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  1. #1

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    Question for all you turbo guys

    What model/size turbo comes with the kit, or what are you using? I have been curious about this for some time, other than the added heat, and cooling of the charger, this should be fairly trivial since the motor is already designed for forced induction. The fuel system is already in place, and the engine is already running forged low compression pistons. The OEM ECU does use a boost comp map correct? IE it calculates fuel requirement on the fly based on manifold boost pressure, correct? I saw this discussed before, but never found an answer, did anyone ever find out any specifics on the maximium boost level where the fuel table ends on an OEM RXP ECU? I would imagine you could see 300hp with somewhere around 15lbs of boost, being that a turbocharger is inherently more efficient. Taking into effect the free HP gain from no longer having to turn the SC. Once you swap to a turbo, this engine would probably benefit nicely from a lighted single gear flywheel, as I imagine a dramatic weight savings is possible there.

    Kinda got off track there, but I was just curious what size, and or make/model turbo is being used on the 4tec turbo setups? Thanks.
    Last edited by boostaholic; 11-20-2007 at 09:16 AM.


  2. #2

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    Quote Originally Posted by boostaholic View Post
    What model/size turbo comes with the kit, or what are you using? I have been curious about this for some time, other than the added heat, and cooling of the charger, this should be fairly trivial since the motor is already designed for forced induction. The fuel system is already in place, and the engine is already running forged low compression pistons. The OEM ECU does use a boost comp map correct? IE it calculates fuel requirement on the fly based on manifold boost pressure, correct? I saw this discussed before, but never found an answer, did anyone ever find out any specifics on the maximium boost level where the fuel table ends on an OEM RXP ECU? I would imagine you could see 300hp with somewhere around 15lbs of boost, being that a turbocharger is inherently more efficient. Taking into effect the free HP gain from no longer having to turn the SC. Once you swap to a turbo, this engine would probably benefit nicely from a lighted single gear flywheel, as I imagine a dramatic weight savings is possible there.

    Kinda got off track there, but I was just curious what size, and or make/model turbo is being used on the 4tec turbo setups? Thanks.
    this is a turbo kit which has been developed and tried and tested by seadoo riders of this forum, i myself wanted to know the turbo type and model number, but it has to have the manifold, and i guess you know
    the cooling, so post your mods lets see were your up to, regards bill

  3. #3
    ctriverguy's Avatar
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    Hi, from one of jerries posts, the turbo is a garrett gt28... something. the boost range from what i have read can be adjusted up to about 30 psi. From what these guys have said, you the turbo really comes to life about 20psi. There is a difference of opinion, on what is safe to run for a stock motor, jerri wants to keep his ski about 19-21 psi this is with the riva ecu and 50# injectors. Others have said 24-25 is safe. but at this boost, based on the previous threads, the air/fuel ratio runs lean and requires 55# injectors. There are aftermarket low compression pistons and the mention of a copper gasket to "safely" run higher boost, but again you then have to look at your injectors. Based on some calculations if i remember them correctly by engineer mike, he claimed the boost at 21psi, and your standard mods of IC, riva ecu,inj, etc will get you about 320 bhp...But don't quote me on this...
    Right now, I have yet to hear someone with turbo who has gone more than 30 hours without a rebuild.. But i hope that isnt the case, as i am seriously interested this kit as well and dont want to rebuild half way thru the summer.. Oh as for the manifold, the kit uses a modified j-pipe to fit to the turbo..No one has said this out loud but based on the photo of the kit and the few install pics posted, and the fact jerri is looking for j-pipes, well two and two equals...

    If your looking for more info on the turbo I suggest you check out the garrett webpage.

    hope this helps...

    Quote Originally Posted by boostaholic View Post
    What model/size turbo comes with the kit, or what are you using? I have been curious about this for some time, other than the added heat, and cooling of the charger, this should be fairly trivial since the motor is already designed for forced induction. The fuel system is already in place, and the engine is already running forged low compression pistons. The OEM ECU does use a boost comp map correct? IE it calculates fuel requirement on the fly based on manifold boost pressure, correct? I saw this discussed before, but never found an answer, did anyone ever find out any specifics on the maximium boost level where the fuel table ends on an OEM RXP ECU? I would imagine you could see 300hp with somewhere around 15lbs of boost, being that a turbocharger is inherently more efficient. Taking into effect the free HP gain from no longer having to turn the SC. Once you swap to a turbo, this engine would probably benefit nicely from a lighted single gear flywheel, as I imagine a dramatic weight savings is possible there.

    Kinda got off track there, but I was just curious what size, and or make/model turbo is being used on the 4tec turbo setups? Thanks.

  4. #4

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    Yea, according to Jerry, the turbo is a GT28. No one knows if it's an R or an RS. The R is very similar to the older T3 60 trim that came stock on the SVO Mustangs. The RS is very similar to the old T3 Super 60 trim that came stock on the Buick GN's. The newer stuff has very similar compressor maps, but is slightly more efficient (~3%) due to CFD and better manufacturing control.

    According to the compressor map, the GT28RS will max out on the 4-tec motor at around 2.5/1 Pr and 37.5 lb/min. That's the equivalent of 22 psi boost and 407 hp.

    For comparison, the T3 60 trim will max out on a 4-tec at about 2.2 and 33 lb/min. That's 17.5 psi and 360 hp.

    As per the other thread, I'm now not sure if the stock MAP sensor is 2, 2.5, or 3 bar. Bosch documentation says 2.5, but BTtek says 2 then later 3. No one knows about the fuel map either.

    It's been my experience that anything that comes from the factory NA can only handle 4 - 9 psi boost without coming apart. Anything that comes from the factory with boost (even if it's only 7 psi) can run well over 20 psi safely. Take a look at the stock-engine Buick turbo's running 30 psi, the stock-engine Supra's running 40+ psi, and the Ford SC mod motors running 20+ psi and all holding up just fine.

    I thought is was funny when I first got into these that people think going from 7 psi to 11 psi on a stock motor was really pushing the limits. I was shocked to find no one running over 13 or so from a Rude. With 8.5/1 compression, all forged bottom end, pentroof chamber, water/air intercooling, a Speed-Density EFI system with no MAF/O2 sensor/OBD2, I figured we would have been well over 20 psi years ago.

    Mike

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