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The mkiv Supra Owners Club

Effects of A/R in turbo's


dangerous brain

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I just bought a T67DBB 0.70 A/R compressor side, 0.68 A/R exhaust side turbo.

 

The unit I have in my car is either a T61 (which is what I was told) or a T67 which it actually looks like with 0.70 A/R compressor side and 0.96 A/R exhaust side.

 

I am going to fit the new one in the old ones place and see what the effects actually are. I had the car dyno'd almost directly before I am going to undertake the swap. What do you guys reckon the differences will be?? Will I now lose top end power which at 455bhp wasn't great?

 

Is a T67 with a 0.96 A/R a huge power turbo?

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There is a P trim and a GTQ trim for the Precision T67.

The P is the .68ar and the GTQ is a .84...I don't know of any others.

 

The only thing that will stop a T67 pushing to the red line will be a lack of cam duration....ie an inability to actually get the air in and out of the engine fast enough.

 

Divided and Non divided housings have different A/R's for the same flow rate because the divided housings have a huge chunk of metal in the exhaust stream.

 

Divided housings are roughly .25 larger than their undivided conterparts.

Garrett tend to use divided and so their exhaust housings feature larger A/R's than Precision based turbos.

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I have the .96 divided garrett turbine housing and was not impressed.

 

I have just ordered a pair of non divided precision turbine housings of .68 and a .82 housing and spent all today stripping the turbo off and getting it ready to try the '68 first.

 

Garrett say that the ar of the compressor makes bog all difference.

 

The '96 spools pretty early on a pull, but the throttle response is pants. Looking forward to the .68, just hope it pulls to the redline, and will post up the results once I have made the swap.

 

The only thing is if the '68 works well I will not be arsed to try the '82 housing...

 

there are lots of us using medium/large sized turbos with small turbine ar's that have graphs pulling hard to the redline.

 

Is a T67 with a 0.96 A/R a huge power turbo?

If thats the ar of the turbine I'd bet it won't be that much more powerful than the .68 unless you have an 8k rev limiter, but a significant amount less responsive on and off the throttle. Still I am guessing until next week!

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Hi Mike,

Do you have a divided manifold?

 

Would you be interested in selling the .96 back housing? I'd like to try it on mine as I believe it would work better with my div tang HKS manifold and plain 4088 than my current non-divided back housing does.

 

I was just about to order an .82 housing from Kyle (I think you're getting yours from hm too) but I'd like to try the div .96 really as I'm only looking for a little spool improvement.

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Hi Mike,

Do you have a divided manifold?

 

Would you be interested in selling the .96 back housing? I'd like to try it on mine as I believe it would work better with my div tang HKS manifold and plain 4088 than my current non-divided back housing does.

 

I was just about to order an .82 housing from Kyle (I think you're getting yours from hm too) but I'd like to try the div .96 really as I'm only looking for a little spool improvement.

 

 

Mate, hold onto your credit card for a few days!

 

I have a .96 that is divided; you can have no worries, that came off this afternoon, and a .82 non and .68 non coming mid way through next week. I'm pretty sure I'm going .68, so the .82 may be straight up for sale too. I only bought the .82 as well incase the .68 is a big bottleneck, but everything I have seen so far suggests it will be the best bet.

 

They cost me 205 bucks per housing.

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Tony,

They're $205 plus $100 shipping from the US.

Shipping is cheaper if ordering more than one though.

 

 

Mike,

Will do mate.

I'm only interested in the .96 div housing as I understand it will work like a smaller AR with my div tang manifold. (You didn't answer my q about whether your manifold is divided)

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Do you mean $205 or £205?

I just ordered a pair of housings for my turbo's from Blitz that came in at £1100 for the pair! :shock:

 

Jakes right matey... 205 usd for a precision housing - the same one as terry used on the gt35 that was already on the same car. I hate to say it but £1100 sound a bit expensive for 5... I think you have spent too long in F1 :innocent:

 

Mike,

Will do mate.

I'm only interested in the .96 div housing as I understand it will work like a smaller AR with my div tang manifold. (You didn't answer my q about whether your manifold is divided)

 

My .96 is most definately divided.

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Yall let me know how it works out and if i can help out anyway possible.

 

Mike i sent your stuff priority too so you should have it Monday or Tuesday.

 

Thanks again guys

 

They arrived this morning.. I only ordered them last monday.. that's 7 days to get them here in my hand after I mailed you! :blink:

 

I posted pics of all three on another thread.. big physical difference between the divided and non divided.

 

Tonight I will be mostly in the garage!

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Originally Posted by Jake viewpost.gif

Mike,

Will do mate.

I'm only interested in the .96 div housing as I understand it will work like a smaller AR with my div tang manifold. (You didn't answer my q about whether your manifold is divided)

 

 

My .96 is most definately divided.

It's your manifold I'm asking about though Mike, not the turbo. There's no point putting a divided housing on a non-divided manifold.
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Hi Jake, sorry mate, evey time I fail to answer your question. My manifold is divided, and I used a divided manifold gasket on the .95 divided housing too, so the whole thing was the real deal.

 

I'm not putting them on the dyno... I get it close with fuel pressure and the fcon does the rest. plus you will have to make do with my ass dyno measurements. :D the spool was never a probem, I was getting good liniar boost building after 3k, but the throttle response was shocking.

 

If the .68 works well I will not bother trying the .81

 

been out tonight buying a new runaround.. so I will be under the bonnet tomorrow night.

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OK so reading all this stuff I decided to see if my compressor housing would be a straight swap from old turbo to new one and bugger me ole lugs it is. Thats a major bonus as the new turbo has some funky 90 degree elbow welded onto the outlet from the compressor housing. Now looking at the exhaust side I am hopeful that I will also be able to use my old exhaust housing forgoing the requirement to fit an adapter to the downpipe or a new flange to the downpipe, and also saving me the job of fitting the EGT probe into the new housing.

 

If these parts are all interchangeable then would I be right in assuming that the two turbo's are identical in size?? IE the new turbo is a T67 so if the housings are interchangeable than my old turbo is also for sure a T67?

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http://www.spicyweasel.com/bryan/image-cache/Bryan%27s%20Car/thor%20dyno_disp800.jpg

 

http://www.spicyweasel.com/bryan/image-cache/Bryan%27s%20Car/dan%20dyno_disp800.jpg

 

As promised in a thread I can't find now a copy of my dyno prints from two weeks or so ago.

Lets see what the ones with the new tubby look like.

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Ran the car today for a short stint. I am not 100% sure but it feels like it is pulling a helluva lot harder than before. Throttle response is also better. Second gear seems to disappear quicker than before. I haven't really gunned it as I didn't have anything monitoring the gauge situation other than MK1 eyeball and I don't know how long a tubby needs to bed in. In third gear boost comes into positive by just over 2000 and hits a bar by about 3800 which considering the housing size isn't surprising.

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