fif_gen_powa

I have a hunch the pt7675 is the better turbo but curious to see results

1CAMWNDR

iTrader: (21)

How big is the TURBINE blade outer diameter on each? Same? They are both listed as 75mm turbines but I think that is just the outlet/inner diameter. If they are both the exact same turbine then perhaps the turbine is having a hard time driving the larger 84mm compressor wheel.....

Redbull87

iTrader: (3)

No worries,its in my sig. In the middle of putting the engine back together with forged internals.
High mileage 2003 lq4 6.0
317 heads milled .030
Btr 660 dual spring setup
Stock rockers with trunion bushings
Ljms stg 2 turbo cam
Stock ls6 intake with ported stock tb
On3 84mm Billet journal t4 turbo
rebuilt stg 2 T-56 with monster twin disc clutch

Im not sure if im just out of the efficiency range of the turbo or just need a better flowing hotside.Theres alot to factor in. I wouldnt be surprised if a pt turbo with more flow given the same size diameter might pick up some power.

I do know my setup vs everyone elses makes heeps of torque and noses over on hp!

mightyquickz28

iTrader: (8)

Interesting thought. I'd briefly contemplated that aspect. "Same turbine turning a larger wheel? Wonder if that's more difficult?".
Haven't got to make any passes with the 84mm yet. Last Wed got rained out, this Wed (every Wed is test n tune night at Lebanon Valley) is the 4th so I'm sure that's out. Hopefully after that. On the measurement, I'll probably pull off the 84 just to do that and put the two turbos side by side with my digital caliper so you guys can see in a picture or two.

I've still go the twin GT35s to put on this coming Winter but I'm thinking of trying a BW S475 in August since I see a lot of success with the 5.3's and those turbos.

mightyquickz28

iTrader: (8)

This is the main reason my friend took off the ON3 84mm. With 416 cubes, huge cam and log manifolds, it would go into boost near instantly and then fall on its face.

3pedals

iTrader: (3)

The 75mm turbine is WAY too small, even for a small motor like a 4.8.
The 75mm exducer turbine can only do so much work, and now you have asked it to do more by adding a larger compressor to it. It is also probably at its choke point, where it cannot flow any more exhaust through it, no matter what you do.
Put a much larger turbine on the 76 compressor, and hold on

Chicago TDP

iTrader: (3)

So just curious, what would be the next step up for a larger turbine that would work with a 76mm compressor? What is the next size up that will keep the same or similar frame size?

Ratical

iTrader: (82)

If you can find an S475 T4 with an 83MM 1.25 exhaust or something similar I think it will run really good! My buddy had a t6 1.32 on his stock 5.7 Hemi and was on a solid 9.4 pass before a rod decided to take a vacation out the side!

Redbull87

iTrader: (3)

This is my thinking and my tuner says the same.hence why i want to do a full back to back dyno comparison on the same day with no change to tune and see what the motor says

Redbull87

iTrader: (3)

My other question is,comparing the on3 84/75 with a .96ar to the pt which is also a /96ar to me still seems like a limiting factor.it might have marginal gains in the upper rpms for holding power uptop.
Im seriously considering going with the turbonetics also but with a 1.15 for a custom dropin unit.Essentially that is the best route..for what a spent on the bilet 84mm journal turbo..for a few more bucks have a turbo thats rock solid for my combo.

Luke19901

if you're sole on 80+mm compressor and T4 then

S400SXE 80mm borg warner T4 1.10. 80mm comp wheel 76mm turbine
GT4508r Garret T4 1.01 80mm comp wheel 80mm turbine
S400SX3 S475 borg warner T4 1.10 75mm comp wheel 74mm turbine

soloman369

iTrader: (13)

I guess my suspicions are confirmed, ill spec'd combo some of these guys are running for there turbo.

Redbull87

iTrader: (3)

I dont mind going back to a 78mm, especially since size and placement of the small frame of the current turbo is what made me look at the pt and the turbonetics. Going with the borgs or garrets would require me to re-engineer my hotside..and fender clearance sadly

3pedals

iTrader: (3)

You guys are completely missing the real problem.
The turbine wheel diameter is the limiting factor here.
75mm turbine exducer is TOO SMALL!!

Redbull87

iTrader: (3)

This I understand but then Id ask would going to a larger housing aka the 75mm exducer with a .96ar vs a 75mm with a 1.15ar not be any benefit?
If I had the space for a t6 turbo..this wouldnt be an issue Im sure. Does the improvement of flow not help reduce backpressure even though its a 75mm exducer? Im here to learn and understand the pros/cons or if its worth doing at all given the space I have.

This is what Im looking at
https://turboneticsinc.com/store/ind...product_id=565

Luke19901

have gone 850rwhp with T4 S475 with 74mm turbine wheel. 6.0 manual on E85 16psi
same car one new owner later T4 GT4202 with 74mm turbine and 74.x comp wheel E85 17 psi

to compare how much turbine flow helps

6.0 TH400 4800rpm converter S480 80mm comp 88mm turbine T6 1.32 E85 11psi 720rwho
16psi 907rwhp

3pedals

iTrader: (3)

The turbine wheel exducer diameter is the main thing that determines the flow through the turbine. The a/r is more of a fine tuning tool.
find yourself a turbo with at least an 85mm turbine exducer.
There are turbo companies that can fit a T4 housing on a BW 96/88 turbine

1CAMWNDR

iTrader: (21)

Borg Warner S475, 476, 480 with the either of the larger 2 turbines (96mm or 92mm inducer, both 88mm exducer I think) can be had with T6 or T4 and 1.00 A/R up to 1.56 A/R. That is where I would look. Or similar from VS Racing.

fif_gen_powa

These are both T4 turbos with H compressor cover

Comp 78/75 1.15 a/r T4 housing on the right Precision PT8847 (88/84) .96 a/r T4 housing on the left

It's pretty obvious the "larger" 1.15 a/r housing on the 78/75 is still pretty tiny compared to the .96 a/r on the 84mm turbine precision turbo

JoeNova

A/R is a ratio. You can double the area, double the radius, and have the same exact A/R number with a HUGE housing. People pay too much attention to A/R.