Turbo Cam ???
05-04-2012, 08:53 AM
#43
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Agree! If you are going to overpower your turbo (Big cubes, small turbo) you have to run a Reverse split... My car (years ago) when I was first starting was runing a STS 67mm turbo... it ran like crap until I put a reverse split cam in it helping address the backpressure and reversion issues... it was however a bandaid. The real problem was what INTMD8 is trying to point out... and one I learned after having to blow up my engine because I wanted to show everyone they were wrong (I was wrong).Turbo selection... Pick a good cam yes, but it wont make up for your turbo selection. You can make it work yes, but you may well join my club... or at least be chasing surge issues and fuel issues due to backpressure results, in the end burning out some major component (turbo or motor).
Nobody is beating you up for your selection here... please dont take it that way, they are simply sharing with you the experience of alot of their time, money and racing experience. IMHO, lessons from these guys is the best value you get... I have learning almost everything I know about these cars from many of these guys. Your other option is you can simply pay a great shop like SPEEDINC to build it for you, orrrrrrr rebuild it for you!!
05-04-2012, 08:57 PM
#46
05-04-2012, 09:37 PM
#47
yeah dont focus on it too hard. i gave my cam reference because it is a good cam, and close enough in spec for be very beneficial to the power adder of your choice. There really is no perfect spec'd cam because all setups are different in some way even if they use the same parts. Basically a wide lsa, and between 580-600 lift is a good general area to be in. Brutespeed and thunder racing, and speed inc, and ECS all make cams for blown, turbo, applications.
05-04-2012, 10:06 PM
#48
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Jim and Kurt. I was looking to up the power, what do you thinking about a .993-.913 @ 119.4 224~289
Will that keep the turbos running in the right direction?
Will that keep the turbos running in the right direction?
05-05-2012, 10:29 AM
#51
Jokes aside, the cam is just one component which needs to work with the other components. So to make a sweeping generalization as to what a turbo cam should be just doesn't work. You guys have to remember that alot of cam theory has to do with cylinder scavenging (clearing out the cylinder w/ pressure differential) and trying to avoid reversion (contaminating the charge with exhaust gases). Both of these rely heavily on exhaust backpressure or lack there of. Turbos are an exhaust restriction. The smaller the turbo, the bigger the restriction which changes what may or may not work as well for a cam.
Now, even after you understand all that, the theories as to what works best vary from "expert" to "expert". This is why you can give your specs to 5 different experts and get 5 different cams. And to confuse the matter even more, they could all be very very close in power output with slightly different power curves. Meaning that the one that makes the most peak power may be giving up alot under the curve so it may not actually be better. Then you must consider transmission type and converter stall. So the cam for a stick shift car would need to make alot more power down low than say a cam for an auto with a 5500 stall which can obviously be more peaky.
Hope that helps
Now, even after you understand all that, the theories as to what works best vary from "expert" to "expert". This is why you can give your specs to 5 different experts and get 5 different cams. And to confuse the matter even more, they could all be very very close in power output with slightly different power curves. Meaning that the one that makes the most peak power may be giving up alot under the curve so it may not actually be better. Then you must consider transmission type and converter stall. So the cam for a stick shift car would need to make alot more power down low than say a cam for an auto with a 5500 stall which can obviously be more peaky.
Hope that helps
05-12-2012, 02:54 PM
#58
Your turbo will now be fine.
Cam:
Turbos dont need alot of cam. But this can very greatly with set up. Your hp goal is low for a LS motor of this size with turbos, which can easily put you into the stock or little above stock cam sizes. This would really apply if you had the lower compression LQ4 instead of an LQ9. The LQ9's will run over 10 to 1 compression. One of the things that helps the LS guys get away with so much compression and FI is bigger cams and wider LSA's because both usually delay the closing of the intake valve. The later closing of the intake helps to keep cylinder pressures lower especially at lower rpms. The late intake closing also helps to maintain good cylinder pressures at higher rpms, where a small cam would really be dropping off. Good cylinder pressure = good torque, good torque and higher rpm at the same time = really nice HP
HP goal and LQ4 with stock, little bigger, or moderately bigger cam would all be legit choices. Which ties into some one saying cam really isnt that important.
LQ9 with its higher static compression.... prob go anywhere in the 220's.
Dont over do the LSA. GM engineers have a whole lot of other things to worry about other than performance. These "OTHER" factors are why their factory cams are ground with such large LSA's. You also dont need crazy LSA's for turbo motors. A 112 LSA would be fine. Installed at 110 intake centerline for a little better throttle response and better spooling.
Answer: 224/224 224/228 228/228 with 112 or 113 LSA. With or under .600" lift with stock ratio rocker arms of 1.7 to 1. Drop the advertised cam lift to about .565" or under if you are going to run 1.8's
HTH: Jason
HTH
Cam:
Turbos dont need alot of cam. But this can very greatly with set up. Your hp goal is low for a LS motor of this size with turbos, which can easily put you into the stock or little above stock cam sizes. This would really apply if you had the lower compression LQ4 instead of an LQ9. The LQ9's will run over 10 to 1 compression. One of the things that helps the LS guys get away with so much compression and FI is bigger cams and wider LSA's because both usually delay the closing of the intake valve. The later closing of the intake helps to keep cylinder pressures lower especially at lower rpms. The late intake closing also helps to maintain good cylinder pressures at higher rpms, where a small cam would really be dropping off. Good cylinder pressure = good torque, good torque and higher rpm at the same time = really nice HP
HP goal and LQ4 with stock, little bigger, or moderately bigger cam would all be legit choices. Which ties into some one saying cam really isnt that important.
LQ9 with its higher static compression.... prob go anywhere in the 220's.
Dont over do the LSA. GM engineers have a whole lot of other things to worry about other than performance. These "OTHER" factors are why their factory cams are ground with such large LSA's. You also dont need crazy LSA's for turbo motors. A 112 LSA would be fine. Installed at 110 intake centerline for a little better throttle response and better spooling.
Answer: 224/224 224/228 228/228 with 112 or 113 LSA. With or under .600" lift with stock ratio rocker arms of 1.7 to 1. Drop the advertised cam lift to about .565" or under if you are going to run 1.8's
HTH: Jason
HTH
