Turbocharger cam specs....
Originally Posted by Shinobi'sZ
Are you sure you are not smoking Kentucky Blue Grass out there.... 
I would really like to see your 1/4 mile run at 9.50secs on street tires...do you have a video or somebody to vouch for you...because if you did or do...that is pretty fn amazing!
Like I said C5R Block....and you don't need a C5R block to get any LS1 into the 9's. Wade Stevens at ARE has a 422 with a 200 shot in the hi 8's..without a C5R block.
I would really like to see your 1/4 mile run at 9.50secs on street tires...do you have a video or somebody to vouch for you...because if you did or do...that is pretty fn amazing!
Like I said C5R Block....and you don't need a C5R block to get any LS1 into the 9's. Wade Stevens at ARE has a 422 with a 200 shot in the hi 8's..without a C5R block.
*sigh*I'm NOT saying LS1's can't do 10 seconds or less in the quarter. We all know they are quicker. I am saying that when Lingenfelter builds a C5 that will run under 10's they will use the C5R block like stated above.
And his C5 that runs 8's has a C5R. Thats what I saw and here's an article on it.
http://lingenfelter.com/images/CF427TT_eprint.pdf
My quarter mile run??? And why did street tires come up???
BTW- RIP John. You will be missed.
Registered User
Joined: Jun 2002
Posts: 453
Likes: 0
From: Forced Induction Heaven
Originally Posted by rodent
*sigh*My quarter mile run??? And why did street tires come up???
(
Last edited by Shinobi'sZ; Dec 31, 2003 at 01:33 PM.
That came off this link:
http://lingenfelter.com/pac725ttls1y.asp
I know Lingenfelter considers MT ET Streets street tires since that was brought up at the Corvetter Shootout in KY. People were whining to the officials that Johns tires wern't street tires even though they are DOT rated and that was one of the rules. Not really my idea of a true street tire but what ever.
http://lingenfelter.com/pac725ttls1y.asp
I know Lingenfelter considers MT ET Streets street tires since that was brought up at the Corvetter Shootout in KY. People were whining to the officials that Johns tires wern't street tires even though they are DOT rated and that was one of the rules. Not really my idea of a true street tire but what ever.
hmm thought we are talking about ls1's not C5R's (the engine block that cost 6k) thats why i tried to show the difference. The C5R's do perform (along with their heads) better then the ls1. so you need to compare then on different bases.
But one reasoning ive heard to go with the reverse split was that
since all air going into the engine must come out if you use a smalller exhaust durration it will cram the air out faster, this in response, this high velocity air will spool/power the turbo better, which in turn provides more air to do the exact same thing again.
But one reasoning ive heard to go with the reverse split was that
since all air going into the engine must come out if you use a smalller exhaust durration it will cram the air out faster, this in response, this high velocity air will spool/power the turbo better, which in turn provides more air to do the exact same thing again.
Originally Posted by Phil99vette
Anyone have an explanation why to run a reverse split?
Phillip
Phillip
I think that I am going to use the LPE GT2-3 myself.
Registered User
Joined: Jun 2002
Posts: 453
Likes: 0
From: Forced Induction Heaven
Originally Posted by sr71
I don't really understand the reasoning myself....as a matter of fact, one of the comp tech guys(Hadley) that is supposed to be "the turbo guy", reccomended a 222/226-114 to me. he told me that a larger exhaust lobe on a higher rpm engine would help keep the turbo spooled. one that was too small would have trouble keeping the turbo spun up.
I think that I am going to use the LPE GT2-3 myself.
I think that I am going to use the LPE GT2-3 myself.
I have always been told the reasoning in running a cam with less exhaust duration is that there is less tendancy to bleed off boost..it maintains higher cylinder pressures. Phil from Detroit Speedworks is working out a cam for me with Cammotion. He hasn't heard back from them yet..but I think the specs will be a 228/224 on a 116lsa with a 112icl...between 570-580 lift. My current cam is a 224/224 114 lsa on a 110icl at .581 lift. I am wondering how much difference it will really make.
Last edited by Shinobi'sZ; Jan 2, 2004 at 10:40 AM.
TECH Fanatic
Joined: Mar 2002
Posts: 1,044
Likes: 0
Originally Posted by CAT3
QMP single T76, and what about my current cam- TSP 231/237 wrong split, or good?
