View Full Version : Gear Ratio ?'s
fodive
08-02-2002, 05:30 PM
im not sur ehow to ask this, but ive always wondered what diffrences gear ratios make in a car, i always see car magazines refering to final drive ratios of cars, and i was wondering what kind of effects these have on the cars, thanks
The larger the gear ratio the greater the acceleration but you sacrifice top speed <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/mad.gif" border="0" valign="absmiddle" alt=':angry:'> nismoparts.com has a set for the s13 and s14 take a look under RING & PINION SETS i think the s13 comes with 4.083 final gear ratio stock you could move to the 4.364 or 4.636 for around $457 but i don't know how much of an improvment they are in the 0-60 and 1/4 mile <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/hmmm.gif" border="0" valign="absmiddle" alt=':hmmm:'>
fodive
08-03-2002, 01:24 AM
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Dark @ Aug. 02 2002,8:09)</td></tr><tr><td id="QUOTE">The larger the gear ratio the greater the acceleration but you sacrifice top speed <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/mad.gif" border="0" valign="absmiddle" alt=':angry:'> nismoparts.com has a set for the s13 and s14 take a look under RING & PINION SETS i think the s13 comes with 4.083 final gear ratio stock you could move to the 4.364 or 4.636 for around $457 but i don't know how much of an improvment they are in the 0-60 and 1/4 mile <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/hmmm.gif" border="0" valign="absmiddle" alt=':hmmm:'></td></tr></table><span id='postcolor'>
i thought the shorter the gear ratios the greater accel, and hte wider the ratios the higher top speed.... either you or gran turismo 3 is lying to me <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/sad.gif" border="0" valign="absmiddle" alt=':('>
SR20Fastback
08-03-2002, 01:35 AM
Go Gran Turismo!!! I think its the bigger the number the quicker the gearing. ie 1st gear is like 3.34, and 5th gear will be.589 (not real gear ratios for any car probably)
fodive
08-03-2002, 01:47 AM
alrite...but then what is a final drive ratio? what is its purpose?
SR20Fastback
08-03-2002, 01:56 AM
I got the impression final drive is the overall gearing... I guess like on GT3 where you can adjust the overall gearing. You know what I mean?
fodive
08-03-2002, 01:59 AM
yeah i know....i love that game...i wonder how many posts we can go back and forth uninterupted before someone comes in here and says that we're both wrong....
so is final drive jsut the average of the 5 or 6 gear ratios then?
SR20Fastback
08-03-2002, 02:06 AM
Hmm Im not sure, SprunScorp and I got like 30 one time <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'> I guess it could be something like an average. damn transmissions and the confusing things about them. We should talk about things that I can understand, like pizza, or boobs
fodive
08-03-2002, 02:20 AM
boobs are fun....and girls dont poop
we can make this a hot topic all by our selves...
too bad in the moring someone will bitch slap us in the face fo rpost whoring Xtremo...but oh well, if you guys do....JUST AWNSER MY QEUSTION!!!!!!!!!!!!!!
transmissions are scary...i wish life was like gran turismo...
PabloHoney
08-03-2002, 02:27 AM
Final drive is the final gear ratio that the tranmission has, not one of the actual gear ratios (like 5th or 6th). In a RWD it's in the rear end, in a FWD it's in the transmission. The purpose is to be able to change the overall ratio of the tranmission with one gear (the final drive gear) rather than having to change each and every gear to lengthen your gears. A larger, or taller, final drive gear will give you better acceleration sacrificing top speed, and vice versa.
fodive
08-03-2002, 02:39 AM
it all makes sense, but how can the final drive gear change the set ups of the other gears?
well, you've got gears in your tranny connecting your engine to the drive shaft and then gears in your differential connecting your drive shaft to actually put the spinning to the wheels. So you change the gear ratio between I believe the drive shaft and the differential. Then It will change the characteristics for all gears, instead of having to go in your tranny and actually change every gear. And yes, the higher the # the quicker the accyl and lower the top speed. Just think of what it actually means. Say our imaginary car has ratios of 1:3 in 1st, 1:1 in 3rd, 1:0.5 in 5th, with a final drive ratio of 1:2. These are definately off for a regular car but ya know...easy math.
