Thats what im talking about when i say get rid of the back pressure with a cutout.If you use a wastegate to completly control it will be more difficult plus the extra cost.Once you control this you will be able to limit boost.

 

I wasnt satisfied with the amount of boost from just the SC so I pulled the 5" pulley of and put on a 4" When I got the pulley changed I still could only see maybe 5 lbs. I then found that the only silicone boot on the truck which is the elbow on the SC was getting sucked closed.Which with the spring out of the wastegate its clear it made no turbo boost at all, otherwise it wouldnt collapse, even with 1 lb. Thats why it was slower that a stock truck. So I really dont know what the actual boost would have been with the 5". However the actual boost with the 4" is 9lbs which I feel after driving is right where I want to be as far as low end torque. I then figured I would try and start taking off 1 coil at a time on my 5.5 lb wastegate spring and I finally acheived my goal of 15 lbs at wot. I wont know any #'s until I get it out to the tuner.

 

Mine is the 2.8H

 

Cool! I'm glad you got it to make the boost you were looking for. I'm really interested in seeing the numbers it's makes, so PLEASE be sure to let us know. How does it feel BTW?

I debating what to do with this blower I just got, I wanted to play with a blower again on my truck, (I just love that instant hit on the low end, ) but I know with the TVS1900 I was pretty much limited to 10-11psi blower only and I built my motor take about 18-20. I think this blower might be able to reach that on a smaller motor like the 5.7 I have. Maybe I'll just have to compound it again!

 

I dont think you would have a problem even with the small blower. It seemed as the equation was literally multipling the two boosts and it was always close to what it was doing. like right now the 9lbs out of my blower I seruiosly think its only taking 1-1.5 lbs from the turbo to get 15. Ill have to get a gauge on the piping feeding the blower. I also must modify or figure something out on the elbow- if I cruise and roll into it with turbo boost its fine- if not the blower closes it at the blink of an eye because its faster than the turbo. Ill definetly update

 

Ya, the boost doesn't add together, it multiples by pressure ratio, at least in theory. Here is a chart of what you should get for boost based on PR's multiplying. Looks about right with what your seeing.

 

One things for sure, I was never happy with the #s from the dyno when it was sc only, I had it at several different tuners as well. I had even had different 408 shortblocks and at one time had trickflow 225 cnc heads and big cams. The best I ever got from it was like 530rwhp at 13 lbs. It is 4wd and does have a 4l80e and bigger tires, but I always expected more. I like it the way it is now. I was tired of valvetrain noise so I have a smaller patrick g cam, stock rockers and 317 heads with springs locks and retainers only. Sadly I think it runs better now then ever. I dont know what to expect with the turbo but we will see. At the track it would run 12.1 all day everytime, with alot of cool down time of course.

 

that thing is sweet!!!!

 

That's not really what I want to hear... I want about 700 or so rwhp out of blower only! Supposed to be lighting guys with this blower on 5.4's in the 800's... :o/ I have the same drive train as you, Just a smaller motor and bigger truck. I've been low 12 with just a T70 turbo. Never had a good track day with just the big turbo. Best I ever ran with the compound setup was on 13psi and ran 12.6 @ 107 I think up here at altitude (4800', 6000+ DA) I want to be in the 11's easy, as a daily driver and not all striped down.

 

Even with the S480 and quick spool valve you've never beat low 12s with the T70?