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Thread: Compound Boost

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    Forum Newbie Array assquatch20's Avatar
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    Compound Boost

    Heya, I know it's not the preferred method at all, but I'm looking to twincharge and shoot for the moon in HP. Girdled block and all the toys, but supercharged and turbocharged. I've been reading up on it for a couple years now. My first thoughts were to buy up a SAAB LK9 and maybe swap heads, but I'm really unsure how to go about it all as far as heads and internals.

    It's a longitudinal application, an AWD Chevette. If I can get the numbers GM say in the build book, that would be fantastic, but I am not following the book, clearly.

    Just please try to spare me the supercharger hate. It will have a bypass at higher revs and I'm thinking meth injection to assist the end of the curve. Maybe n2o for kicks. It's definitely an engineering demo in overkill.

    So, what crank, rods, pistons, heads? Standalone for sure, but what would you use?

    The layout will be turbo feeding SC, with 2-3 intercoolers in the chain. SC bypass will be looped to a blowoff to let the turbo take over at a set point. Hopefully looking for multiple tunes on the fly, but the programming and sensor setup here is a little over my head. I've been focused on the mechanics of it.

    Anyhow, that's a lot, but if you can make any sense of it and throw out any advice, it would be appreciated. Long time reader, first time writer here. Keep up the good work.

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    Personally, I'd look more into what Volvo is doing with their newest twin-charged four-cylinder. Basically, the have a supercharger feeding into a turbocharger, helping the turbo spool up faster, until the turbo is spooled enough that the air then bypasses the supercharger entirely and goes directly to the turbo. The major issue with a turbo feeding a supercharger is how much the supercharger heats up the incoming air and decreases the efficiency. That was the reason ZZP moved away from twin-charging a few years back.

    Mechanically, you'll probably want forged rods and forged pistons, with ceramic-coating for the pistons to keep them from getting too hot. The LK9 cylinder-head is a good one, and you'll probably want to port it, get some upgraded valvesprings, and perhaps some stronger valves for such a demanding application. Your meth injection is probably going to be most useful in keeping the air going into the engine cool enough that it doesn't blow up the engine.

    You're right, tuning is going to be a BITCH.

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    Forum Newbie Array assquatch20's Avatar
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    Personally, I'd look more into what Volvo is doing with their newest twin-charged four-cylinder. Basically, the have a supercharger feeding into a turbocharger, helping the turbo spool up faster, until the turbo is spooled enough that the air then bypasses the supercharger entirely and goes directly to the turbo. The major issue with a turbo feeding a supercharger is how much the supercharger heats up the incoming air and decreases the efficiency. That was the reason ZZP moved away from twin-charging a few years back.

    Mechanically, you'll probably want forged rods and forged pistons, with ceramic-coating for the pistons to keep them from getting too hot. The LK9 cylinder-head is a good one, and you'll probably want to port it, get some upgraded valvesprings, and perhaps some stronger valves for such a demanding application. Your meth injection is probably going to be most useful in keeping the air going into the engine cool enough that it doesn't blow up the engine.

    You're right, tuning is going to be a BITCH.
    Fallen2603 Quoted Post
    The issue there is what seems like a more complicated bypass for the SC. I'm not positive a blowoff would do the same job here, but the advantages to the routing are clear. I was trying to keep everything but the fuel mechanical, really. Probably no ABS or power steering. I'm just now playing with a programmable transfer case instead of a fulltime mech. setup. I may end up routing it this way, but kinda slim chance.

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    You could probably make it really simple by just getting the bypass unit off of the Volvo engine, even from a junkyard, and just figure how it is actuated. I assume it's actuated by boost reference like the bypass valves you'd find in a stock LSJ set-up, just bigger. I just think it's a much better idea to have the more efficient turbocharger being what feeds the engine, especially if you'll only need one air-to-air intercooler. Most of the ZZP twin-charged set-ups blew up because the compounded boost the supercharger was pumping into the cylinders was way to hot, even with the laminova-core charge-cooler. I'm also more of a K.I.S.S. (Keep It Simple, Stupid) person.

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    I doubt you will find any supercharger hate around here, they are pretty common.

    Important question needs to be asked here.....what means of supercharging are you looking at, roots or centrifugal? Major differences in capability and flexibility.

    For tuning, the AEM standalone is decent from what I have heard if you have the pockets to empty on it.

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    Roots. The stock SAAB turbo and the M62 would be convenient, and I might try it, but I'd say that's not what I need come time to make more power. A larger turbo would probably be needed. If funds permit at some point in spacetime, a TVS would be much welcomed to the mix.

