Gearing
Posted by ChrisKobi
ChrisKobi Chris Kobayashi Professional Moderator Location: Seattle, Wash. Join Date: 02/15/2012 Age: Possibly Wise Posts: 319 Rally Car: 2000 ford focus zx3 |
So while i understand how gearing is important I just don't understand fully what we want are cars geared at and why. I would like to have a better grasp on it, so if anyone has any good recommendations on a website or just flat out good knowledge perhaps with some graphics they would want to share with some of us that would be great!
Thanks, Chris |
john vanlandingham John Vanlandingham Senior Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
Gears are levers. A series of levers arranged so the continully mesh. The fulcrum is the point of cotact on the toofies. Big lever multiplies the force applied to it.. Motors are happy to spin what's known as "loadsa" rpm... We take that "loadsa' rpm and via gears in the box and final drive turn that into TORQUE to either overcome inertia like the lower gears or cruise along like the higher gears: 4th, 5th 6th. What we want in a rally car, no matter what the type is repeated HARD acceleration---sometimes know as "AX" from about 25 mph up to about 90mph and the ability to do a bit more MPH when needed 9because the pioneers made such straight roads. So we use "short' final drive and convert 5000-7000 into loadsa ft/lbs so the pokey low hp car goes quickly. This is a moot point nearly cause there is only alleged to be alternate gears and final drive that any normally sane person can afford.. See if you can lure Micheal Hoche-Mong who has a coupla Golves, one with a real box, ask him how it worked in Idaho last years.. John Vanlandingham Sleezattle, WA, USA Vive le Prole-le-ralliat www.rallyrace.net/jvab CALL +1 206 431-9696 Remember! Pacific Standard Time is 3 hours behind Eastern Standard Time. |
MarkHille Mark Hille Super Moderator Location: The hills of CT Join Date: 10/04/2011 Age: Midlife Crisis Posts: 135 Rally Car: I have two crap boxes |
http://www.teammfactory.com/gear-calculator
This was one of the best speed to rpm gear calculators I found because you can compair yours to another one. Tire size can make a bit of a difference. Where does your motor make usable power? Good gearing will allow you to keep the RPM where the motor can use it. Find the gear ratios and final drive that works and compair them to what you have or want. Subaru 6 speed for example, how does your speed per gear relate to one of those? My 1st-4th is really close...5th is another story. The closer the gears are to each other the faster you are going to accelerate and the higher the RPM will be (in the next gear) when you shift....but the more shifting your going to have to do. When you hit red line where does your speed put you in the next gears RPM? And what John said, gearing multiplies torque...and what is going to get you to 90mph the fastest? |
ChrisKobi Chris Kobayashi Professional Moderator Location: Seattle, Wash. Join Date: 02/15/2012 Age: Possibly Wise Posts: 319 Rally Car: 2000 ford focus zx3 |
ok so out of curiosity, is this what i'm looking for in my car? http://www.ebay.com/itm/Quaife-Ford-Focus-Escort-Mondeo-MTX75-Gearbox-5-Speed-Synchromesh-Gear-Kit-/120810139671?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item1c20d87017
Also not quite on the same topic but... LSD's,I was suggested a KAAZ http://www.kaazusa.com/lsd_ford.html but I also found these other 2 and was wondering what the differences my be if anyone knew. Quaife LSD http://www.sparktecmotorsports.com/qua-qdf20z.html?utm_source=googlepepla&utm_medium=adwords&id=20861070197&utm_content=pla Ford Torsen LSD http://fordracingparts123.com/driveline-parts/differentials/svt-focus-torsen-m-4204-svtf/?gclid=CJvGoJq7jrcCFclxQgodpTEALA HMMM I wonder if this thread is flagged by big brother for using LSD in it? By the way, thanks for all the help! Not gonna learn if I don't start asking questions! |
ChrisKobi Chris Kobayashi Professional Moderator Location: Seattle, Wash. Join Date: 02/15/2012 Age: Possibly Wise Posts: 319 Rally Car: 2000 ford focus zx3 |
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RALLYRS Mike Ball Godlike Moderator Location: Simi Valley,Ca. Join Date: 07/15/2011 Age: Ancient Posts: 466 Rally Car: Nope...I wish...RWD 2 Door Jeep XJ 4.0 5-spd Dirt-o-cross car(we have no grass!)2.3 ZX3 rallyx car(sold) |
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hoche Michel Hoche-Mong Infallible Moderator Location: Campbell, CA Join Date: 02/28/2006 Age: Possibly Wise Posts: 1,156 Rally Car: Golf, Golf, RX-3 |
Hi, wasn't paying attention or I would've responded sooner.
