shorter gearing for better acceleration

[vtecrcr4]

i have read many times that installing a shorter gear in the final drive will better your acceleration. i dont know anything about that and what is involved in it. can someone explain what this is supposed to do, how to do it and what should someone look for when performing this upgrade..
thanks

[sgvridgerunner]

Shorter gearing means that the driven gear itself is of larger diameter (more teeth) Assuming the driving gear is not changed, the mechanical advantage (leverage) will be greater. Your engine will put more torque to the wheels at the cost of top speed.
It's called "shorter" because your top speed is reduced and you reach redline faster - thus the gear feels "shorter" than it used to.
It's like shifting into a lower gear on a bicycle, you accelerate faster, but you have to shift up to go faster.

You can also do this by making your wheel/tires smaller. Say 13" with 195/50/13. That way you can have good torque for racing and go back to good mileage afterward.

[kommon_sense]

downside of going with a different final drive is that your shiftpoints will change. Also, in my y8 tranny, I can cruise at about 80mph around 3k rpm. If I were to change to a 4.7 final drive, then I would be cruising at 80mph around 4k+ rpm.

I don't know that changing the final drive is a good move on a daily driver. Get a lightweight flywheel and a light set of wheels instead.

[jdmspecdc5]

good accelleration but bad top end...unless you can rev high

[green_hornet_96]

downside of going with a different final drive is that your shiftpoints will change. Also, in my y8 tranny, I can cruise at about 80mph around 3k rpm. If I were to change to a 4.7 final drive, then I would be cruising at 80mph around 4k+ rpm.

I've never had my y8 tranny apart, why do I do 3700 rpm at 80 mph? I know, OT, but i had to ask.

[jwn7]

just found this forum, and this thread is exactly what i was looking for :D
i've been considering turbo until late last night, when i had a revelation.

http://www.f-body.org/gears
^^ a very very very useful link for everybody.

so....

with the ex tranny (4.25 final, 3.25,1.9,1.25,0.909,0.702) (fuel cutoff is at 6950 for a y8, but it only goes in 100s)

heres the shift points with the stock 185/65-14 tires:
6900 35 60 91 125 161

now with the 205/50-15:
6900 34 59 89 123 159 better...

now by trial and error, i figured out that those tires in effect changed my final to 4.31. still weak...

srr makes 4.7 and 4.9 finals for d series transmissions. www.exospeed.com

here's the shift points with the 4.7 & the 205/50-15:
6900 31 53 81 111 144

and with the 4.9 & 205/50-15:
6900 30 51 77 106 138
now that's pretty damn quick.

and furthermore... take that combination, and use the 1.346 3rd gear, and the 1.033 4th from a zc tranny, plus the 0.771 5th from a crx si and you'll have this:
6900 30 51 72 94 125 as compared to the stock:
6900 35 60 91 125 161 <- never even get there

as far as rpm drops: with the 4.9, 205/50-15, & hybrid tranny, vs stock.

2nd at 30: 4100. 3rd at 51: 4900, 4th at 72: 5300 5th at 94: 5200
2nd at 35: 4100, 3rd at 60: 4600, 4th at 91: 5000, 5th at 125: 5000

the drop is the same to 2nd because the gear is unchanged of course.

wow. just wow. i need to do this first.

in fact, it may eliminate my need for boost. i bet with some 0.5 overbore a6 pistons, crower stage 2 cam, upgraded valvetrain, pnp head, quaife lsd, hondata, and the usual bolt ons, i'd be putting up some very respectable times. well something along those lines, i haven't researched na parts at all; because i thought i'd never stay na d series, but now it seems like it might be a very practical option.

what do you guys think? :?:

[Toddnos]

true enough but......boost provides torque, which none of the above mention mods provide. You just making a quick rever instead of a horsepower machine........

[jwn7]

my car with less horsepower will be just as fast as your 'horsepower machine', because my more effective gearing will make my power more useful, and i won't drop out of the powerband as much. then just wait till i get more horsepower :D

and i don't know who told you that greater displacement, higher compression, a more agressive cam, more head flow, and bolt ons don't provide torque.

