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Discussion Starter #1
Anyone know the specs for the 98-99 GM 8 turbo? I am looking to use this turbo on another engine project but not sure if it will work, I have searched all over the net for A/R ratio's and compressor maps for it but can't find anything. I finally came across this website but did a search and still found nothing, so hopefully someone out there can help.


Thanks guys!
 

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The GM8 is an IHI RHC6. There's limited information on it, but there are a few graphs available online if you look hard.

Good luck!
 

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Discussion Starter #3
cool, thanks, hopefully that new deswcription will help, I did find specs on a bunch of Ihi turbo's but thye had different names then GM8, I'll have to check, maybe that turbo was listed.
 

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I called these folks today listed on IHI's site as vendor to repair the GM-8


Turbo & Electric
2408 Grand Avenue
Phoenix, AZ. 85009
800-738-8726


They only build to stock specs which are still propietary from IHI so no AR info or flow maps out yet for GM-8, they did say it was from what they could tell very close to Garret T3 or T4 and said AR should be pretty large to flow the 6.5.
 

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Wow, what a terrible graph that is. I'm wondering if the RHC6 isn't interchangeable with the RHF6... maybe just a newer model? Who knows. What application are you looking to put a pair on? I'm going to put a pair on my twin-turbo Jag V12 project... (5.3L so each turbo will be feeding 2.65L) running ~15 psi boost. My calculations show it should work and be reasonably quick-spooling. Another turbo of similar spec is the Holset HX35 off of the Dodge Ram Cummins turbo diesel, but I believe that the GM8 will be faster-spooling. The A/R on the HX35 is I believe 1.06... way too high for displacements much below 4.0L.
 

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Discussion Starter #7
Its my uncle who wants to use it on a custom Turbo 4 cyl motor from a turbo coupe (2.3L) We are dropping this motor into an older Mazda Pickup truck, tubbing it out and everything, my uncle is a fabricator adn this is gonna be a custom shop truck with drag use.
 

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I had a feeling you were going to use it for something along those lines. Yes, the GM8 or a Holset HX35 will do you just fine. I haven't seen the GM8 used on any projects, but I HAVE seen the HX35 used on a large number (mainly because there's more info on them, I'm guessing). On a 2.3L you can get a good 30 psi out of them.

Good luck!
 

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Also, you asked initially about the 98-99 GM8 turbo... I think that the same turbo was used from '96 on (possibly from '94 on, I forget) so if you don't already have the turbo you'll planning on using that gives you some more flexibility in what to look for.
 

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Discussion Starter #10
the GM8 is from 98-99 previous years are Gm4 and Gm6 I believe, at least thats what one web site said that I found. Thanks for the info that should help.
 

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My truck is a '97 and has a GM8 and I'm pretty certain they didn't change from the GM8 afterwards. You can check on the turbo itself. It will say what kind it is on the compressor housing.

Good luck.
 
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