SlowTeg

I would honestly think the best alternative to a nice cruising rpm would be a taller FD. Yes, this would hurt acceleration around town, but especially for those with mods (and more power) to make up for it, it wouldn't be very noticeable. Not to mention for those who are force fed, the taller gears would probably be an improvement. Especially for the F22 motors, I think slightly taller gearing in the cars wouldn't be that bad, as the added torque over the F20's should help considerably. I will say, it would be nice if 6th gear was shorter for highway cruising. I think the car could easily cruise a 500rpm lower in 6th gear, and be just fine (at least w/ my F22). It would make long highway drives much nicer.

Xzibit A

Those are all very good points, If the OP needs a trans then it might be worth it but its not worth buying a trans, then spending another 250 in parts, and then also the money for the rear diff. But for those with an AP2 all they have to do is spend about 250. if they are skilled enough to replace a clutch they can do this job.

Ive decided not to do this and instead just install the 3.63 gears after bumping up my power some.

rugsr

Ok thanks guys
Yea I have 27k on the car so I am in no need of a tranny
I was thinking Why not be able to take the 6th gear some where and have a taller one made in it's place
Sounds like it is not that easy

donaldmejr

the cheapest way (i would think) is to just add in a 3.9 gear in the diff. Also MY08 was at 4k @ 70MPH and after I upgraded my exhaust and intake it dropped to 3600 RPMs

Xzibit A

6th gear itself is part of the counter shaft, so you would have to have the a custom counter shaft and output shaft. which would be EXTREMELY expenive

rrounds

I'm sorry but your exhaust and intake did not change your rpm's at all @ 70MPH or any other speed.
That can only be done in the drive train(transmission, rear end gears or tire height.

ROD

BrazT

Actually, I installed an aftermarket Air-Freshener on my rear view mirror and noticed a 700rpm drop in cruising speed, along with a 5hp increase!

On topic: I would love to see someone actually attempt a change then gather some facts. Seems like an interesting mod but how long would it take for it to become cost effective though.

rrounds

That's because you had the top up and the windows closed. The fumes got you high and you were hallucinating.
If you have the money you can get a transmission with any gear ratio you want. I've seen 7 speed transmissions but they are way out of my price range($9500).

ROD

SlowTeg

I don't think anyone said they expect to cruise at <2.5k rpms, but lower would certainly be better. My old 98 civic would cruise at 3k rpm at 70mph. I think any taller than that is unnecessary and would certainly hamper performance. We all know honda loves short top gears in the performance oriented models (my old gsr had a cruising rpm of 3500rpm at 70mph, and the older Si's with the b16a's had a cruising rpm of 3750 at 70mph (and the Si's had a 1.6l)), but it'd be nice to have a lower cruising rpm in the s2k's. My '06 Ap2 at 3k rpm is at a piddly 55mph. At 70mph, we're talking ~3750rpm. That's way too high if you ask me. Yes, the s2k is hardly a "torque monster," but perfect for me would be 500rpm lower, so say 3250rpm at 70mph.

Keep in mind, I'm talking for Ap2 owners. The F22 clearly makes a decent amount more torque than a F20, so having a lower cruising rpm makes perfect sense. Personally, I think 3krpm at 70mph would even be fine for the s2k. Yes, it might not have quite the passing power with the taller top gear, but I don't recall my civic being that bad. Yes, the civic was lighter and fwd (less drivetrain loss), but it also only had a 1.6l. Yes, it changes the nature of the car a little, but again, I feel the s2k's gearing is plenty short. It seems like the best option would be a taller FD. Frankly, I don't know how the FI guys can stand all the shifting.. I think a taller FD would be on my short list for mods if I had boost.

Now, no one's saying this is "cost effective" by any means, because it's not. However, it would make long trips MUCH more pleasant as the engine wouldn't have to be spinning so high just to cruise at 80mph. More rpms = more wear.

davidc1

My 2c.

RPM's have a lot to do with mpg. All other factors being equal, running a 4k will burn twice as much fuel as 2k.

But, all other factors are not equal of course.

What XZibit A said above makes the most sense I think, but, I don't have anything to back it up.

As far as the money you'll save, let's see if this makes any sense, I'm just throwin some numbers in here....

Let's say you drove 10,000 freeway miles in 6th gear. (that's probably way, way, way more than most of us, but probably what I do). if you got 25mpg, then you'd use 400 gallons of gas. If you were to lower your rpms to some arbitrary number that now allowed you to get 35mpg, you'd use 286 gallons. That's a 116 gallon savings. If gas was $4 a gallon, thats a saving of $464 a year.

If all that makes sense above, it's a no brainer to make the change, assuming it could be done, and assuming you're gonna keep your car for a couple of years at least.

As far as lowering the drone of the exhaust, I know what you mean. I'd do it immediately just for that with my Skunk2, even with the silencers in!

As has already been pointed out, switching to an AP2 tranny won't help, as the 5th and 6th gear have the same equivalent ratio's as the AP1 because both the primary and secondary reduction shaft is different.

Now, if you could simple change the 6th gear set itself...the ratio of the AP1 6th gear is 0.810 and the AP2 is 0.763. Assuming my logic is correct, this is a reduction of 5.8%. So, for example, if you were running 4000rpm before, you'd drop to 3767rpm. Not enough for me for drone reduction, considering my highway speeds vary from 60-80.

Also, if we assume mpg is based only on rpm at constant rpms, which it isn't, this would result in an increase from 25mpg to 26.5mpg. Not enough....


Fun thinking though....