Combo Im working on right now.
4.3 v6 , e85 blowthru, mid mount.
Timing locked at 31 deg.

I just did some changes to it.
Previously it had stock GN turbo on it, cam was na design, 224 at .050 110 lobe sep on 106 intake cl
Convertor is tight, like 2000. In this combo boost came on at 3000 like a light switch.

Freshen the motor, tad more compression, new cam, 215/220 at .050 114 lobe sep on a 110 intake cl.
Put a VS 76/65 on it with the .98 housing.
Now it is a turd. Just starts building at 3000 and then acts like a supercharger and wont make peak boost until 5500. Changed to a .68 housing and its a tad better but not enough to count.

I believe the compressor wheel just doesnt make boost very well at slow speeds effecting its ability to come up fast.

So im leaning towards a s366 t4 setup.
Looking at what all the grand national upgraded turbo are they seam to stay in the 60mm range on compressor and t3 housing up in the 700hp range.

Only trying to make 500 flywheel with this thing. But want some average HP, not just peak.
Old GN turbo combo made little of 400 crank but was maxed.

Any experienced opinions on this.

 

I have no real experience with a setup like that, but that 7665 is severely under driven. I was thinking s360, or 366 before I even got to that part of your post... A s360 (or 63) with the the 68mm turbine should give you a nice bump in turbine flow, the compressor should easily make your goals, and spool much better.

 

x2.....I did the same thing

 

thanks guys,
I talked with my turbo guy and he confirm the same. s366 . He said we can force it to spool pretty low and still make our power goals without a problem.

Now I need to get this thing sold to an LS guy that wants to make some power on the cheap. I see guys using these on 4.8 and 5.3 all the time.
And convince my buddy that its what it needs to work good.

 

So which 66? The 80/73 turbine is the most common, but I'd almost be worried that it would be too much turbine for a 4.3 midmount looking for early spool. There are guys running the 80/73 on 5.7 hemi's with some impressive results.

 

yeh my buddies gen3 5.7 has the same turbo. Its lit by 1500.

He was leaning towards a t3 turbine. Dont know what wheel.

 

update.
Purchased a Bullseye s366 street billet, t3 76x68 wheel.
Put this on yesterday. Drove a few miles to get some heat in the system. Right away it was more responsive. At 1800 rpm cruise the turbine is already whining and ready to come right up. I stopped and rolled a few feat then hit it. Turbo came right up to 15 psi instantly and held it solid thru every gear. Night and day difference all around with this turbo compared to the other.

 

Engine breathing lines need to be matched with not only the proper turbine wheel. Believe it or not, the compressor performance has just as much to do with this issue. The exact MPTurbos solution you're looking for is the MXT67/65B.

Unlike the unit you are currently running, this unit is antisurged and comes with a much lighter and higher flowing billet compressor wheel. Flank milled out of A2618 aerospace grade aluminum, a material that weighs around 50% that of the C356 cast aluminum used in your current unit. Please see below information for your reference. Thank you.

By the way this should be a driect bolt-on replacement to the unit you are currently running! T4/Vband turbine with 4inch inlet and 2.5inch outlet...




#ad

#ad

#ad


#ad




#ad

 

Got this thing to the track a couple times.
This weekend it [email protected]
Still has more ET at current boost. Still foot braking it with a tight converter and no 2 step or transbrake.
Very happy with this for what it is.