That's very similar to what they recommended to me. One of the benefits of a reverse split is that in a street turbo appl. the exhaust back pressure is usually more than the intake pressure. If the intake and exhaust valves are open at the same time, the exhuast will reverse and go back into the cylinders. This is called reversion and a the reverse split and wide LSA aim to eliminate this.

Comp cams has a different view on this though. Its quite the opposite.

 

It depends on who you talk to there. Call back 5 minutes after getting a recommendation and talk with someone else, see if you get the same rec.

 

So true, I was going through my notes from over a year ago when I did my cam swap. I talked to a different guy and he recommended the same off the shelf cam for my NA setup as another guy did for my turbo setup.

 

If the backpressure is that much to cause reversion, then it seems to me you would want to open up the exhaust. Not compensate for it with a cam profile. Anyway I think I have it narrowed down to a couple. Tell me what you guys think. Keep in mind in a few months once the savings account builds back up I will be getting heads, probably AFR mongoose 205's with 76cc chambers to lower the compression.

Thunder Racing Custom Split Pattern Camshaft for Nitrous/Supercharger applications- 224/227 .563/.569 114 LSA (This cam will check in the 226 range on the exhaust lobe.) 2200-6800 RPM Power Band. Excellent mid-range & high RPM power. Automatic cars require computer tuning and it is recommend for optimum results.

OR

Thunder Racing Custom "CheaTR" Camshaft - 214/230 .601/.578 117 LSA. Off Idle-6800 RPM Power Band. Broad power range. Works well with stock exhaust manifolds and catalytic converters. Stock like idle. Minor tuning required on automatic transmission cars.
The CheaTR would idle considerably nicer, but the other seems like it would be downright nasty....I like nasty.
Plus there is that pesky thing known as smog test I have to pass here in California.

 

You're pushing it with 224+ duration on a vehicle you expect to pass smog.

 

Do you think the CheaTR would pass smog? Is intake duration the important factor for smog or is it exhaust or both. What do you think the limit is?

 

Overlap is a determining factor, not necessarily duration for smog. Lots of overlap at low lift bleeds off cylinder pressure, but at the same time dumping unburnt fuel out the tail pipe. The Cheatr cam is your best bet for passing smog, but I'm not saying it will. It won't lope, where as the other one will, which is a dead give away to the smog police that you have a cam.

You can't open up the exhuast on a turbo vehicle, because there's a turbo there. You WILL have back pressure no matter what. The reverse split aims to put that to use. Talk to cam motion about it some more, they can explain it better. That's what they do.

 

OK I have talked to Lingenfelter and they recommend the GT2-3, 207/220 .571/.578 w 1.7 rocker 118.5 CL

Comp Cams says with the rear mount turbo you want a straight pattern so as to not cause reversion. They recommended a 218/218 .563/.563 on a 115 with 4 degrees of advance ground in. It is ground using their Xtreme Lift lobes.

I am leaning toward the Comp Cams straight pattern for now since all this dual pattern/reverse pattern stuff is confusing me and everyone has different opinions on it. I figure a good straight pattern cam will make good power and I will be just fine.
On the flip side of the coin Lingenfelter has been doing turbo motors for a long time and if they say the GT2-3 would be good, then it probably will be.
What to do?????