R34/vg30 Turbine Exhaust Cover - On Gcg High Flow

[benl1981]

Ok. I got some advice on here and had the GCG highflow done with the larger op6 housing.

The response is now pretty average. Considering switching back to an R33 housing.

Car is R33 rb25det

Mods:

3" and 3.5" turbo back exhaust

PFC

Z32afm

480cc injectors

tomei fuel pump

FMIC

Boost builds much slower. I am going to modify the actuator a little but it seemed fine when I put it on. GCG had the actuator and set it up.

I had another mongrel highflow on before this (slightly smaller wheels and R33 cover and it built boost quite a bit faster)

Anway 14psi by about 3700rpm in 4th

and 4200rpm in 2nd gear

Haven't had a tune so it is running very rich.

How much does the tune actually help the boost build (ign timing and correct AFRs)? A few of the tuners say it is mostly the physical size of the turbo.

Bit of a pain since I didn't want to pull the turbo off again

Its very noticeable coming round a corner in 2nd gear with about 2500-3000rpm - with the stock turbo you squeeze the throttle a bit and the rear wheels would scrabble for traction. Now you can keep your foot planted till you get the boost coming on hard at which point you are back on the straight.

Cheers

Edited December 26, 2007 by benl1981

[Abo Bob]

A tune can definitely help. So can proper use of cam gears by your tuner. I have cams and get 1 bar by 3100.

[NYTSKY]

I have cams in mine aswell,and i dont see full boost (16psi) till 3800rpm.I think its normal with these sort of highflows as really the GT30 based wheels are cropped slightly to fit into the housings.Thats the price you pay for the bigger power gains you get from the bigger 0P6 housing. For example the GT3076 ill be putting on my car next month will have the same response as the highflow i have now.The GT3076 is much bigger than my highflow,its just the GT3076 is more efficient than a highflow.As a result ill get alot more power.

[discopotato03]

Your engine should now be able to take a fair bit more ignition advance and that tends to improve bottom end torque and often the turbos boost threshold .

I'm told that a properly designed split dump pipe also helps with those Hitachi integral gate exhaust housings .

I think a tune session is whats needed and if you still don't like it then use the RB25 housing .

Cheers A .

[R31Nismoid]

Without a proper decent tune, having anything upgraded is a waste

[benl1981]

NYTSKY - is that 3800rpm/16psi in 2nd gear or in 4th?

How does it feel going round corners in 2nd? I find a lot corners that keep the revs below 3000rpm see the engine drop right off boost.

[NYTSKY]

NYTSKY - is that 3800rpm/16psi in 2nd gear or in 4th?

How does it feel going round corners in 2nd? I find a lot corners that keep the revs below 3000rpm see the engine drop right off boost.

3800 in first and say 3700 in all other gears.And yes if i go round a corner below 3000 there will be a second where im waiting for the boost to come back on.But mate that is normal.

But really i dont see the need to bring full boost on in second as all i get is wheelspin when full boost comes on.And as we all know now in NSW wheelspin can carry a gaol term.

EDIT:No turbo upgrade will ever have the same response as the stock one.IMO

A highflow is the most basic turbo upgrade,and even that gives away in response.The fact you went for the 0P6 housing as i did was to have a bit more power in the top end.Thus result in lower engine response.

[Simon-S14]

Ive got a 3071R with the GCG op6 casting rear housing... and its not laggy at all! spools at 2000 rpm and full boost just after 3000.. cant complain. and thats with a larger compressor housing compared to a highflow.

its all in the tune!

[benl1981]

I'm surprised the tune can make that much difference... I am thinking of swapping back to a R33 housing.

Been doing a bit more reading and it sounds like the larger housing costs about 300rpm of boost response but gives about 15rwkw more..

NYTSKY - I would think if you had 16psi by 3800 in 1st it would be much lower in the higher gears..

[Sydneykid]

I will swap you turbine covers, been looking for a VG30/R34GTT one for a couple of weeks.

I mean, advancing the ignition timing about 15 degrees won't help much

Leaning it out around 2 points, probably won't help either

As for retarding the exhaust camshaft timing 4 degrees or so, well we all know that doesn't do anything

Yep, I definitely think you should swap with me right now

Cheers

Gary

[Sydneykid]

EDIT:No turbo upgrade will ever have the same response as the stock one.IMO

Ah, no. My R34GTT had more power EVERYWHERE, from idle to redline than when it was standard. SoSK's R33GTST is about to do the same and, if someone swaps the VG30/R34GTT turtbine cover with me, I believe I can accomplish the same with it.

Cheers

Gary

[benl1981]

Hahah. SK. I thought you weren't a fan of the vg30 cover? You lost about 250rpm of boost response from some of your old posts...

I'm still not sure whether to rip it off. Not the most fun job pulling turbos off.

But if you're at about 3000rpm even in 4th and floor it it builds boost quite slowly. I was thinking the r33 cover would make it quite abit more responsive.

If the difference isn't huge maybe I won't bother.

[Simon-S14]

the difference is in the tune

[mjfawke]

Just one thought - rich mixture means cooler exhaust temp therefore less pressure across the turbine. Running it leaner (as in not excessively rich) should bring it on boost earlier.

[Sydneykid]

Hahah. SK. I thought you weren't a fan of the vg30 cover? You lost about 250rpm of boost response from some of your old posts...

I'm still not sure whether to rip it off. Not the most fun job pulling turbos off.

But if you're at about 3000rpm even in 4th and floor it it builds boost quite slowly. I was thinking the r33 cover would make it quite abit more responsive.

If the difference isn't huge maybe I won't bother.

Yep, around 250 rpm is it. But the rebuilt RB25 in the R33 is actually an RB25.5. So I get the 250 rpm back with the larger capacity, not to mention the Poncams, porting and larger exhaust valves. I would like to see how close I can get to 300 rwkw out of a GCG Highflow

Cheers

Gary

[MANWHORE]

sk, i've got one have had for a while, but i just haven't been posting.

[benl1981]

So SK. Assuming you had a regular 2.5L normal cams etc would you recommend the vg30 housing in order to get ~ 250rwkw.

Should the response still be ok? Putting your invested interest aside hahaha

What I'm wondering is if is worth downgrading to the R33 cover to increase response and still have close to 250rwkw. It's about 4-6 hours work taking the turbo off and on again though.

[Sydneykid]

sk, i've got one have had for a while, but i just haven't been posting.

Yes I know, but it is a bit too much for what's left of SoSK's budget.

We got a bit carried away with the RB25.5 rebuild and so it's got some serious stuff in it and done to it.

Cheers

Gary

[benl1981]

What you reckon SK? Did you see my post above?

Cheers

[Simon-S14]

dont know how many times it needs to be said, tune it first, then make a decision after that