Truck:

1999 4.8L RCSB (4860lbs + 285 for me)
KBRacing hot side
eBay FMIC 31x12x3, 3" cold side all the way
BW S372, 72 comp, 83 turbine, 1.15 AR
4" dp for first foot then 3" all the way to a Magnaflow then (2) 2.25" outlets
1000cc injectors
E85
Twin Walbros
LS6 cam
Patriot dual springs
LS9 gaskets and head studs
4L80e
3.73 gears
33" tires
Circle D stall

I finally got to the track last Friday. First pass:

1.86 60'
8.7@87 (1/8th mile)

Left it in 4 wheel the whole run. I let out after the 1/8th because I forgot my helmet.

I borrowed a helmet from a buddy (Thanks Darryl!) and made a full 1/4 run. I botched the launch. Run 2:

2.3 60'
13.0@108 1/4 mile

I am currently running 18* timing and about 17psi. I really thought the truck should go a decent amount quicker than 108. Fuel was about .75 lambda (11.2 or so on a gas scale).

Thinking I had backpressure issues, I put a cutout on last night. This went right on the end of my downpipe and made my wastegate an open dump as well. I took it out and didn't see any boost increase (Maybe 1 psi?) and AFR stayed the same. Truck didn't seem any faster either.

I'm currently reving it out to about 6100. I don't appear to be blowing the the converter. Everything looks right. Just doesn't seem as fast as I think it should be.

Any ideas? I'm going to boost leak test again. I may yank the FMIC as well and see if it makes a difference.

Let me know what you think!

Adam

 

Do you have a compressor map for that turbo? What plugs and gap?

 

I can find one and post it. Plugs are Br7ef @.025. I don't feel any blowout or hesitation.

 

BorgWarner S400SX 71mm Turbo S372 (179171) - Full-Race.com

 

The good news is its definitely gonna be a beast when you get it sorted out. Nice setup.

 

that turbo should be good to every bit of 700whp... so i dount thats your issue. the 3.73s and 33" tires and some tall gearing, but that shouldnt kill you like that. i would expect solid 11s out of your setup aty least, so somethign is definitely not right. everything youve said seems to check out, except your ET... running a boost controller? what are you IATs?

 

IATs were under 110*F. Halman Pro BC. Boost was a consistent 215kpa through the whole run.

I've seen issues with clogged eBay intercoolers. I'm going to yank it and bypass it and see what happens. I really don't know what else it could be. Tune looks mint in my logs. According to some basic calculations, I'm only making ~440whp. A 4.8 with 15psi from that turbo should be over 600whp.

 

Can't wait to see what this thing really runs. Good luck. Wish I could help

 

i would think an ls6 cam would be good for more rpm?

 

33" tires, 3.73 gear, 4x4 truck, betting it's lifted too..... Only 18* of timing on E85.

I think your times are not too bad considering all of that. If your second run would have 60 ft better, it would have been mid 12's. Tuning may get you into the 11's, hard to say, but that tall tire & gear isn't helping you.