1:3 1st gear, every time your crankshaft spins once, your driveshaft spins 3 times and your wheels spin 6 times.
1:1 ratio in 3rd gear....every time your crankshaft spins once, your driveshaft spins once and your wheels spin twice.
1:0.5 in 5th gear, every time your crankshaft spins once, your driveshaft spins 1/2 a rotation and your wheels spin once.
I'm not 100% sure this is correct, but it is how I understand it as of now...I agree though, tranny's are scary :)
SR20Fastback
08-03-2002, 03:07 AM
Haha so I was right about the #'s. I remember someone talking about the differential being the final drive not too long ago. I totally forgot about that, doh!
pornallstar
08-03-2002, 03:33 AM
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (DSC @ Aug. 03 2002,03:54)</td></tr><tr><td id="QUOTE">well, you've got gears in your tranny connecting your engine to the drive shaft and then gears in your differential connecting your drive shaft to actually put the spinning to the wheels. So you change the gear ratio between I believe the drive shaft and the differential. Then It will change the characteristics for all gears, instead of having to go in your tranny and actually change every gear. And yes, the higher the # the quicker the accyl and lower the top speed. Just think of what it actually means. Say our imaginary car has ratios of 1:3 in 1st, 1:1 in 3rd, 1<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wow.gif" border="0" valign="absmiddle" alt=':0'>.5 in 5th, with a final drive ratio of 1:2. These are definately off for a regular car but ya know...easy math.
1:3 1st gear, every time your crankshaft spins once, your driveshaft spins 3 times and your wheels spin 6 times.
1:1 ratio in 3rd gear....every time your crankshaft spins once, your driveshaft spins once and your wheels spin twice.
1<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wow.gif" border="0" valign="absmiddle" alt=':0'>.5 in 5th gear, every time your crankshaft spins once, your driveshaft spins 1/2 a rotation and your wheels spin once.
I'm not 100% sure this is correct, but it is how I understand it as of now...I agree though, tranny's are scary <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'></td></tr></table><span id='postcolor'>
Yes that is correct DCS, You get a cookie. Good Job! I almost had to whip out my old high school auto book to get some quotes. LOL.
There is an easy what to think about the ratios on a tranny. Think of them on your old 10 speed bike. 1st gear you had to pedal real fast and yet you weren't going all that fast. Once you got to the 10th gear you didnt have to pump those lil chicken legs of yours as much to maintain that nice fast cruising speed. Hope that kinda makes since to all of you.
now that we know how the do hicky works <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> How about some 0-60 <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> 1/4 mile <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> and Top speed loss estimates <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/mad.gif" border="0" valign="absmiddle" alt=':angry:'> anyone? <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'>
pornallstar
08-03-2002, 03:59 AM
Well your top speed can be limited to 3 things.
1. Computer, just get a new chip.
2. Aerodynamic, AKA "A wall of Air" this can be overcomed by being more Aerodynamicly sound and adding more horse power to overcome that "Wall"
3. Gear limited. well you could change the gearing on the car but who has the money for that.
Most people that are trying to get a land speed record in a car will run into Problem #1 or #2.
To be continued................
