Turbos and cams

[AB'sLs1]

i am very interested in have a turbo ls1 the thing about it is that i dont know how they act with high lift cams and cams that have a good amount of over lap. ive heard alot of things from people saying that turbos love overlap and other people saying turbos hate overlap. so if anyone has any info on how a turbo and a high performance cam interact it would be much appreciated.

[rbarnes]

Turbos do not like overlap.

Overlap is good for N/A because you can use the vacuum created by
out flowing exhaust to help pull more air in.

But in a turbo set-up the turbo creates a certain amount of
exhaust pressure in the system. At higher boost pressures or with
too small of a turbo, back pressure can get high enough to actually
stop air from coming in. This is called reversion.

Turbo cams can have high lift and duration, but they need a high lobe separation.
LSA of 115-117 not uncommon on tubro cams, where N/A cam might be 110-112.

Stock cams actually usually make nice turbo cams with their high LSA's

[mike13]

Can you get a nice rumble with a turbo type cam?

[AB'sLs1]

Turbos do not like overlap.

Overlap is good for N/A because you can use the vacuum created by
out flowing exhaust to help pull more air in.

But in a turbo set-up the turbo creates a certain amount of
exhaust pressure in the system. At higher boost pressures or with
too small of a turbo, back pressure can get high enough to actually
stop air from coming in. This is called reversion.

Turbo cams can have high lift and duration, but they need a high lobe separation.
LSA of 115-117 not uncommon on tubro cams, where N/A cam might be 110-112.

Stock cams actually usually make nice turbo cams with their high LSA's

thank u that helped alot im trying to plan a nice build and i want to get as much info as i can before hand.

now lets say i wanna run a twin turbo at around 15 psi on a 346 what sort of lobe seperationg would u recommend?

[rbarnes]

Can you get a nice rumble with a turbo type cam?

My custom LSM turbo cam in my TT 351W mustang thumps like a mo-fo
240+ duration with .625 lift, but has like a 115+LSA

thank u that helped alot im trying to plan a nice build and i want to get as much info as i can before hand.

now lets say i wanna run a twin turbo at around 15 psi on a 346 what sort of lobe seperationg would u recommend?


Get a custom cam. I have an LSM cam. Only know Ford cam guys ,,,,, sorry.
Check the site for best custom cam grinders.

Tell the cam guy what you have and what you want ....... and thats what you get, no guessing

[AB'sLs1]

thanks alot everyone any info on how a cam interracts with a turbo is much appreciated. im still learning alot so any info u guys think would be helpful on my quest for amazing power is very helpful. so keep the info and ideas coming:thumbup:

[rbarnes]

If you really want to understand turbo systems get the following book.

Explains everything from engine dynamics to stainless vs mild to how
to read and use compressor maps to pick your turbo correctly.

http://www.amazon.com/Maximum-Boost-Turbocharger-Engineering-Performance/dp/0837601606/ref=sr_1_1?ie=UTF8&s=books&qid=1225326590&sr=8-1

[AB'sLs1]

haha shit a book! im not out of high school yet i get books out the wazooo! but this looks like a very valubale peice of info that i really should get my hands on. would u say that for somone who is interested in turbos but little knowledge this is a good buy?

[rbarnes]

haha shit a book! im not out of high school yet i get books out the wazooo! but this looks like a very valubale peice of info that i really should get my hands on. would u say that for somone who is interested in turbos but little knowledge this is a good buy?


Excellent book. Easy to follow along. 8th grade algebra will get you thru the engine
math on calculating airflows for any given engine.

[AB'sLs1]

Excellent book. Easy to follow along. 8th grade algebra will get you thru the engine
math on calculating airflows for any given engine.

alright its sold then haha the math part might get to be a challenge but it sounds like a really good book for me cuz i want to learn as much about motors(in general fbodys only)as i can in every aspect

[TNTramair]

http://www.youtube.com/watch?v=g8gRCx8_fs0

this is a TwinTurbo 402....cant give ya the specs on the cam cause its a prototype but i can tell ya its on a 118lsa.

[AB'sLs1]

wow that sounds amazing! thats the kinda idle i want if not that more aggressive and there r more cams out there that sound like this that r good for turbos? any info on this cam?

[TNTramair]

its a custom Grind cam that HSW did for me..its in the 230's intake and 240's exhaust i beleive, if i remember correctly with no overlap and on a 118lsa.
hearing the car in person it basically sounds like a car with headers and a cat back. there's a very light trace of a cam but it definetly makes the power and im very happy with it. pulls strong to 6500rpms...might go further but i only have about 600miles on the motor and i dont want to break anything just yet.

[AB'sLs1]

what im looking for is something that idles like a normal n/a motors cam would but i dont think im going to find that?

[slims00ls1z28]

Blah so my current MS3 on a 114 LSA (237/242 .605/.610) would be bad for a turbo? Was hoping to salvage some of the parts (and money) from my earlier build.

