The art known as choosing ratios.

Right then its time to dig this up again.

What i want to know is what makes a good geared car for road use, i know its all personal choice and it depends on where the power is and so on.

So from what i can gather a race engine has a narrow power band so you dont want lots of rev drop, so would this be long/short geared, long/short final drive, all i know its close ratio'd.

Whats the effect of having short gears and a large final drive and vice versa, what's a better choice for N/A and boosted particulary turbo'd cars with lots of mid range torque.

Is it possible to achieve fast acceleration with high in gear speeds.

So to bring it something to work from here is a plot of my engine [assume its flywheel figures], where do i need to be looking to drop onto when i change up a gear? 4.5K

Black line is HP/Green is torque.
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For a road car, my preference is a close ratio 6 speed rather than leggy diesel gearing. Keep the stock 5th as 6th and move the rest closer together.

The Gemini gearset is a classic example of how good a close stack can be. In the VR6 02A application, the standard VW gap from 2nd to 3rd is awful, drops something like 1500rpm between changes and 1st is too tall. The Gemini gives ~ 500rpm drop through all of the gears, which is a substantial improvement for a road car, especially naturally aspirated. It makes the car feel half the weight and considerably more accelerative.
You can get the spacing closer with a short FD, but you'll be rowing the gearbox all day and have a schitt top end.

A cheap and good compromise is the standard VR6 box with a 3.64 G60 diff in it, which gives good acceleration in all the gears, inc 5th, without being too short.

If you want max acceleration, it's the way to go. If you want to hang onto the gears for longer and just lump around on the torque all day, then a diesel box is probably your best bet.

Have you looked into the 02M conversion? Nice gearing on that and very very strong. Being a 3 shaft gearbox, it spreads the load a lot better than the O2A/J and therefore less gear case flex.

I want max acceleration but i find that with the standard box now [G60] all it wants to do is spin in 1st and 2nd, now how do i keep the acceleration with more traction, im sure even with a diff in it will still spin, i dunno i want the best of both worlds.

How do drag cars get really fast acceleration, grip and high top speeds, and im not talking stupid high hp full on dragsters.

Slick tyres, anti-lag, launch control and a tall 1st gear

The G60's standard gears are well known to be a bit pants..... 1st and 2nd too short and 5th way too leggy. it's all over the place.

I think you will only find satisfaction in a full gearset like the Gemini or an O2M conversion.

Spinning in 1st and 2nd is inevitable with most gearboxes that have to deal with excessive torque, but you learn to drive around it and use those two as moving away gears only, and use the remaining 3 or 4 as you play time gears!

It's all about Compromise Mr Junkie

Yea i accept its about compromise thats why im trying to understand the whole effects different things will do, so how would a car with a long 1st then close ratio'd to 5th be like as that sounds like a good idea to me lol.

It is inevitable spinning in the lower gears currently but surely there must be a better compromise, as you say the standard ratios i have now are all over the place, there must be a way to get mental acceleration without spinning, my problem is i can turn the boost down to hold a solid 0.5bar but then its pants.

Ideally i just want to swap cogs about with no need to modify gearbox mountings, i have not broke the box yet or driveshafts so obviously im not running enough power haha.

With all the different boxes/cogs/final drives out there there has to be a good combination to create a suitable set of ratios to suit my engine.

But lets say when people post up the specs of the ratios of a box it means nothing, i cant look at it and think thats a good 1st gear or whatever, even looking at the quaiffe site as there is different gearsets/5-6gear etc also without taking into the equation different final drives, hence the thread title.

Suppose this is the same as alot of people as you always hear it but 3rd gear is just right in acceleration and traction, spins 3rd in the damp/wet conditions but hoping a diff will control that more.

So in an ideal world what would be a good gearset in numbers and final drive for good-mental acceleration without compromising too much traction and with a diff in to aid things.

kevhaywire wrote:It's all about Compromise Mr Junkie

Exactly! What are you prepared to compromise and how much money do you have, they are the first questions to ask!

Well for the right thing i will spend the money, i like the quaiffe idea of long 1st and close spaced, but i dont think i need 6 speed, quite happy with 5 also i like the synchromesh for ease of everyday driving which in my eyes defeats the point of getting the synchromesh 6 speed quaiffe.

I am willing to sacrifice top speed, [still want 140 -150], for acceleration but want bloody good traction without running R888's.

Is this possible?

OK my first post isn't that helpful, I guess your first problem is to find out what your engines actual wheel output is and take it from there you need to know how much torque you have at the wheels before you can start really getting a handle on gearing a car effectively IMHO.

It's difficult to pick ratios off the shelf and translate them into a theoretical ideal mate. All you can do is assess how the car behaves with the current gearing and make best guesses as to what would work better.

Have you played with Quaife's gear calculator? It's very good!

