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Old 01-06-2011, 01:40 PM   #97
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Join Date: Nov 2004
Location: PERRIN Performance

Originally Posted by Phatron View Post
nice right gtx30 vs gt35

i think thats one of the biggest questions......since the gtx30 comp map looks so simliar to a gt35...then question becomes why would i get the gtx30 if the gt35 has more power potential and only xxx rpm later spool.....
Good question, why get a GTX3076R if the GT3582R is cheaper and make more power. I can say that for a fact, the GT35R with a .63 housing is no where near as snappy on the road. Without doing the back to back runs (which will be very soon), either 3076R turbo is better below 4000RPM. On the dyno a GT3582R with .63 spools like a GT3076R with a .82, but the question is, does it make more power. I have tons of dyno graphs of customers cars with the GT3582R with .63 and at 22psi of boost they are making 430-450WHP and TQ. But we will do our own testing to really see how they compare on the same car, same dyno. I suspect that its because of the free flowing natures of the bigger exhaust wheel that it will make more top end power.

I am dynoing a friends GT35R with a .63 in a few days (has cams though) so we will get some good results there. Then if i have time swap to the GTX for a few runs we will get that. My intention is to do the GTX3582R on my car to keep things as consistent as possible.

Originally Posted by juanmedina View Post
Ron's question will be answer we you guys overlay gtx30 with the gt35 at the same boost level and tuning.

are u guys planning on testing gtx35 vs the gt35? How much power do you loose by switching to the .63 AR housing?

Thanks for the test
For sure! I have the turbo here as well. Most likely not the .82 GT3582R but for sure .63 is planned right away.

Originally Posted by NSFW View Post
This is why I'm really looking forward to a GTX3071 vs GT3076 comparison.

For the 3071, the GTX does use a larger turbine than the GT. From the dimensions, it appears that the GTX3071 might use the same turbine as the GT3076. So I think it's reasonable to expect the GTX3071 to produce similar power to the GT3076. The big question is, how much faster will it spool up?

But don't get me wrong - the GT/GTX 3076 comparison is still pretty interesting in its own right. Thanks for posting it!
I have the GTX3071 here, but i highly dout that its faster spooling. Or faster spooling enough that its noticeable. Because it DOES use the same turbine as the GT3076R and GTX3076R (60mm) i don't think its going to do anything but act like a GT3076R. I was hoping that it would use the smaller 56.5mm wheel which does make the turbo spool quicker by about 300-400RPM. (Tested on 08WRX where 3071w.82 hit full boost at 3600). But since it shares the same turbine wheel the only reason it will spool faster is for reasons the compressor wheel weighs less.

If you think about it, at the same given RPM/Load point the turbo speed will be the same between the two turbos (GTX3076 and GTX3071), but the 3071 will be slightly more efficient at the lower RPM points. So it may allow for a few more HP, but most likely not much different response. That is my guess, but i could be wrong.

Lets just say for argument sake that it does act like a GT3076R, then its not worth buying as it cost about $250 more. But who knows.

Originally Posted by LittleBlueGT View Post
If the GTX turbo needed more WGDC to hit target, that means it was dumping less exhaust pressure to control boost. Higher WGDC means the WG is opening less, and more air is going past the turbine.

Thanks for the rest of the work you did, very informative, done fairly as well.

I also would love to see the GTX3071 turbo done.
Sorry, it was late, i was on a roll with getting it done and just was thinking straight. Thanks for saying something, this morning my mind is much clearer. I changed it up a bit to make more sense.

Originally Posted by kellygnsd View Post

What effect on spool do you think holding the cars at 2000 for 3 sec at full throttle had on spool of these units. Do you have any runs in which you didn't "brake" boost before the start of the run?
On the bigger turbos, 2-3 seconds is the same as 4. Because the transient response is slower and boost doesn't hit until 4000 its not a big deal. BUt on a 08 WRX if we used a 3-4 second launch, it will be at 10psi before the run begins! So on those 2 seconds is perfect. On the GT turbos, you floor it at 2000 and boost starts at say 2psi and might climb to 3psi before the run starts. On an STI or WRX with stock turbo, you floor it at 2000 and it might start at 2-3psi, but by the time the run starts they can be at 8psi. What makes the most difference is hot header vs. cold header.

Originally Posted by stu View Post
did you try any race gas while it was on there.
Nope no race gas. I wasn't going for the gusto to make the most power possible. It was more to show everyone the GTX and how it compares to the GT turbo. I am excited to see what other tuners and our customers get out of these with race fuel, built heads, and other crazy things!
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