Turbo Street cam choice
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Joined: Dec 2000
Posts: 1,320
From: Alta Loma, CA
Re: Turbo Street cam choice
Originally Posted by engineermike
That's a good question.
The risk has to do with rpm range and is quite different from a turbo to a supercharger.
Supercharger: Since boost is proportional to rpm, a centrifugal supercharger will typically raise the power band 1000 rpm or more. When you have a large cam, then add a supercharger, you wind up with an engine that's relatively weak on low end, but screams on top.
Turbocharger: In many cases, you can't or don't put a large enough turbo on a V-8 engine. So, unless you go with a Thumper T-6 turbo, the turbo can only support x cid to x rpm. The rpm range of the engine has to match the turbo's capabilities. For instance, if the turbo can only support 383 cid up to 6000 (such as a T-76) and your cam is 260 at .050, then it's counterproductive.
The risk has to do with rpm range and is quite different from a turbo to a supercharger.
Supercharger: Since boost is proportional to rpm, a centrifugal supercharger will typically raise the power band 1000 rpm or more. When you have a large cam, then add a supercharger, you wind up with an engine that's relatively weak on low end, but screams on top.
Turbocharger: In many cases, you can't or don't put a large enough turbo on a V-8 engine. So, unless you go with a Thumper T-6 turbo, the turbo can only support x cid to x rpm. The rpm range of the engine has to match the turbo's capabilities. For instance, if the turbo can only support 383 cid up to 6000 (such as a T-76) and your cam is 260 at .050, then it's counterproductive.
I'm going with a fully built 355 with AFR 195CC LT4 heads and a valve train designed to go to 7k RPM. I'm building the motor like that so that I can have a very wide power band, and want my turbo to work up to 7k.
Sorry for butting into the thread.
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Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
Re: Turbo Street cam choice
Originally Posted by maximumvelocity
How would a 221/221 558/558 lift 114LSA lunati cam compare to the Comp XE 218/218 114lsa 110icl .528/528 in terms of driveability and power/performance range on this setup? Will a little more durration and a little more lift help or hurt and if so at what range?
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Joined: Feb 2002
Posts: 5,645
From: Bridgewater, MA
Re: Turbo Street cam choice
Originally Posted by snorkelface
How would I be able to determine what turbo would be best for my setup?
I'm going with a fully built 355 with AFR 195CC LT4 heads and a valve train designed to go to 7k RPM. I'm building the motor like that so that I can have a very wide power band, and want my turbo to work up to 7k.
Sorry for butting into the thread.
I'm going with a fully built 355 with AFR 195CC LT4 heads and a valve train designed to go to 7k RPM. I'm building the motor like that so that I can have a very wide power band, and want my turbo to work up to 7k.
Sorry for butting into the thread.
Here is your lb/min consumption based on presure ratio (which shows boost) and the rpms your turning the engine. The result is the lbs/min of air needed.
http://www.forcedinductions.com/consumption355.htm
Next, look at a compresor map and mark points for your lbs/min and pressure ratio on the compresor map. Belo is a compressor map for a T76 which would be a nice turbo for you.
http://www.forcedinductions.com/images/t76.jpg
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Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
Re: Turbo Street cam choice
Originally Posted by snorkelface
How would I be able to determine what turbo would be best for my setup?
I'm going with a fully built 355 with AFR 195CC LT4 heads and a valve train designed to go to 7k RPM. I'm building the motor like that so that I can have a very wide power band, and want my turbo to work up to 7k.
I'm going with a fully built 355 with AFR 195CC LT4 heads and a valve train designed to go to 7k RPM. I'm building the motor like that so that I can have a very wide power band, and want my turbo to work up to 7k.
The next step up is to a T-88, but it is physically larger than the 76 and will not fit most turbo kits. Plus, it only gained about 20 rwhp over the 76 on the car mentioned above. There are a couple of in-between options that the 76 can be upgraded with also, like maybe an 80 and 82.
Mike
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Joined: Dec 2000
Posts: 364
From: Durham,NC,
Re: Turbo Street cam choice
Originally Posted by RealQuick
Do you have a link to the cams?
here is a link to the cam in the new summit mag.
http://store.summitracing.com/defaul...=egnsearch.asp
here is the 210/218
http://store.summitracing.com/defaul...=egnsearch.asp
how would these work under boost
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Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
Re: Turbo Street cam choice
Originally Posted by JDMZ28
What would be the most efficient rpm and boost level with the T76? Did I notice 9 and 11 psi where highlighted on the graph?
Peak efficiency of the T-76 comes at 15 psi and 550 hp at 78%. However, as I said, it's been proven to 1150 hp at 22 psi, which corresponds to ~65% efficiency.
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Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
Re: Turbo Street cam choice
Originally Posted by JDMZ28
. . .What are you pushing with your setup Mike? 600+rwhp?
Mike
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Joined: Dec 2000
Posts: 1,320
From: Alta Loma, CA
Re: Turbo Street cam choice
Originally Posted by engineermike
Compressor maps are not based on rpm.
Peak efficiency of the T-76 comes at 15 psi and 550 hp at 78%. However, as I said, it's been proven to 1150 hp at 22 psi, which corresponds to ~65% efficiency.
Peak efficiency of the T-76 comes at 15 psi and 550 hp at 78%. However, as I said, it's been proven to 1150 hp at 22 psi, which corresponds to ~65% efficiency.
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Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
Re: Turbo Street cam choice
Originally Posted by snorkelface
So how can I assure that the turbo I am matching with my setup will be good across the power band I am designing engine to run up to (7k RPM shifts)?
What are the spec's on your cam?
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Joined: Dec 2000
Posts: 1,320
From: Alta Loma, CA
Re: Turbo Street cam choice
Originally Posted by engineermike
What are your power goals? I, personally, don't have an rpm goal, but more of a power goal. If it makes 1000 rwhp, I don't care if it's at 3500 rpm.
What are the spec's on your cam?
What are the spec's on your cam?
The turbo setup will likely be either a PTK, or a new GMR Speed setup if it's out in time. I'm using components that will be good to a 7k shift point because I am using an auto, and therefor I don't have a lot of gears to utilize.
From what I understand though, I should be in the 900FWHP range. I would sacrifice peak power for a wider power band.
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Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
Re: Turbo Street cam choice
I think you may be going about this the wrong way. I think your logic is that you want a wide power band because an auto has only 3 gears to use in the quarter. However, an auto with a proper torque converter actually keeps the engine in a very narrow rpm range. Mine only drops about 300 - 400 rpm on the shifts, so the engine is always between 5800 and 6200. The torque converter experts say that the optimum rpm drop on the shift is about 600 rpm. Either way, don't spend so much effort and sacrifices trying to get a broad power band.
With either of those kits, you will probably be stuck with the T-76 anyway, due to the larger overall size of the T-88. The T-76 will go way over 900 fwhp anyway.
With either of those kits, you will probably be stuck with the T-76 anyway, due to the larger overall size of the T-88. The T-76 will go way over 900 fwhp anyway.