Help needed choosing best gear ratio combination

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12-21-17, 05:31 PM

Ernstudet22

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Help needed choosing best gear ratio combination

I have a 500 horsepower single turbo FD. I am upgrading to a t56 and a ford 8.8 irs. I want to gear it for the 1/4 mile. I've done all the starting line ratio calculations and differential calculations. The calculations point towards a 2.66 1st gear and either a 4.56 or 4.88 ring and pinion. But then I read a few older posts and I'm concerned that the R&P won't be tall enough. Would a 2.97 first with 4.10 gears be better? I would really appreciate any real world experience. Thanks

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12-22-17, 04:12 AM

C. Ludwig

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What's the rev range of the engine? What rpm do you want to trap at? What gear do you want to trap in? What size tire?

Where in Indiana are you from?

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12-22-17, 08:05 AM

Ernstudet22

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The engine makes really good power from 5000 to 7800. I'm running a Borg Warner efr 8374 with stock ports. I would like to trap under 8000 in 4th gear (7500-7800 would be ideal). Tire diameter is 26". I live in the northwest corner of Indiana very close to the southernmost tip of Lake Michigan.
I've been drag racing on and off for 28 years now and normally would have no problem making this decision if it were a n/a V8. But because of the loading effects on a turbo rotary, I'm somewhat lost.

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12-22-17, 01:09 PM

BLUE TII

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Quote:

Ernstudet22

The engine makes really good power from 5000 to 7800. I'm running a Borg Warner efr 8374 with stock ports.

This statement is going to confuse people.

The reason for the late power on this set-up (which usually dies up top) is because the OP has boost creep.

OP- you should tune for whatever your peak boost is as your boost setting to really wake up the midrange on the EFR 8374 set-up.

This will allow you to leave the line with a taller 1st gear and smooth out any mistakes in shifting or throttle modulation with the added midrange torque.

That said, I would put in whatever T56 gears will be streetable for your car since an EFR 8374 on stock ports isn't any kind of drag set-up (ie, your not hunting for records).