Turbo Choices for ScoobieWRX

[ScoobieWRX]

What i have sussed out from all this, and having done some more logging today, is that i'm not sure now if the decat 3 bolt uppipe that's part of the GT Spec GenII headers is a bit much for the VF35, and i'm now thinking a smaller diameter pipe would be better suited to the VF35 producing better spool up lower down.

You are entirely correct, the standard 3 bolt up pipe is way to big for any stock turbine housing. We have a test up pipe here which is set to replace it in our 3 bolt manifold kits. .


Jase.

I take it your test uppipe is a 2.5" ID 3-bolt pipe. I haven't seen any at 2.5" 3-bolt, they all seem to be 3". I may be interested in that if you get some good results and it shows quicker and much lower RPM spoolup.

With my setup that is the STi8 with STi TMIC, VF35, STi pinks, flat panel air filter, snorkus mod, catted 3" downpipe, walbro pump and adjustable fuel pressure reg + the headers and uppipe, what do you reckon is the best i could reliably hope for?

At the moment I get 1.48bar peak boost down to 1.12bar at the redline. I run mid 11 AFR's on Tesco 99RON, no additives, no IC spray.

Your pro advice would be gratefully accepted.

[Gerry H]

Up-pipe's aren't those sizes.

[ScoobieWRX]

Gerry, My uppipe starts off as 58mm ID and for 90% of the way up to the Turbo, where the last 10% of the uppipe tapers down to whatever the size of the turbo exhaust inlet is, 52mm (2") maybe, don't know for sure so perhaps if you know what it is you can tell me But you're right it isn't 3", it's 2.3" so Jase's 3-bolt uppipe may be 2"

Apparently it's supposed to create a venturi effect so exhaust gases are flowing quicker at the turbo end than the header end but i don't think that is the case in practice and i think it's just bullshit for 'and it fits the turbo end too', maybe i'm wrong.

However, it's true to say that a narrower ID uppipe that's uniform all the way up will flow faster than the bigger ID pipe even with its taper. A narrower ID pipe with a 3-Bolt header flange would be the way to go and Jase seems to have such a thing on test. It would more than likely cure some of the lag i'm getting now which i am trying to over compensate with by having higher AVCS values set which to be honest i don't think are making a huge amount of difference and there might not be a lot of difference to the mid/high range of my current uppipe. However, i have noticed mid-range and top end power to certainly feel very good and come in quick so do i want earlier spool up or better on the move mid/high range. It's a trade off really, what more important.

If you want to see one of these 3-bolt flanged uppipes go to RCM and ask to see their GT Spec GenII headers. They have some on display up on the wall of their shop. It's exactly the same ID as mine, and don't forget to take a ruler with you just to make sure

[Gerry H]

Same headers I have nd to be honest, didn't take much ntice of the pipe diameter. I was so pee'd at having failed header to up-pipe gaskets, the three bolt flange was the decider.

A smaller pipe will increase the gas velocity over a larger diameter because it's a smaller pipe. Same amount of gas passing through a smaller space has to get to the end quicker

[ScoobieWRX]

I've heard a bit on other forums about 2-bolt flange gaskets failing so it must be a common problem.

We'll see what Jase's findings come up with on his narrower uppipe.
You never know!!

[duncan]

What i have sussed out from all this, and having done some more logging today, is that i'm not sure now if the decat 3 bolt uppipe that's part of the GT Spec GenII headers is a bit much for the VF35, and i'm now thinking a smaller diameter pipe would be better suited to the VF35 producing better spool up lower down.

I'm almost at full boost by 3300/3400rpm and i am sure the VF35 is meant to kick in a bit sooner than that. Any suggestions Duncan??

In hindsight i maybe should have gone for a more standard set of tubular headers with the smaller diameter 2 bolt uppipe.

I think i need a bigger Turbo :lol:

What AFR/wgdc/timing are you running early on in the map Francis to bring the spool in sooner?

[ScoobieWRX]

Initial WGD WOT:

Throttle - 100%
2400 - 100.0
2800 - 80.0
3200 - 60.0
3600 - 42.0
4800 - 45.0
5600 - 51.0
6400 - 68.0
6800 - 68.0

AFR Between 1200 and 3200 rpm
14.70 - @ 1.00 Load
13.84 - 12.99 @ 1.20
13.25 - 12.71 @ 1.40
12.89 - 12.63 @ 1.60
12.71 - 12.46 @ 1.75
12.71 - 12.38 @ 1.90
12.71 - 12.38 @ 2.05
12.71 - 12.30 @ 2.20
12.71 - 12.22 @ 2.35
12.71 - 12.06 @ 2.50
12.71 - 11.98 @ 2.65
12.71 - 11.86 @ 2.80

It's easier if i just put some screenshots up

[ScoobieWRX]

[duncan]

edit

[Gerry H]

Don't forget Francis has a 2.0L not 2.5L