I havent spent the time to finish working out the bug (since it drives) which the only problem is to much boost. I am looking for suggestions in the mean time or maybe even someone just has the answer. My truck has had a kenne bell 2.8 and a 408 for a couple of years and even with 8 ribs and an overdrive balancer my max boost without any slip was 13.5 lbs, any smaller pulley it would actually make it slower.It also obviously would heatsoak bad at the track.So that all got old and I was wanting to do this for a while and was thinking that the supercharged exhuast pressure would really spool the turbo quick and would make the power while not getting the blowers air so hot from spinning that fast. I saw the other post but then it was given up on. Well, my truck is already completely done and Im not going to give up. Amazingly ive done nothing as far as tuning and it runs better now than before. It is a blast to drive but i can only give between 20-30 % throttle, so I shoot it to 15 lbs which is instant and slowly lift off the pedal.From a dead stop I can foot brake to 15lbs and spin in 4x4, it definetly never felt this strong. The way it is now I dont doubt it would make 45lbs if the engine would hold it. Ive played with the boost controller which is a greddy profec b spec 2, set everything as low as it will go but it wont control it. Thats really all ive done but im going to try this weekend to get the bigger blower pulley on it and find a 5lb spring for the wastegate to see if it helps. Currently i have the boost source for the controller coming from the actual combined boost, maybe I should have it at the turbo? I know it will take some time and probably more money but Im not concerned. Below are some specs on the truck and any info or suggestions are appreciated- Mason

03 gmc 4x4
408ci
2.8 kenne bell
4l80e with precision 2600 5 disc
3:73 gears
sts kit intercooled .70ar
50mm wastegate
tial 50mm blowoff
greddy profec b spec 2 boost controller

 

So youve already put it together? I think kbracing tried it a while ago but gave up because of boost creep.

Need pics of your setup ASAP

 

Yes it is together, I have about 700 miles on it now. And I had read all his posts on his setup but he just took it all off and sold it. Im going to get it figured out. I would post pictures but just dont know how.

 

Do you have a photobucket account? If not sign up, it's free.

 

What size turbocharger are you using? (.70 a/r is not a size) You are going to need MORE WG!!!! Trust me. I did get a handle on the over boosting, but it took a 7lb pulley on the blower and a 50mm and 38mm WG bothe with LIGHT springs in them to be able to control boost. My setup with just the 50mm WG would go right to 20 psi with just a 5# spring and 7psi pulley.

A boost controller can not lower the boost any lower then the spring in the WG.

 

And leave the boost reference line where you have it...don't move it to the turbo or your gonna lift your heads or worse. Get some pics up!! Glad to see you followed through on this idea!
Is your truck a RCSB, ECSB, CCSB?

 

Very cool, your making more boost than my Dmax !

Sounds like its insane when you push the pedal.

pics !!!

 

Seems to be the problem most common with a compound...runaway boost. Is it just not dumping enough at the WG? Curious to see if you get it figured out.

 

Thanks for the info. Where do you suggest the placement of the 2nd wastegate and what size springs are you thinking? The turbo is a gt70.
Truck is a factory orange shortbed regularcab stepside.

 

WOW...we need pics of this thing!!! GO TO PHOTOBUCKET ALREADY.... ITS SIMPLE!!!
Please!