Yeah, I have two MkII Golves that're virtually identical except where they're completely different. One has a stock GTI transmission with a big final drive and the other has a special VW Motorsport gearbox, with all the gears spaced much closer together. It all comes down to the fact that the whizbanging fuel-suckin' noisemaker in the front of most vehicles makes its best torque in a relatively limited range of RPM. The reason for that has to do with the speed at which you can move air around inside it. You can do all sorts of things to change that - muck with the size of tubing, length of tubing, valve timing, dynamic compression ratios, blah blah blah, but even at best you can really only change it a little bit relative to the range at which it can run. For example, a stockish engine will idle happily at around 500rpm, but doesn't have any power there. At the same time, it'll be able to wind up all the way to its redline - say 7000rpm, before it falls on its face because it can't suck air in fast enough (or more likely, the rev-limiter cuts in to save it from grenading). Now if you put it on a dyno, you'll find that this hypothetical stock motor will start to develop its best torque at say, 3500rpm, and will pull pretty strongly up to 5500rpm, but after that it tapers off. So you've got about an 2000rpm ideal range at which that motor will accelerate quickly. You might dink around with the engine and move that band up or down - maybe 4000-6000 or higher, and may be able to broaden it by 500rpm or 1000rpm, but you're still relatively limited in how big that torqueband is. So the trick is to have some kind of device that you can use to keep the motor in that happy zone as much as possible, no matter what speed you're going. That's (obviously) the transmission. Now the question of "what's going to get you from 0 to 60 the quickest" comes into play. It's an important one, but it's not the whole story. If you're going to simply race down a dragstrip from christmas tree to timing lights, you can pick gear ratios that let you get up to into that torque range as quickly as possible (first), and then each gear after that can be selected to get the maximum use of that powerband so that you shift as few times as possible. For instance, in the case of an engine that develops optimum torque from 4K to 6K, you'd want to select gears so that every time you hit 6K and shift up, the next gear puts the engine right at 4K. The problem is that in rally, that's not the way we drive. You wind up through the gears on the start and then it's "brake, downshift, gas, hold it, gas gas, brake brake brake, down to second up to third back to second shit shit shit I need POWER NOW, ok whew, upshift upshift, brake, gas, brake, downshift, ..." A lot of times you don't have time to shift, or you can't do right on the optimal boundaries (4K and 6K in this hypothetical engine), or something comes up midcorner and you have to scrub off more speed than you anticipated, or yadda yadda. So you want a gearbox where the gears give you an overlap into that ideal torque range. So maybe you're moving along at a speed where third puts you at 5700rpm, and you know that if you upshift to fourth you'll be at 4300rpm. Now you've got the option to shift if you want to, and either way you'll still be in your optimum torque band. The drawback, of course, is that now you have to shift more over the total range of speeds, and this is where you go back and either build a motor that's got a broader torque band (and maybe get caught up looking into variable cam timing, or variable intake runners, or twin turbos, or other geewhiz stuff), or make compromises on how much that gear overlap