Rx-7 Rally Car v3.0!

seems they have 3 kits. So i want 100 ft-lb or 250 ft-lb breakaway torque?

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First Rally: 2010 First RallyX: 2004 (a bunch)
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another good question, 4.88 or 5.29. I have been back and forth on this for some time.

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First Rally: 2010 First RallyX: 2004 (a bunch)
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5.29 and a .80 (or better a .90) 5th gear if you're running 195/70r15s.
The 4.88 is possible just a little too high in the Volvo rally car.

Quote
Gravity Fed
seems they have 3 kits. So i want 100 ft-lb or 250 ft-lb breakaway torque?

We've used the 250lb-ft kits in the ecoboost xratty, and now in the 8in axle that has yet to be installed in the Volvo. No discernible corner entry understeer from the higher preload. They can get a little noisy/chattery if you don't use a LSD diff oil. But since they're just steel plates, you can basically run whatever you want for diff oil and they'll be a-okay.

I got the 250lb kit. Seems to be the choice for rally use. You wanna be able to do some proper skids don't ya!?

I unfortunately, didn't have enough time with mine installed to offer a thought on how it drives, when trying to have fun. Honestly I wouldn't take my opinion anyway! I can say mine had no chatter/ noise cruising around.

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Robert Culbertson
5.29 and a .80 (or better a .90) 5th gear if you're running 195/70r15s.
The 4.88 is possible just a little too high in the Volvo rally car.

Robert what the fuck are you doing here advising people? Gawddamn dude just where do you get off thinking you know enough to advise on shit when you are so often off base?


.9 5th? WTF. Show me a serious box that has just a 10% "next to top to top" spread.
You won't find it.

If you studied more real shit than talking to just talk you'd see a remarkable consistancy over decades of around 14%..ie 1,14 to 1,0:1, or 1,0:1 to 0,86 all kinds of cars for 30-40 years--rally cars..
And 4.88 too "high"? since the rise of Inter-net experts the traditional meanings of "high" and "low" have been muddled by 20 somethings blabbering.. Do you mean its too "short" or too "long"? Running out of revs or running out of mph?

I ask because you seem to have some very "unique" ideas like using a 3,9 instead of the 4,3 for the turbo Xratty..a choice which mildly put is utterly bewildering...and that's being polite..Never did quite grasp what the "reasoning" was there, and no way I can figure out why a person would do that intentionally as long as there was easy options.

For Alex the first question is if he intends to be a lemming and use tires way too fat and tall.. Then the question is can he be happy with the box he has with the 4th he has and just use 5th on transits since it is a) not the strongest gear, b) its a dog leg to select it which might be fucking stupid exciting at 100+ mph and c) 5,29 will of course render 1st gear utterly useless..
Great idea, now he has a 3 speed box: 1st 15,0:1 put it on the trailer gear and skyhigh overdrive just for highway cruise/transits..
4.88 is 14;1 and that really is short but it sure is nice in the 2nd/3rd/4th range..

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John Vanlandingham
Sleezattle, WA, USA

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A 0.9 5th isn't a bad deal when you don't have the power to push a bigger gear.
My thoughts are this. In the Volvo with 4.88 and 195/70 tires (and with 215/65s), it will spend a significant amount of time on the rev limiter in 4th (1:1) at Olympus, Idaho, and Oregon Trail... but 5th is never used because it's a Z Spec t5 with a near useless 5th gear and 1st that's only good for loading onto the trailer. Anyways, 5.29 with a 0.9 5th is just a smidge longer that 4.88 and 4th. Though the 0.9 is a huge pain to add, the benefit is you can disassemble the gear box without cutting the bearing in half first.
Even if Alex keeps the gearbox stock, the added benefit from the lower gearing will outweigh the few seconds lost on long straights.

1st gear @ 2.95:1 is near useless in the Volvo on stage. We launch in 2nd most of the time unless it's a STEEP uphill.

Too high as in it's long, and a shorter gear would be more bettererer.

The reason the Xratty has a 3.9 is the 4.3 were worn out and went bad just a week before the rally. Hence the scramble to find a Supra diff, all I could find in the 3 phone calls I made was a good 3.9. So in it went. Will probably go back to a 4.3 when the time comes, and toss in a .8 5th gear as well.



Edited 1 time(s). Last edit at 04/05/2017 11:37AM by Robert Culbertson.

not to interject into my own thread BUT,

i went with 5.29. I spoke with many rotary people who used to race. They all said go for the 5.29. 4.88 if i need to reach higher speeds on a track.

So 5.29 it is.

My box is the WC T5 out of a 5.0. But that box will eventually get a different gearset. eventually. maybe.

really though, I should have a good 3 - 4 back and forth shifting experience with this set up. And this is a 13b. So my rpm limit is going to be significantly higher than the aforementioned volvo.

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
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Last Updated, Apr 9, 2023

Welcome back! What's the rev limit on the 13b?
And gearsets? Do tell!

well, Weir performance is literally up the way from me so I think I will just stop in.

Rpm wise, i will likely keep it under 7,500 since this motor is stock and old. The next motor would likely a bit higher.

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Quote
Gravity Fed
well, Weir performance is literally up the way from me so I think I will just stop in.

Rpm wise, i will likely keep it under 7,500 since this motor is stock and old. The next motor would likely a bit higher.

That's what the Volvo revs to. The 5.29 should be nice!

Quote
john vanlandingham

Quote
Robert Culbertson
5.29 and a .80 (or better a .90) 5th gear if you're running 195/70r15s.
The 4.88 is possible just a little too high in the Volvo rally car.

.9 5th? WTF. Show me a serious box that has just a 10% "next to top to top" spread.
You won't find it.

Just because its 0.04 to short, shouldnt mean its a useless gear then? why not have it anyway instead of having a 5-geared 3speed?

I think i have the

2.95
1.94
1.34
1.1
0.76

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Quote
Gravity Fed
I think i have the

2.95
1.94
1.34
1.1
0.76

Z-spec or GM?

Ford

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023