turbo cam theory.
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turbo cam theory. hey guys i am thinking about getting a cam to go into my engine that will soon be turbocharged. i am looking to do the cam just to have a little more power until the turbo goes on, have a little fun with the install, and better learn to tune with EFILive.
i have read all kinds of things about turbo cams and what they should have/be. what works well, what doesnt, etc.
I have a pretty decent amount of what i want it to be but before i decide on what exactly i want, i was wondering if anyone could answer a couple things for me.
First, i know that a higher LSA is desired. but i am not exactly sure why. i know that we dont want overlap cause that will bleed boost...but is having 0* of overlap just as good as having 5*, or 10*? in other words is more overlap better? or is it all pretty uch the same.
Second, i read on smokinhawk's turbo FAQ that the higher LSA helps with the spool of the turbo, but is that actually directly related to the LSA or does it go back to the Overlap?
Now that that is out of the way i am going to assume that the duration and lift will be something to determing based on my desired rpm band that i am shooting for. and i am shooting to have a high reving engine...maybe shift at like 6900even. i dont know if this is something that is ok on a turbo engine, but that would be the goal.
Now i have more questions, but they heavily rely on the answers to the first two questions so if anyone knows the answers to those...that's be great.
Thanks
Louie
i have read all kinds of things about turbo cams and what they should have/be. what works well, what doesnt, etc.
I have a pretty decent amount of what i want it to be but before i decide on what exactly i want, i was wondering if anyone could answer a couple things for me.
First, i know that a higher LSA is desired. but i am not exactly sure why. i know that we dont want overlap cause that will bleed boost...but is having 0* of overlap just as good as having 5*, or 10*? in other words is more overlap better? or is it all pretty uch the same.
Second, i read on smokinhawk's turbo FAQ that the higher LSA helps with the spool of the turbo, but is that actually directly related to the LSA or does it go back to the Overlap?
Now that that is out of the way i am going to assume that the duration and lift will be something to determing based on my desired rpm band that i am shooting for. and i am shooting to have a high reving engine...maybe shift at like 6900even. i dont know if this is something that is ok on a turbo engine, but that would be the goal.
Now i have more questions, but they heavily rely on the answers to the first two questions so if anyone knows the answers to those...that's be great.
Thanks
Louie
you want little to no overlap.Quoting a sponsor you usually want somewhere between -8 degrees to +2.And i probably will be selling my brand new never used T76GTS if youre interested.Im waiting on an email for a bigger turbo,but if i get that 1 then ill sell you mine.
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Originally Posted by ddnspider
you want little to no overlap.Quoting a sponsor you usually want somewhere between -8 degrees to +2.And i probably will be selling my brand new never used T76GTS if youre interested.Im waiting on an email for a bigger turbo,but if i get that 1 then ill sell you mine.
Also thanks for the info...but i am looking more for why...than what.
Louie
I am likely getting lingenfelter gt7 but think the GT2-3 is also a good one for turbos too and think they used to use it a lot.
I think lingenfelter knows a thing or two about turbocharging!!
I think lingenfelter knows a thing or two about turbocharging!!
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Originally Posted by MY99TAWS6
I am likely getting lingenfelter gt7 but think the GT2-3 is also a good one for turbos too and think they used to use it a lot.
I think lingenfelter knows a thing or two about turbocharging!!
I think lingenfelter knows a thing or two about turbocharging!!
turbo...but i also have to consider they are building their cars as a package...maybe if they were one offers like we are they would grind the cam a little differently...
That is why i want to learn about how cams work with turbo...what affects what.
Once i do my own research and question asking, then i will be able to get a better idea of a cam for my own personal car, like, and wants.
Thanks
Louie
Duration is more important than lift, and IMO LSA. People increase duration to make more power.
I'm going to a 237/231//115 cam for the turbo. I found that one prominent FI shop advocated reverse splits for max power, mostly because running too much exhaust duration would increase backpressure (for a single turbo application). Cams for the most part are compromises between streetability, goals, and durability of your drivetrain.
Lift is dependent on your cylinder heads, and the the limitations of your cam grinds.
From talking to a lot of turbo cam folks, and some shops, the common generalizations are that cams in the 220's duration can make a lot of power, and will be enough for most folks. Stuff in the 230's would be for 800-1000rwhp, or more, and stuff in the 240's would be for 1000-1400rwhp combos.
I don't think most turbo cam manufacturers sweat LSA as much as we do, and I found that one prominent shop generally tried to stay around a 114 LSA with most of their grinds. But it sounded like 113 or 115 would not be a big deal.
My comments are generalizations and partially just opinion.
I'm going to a 237/231//115 cam for the turbo. I found that one prominent FI shop advocated reverse splits for max power, mostly because running too much exhaust duration would increase backpressure (for a single turbo application). Cams for the most part are compromises between streetability, goals, and durability of your drivetrain.
Lift is dependent on your cylinder heads, and the the limitations of your cam grinds.
From talking to a lot of turbo cam folks, and some shops, the common generalizations are that cams in the 220's duration can make a lot of power, and will be enough for most folks. Stuff in the 230's would be for 800-1000rwhp, or more, and stuff in the 240's would be for 1000-1400rwhp combos.