is. Getting back to a stockish car and its gearbox, you have to consider what the manufacturers are building for. In most cases, the average driver doesn't want to have to rev the snot out of their engine and slip the clutch to get going at a stop light (and it plays hell with the clutch) so the manufs tend to put in a really low first gear. After that, they assume that people are going to want a medium amount of power around town, so they space 2nd, 3rd, and 4th moderately close. When people hit the highway, they mostly want good gas mileage, so the manufacturers put in a really high overdrive gear that lets people cruise to LA at low revs and get 30mpg. This is all really annoying when you're trying to race the thing. The (relatively) cheap'n'quick fix is to simply change the final drive ratio to something much bigger. This has the effect of "squishing" all the gear ratios together towards the slower end of your speeds. So say you put in a final drive that's 1.5x the size of the stock one. Now your fifth, which used to redline at 150mph is only good to 100mph. Your 4th, which went to 100, now bounces off the rev-limiter at 75mph. This goes all the way down to first, which used to go to 20mph and now only goes to 13mph, and is pretty much only useful for spinning the tires at launch. In my particular case, both of my cars have engines built that have about a 3000rpm-wide peak torque range. One of them has a stock GTI gearbox with a bigger final drive, so it's susceptible to the issue I mentioned in the previous paragraph. I almost never go down into first in that car and have to be thinking a bit about where I am in the RPM band when I shift because the relative gear ratios change from gear to gear. The other car has the groovy VW Motorsports gearbox with a taller first gear and all the gears spaced about the same distance apart - in that car it's a bitch to get it going in first but after that I don't have to think about it. Every gear is neatly spaced the same distance apart and they're close enough that I always have two gears that are possible candidates. It also translates into quicker stage times in a variety of more subtle ways - I don't have to being thinking about the gearing quite so much so I can spend more time concentrating on the line or listening to my codriver, I don't have to worry quite so much about gear-snatch destabilizing the car right when I need it to be predictable, I always have power on tap if I need it, etc. If I were rich or were driving a RWD car (cue JVL) or had one of them fancy gearboxes with a quickchange hatch in the case I'd change out final drives every event to match the roads, but I ain't and FWD gearboxes are generally bitch to deal with, so I just live with what I've got, which is pretty sweet all things considering. Self-righteous douche canoe Edited 1 time(s). Last edit at 05/11/2013 11:44PM by hoche. |
ChrisKobi Chris Kobayashi Professional Moderator Location: Seattle, Wash. Join Date: 02/15/2012 Age: Possibly Wise Posts: 319 Rally Car: 2000 ford focus zx3 |
Awesome that's some good info you guys! Ill read it again and again till it full sinks in my head. I am starting to get a better idea of how it all works and is beneficial. At this time I am just researching for what I need to do to the car in the future and after saving a lot. I do plan om putting an LSD in as soon as I can, maybe with the year as I have been told it would be of great benefit. It almost seems that while all that's taken apart I should put the close ratio gear set in. However, I need to figure out if the cost is worth the benefit at my newb skill level and if there is more important things to spend the money on.