(im very tired and need to sleep its 5 AM)
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Dark @ Aug. 02 2002,06:50)</td></tr><tr><td id="QUOTE">now that we know how the do hicky works <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> How about some 0-60 <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> 1/4 mile <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> and Top speed loss estimates <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/mad.gif" border="0" valign="absmiddle" alt=':angry:'> anyone? <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'></td></tr></table><span id='postcolor'>
Webpage (http://www.geocities.com/MotorCity/7080/TIP094.html) <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/thumbs-up.gif" border="0" valign="absmiddle" alt=':thumbsup:'>
Too many numbers my brain can't take anymore aaaaaah <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=':p'>
Thank you DSC that article was a great contibution but since i hate math i found this Gear ratio program (http://www.240sx.org/links/programs/gear.zip) It's a zip file you need Excel to run it but you don't need a calculator and it does all the work for you <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'>
drift freaq
08-04-2002, 11:50 AM
its nice to see people grasping this concept quickly . Good job DSC very well explained . Now if we really want to spin these guys heads lets start talking final drive ratios in relation to boost with Turbo's and keeping the car in optimum boost for the longest possible amount of time in each gear. Seems to me I went around quite a bit with this in the chat room a few months back . hahahahha <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=':p'>
fodive
08-05-2002, 12:57 AM
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (drift freaq @ Aug. 04 2002,12:50)</td></tr><tr><td id="QUOTE">its nice to see people grasping this concept quickly . Good job DSC very well explained . Now if we really want to spin these guys heads lets start talking final drive ratios in relation to boost with Turbo's and keeping the car in optimum boost for the longest possible amount of time in each gear. Seems to me I went around quite a bit with this in the chat room a few months back . hahahahha <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=':p'></td></tr></table><span id='postcolor'>
bring it on...i want to know as much as i can about everything i can
uiuc240
08-05-2002, 09:28 AM
well, turbos take time to build boost...and they build boost better in higher gears. for instance, 11 psi is tough to see in 1st for me, but in 4th it's no problem. if you numerically lower the final drive, it effectively lengthens each gear ratio by the same factor. so, you can stay in each gear longer before running out of revs. the trick is to not gear it TOO high, or you'll go slower because the engine might not have enough torque. this whole idea is how cars like ferraris and lamborghinis and mclarens can go like 50+ in 1st and 200+ in 6th. they have enough oomph to push through those amazingly long ratios. i think the 300ZX TT rear end would be about perfect in a tuned SR (3.73:1 vs. 4.08:1) but it's hard to fit back there. So you're probably better off with the J30 LSD with it's 3.92:1 gears or a nice set of NISMO gears in whatever ratio you want <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'> $$$
Eric
fodive
08-05-2002, 07:45 PM
so for a turbo setup, you'd want to spend minimal time in 1st and 2nd gear right...but wouldnt you also want to set your car up so its staying in boos throughout the gears, i.e above 4k RPM?
uiuc240
08-06-2002, 09:07 AM
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (fodive @ Aug. 05 2002,8:45)</td></tr><tr><td id="QUOTE">so for a turbo setup, you'd want to spend minimal time in 1st and 2nd gear right...but wouldnt you also want to set your car up so its staying in boos throughout the gears, i.e above 4k RPM?</td></tr></table><span id='postcolor'>
not really. i'm saying that by having too short of a 1st and 2nd, it's hard to really give the turbo time to spool. you spend more time spinning tires and shifting gears than simply keeping your foot to the floor. make sense?
Eric
drift freaq
08-07-2002, 10:59 AM
give Eric the star. For understanding boost pyshics 101 congrats eric. Ok now that Eric has made the point , not only has he made it well but he is right on the money as for the gear ratio in a properly tuned SR20DET powered car. In fact in Japan S14 and S15 SR's came with 3.70 gears. I still do not have concrete data on the 180sx but I am assuming it was the same story. I am also not sure about red top Silvia's.
Though I do know CA18DET powered cars had different gears around the range of ours due to the smaller engine size and lower HP output. HP output plays a role in the gearing to.
the more HP you have the lower numerical gears you can run and get away with it(which is actually termed has tall gears because it gives you more top end wereas 4.08 would be considered lower gears because it gives you acceleration in the bottom end). Hence V8 cars usually coming with gears in the low 3's say 3.18 to 3.46 some even had 2.9 gears. I know he might have said this more or less but I want it to be clear car companies also gear their cars according to the HP . Which is why you see HOnda's running 4.2:1 gears. Small engines not a lot a Of HP per see unless its a type R engine or a Japanese Honda engine.
Dave
uiuc240
08-07-2002, 11:13 AM
thanks for the gold star, dave! <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=';)'>
something else to mention is this:
some of you may be wondering, why change the final drive ratio so much? why not just change 1st and 2nd or something and make them a little taller? well, the answer is cost. they can use the same tranny in multiple cars, and simply change the final drive (aka "rear end") and get a whole new range of gears. this helps to keep the gear spacing roughly the same, too. you don't want a tall 1st and 2nd, but then 3rd is only good to 85 or something. change the final drive and you spread them all out.
i can't think of ANYTHING more to add about gear ratios. except that i would love to have the money for a 3.73 R200 LSD. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>
Eric
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