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    I just went back and read your original post and got confused. Could you clarify this:

    The layout will be turbo feeding SC, with 2-3 intercoolers in the chain. SC bypass will be looped to a blowoff to let the turbo take over at a set point.
    The point of you trying to run the s/c with the turbo is to have a higher amount of power without waiting for spool time correct?

    It sounds to me like you are shooting for this....
    Boost1.png
    Which would need heavy modification to the intake manifold and seems to me like having the 2 devices in series could be more restricting for the supercharger when you need it the most.

    A setup like this seems to me to be more efficient...
    Boost2.png
    This could be done with a roots, still heavy modification to the intake manifold, but would be much easier with a centrifugal (ProCharger or the like) which still share some performance characteristics of the roots since it is belt driven. A much cleaner turbo manifold could be used in this application.

    When you are sucking air for your intake system, whether it be turbo, s/c, or NA; you want it to travel as short a distance, and as few bends as possible, and you don't want anything in the way. With the turbo (and it's subsequent cooling system) in the way it becomes a restriction in the intake pipe (because lets face it, if it wasn't you wouldn't be looking to supplement it). Every bend and extra length of pipe decreases the systems efficiency and power delivery.

    My 2 cents, I have no references to cite

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    The point of you trying to run the s/c with the turbo is to have a higher amount of power without waiting for spool time correct?

    It sounds to me like you are shooting for this....
    Boost1.png
    Which would need heavy modification to the intake manifold and seems to me like having the 2 devices in series could be more restricting for the supercharger when you need it the most.
    Sparkey Quoted Post
    That is indeed what I was sorta thinking. The manifold thing is a great point, and part of why I'm here. I have some theories on all of this and know few enough specs for the Ecotec to know I want to use it, but I'm not actually familiar enough with them. Your picture is correct, just incomplete. There will be a lot of piping and bends, but I intend to tune the entire intake tract, so perhaps I can remedy it a bit.

    presentazione-2.jpg

    The idea is to stay cheap and avoid a clutched charger, but let the bypass do a similar job. I'm not sure how well it can work, but one of the better references I have is this link and the threads it links to. The fella whose handle is "Warpspeed" over there has enlightened me a bit to what Lancia were doing back in the day for Group B.

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    I didn't include the minor details, I.C.'s and such, for simplicity sake.

    I have seen it done where the laminova cooler core integral to the LSJ supercharged manifold has been removed, and in its place welded in baffeling that diverts the charge air to piping and run to an intercooler, then returned. I cannot remember if the inlet and outlet were both done in the place where the laminova cores bolt on (side of the manifold) or if there was some welding and piping added to the underside of the manifold. Here is a crude picture of the internal air flow and structure of the stock supercharged intake manifold.

    IM Flow.png

    The Eaton M62 blowers used on these motors has been called the Heaton before since it is not thermally efficient. It creates quite a large amount of heat on it's own so sending air from a turbo at it, you would want to be very sure was nice and cool.

    What exactly is your power goal here? This is going to be a big, expensive pain in the ass and if cheap is in your vocabulary I would turn back. Depending on what your goals actually are there could be a cheaper way to reach them than twin charging. Though it would be pretty badass to roll up twin charged.

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    If you're going for under 600WHP, I'd recommend the Volvo method.

    If you're going for upwards of 1,000WHP, then the set-up like the image you posted may be more practical. However, the cost of parts needed to support that performance level will be VERY expensive.

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    Well, ideally I aim for the 3-400whp that I've seen out of boosted Ecotecs, using the M62 and Saab turbo somehow, but build the motor to take much more boost. Then we're aiming for four figures with better compressors and much better tuning, the meth injection, etc.

    The mandated goal is to "Boldly construct an all-wheel-drive twincharged Chevette, capable of unleashing one thousand horses and a great many torques, with various states of tune, adept at hauling ass or just 'some ass', ready to wake from its slumber at any given stoplight, rendering its opponents awestruck & defeated, whilst hell freezes and swine glide over the earth, and so it will be. Amen."
    Last edited by assquatch20; 08-25-2015 at 11:53 PM.

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    I'd probably just skip the M62 entirely and jump up to a M90 off a Thunderbird Super Coupe. They are probably the most compact M90 supercharger with plenty of mounting options. Just use a big pulley so you're not turning it too fast to keep it in it's efficiency range, until you start going for four digits. Hitting 300-400WHP is doable with a supercharger (HTV1320) or turbocharger independently and without difficulty.

    If you're planning on pushing that much power, you'll want the "Gen 3" block.

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