Ej20G + GT30
 

As above guys,

I am looking to try a slightly larger turbo on my V2.

The engine was rebuilt about 1000miles ago. Mahle 4032 pistons, eagle rods, ACL, ARP studs, MLS gasket,V4 STI heads. Fuel, ECU and drivetrain are already taken care of.
I am currently running a 20G, I would like to try something a little bigger and rotated.

Has anyone ran big HP reliably on the early phase 1 engines with the middle thrust bearing? Kinda looking for street power, but can deal with a bit of lag!

Or does anyone see any other weak point on my setup which could be prone to breaking if I go for more power?


Thanks
Dan

You completely omitted one important point - what heads do you have ?

Ah Yes. Sorry! STI V4

Unported v4 heads with stock camshaft and valvetrain will not flow too well on top and will run out of puff at 7,000rpm with a bigger turbo.

Depending on the compressor wheel size of gt30 turbo that you want, on a 2ltr with your heads you are likely to have 1 bar of the smallest gt30 (gt3071) turbo at 42000-4800rpm, for the next size compressor wheel (say gt3076r) you will add 500rpm to spool time.
Do you want to have a 2,000rpm powerband ?

And while your engine is certainly stronger than stock with its closed deck block and forged pistons, the choice of 4032 alloy pistons wont allow you to run high boost to compensate for lack of headflow, they are more of a moderate boost type of piston and they will still crack relatively easy if detonation is introduced.

4032 alloy does however last much longer than 2618 when used safely at power levels slightly higher than stock.

I suggest you stick with what you have, or go with a more modern turbo choice than 20g, for example a 2867r is a great turbo for 2.0 engines, because its a ball bearing turbo as oppossed to the journal bearing that you have now and has a billet compressor wheel, it will spool sooner than 20g and it will flow about 40-44lbs/min with relative ease which is more than 20g and can net you 370 at the wheels or 440 crank, which is a sweet spot for your engine. And another advantage point is that you dont have to go rotated, gtx2867 will fit in your stock location with a GT28 subaru ATP housing

Thanks for the reply. Will persist with the 20G for now then!

Ive ran a rotated gt3076r billet on a 2 litre and spool was pretty good, wasnt really laggy at all, i had full boost by 4200rpm and it hits like thor's hammer.

Mine was on a newage sti with avcs but a 2litre non the less

Besides AVCS, newage japspec heads have better cam profiles and flow rates than a ver4 head in its stock variant and your turbo was billet, this all adds up to a much quicker spool, however 4,200rpm is still mighty impressive for a 76 wheel.

What was your boost set at ?

Max boost was 1.8 bar, turbo had a .63 turbine housing.
Mine maxed out at 452bhp because it has a restriction somewhere that i cant seem to find as my setup should do around 550bhp.
Yes i agree the jdm heads maybe helping quite a bit

You still have same restriction there?

You didn't sort this ?

As per PM what I've said,we are have restriction on Up pipe side,which has caused few issues

Thanks,Jura

So the small gt30(37 or 71) lag doesn't seem too much different than my 20G.
I have tomei unequal headers and up pipe so hopefully not too much restriction.

Please have look on standard location turbos which are based on GT3071 like is MDX321T or V,SC42 or SC46 and then you can decide if its worth go with GT30

But I would go deffo with twisted GT30 than standard location GT30,its worth extra expense

Thanks,Jura

I think spool time is greatly effected by up pipe size.
I currently have a tomei setup which is near 60mm!!! Just found out it's bigger than my turbo exhaust inlet!! Far less than ideal.
What size up pipe are people running on their 20g's and gt30s.
When I twist the turbo I am thinking of scaling down to 45-50mm.

Thanks

Hi Dan

Yes off course Up pipe diameter will determine spool,oversized Up pipe(those Up pipe with flex joint) will have worse spool on any turbo,we've run once this Up pipe with TD04 and we are lost around 600RPM worth of spool if I'm comparing to the STI Up pipe

As many people running similar sized up pipes 60mm(2") on their cars with those turbos,not sure what diameter have GT Spec(not sure,but think is 2"),but we run GT Spec Up pipe on MDX321T,we are never tested or run Harvey trick Up pipe and due this I can't comment on that,but what I've seen few test on other cars its worth to have

And about the Twisting the turbo and using smaller Up pipe,1.7"(45mm) should be OK,as 1.7" diameter Up pipe should support or will be OK for 550bhp or more,not sure if then diameter at high 600hp this can cause any other issues

Thanks,Jura

Thanks for the interesting info Jura.
Going to modify my 60mm Up pipe to reduce down to 45mm and extend this pipe up to the turbo flange. Hopefully should help! I am amazed that companies are producing up pipes which are bigger than most turbo exhaust inlet holes! This but destroy spool up and introduce all kinds of turbulence and back pressure!