SC-
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
FormerVendor
Joined: Dec 2001
Posts: 2,444
Likes: 2
From: WWW.SPEEDINC.COM
Originally Posted by ChrisB
The exhaust can be restrictive, but that is a neccecary function of the turbo. Say you are running a 2:1 exhaust/manifold pressure ratio - you look at two cams - a reverse split and normal split. The reverse split is going to have much less overlap than the traditional split (assuming intake lobes are ~).
Now what happens during valve overlap? We have say 20psi on the exhaust side and 10psi on the intake side - which way is the system going to flow? Exhaust flowing back into the intake probably isn't what you want. Now there is still some inertia from the airmass moving, etc. but the more overlap you have the more you are going to start to backflow into the intake/get exhaust back into the cylinder.
Why more intake duration? To fill the cylinder - even though you are pressurized, etc. you still probably aren't achieving 100% fill at what ever pressure you are at. It may not be as much of an issue as it is NA, but it still is a pretty big issue - basically, you can only get air in the chamber when the valve is open.
So if you want as much intake duration as you can get, but want to limit overlap, you end up having to go smaller on the exhaust lobe.
But there isn't some huge change when you go from traditional/single/reverse split, it is all a progression. You may very well not end up with a reverse split - if you are running a 91mm thumper and seeing very low backpressure then you can get away with more overlap/more exhaust lobe - and more valve time in general is good since that is the only time your engine is "flowing".
So I guess the answer is that no, reverse splits aren't the way to go neccecarily - you probably will tend to see them more here as these motors tend to move a decent amount of air, especially the larger cubic inch ones. The turbo's people are using are smallish in general (compared to what import people are using vs. their engine's cfm flow, for example). There was a post on turbomustangs.com - an individual with a T-76 and a ~350" ford motor was seeing over 60lbs of backpressure at 20psi of boost. That type of situation is where you really need to limit valve overlap. On the other hand a T-88 at 10lbs of boost on the same motor may only see 20lbs of exhaust backpressure. In that situation you could get away with alot more overlap.
Now what happens during valve overlap? We have say 20psi on the exhaust side and 10psi on the intake side - which way is the system going to flow? Exhaust flowing back into the intake probably isn't what you want. Now there is still some inertia from the airmass moving, etc. but the more overlap you have the more you are going to start to backflow into the intake/get exhaust back into the cylinder.
Why more intake duration? To fill the cylinder - even though you are pressurized, etc. you still probably aren't achieving 100% fill at what ever pressure you are at. It may not be as much of an issue as it is NA, but it still is a pretty big issue - basically, you can only get air in the chamber when the valve is open.
So if you want as much intake duration as you can get, but want to limit overlap, you end up having to go smaller on the exhaust lobe.
But there isn't some huge change when you go from traditional/single/reverse split, it is all a progression. You may very well not end up with a reverse split - if you are running a 91mm thumper and seeing very low backpressure then you can get away with more overlap/more exhaust lobe - and more valve time in general is good since that is the only time your engine is "flowing".
So I guess the answer is that no, reverse splits aren't the way to go neccecarily - you probably will tend to see them more here as these motors tend to move a decent amount of air, especially the larger cubic inch ones. The turbo's people are using are smallish in general (compared to what import people are using vs. their engine's cfm flow, for example). There was a post on turbomustangs.com - an individual with a T-76 and a ~350" ford motor was seeing over 60lbs of backpressure at 20psi of boost. That type of situation is where you really need to limit valve overlap. On the other hand a T-88 at 10lbs of boost on the same motor may only see 20lbs of exhaust backpressure. In that situation you could get away with alot more overlap.
I think people would have a better understanding of how these things work if they looked at the actual valve events rather than the duration/lsa/icl numbers.
Registered User
Joined: Jun 2002
Posts: 453
Likes: 0
From: Forced Induction Heaven
That is the best response yet. I would gather from this that it very much depends on the whole setup. Let me ask you this. I had 20lbs of backpressure at 12lbs of boost and it was not measured at 16lbs of boost..but I imagine it still is not 3:1 mabye 2.5:1. Should I change my straight up cam???? What would I gain from it??
