A couple weeks ago I got the blue truck tuned. The turbo system is a Trick kit. I originally ordered the kit for a 1000+ hp build, but by the time I got taxes paid and the truck got done nickel and diming me to get it done, I didn't have the cash to build a motor solid enough to hold 1000+ hp. So I bought an on3 76mm turbo to run on the 4.8 for a while. The turbine is 65mm and the housing is a .81 a/r. Awful small.

When I got the truck tuned, it made 508hp at the tires on e85 and 15psi. Is this about normal or is it kinda low? I've read many write ups about 4.8's making 600-700hp on a small turbo like I have. Is my turbine housing too small? Even the tuner asked why the truck wasn't making power. The long block is all stock except for a TSP 220 cam. Could it be lifting a head or pushing thru the head gasket, since the head bolts are stock? I haven't got to drive it enough to be able to tell if its burning off coolant. Any help is appreciated.

 

I made 578rwhp on 12psi with a borg S475. Your numbers do seem pretty low. It would be pushing water if it was lifting the heads.

 

That 65mm turbine wheel is what is holding you back big time. Get one of On3's bigger turbine wheel turbos and you'll make more power on your 4.8, you'll just have more lag.

 

i just finished the tune on my 4.8 yesterday and made 626/599 at the tire with an on3 76mm with a .96

specs are in my sig.......

http://youtu.be/xczCZG6JXZc

 

Good numbers for 16psi with the On3. Your truck is sick man!

 

Could fuel pressure be a cause of low power? Not atomizing well enough? Only running about 40psi base pressure.

 

What was the torque and when did it peak? Small turbos just cant carry a big engine through the upper rpms but will make torque very early then crash.

 

/\ What my truck does cause I believe I have that same turbo but on a 6.0. But Id rather have low end than top end

 

Mine does the same thing, torque falls way off by 5000 rpm or so.

 

Take it to the track!!! Too many variables between different dyno's. Trap speed is always a better indicator of horsepower.