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Old 10-16-2019, 10:23 AM   #1
jfj85
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Default What size S48x compressor wheel would be best

I've decided to go straight to a t6 flanged s480 chassis turbo. Full weight '69 Camaro street/strip (mostly street), auto with a 3k stall and 3.73s but will be swapping to a t56 magnum at some point.

Combo is a 93 octane/meth injected 400ci SBC, Dart little M block, 8.5:1 cr, AFR 190cc 2.02 valved heads, hydraulic roller - cam specs unknown. It was ground for the 177 roots blower I had previously. I can swap cams as needed later on. Single turbo setup with 1 5/8" headers divided to the flange. Crossover will be 2.25" or 2.5". It'll be running 5" off the turbo to 4" then short side exit exhaust (4" oval tubing) with no muffler.

What compressor wheel would be best suited to make a fairly responsive street car with a 1.32 A/R and 96/88 turbine? 80, 85 or 88mm? I'm more concerned with having a well matched setup which spools reasonably with no back pressure issues over all-out max power. Thanks
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Old 10-17-2019, 09:46 PM   #2
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Default Re: What size S48x compressor wheel would be best

I had a S483 on a 383 sbf Windsor with Victor jr heads and a .700 lift cam. I had major back pressure issues with that turbine wheel at 21lbs of boost.
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Old 10-17-2019, 10:17 PM   #3
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Default Re: What size S48x compressor wheel would be best

Quote:
Originally Posted by jfj85 View Post
I've decided to go straight to a t6 flanged s480 chassis turbo. Full weight '69 Camaro street/strip (mostly street), auto with a 3k stall and 3.73s but will be swapping to a t56 magnum at some point.

Combo is a 93 octane/meth injected 400ci SBC, Dart little M block, 8.5:1 cr, AFR 190cc 2.02 valved heads, hydraulic roller - cam specs unknown. It was ground for the 177 roots blower I had previously. I can swap cams as needed later on. Single turbo setup with 1 5/8" headers divided to the flange. Crossover will be 2.25" or 2.5". It'll be running 5" off the turbo to 4" then short side exit exhaust (4" oval tubing) with no muffler.

What compressor wheel would be best suited to make a fairly responsive street car with a 1.32 A/R and 96/88 turbine? 80, 85 or 88mm? I'm more concerned with having a well matched setup which spools reasonably with no back pressure issues over all-out max power. Thanks
It's going to have back pressure issues with that displacement and the cam that's in it will probably make matters even worse. The compressor wheel has little to do with spool compared to the hot side setup or cam specs. I run two of those turbos with 80mm compressor wheels and 1.32A/R Bullseye v-band SS housings. It's 402cuin on methanol and will make 10psi in 1.2sec from going WOT on transbrake. If you were 50 - 80cuin less displacement I'd say go for it. You would be better off with a pair of S366 turbos on it in my opinion.
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Old 10-18-2019, 09:46 AM   #4
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I really need to stay with the single turbo setup to avoid a whole lot of rework. What would be a good street turbo to avoid back pressure issues? I'll be keeping it at 16 to 18 psi max, probably set it at 12 or 14 honestly. I have no where near the tire to hold more.

I was in hopes a t6 flanged s480 with a 1.32 AR and 96/88 wheel would be ok at mild boost levels if I keep the downpipe as large as possible and limit exhaust restriction. Would a race cover or the big AR be better, even on the street? I was asking about compressor wheel size because the compressor output for an 80mm billet wheel would seem to suit what I'm doing for the street but is that too small in reality? I was always under the impression having a compressor wheel bigger than what's needed just hung extra weight off the shaft and compromised low end efficiency. Thanks for the replies.
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Old 10-18-2019, 10:42 AM   #5
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Default Re: What size S48x compressor wheel would be best

If that's all the boost you are going to run it will be fine. You could always go to a 1.58A/R housing down the road if you want to really lean on it in the future. It would be alot more responsive and spool quicker with at least another full point of compression. 8.5CR is too low in my opinion. I never go below 9.5CR even on street driven combos.
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Old 10-18-2019, 10:50 AM   #6
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Awesome, thanks. From the actual backpressure data I've seen on other builds they were staying between 1.5:1 and 1.75:1 with a similar setup and boost levels. I figure I'll be slightly higher but not dangerously.

From experience, would the bigger compressor wheel (like an 85 or 8 be beneficial in this case?
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Old 10-18-2019, 11:53 AM   #7
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Default Re: What size S48x compressor wheel would be best

If you can I know a lot of people don’t like it go to vsracing website they have a similar turbo with a bigger turbine wheel. I ran the 1.5 housing also and it only let me get 1-2 pounds more of boost
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Old 10-18-2019, 01:05 PM   #8
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Default Re: What size S48x compressor wheel would be best

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Originally Posted by jfj85 View Post
Awesome, thanks. From the actual backpressure data I've seen on other builds they were staying between 1.5:1 and 1.75:1 with a similar setup and boost levels. I figure I'll be slightly higher but not dangerously.

From experience, would the bigger compressor wheel (like an 85 or 8 be beneficial in this case?
An 83mm to 85mm would be fine. Just keep in mind that the turbo is pretty much done at 2:1 back pressure, hence my original statement.
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Old 10-18-2019, 06:43 PM   #9
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Default Re: What size S48x compressor wheel would be best

Im running a Forced Induction Turbo Billet S485 1.32/96 on a 3.75 stroke , 6" rod , 4.060 bore sbc . AFR 195 street heads .

Aprox 8.8:1 .

Makes 34psi with the gate pinned shut . C16 fuel . Water to Air .

Calculators say around 1350 HP

Not ideal , but it does what I need it to do .
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