TECH Fanatic
Joined: Mar 2002
Posts: 1,044
Likes: 0
Originally Posted by ChrisB
So I guess the answer is that no, reverse splits aren't the way to go neccecarily - you probably will tend to see them more here as these motors tend to move a decent amount of air, especially the larger cubic inch ones. The turbo's people are using are smallish in general (compared to what import people are using vs. their engine's cfm flow, for example). There was a post on turbomustangs.com - an individual with a T-76 and a ~350" ford motor was seeing over 60lbs of backpressure at 20psi of boost. That type of situation is where you really need to limit valve overlap. On the other hand a T-88 at 10lbs of boost on the same motor may only see 20lbs of exhaust backpressure. In that situation you could get away with alot more overlap.
The fact is that reverse splits are not necessarily the way to go on a turbo app. If the turbo(s) are large enough, they can support some extra blow-through which can potentially give cooler cylinder charge temps, due to some limited, but additional, blow-through. Additional exhaust crutching doesn't actually factor too highly, since all cylinder heads flow less on the exhaust side. Turbos back up the exhaust side so additional exhaust duration (proportionally to the intake) may help the cylinder scavenging, in spite of the hypothesized reversion. My turbo intakes have never shown such reversion, as my N/A intakes have shown.
I give examples gallore, such as the fastest turbo LS1s, GN/TRs, and the SVO 2.3 motors. Certainly the Dutweiller cars are proof enough, just call the respective experts on those venues.
SC-
Last edited by SS00Blue; Jan 2, 2004 at 05:59 PM.
Well, I will hopefully put this to rest this spring. My car is getting a base incon kit and initially I will have just the kit on my stock shortblock (mods in sig) with GT2-2 lingenfelter cam. Once I get done showing SS00Blue (and his 43 years of combined experience) my tail lights, I am going to swap in a Lunati 226-222 115 with comparable lift and see what the gains will be (or not). 
Damn, I can't WAIT until spring!
-Geoff
Damn, I can't WAIT until spring!
-Geoff
Originally Posted by SS00Blue
You may not believe this, Chris, but I totally agree. I am sure you don't have much respect for my 18 years of production experience, or my 25 years of race experience, but never-the-less, you're exhibiting open-minded opinions, and I respect that.
The fact is that reverse splits are not necessarily the way to go on a turbo app. If the turbo(s) are large enough, they can support some extra blow-through which can potentially give cooler cylinder charge temps, due to some limited, but additional, blow-through. Additional exhaust crutching doesn't actually factor too highly, since all cylinder heads flow less on the exhaust side. Turbos back up the exhaust side so additional exhaust duration (proportionally to the intake) may help the cylinder scavenging, in spite of the hypothesized reversion. My turbo intakes have never shown such reversion, as my N/A intakes have shown.
I give examples gallore, such as the fastest turbo LS1s, GN/TRs, and the SVO 2.3 motors. Certainly the Dutweiller cars are proof enough, just call the respective experts on those venues.
SC-
The fact is that reverse splits are not necessarily the way to go on a turbo app. If the turbo(s) are large enough, they can support some extra blow-through which can potentially give cooler cylinder charge temps, due to some limited, but additional, blow-through. Additional exhaust crutching doesn't actually factor too highly, since all cylinder heads flow less on the exhaust side. Turbos back up the exhaust side so additional exhaust duration (proportionally to the intake) may help the cylinder scavenging, in spite of the hypothesized reversion. My turbo intakes have never shown such reversion, as my N/A intakes have shown.
I give examples gallore, such as the fastest turbo LS1s, GN/TRs, and the SVO 2.3 motors. Certainly the Dutweiller cars are proof enough, just call the respective experts on those venues.
SC-
Here's some more examples of the big cam companies selling reverse pattern cams for turbo cars:
http://www.holley.com/HiOctn/ProdLin...CC/Buick1.html
http://compcams.com/Technical/Catalo...L/110-113.html
http://compcams.com/Technical/Catalo...04/Page-3.html (mits turbo)
http://cranecams.com/import/mitsubishi.htm (stage 3 turbo)
http://cranecams.com/import/avteccams.htm (turbo)
http://www.crower.com/pdf/2-52.pdf (pages 25, 44, 45)
http://www.crower.com/pdf/53-104.pdf (pages 8, 13, 19)
http://www.cmotorsports.com/engine/l...ft-design.html (turbo)
So why are the big name companies suggesting RP cams in their catalogs for turbo applications? Don't you think they do that for a valid reason? And why would comp spec out a normal split when they're selling a RP for the largest cam of the Buick GN??? I'm planning on calling Comp Monday and see what they say.
