Backpressure issues? comp 6265- A/R .68, 2jzgte

TBS

New Member
Feb 3, 2011
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Oslo
Hey guys.

I just had a conversation with the tuner that is going to be mapping my car in about a month. And he said that we'll might have an issue with backpressure on the exhaust because of the small A/R of the turbo on the 2jz... So i wonder if any of you have any experience with that kind of A/R size on the 2JZGTE...?

Thanks, Tim
 

nathaninwa

New Member
Jul 1, 2012
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Aberdeen, WA
How will the car be driven? Street or drag? What kind of tq/hp numbers are you looking for? If for the street and moderate goals of 600whp then perfect. Small housing for quick spool and good tq down low, for a bit of sacrafice up top. All motors are different based on intakes, exhaust, cams and porting. And more importantly driving style.

Do you have a standalone ecu? If so, its simple to find out if the housing is a restriction. Wire in a second map sensor and log it. I've talked to pte before, and they don't want to see anymore than a 2-1 drive ratio. So when collector is twice what boost pressure is, then the housing is to small. I would change it out before then, but I think you get the idea. Housings aren't cheap, so work with what you have and see.

If you can't log it, that's fine, either use a junk boost guage with lots of hose on it with copper at the header, or use a map sensor and use a volt meter to watch the voltage output and compare that to the reference scale. Either way, you should weld a 1/8th pipe bung in the header. I do this for all mine and the info is great.

For reference, I'm about to start up my 2j and have a 6466 with the divided .84 housing.

This same housing on a worked over 2.5l with a 6262 only produced 34lbs drive pressure at 27lbs of boost pressure. So unless you looking to run max boost like 40psi on race gas and drag the car at 800whp, id say run it and feel it out.
 

TBS

New Member
Feb 3, 2011
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Oslo
nathaninwa;1895638 said:
How will the car be driven? Street or drag? What kind of tq/hp numbers are you looking for? If for the street and moderate goals of 600whp then perfect. Small housing for quick spool and good tq down low, for a bit of sacrafice up top. All motors are different based on intakes, exhaust, cams and porting. And more importantly driving style.

Do you have a standalone ecu? If so, its simple to find out if the housing is a restriction. Wire in a second map sensor and log it. I've talked to pte before, and they don't want to see anymore than a 2-1 drive ratio. So when collector is twice what boost pressure is, then the housing is to small. I would change it out before then, but I think you get the idea. Housings aren't cheap, so work with what you have and see.

If you can't log it, that's fine, either use a junk boost guage with lots of hose on it with copper at the header, or use a map sensor and use a volt meter to watch the voltage output and compare that to the reference scale. Either way, you should weld a 1/8th pipe bung in the header. I do this for all mine and the info is great.

For reference, I'm about to start up my 2j and have a 6466 with the divided .84 housing.

This same housing on a worked over 2.5l with a 6262 only produced 34lbs drive pressure at 27lbs of boost pressure. So unless you looking to run max boost like 40psi on race gas and drag the car at 800whp, id say run it and feel it out.



Okey, thanks for the great info :)
The tuner said that i should drill and tap 1/8 NPT threads on the turbo-exhaust housing, so he could read the pressure there. So if i Understand you correctly, when the pressure i measure at the turbo is twise what the boost pressure is, then the housing is too small? (I'm sorry that I seem a bit slow, but my english isnt up to date)

And when I chose the turbo and A/R size it was because i wanted power at low RPM's because its only going to be a street car, and I'm not going past 500whp... I'm hoping for 400-450whp.. what kind of torque do you think i will see at those levels?
I have AEM ecu and a stock Aristo engine
And the turbo is a CT4, Triple CERAMIC Bearings, because I heard that it was a fast spooler...
 

nathaninwa

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Jul 1, 2012
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Aberdeen, WA
Perfect. I bet that housing is just the right size. Still log it, but try to get it in the header collector rather than the housing. Nothing wrong with it there, just don't want to make a sellable housing not anymore to a potential buyer.

And yes, if 20psi in the intake, no more than 40psi in the collector.

So, get setup and log the backpressure.

And I don't really know on the tq, but I'm typically seeing about the same tq/hp numbers on pump gas.
 

Dylan JZ

一番 King
Oct 18, 2007
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湾岸せん
like nathaninwa said, I'd feel it out and check the logs for pressure ratios, but keep in mind that housing is probably less than ideal for higher revs. A .64 T4 on a 1J (2.5L) is about as good as it gets in terms of a housing match for the entire RPM band, so being that you are a full half a liter larger it's going to make a difference, I'm just not sure by how much.

one thing is for certain though, it will make power fast and hard on the low end just like what you stated above that you want.
 

nathaninwa

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Jul 1, 2012
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Aberdeen, WA
Your welcome. I have thrown to much money at stuff on the basis of so and so said. I like to test as much as I can, and be certain I need the upgrade. I do try to make educated guess's at what I want, but none the less, I like to tinker and enjoy tweekin like that.

Once my car starts one of my first moves is to see if my IC is to small (3 inch core, 12x22) by loggin the pressure drop and the temp in vs out. Only then will I try to chop up the core support to fit a 4 inch core.
 

Turbo Habanero

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Apr 28, 2009
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Tucson,AZ
nathaninwa said:
. Only then will I try to chop up the core support to fit a 4 inch core.

Not that it matters much i fit my 4in core without Any cutting to the core support. Or modification to the bumper.