4 replies to this topic

[kyller]

edit : title should say 1st gen crx/3rd gen civic

I'm sure this has been covered in the past (but can't find really old threads), but I'm trying to find a good ratio combination for a specific purpose.

Basically, I have about 7 5sp transmissions. I've gone through every single one. Each of them have the same 2nd/3rd gear (1.76/1.19), and I've come across a 4.25/4.27/4.40 final drive.

I race on an oval track, and usually run carb'd, turning roughly 8000+rpms. With recent rule changes, I have to find mroe speed. We switch to FI, and notice a ton more acceleration, but have to fight with a low rev limiter. The car Flies off the corner in second, and absolutely sucks in 3rd. So the best scenario I've used is running the FI, and shifting into 3rd halfway down each straight....That is not easy, and even harder, is down shifting and popping the clutch to slow down. 25 lap race = 100 shifts...Any gain you get with the fuel injection, is all lost with 1 single missed or slow shift.

So, basically I have 2 options. I can try and find a much shorter 3rd or final drive, or a taller 2nd/final to jus ttouch the rev limiter at the end of the straight. We hit roughly 70 mph, so I use that as a marker...and that puts us at 7900 rpm with 1.76/4.40, and about 7600 with the 4.27 final. To be around 7000 rpms, I would need a 3.8 final drive (roughly) with some room to still go faster before the limiter.

I've looked into the integra transmissions, and the gearing is better, but unforunately the shafts are different sizes, and it's a different setup, so they are not interchangeable. Which sucks, since all gears changeable on both shafts, where the civic ones you cant change the gears on the input shaft.

Only thing I have come up with, is I've seen some people mention the final drives out of the 2nd gen civics, Does anyone know whether that is possible to change those? I've seen the exploded view of the transmission, and the set inside is idnetical, but those diagrams are always accurate.

And 2nd question, anyone else have any other suggestions? The HF gears are impossible to find, or else I would be having so much trouble.

Edited by kyller, 25 May 2012 - 09:34 AM.

[Mark L]

Curious which (carbs) are you running?
1. Have you thought about modifying the ECU to remove the rev limiter?

2. You could switch to a 86-89 Integra trans, if you change to a wagon 4wd block. If you were turning 8K, I bet you have some $$$ in your current lower end though.

3.Taller Tires? Can you stagger?

Mark

[jsgprod]

Try to find (or see if someone here has one) one of the old 4 speed gearboxes. They came with a 3.722 FD ratio and 1.66:1 second gear.
If you can find a good machinist the 3.722 FD can be made to work inside a 5 sp box. which would drop you rpm to about 67-6800 in 2nd. According to the info you mentioned.

Or install a Megasquirt and you can set the rev limit wherever you want. Not to mention infinitely tunable.

[kyller]

Unfortunately, we can not alter the stock ECU (rules say no), and they are good at catching stuff like that. And we run the stock (reman'd) DX carb for 86-87 ordered from napa. Believe it or not, there's no money in the bottom end at all. We used to turn this thing at 8500 rpm's literally all day long, with stock induction, head and bottom end. Only exception was ARP rod bolts, which is their main weakness.

When you say "old 4sp gearbox", what year are you refering to? I'm in Canada, and we're limited to the 4sp that have the same ratio's that the 5 speeds had, just less 5th gear.

Edit : And to clarify, when I say "stock", it is rebuilt, but a mix and match of parts from that generation.

Edited by kyller, 25 May 2012 - 02:24 PM.

[kyller]

Also, tires size is kind of restricted. Taller tires = major loss in HP. That, and the tires we run are only available in the 195/60/14.

MY biggest problem is budget. I work at a scrap yard, so I can get the transmissions, but, since they were all interchangable, there's no guarantee the trans is actually the original one based on model. I can't afford to order one in (Again, I'm in Canada), to have it be the wrong one.