Hi Dan

Are you thinking to run standard location turbo and rotating this turbo ?

If yes then you will not gain a lot on the spool,you can gain with smaller sized up pipe,but how small is hard to say,you can ask guys who using Harvey Up pipe and what size is this Up pipe

Those Up pipes like on GT Spec or RCM(I think RCM using Venturi in their Up pipes) are OK and been OK on numerous turbo,problem is when you are want to run bigger turbo on 2.0 or 2.1L where lag can be the issue and where Up pipe with smaller bore/diameter can help without going with expensive route of the new heads etc

Will depends on turbo which you are thinking to run and from this I would decide,but GT30 .63AR will get my vote as best turbo for 2.0L or 2.1L,we run this turbo on 2.35L and car has been ballistic

Thanks,Jura

Jura,

Thanks again, Its nice to hear this stuff. Seems a lot of discussion of what up pipe is the best, but not so much on sizes.
Im tempted by a Gt3037 which is the small one! From my research with a decent setup ,the lag should be similar to my rather poorly setup 20G I am running now!

Hi Dan

There has been always discussion about the reducing lag on any turbo and Up pipe size really can improve spool or will worsen the spool

This GT3037 is GT3076R(30R) which we are run,but smallest will be GT3071R which should spool good on yours and 20G,not sure seen few of them and they're making nice power,is yours Billet or non billet ?

If its non Billet then I would upgrade to Billet and this will help for sure

On yours spec I would be more concerned by rods which you are running,Eagle rods don't have best reputation on Subaru engines,agree on Honda K20 engines they're used in great success on high powered cars,but when you look on those HP levels,then you will see Torque(TQ) is lot lower than you want to have,I know some people using better rod bolts and this can help

Thanks,Jura

I am running a Billet 20G with 7cm housing. I am only making 1.5 bar at 4300rpm. Which seems a bit slow for a small turbo! Have confirmed no exhaust leaks.
Think the up pipe must be killing spool! Ordered some reducers, So will try bringing the size down to 45mm. And see what happens!!
Gt30 is in the cart! Will be twisted to try and avoid the 90 degree intake bend on the V1-2 inlet!

Seems very laggy.
I'm running forged 2.1 with standard V6 heads and a rotated GT30 with 0.63 housing and making 1.9 bar by 4200 in fifth.
I have been advised this could be improved by getting a smaller diameter up pipe.

Yet to decide on what size to make the up pipe

Billet or non billet?

Wow,that's bit late for Billet 20G and 7cm housing,I know on bigger exhaust housing you can loose on the spool up,but gain on top end

With larger Up pipe you will have slower spool and yes 45mm should be OK for yours needs,but Up pipe size should dictate how much power you are want to run

Thanks,Jura



That's nice on 2.1L and V6 heads,are you still planning to run AVCS ?

Thanks,Jura

I ended up reducing the outlet from header collector to around 50mm and building the uppipe from 50mm.
Now running a GTX3071 with spool not too much different from my old 20G.

Attachment 45182

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I personally think that is still too big. I run a 32mm up pipe on my s206 billet turbo, spoll is out of this world and still builds power at redline.... Doing 550/60+hp ont his set up...

Really?? That's like smaller than std right?

I couldnt say, never had a standard one!

The idea is to keep as much gas moving as hot and as fast as possible, so a smaller surface area and smooth unrestricted flow with shallow bends and as few-er joints as possible is key.

A larger diameter pipe hs a larger surface area so more heat is lost in to heating the pipe, this means less energy getting to the turbo. Heatwrap will help with the heat issue, but its no substitute. I would have aimed for about a 1.5" up pipe in this scenario...

For reference, a standard sti up pipe is 42mm inside diameter. The Harvey up pipe diameter depends on what turbo it is being mated to. There are a few variants.

Ah right ok. Well i have a custom uppipe and it's 2.5" on a rotated system and i don't hit full boost till around 5k :lol:

Will be getting a smaller uppipe made

What turbo is that on?!?

On my S206 im getting full boost below 4k....

It's some old precision turbo like ancient **** tbh. Will be getting a billet gt30 now with smaller uppipe. You got a graph of yours?

Turbo S206 Std placement based on a T38.

Attachment 45174

Graph no meth -

Attachment 45175