Turbo Sizing Q

[Nasty Nate]

Hi Folks,

I'm having a hard time sizing a turbo for my 4.3 V6. I want to make the power output linear as possible since the main application for this frankencar is road race and weekend street cruises. I have a few options picked out: Twin Big 16G, PT67, Twin scroll GT4088, or finally twin scroll GT4094.

I have an rpm limit of 6800ish, very well flowing heads (311CFM In, @ 241CFM Ex @ .600), 6 speed T56 that will keep the car +5000rpm shifting from red line, would like to have full boost 3500RPM-3800RPM.

Compressor Maps for each setup (500whp & 600whp)

Twin 16G
500WHP

600WHP

-----------------
PT67 (T66)
500whp

600whp

-----------------
GT4088
500WHP

600WHP

-----------------
GT4094
500WHP

600WHP

------------------

For the twin scroll turbines, I'm planning on running an exhaust setup like this:

-------------------

My initial choices are the twin 16Gs for a linear, good spool, decent power band. They won't be optimal, but damn close. I think the 4094R is on the larger side, and with the total piping volume and heat loss - I'm worried it wouldn't be a very good street turbo, but the high end would be the best out of all the choices.

Thoughts? Comments?
Thanks,
NP

 

[vortecfiero]

Re: Turbo Sizing Q

im liking this one

far away from the surge line
peak torque seems to be right at the highest efficiency
it has room for higher boost
and never dips below 70% across the range which means cooler boost and you may
be able to run a higher boost setting

 

[denny]

Re: Turbo Sizing Q

Second for the 4094R, I was this close to buying one.

 

[Tooky]

Re: Turbo Sizing Q

Hey NastyNate, this might be the first time I have seen someone ask for a turbo recommendation here using charted compressor maps with the anticipated flow!! Great stuff..

Can I ask what you are using for a block and crankshaft for your planned 6800 RPM? It sounds like a real beast!

 

[vortecfiero]

Re: Turbo Sizing Q

forgot to ask
are you using softwear to plot and draw those maps ?
Ive been using turbocalc for years but i am always on
the lookout for newer or diff program

 

[turbodig]

Re: Turbo Sizing Q

Not to throw more muck in the water, but a pair of GT 28Rs (like a 2860 ) would be a pretty good fit too. And, the off-corner boost response would be almost binary.
(Maybe a little too good, although you could modulate that with your right foot)

What's it wiegh?

I would recommend the twin configuration for what you're doing though. Unless the car is light enough that you want a little more lag, to keep from being too squirrelly on the corners.

Twin 28rs on a light car would be a smile that you couldn't pry off your face.