Gear ratio opinions

I'm thinking pretty seriously about a different gearbox for the new car (B18 honda civic). Initially would be running stock gearing + a lsd, later swapping gearset out to one of the "affordable" options from Gear-X or MFactory - which replace all but 2nd gear.

The issue is, there are 2 different options for 2nd gear: 1.9 and 2.105.

There's only two options for 1st - stock 3.23, and aftermarket 3.07.
Lots of options in the aftermarket for 3, 4, and 5.

(Looking at gearboxes with a 4.4 final with both)

With stock 1st and current engine, RPM drop from 6800-4038 with the 1.9.
With the 2.1, RPM drop is 6800-4474 - ~440 less drop than the 1.9.

With the aftermarket 1st, RPM drops to 4157 with the 1.9, 4606 with the 2.1 - a whopping 10 rpm difference from stock...

On paper it seems obvious to go for the 2.1 2nd, especially since I've got plenty of options to bring 3rd closer. BUT - the 2.1 2nd gear transmissions are more rare, more likely to have been abused, and more expensive.

I believe I can buy a 1.9 transmission and then swap the 2.1 mainshaft and gear from Honda in later, but the cost of OE parts makes this a bit of a wash (unless I buy a used 2.1 trans and discover damage to one of those parts, then of course new parts make sense).

Opinions? Save my pennies and get the 2.1? Get a 1.9 for cheap now, upgrade later? Build a Volvo instead?

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KF7RWG
http://www.utahrallygroup.com

a buddy of mine runs the m factory set on his rally civic and says he rarely sees i belive fourth. everything in a ls b after 5500 rpm is laggy from my experience so i didnt take it to 6200 plus there is no dig to turn after 5500. mind you this is an open diff. thats all i got. ill check with andrew, his setup is running 200 whp as well. dude im going open diff and cutting my teeth cheap cause diffs gearing and what jives with the power curve is an experience thing.

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All bridges burnt, island life is beauty

Just get the 4.9 final drive and be done with it. Yes the short ratio gearset from GearX is great but if you're only getting 6800 revs out of that anchor then there's less benefit for a short ratios than when it revs to 8500.

But what tire sizes do you run, also whats the torque line look like on your motor, where's the HP and TQ peaks? 1.9 vs 2.1 on 2nd gear might not make that much of a difference to the acceleration if your torque is down low and since its still 2nd it will still be ok.

ALSO more important is that a 1.9 will be closer to 3rd and you'll be doing a lot 2>3 and 3>2 gear changes, making things easier on the syncros.

Quote
Cosworth
Just get the 4.9 final drive and be done with it. Yes the short ratio gearset from GearX is great but if you're only getting 6800 revs out of that anchor then there's less benefit for a short ratios than when it revs to 8500.

But what tire sizes do you run, also whats the torque line look like on your motor, where's the HP and TQ peaks? 1.9 vs 2.1 on 2nd gear might not make that much of a difference to the acceleration if your torque is down low and since its still 2nd it will still be ok.

ALSO more important is that a 1.9 will be closer to 3rd and you'll be doing a lot 2>3 and 3>2 gear changes, making things easier on the syncros.

Yeah what up, dawg wif 6800? My ancient all cast iron pushrod V4 revs past 7100 like (snap) dat, mang--
Wot da Phoque, bra?

Shhhheeeeeet and gawddam Honja ought to do a nice safe happy 8500.

That's whe whole point of those little buggers make a million revs and via the magic of gearing make that into hard AX!

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
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My thinking was running a short enough gearset that the OE 4.4 would work. Yeah, the gearset is more expensive than the FD, but FD + buying the gearset later is still more money. Certainly possible that gearing it that short will put me into "needing to shift way too often for a synchro box" territory though.

Currently on 175/70-14s.

Wiki sez:
90-91 Only: 130 bhp @ 6000 rpm & 121 lb·ft @ 5000 rpm
92-93 Only: 140 bhp @ 6300 rpm & 127 lb·ft @ 5200 rpm

Also:

Quote
Cosworth
ALSO more important is that a 1.9 will be closer to 3rd and you'll be doing a lot 2>3 and 3>2 gear changes, making things easier on the syncros.

True, but the closest 3rd (1.695) seems like it might be too close to 1.9 - current setup hits 57 with 1.9 2nd, then all the way to 64 in that 3rd gear. (rpms drop to ~6k)
Same 3rd with the 2.1 tops out 2nd at 51, rpms drop to 5.5k

looking towards the future, 4.9 FD and shift at 8400...
1.9 hits 64 mph 1.695 hits 71, revs drop to 7.5k
2.1 hits 57, revs drop to 6.7k
Looking at some ITR dynos, that extra 800rpm drop doesn't seem like too much problem.

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KF7RWG
http://www.utahrallygroup.com

Quote
john vanlandingham
Yeah what up, dawg wif 6800? My ancient all cast iron pushrod V4 revs past 7100 like (snap) dat, mang--
Wot da Phoque, bra?

Shhhheeeeeet and gawddam Honja ought to do a nice safe happy 8500.

That's whe whole point of those little buggers make a million revs and via the magic of gearing make that into hard AX!

I dunno how high the base integra motors can safely rev (I'm sure it's well past 6800), but based on the <5 minutes of searching I've done, it sounds like it's a breathing issue - a cam may make a difference.

But, really gotta make a transmission plan, do some seam welding, and put it back together and race it a bit before I worry about more powah and revs!

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KF7RWG
http://www.utahrallygroup.com

Focus on the 2-3 shift as Paul suggested; the 1-2 shift is important in hilly, tight roads in relatively few spots, but you wil be doing a WHOLE lot more 2-3 and 3-2 shifts and a bad step there is a killer on speed. Your torque curve looks pretty decently flat so look less at the ratios that you have listed and see which ones keep you more centered in the torque range as speed goes up.

2.1 2nd gear if you can find it, with the straight-cut 4.9 final...Although that 1.9 2nd wont make a big difference.

You're not going to be in first gear very often at all...With the 4.9 final and a relatively torquey motor, you'll be able to take tight turns in 2nd gear with no issues.


As for the RPM thing, the LS head just isn't all that great. The VTEC head off of a GSR(B18C1) is a popular swap, as I'm sure you already know. That head, along with some cams and bolt-ons(header, intake, etc) will make some nice power.

I ended up (or, I should say, am in the process of) buying a trans from somebody getting out of racing.

2.1 2nd gear, MFactory clutch LSD, carbon synchros on 1-3, upgraded shift change holder assembly.
It's only money, right?

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KF7RWG
http://www.utahrallygroup.com