Supercharger AND Turbo? SURE! - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Forced Induction All questions and problems regarding Superchargers, Turbos, NOS, ZEX, intercoolers, water injection, etc.

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Old 11-13-2003, 09:34 PM   #11
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Well I read most all of those. It seems that somewhere along the line the SC becomes obsolete or even an obstruction. What I never did find on the West Coast Fiero car was. Is over all boost increased ? or just the power band ? This turbo lag is just an issue from a dead stop right ? Once moving and above idle the turbo is spinning and pumpin right ? The higher the exhaust pressure the more rpms on the compressor ? Seems like the SC would only benefit those concerned with 0-60 or 60 ft times. Then what impresses me most about the L67 is the way it just keeps pulling stronger and stronger the higher the engine RPMs, until shift then the process startes over again..

I drive a diesel truck everyday but have never driven a Turbo gas engine to see how it acts. On the truck the turbo wistles right up once the R'* are up a little, whats neat is how they add pressure when more load is applied as in hills with out actually adding pedal. When the engine gets a load the exhaust pressure goes up spinning the turbo faster. A SC doesnt do anything until the engine R'* increase.

Im sure theres got to be clear benefits of applying both but Im strugling to see it.

I'm interested in hearing everyones therories here.
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Old 11-13-2003, 10:43 PM   #12
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Just because you increase boost doesn't increase power. Boost is the measure of pressure in the intake manifold. You can have a car have only 7 psi of boost and be making 1000HP (its been done with well designed heads) and a car that has 15psi and only makes 500HP. It'* about airflow.

Twincharging came about in the Toyota MR2 Turbos (well more well known about it). Basically it was a kit I believe from HKS (I think one of the big companies) that would put a roots supercharger to get the car moving and bypass the supercharger once the turbo had spooled up. It was an effective way to get low end torque with top end power.

Another person with a F-150 Lightning truck decided he did not have enough power. So they put on a Centrifigal supercharger w/ an air to air intercooler that feed into the stock Eaton MP112. It made another 100HP without pushing that much boost from the centrifigal. It was an interesting thing.

The Eaton M90 is good up to 400WHP basically. You guys change pullies on your cars and feel more power but not that much. To a certain point its the heads that are holding you back for more power. If you port and polish the heads you can get more airflow in there and even though your boost gauge will register less psi, you will be making more power because you are actually get more fuel and air into the engine. More lift through the cam will help as well. =)

Diesel'* are totally different machines... They have a narrow operating band and very very long strokes. That'* why they make 200HP and 500 lb-ft of torque.... And there is a F-250 and also a F-350 running 13'*... They make 500HP and 1000lb-ft of torquey. Just using a bigger turbo but they run on different priciples. Diesel'* run on detonation, not spark plugs.

And there ya go. There are no theories, just need to know what to do.
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Old 11-14-2003, 03:52 AM   #13
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Well said, Hector-man.

Another example is the 2-stage vacuum pumps I use at work occasionally. They pull an AMAZING amount of vacuum (we're missing a couple techs still), and they do it with a 2-stage Roots setup. Pull vacuum with one, then increase it through the second stage. Works like a charm.
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Old 11-14-2003, 07:40 PM   #14
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Thanks Hector. I did know most of that basic Diesel and headflow infomation. I've read most of Thrashers site and am a firm believer in benefits of head work and engine build up , not bolt on miracles. On diesels I have a 64 Fordson based tractor, its got a 330 c.i. inline 6 diesel, a design started by a English designer during WWII but not finished until 53 because of finances in England as a result of the war. It was the design that finally worked (started on demand) and became the standard. I've had it 20 years and it was the backbone of my finances for 15 years. I also have a 86 GMC Brigadere thats got a 671 Detriot in it, they are alway blown, 2 stroke, intake ports/no intake valves, 4 exhaust valves per cyl. Fires BTDC every stroke. A different animal indeed. A diesel fires on the heat created by intense compression of the air and fuel mixture. It detonates because of this compression factor, some as high as 21:1. Maybe more. I know nothing about new diesel design and nothing at all about these PU engines.

By therories I meant, what would you guys think would be noticable on a L67 if someone were to put a turbo before the blower. Im thinking the blower and the ports would limit the volumn anyhow. If the heads were ported would the blower then restrict the volumn from a turbo. 8psi from a turbo + 8psi from the blower would not = 16 would it ? I'm just trying to picture how the L67 would react to this kind of modification. Theres not really a way to bypass the blower on the L67.
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Old 11-15-2003, 12:27 AM   #15
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Quote:
Originally Posted by Steve LS
By therories I meant, what would you guys think would be noticable on a L67 if someone were to put a turbo before the blower. Im thinking the blower and the ports would limit the volumn anyhow. If the heads were ported would the blower then restrict the volumn from a turbo. 8psi from a turbo + 8psi from the blower would not = 16 would it ? I'm just trying to picture how the L67 would react to this kind of modification. Theres not really a way to bypass the blower on the L67.

Well basically the Eaton would not have to work to pull any air since it woudl be fed by the turbo. And the Eatom M90'* are only so effecient and do leak around the sides of the rotor'*. But if you wanted ultimate power, you would just toss aside the M90 and run all turbo, would make more power that way. But with a smaller turbo, the idea is that if you had it intercooled, you can provide the M90 with a cooler intake charge and let it compress it for more power since the air is not heated up as much (the air entering). If you put the turbo (sized it right) you would make more power. maybe 60-100HP more. Depends how you set it up but you would make more power on the top end where the M90 gets more ineffecient.
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Old 11-15-2003, 01:46 AM   #16
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HMM ! Would the draw from the Eaton at idle help to spool the turbo ? Small turbo would spool faster anyhow, but too small and you would loose the volumn at top end that your trying to gain.

Intercooled fluid to air systems are so expensive. That would be some awful hot air entering the engine after the twin system. Even intercooled turbo air entering the Eaton would be much hotter than what is entering now right ?

Do you think alot more engine control or fuel managment systems would also be necessary or would the existing system be able to handle it ?

Would this be roadable ? Octane ?

I must reread some Thrasher tec articles.
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Old 11-15-2003, 11:55 AM   #17
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you would probably need more fuel. I know when I spoke to Chris West of West Coast Fieros he said I would need a larger fuel pump and run the Hal-Tech computer. I guess I will try to call chris again he said he would send me all the info I needed to make the conversion work and alot more questions can be answered.
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Old 11-16-2003, 08:18 PM   #18
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How is the fiero, I was thinking of picking one up if I can find one chep somewhere.
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Old 11-18-2003, 01:45 PM   #19
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The fiero is extremely fun to drive especially with the 3800sc. Almost like driving a go kart, extremely fast go Kart @ that.
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Old 11-18-2003, 11:31 PM   #20
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Here is another link that shows a few of the Cars that west coast fiero has done including a few pics of the Twin Charged 3800 series 1 on page 2.

http://www.cardomain.com/id/westcoastfiero
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