Hmm. That sounds like an exhaust leak to me, but it may be a function of rpms. That's a monster turbo for a butt mount.


Absolutely there's more in it, but its probably going to be above 4000rpm no matter what you do with the cam. That's just big for those cubes and a rear mount. There are some 408 guys running 88s on an STS kit, but they spool up in 4800-5000 range.

Yes, the small housing is why it's choking up top. Go to the 96 and you'll carry boost and power through 6500rpm at least. I don't think there's much you can do to lower the onset of the boost, however.


Your spool time looks fast as hell to me. It's just a high spool turbo in that application (its fast, just delayed). Your graph shows it spooling up lickity split once it starts.

What a torqueier cam will do for you is make the <4000rpm range a bit more fun, but I don't see how it will move the onset of boost down all that much. If you can find a cam that makes your low end exhaust pulse significantly stronger, it could make the spool start sooner, but I'd think you'd be trading low end for choking the turbo on the high side again. Plus I'd think it would be such a serious exhaust bias that you'd end up with exhaust pressure problems...

Why not just give it some squeeze and go to a 3k or 3500 tcc?

 

larger A/R with a nice 3800 stall and a 75shot off the line. then hold on and point truck sideways so it goes straight once hooked lol. but seriously try this setup

 

I would go 215* or smaller @.050'' 114* lobe center. 220* isn't too bad but if it were me I would go smaller. A reverse split won't bleed off boost, and hurt low end. If anything it should do the opposite.

 

If everything is right he shouldn't need a shot off the line. I agree with the converter though.

 

Oh yeah...forgot about that! My boost is referenced from two locations, the intake manifold and the compressor outlet! They T-into each other and I get an average of the two! Haven't gotten around to changing it but I don't know how it ended up like that! Like I said I've been to some shitty shops!


Yup, that is exactly what my truck feels like, I have to push through alot of dead RPM's to find my sweet spot and then it's over in a flash and next thing I know I'm doing 105mph and slamming the rev limiter.
Found a vid floating around of me racing a bug(YES he did get me in the first 1/8 mile but I caught and passed him), that's some consolation right. Just look at my low end, and then realize I trapped 110mph. Best trap so far was 114 at like 14.3 or something like that.
http://smg.photobucket.com/albums/v6...7_01_23_36.flv


I do love my converter, and I just sold my 3000 Vig to Jarrett so I'm staying with this one. And reason I'm doing all this is to improve the down low, not the top end. I know if I change the top end I'll find more power, but I don't want to go that route, I'd rather lose power and gain some low end. Like I mentioned earlier, don't want to set this truck up for drag racing, I do if for ****'s and giggles but I'm not looking to break any records with this pig. If I do I'll turn it into something totally unstreetable!

 

Changing my cam will effect my low end torque but won't choke down the turbo BEFORE the A/R does. With the A/R that's in there right now it doesn't matter what I do cam wise or any other mod because my power will die right then and there regardless. If I change the A/R it'll be a different story and then the new cam would choke the turbo down. So I just want to see what will happen down low should I change my cam. Engine alone will give me more TQ, and it'll be interesting to see how the turbo reacts to that extra low end TQ, maybe she'll pick up the pace as well.

I thought of that but it would be practical for me on the street, I'd go through 2 bottles a day. To make this a fast track truck, the higher stall and shot is the way to go, to make the truck more fun on the street and still competitive on the track, I think a cam change is the better way to go.
We'll see though, nothing set in stone.

 

Have a good tuner check for any limiters in your tune. There was a time when mine would not spin the tires...it was embarassing at the track. 60/80 ft out it would rip the tires and take off. dc justin got my stuff straight it was like night and day difference...might be something to look into.

 

I had no idea it took off that slow. I mean no offense, but that's terrible. JK. Like I said before, I suffered from similar issues and yes the tune should be looked at. Just because you're at 4psi which is boost doesn't mean your AFR should be 11.5:1. It might be real lazy and not want to rev.

 

Before you do any surgery (cam swap) try figuring out what is up with the boost. I have a feeling that whatever is controlling your boost could be hurting you.

I would also consider bumping up your rev limiter so you have more time in each each.

I'm really surprised you're having trouble turning the tires over. My wife's 96 Quad4 Olds Achieva could do a burnout (with the parking break engaged.)

Have you considered adding a linelock?

 

Or a linelock to build boost at the starting line.

Sounlds as though you have too much turbo for what you want to accomplish.

2.48:1 1st gear ratio of the 80e and the 3.42 make for unexciting launches, esp with you only stalling to 2100rpm at WOT with a 2600 rpm TC.

If you insist on using such a tight TC, you will need a smaller turbo to build boost at lowest rpm AND a smaller cam. The turbo and cam is designed for higher rpm power, while the trans 1st gear and 3.42 rear gear and the TC work best with a high torque at low rpm. Big combo mismatch IMO.

Your peak torque is at 4200 rpm and your TC only stalls to 2100rpm (actual)even though its a 2600 rpm stall. For max acceleration you wnat your TC to stall at peak torque or for a more streetable combo from 1000-700 rpm below your torque peak.
Your turbo is spooling quickly, its just too big to be effeicient at your 2100rpm stall speed. Your TC is understalled bigtime. You didnt liek your 3000 Vig, maybe you should try a 3200-3600 Yank?

Is the tune spot on?

peace
Hog