[rbarnes]

No it will not be a bad cam ......... just may not be the "best" cam

[candlelit]

I always recommend the epp FI cam for a LS1.

it's like a 23x/24x. 115 lsa. lift is pretty close to the .60 mark I think. it's pretty sick

[TNTramair]

Blah so my current MS3 on a 114 LSA (237/242 .605/.610) would be bad for a turbo? Was hoping to salvage some of the parts (and money) from my earlier build.
not an ideal cam for FI. it would work....just about any cam would "technically" work but there are better options suited for FI.

[RedVertTA]

With a turbo, you'll probably want a cam with more on the exhaust side to compensate for the larger amount of air coming in on the intake side.

[crazycat]

What size turbo ? If its a large frame t6 you should be able to cam it like a na car because of the low back pressure.

[99TAWS6]

I have gt7 and its great no lope but didn't want lope. I have it bumped to around 590 lift in the 408 but used 1.8 rockers they are fine with the cam seen the cam card and they were mentioned right on it. Some cams don't like bigger rockers.

Here is comparison of ling to stock cams.the last two are the grinds they usually have used in all their fi cars. The gt7 is still used a lot in their turbos and think the gt3 is more their super builds. But both would be good choices.If you don't want lope.These are normal split duration with more on the exhaust. Lift won't hurt anthing and most turbo cams have 115 and higher lsa typically. But you find guys running some different stuff. Turbos will make big power with almost any cam. It would take a dyno to see how much more you would make with the different cams . They need to do a good article on this subjet and test out some theories. We have guys that like reverse split, normal split,no split. We have guys that like lower lsa higher lsa.

All I know is doubt will need any more power with my current combo. Only thing will need is traction.Go too high on lift and you will be doing valve springs much more often. one reason I stayed a bit under the 600 lift point. Past 600 plan on spring changes maybe every 20,000 miles. I wanted to be able to go 50000 or so thats about 10 years of driving for me.

[crazycat]

Yes I wish some one would do some testing on a dyno with a bunch of differnt cams on a turbo motor so we can find out the truth about what works the best...

[RedVertTA]

Yes I wish some one would do some testing on a dyno with a bunch of differnt cams on a turbo motor so we can find out the truth about what works the best...

Yeah, but who would be willing to risk a motor?

[99TAWS6]

Umm risk a motor..why would they risk a motor? I have seen many different cams on fi builds,stock ,reverse split, normal split,no split,,different lifts and different durations and lsas.

Dyno testing would be great idea.

[cailey37]

Turbos do not like a lot of lift.....you can find plenty of dyno runs out there where they have been tested. each motor will respond a little differently but for the most part you'll be in the same ball park. my cam is really just a little over stock specs and performs quite well

[RedVertTA]

Umm risk a motor..why would they risk a motor? I have seen many different cams on fi builds,stock ,reverse split, normal split,no split,,different lifts and different durations and lsas.

Dyno testing would be great idea.

Well, I think I should take back part of what I said, its my fault for not being more specific. You're right, you probably won't downright blow a motor with a different cam, but there are some things in a cam that just aren't good for a motor. You could risk damaging some parts of the motor depending on what cam you went with. I guess if you just didn't go too extreme then you'd be right, and it shouldn't hurt the motor.

But as for what you specified, Quote: "the reverse split, normal split,no split,,different lifts and different durations and lsas." You couldn't just run the method of anything goes for this, certain characteristics of these would not be good for a motor.

Turbos don't like high lift. Its my understanding that excessive lift in a turbo motor won't yield the gains comparatively seen in an N/A motor and can also place stress on the valves with large boost pressures. This is harmful for a motor.

Turbos also don't like overlap. If you had a cam with a lot of overlap in a turbocharged motor, the turbo would create a larger amount of backpressure on the exhaust side and the burned gasses in the chamber could exit out the intake since the pressure is lower than that of the exhaust. This would be a bad thing.

As for you're idea, I'm not bashing it, personally I think its great. I just don't want to be the guy to do it.:)

Lets all admit, we WANT to see results from extreme cams. The whole point in of these tests in my view is to see just how far we can push the envelope in the name of performance before risking the structural integrity of our own motors, all at someone else's risk and expense, totally awesome.:chuckles:

[01WS6475hp]

Question for all you turbo guys. I already have a comp custom grind 228/236,588 intake/578 exhaust on a 114 with ported heads and all the supporting goodies. Would this be an ok cam for a turbo.

[qwkgto]

Turbos do not like overlap.

Overlap is good for N/A because you can use the vacuum created by
out flowing exhaust to help pull more air in.

But in a turbo set-up the turbo creates a certain amount of
exhaust pressure in the system. At higher boost pressures or with
too small of a turbo, back pressure can get high enough to actually
stop air from coming in. This is called reversion.

Turbo cams can have high lift and duration, but they need a high lobe separation.
LSA of 115-117 not uncommon on tubro cams, where N/A cam might be 110-112.

Stock cams actually usually make nice turbo cams with their high LSA's
+110% i am running the ls2 stock cam..

[qwkgto]

Yes I wish some one would do some testing on a dyno with a bunch of differnt cams on a turbo motor so we can find out the truth about what works the best...
this all has been done super chevy magizine has done lots of them im sure others have as well,trust me when I say FI cams do work otherwise why would places like comp cam grind so many.makes perfect sence valve lap is not a good thing when you want to keep pressure in the cylinders in any FI setup.