Euro spec gear ratios - did we get a bum deal?

[Anonymous]

IMHO the original gear box (C56) final drive is fine. (Any shorter and you *will* need a 6th gear   s:P s:P  ) The Euro box's final drive clearly is too long: it's obvious for example when going up a steep hill in 2nd and you often have to drop into 1st.

Changing just the final drive ratio on a C52 (Euro) will improve performance but not solve the other major problem: the drop in rpm from 2nd to 3rd is massive compared to the original gearbox ratio. No matter how short your final ratio is, the drop will have the same magnitude. Anyone who's driven the '2 hard will know about this long "gap".

From a purely practical viewpoint, I think it's much easier to change the whole gearbox. Changing the final ratio means changing the crown (around the differential) AND the output shaft... (this is no quick job).

Incidently I spoke to a Toyota mechanic who has over 30 years of racing experience, he told me that the "ultra-long 3rd" on sports cars is a "European tradition" designed solely for better fuel economy, but it's a real pain in the arse.

[GSB]

Interesting stuff... Whats the score with the newer 6 speed boxes?

Also, am I correct in thinking that the US/J-spec box wont let the car get up to 60mph in second, so requireing an extra change in a 0-60 sprint? Obviously in Europe the 0-60 is an important marketing tool, but in the US they seem to prefer standing 1/4 mile times as an indicator of performance.

[Anonymous]

0-60mph: 7.9s (Euro), 7.1s or 7.3s depending on year (J/US).

That's still a big difference, even with the extra gear change.

Anyway, 0-60 (or 0-100 km/h) are a bit naf... a 1/4m (or 400m) is a better measure of performance.

IMO the best way to test is to take the car on a good (twisty) track and time your laps   s:wink: :wink: s:wink:

[Anonymous]

The new 6 speed gearbox has the same ratios as the 5 speed, but with an added 6th gear (see Tem's link to page on Spyderchat.com, on the previous page of this thread    s:wink: :wink: s:wink:  ).

Looking at all these tables it would appear that the US/J-spec gearbox won't do 60 in second gear, unlike the Euro spec one. Hmm, I understand that in driving terms a close ratio gear box is better at maintaining appropriate engines revs for maximum performance / better acceleration, but won't this extra gear change cancel out any advantage in acceleration for a straight 0-60 time?   s:? :? s:?

edit: posted the above at the same time as Phat!

I would be dubious about those 0-60 times - the gearing may not be the only factors affecting these times (driver, conditions, etc...). A fare comparison would be between two cars fitted with the different gearboxes with the same driver, on the same day, same, track, etc, to try and make it a fare test.

[Tem]

0-60mph: 7.9s (Euro), 7.1s or 7.3s depending on year (J/US).

Where did those 7.1s and 7.3s came from?  s:shock: :shock: s:shock:  

AFAIK, the official Toyota quote for 0-60mph is 7.9s in US as well. And a 2000 model brochure from Japan quotes 7.9s for 0-100kmh.

[Anonymous]

From Toyota's press release:

"Capable of 0-60 mph performance in slightly over seven seconds"

Actually 0-60 mph was generally quoted as 7.1s for the  '00 and '01 models. Some car magazines managed even better times as low as 6.9s. (This is often the case as at least three car magazines in Europe managed to get better times than the official Toyota figures: Evo, TopGear and a Auto Revue.)

Later models became heavier and slightly slower 7.3s (the 2004 model is the worse with a whole load of extra fat member braces).

http://spyderchat.com/comparisons.htm#miata

The only improvement (with time) was for the '03 SMT model (the gear shifting is as good as for the manual version.)

[Anonymous]

I would be dubious about those 0-60 times - the gearing may not be the only factors affecting these times (driver, conditions, etc...). A fare comparison would be between two cars fitted with the different gearboxes with the same driver, on the same day, same, track, etc, to try and make it a fare test.

