Hi Guys,

I am going to be soon ordering a trick performance kit and I am not quite sure if I want the 74mm or 76mm precision turbo. Does anybody have any dyno plots of these two on a 4.8? My eventual goals will be 600whp....maybe more if I get crazy with it later down the road. I do not mind some lag, but do not want something that is too laggy and not fun on the street.

Thanks!

 

Either will get the job done.
Stage 2 = 72/68
Stage 3 = 76/68

Either kit can be upgraded to
74/75 cast wheel
76/75 billet wheel.

For your power level 76/75 is NOT needed.

If pulling any trailer I would do the 74/75.
If not pulling trailer just a fun hot rod. 72/68 or 76/68.

Feel free to call if you have any questions.
940-781-5204

 

Thanks for the reply! Do you have any dyno charts with the 74/75 on a 4.8? I was only considering the 76 to have room to grow if go all out later on.

 

I have a 74/75 on my ride. My kit was originally spec'd for a 1000+hp 370ci motor so everything but the turbo is pretty oversized for a 4.8L. But by the time I paid my taxes and the truck got done nickel and diming me to get it done, I couldn't afford to build the 370. So I bought a Precision 74/75 and put it together. If I can get my tune nailed, I think it'll be a pretty awesome setup. Spools well and makes pretty decent power, even tho the tune needs a little work and maybe a few mechanical adjustments. Granted the Precision costs more, but you get what you pay for.

 

Very nice. When do you hit full boost in say 2nd and 3rd gear and how much boost?

 

A 76mm is huge for a street 4.8L, and not the right turbo for 600whp setup. Go with something like a borg S366. To put things in perspective, I'm making around 800 with a 75/74 turbo. JMO.

 

I'm hoping for 600ish with 70mm on 4.8. Even if I come a little shy I would rather the quick spool for street use vs the 600 goal and having lag with a 76mm.

 

I ended up ordering the 7475 turbo. I will likely be looking for 600+ later on down so it will at least give me room to grow.

The s366 is a good turbo too. I run it on my s2000 making over 650whp. It looks like on higher boost levels with a 4.8 I could potentially be running off the edge of the compressor map though.

 

There is nothing wrong with running off the edge of the map a little when you really crank it up. It will just blow a little hot air then.

I like to build the setup so the majority of the time when you're running it, you're right in the sweet spot of the map and not on the low end. Makes best average power for the majority of your driving that way and not laggy but will still make really good power when you do turn it up.

 

Too bad precision does not give out compressor maps :/