Turbo Cam ???
FormerVendor
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From: WWW.SPEEDINC.COM
TECH Fanatic
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5.3L ~45* 114 LDA 193/193 @ .050
LS1 ~44* 116 LDA 196/207 @ .050
LS6 ~40* 117.5 LDA 204/218 @ .050
LS9 ~39* 122.5 LDA 211/230 @ .050
LSA ~39* 119 LDA 198/216 @ .050
So why is it then GM for their factory Supercharged engines are running less valve overlap and a wider LDA than their non-supercharger engines? Not one of their engines is running a Reverse Split Duration cam either.
I'm just wondering because if my the information I've read is incorrect I'd like to be corrected.
LS1 ~44* 116 LDA 196/207 @ .050
LS6 ~40* 117.5 LDA 204/218 @ .050
LS9 ~39* 122.5 LDA 211/230 @ .050
LSA ~39* 119 LDA 198/216 @ .050
So why is it then GM for their factory Supercharged engines are running less valve overlap and a wider LDA than their non-supercharger engines? Not one of their engines is running a Reverse Split Duration cam either.
I'm just wondering because if my the information I've read is incorrect I'd like to be corrected.
Last edited by F0x Slaughter; May 1, 2012 at 09:33 PM.
FormerVendor
Joined: Dec 2001
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From: WWW.SPEEDINC.COM
Stock 1987 Buick Grand National Cam-
38 degrees overlap
192/196 @.050
107 LSA
Pretty tight LSA on a restrictive turbo system and I'm fairly certain the turbo doesn't start to spin backwards.
Basically what I'm saying is, repeating (a somewhat skewed perception) of what you read on that website does not translate into reality. There is no reason for super wide LSA's or an exaggerated delay for IVO even on a less than ideal turbo system.
ever get the feeling you waste your breath?
my buddy is running 5psi (yes 5) on a 76mm and wants to put heads on the thing when all he needs is a gasket swap... people make it really difficult to let you help them sometimes.
The other type of compressor surge is when you have a compressor that is moving more air than the motor can ingest at WOT. Oversimplified.
5.3L ~45* 114 LDA 193/193 @ .050
LS1 ~44* 116 LDA 196/207 @ .050
LS6 ~40* 117.5 LDA 204/218 @ .050
LS9 ~39* 122.5 LDA 211/230 @ .050
LSA ~39* 119 LDA 198/216 @ .050
So why is it then GM for their factory Supercharged engines are running less valve overlap and a wider LDA than their non-supercharger engines? Not one of their engines is running a Reverse Split Duration cam either.
I'm just wondering because if my the information I've read is incorrect I'd like to be corrected.
LS1 ~44* 116 LDA 196/207 @ .050
LS6 ~40* 117.5 LDA 204/218 @ .050
LS9 ~39* 122.5 LDA 211/230 @ .050
LSA ~39* 119 LDA 198/216 @ .050
So why is it then GM for their factory Supercharged engines are running less valve overlap and a wider LDA than their non-supercharger engines? Not one of their engines is running a Reverse Split Duration cam either.
I'm just wondering because if my the information I've read is incorrect I'd like to be corrected.
Also, supercharged cam theory is far more similar to N/A cam theory than it is to turbo cam theory.
Because that turbo is too small for the cubes. Meaning that it will likely have very high pressure ratio. Reverse split should help with that. As mentioned by others though, the turbo is the problem not the cam. I ran 10.0 @ 135 running out of gear about 150-200' out with a bone stock LQ9 long block. That's in a 3850# car. Works out to about 600-650 rwhp.
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I haven't talked with anyone at GM but I would assume they run those cams because it's what they needed to meet their goals.
Stock 1987 Buick Grand National Cam-
38 degrees overlap
192/196 @.050
107 LSA
Pretty tight LSA on a restrictive turbo system and I'm fairly certain the turbo doesn't start to spin backwards.
Basically what I'm saying is, repeating (a somewhat skewed perception) of what you read on that website does not translate into reality. There is no reason for super wide LSA's or an exaggerated delay for IVO even on a less than ideal turbo system.
Stock 1987 Buick Grand National Cam-
38 degrees overlap
192/196 @.050
107 LSA
Pretty tight LSA on a restrictive turbo system and I'm fairly certain the turbo doesn't start to spin backwards.
Basically what I'm saying is, repeating (a somewhat skewed perception) of what you read on that website does not translate into reality. There is no reason for super wide LSA's or an exaggerated delay for IVO even on a less than ideal turbo system.
Thread Starter
Joined: Oct 2003
Posts: 1,313
Likes: 10
From: Las Vegas NV
Ok ,so is better to invest in a better turbo !
How about TC78 turbonetic with 1.15 ar. Now the 317 heads are stock you guys think is good idea porting them and put 2.08/1.57 valves or just use that money in the turbo? I already have the new set of SS Valves.
How about TC78 turbonetic with 1.15 ar. Now the 317 heads are stock you guys think is good idea porting them and put 2.08/1.57 valves or just use that money in the turbo? I already have the new set of SS Valves.
FormerVendor
Joined: Dec 2001
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From: WWW.SPEEDINC.COM
What are the advantages of a 112.5 vs a 115+3 ?
I don't know turbos or cams, I am running a 372 iron/LS3 topend with a gt91.
My builder ordered a custom grind as follows:232 234 .595/.576 115+3
Thread Starter
Joined: Oct 2003
Posts: 1,313
Likes: 10
From: Las Vegas NV
FormerVendor
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This is where I get into trouble generalizing.
The actual LSA figure doesn't really matter, what it all comes down to is the valve events. By that I mean, choose the valve events and the LSA is a byproduct of that (not the other way around).
After many years of building and testing different combinations, our preference is to run turbo cams with similar valve events as something you would use on a naturally aspirated engine along with relatively mild lobes that maintain stability at high rpm (7500+ if the turbos are up to task).
Your cam will work great, I see no problem with it even though it is slightly different than what I would use.
The actual LSA figure doesn't really matter, what it all comes down to is the valve events. By that I mean, choose the valve events and the LSA is a byproduct of that (not the other way around).
After many years of building and testing different combinations, our preference is to run turbo cams with similar valve events as something you would use on a naturally aspirated engine along with relatively mild lobes that maintain stability at high rpm (7500+ if the turbos are up to task).
Your cam will work great, I see no problem with it even though it is slightly different than what I would use.
FormerVendor
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If it's for the combo you listed in the first post, I don't know what cam would be considered ideal because that turbo on your engine is far from ideal.
I don't think you would see much gain with anything much bigger than an LS6 cam, it's just not going to make up for the turbine inefficiency.
For example, by playing around with the cam from stock to -anything you might see a 30, 35hp difference.
Now, if you tossed a PT7675 on there you will probably see a couple hundred HP difference, even with the stock cam, which is why I think the money is best spent there.
I don't think you would see much gain with anything much bigger than an LS6 cam, it's just not going to make up for the turbine inefficiency.
For example, by playing around with the cam from stock to -anything you might see a 30, 35hp difference.
Now, if you tossed a PT7675 on there you will probably see a couple hundred HP difference, even with the stock cam, which is why I think the money is best spent there.
I have seen the turbo spin backwards on the dyno, does that mean I need a new cam? I think it looks cool when the turbo spins backwards, so I might not change it even if it's wrong.....
Kurt
Kurt
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