How do turbine wheel sizes affect turbo performance?

Sledheadxp800r

That was only my tow tune
Dec 13, 2010
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I'm basically looking for some info on how different size turbine wheels affect Turbo performance. I've been looking at s400 turbos and there's so many different turbine wheels available. 83mm 87mm 92mm 96mm. Any info would be great guys. Thanks
 

bullfrogjohnson

Big Girl!
Nov 20, 2006
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The bigger the wheel the more exhaust it can move per revolution. The bigger wheels have more surface area for the exhaust to act on and it will drive the compressor wheel harder. You will have better high rpm performance with lower drive pressure but you give up low rpm drivability.
 

Sledheadxp800r

That was only my tow tune
Dec 13, 2010
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The truck has an S475 1.32 a/r 83mm turbine wheel on it now. I will be running it mainly in 3.0 and hot diesel classes in New England. It has a stock motor but I have pistons, rods, studs, pushrods all just sitting and waiting to go in one of my trucks.
 

CurtisEmery

New member
Mar 21, 2008
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The 92 or 96 would be my choice. You will need a good n loose converter to get it to light. The 92 I think you can put in the t4 housings. The 96 I believe is more geared for the t6 foot.
 

Slammed2007Lbz

Super Spicy Tunaz
Feb 1, 2009
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Good Info. here guys!:thumb: I understand having to have a loose convertor to light a big turbo but what do ya'll mean when you say stay on top of it? Are you talking about like when the truck shifts and rpm's drop lower then the turbo would run back into a lag situation? So if you where sledpulling and the truck shifted and rpm's dropped you wouldn't be able to get the turbo back lit again?
 

cafryer

New member
May 5, 2011
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I would upgrade your fuel before the charger. I bet their is still power left on the table with the charger you are curently running if you could drive it harder.
 

LWATSON

future trans limpers
Jul 30, 2008
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What does AR mean? My charger is a 83/.90/75, just wondering what the .90 is and means. Sorry for the hyjack.
 
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Evan@InglewoodTrans

yerp
Vendor/Sponsor
Aug 5, 2010
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In short the A/R you're referring to is the size of the turbine housing. A .90 will spool better than for example a 1.10 but there is a trade off in the amount of flow you have through the turbine and in the end it's overall potential. It's a balance of having enough pressure to spool the turbo but also enough flow to get it out.
 
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Dozerboy

Well-known member
Jun 23, 2009
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Good Info. here guys!:thumb: I understand having to have a loose convertor to light a big turbo but what do ya'll mean when you say stay on top of it? Are you talking about like when the truck shifts and rpm's drop lower then the turbo would run back into a lag situation? So if you where sledpulling and the truck shifted and rpm's dropped you wouldn't be able to get the turbo back lit again?

That or normally just putting the load of the sled on the truck when you take off. It will pull the RPMs down a little and if your barley able to spool it your not going to be able to keep it spooled. When a pulling truck bogs down and doesn't make it 15' he didn't stay on top of it.

Stay on top of it=keeping the boost
 
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Rhall

Old Skooler
Aug 12, 2006
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From what ive seen lately, if you have the fuel to support it, the bigger turbines if designed well, will lug better than the small ones when matched to the right housing.
 
Sep 10, 2008
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Morehead City, North Carolina
Not trying to hyjack either but would there be a noticeable difference in driveability in swapping a/r housings on my gt4088r which has the 1.06 now to a .90 or less? I rarely see 3800 + rpm's and its pretty easy to fall off the charger when shifting 5th.


Thanks
 

cafryer

New member
May 5, 2011
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I think it would be easier to spool for sure but it shouldnt be that hard to spool as it is. What do you have for trans tuning?
 
Sep 10, 2008
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Morehead City, North Carolina
I think it would be easier to spool for sure but it shouldnt be that hard to spool as it is. What do you have for trans tuning?

I believe it is still stock TCM tune but im not positive. It already spools pretty darn fast but im always trying to find a way for improvement. I've tossed around the idea of pulling the charger, installing a batmowheel, polished cover and tighter housing. Any serious gains from a polished cover? I didn't know they were available for garrett turbos till just now.