Turbo cam choices
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TECH Junkie
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From: Glen Burnie, Md
Turbo cam choices Where would you go with reverse split and where a traditional split?
Any ever logged the backpressure curves of their turbo setup? I think that would be most determining factor as far as cam choices. I think the intake opening and exhaust closing events should be held around TDC to minimize overlap
I would think a single turbo kit, with a less effecient exhaust setup as compared to a twin setup - would prefer something like a 212/224 wide LSA - seeing the turbo like a restrictive exhaust setup
A more efficient exhaust twin setup Id say a reverse split may make sense, dont exhaust the charge until its doing the most good spooling the turbo up.
However Ive seen guys running reverse split on single T76 cars. I wonder how much pumping losses these are incurring at high rpm? On restricted ex NA motors, supercharged stuff, I add to the opening side of the exhaust lobe. Not detrimental to power NA but does cut useable cylinder pressure at low rpm boost because they keep cylinder pressure longer. A reverse split goes against all this. Well unless your placing the opening side at the same point as a restricted NA motor, and closing the exhaust valve WAY earlier. But is there enough cam lobe area to blow down the cylinder like that?
Not looking to make 9 milion footlbs of torque at 2000 rpm. Its nice and all, but Id rather set up the car to make max torque between FOUR thousand
-6500 rpm 346 inch with T76
Any ever logged the backpressure curves of their turbo setup? I think that would be most determining factor as far as cam choices. I think the intake opening and exhaust closing events should be held around TDC to minimize overlap
I would think a single turbo kit, with a less effecient exhaust setup as compared to a twin setup - would prefer something like a 212/224 wide LSA - seeing the turbo like a restrictive exhaust setup
A more efficient exhaust twin setup Id say a reverse split may make sense, dont exhaust the charge until its doing the most good spooling the turbo up.
However Ive seen guys running reverse split on single T76 cars. I wonder how much pumping losses these are incurring at high rpm? On restricted ex NA motors, supercharged stuff, I add to the opening side of the exhaust lobe. Not detrimental to power NA but does cut useable cylinder pressure at low rpm boost because they keep cylinder pressure longer. A reverse split goes against all this. Well unless your placing the opening side at the same point as a restricted NA motor, and closing the exhaust valve WAY earlier. But is there enough cam lobe area to blow down the cylinder like that?
Not looking to make 9 milion footlbs of torque at 2000 rpm. Its nice and all, but Id rather set up the car to make max torque between FOUR thousand
-6500 rpm 346 inch with T76 Last edited by GrannySShifting; Jan 9, 2005 at 12:18 AM.
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From: WWW.SPEEDINC.COM
Most 'reverse split' turbo cams I have seen, have accomplished this by closing the exhaust valve early.
Generally, I like single pattern cams for turbo cars.
Everyone will tell you to go with a really wide lsa and the least amount of overlap as possible. I disagree with that, as I've dyno tested -many- cams in my car.
More overlap (or actually less negative overlap @.050), made ALOT more top end power, with no sacrifice to the rest of the powerband, even when exhaust backpressure was nearly twice boost pressure.
The cam we've been using with our single turbo setup is-
225/225 113lsa 111icl
My next cam will be something like-
221/221 112lsa 110icl
JMHO
Generally, I like single pattern cams for turbo cars.
Everyone will tell you to go with a really wide lsa and the least amount of overlap as possible. I disagree with that, as I've dyno tested -many- cams in my car.
More overlap (or actually less negative overlap @.050), made ALOT more top end power, with no sacrifice to the rest of the powerband, even when exhaust backpressure was nearly twice boost pressure.
The cam we've been using with our single turbo setup is-
225/225 113lsa 111icl
My next cam will be something like-
221/221 112lsa 110icl
JMHO
Originally Posted by GrannySShifting
Not looking to make 9 milion footlbs of torque at 2000 rpm. Its nice and all, but Id rather set up the car to make max torque between 400-6500 rpm 346 inch with T76
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Thread Starter
TECH Junkie
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From: Glen Burnie, Md
Originally Posted by smokinHawk
if that is your goal KEEP your stock cam it will perform nicely there.
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Originally Posted by GrannySShifting
My stock cam will not make maxx possible torque from 4000-6600 rpm
Your original post says 400-6500rpm, so some people may assume you want torque off idle. Fix the post so it says 4000. 