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Gt3076r Rear A/r Question

drpheel

By drpheel,
in Engines & Forced Induction

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drpheel Enthusiast

drpheel

Posted
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One of my buddys can souce me a BorgWarner turbo for my Rb25, the model is S259 and this unit is there interpretation of the 3076r. My Exhaust will be V-band but as for the rear A/R, they do not offer the standard .63 or .82 A/R that you see in most Garrett housings. I have no compressor maping for the s259 as it is fairly new on the market so nothing to base my numbers on :blink:

Turbo Specs :

360 journal, oil cooled , billet wheel with ETT wheel ( extended tip technology )

- Compressor Wheel Ind:59mm, Exd:80, Trim:44

- Turbine Wheel Ind:61.5, Exd:69.5 ***OR*** Ind:64, Exd:74

Here are my options for the rear A/R :

- .55 a/r

- .70 a/r

- .76 a/r

- .85 a/r

The recomended A/R for the GT3076r is .82 as most people using this setup are showing good numbers ( with supporting mods) The .55 I know for sure is no good as even the Garrett .63 are not recommended for the RB25.

My question is : What would you guys use OR try on a rb25 and what would be the outcome or expectations of your decision.

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https://www.sau.com.au/forums/topic/328979-gt3076r-rear-ar-question/
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WYTSKY Veteran

WYTSKY

Posted
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the thing is, the Garrett core in the 3076r is water and oil cooled and comes in ball bearing which is better for response.

I dont know where you have heard .63 rears are too small... me,the mafia and simonr32 have all made good power with it, but with great response. lookup the rb25 dyno thread, simonr32 is making like 350rwkw....

we need to know how much power you are looking for and how much lag you are willing to sacrifice for that, that will help determine which rear housing.

personally.. because it is only journal bearing so response will be slower, I would go the .70, seems like a good mix between power and response in my mind...

drpheel Enthusiast

drpheel

Posted
  • Author
Posted
the thing is, the Garrett core in the 3076r is water and oil cooled and comes in ball bearing which is better for response.

I dont know where you have heard .63 rears are too small... me,the mafia and simonr32 have all made good power with it, but with great response. lookup the rb25 dyno thread, simonr32 is making like 350rwkw....

we need to know how much power you are looking for and how much lag you are willing to sacrifice for that, that will help determine which rear housing.

personally.. because it is only journal bearing so response will be slower, I would go the .70, seems like a good mix between power and response in my mind...

I have looked at alot of the RB25 builds and like I said above, non of theme are with the A/R selections That I have, Numbers will be 350 to 400 WHP , I want a smooth power band ... I dont want to have it go sideways when the boost kicks in, but I dont want to kill the top end either

For street responce im thinking .70 or .76

drpheel Enthusiast

drpheel

Posted
  • Author
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Ball bearing v Journel Bearing core means sweet FA when comparing different turbos.

and the Borg Warners are a good thing.

I would probably try the .76 as a good all round street turbo.

Agree, With the billet wheels and the new ETT my tuner has seen some spool a few 100x rpm quicker then the 3076r on some Vw Vr6

.70 or .76 seems like a good mid range street choices .... I dont like to pull up at a light to race I rather drop a 3rd on the Hwy I think this will lead to a larger A/R to take it a bit more in the top end

drpheel Enthusiast

drpheel

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Yeah, if your after highway overtaking type power then the 0.76 is the clear winner

You think the .85 would be to much of a slug in the streets ?! Yet people that run a 3076r with the .82 praise its good response and power :(

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
the thing is, the Garrett core in the 3076r is water and oil cooled and comes in ball bearing which is better for response.

I dont know where you have heard .63 rears are too small... me,the mafia and simonr32 have all made good power with it, but with great response. lookup the rb25 dyno thread, simonr32 is making like 350rwkw....

On a hub dyno & E85... You won't see that on PULP :(

And Jono is using water meth... So bit of a helping hand in both scenario's

I want a smooth power band ... I dont want to have it go sideways when the boost kicks in, but I dont want to kill the top end either

For street responce im thinking .70 or .76

The .82 will come on much nicer compared to a .63.

The .85 could be an option to consider - what it depends on is exactly "how close" the two turbos are in terms of characteristics.

I mean if the turbine wheel is a tad smaller/trim on the BW turbo compared to the Garrett then the .85 should respond in pretty much the same manner as a GT .82 if you catch my drift.

Other side of the coin if the BW is a tad bigger, then the .76 would then be the choice.

I think .70 would be to small either way - again though depends on the turbo and what BW have to say about it.

tridentt150v Grand Master

tridentt150v

Posted
Posted

I like my 0.82, but I think a mid sized exhaust housing would be better.

The HKS 3037 is 0.68 and I think it is still a midgion small.

Ideally I have a feeling that somewhere around the 0.75 would be ideal, but I do highway miles and my 0.82 is good for that. At 100km/h it is just spooling and then it gets motoring from then on. A 0.63 would be spooling all the time.

But this is for my use, others have different needs and uses.

drpheel Enthusiast

drpheel

Posted
  • Author
Posted
On a hub dyno & E85... You won't see that on PULP :(

And Jono is using water meth... So bit of a helping hand in both scenario's

The .82 will come on much nicer compared to a .63.

The .85 could be an option to consider - what it depends on is exactly "how close" the two turbos are in terms of characteristics.

I mean if the turbine wheel is a tad smaller/trim on the BW turbo compared to the Garrett then the .85 should respond in pretty much the same manner as a GT .82 if you catch my drift.

Other side of the coin if the BW is a tad bigger, then the .76 would then be the choice.

I think .70 would be to small either way - again though depends on the turbo and what BW have to say about it.

Thanks for all the help guys !! I think this seals the deal, the .76 will be my choice !

I just got a message form my tuner telling me the BW rear housings are about 300 UDS so if the .76 does not suit my style Il try to swap for either bigger or smaller knowing that I have a base idea of what the .76 feels like

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