Newbie Question on gear ratios

[Drftn280zxt]

I been reading around, and searching and have found that many different differential gear ratios are were available in R200. My question is, is it better to have a low gear ratio, or high gear ratio for drifting/roadracing. What would be a good ratio. To put it simply I read all those number and have no idea what they mean. Please fill me in, I feal dumb not knowing the meaning of gear ratios,but better late than never.

 

The only thing I got out of my reading is that a low/low gear ratio is excellent for drag racing, unless my memory is failing me, quite possible.

[Leith280zlt1]

A 3.5 gear ratio means that for every 3.5 turns the driveshaft makes, the tires make one. If you have a taller gear ratio, say a 4.11, you will have more low end/takeoff power. The downside is you won't go as fast or get as good of gas mileage typically. With a taller ratio, you take off faster. With a lower gear ratio, you go faster but don't take off as fast. For drifting, I would imagine you would want the taller gear ratio because it would be easier to get the tires to break loose. Hope that helps.

[boodlefoof]

Just to clarify, I think Leith is referring to higher and lower numerical values for gear ratios in his post. The terminology does get confusing.

 

A lower gear ratio has a higher number. E.g., 4.11 gears are actually fairly low ratio even though they have a higher number. A lower gear doesn't always equal better accelleration though... you want to match your gear to the powerband of your engine. You can "over gear."

 

A higher gear ratio has a lower number.

 

I actually usually heard the term "tall" refer to higher gear ratios (lower number). Also commonly referred to as "highway gears."

 

I really wouldn't know what would be best for drifting.

[Thumper]

It depends on if you plan to run a n/a engine or a turbo engine. Turbo you will want a 3.545 and n/a 3.9 or 4.11 This is for short track work, no big straight aways.

[frank280zx]

id say for a turbo for roadracing you want a 3.3 but that is just me

[Drftn280zxt]

drag racing is much of concern, don't need top end speed. I need torque. I do plan on going twin turbo someday. But I am planning on getting the LSD next summer (Leith )just trying to figure out waht gears to use. From what I've read my 82 280ZX Turbo should have 3.54 gears, correct? I would think that low end torque would be very desirable it get the rear tires loose. And if I can eventually do the 17x12 in the rear, I think so good low end torque is going to be necessary to break the rear loose. And since at low rpm, there isn't any boost yet, whatever can help in the torque domain would seem very appropriate. So maybe 3.9 or 4.11. I don't know, please give me more input and suggestions.

 

Thanks for the help so far. Its starting to make more sense.

[Drftn280zxt]

bump! Okay I'm getting mixed responses here. Half of you are saying go with 4.11 gears. And then the other half is saying if your going turbo have 3.3-3.5 gears. I do not have intentions of building a drag racing machine, so I would expect that a high gear ratio like 3.3 would not be desirable for road racing, autoX, or drifting. Low end torque is very important because those tires gotta stay loose. In the low end (no boost) turboed cars don't have a whole lot of torque (at least my Z doesn't seem to) so I would think that the taller gears would be benificial, and then at higher rpm when the diff is not supplying the torqey advantage the turbos are spooled and accomodate for lack. So would 3.9-4.11 gears be more desirable? I want to make sure I have leith put together the right setup when the time comes. From my uderstanding and research my Z has a 3.545 open diff.

[zguitar71]

A 3.54 in your car is not really higher overall than a 3.9 in a N/A car. Your 1st gear ratio is 3.5 and a diff of 3.54 = 12.39 overall 1st gear ratio. The N/A trans 1st is 3.06 with a 3.9 diff = 11.93 overall ratio. So the turbo's overall ratio is actually lower than a N/A ZX. I would drive the car like it is (in a race that is) and see if you are staying in the power band or not. You could go to a higher gear diff and mabey stay in 1st on an autox race or you might find going to a 3.7 or 3.9 is better and then stay more in second gear. Remember that racing tires are usually smaller in diameter than the street tires you use so that alone can be like using a different diff. If you do end up running large diameter tires then you will probably need to go to a lower diff.

 

If you are staying below your power band too much then you need lower gearing is you are running up by the red line too much (running out of room) then you need higher gearing. Typically cars that run very low diffs also rev very high too. The gearing that works with your car probably will not work well after you have built the engine up a bunch. You need to figure out the set up of your car and then gear it to suit, until then it is hard to say what way you should go.

[zredbaron]

I run a 4.37 with a Quaife for autox, and I estimate I have just under 250 rwhp (NA). I have dragged my car as well, and I find that I kick *** off the line, and lack acelleration in 4th and 5th gears (and I need all 5 for the 1/4). Too high a number/too low a gear for drag.

 

I autocross my Z, and this ratio is a considerable advantage, my accelleration is tremendous under 60 mph, and my wheels breakway when I don't want them to if I'm not careful. My Quaiffe saves my a$$ all the time.

 

You keep mentioning 'drifting.' With my setup, a very challenging setup to drive, I drift all the time, but not intentionally. If you drift through a turn, you are not carrying as much control (and therefore speed) through the turn. You DO NOT want to drift. Go to nationals and you will see how many of the pros drift. Zero.

 

It IS fun as hell, though.

 

Cars such as a stock 350Z (with r-compound tires) can hold full pedal without breaking away the tires, which can actually be an advantage. Proper throttling is now a skill that driver does not have to master, and can put faster times down with a quicker learning curve.

 

My ratio makes my first gear almost useless. I can't floor it, and I can't use it for more than ~ half a second. Any more and my wheels break loose, and I don't accellerate as well. I can't floor second above 4000 rpms, and I can't ever floor second if I'm not in a straightaway. Too much gas and I drift and lose speed trying to recover and not take out a wall.

 

If you don't make much power, then a low ration will help you. If you do, it will force you to learn how to use it. I advise you take all this into consideration when making your final decisions. Your differential can make or break you in autocrossing and road racing.

 

Personally, I like having a car that is difficult to drive. Trying to tame the beast is what makes it so fun for me.

 

Fun doesn't necessarily correspond to being the most competitive.

[Guest 81na ZX]

For a dedicated autoX car, you want basically to top out(redline) in 2nd at 70-75mph.

Why? Cause if your reaching over 75mph on an autoX, your local region is taking on alot of risks Most autoX's for stock/SP/ST/SM cars get around 60mph on a long course. As we all know, adding an extra shift is bad on a straight right before a corner

 

Theres a bunch of calculators out there that'll find that out for you. I've got some at home, maybe I'll remember to look tonight...

[Drftn280zxt]

with knowing all of that, and taking into consideration what I plan to do engine ways, a 3.9 might not be bad, more offline acceleration (more break away power) without sacrificing to much top end. Oh yeah my intention are not to drift while autoXing. I plan to drift at drifting events, ie Drift Day or the like. I think that a 2way and 3.9 gears ought to do it. If I got 4.11 of lower, I have to much torque, and I'll just be spinning in high rpm. If I stick with what I've got I can't gurantee I'll be satisfied with the torque response later. I think I've got a solid decision, but any opinions are welcome, I'll take all the guidance I can get, all it takes is one person with different input.