nlpy8b

Hi,

Anybody have experience with comp turbos for a set of twins?

I just received a recommendation/quote for comp CT3 5756 turbos. They appear to be rated at 550hp ea.

Looking for a VERY responsive set of twins for the conversion in my sig with a stock LS3 and GT11 cam. It'll be a 6sp about 3800lbs with a goal of 650/650ish on pump.


I was originally looking in the 58-62 range max but everyone is giving me advice of going AT LEAST 62mm. I obviously want to keep them as small as possible for my goal but also don't want to cause too much BP or not reach my goals.

Any 2nd opinions or even better experience with comp turbo twin setups?

Thanks.

wrp

I went with the Precision 6266 using a .81 AR to help spool. We've been sitting around looking at the car playing stump poker since May so we haven't gotten it assembled. I did see a vid where a guy with a 427 Camaro made 850 ish with the precision units.

Blackpanther99

iTrader: (8)

What are your HP goals?

I think the PT6266s will do a legit job and have a little extra room for more.

Anchor

Be careful, comp have a history of under-sizing when quoting for us V8 crowd.

wrp

I think Precision is pretty overrated too. 850ish on a 427 seems a little weak. They were estimating my 408 getting 1000+ but I have not yet seen an example of them producing that kind of power, (the 6266). My guess is 850 ish is probably their comfort zone. My builder believes them, hope we can see someday.

nlpy8b

Thanks for all the replies. I was actually originally recommended pt6262 turbos. Almost all the twin turbo kits for LS3 Camaros are sold with approx. 58-62mm turbos so this is why I was looking in this range for a good "best bang for buck" turbo.

Although I want them to be very responsive I wonder if the CT3 5756 wouldn't be just a hair too small?

Anyone here have experience with any comp twin setups? I saw Westtexasbuff build, but it looks like its still in the works with some 6767 turbos.

toytech93

iTrader: (2)

I would follow their original recommendation. I would recommend 6062. I was recommended Billet T4 6265s and things have been snowballing ever since.

Superman09

iTrader: (65)

Be sure to contact us when you are ready for a pair of Comp's or whatever turbos you decide on for the best pricing For the Comps, I don't think they are too far off for what you want the turbo's to do. Your HP goal doesn't need anything crazy for turbos that would sacrifice spool time. Being a 6-speed as well, I would go something in the 5858 or 6060 range which will more than meet and exceed your power goals as well as spool quickly for you! Let me know if you need anything else, be happy to assist!

nlpy8b

Where are you with your build? I know your setup can afford to be a bit bigger with the built motor and auto, but it shouldn't be too far off base. What are your goals?

Why did you chose billet over the BB option?? Why not both? I know BB helps with spool and it seem the billet versions are more efficient, would going billet help with spool as well due to decrease rotating mass?

nlpy8b

Thanks again for your quote and military appreciation!! You'll be hearing from me soon I assure you. I just want a few second opinions on sizing or some real world results but it doesn't seem easy to find them anywhere on the web much less here on ls1tech.

Your quote/recommendation was for the ct3 5756 turbos. This was the size I was looking for but then came across the very poor recent results that denmah had with ebay 6162mm turbos being too small for a 6.0

Maybe comparing ebay/Chinese turbos to Comp turbo is a poor apples to oranges comparison??

I'm just a little gun shy due to the amount of $$ involved and don't want to buy twice.

yelo04goat

iTrader: (11)

cant compare the ebay stuff to others. really. i got a buddy with a comp 91 and loves it

Blackpanther99

iTrader: (8)

Hard to choose turbos now days with all the issues the manufacturers are having.

smokeshow

iTrader: (17)

I feel like those turbos have got a bad reputation because of denmah's results with them. My 6.0 truck made consistently over 900hp on an eddy current loaded dyno at 17psi with the same turbos. This is what happens when the cam is far too large. High backpressure from the turbos makes it difficult for the cylinder to evacuate all of the exhaust. When the cam is too large like his was, it becomes far more difficult to get rid of the exhaust. It can also induce a negative torque on the crankshaft because turbo drive pressures can often be at a ratio of 2:1 with boost or higher. All of that pressure just pushes against the piston as it comes up to push exhaust out. Not good for making power.

To fix this, you either have to go huge on the turbine housing at the expense of turbo lag, or you have to downsize your camshaft at the expense of your car not sounding as 'cool'.



Stock LQ4 at 17psi with those 6162 turbos, Isky triple 12 camshaft, 4L80e, unlocked Yank converter. 17psi at my elevation is 210kpa manifold pressure.

nlpy8b

Thanks for your post. That sheds so light and eases my worries a bit. My cam is a gt11 which is basically just a ls9 cam with more lift so hopefully this won't be a problem for me.

Any reason your torque peak occurred so late at 5k rpms?

smokeshow

iTrader: (17)

I didn't start building boost until 3000rpms, so it wasn't at full boost before the cam's torque peak came by. I started later so it wouldn't downshift to 2nd. If I had been chasing numbers I may have tuned it to hold 3rd at a lower rpm and had the dyno loaded a little more. I wasn't expecting that much power anyway, so I was pleased.

Your cam is a bit bigger than the LS9 cam. The exhaust duration is set more for a low backpressure application. I think you can reach your goals with that cam, however the turbos you'd have to use to do it will likely not net the fast spool time you're looking for. I've seen the LS9 cam in action in several turbo applications, and it takes quite a bit of RPM to make it sing. Translation: turbo lag.

jt76

iTrader: (10)

I have a pair of precision 6262's on a 370/6sp and 93 pump and mine is at 800rwhp on 12 psi and is instantly responsive. I'm very happy with my turbos.

code4

iTrader: (30)

I have twin ct3 6265's on a 346 ci. They are the non billet entry level for $675 a piece. The car is ridiculous on the street at 13 lbs of boost on 325 50 15 DR's
Here is a 60 MPH roll by:

wrp

What AR are you running?

I guess that smoke is characteristic of the twin setups? Or is that tire smoke?

nlpy8b

Billet PTE6262 turbos were what I was originally recommended but these comps looked very interesting after Casey at Huron told me to check them out. Thanks for your response though as these are reassuring me I'm heading in the right direction

nlpy8b

That's awesome, first hand experience with these...exactly what I was looking for. You say your car is "ridiculous on the street" which I'm assuming is very responsive based on your video which is also exactly what I was looking for.

It did sound as though your car is auto though, correct? What power are you making at 13psi and what fuel are you using?

Thanks again.