I would go with the 230XL. I tend to see better results with dual pattern cams. At least on my GN it runs better. I went with a similar cam also.

Jose

 

Do you think that much valve overlap would be good for the engine? I'm worried about the back pressure from the pipes being really high. The turbo tubing is far from ideal and I don't want to have that hurt the engine.

 

First what size tubing are you using. Second with that A/R on the turbine and the physical size of the turbo itself your probably going to get some reversion yes. But you do plan to upgrade, so a 230/230 duration cam won't be bad. Now if you plan on sticking with that turbo for a long while, then I would use a reverse split duration cam just for that fact that it will keep the motor from getting exhaust gas back in the CC.

 

Ok, if I upgrade turbos then my exhaust backpressure will go down? Now I thought the T series turbos used the same turbine housing as the T4's did. Or are you just talking about going to a higher a/r .96 maybe, higher?

 

Well its a little of both. The A/R needs to be at least a .96 on that 60-1 first of all. As far as the turbine wheels on the T4's well they vary in size greatly which also effect backpressure greatly. For instance a 60-1 is flowing through a 2.4" wheel, vs the 76 flows through a 3" wheel.

Jose

 

A .96 with that size motor you will never make it past 12psi. My T76 had a .96 a/r and my back pressure was like 1-3 ratio. The most boost I got was 11psi because of it.

 

Sleeper, I think your problem was mostly the header setup. The turbotech kit just couldn't flow anymore air. Jordan had a 76 Qtrim with a .96 and he was easily able to go over 11psi. Also Jim was running a GT80 with a .96 I think for a while and 1.30 and he didn't see much of a difference even at 18-19psi.

Jose

 

SleeperZ,

Could you give a little more explination as to why you couldn't make more than 11psi with a .96 a/r? This isn't making sense to me. But lets make it short not one of those what spins a turbo conversations. I know we don't need to turn this into one of those threads.

Thanks


Don't you just love a bunch of guys that don't keep busy at work and talk cars all day

 

mine would go over 11psi easily, but there was some SERIOUS backpressure.. never measured tho.

 

At 11psi manifold presure, my exhaust presure was 35psi. Thus the turbine could not spin any faster. No more boost for me=bunk turbo tech kit=2 pist off seasons...

 

I hate to think what mine was at 18psi No wonder why the heads kept leaking coolant!

 

I understand that there was alot of back pressure but what's the fizix behind limiting the boost? Can it not flow emough air at that pressure to get the turbine to spin? If that's the case I'm not sure now lesser back pressure would help. Does it start leaking from somewhere else causing less air to go through the turbo? There's something I'm missing about this 3:1 ratio that isn't making sense to me.

How much HP was your car making on 11psi??

 

Fixing the back pressure issue with turbo tech would be:

A. Getting larger manifold tubing
B. Get a much larger turbine housing (it comes with a .68 A/R 60-1 HiFi turbo) I looked into this with turbonetics and your pretty limited with the on-center housings. You could step up to a 1.30 they told me!
C. Add another, or get a bigger Wastegate
D. $hitcan the turbo tech kit and do a tubular setup

 

I've been thinking about the whole backpressure issue on the turbotech kit. If the backpressure were so bad with the TurboTech kit wouldn't you see massive amounts of boost creep?

 

I did! Had to upgrade the downpipe and wastegate to solve it.

Bill