I don't think most turbo cam manufacturers sweat LSA as much as we do, and I found that one prominent shop generally tried to stay around a 114 LSA with most of their grinds. But it sounded like 113 or 115 would not be a big deal.
My comments are generalizations and partially just opinion.
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Verdad Gallardo Some of those LPE cam grinds are just the Z06 cam with more lift. If a Z06 grind is like a 208/218//117.5, is it a bad cam? Not at all. But the LSA for that cam was driven by a compromise of power, emissions, and part-throttle driveability. The new C6 Z06 cam is like a 211/230 I think and I'm sure the lsa is like 117 maybe even 119. But it idles pretty darn good.
One tuner I know has tended to like single pattern cams quite a bit, and I'm sure that he's probably seen marginal increases with splits, so he prefers the single patterns for idle quality.
I think to really see a pattern, you'd need to find a sample pool of folks who all have the same turbo kit, and see how their powerbands differ based on cam selection.
Hi Javs.
One tuner I know has tended to like single pattern cams quite a bit, and I'm sure that he's probably seen marginal increases with splits, so he prefers the single patterns for idle quality.
I think to really see a pattern, you'd need to find a sample pool of folks who all have the same turbo kit, and see how their powerbands differ based on cam selection.
Hi Javs.
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...yeah it is extremely difficult to get an cold hard proof on a cam selection. it seems like everyone(literally) runs somthing different. there are so many opinions out there it is rediculous.
I really may just go with an off the shelf TR cam.
i was kind of liking the 227/224 114 LSA.
220's duration
114 lsa
and still has negative overlap. ie no overlap.
i cant imagine that it would work poorly based on the average of the ideas given here. i am going to maybe try to look into the valve events and get an idea of what exactly the valves will be doing in this application.
PSJ, based on what you are saying (i understand it is just generalized info not law) the Z06 cam, and damn near all of the LPE cams should work great for them...they make TT cars, and have high exhaust duration...but maybe the z06 and LPE cams are not really that great for a single...i dunno...
Well thanks for the info guys.
Louie
I really may just go with an off the shelf TR cam.
i was kind of liking the 227/224 114 LSA.
220's duration
114 lsa
and still has negative overlap. ie no overlap.
i cant imagine that it would work poorly based on the average of the ideas given here. i am going to maybe try to look into the valve events and get an idea of what exactly the valves will be doing in this application.
PSJ, based on what you are saying (i understand it is just generalized info not law) the Z06 cam, and damn near all of the LPE cams should work great for them...they make TT cars, and have high exhaust duration...but maybe the z06 and LPE cams are not really that great for a single...i dunno...
Well thanks for the info guys.
Louie
The only real generalization that I like is that duration makes power. To a point, but I don't think we have found that point. So when folks advocate the Z06 type stuff it's better than stock but IMO not as good as other stuff out there.
The cam I have is Mightymouse's old cam, so we can compare a little bit my new numbers with his hold numbers with the same one.
The cam I have is Mightymouse's old cam, so we can compare a little bit my new numbers with his hold numbers with the same one.
I have an f13 cam right now. Im about to buy the hi-flo kit and im not changing out the cam right off. Im going to dyno it first and see what happens... Of course Im only going to run about 600rwhp which doesnt make as much difference as the really high hp apps. But I plan to change to a z06 or similar cam which is smaller but I should pick up hp right.
What are the specs of the F13? Personally the only time I would do a Z06 cam is when I got it for $100 or it came stock in the car. You are doing from like a 205/211 (stock) to a 208/218 (Zo6)... That's not worth it to me. If was doing a turbo cam from scratch, I'd probably look into 228/228 stuff for 700-800rwhp, and 240/232 stuff for big power. My guess is that Mike Brown runs something like the latter, but he has more cubes than me.
I got it for $75 but was told and read that it was a really good cam to go with... But then again look at the topic lol... From everything I have read there has been no testing done to find a "turbo cam" and people get random numbers with he same cams .. However, since Suggestion ill look into it more.. thanks
Cam timing is normally adjusted to deal with the factors involved with filling and emptying the cylinder. The two main factors are time and pressure differential.
The time required to do the job is very directly dependant on pressure differential at the valve, and the flow capacity of each valve of course.
You have to keep in mind that a turbocharger is changing the pressure differential to a very significant degree.
Basically the pressure difference (absolute) at the intake valve is normally much more, and fills the cylinder faster... which is why boost works in the first place.
The pressure differential (absolute) at the exhaust valve would normally be less, which would empty the cylinder slower. Turbocharged systems have much more backpressure than supercharged or NA systems.
There is also a distinct lack of pressure-wave tuning from the exhaust side of most turbocharged systems. That really changes the game as far as overlap and LSA is concerned.
IMO it's a good idea to get a good consult from someone vastly experienced in spec'ing cams for turbo applications. Then you can be sure to get the best efficiency out of the system, or at least try your hardest to.