If you have excessive spin in the first 3 gears, then a diff and a good boost controller is probably a good start. Something like an AVCR where you can limit boost in the lower gears. Takes a lot of setup to get right but is effective. Sounds like pooping the party restricting boost, but less boost gives better traction which = better acceleration than wheel spin!

Obviously a bigger, laggier turbo will help aswell. Strong boost kicking in only when the car has good momentum is again more effective than a quick spooler breaking traction too early.

As I say, for me, a close stack box that drops the rpm right back into the peak torque zone with every shift is the way to go

No worries Chris, it made me think of things i had forgotten aout.

Well here it is in actual torque not NM but still flywheel i presume still, so at least its a ball park if you work on the presumed transmission losses.

RPM = lb/ft
2500 = 166
3000 = 258
3500 = 317
4000 = 332
4500 = 339
5000 = 317
5500 = 291
6000 = 258
6500 = 239

Looking at those numbers, 258 - 317lb between 3000 & 3500rpm is enough to break traction really easily. Hell even 166 @ 2500 is.

My missus's polo makes the same 166lb at the same rpm and that also spins the 1st 3 gears, despite having "traction control".

Which reminds me, that is another option...... check out Race Logic's TC system, which can be added to any car. It's damn good kit.

With that kind of torque, some form of boost control or decent TC system is going to be your best bet. Super long gearing will just frustrate you because if you make 1st and 2nd very tall, the rpm drop the 3rd will be huge if you want 3rd to be accelerative.

Take it to a rolling road and like awesome and get some comparative wheel figures. You describe the engines power as peaky but those figures look very drivable/unlaggy.

kevhaywire wrote:It's difficult to pick ratios off the shelf and translate them into a theoretical ideal mate. All you can do is assess how the car behaves with the current gearing and make best guesses as to what would work better.

1st 2nd too short, 3rd 4th spot on, 5th too long

Kevhaywire wrote:Have you played with Quaife's gear calculator? It's very good!

Tried before but its all meaningless to me.

kevhaywire wrote:If you have excessive spin in the first 3 gears, then a diff and a good boost controller is probably a good start. Something like an AVCR where you can limit boost in the lower gears. Takes a lot of setup to get right but is effective. Sounds like pooping the party restricting boost, but less boost gives better traction which = better acceleration than wheel spin!

Im happy with the boost control on the Haltech at the moment, simpe rotary electronic knob to adjust.

kevhaywire wrote:Obviously a bigger, laggier turbo will help aswell. Strong boost kicking in only when the car has good momentum is again more effective than a quick spooler breaking traction too early.

Well when i initially turbo'd the car i said to Jabba make sure its a big turbo, they put the largest VF series turbo on the VF22, it was back in the day when people were saying when you going "big" turbo on the 20v and referred to the IHI's which are obviously small turbos compared to say GT30's - GT35's. I never knew it was going to spool as quickly as it does.

kevhaywire wrote:As I say, for me, a close stack box that drops the rpm right back into the peak torque zone with every shift is the way to go

That sounds good to me but if i drop right onto the peak torque then surely my rev drop will be huge, like a 2k drop?

kevhaywire wrote:Looking at those numbers, 258 - 317lb between 3000 & 3500rpm is enough to break traction really easily. Hell even 166 @ 2500 is.

My missus's polo makes the same 166lb at the same rpm and that also spins the 1st 3 gears, despite having "traction control".

Which reminds me, that is another option...... check out Race Logic's TC system, which can be added to any car. It's damn good kit.

With that kind of torque, some form of boost control or decent TC system is going to be your best bet. Super long gearing will just frustrate you because if you make 1st and 2nd very tall, the rpm drop the 3rd will be huge if you want 3rd to be accelerative.

How will making 1st and 2nd longer make me have a huge drop in revs to 3rd, surely it would be the other way around, i also want to get as much mechanical grip/traction as i can before the need to add on electronic traction control so the car is doing more of the work instead of the party pooper trick.

ctwg60 wrote:Take it to a rolling road and like awesome and get some comparative wheel figures. You describe the engines power as peaky but those figures look very drivable/unlaggy.

I now agree with you that it is very driveable/unlaggy, when we were talking about it before the car was laggier due to the cracked exhaust housing causing more lag, now its fixed there is no lag if going up through the gears and not pottering around and i know thats the problem lol.

As Kev said, if i could have a bigger turbo i would but at this moment its not feasable.

I guess as Kev said you need to just try something either swap in a CTN or get a vr cog swap into your current box. I can't really make a judgement on how either choice will affect drivability without knowing accurate wheel figures. So.........

There is no magic solution, gearboxes are the compromise for the internal combustion engine. I think it is always going to be difficult to get the gearing right for a small capacity big power turbo car with FWD and not a lot of weight over the front wheels.