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Discussion Starter #1
Went to the dyno (dynojet) yesterday to my new turbo on moderate boost. Specs are GT42 DBB 71mm version (70.34mm at the inducer) with a 1.01 A/R turbine housing. I ran a GReddy T88-34D previous to this.

I dyno'd a couple times on pump gas previously and yesterday; best #'s b/w 585rwhp to 593 being the highest, boost controller turned off ~ 18psi (spiked a little on low boost).

With pump/race gas mix on ~23.5psi she belted out 698rwhp! A/F was in the 11.0 to 10.9 range taken at the DP. I was pretty stoked with that.:D For comparison, my T88 made 700rwhp at 28psi, 716rwhp at 29psi. To be fair it did not have the benefits that the GT42 does now (T88 was on stock cams, 3"dp/mp, tiny turbo side IC pipes). Big difference in spool though. Mods are:

Stock short block, stock intake, HKS 264 cams, Crower springs/ Ti ret.
Greddy T78/88 kit, now with T88H DP & MP, HKS Ti exh.
Phil Panas fuel system (890cc inj's, stock + Walbro 341 pumps, custom rail, etc.)
Greddy 3 row with custom 3" turbo side IC pipes
G-Force ecu/VPC/Field SFC

I can't wait to really turn her loose on better gas and 28ish psi. Hoping to be around 800rwhp and will be running the car at Maxton-mile in a few weeks. :)
 

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T-Power
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Great # for only 23.5psi! Congrats. :bigthumb:
How much difference in spool? What RPM do you get full boost???

TIA,
john
 

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The GT42 he used is a 56trim GT4294R. IMHO this is a much better matched turbo than the typical GT4202R that is used (76mm inducer). It is good to finally see somebody using it. There is also a 52-trim GT4294R (67mm inducer) that uses a slightly different compressor wheel, but should flow nearly the same.

Now, turn it up so we can see what it's really made of! Good work.

Daniel
 

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But the 1.01 AR is huge. I bet it adds quite a bit of lag. But the results so far are very impressive. 700 rwhp on 23 psi!? Dang! This baby flows!! :)

-Olivier
 

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1.01 is on the small side for a GT42. I would actually try the 1.15. I will be using a 1.06 on my GT40 and may give a 0.95 a try. I believe there is even a 1.2x and 1.33 for the GT42.

Daniel
 

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made by precision? i dont see it on their site


SupraWood said:
The GT42 he used is a 56trim GT4294R. IMHO this is a much better matched turbo than the typical GT4202R that is used (76mm inducer). It is good to finally see somebody using it. There is also a 52-trim GT4294R (67mm inducer) that uses a slightly different compressor wheel, but should flow nearly the same.

Now, turn it up so we can see what it's really made of! Good work.

Daniel
 

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Suprawood, this would be the one he got?
1100 GT42R 94mm, 102mm 53, 56 0.60 Ball Bearing 82mm 84 1.15

His a/r is different... also the inducer looks to be 94mm not 70.34 like be said?
 

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A 56 trim 94mm wheel has a 70.34mm inducer. You would NEVER want a 94mm inducer wheel on a GT42....not even a GT47. You would be looking at a GT55 before you saw anything that large.

trim = 100 x (small diameter/large diameter)^2

If you look at the limitengineering link I posted it shows a 1.01, 1.15, and 1.28 A/R turbine housing options. I am sure Precision has the same options....maybe even others since they do a lot of thier own casting.

Daniel
 

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Discussion Starter #13 (Edited)
John, I'll have to look at the data again (don't have it with me) to give you an accurate answer, but the T88 made peak torque about 5200-5300rpm and the GT is noticably quicker.

chidoks, I actually bought this used from a friend ("uask4it" on here) with 2K miles on it. I think he got it from ATP turbo. Also as Daniel metioned this is the 56 trim.

trim = 56 = 100 * (Dp/Dg)^2 , where my Dg is 94mm. So my inducer is

Dp = ((56 * 94^2)/100)^(1/2) =~ 70.34mm inducer...or something like that. :)

Daniel, thanks man! Yep yep that's right on...and I agree this is a nice turbo, lovin it so far. I will get back with some better firewater soon and turn the boost up. My friend who had this one was gaining 20+rwhp when above 25psi. He sold this one to me, went to another T and now has changed back. His set up is similar, but with an AEM and SP intake manifold.

Oliver, thanks, yeah she does move a lot of air. Very efficient and we haven't really hit the happy spots yet.

Edit- sorry was typing when Daniel posted.

West, thanks man! I will get the sheet tomorrow. We were in a hurry to go eat and I forgot to grab it.

Brian
 

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k...makes sense now...thanks for explaining it...


SupraWood said:
A 56 trim 94mm wheel has a 70.34mm inducer. You would NEVER want a 94mm inducer wheel on a GT42....not even a GT47. You would be looking at a GT55 before you saw anything that large.

trim = 100 x (small diameter/large diameter)^2

If you look at the limitengineering link I posted it shows a 1.01, 1.15, and 1.28 A/R turbine housing options. I am sure Precision has the same options....maybe even others since they do a lot of thier own casting.

Daniel
 

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Its 4" IIRC, i had some good times with that turbo myself freezing my nuts off helping him put it on, LOL
Great numbers man!!
blkdawg said:
Brian,
Is the compressor inlet 4" or 5"?

thanks,
john
 

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It might be 5", i cant remember for the life of me. Brian will remember for sure though, as he bought all the piping
 
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