G25-550 Exhaust Housing Question - And your general experience

[Ryan_H]

Hi All

I'm building a street S14 with an SR20DET VVT (not VVL!) for the weekend here in the UK that will do occasional track work.

I want something very driveable and responsive and with a bit of punch. I've come to the conclusion the G25-550 works best for me.

Now here's where I could use advice.

I want to keep the setup simple, so ideally I want to use the T25 exhaust housing that is available for it so I can mate to a PSM Flex Cobra downpipe and maintain the low mount position. I also want to keep it internally gated.

There is a T25 5 bolt housing compatible with the Flex Cobra with an AR of 0.64. The next one along is a VBand at 0.72.

My question is, what's your gut feel of the 0.64 AR in terms of power output?

I presume it'll break 350hp at the flywheel which would be fine for my needs but what could it realistically do, your input is appreciated.

And secondly, is anyone here running a G25-550 on an SR20DET (in any config) and would you mind sharing your feedback? I have tried to search for it on here but come up short.

Thanks

Ryan

Edit - to add, the motor is built and has Tomei USA 258 IN/EX Cams. I have, I believe, Nismo 555cc injectors but I can swap these out for whatever.

[PoorMans180SX]

On what fuel?
The .49 housing will indeed break 350whp on E85. I've never seen a .64. It should make over 400whp actually. Anyone telling you you NEED the bigger housing is a liar. The new turbine wheels flow so well, you do not need a big exhaust housing like the old shitty Garretts.

Here's one doing just that. G25-550 .49 T25 housing, BC 264 cams and valvesprings.

[Ryan_H]

Thanks for this, this is super useful and tbh quite exciting, especially as that's the smaller housing again. It says Pump in the dyno run at the bottom, was that a pump gas run? And are you sure that's the 0.49? If it is, amazing.

I won't be using E85, I'll be using UK 98 RON fuel. I am trying to find what that means in the USA on google, looks like the comparison would be 90 MON or 94 PON, does that make sense?

I haven't been told I need to go bigger, I appreciate how well the compressor flow on these G series turbos.

I had a twin scroll EFR7670 on my last SR20DET and it was just awfully mismatched to me, so I'm looking for a much punchier car.

[PoorMans180SX]

Originally Posted by Ryan_H

Thanks for this, this is super useful and tbh quite exciting, especially as that's the smaller housing again. It says Pump in the dyno run at the bottom, was that a pump gas run? And are you sure that's the 0.49? If it is, amazing.

I won't be using E85, I'll be using UK 98 RON fuel. I am trying to find what that means in the USA on google, looks like the comparison would be 90 MON or 94 PON, does that make sense?

I haven't been told I need to go bigger, I appreciate how well the compressor flow on these G series turbos.

I had a twin scroll EFR7670 on my last SR20DET and it was just awfully mismatched to me, so I'm looking for a much punchier car.

Indeed the bottom run is on pump gas, but he tuned it extremely conservative, as the car (not mine) will be running E85 almost exclusively and 91 octane would only be for emergencies or flushing the fuel system. I am positive it's the .49 housing, that's the only reason I saved all that info. It's even on the factory SR exhaust manifold! People still have that old Garrett mentality, and it just doesn't apply to modern turbos with properly matched turbine to compressor sizes and good turbine wheel design.

Yeah your 98ron is basically like 92 octane here.

[Ryan_H]

Thank you bud, apologies I didn't come back to the topic, I actually thought I raised it on another forum.

Well, you've got me thinking that the G25-550 0.64 T25 might very well be the way forward. It would be awesome to have a 400hp car, but anywhere around 350hp is absolutely spot on for me. I am seeking response, so I will let you know what I decide.