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Discussion Starter #1 (Edited)
What turbo for 281ci ModMotor 26x8.5 1/8th mile class (MT or GY tires only)

Small Blocks Single Blower/Turbo (Max F1 or 88mm) ......3000 lbs
Small Blocks Single Blower/Turbo (Max F2 or 94mm) ......3100 lbs
Small Blocks Single Blower/Turbo (Unlimited) .................3200 lbsSmall Blocks Twin Turbo (Max 76mm) ..............................3300 lbs


Turbocharger (Up to 98mm) or Twin Turbocharger (72MM Max Each) 98mm Single Turbochargers are permitted in accordance with the following requirements:
1) Turbocharger must be of conventional impeller and housing design and type.
2) Turbocharger is limited to a maximum size of 3.860 inches (98mm) inducer diameter at the point where the leading edge of the compressor wheel meets the inlet housing.
3) Compressor cover inlet is permitted a maximum inlet diameter of 3.951 inches (100.36mm)
4) Compressor Wheel to housing clearance must maintain a maximum 0.091 (2.3114mm) clearance beginning from a) the leading edge of the compressor wheel where it meets the inlet of the compressor housing, to b) the transition point where the trailing edge of the compressor wheel meets the volute.
5) All air entering the turbocharger must pass through the turbocharger inlet.
6) Injection of any liquid, gas, or any other substance into the inlet or exhaust housing prohibited.
7) Compressor wheel contour must be continuous features from the inducer to the exducer (no "stepped" wheels).

He said billet wheel is ok so what does "conventional impeller" mean?


3200lbs now with 1.80 PG Have not chosen Cams or gears yet


TIA
 

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Gt4788 and put the pig on a diet to make weight. 3.73-3.90 rear gear and cam it to pull 7600-7800. get a stall thatll go 4500 easy so you can tune the launch rpm. I dont think a large frame 94 would run as well. Im prolly wrong thou. If you went that route an F trim wheel and a 1.00 housing would be needed. I think itd be a slug with one that big thou.
 

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Forgot about the promod versions....if he went that route he could do the 91 for a little extra oomph. Thatd run well at 3100, but the lighter the better on that tire.
 

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Discussion Starter #6
Thanks Right now I have stock heads and cams GT47-80 3.55's and 28" goodyears PTC converter footbakes to 4000easy bump her in and she will go to 5200 but has gone a best 60' with the 2step at 4400 she flashes to 6300 at mid boost and calculates 5.5% slippage in the big end.

I was thinking of trying 4.10's (as I have a set) will help or hurt with the little tire and the 1.80 ? Was thinking of spinning her to ~8200

Trying to do this on a budget not sure if it will be possible
 

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4.10 with the 26 inch tire is gonna be pushing it. Thats alot of mechanical advantage and wheel speed. It might work.

The rules arent really even between twins and a big single. Hell a pair of billet 76's is easily 2300 hp. But a cast wheel 98 is only 1900. dunno if precision does a billet wheel that size and if the do i bet itd still be 100-150 shy.

If yer at 3200 now and start adding this turbo weight.. You could get over 3300 pretty quick. At that point twins would make sense. Pair of billet 6765's is 1900 hp worth of turbo. Cast wheel versions are 1700. But theres only like 100 bucks between them retail. Its worth the upgrade.

With no promods allowed... Id prolly go twin 6765 or maybe 6868.
 

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You did read where this is a 26x8.65 tire class right? 4.6 would have a hard time spooing a pair of 76's
 

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I had large frame f trim 88mm with .92 ar on my 5.4 dohc and it worked pretty good once u learn what u need to do to spool its not that bad. Either way if u run a large frame or twin 76 u gonna have to have loose converter and give it some rpm just have to lean on these mods a little bit. What kind of power is needed to compete those x275 large 88 makes tons of power though but they are big .
 

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All combo's are limited to the tire. And the lighter you are, the better this tire works! single 88mm will work best. Hell if they allow more weight breaks id go for a 85mm at 2900 or even a 80mm at 2800.

Where is this at and what are they running e.t. wise?
 

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I'm 3200 with 47-80 right now I can get her to 3100 I think but that next 100 will be near impossible with my limited budget

This is a new class for next year most think 5.30s
Id check out some weight reduction threads. My 95 with a 88mm and a-w intercooler sits at 2850-2900 with me in it (225). Only thing fiberglass is the hood. I dont have a cage yet but tack on a 100lbs max for that.
 
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