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Currently have a twin scroll .78 3071 setup on my SR with 290rwks at 22 psi....max power at 7700rpm

I was going to swap in a 3076 56 trim CHRA.......cos I can't stop tinkering and evolving my setup.

However, I note that the Evo X Garrett upgrade turbo specs in a twin scroll format are:

3071 56 trim comp / .73 ex a/r

3076 56 trim comp / .94 ex a/r

This then suggests to me that my current .78 ex a/r might be too small for a 3076 56 trim comp as Garrett has used a .94 ex a/r on a 2 litre Evo motor.

The 52 trim comp 3076 falls roughly between the 3071 and 3076 56 trim. A rudimentary and purely unscientific calc shows that the middle ground of the .73 and .94 ex a/r is approx .83 a/r.

OK so .83 is still bigger than my .78 but I was thinking of having the .78 e/x a/r extrude honed and I have a few other tricks to try which would give it a bit more flow.

There is a .82 twin scroll ex a/r available via GCG however its a different housing altogther meaning it places the turbo in a different position to the .78. The .82 also needs profiling and as it only has a slip joint outlet, a v-band or 4 bolt outlet needs to be welded onto it. Plus I haven't seen any solid results from the .82 twin scroll housing - so its an unknown.

So my conclusion was to stay with a .78 ex housing with extrude hone and fit the 3076 (3037) 52 trim turbo instead of the 56 trim.

I'm after the optimum 3076 turbo comp/ex match for all round efficiency spool/response

Do people concur with my thoughts or am I just over analysing things and should I just go with a 3076 56 trim?

I will try E85 in the future - I have a 205 litre drum at home to try and will run it full time if the stuff every becomes available at the pump<<<<< just mentioning this in case that would sway your decision re a 52 or 56 trim.

Cheers

Edited by juggernaut1
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Its difficult to make a direct comparison of those two turbine housings because they are not of the same family , the 0.78 A/R one is from a GT32 series diesel turbo and the 0.94 A/R one is model specific to the Evo 10 and the GT30 petrol turbo family .

Garrett used to advertise the GT32 as a GT3267 and GT3271 and the turbine was a smaller trim (from memory) than the 84T GT30 turbine .

The theory of TS turbine housings is to go larger in A/R than most would image particularly if going from single scroll turbo systems . The idea is that you want the manifold pressure to be high when the turbine needs it and low when the engine likes it . In a bigish single scroll housing the pressure is low when it needs to be high (low revs) and high when it needs to low (high load/revs) so really the wrong way around .

A TS housing thats too small in A/R gives a pulse damping effect which is not ideal unless you want lots of torque at quite low revs with a small/med capacity compressor - diesel style . Remember those GT32's with an ~ 65mm dia turbine and a 67 or 71mm diameter compressor .

The word on the "street" is that Garrett got around the twin IW valve issues in the Evo 10 spec TS GT3076R but I haven't looked into them since I got my single scroll GT3076R/3037 52T . I can't justify a TS system on my GTS25T and I've seen them go "well enough" to please me without it .

Different if you're racing and need every advantage available to you but for me there are limits to how much torque you can feed into a RWD road car and street rubber .

Cheers A .

I hear what you say re the background of the .78 a/r thats why I mentioned I make peak at 7700rpm as some sort of evidence (or luck) that it does flow at these rpm and makes 290rwkw in the process

with the 3071.

Did you have a conclusion to my "theorising" as to whether to go a 52 trim or 56 trim. :rofl:

Edited by juggernaut1

^^Yes, interesting thoughts Juggernaut...

i too have wondered the same, as i have an sr22vet in a datsun 1600 with a HKS 3037 pro s with the .78 atp twin scroll rear and thought that maybe i had gone for a housing that was a bit on the small side... a .92 maybe something i will have to investigate further if i dont see the numbers im hoping for .

But as you have made 290 rwkw @ 22 psi...im sure my goal of 350 rwkw can be had on E85.

If you were in sydney i would lend you my turbo to do a comparison back to back.

Strewth....a Datsun 1600 is going to be a handfull with a twin scrolled 350rwkw on E85 if your goal is reached.

.78 could be a too small for a 22vet motor. However, E85 seems to somewhat delay the effects of going too small a housing based on what I've seen.

In addition to the .82 I mentioned a 1.06 housing is also available from GCG in T3 format......I see ATP also lists a T4 twin scroll housing for the 3071/76 turbs.

Your only other option would be a switch to the BW twin scroll turb's....although dyno results are as rare as hens teeth.

Edited by juggernaut1

It look like the only t4 housing that atp supply is the 1.06,which was not available when i got my rear housing from them.

Though i think i will be happy with the response from .78...after all killer throttle response and a strong curve was more important to me than an overall number which is why i chose to go 2.2 litre with a twin scroll & individual throttle bodies.

I was going to try a borg warner as i have seen & heard good things from them,but i thought i would try the one i have first.

Unfotunately there is no universal .94 twin scroll ex housing.

The .94 I mentioned is purely a bolt on proposition for the Evo X which of course has a different footprint to the generic T2 / T3 / T4 fottprint Garretts.

ezy 9's: you'll be happy with the throttle response of the .78 especially on a 2.2. If you refer to the Full-Race website, they recommend that you grind back the CHRA bolts so they don't protrude into the volute of the housing.

Edited by juggernaut1

Yes mine came through GCG as did the port shrouded compresor housing to suit the 52T compressor .

CHRA or cartridge number is 700177-5006 . I opted for the 0.82 A/R Garrett GT30 IW turbine housing . It hasn't been fitted yet so can't give results .

Cheers A .

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