Also IMO, this follows the same rule as nitrous cams in that EVERY cam is a turbo cam once the boost comes up. Think about it. If you're still able to make X amount of boost and peak power at a higher RPM, you should see higher peak numbers on the dyno. You will be working the turbo harder to do so obviously, so efficiency will be down. Total power output will be high, though you may have some side-effects of lag or slower spool time.
With N2O it's easy just to jet up until you get the power you want, no matter how bad of a match your camshaft happens to be. Every cam is a nitrous cam, but that doesn't mean it's the best match for efficiency.
The time required to do the job is very directly dependant on pressure differential at the valve, and the flow capacity of each valve of course.
You have to keep in mind that a turbocharger is changing the pressure differential to a very significant degree.
Basically the pressure difference (absolute) at the intake valve is normally much more, and fills the cylinder faster... which is why boost works in the first place.
The pressure differential (absolute) at the exhaust valve would normally be less, which would empty the cylinder slower. Turbocharged systems have much more backpressure than supercharged or NA systems.
There is also a distinct lack of pressure-wave tuning from the exhaust side of most turbocharged systems. That really changes the game as far as overlap and LSA is concerned.
IMO it's a good idea to get a good consult from someone vastly experienced in spec'ing cams for turbo applications. Then you can be sure to get the best efficiency out of the system, or at least try your hardest to.
Also IMO, this follows the same rule as nitrous cams in that EVERY cam is a turbo cam once the boost comes up. Think about it. If you're still able to make X amount of boost and peak power at a higher RPM, you should see higher peak numbers on the dyno. You will be working the turbo harder to do so obviously, so efficiency will be down. Total power output will be high, though you may have some side-effects of lag or slower spool time.
With N2O it's easy just to jet up until you get the power you want, no matter how bad of a match your camshaft happens to be. Every cam is a nitrous cam, but that doesn't mean it's the best match for efficiency.
White I liked where your post was going, though towards the end you did a "make sure you use an expert." 
The three big questions in my mind, when it comes to turbo cams is:
-How much duration for a given engine combo, and when is too little or too much
-More info regarding how overlap, too much or too little, affects power for a turbo combo
-How do turbo cam folks spec turbo cams to keep the combo from having ridiculous torque and at the same time have great power under the curve.
It's sort of like if you had a 348ci engine with good heads... If you wanted to hit 1000rwhp, would you avoid the 230/230 cam because the 236/230 just makes another 30rwhp, or do you think about going to the 240/232 because that bigger cam has the best power of all.
The three big questions in my mind, when it comes to turbo cams is:
-How much duration for a given engine combo, and when is too little or too much
-More info regarding how overlap, too much or too little, affects power for a turbo combo
-How do turbo cam folks spec turbo cams to keep the combo from having ridiculous torque and at the same time have great power under the curve.
It's sort of like if you had a 348ci engine with good heads... If you wanted to hit 1000rwhp, would you avoid the 230/230 cam because the 236/230 just makes another 30rwhp, or do you think about going to the 240/232 because that bigger cam has the best power of all.
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It's just like any other combination. You should pick your goals for horsepower, driveability, rpm range, efficiency and choose the combination accordingly.
I believe many turbo setups are over-cammed. Meaning that you would max out the combination long before the cam would hold you back.
To generalize, I prefer single pattern cams on tight LSA's.
I believe many turbo setups are over-cammed. Meaning that you would max out the combination long before the cam would hold you back.
To generalize, I prefer single pattern cams on tight LSA's.
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Originally Posted by Pro Stock John
White I liked where your post was going, though towards the end you did a "make sure you use an expert."
The three big questions in my mind, when it comes to turbo cams is:
-How much duration for a given engine combo, and when is too little or too much
-More info regarding how overlap, too much or too little, affects power for a turbo combo
-How do turbo cam folks spec turbo cams to keep the combo from having ridiculous torque and at the same time have great power under the curve.
It's sort of like if you had a 348ci engine with good heads... If you wanted to hit 1000rwhp, would you avoid the 230/230 cam because the 236/230 just makes another 30rwhp, or do you think about going to the 240/232 because that bigger cam has the best power of all.
The three big questions in my mind, when it comes to turbo cams is:
-How much duration for a given engine combo, and when is too little or too much
-More info regarding how overlap, too much or too little, affects power for a turbo combo
-How do turbo cam folks spec turbo cams to keep the combo from having ridiculous torque and at the same time have great power under the curve.
It's sort of like if you had a 348ci engine with good heads... If you wanted to hit 1000rwhp, would you avoid the 230/230 cam because the 236/230 just makes another 30rwhp, or do you think about going to the 240/232 because that bigger cam has the best power of all.
Originally Posted by INTMD8
It's just like any other combination. You should pick your goals for horsepower, driveability, rpm range, efficiency and choose the combination accordingly.
I believe many turbo setups are over-cammed. Meaning that you would max out the combination long before the cam would hold you back.
To generalize, I prefer single pattern cams on tight LSA's.
I believe many turbo setups are over-cammed. Meaning that you would max out the combination long before the cam would hold you back.
To generalize, I prefer single pattern cams on tight LSA's.
that is very generalized...lol
are you saying that the LSA will be soo tight that there will be positive overlap or do you still like to keep the overlap at a minimum?