But comparing the same car/driver/track is what I'm doing in a much better context than just doing 0 to 60 trials. (Personally, I hate doing these 0 to something trials, almost as much as my clutch hates them...  s:wink: :wink: s:wink:  ) Anyone used to driving a Euro '2 who tries one with the C56 gear box will be amazed at the difference. (And not just for acceleration timing.)

The figures I quoted are the standard Toyota data.

For info: with the new gear box, I have knocked approx. 0.7s off my 0 to 100 km/h and 1s for the 1/4m. (Did it on the same stretch of road, however not exactly same mass or air density.)

[Tem]

http://spyderchat.com/comparisons.htm#miata

"Data courtesy of Road and Track"

Looks like that time was measured by R&T magazine...?


Like you said, we all know that it's faster than the quotes  s;) s;)

[Anonymous]

Also, am I correct in thinking that the US/J-spec box wont let the car get up to 60mph in second, so requireing an extra change in a 0-60 sprint?

im sure my j-spec '2 hits the limiter in 2nd gear at 58-59mph, its definately not on the 60 mark anyway. so surely that would mean j-spec have a slower 0-60 time than euro because of the extra chage up.

in 5th gear, every 500rpm equals 10mph e.g:

1500 = 30
2000 = 40
2500 = 50
3000 = 60
4000 = 80

and so on, which would make it a few mph out on that chart thats just been put up. put my speedo is probly out by a few mph anyway

[Anonymous]

im sure my j-spec '2 hits the limiter in 2nd gear at 58-59mph, its definately not on the 60 mark anyway. so surely that would mean j-spec have a slower 0-60 time than euro because of the extra chage up.

That's just what I was thinking!

Phat; I'm not disputing that there is an improvement with the C56 gearbox with in-gear driving, but I just don't see how there could possibly be any flat out acceleration advantage with the C56 over the C52, as you have to change gear sooner/more often to achieve a certain speed (i.e. 60 mph); let alone beat it by 0.7 second plus!   s:shock: :shock: s:shock:  

Measuring a performance change by feel may not be very accurate; my mates Peugeot 406 TD feels quicker to 60 than my Rover, because of the characteristics of a TD car, but it is infact it's 2 seconds slower.

Sorry this isn't a dig, I just don't understand how it could be that much quicker...  s:? :? s:?    s:) s:)

[Anonymous]

No problem. These concepts are sometimes not that easy to grasp. In fact I know quite a few mechanics who still don't understand the difference between torque and power, even less the importance of having the right gear ratios...   s:? :? s:?  

OK, I'm going to try and illustrate the "practical" way...

If you put your car straight into 2nd gear (or 3rd) and accelerate from standstill up to 60 mph -- you wouldn't even have to change gears. But do you really think you will get a better 0-60 time?...    s:? :? s:?  
I don't think so (unless you have a magical engine)  s:wink: :wink: s:wink:  

One of the first things you do when you "prepare" a race (or rally) car for a track or event is to adjust the gear ratios to adjust the amount of  acceleration and top end speed (it's often a compromise). (In fact there are many other subtleties...)

Changing gears takes a definite amount of time (in fact it's approximately 0.4s). But if your acceleration is higher and most importantly, if the next ratio keeps your engine rotating in your maximum POWER (not torque) zone, you will maximise acceleration. This explains how I have demolished my 0-60 and 1/4 mile times (as I had expected!)

However you are right about the time lost on gear change. In fact I can reach about 57 mph in under 6.7 seconds! If the engine were a 2ZZ and could rotate over 6800 rpm, the time would be very good because I wouldn't have had to shift up.

But 0-60 times are silly anyway (unless you're a rice boy   s:wink: :wink: s:wink:  ). What matters here is to have a gear box that's capable of getting the most out of your engine and converting it into maximum torque at the wheels.   s:P s:P  

This graph illustrates pretty well the difference between both gear boxes. (I used the Quaife GB calculator) Quife builds close ratio sequential gear boxes for racing (if anyone is interested)   s:wink: :wink: s:wink:  

[Anonymous]

Beyond the technology, there's also a "human" issue here:

Most MR2 drivers couldn't care less about the gear ratios on their car. They are happy cruising with it and are not necessarily looking for the maximum performance.

