Gear Ratios - Gearing Experts Needed

[Tr0uble]

S15 6 spd transmission w/ S15 Differential Gear Ratio = 3.692

Transmission ID FS6R92A1st - 3.6262nd - 2.2003rd - 1.5414th - 1.2135th - 1.0006th - 0.767Reverse 3.4371.8 Liter Oil capacity

Anyone know the formula to calculate gear ratios?

S15 6spd transmission w/ 240sx Differential Gear Ratio = 4.083

1st - ?2nd - ?3rd - ?4th - ?5th - ?6th - ?

I'm not too keen on gearing or rear end swapping and I never got my hands on the S15 Diff.Wanted to know what the difference would have been if I had the3.692 rear end as opposed to the 4.083 I currently have.Does bigger number = "shorter" gear?

Also does anyone know offhand the stock tire size of the S15 Silvia?xxx/xx/Rxx?

[jdm_master_X]

i forgot the equation, ill have to look in my notebook.

you have to remember this key thing about gear ratios. i think of it as the "skyline tails picture" allow me to demonstrate:



as you see in this picture, the circles resemble the rear of a R34 GT-R and some fuel cell gizmo. this way, i remember that taller gear ratios mean high torque, low speed. direct drive will always be even speed and torque, and a shorter ratio allows for much more speed but sacrifices torque. pretty much, ratios exploit the engines rotation in relation to the gears in the transmission and differential and ultimately the wheels.

ugh, my bad. i was just blabbing. i realize how confusing my explaination was. but the above facts are TRUE!

[Tr0uble]

Does photobucket just not work for me only? or does everyone have problems viewing/logging in to photobucket?

So according to your explanation above, I should accelerate faster with 4.083 differential? or accelerate faster with 3.692?

In 6th gear with 4.083 Rear End @ 3200 RPMs I'm rolling at 80MPH

[niceguy]

The shorter (numerically higher) the final, the faster you should accelerate (vs a taller final and all else the same)...of course, all else equal, at a given speed, you'll be at a higher rpm which can cause less mpg and droning (depending on exhaust),etc....

Ex: With a 3.69 FD at 80mph, you may be around 3k rpm but with a 4.08 (and same gearing) you may be around 3500rpm...

[jdm_master_X]

another example is the difference between using a 3.9 FD from a J30 vs a 4.36 FD from an R32.

with the J30 @ 80 MPH, I was around 3K-3.2. The OEM diff will place me at 3.4-3.5K, and the R32 diff placed me at 3.7-3.8K @ 80 MPH. Obviously this also depends on the wheel + tire size.

[Tr0uble]

So I guess that's why my acceleration feels insanely fast.Putting a 4.083 FD with a transmission that usually has a 3.692 FDThe 1 piece aluminum DS from Shaftmasters probably contributes to the bigger pull I guess.

Anyone have any recommendations on brand for lightweight flywheel for an S15 SR20DET w/ 6spd transmission?

[Fla240sx]

see if fidanza makes one, I always liked their idea of having a changeable area where the clutch rides.....

[Tr0uble]

see if fidanza makes one, I always liked their idea of having a changeable area where the clutch rides.....

Will do, already had them in mind. Though I like to have a couple to compare specs.

Anyone else have a different brand in their car they'd like to recommend?

[jdm_master_X]

OS Giken Flywheel. Obviously it comes with their multiplate clutch, but the flywheel is insanely light. It's pretty much comparable to an automatic flexplate. This clutch kit is installed in my friends car and I drove it. For a relatively stock car, this thing is super rev happy with that flywheel on.

the JUN flywheel is good too.

[Tr0uble]

OS Giken Flywheel. Obviously it comes with their multiplate clutch, but the flywheel is insanely light. It's pretty much comparable to an automatic flexplate. This clutch kit is installed in my friends car and I drove it. For a relatively stock car, this thing is super rev happy with that flywheel on.

the JUN flywheel is good too.

How did the clutch engagement feel with the OS Giken multiplate?

I'm also looking into some aluminum output shafts. Anyone tried these on their car with an aluminum driveshaft, underdrive pulley, and flywheel?

If I decide to go all out race I may just switch to all carbon fiber from the shaft all the way back to wheels. I dunno yet, decisions decisions.

[jdm_master_X]

How did the clutch engagement feel with the OS Giken multiplate?

I'm also looking into some aluminum output shafts. Anyone tried these on their car with an aluminum driveshaft, underdrive pulley, and flywheel?

If I decide to go all out race I may just switch to all carbon fiber from the shaft all the way back to wheels. I dunno yet, decisions decisions.

the clutch engagement is obviously stiff but grabs super hard. i would imagine the clutch could engage under hard launches. the pedal engagement is at half travel when you depress it, but there are so many factors that come into play like my friends pedal freeplay, etc.

output shafts/axles? I believe there is a member here who used MazWorks axles but they broke. He was running a drag setup, so I guess there are also factors to consider, such as what the vehicle is primarilly used for.

aluminum should be more cost effective and vehicle efficient compared to carbon fiber unless this car is a serious serious drag car. what a daily driver does well on the street, does sub-par on the track, and a dedicated track car obviously drives like $h!t on the street.

find the medium.

[Tr0uble]

Good Advice

[Steinkrunk]

I was bored, so i decided to actually calculate the gear ratios for youif your using the same diameter tires, the ratios should be as following1st: 4.0102nd: 2.4323rd: 1.7044th: 1.3415th: 1.1066th: 0.848reverse: 3.800

i dunno if this still helps you, but i'd thought i'd try to help a fellow member out.

[Tr0uble]

Thanks, I appreciate that. Now I see why my car accelerates like it does.