Exhaust AR on a TTA different than the GN turbo?

[2QUIK6]

I thought I had read somewhere that the exhaust A/R on the TTA turbo was .83 and on the GN it was .63, althought the turbos are exactly the same....can someone confirm this?

At would explain why the spoolup on my TTA was nothing like my GN in stock form.

 

[strikeeagle]

Not to my knowledge. I thought I read in an article by John Craig that the only difference is that the wastegate hole is very slightly larger in the TTA. I'll look into it.

 

[strikeeagle]

Paraphrasing John Craig:

'The 1989 TTA used a model TBO348 turbocharger (Garrett part number 466748-5006, GM part number 25536314). This turbocharger is identical to the 1986/1987 TR turbocharger except that the wastegate port is machined to a diameter of .912-.933 inches.'

(The TR wastegate is .82 inches.)

(The GNX turbine housing A/R is .82.)

HTH.

 

[2QUIK6]

ahh, I bet that's where it came from, the article I was reading from what I recall was saying the TTA turbo was very similar to the GNX except it wasn't a ceramic turbine..that's probably where they got it was an .8x housing also.
Thanks for the clarification.

 

[1BADDAM]

Originally posted by 2QUIK6
I thought I had read somewhere that the exhaust A/R on the TTA turbo was .83 and on the GN it was .63, althought the turbos are exactly the same....can someone confirm this?

At would explain why the spoolup on my TTA was nothing like my GN in stock form.

I noticed the same thing with my buddies GN vs the TTA, both were completely bone stock. His seemed to spool sooner in the RPM range. Only think I could attest this to was the difference in gearing, 3.42 vs 3.27

John Craig told me the same thing regarding the wastegate hole being larger in the TTA, to resolve a boost creep issue.