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Thread: GT42 big enough?

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    GT42 big enough?

    Hi there, I'm new to the turbo world and was after a little advice. After reading about a standard LS2 with a Chinese GT42 going 150+ mph down the quarter I went and bought myself one GT4294 along with an Aeromotive rising rate regulator.. My question now is would this be suitable for a currently 590hp NA 406chev looking to add approx 150hp. My plans are to gather the extra necessary parts bov, wastegate, carby mods etc over the next 12 months. Any assistance is greatly appreciated and please excuse my lack of knowledge in this subject.

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    あなたの母親の肛門 Shifty's Avatar
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    There are plenty of people here who can help, but be prepared to cop a bit of a belting as most people here like to take the piss.

    So the first question is - how much do you think this will cost? I think it is worth back-tracking and planning this out. If you have spent $500 on an ebay turbo you only have about $19,500 to go. In the grand scheme of things you should look at buying a quality turbo as at 90hp/litre from 6.5+ litres you're obviously accustomed to good gear & aware what it costs.

    It has been done many times with a carb, some of those have been successful, but generally they are not so you'd want to add EFI to your 'to do' list.

    I'd also speak to your engine builder and see if the engine will suit boost as if your current one is built to 90hp/litre already you'll likely need to reconsider the whole thing - maybe sell yours as a package (depending on value) and start again with a boost-specific engine build as you'll probably be throwing most of it in the bin. I have little-to-no engine-specific experience with V8s but it would be fair to say you'd be almost certainly be looking at new aftermarket block, crank rods and pistons as a starting point as well as a totally revised cylinder head & camming.

    There's an extensive list of things you'll need to consider like oil & water lines for the turbo, new collectors/headers and at least a partial new exhaust, intercooler and piping, fuel system (double your current size), tuning, driveline etc etc etc as even if it's all upgraded much of it will need revisiting.
    Last edited by Shifty; 04-05-17 at 05:49 PM.

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    あなたの母親の肛門 Shifty's Avatar
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    And to answer your question, my opinion is that that turbo is too small for that engine but so is a 150hp target increase. You will struggle to keep power DOWN to 590hp+150hp if you do it right.

    You might instead be better considering a decent bit of nitrous if 'all' you want is 150hp.

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    Thanks for the response Shifty, the combo consists of an SHP block K1 steel crank Callies H beam rods Brodix Dragonslayer 227 heads slightly massaged custom solid roller and AED 950 carb. My assumptions so far are a turbo specific cam, compression adjustment carby mods Reg etc.
    I thought I'd seen these turbos on ls1's going 150 in the quarter.

  5. #5
    Goat roper Motherfucker Jones's Avatar
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    They seem to max out at around 750 rear wheel. You've got all good shit, why not at least put a Borg Warner s480 on it? It'll probably make 900 by accident. It would suck to blow up a $2 turbo and hurt a good motor

    If you can do a e85 blow through setup you could probably run non intercooled for simplicity and if you're under 11:1 comp it will prob still work alright with ethanol.
    Quote Originally Posted by RVK 355 View Post
    Hold it flat cunt

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    Thanks Motherfucker, I'd be stoked if it made anywhere near 750rwhp. Honestly I'd be pretty happy with 600-650rwhp if I can do it safely, good tune and not maxing out the revs. I was under the impression that there were plenty of these units surviving ok in a lot of situations. My aim is to still drive it on the street and develop some nicer street manners with the turbo. I've already purchased the turbo, if in the event of a failure would an intercooler prevent any hurt to the motor?
    Cheers.

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    Twin China GT4294's would be about right, on ethanol, keep the high compression ratio.

    You'd need to run about 1psi of boost to make your target, so plenty of headroom as your balls drop and you turn it up.
    Your signature is too long.

  8. #8
    Now with more ebay parts. 2JZR31's Avatar
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    I would run like 2 psi just to be extreme.
    10.83 @ 125

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    Quote Originally Posted by cracka View Post
    Some conclusions empirically were that a large protruding ridge like a prolapsed arsehole around the runner was largely beneficial.

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    Haha cheers guys, myliberty is that the e10 blend I hear about on the telly or e85?

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    Registered User Dexi's Avatar
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    United 85 as a minimum with that comp ratio for sure

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    Yeah E85 mate.
    Your signature is too long.

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    GT42 turbine is too small for an engine making that sort of power NA. You could add another if there is room or go to an S480 if there is no room for 2 turbos. Even an S475 would be better and they are cheap.
    You have to remember that the LS2 that made X power with a GT42 added was only making 350hp NA. You have to size the turbo for the exhaust flow of a 500hp NA engine regardless of whether you are targeting a small power increase.


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    David Fraser - Automotive Historian!

    Quote Originally Posted by bigmuz View Post
    You can't polish a turd but you can put 600hp in it and laugh your fucking arse off coming past someone sideways at Powercruise.

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    Quote Originally Posted by JZK25 View Post
    GT42 turbine is too small for an engine making that sort of power NA. You could add another if there is room or go to an S480 if there is no room for 2 turbos. Even an S475 would be better and they are cheap.
    You have to remember that the LS2 that made X power with a GT42 added was only making 350hp NA. You have to size the turbo for the exhaust flow of a 500hp NA engine regardless of whether you are targeting a small power increase.


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    Thanks mate appreciate the tip. I'd rather run a single, the other spot I have I'd prefer to put a air to water cooler if need be.

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    Now with more ebay parts. 2JZR31's Avatar
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    Quote Originally Posted by JZK25 View Post
    GT42 turbine is too small for an engine making that sort of power NA. You could add another if there is room or go to an S480 if there is no room for 2 turbos. Even an S475 would be better and they are cheap.
    You have to remember that the LS2 that made X power with a GT42 added was only making 350hp NA. You have to size the turbo for the exhaust flow of a 500hp NA engine regardless of whether you are targeting a small power increase.


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    That's pretty much what I always said when people reckoned turboing a Vtec "doesn't work". A Vtec engine is just a hipo NA engine with big cams when it kicks in yo.
    10.83 @ 125

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    Quote Originally Posted by cracka View Post
    Some conclusions empirically were that a large protruding ridge like a prolapsed arsehole around the runner was largely beneficial.

  15. #15
    Registered User dnegative's Avatar
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    Highly efficient engines go even harder with boost.
    GT42 is way small but fuck it would be a monster for the first half 4000rpm
    Quote Originally Posted by cracka View Post
    Fuck I'm retarded

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    This is me standing by my first comment.
    Your signature is too long.

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    Ok thanks guys, might have to chase up a BorgWarner S480 S475 or equivalent......anybody after an ebay GT4294?

  18. #18
    \_(ツ)_/ burn is weird's Avatar
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    Just return it and get a refund, ebay are cunts to sellers these days. buyer is always right.

    Oo___oO


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    Well I bit the bullet, I've onsold the GT4294 and just purchased an Airwerks S400-475 with a 1.32A/R
    Hope to start a build thread in the next 12 months, it'll take a while I'm guessing.

  20. #20
    \_(ツ)_/ burn is weird's Avatar
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    you have done the right thing.

    Oo___oO


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    Ok so the seller showed me picks of the S475 he was about to post and it had bad scoring and casting imperfections that made it look like it had been run over by a truck. He offered me $20 off!! No thanks dude, that was 4 weeks ago and now Im in the process of buying a brand new Garret Billet 88mm with T6 dual entry and 1.15a/r. It'll sit for awhile until I have funds for manifolds BOV carby etc.

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