Doing some logging and using the torque log in hpt. According to it I'm not making anymore power from low boost 7.5 to high boost 13. Wtf. Is my exhaust side holding me back? It's making the pressure but no power. It doesn't feel much stronger either. Timing is a little lower do to iat but I don't get it.

 

what Turbine wheel and housing are you using?
Down pipe and the rest of the exhaust?

 

Tc78 68mm turbine 3" down pipe to 4" exhaust right under the firewall. .96 ar

 

Seems a little early for the turbine to be running out of steam. 5.3 I assume?

There was a guy who did a test on exhaust back pressure with a 7665 I think, smaller turbine than yours, and it continued to make power up to like 15 psi I want to say, then started to flatline.

I hope yours isn't done for, I just got a TC76

 

Wait didnt you just go 6.0?

It should still be making power.. my buddys 5.3 with a magnum 76 with a 65mm? turbine is choked out past 15-16psi.. it doesnt go any faster on 18psi just heats up the IATs more.
Yours should be in the sweet spot at 13psi. im assuming your AFR and timing were good?

 

I think I may have a boost leak. It does sound kinda whoooshy under boost.

 

I need to update my signature to the 6.0l

 

I would say you are just about done with the 68mm turbine and 3" dp. I switched from a 76/64 and 3" dp to 80/77.5 and 4" and man what a difference! And that's on a 5.3. Your 6.0 should breath a good bit more

 

Yea.. i love my 83mm turbine.. should be good for a few hp.

 

I was thi king same thing. I'm also wondering if 600lbft isn't the max that hpt can log and that's why it looks funny. I I ow its not going to be 100% accurate just using it as a gauge is all. Was on a long striaght road today hit wot on low boost pulled hard then hit high boost and there was a good difference. But high boost has a whoosh noise that low doesn't. I'm wondering if I'm blowing my bov open. I took the push hose off and just the pull hose on but it felt about the same. My thinking is that since the bov is on the turbo side of the cooler and the reference to hold it closed in boost and pull open in vacuum is on the intake itself. maybe the Intercooler is having a huge pressure drop at wot high boost and the bov valve is seeing more push than the diaphragm is from the reference causeing it to open. Hope that made since. Lol