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john vanlandingham John Vanlandingham Senior Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
Well final drive and diff at same time means you only take the box apart 2 times, once for diff and FD, the other time when you eventually have money for a gear kit.. In the meantime that final drive is going to wake the hell up the car..Look at the Corolla guys: lame ass little motor with not even 100 Beee Haitch Peas and ft/lbs but with a 5.35 final drive they've done good. Same with the too often ignored Garth with the Saab with such a low spec motor..but coupled with either 5.43 or 5.85, he drives that car quick (of course the weight of the car at maybe 1960 lbs helps) John Vanlandingham Sleezattle, WA, USA Vive le Prole-le-ralliat www.rallyrace.net/jvab CALL +1 206 431-9696 Remember! Pacific Standard Time is 3 hours behind Eastern Standard Time. |
ChrisKobi Chris Kobayashi Professional Moderator Location: Seattle, Wash. Join Date: 02/15/2012 Age: Possibly Wise Posts: 319 Rally Car: 2000 ford focus zx3 |
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john vanlandingham John Vanlandingham Senior Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
Well the motor in that thing doesn't make much of anything so I'd say go with shorter (bigger numbers) if you could, and then essentially skip first, use 2nd thru 5th..... Note that on the nicer cars that I like their motors make around 200 ftlbs of torque at modest rpm, so we dun't hafta gear them so short to get some good yank out of the car...,so a 4,3 or so is fine, a little short to compensate for the tall tires---which gear us UP 7-8% John Vanlandingham Sleezattle, WA, USA Vive le Prole-le-ralliat www.rallyrace.net/jvab CALL +1 206 431-9696 Remember! Pacific Standard Time is 3 hours behind Eastern Standard Time. |
JuggernautMotorsports Andrew Kulikowski Professional Moderator Location: Ontario, Canada Join Date: 03/31/2012 Age: Settling Down Posts: 25 Rally Car: 2000 Focus ZX3 |
I'll chime in. I currently race one of 2 Foci on our team. Take a look at our website (www.juggernautmotorsports.ca).
GET a KAAZ diff and have it set at 60% lock to preserve turn in. Its a proper plated diff. and does magic for the car. Unbelievable difference in performance. Literally the one thing I would keep if I had to strip everything else. Don't bother with the 'keep it at 100% lock so you can drive out of a stage if you pop a cv or axle' as you'll burn it out and need to rebuild it. As for gearing we run the MFactory 4.75 final drive set with the close ratio 3-5 gears; all synchromesh. Works decently for now. We started on the stock box then as we got faster did the final drive, folowed by the close ratio only last november. The next step is a dogbox but they're around $5000 and to tell you the truth when I get one (not soon) I will be slapping a sequential on it to reduce miss-shift related maintenance costs. The universal kit is around $2000. For you I'd grab a KAAZ and throw that in and spend all of everything else you have on new tires and getting to events to get as much seat time as possible. Upgrade only after you have lots of time in the car and feel that you need something. If you can't feel in the car as you race that 'hey I sure could use a little more torque to get up that hill' or 'I could use more power there' remember, if you're not pushing what you have to it's limit you won't do yourself much good to upgrade something you won't use fully. Plus with the way grassroots is I'd rather beat someone out and out in a spec class than beat them because I could drive 8/10 with a faster car and they had to drive 11/10 with a slower car. Your satisfaction may be different. This is of course assuming that you have a safely built, mechanically sound, well suspended car. |
john vanlandingham John Vanlandingham Senior Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
Well he has the struts, I arranged a loan of the car and maybe he's forgotten but he's supposed to bring a check.. Seems a lotta guys forget to bring checks for things... Hey Andrew (?--naughty naughty boy, that ain't your full name) weren't you supposed to be talking to me about stuff? John Vanlandingham Sleezattle, WA, USA Vive le Prole-le-ralliat www.rallyrace.net/jvab CALL +1 206 431-9696 Remember! Pacific Standard Time is 3 hours behind Eastern Standard Time. |
JuggernautMotorsports Andrew Kulikowski Professional Moderator Location: Ontario, Canada Join Date: 03/31/2012 Age: Settling Down Posts: 25 Rally Car: 2000 Focus ZX3 |
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ChrisKobi Chris Kobayashi Professional Moderator Location: Seattle, Wash. Join Date: 02/15/2012 Age: Possibly Wise Posts: 319 Rally Car: 2000 ford focus zx3 |
John, nope I have not forgot. Was just telling the girlfriend I needed her to write a check for you. (I don't have checks) I will mail it Monday as the mail man just came by. Or if you're going to be at the meet next weekend I can bring it to you then. Up to you.
Andrew, some good information. Every bit of it is good stuff especially since you're a foci driver also! I will look up your site when I'm at a PC and not on a phone. I'm pretty sure the diff is the next big thing after the suspension is done. Don't have much time to do anything big to the car before Nameless. Chris |
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