Many bought the '2 because it's a true sportscar (lightweight, agile, powerful, etc.) I'm part of this group.

When I first tried the car I had just sold my 300bhp+ cup tuned 911 Carrera (0-60 in just over 5s) However, I immediately fell in love with the way the '2 handled, it's a brilliant and care free car to drive.

I did a few track days and drove it often hard around great mountain roads etc. I had noticed the wierd gear ratios, but it wasn't until I discovered about the original gearbox (J- and US-spec) that I got pretty pissed off. Because it wasn't a case of something being improved (subsequently) it was the case of a perfectly tuned gear box being replaced in Europe by a badly tuned one...

Of course I could have lived with the Euro box. But $750 got me a brand new C56 in the US. The performance gains are massive and I cannot wait to take it to the "Circuit du Laquais" this Saturday   s:twisted: :twisted: s:twisted:

[Anonymous]

One of the first things you do when you "prepare" a race (or rally) car for a track or event is to adjust the gear ratios to adjust the amount of  acceleration and top end speed (it's often a compromise). (In fact there are many other subtleties...)

Thanks for the explanation - I do appreciate what the differences in gearing mean; It just seemed that these figures were a little "optimistic", compared to the change in gearing and needing to change up sooner - however the calculations prove otherwise! As you mentioned before, I wonder why Toyota put the C52 on the Euro spec Roadster (different ratios on 3rd, 4th, 5th and final drive)? Maybe as above they felt it would either better suit our european driving style (?) - a longer 3rd gear as you said.

But 0-60 times are silly anyway (unless you're a rice boy   s:wink: :wink: s:wink:  ). What matters here is to have a gear box that's capable of getting the most out of your engine and converting it into maximum torque at the wheels.   s:P s:P  

Exactly! Most acceleration is not done from a standing start, so really the most useful gears are probably 2nd, 3rd and 4th and the relationship between them - i.e. closer ratio's being best.   s8) s8)  

How much did your C56 box cost / where did you get it from? (EDIT; well you've answered that one now!) Did you do anything else while the box was off - up-rate the clutch / put on a lightened fly wheel? These may be worth doing (particularly the latter) while you got access to them.

Does anyone have any experience of a lightened flywheel on the Roadster, btw?

(Sorry slight thread hijack!)  s:) s:)

[Anonymous]

How much did your C56 box cost / where did you get it from? (EDIT; well you've answered that one now!) Did you do anything else while the box was off - up-rate the clutch / put on a lightened fly wheel? These may be worth doing (particularly the latter) while you got access to them.

Does anyone have any experience of a lightened flywheel on the Roadster, btw?

(Sorry slight thread hijack!)  s:) s:)

I was really tempted by the lightweight flywheel, but wanted to keep costs within reason. I did the gear box swap myself (with the help of the Big Green Book) and asked a friend who has a Toyota garage to help me with the LSD swap. So total cost was about $750 + $200 (shipping from US) + $200 (tools, materials, "pocket money" for the mechanic   s:wink: :wink: s:wink:  , etc.)

Arnaud (a.k.a. Dieamond) a french MR2 enthusiast has also bought a C56 gearbox in the US. He's going to get it shipped over next month and I believe he's going to buy and fit the lightweight flywheel (instead of swapping the LSD)... He wrote a good article on the difference between the gear boxes

[Anonymous]

I was really tempted by the lightweight flywheel, but wanted to keep costs within reason. I did the gear box swap myself (with the help of the Big Green Book) and asked a friend who has a Toyota garage to help me with the LSD swap. So total cost was about $750 + $200 (shipping from US) + $200 (tools, materials, "pocket money" for the mechanic   s:wink: :wink: s:wink:  , etc.)

