I currently have a Garrett GT-76 turbo with a 76 on the compressor side and a p-trim n the turbine side.

I was told it was too small for my 408 and that it would choke on the top end and have too much back pressure. I had originally thought about 600rwhp. This is using a Trick low front mount setup.

What size turbo should I get to make 600-800 rwhp? I want it too spool quickly so it drives good on the street rather than a track use only setup. Hoping for low 11's.

Also, how much should I ask for my current Garrett GT-76?

 

Anyone!

 

Not sure on the exact trim or A/R details, but Parish made over 700hp and 1000tq on a 76mm turbo. It will fall off up top, but it will make the power you want.

 

The problem is every 76mm turbo is different. I have a Garrett GT-76 I bought from STS. The compressor size is 76mm and that seems to be fine the problem lies in that it is a P-trim which has a 64mm turbine wheel. Apparently that is too small and will create too much back pressure and as a result will choke(limit) the top end.

On the other hand Forced Inductions has a GT-76 with a 76mm compressor but with a much larger 94mm turbine wheel. This larger wheel together with a bigger a/r would help with the back pressure.

I have been doing some reading about back pressure and since it is directly tied to boost pressure and I only want to make 600rwhp to a max some day of 800rwhp I don't think I need a big turbo. The PT88 and 91 have been suggested because of my 408 but those turbos are capably of 1400 hp which is way more that I ever plan on making.

For 600rwhp what turbine and a/r size would be ideal. Something that will not be too laggy.

 

You should be able to make 600 rwhp on a 408 with pretty much any setup. A 76 should get you there, But like you said will choke you up top which is where a turbo shines. With that said you have to take in account that you are talking 600 rwhp, and rating of turbo is more towards flywheel ratings, and on a perfect setup. I dont like pushing a turbo over 80% of its rating b/c it seems to get out of its sweet spot anything over that. I have made 600+ rwhp with a gtk850, wich is a 72mm turbo rated for 850 hp... It was maxed out, and would not hold higher boost over 4k rpm. I hated it... was great under 12 psi, or under 4k rpm.... but I dont spend much time in that range. went to an 80mm tnetics and loved it. Made over 700 rwhp on the same 6.0, and was not laggy at all to me. then went on to do twin 76s on it and loved it more. If it was me on a 408, I would not run anything smaller than a pt88, or something comparable. Just b/c it will support 1400 doesnt mean u will make 1400. just my .02 hope this helps your decision

 

what would be a good size turbo to run on a 5.3. i wanna go twins

 

kkeeping the revs down to 5800 or 6k will help. 600rwhp should be easy on that setup. torque will be killer. are you against a T6 76mm, like an S76.