Changing Turbo Exhaust Housings

[supraguy31]

Hey Yall, Got a Question and Im not for sure where to ask. My Turbo setup is great and I love it but My Exhaust housing on my turbo is like a .86AR.
Question is What would I need to do to change the Exhaust housing to something around a .68 or .70AR. What would be the Benefits of this

Right now I have a T66 on my 7MGTE converted MKII and Im not reaching full boost until 3800-4000 RPMs.

Thanks
Robert

 

[Adjuster]

Floor it more.
You could go to a smaller AR hot side, but might only spool up your turbo slightly sooner, and it would limit top end flow..

IIRC, Zazzn ran a .53... and loved the spool, but I don't think his was a T66...? Not sure on that actually.

My Master Power turbo has a .63 hot side, but I have not actually run this dang turbo yet... LOL (Has a 69mm compressor.)

I'm hoping with my engine it will prove to be both quick spooling, and produce the 650rwhp that I'm looking for (Ok, so 600 would be fine, the other 50 would be just gravy... LOL)

 

[supraguy31]

Ive heard that since my Exhaust housing is so big and Im running a 2MM MHG that both them together would be a good reason for my late spool. Either go to a Small HG or go to a Smaller Exhaust Housing.

Just not for sure which one would be ther better choice if not Both

Robert

 

[Idealsupra]

Ive heard that since my Exhaust housing is so big and Im running a 2MM MHG that both them together would be a good reason for my late spool. Either go to a Small HG or go to a Smaller Exhaust Housing.

Just not for sure which one would be ther better choice if not Both

Robert

first off what is considered "late spool"?

secondly they say the hg due to the compression however how much was taken off the block and head to warrant the 2mm hg? IE: did you raise or lower your compression. the higher the compression the faster the spool time however the higher the compression the less boost you can ultimately safely run without issues of detonation.

honestly a .86 AR isnt big at all for a 3 liter. especially with the stroke on the 7m. personally id say youre fine. and as stated above going smaller will maybe gain you 100-200rpm of spool time but in the long run it will minimize your maximum horsepower capabilities.

 

[starscream5000]

I would look into increasing the air flow of the head and it's manifolds (porting) first. This should help a little with spool, plus it's free, but you would have to take the head off to do it . Maybe start with gasket matching the manifolds and see what type of gains you get from that).

 

[IJ.]

Gasket matching the exhausts on a 7M hurts performance

 

[starscream5000]

Just as long as you leave like 1mm on the exhaust ports on the head (reversion dam) you should be fine right?

 

[IJ.]

Yep that's it

 

[supraguy@aol]

I'm doing some porting now on my spare head. Got two of the cylinders done;
unshrouding valves, smoothing cc, and flush grinding the intake valve seats.
I Don't expect much, but like the guy said- it's free(not including all the dremel bits i've bought.)

 

[IJ.]

SG: A tip I can give you on this is to perform the same cut on all chambers then the next on all and so on so you take advantage of muscle memory.

If you do all cuts on a chamber then move on you make it harder to be consistant across all 6.

Hope this helps.
(ported MANY heads when I was younger and used to make go/no go gauges to help out with this)

 

[boostadikt]

full boost at 4000 is not bad at all........ i had a .69 exhaust housing and was seeng full boost around 3800-4000, the housing warped so i had to buy a new one and a shop near me had a .96 in stock so that is what im running now and i see full boost at 4600-4800 and im still not complaining cuz when it hits im gone.

 

[hottscennessey]

My Master Power turbo has a .63 hot side, but I have not actually run this dang turbo yet... LOL (Has a 69mm compressor.)

I run this turbo on my 2JZGE.. well mines a .68 A/R, spool is great.. I'm sure you'll like it

 

[MRSUPRA]

the main reason you have late spool is because you have a big turbo. A T66 can support 700rwhp. DO you plan on making that kind of power. If not, why have such a big turbo in the first place.

But you are right, a smaller exhaust housing will definantly help get you get ealier spool. And more power under ther curve. I'm not sure why some people are so fixated on big exhaust housings and the least backpressure. There was a guy on supraforums who just dynoed at 720rwhp with a .68A/R on a 67mm turbo.

 

[supraguy31]

My goal is just to be in the 500hp Club in a MKII. There arent many of us that have made it that far, Especially in a MKII. Actually after looking at the turbo, I think I have an .96AR. Ive sent all the Manufactor and Model Number to a few guys on the forum and they are trying to see what this turbo is in AR comparison.

Robert

 

[starscream5000]

There are more than you think .

 

[Suprapowaz!(2)]

I thought a T66 had a 66mm compressor wheel. So I figured a 67mm turbo was a tad bit bigger? :dunno: I thougth that the new thing for turbos was to label them with the size of their compressor wheel measurement. Am I wrong about that?

 

[starscream5000]

Start here for turbo terminology: http://www.supramania.com/forums/showthread.php?t=38860 This should clear up most misconceptions on turbos .

 

[drjonez]

Gasket matching the exhausts on a 7M hurts performance

you've got that right!

as for the smaller turbine housing thing, if only you could search on SF. there was a fantastic comparo someone did between a .58 and a .8?....NO loss in peak power, just much better spool.

 

[Intothenight19]

I run a 1.00 on my TO4r and see 15psi @ 4200rpms and it rips so what your experiencing isn't bad.