Arnaud (a.k.a. Dieamond) a french MR2 enthusiast has also bought a C56 gearbox in the US. He's going to get it shipped over next month and I believe he's going to buy and fit the lightweight flywheel (instead of swapping the LSD)... He wrote a good article on the difference between the gear boxes

Interesting - I'll keep an eye out for any news of what it's like!   s8) s8)

[Anonymous]

i beleive sam has a light weight flywheel...

[mph]

I've compiled a simple table comparing top gear speeds for both transaxles (i.e. 5th gear):

http://www.hanneken.net/MR2/ratios.html

There's something definitely wrong with those numbers. I have a standard UK spec car along with stock wheels/tyres. ~6500rpm in 5th gets you just over 150mph according to GPS (and off the scale of the speedo). I didn't fancy taking it to the rev limiter.

Does anyone have any experience of a lightened flywheel on the Roadster, btw?

Yes. Yum!

[Tem]

There's something definitely wrong with those numbers.

Didn't look at it earlier, but you're right, the speeds in that table are too low...

[SteveJ]

[ I have a standard UK spec car along with stock wheels/tyres. ~6500rpm in 5th gets you just over 150mph according to GPS (and off the scale of the speedo). I didn't fancy taking it to the rev limiter.

Aside from the little matter of a turbo that is  s;) s;)

Having seen you dissapear along the autobahn and then seeing the look on your face when we caught up with you, I dont think I would want to find out what speed you can ultimately achieve with the stock ratios either  s:? :? s:?

[mph]

Does anyone have any experience of a lightened flywheel on the Roadster, btw?

Ok, to qualify my post a little - there's a lot of labour of getting to the clutch/flywheel. If you're there already and can exclude the labour costs, then it's you're only paying for the material cost of the flywheel - I'd highly recommend it. The stock FW is very heavy (8-9Kg IIRC); my particular one is half the weight. I'll let some clever boffin (GSB?) tell you how much angular inertia saving that equates to, but it's a lot. Between the turbo and the SMT, I can't tell you want acceleration performance you'll get, but if I inverse the increased amount of engine drag I now feel, it's probably quite a lot. The SMT loves the flywheel and blipping the throttle is 'almost' bike-like in performance. I'd look forward to test driving a manual!

[Anonymous]

how much was your fly wheel mph?

[mph]

I think I've prevously talked about it in detail - have a look   s:wink: :wink: s:wink:  

I purchased here - primarily coz I needed a clutch pronto and there wasn't a lot of choice (and Paul had helped me out before..)  m http://www.ppeengineering.com/PPEindex.htm m

[GSB]

I'll let some clever boffin (GSB?) tell you how much angular inertia saving that equates to, but it's a lot.

Thaks for the vote of confidence! But with out knowing the exact dimensions and distribution of the materail the flywheel is made of, its hard to come up with exact figures... However, the removal of even a small amount of mass from a flywheel can have a big impact, so with 50% of the wieght removed, the engine speed must accelerate very-very quickly...  s:shock: :shock: s:shock: .

The upsides of fitting one are well known; power thats not being used to accelerate a bloody great lump of iron on the end of the engine can be used instead for accelerating the car. You're not increasing the engines power, but making better use of the power its got...

The downsides of a lightened flywheel are that you may be able to feel some of the harmonic vibrations that the stock flywheel would otherwise dampen out (i.e. you may perceive the engine to be running a little "rougher" when in fact its just transmitting vibrations that were always there, but were previously dampened out - If a poorly designed flywheel were to be fitted, there is a chance that these vibrations can cause damage to other parts of the engine. I seem to recall VW engines were susceptible to this, and were cured by fitting a heavier pulley at the front end of the crankshaft.) , Also, due to the reduced mass, theres lots more engine braking. Thats not so bad in theory, but it does mean that if you're a driver of only middling ability, or have a particularly leaden throttle foot, The sudden change in engine power with small throttle movements could very easily catch you out... Say mid bend, a lift off the throttle, and due to greatly enhanced engine braking charachteristics the back end of the car suddenly wants to be in front where all the action is... Owners of very sensitive right feet need only apply!

