Why a compression issue?

low compression is possible (albeit not likely), but there are so many factors here. Besides the turbo itself, the exhaust manifold design, boost controller setup, intercooler setup, porting, and so many other things will affect spool.

Due to the time and trouble involved I really think you should switch to a turbo with a smaller T3 hotside first, and only if you aren't satisfied should you go down this route. That will give you the transient response you want. Then you can set up the boost controller to give you midrange punch by running higher boost in the low to mid range and letting it fall off in the mid to upper rpms where the engine is more prone to knock. This type of setup is very common on 4 cylinders (Evo, STi) making broad midrange torque.

moehler as you can already tell from this thread a boost threshold of 16 psi by 4300 RPMs is way out of the norm.

Here we are talking about BB, piping, port jobs, manifold designs, switching turbos, low compression engines... When in fact the largest contributor of spool time is the turbo itself (lol). Funny I just realized that we seem to be under the impression that you have a healthy turbo. As you stated yourself: you bought this FD with the conversion already done, meaning you don't know the history of your turbo. Shoot for all you know you could have a T-78 (No just joking ;) but I'm trying to make a point).

I'd say take out the turbo and have it inspected.

Let me get the car out and again verify the spool. It may be closer to 4k (it's definitely over 4k). There really is no evidence that the turbo has a problem, it really just has a large hotside, it's non ball bearing and is built more for top end than mid-range power. 4-4.3k makes sense for that kind of turbo (it put down 504 rwhp at 17.5 psi).

well shoot, there's your answer right there. No need to verify anything. Whenever you get around to changing out to a different turbo (if you do of course) come back and update this thread. As I'd love to hear your experience of a top end car vs a midrange one.

Low compression = slow spool, but 500rwhp @ 17psi indicates a healthy motor. Although there are a ton of dynos that rear stupid high. I would do a compression test to rule it out, takes all of 10 minutes...

You are using the same turbo I mentioned, but this one has a 1.15 and hits 15psi by 3k rpms...

Yeah on another dyno (but with old, bad plugs) it did 478 rwhp at 17.5 psi. I had a compression test last year and it was perfect. Hopefully it still is, but there is nothing that indicates otherwise.

I think I'll just switch to a smaller single turbo when I am ready to make a move. It actually is a lot of work to get back to the twins (and money since I want BNRs). Thanks for thehelp guys :icon_tup:

someone correct me if I'm wrong, but a gt35, especially at 17.5 psi, shouldn't be capable of making 500 whp. methinks you haz a bigger turbo.

It's a 3574...

Bump for update!

http://www.a-spectuning.com/html/products/gt3574.htm

Also, after reviewing my original post I forgot to add that I have a T3 35R.