GTX4294r or GT4508r for my 20B?
 

I have both. Engine is street ported with a full 4" exhaust. It also has a custom intake with a 90mm throttle body.

The 4508r has a 1.15 rear.

If I use the gtx(ErnieT's old turbo) which size rear should I use? It has to be a t4

I'm planning on using the gtx4508r with the 1.15 housing on my 20b so I will admit im a little partial to that setup because I'm trying to get to the 1k mark. but i honestly think if its a car for the street the gtx4202r is probably more fun in the long run better spool, useable horsepower and effiency range that you don't have to crank the boost real high to get to. just my opinion.

2 or 3 rotor?

Sorry, for some reason I thought you put gtx4202r when you actually put gtx4294r. Based upon that if its a street car I would go with the gtx4294r especially if its a 13b if its a 20b and you want huge numbers go gt4508r even with the 20b i think it would be A LOT more fun on the street with the gtx4294r though. Again, Just my opinion.

It's a 20b which is why I posted it there....either it got moved or I goofed :)

sounds like you making a monster, subscribed.

What's the intended use?

Seems like a 1.15 T4 housing on the 45 would be a little small for a 3-rotor for ultimate power potential.

Use the 45 and sell me the 42. ;)

I have a 1.28 for the 45r as well

I would love to do a comparison but would need to borrow a t4 housing for the 42. :)

45 is way too big for street use, you will never ever be able to use half its power potential with any size street tire. Every 45R 20b I have ever done every owner wishes they would have gone smaller...

What size turbine housing should I use on the 4294?

Still messing with 3rd gens John!!! Hope all is well buddy, go wolfpack!!!

turbine housing would really depend on what you need it for.. so what is the purpose of your setup?

street fd with gtx4294 on a tial 1.01 A/R seem to spool very quickly (Comparing to what i was expecting at least) but again that was a 2 rotor

I want an all around beast

go with the smaller choice, you can always go bigger later

I just need to know what size T4 turbine housing to go with...I dont ant to choke the 42 and want to use its entire power band

what kind of power numbers do you guys think the gtx4508r 1.15 (billet compressor model) will make with the 20b at just under 30psi? At what psi is that turbo in its effiency range?

Carlisi had a T6 4202R on the 20B and it spooled fairly quickly. He was running 12 psi..... when boost came on, it felt like being shot out of a slingshot. I do know he was searching for better response so went with a smaller turbine A/R..... from something above 1 to a 1.0 I believe.

I had a t6 4202r 1.28 on my last 20b and it spooled very fast...just want something different. I will start with the 4508r since it's already mounted.

yeah it was 1.15 :)

thanks rich

what kind of power numbers can you expect right at 30psi with the GTX4508R on the 20b? at what psi does that turbo peak in CFM's?

Answer=a lot

This isn't a gtx45r thread lol

my appologies

I think you'd be best off with the 42R, for an all-around setup it will make better use of your engine's powerband. By my math, at 15 psi and 7500 RPM (pretty close to where your peak power/torque will be) you'll be around 70 lbs/min of air, and at 20 psi you'd be near 85 lbs/min of air, which will be just within the outer island on the compressor map. Any further than that and it might drop off a bit, but you will have more area under the curve, so to speak.

That being said, I wouldn't go any smaller than it, and if you're comfortable with the response of the 45R, than go with it, it will present less backpressure, and won't choke on the top-end.

As for housing choice, I think it will partly depend what your intention with the car is, but I'd say larger on the 42R would be better to not limit your top-end any more than the turbine will. Won't be as big of a deal with the 45R.

Edit: largest turbine housing for the 42R is a 1.44, that's a bit excessive. Maybe try the 1.28 A/R T4 or a TiAl housing. There's a big difference between a 1.15 A/R T4 and 1.15 A/R T6...

I picked up a 1.15 for the Gtx and will run both turbos to compare

My current set up is a semi pp 13B , I run a GT45R with a 1.28 housing on it and spool is fast , its not lightning quick , but its fast ! on a 20 B I think you would be better off with the larger turbine wheel for increased flow , spool time could always be adjusted by changing a/r ratios .I plan to upgrade to a SS Tial housing mainly to try and drop some weight ! the 45 is a freakin heavy turbo ! I'll go down in a/r a bit maybe to 1.15 to see how spool and power is affected. At 10 psi my 13B made 366 RWHP and 300 ftlb at only 6600 rpm before the clutch started to slip!