[Toddnos]

my car with less horsepower will be just as fast as your 'horsepower machine', because my more effective gearing will make my power more useful, and i won't drop out of the powerband as much. then just wait till i get more horsepower :D

and i don't know who told you that greater displacement, higher compression, a more agressive cam, more head flow, and bolt ons don't provide torque.werd on the cams/headflow stuff.....i meant the gearing upgrades. I would rather have a turbo, its a cheaper option.......

[jwn7]

yeah i'm kinda torn....

i budgeted $3000 for a custom turbo setup: t3 super 60, lovefab mani, hondata, ss oil lines, custom piping, custom 2.75 dp & exhaust, spearco ic, blitz bov, tial wg, 440 injectors, avc-r boost controller. boosting 8 psi, dyno tuned, daily driven - hopefully in the 180-200 whp range. that was the plan, but: i don't want reliability headaches, and autox with a turbo honda isn't very sensible. however, thats what the quaife lsd stitting on my desk, a jimfab traction bar, and the avc-r with gear dependent boost control would take care of.

now with this other setup: i'll be making less power (140-165) maybe (again, i don't know too much about na d). but, i won't need near as much.

compare those shift points again:
6900 30 51 72 94 125
6900 35 60 91 125 161

it just about gives me wood.

now with the upgraded valve train i could rev even higher; so the gears will be even closer!!! i'll be moving pretty damn quick i think, even with a moderate build that's not putting out too much hp.

if i could acheive the same results with an na setup, i'll take that over turbo any day. also, later on i could swap the pistons, sell the header and intake, and stick a big fat turbo on there and fucking rip.

my wood is getting bigger and bigger the more i think about this :lol:

[Toddnos]

still seems to fall out of vtec with those ratios right?

[jwn7]

yeah but the rpm drop is closer to 5500 in 3rd, 4th, and 5th; also, that's what a cam will compensate for. furthermore, with that 4.9 or 4.7 final, it will rip through the gears a little faster - a measly 200 rpm and i'm right back in vtec in 4th. plus the higher redline i'll get will keep me even closer - maybe even still in it in 4th gear. :twisted: :D

hell, maybe i'll be able to lower the xover point and actually gain from it when i get on the dyno, with a built engine.

:hyper: <- me ever since i thought of this last night.

but i have this shirking feeling that i'm missing something. i'd love to see a timeslip of a stock y8 tranny vs. this one.

[kommon_sense]

still seems to fall out of vtec with those ratios right?

I think that you will always fall out of vtec on the y8/z6 tranny *unless* you raise your rev-limit. If I shift at 7k, then I fall back to nearly 5k on the shift. If the redline were 8k, then I still fall back into a sweet spot on the powerband.

[kommon_sense]

yeah but the rpm drop is closer to 5500 in 3rd, 4th, and 5th; also, that's what a cam will compensate for. furthermore, with that 4.9 or 4.7 final, it will rip through the gears a little faster - a measly 200 rpm and i'm right back in vtec in 4th. plus the higher redline i'll get will keep me even closer - maybe even still in it in 4th gear. :twisted: :D

hell, maybe i'll be able to lower the xover point and actually gain from it when i get on the dyno, with a built engine.

:hyper: <- me ever since i thought of this last night.

but i have this shirking feeling that i'm missing something. i'd love to see a timeslip of a stock y8 tranny vs. this one.

I was doing a little math on the final drive earlier. I realized that with a 4.7 final drive, that the y8 would have nearly the same gearing as the b16a2 tranny. Only problem is that you are revving high when cruising at highway speeds.

[transzex]

slap on some 20" tires, cheapest gearing mod there is.

4.25 FD becomes a 4.82 FD on the small tires.

[kommon_sense]

downside of going with a different final drive is that your shiftpoints will change. Also, in my y8 tranny, I can cruise at about 80mph around 3k rpm. If I were to change to a 4.7 final drive, then I would be cruising at 80mph around 4k+ rpm.

