I think that turbo is a bit small as well, but you would ( I think) need way more waste gate as others have said.

 

Oh WOW, that turbo is WAY to small!!! You need to size the turbo for what the motor is WITH the blower. A 408 at 13psi from the blower is like having a 767ci motor and your trying to feed it with only a T70, which is to small for a 408 without a blower, . Your so far off the right side of the compressor map of that turbo its starting to come around to the left side again! You need something like a PT88, or a GT91 or 2 T70's. Doesn't mater where you put the WG, but your trying to force a LOT of exhaust though a tiny turbo that your only asking for a few psi from. It needs to bypass a LOT of exhaust. I'd get another 50mm gate and put it right next to the one you already have.

How much boost do you want to make and how much power? Give me an Idea of what you want out of this setup and I can help you get to there. I know what it takes to do this, been there done that and I did get it to work ok, just wasn't exactly what I wanted and money from the blower was better spent else where at the time. I do have a "spare" cheapo Roush tvs1900 laying around again, so might get revisited another day,

 

I no its a small turbo for the size engine but its not the only thing feeding the engine, as you said 7 lb blower pulley and 5 lb wastegate was already way to much- so why the need for the bigger lagy turbo?. I can tell by driving it no matter how small it is it definetly has more than enough capability to make what I want which would never be more than 20lbs. I will order another wastegate and get my pulley changed.

 

Mason if your using the same spring in the wastegate that was in it when I sold it to you it is a 8lb. spring. Stock is 5.7 spring. I have it in my hand if you want me to send it to you I will just email your address as I don't have it anymore. Don

 

Don thanks and that would be great. Ive actually been looking everywhere for the other spring to see what I currently have in it.

 

Oh, but the turbo is the only thing feeding the motor AND blower. Your compounding. You got to think of them as 1 unit because to the turbo they are. EVERYTHING going through the motor and blower has to go though that little turbo first, right? So its gotta feed all that air and then add enough to it to make another 7psi on top of the 13 your making now. That's a **** TON of air your asking for from a small 70mm turbo. You got to be over spinning the crap out of it!

I didn't just give up on my compound setup, I spent a LOT of time researching and trying things to get it to work as best as I could.

I did get my setup to work pretty good, but this is what it took to run 13psi on a 346ci motor (MUCH smaller the yours). BW T76 turbo with a BIG T6, 1.36 a/r, 96mm turbine wheel, feeding a TVS 1900 supercharger with a 3.3 pulley that makes 7psi of boost on it's own. Then I had a 50mm WG and 38mm WG, both with 5psi springs in them. Could finely get some control over it with the boost controller then.

Your motor and blower at 13 psi are consuming about 70lbs/min with everything be figured at 80% efficient. Look how far you are off the Map of a T70 you are at a PR of 1 to start with. SO then you asking for another 15 or so lbs/min at only a PR of about 1.4??? (that's what it takes when multiplying PR's to get total pounds of boost to 20 psi) You now at 85lbs/min at only a PR of 1.4 on the T70. See what I'm talking about for being too small??




IDK, maybe you'll figure out something I didn't but I tried a lot of things and this is the stuff I came up with

I think if you added a second T70 right next to the one you have and drop the blower boost to about 9-10, you would be about where you needed to be for the air flow and PR requirements out of 2 T70's. You need to get them turbos up where there working and not just passing air

 

Kb, Im not saying your wrong im just saying thats whats on there now. I purchased the sts kit used from a forum member and installed it to get started. If it needs a different turbo then oh well Ill have to buy one. The only reason I didnt want a top mount was because theres already to much under the hood heat as it is. Is the turbo or 2nd wastegate something I could purchase from you? Working and being absolutely as efficient as possible are going to be two different things, If this baby turbo produces way to much already only see it amplifying the problem but I must first tone down the boost through the pulley and wastegate spring and then make changes.

 

If you want to try somthin cheaper install a manuel ajustable cutout.Makes sure it is placed before the turbo.It will technically be a bypass around the turbo.I say bypass cause,noise will be an issue if it was left open to the atmophere.You would need to try some adjustments first to get back pressure at a reasonable level but, in theroy it will work.This would allow you to keep the setup the same while utilizing the extra air from the little turbo.

 

It's not a problem man, I LOVE doing stuff like this! I can get you the stuff it will need, if you want to call and talk about the setup, I have some ideas.

My number is 480-785-6132

The thing with that small turbo right now, is your over spinning the crap out of it. Probable well over 100,000 rpm... Your back pressure has to be though the roof! How long ya think it's gonna last doing that? You want to try some thing, take the spring clear out of the WG so it clear open all the time. I'll put money on it spools and the boost just keeps climbing just like it does now.

BTW, what do you have for intercooling on this thing? Do you do your own tuning? How are the IAT's? How much of a fuel system do you have? Just some FMI questions,

 

Ok I got a photobucket account and uploaded pics now what !