I have a built LS3 with an On3 kit using a Turbonetics 75/68 billet BB unit and CompCam 239/251 620/632 122+4

First time I had it tuned with an LS9 cam, it topped out at 620whp and the tuner said the cam was limiting factor. I had a feeling it was the 68mm turbine wheel, but he seemed so confident it could make way more power with bigger cam I fell for it and it made a whopping 20 more hp with the new cam. Now, I feel like I have a ton of hp left of the table because of the small turbine wheel.

Coincidentally, there is a guy 20 miles down the road selling a near new Turbonetics 78/75 BB, but the compressor wheel is cast. I'm thinking the F1-75 turbine wheel solves a good bit of the back pressure problem but I am worried it will spool slower and I could end up in a worse position with less "area under the curve."

From what I understand these Turbonetics units only have a hybrid BB/journal bearing and don't spool super quickly anyway, so the spooling difference could be negligible. I would not pick the 78/75 if I were buying a new unit, but the cost to change is probably only a couple hundred bucks after I sell my current turbo.

Given this is my first turbo build, I'm looking for someone with experience who might have a better idea of what to expect from the change.

 

While changing to that turbo will indeed help, you would be better off getting a new unit with even more turbine. My advice is to get with Jose at Forced Inductions, or Reed at Work Turbo to get a properly sized turbo.

 

I've looked at both of your threads, I think the real question is how much power do you actually want, and is this a dedicated race car or also a street thing? Going from one turbo to another without an actual power goal in mind seems fruitless.

 

The car is street/strip. It's my daily driver, but I work from home, so I use that term loosely.

The original goal was 600-650 and use nitrous to get well into the 10s, but now I put this new cam in and I feel like the turbo is too small. The hp peaks at like 5k and the cam is just starting to work hard at that point. I don't see any reason this setup could not pull 700 with the 78/75, but will there be a big difference in spool up. I'm thinking probably not and for the cost, I should just give it a shot.

I'm sure I could put new injectors in, install a better fuel supply, change to a T6 kit with much larger turbo and bury 1000 hp on the dyno, but honestly, if I go under 10 I'll have to put a roll cage in it and I don't want that, at least yet.

Right now, I'm looking to build something that would be competitive in Ultimate Street Car or Modern Muscle classes.

 

Just to close the loop, Jose confirmed what I thought. With the cam and the LS3, it really needs a T6 opening and bigger down pipe. Since we are not doing that, I'm pondering what 75mm turbine turbo to put in it.

 

Who spec'd your current cam? Im personally not a fan of the huge lsa, but that aside, the 75 turbine would be a huge step in the right direction and won't be laggy imo. The 122 should help the turbine restriction.

 

No one spec'd it. The tuner said it needed more cam to make more power up top and a guy was selling this one NIB on LS1tech. I was running an LS9 which is a couple steps down in lift and duration, so I was not just going to go a little bit bigger to solve the problem.

Based on what I've learned, I'm looking at enlarging the dp and going with a CT 76/83.

 

I finally got finished with a dyno tune. I went with the Comp Turbo CTR76/75 oilless and made 710whp@5800, which is exactly what I was looking for. Torque curve was very flat and it continued to make 700+ well past 5800.

The CTR76/75 also has way better bottom end than the smaller Tnetics. So far, a great turbo. I'll update after I go to the track.

 

I have a gen 5 Camaro with stg 2 tuner kit and and btr cam 222 231 @ .050 112 lsa 108 ICL we have the same goals I might even like your smaller turbo the stg1 love to here how your spooling or 60 ft times any info would be awsome

 

Spools around 2500 and way sooner and stronger than with the Tnetics 75/68. Car used to lug and want to stall leaving a light. This turbo makes the car much easier to drive and has 75 more HP along with more area under the curve down low.

I'll post some 60ft times one I get it to the track. Right now, I'm wanting to drive it for a while.

 

Thanks very helpful appreciate any info you pump gas or e85

 

Pump gas. Love E85 in my mud truck, but did not want to replace fuel system on the Camaro. I have a ZL1 pump with Ken Bell BAP. Can't get over 560hp without BAP. With BAP pressure topped at 62# and stayed through 6500.

 

How much boost

 

15 pounds

 

Sorry another question what fuel watermeth race fuel e85 I think you had a zl1 pump and bap

 

I'm sorry you answered that this is a stock bottom end 6.2 15 psi no water meth must be low timing either way great tuning job I would say

 

I will try to copy or come close