I've never had my y8 tranny apart, why do I do 3700 rpm at 80 mph? I know, OT, but i had to ask.

what size tire you running? I'm running 195/55/15.

[sgvridgerunner]

In the long run the shorter gears will be more expensive for two reasons
1) - you will be sucking gas like crazy, and with rising gas prices, that's the last thing I would do.
2) - Since you will be cruising at higher rpms on the fwy, you will wear out your rings faster, leading to more frequent engine rebuilds.

With a turbo, you aren't always on boost, with short gearing you are always on high revs. You will be locked in.

I agree with the 20" tires. It's the cheapest, and pair that with your LSD, you will put down some wicked fast times for a near stock car.

Only if you are going full race (i.e: bye bye liscence plates) would I recommend the transmission.

[jwn7]

In the long run the shorter gears will be more expensive for two reasons
1) - you will be sucking gas like crazy, and with rising gas prices, that's the last thing I would do.
2) - Since you will be cruising at higher rpms on the fwy, you will wear out your rings faster, leading to more frequent engine rebuilds.
i used to own a car that got 12 mpg, so visiting a gas station every other day is nothing new to me. i think i can deal with a 5-10 reduction from the 31 mpg that i'm getting now. if that caluclator is right, i'll be crusing at 3900 rpm because i never go over 70 on the freeway - well not anymore. :wink: i can live with 3900 - hell i wouldn't even mind 4500 all day. i've been driving around in 3rd and 4th on the highway lately just to test the waters. i don't really mind.

and at 3900 i'm sure my rings will be shot after just a few days. :wink: chad drove 5 hours straight with a b16 tranny with 4.9 final on his b20vtec: 5500 rpm for 5 hours straight and no issues whatsoever - proof positive that honda engines can take it. my engine has near perfect compression all across, 1% on the leakdown test, and just feels very strong every day - it's a good one for sure. as long as i keep up on matience i'll be ok. worst case scenario: i build a motor. :)

With a turbo, you aren't always on boost, with short gearing you are always on high revs. You will be locked in.
that's not a very sound point: it's called upshifting :wink:. i can catch fifth going 25 and cruise at 1500 rpm if i want to. i'd say on average i'm going 30-40 so the tach will be somewhere between 1700-2400 most of the time if i stay in 5th. even in 4th it's still below 3000... the difference really isn't too bad. it's no cx tranny for sure though.

I agree with the 20" tires. It's the cheapest, and pair that with your LSD, you will put down some wicked fast times for a near stock car.
combine the tires, lsd, gearing, and the final = even more wicked times. :twisted:

Only if you are going full race (i.e: bye bye liscence plates) would I recommend the transmission.
point taken, and thanks for shedding a different light on the subject. but what's streetable to me may be very different than what's streetable for most people. i'll drive around in a gutted car with a ride that hurts your nuts everytime you hit a pebble in the road, an on off switch for a clutch, 6 lb flywheel, no radio, no ac, no ps, solid mounts, and want more. :twisted: if i want creature comforts i'll borrow my rommates cadalliac. :)

[Toddnos]

[quote=sgvridgerunner]Only if you are going full race (i.e: bye bye liscence plates) would I recommend the transmission.
point taken, and thanks for shedding a different light on the subject. but what's streetable to me may be very different than what's streetable for most people. i'll drive around in a gutted car with a ride that hurts your nuts everytime you hit a pebble in the road, an on off switch for a clutch, 6 lb flywheel, no radio, no ac, no ps, solid mounts, and want more. :twisted: if i want creature comforts i'll borrow my rommates cadalliac. :) thats what im sayin 8)

[mike6024]

It seems like I already have to shift really early in low gears in my daily grind. If this car is your day-to-day vehicle I wouldn't recommend it. It would drive me nuts. Maybe that's just me though. Also if you care about 0-60 times, you may have to start to shift to 3rd in order to reach 60 if you lower the ratios.

[transzex]

getting a clean shift into 3rd gets the best times!!!!!!!!!