I did read that a low exhaust lift helps keep velocity high and long duration and moderate lift on intake to keep restriction low which helps with turbo applications.
TECH Fanatic
Joined: Mar 2002
Posts: 1,044
Likes: 0
Originally Posted by White_Hawk
Once I get done showing SS00Blue (and his 43 years of combined experience) my tail lights, I am going to swap in a Lunati 226-222 115 with comparable lift and see what the gains will be (or not).
-Geoff
-Geoff
Anyway, I'm not saying that reverse splits are NOT the way to go. Many companies do this. I'm just saying that standard splits have benefits, too. Many cars run them. Maybe I'm mistaken, but I think the companies listed also have standard splits to offer. And, didn't Matt break a record or two with a standard split?
I guess I just mean that there are credible examples that standard splits work, too. Many GN/TRs use them, not to mention others. The guys suggesting reverse splits are not wrong, certainly their results show that. I'm just saying there are other schools of thought. If someone says they're right and there's no other right way has probably not been exposed to the alternatives.
Just sayin'
SC-
See ya this year, Geoff.
Launching!
Joined: Nov 2002
Posts: 224
Likes: 0
From: Florida
Like I said before, there are too many variables, Int/EX ratio, ECT...
But my original info came from a top engineer in the Turbo/Supercharging development & Advanced engineering dept of one of the Big 3 in Detroit. They have very cool toys to play with...
But my original info came from a top engineer in the Turbo/Supercharging development & Advanced engineering dept of one of the Big 3 in Detroit. They have very cool toys to play with...
TECH Addict
Joined: Nov 2001
Posts: 2,207
Likes: 0
From: College Station, Tx
If reverse pattern cams are not the way to go then why is Harlan and INTMD8 running one? Their engines are making gobs of power. Cammotion also spec'd out a RP cam earlier in this thread.
Couple of points:
1) I don't think anyone said "Reverse split camshafts are not they way to go" - rather, the "may not" be the way to go - again, it depends on your setup (primarily your backpressure/boost ratio).
2) It's definitely *not* a sitaution of "turbo = reverse split" - again, it depends on the overall setup. Also a small traditional split (say 214/224, 114) is going to have much less overlap than a larger reverse split (say 244/230, 116) - so again, there is much more to it than just being a "reverse split" or not.
3) There isn't any sort of magical transition that occurs when you go traditional split/single pattern/reverse split - it's just a change in degree. Your setup itself is going to dictate what you need.
Originally Posted by INTMD8
Actually, I'm not anymore. I'm using a 224/224 113lsa cam.
I know it depends on your setup but I'm trying to get a good reason why Comp Cams spec'd a RP cam for me. I'm currently building the engine and I'd rather install the right cam now than later down the road. It seams that a straight up cam (no split) is also used alot in turbo apps. Why did you pick that cam over others. Are you using any dyno similation programs? I might futz with dyno2000 (don't laugh) just to see what it shows on a SBC w/turbo. I also know that Rob Raymer is using a standard split and he's making good power too. This SP vs RP cam choice might have no right or wrong answer.
Well duration makes power and in the grand scheme of things a 224/224 cam makes more power than a say a stock cam, which is designed with a lot of other parameters in mind not just performance.
LS1/Gen III cylinders heads are excellent stock and fantastic ported. So when folks talk about cam specs on other motors the cam designs IMO are spec'd to get around the shortcomings of say an LT1 or a SBC OEM head casting. So when spec'ing cams I think we need to keep in mind you could have a 6.0 head that flowed 315/225 and that's pretty darn good. What do you need to crutch in that instance?
I think that for an effort that's trying to make 700-800 crank hp it's important to look at how much duration you need to support that power level.
LS1/Gen III cylinders heads are excellent stock and fantastic ported. So when folks talk about cam specs on other motors the cam designs IMO are spec'd to get around the shortcomings of say an LT1 or a SBC OEM head casting. So when spec'ing cams I think we need to keep in mind you could have a 6.0 head that flowed 315/225 and that's pretty darn good. What do you need to crutch in that instance?
I think that for an effort that's trying to make 700-800 crank hp it's important to look at how much duration you need to support that power level.
106mm, 232, 238, 427ls1, cam, cammotion, cams, comparison, dutweiller, lobes, pdf, specs, t76, turbo, turbocharged, turbocharger
