1jz single turbo, stock ecu, stock fuel?

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Thread: 1jz single turbo, stock ecu, stock fuel?

  1. #1
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    1jz single turbo, stock ecu, stock fuel?

    I have a 1JZ in my mk3, currently on the stock twins, only think done is front mount, 3 inch all the way back, and other little things. I would like to go small single and reach 350 whp. I would like to stay on stock injectors, stock ecu, and was thinking of getting something like a GT35 or a BW s257 or something around those sizes.

    So 10 psi on the twins is not going to be the same as 10 psi on a single, there will be more air coming in at 10 psi on the single at 10 psi vs the small twins. Because the 1jz are MAP, it goes by the pressure, so here's my question:

    1. Does the ecu only use the map as its only way to determine how much fuel to give?

    2. Because there will be more air coming in at 10 psi on the single, will the engine lean out a bit more? My guess is because it's still sensing only 10 psi on the single, it will give out the same amount of fuel as if it was 10 psi on the stock twins, but because 10 psi on the single will be getting more air, the engine will lean out because it's still giving the same amount of fuel, so it's not really compensating.

    3. Should I get a fuel cut defender, my boost cut is at around 13 psi and I'm sure I'd need to be at 13 psi or so to reach 350whp.

    4. How do you think the car will run if I do this?

    I've read people saying they've ran setups like what i am going for as long as i stay under boost cut. Most people get an AFC but i would like to avoid that route if possible. Also, I have a AEM wideband and boost gauge, since I know people will tell me to get that first.

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  3. #2
    I ran an HX35 and manual boost controller on a fully stock setup for a while without issue. Get a wideband to monitor. I don’t know how much the stock injectors can handle as far as hp though.

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    Quote Originally Posted by rhslol View Post
    I ran an HX35 and manual boost controller on a fully stock setup for a while without issue. Get a wideband to monitor. I don’t know how much the stock injectors can handle as far as hp though.
    Can you give me some more info? How much did you make on it or did you think you made? How much boost?

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    Quote Originally Posted by hernanhms View Post
    So 10 psi on the twins is not going to be the same as 10 psi on a single, there will be more air coming in at 10 psi on the single at 10 psi vs the small twins. Because the 1jz are MAP, it goes by the pressure, so here's my question:


    .
    this is not exactly what is going on. put 10 lbs pressure in your manifold, your motor eats the same amount of air. its the other variables ...

    a better compressor (or two VS one bigger compressor) is going to do two things:
    1. heat the air less as it compresses it to 10 lbs
    2. require less exhaust energy to spin fast enough to create 10lbs pressure


    its all about efficiency, thats why one turbo makes more power than another at same PSI. your stock twins might have x psi back pressure on the exhaust side @10lbs, while a s366 would have less exhaust back pressure at 10 psi ( and blow cooler air). if you can drive your car when its cold out (freezing) and not hit fuel cut you can likley run a single and stay off cut at similar psi. and make more power due to better exh side / efficient compressor
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  7. #5
    I was near boost cut, but remember it being hard to stay below boost when going wide open too quickly. Never had it dynoed so can’t give a good estimate of power. I wish i could give more concrete answers other than the engine will run fine on stock electronics.

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    Quote Originally Posted by madisonMK3 View Post
    Quote Originally Posted by hernanhms View Post
    So 10 psi on the twins is not going to be the same as 10 psi on a single, there will be more air coming in at 10 psi on the single at 10 psi vs the small twins. Because the 1jz are MAP, it goes by the pressure, so here's my question:


    .
    this is not exactly what is going on. put 10 lbs pressure in your manifold, your motor eats the same amount of air. its the other variables ...

    a better compressor (or two VS one bigger compressor) is going to do two things:
    1. heat the air less as it compresses it to 10 lbs
    2. require less exhaust energy to spin fast enough to create 10lbs pressure


    its all about efficiency, thats why one turbo makes more power than another at same PSI. your stock twins might have x psi back pressure on the exhaust side @10lbs, while a s366 would have less exhaust back pressure at 10 psi ( and blow cooler air). if you can drive your car when its cold out (freezing) and not hit fuel cut you can likley run a single and stay off cut at similar psi. and make more power due to better exh side / efficient compressor
    Quote Originally Posted by rhslol View Post
    I was near boost cut, but remember it being hard to stay below boost when going wide open too quickly. Never had it dynoed so can’t give a good estimate of power. I wish i could give more concrete answers other than the engine will run fine on stock electronics.
    You're right, I was a little confused about that and you just cleared it up. Regardless though do you believe the car will run just fine and won't lean out?

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    Quote Originally Posted by rhslol View Post
    I was near boost cut, but remember it being hard to stay below boost when going wide open too quickly. Never had it dynoed so can’t give a good estimate of power. I wish i could give more concrete answers other than the engine will run fine on stock electronics.
    I believe so too just want to get others to comfirm before I decide to do it since it's my daily. Do you think I should just get a fuel cut defender? I don't think it will be risky as long as I stay at the proper fuel power rangers.

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    I don't like FCD because if you accidentally over boost, good chance your going to go lean with the MAP signal clamped and way more air coming in (that the ecu does not see)

    A SAFC / piggy back tuning device to alter MAP signal paired with an adjustable fuel pressure reg would give you some headroom. crank the fuel pressure up and scale the map signal back

    do you have a wideband on the car ? who knows, you could be running pig rich at WOT (10:1 or more). if so there is already room to grow by just scaling the map signal back and getting closer to 11:1

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    You will not be able to hit 350whp on stock injectors. The injectors, ecu, and turbo all max out around the same point. Putting a bigger turbo on, doesn't change that the injectors max out around 300 whp.

    Also, a GT35 is not a small turbo haha

    Save up a little more, get injectors and an S-AFC. I personally wouldn't run much more than 350 with an S-AFC anyways.
    ProceeD!

  12. #10
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    I can attest to what he said. I have a 1JZ with stock twins and standalone ecu masters. Stock injectors is what kept me from moving above 307. Injectors hit 95% duty cycle which is basically almost static open which isn't good. Have ID 1050x injectors and radium fuel rail on its way in and will swap out to see how much I can get with the stock twins until I go to a big single. Planning no more than 18psi on them max. So I wouldn't waste the $$$ on getting a single turbo if you aren't swapping out the injectors among other things.
    New site www.supra-1jz.us replaces 1jz-gte.us

    Still own 92 Teal supra with 1JZ. Making 307whp on last dyno with 14psi stock twins.

  13. #11
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    For what it is worth, I made 320whp on only 12psi on my stock twins at SILV 2010. Ended up running about 15-16 psi later on, and it definitely felt closer to 350whp, maybe 360. This was through the stock airbox and intercooler even...

    That said, my head was ported, and I'm running 264 cams, so each situation will be different. 350whp is certainly possible, with the right degree of efficiency.

    To the OP, what do you intend to use the car for? If highway cruising / road tripping isn't a big part of your plans, a higher ratio rear end would likely make up for a perceived lack of power.
    -Brad
    87 Supra 1jz, monster in the making
    99 Miata DD, 46 Chevy Fleetmaster garage ornament

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