
    Regardless, you're going to have a cool car when done.
    I sure hope so! :D

    Quote Originally Posted by 1project2many View Post
    You might also want to check out a turbocharged TBI Cavalier that used to be on v6z24.org. Username was 1redry. Car was built (IIRC) without an ecm that was boost specific. IIRC he made decent HP numbers for a mild car.
    I'll see if i can get ahold of him. Thanks for the info.
    With you saying without an ecm which was boost specific, do you mean that he just has a timing box, and a 2:1 FPR controlling it?

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    I don't see how a single supercharger will be any different than twins.....
    Heat! More heat. And the noise, noise, noise, noise! Like my Grinch impersonation? :)


    With you saying without an ecm which was boost specific, do you mean that he just has a timing box, and a 2:1 FPR controlling it?
    I don't remember what he had for additional controls. But the ecm had stock programming so something had to be adjusted.

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    Quote Originally Posted by 1project2many View Post
    Heat! More heat. And the noise, noise, noise, noise! Like my Grinch impersonation? :)
    lol well i knew that, it's going to be intercooled with water/meth so i don't think heat will really matter that much.... As for the noise, the more, the marrier! Haha the more it screams, the more it intimidates :]
    Yeah, first thing i thought of was the grinch lol.

    But, i was talking about how the tuning would be different from twins vs single


    Quote Originally Posted by 1project2many View Post
    I don't remember what he had for additional controls. But the ecm had stock programming so something had to be adjusted.
    Ok well i just emailed him because he hasn't been on v6z24 since October of 2014, so; my fingers are crossed.

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