As for the maths, frankly I cant be bothered as its not easy stuff! But if you really want to go that deeply into it, heres a quote from a Nissan site...  s:wink: :wink: s:wink:  

Inertia is the property of matter resisting a change in motion. The flywheel resists a change in the speed of rotation of the driveshaft, consuming power during acceleration. A flywheel has mass and inertia.  It takes torque, the rotational equivalent of force, to start and stop its turning. The rotational equivalent of mass is the moment of inertia. The more mass an object is, the harder it is to get it to start or stop moving. Moment of inertia depends on the mass of an object and where it is concentrated close to the axis of rotation. Think of the flywheel as a disc. This oversimplifies the properties of a flywheel since a flywheel is not a homogenous mass but thicker in the center than the edges. However, it will make calculations easier to understand and still offers a good estimate. The formula for the moment of inertia, I, is: I=0.5mr^2. Holding r constant since the size of the flywheel is not changing you'll notice mass has a large effect on the moment of inertia. Substitute rotational equivalents for straight-line motion variables in Newton's second law of rotation to determine the amount of force exerted on an object. Use torque for force, moment of inertia for mass, and angular acceleration for acceleration.



If moment of moment of inertia (mass) decreases, less torque is needed to keep the acceleration variable the same. If the same torque is applied, the angular acceleration increases. Now that you've gotten the Physics 101 lecture, let's take this to a more advanced level course. Let's apply this to the 1993 Sentra which weighs about 2,500 pounds and makes about 140 horsepower at 6400 rpm in 3rd gear. Using 3rd gear and final drive ratios, the 3rd gear wheel rpm is 1192 (6400 rpm x 1.286 3rd gear ratio x 4.176 final gear ratio). Calculating for 3rd gear torque and assuming a stock tire radius of 175mm (0.574 feet), this gives a forward rate of acceleration of 0.43 g, or about 13.8 ft/sec^2. Angular acceleration, or how fast the rate of rotation of the flywheel is changing, is 24.1 rad/sec^2 (linear acceleration/tire radius). Multiplying this by 3rd gear ratio and by the final drive ratio, the flywheel is accelerating at 129.4 rads/sec^2. The stock flywheel weighs 18 pounds and is about 0.365 feet in radius, giving a moment of inertia of 0.0434. Flywheel torque is the flywheel angular acceleration times the moment of inertia, or 4.8 ft/lbs and the power consumed by the flywheel is torque times angular velocity, or 5.86 hp. Changing the flywheel weight to a 9 pound lightened flywheel from Unorthodox Racing while holding all other variables constant, the flywheel only consumes 3 hp, freeing up 3 hp in 3rd gear. A lightened flywheel frees up more power in the lower gears since it is harder to begin momentum that to continue it. Solving for 1st and 2nd gears, the lightened flywheel frees up 16 hp in 1st and 6 hp in 2nd. Gains in the higher gears are negligible, 1.7 hp in 4th and 1 hp in 5th.

A car with a heavier stock flywheel will obviously benefit more from a lightened one. The Spec V flywheel weighs in at almost 29 pounds, a heavyweight in the Nissan lineup. Switching to the 12 pound Jim Wolf Technologies flywheel will free up 16 hp in 2nd, 7 hp in 3rd, 4 hp in 4th, 2.5 hp in 5th, and 2 hp in 6th. Amazing, the stock QR flywheel consumes 50 hp more than the lightenend one in 1st gear! It revs happier and has more pickup than a Playboy bunny at a Wall Street bar during happy hour! This engine is already a torque monster so invest in sticky tires to make the most traction of that power.

Since a flywheel absorbs some of the energy generated by the engine during acceleration, lightening the flywheel increases the torque on the driveshaft since less energy is used to accelerate it and more is used to turn the drivewheels. Keep in mind it's not just how much mass is removed from the flywheel but where it is removed. The concentration of mass affects how much resistance the flywheel offers to changing rpm. Rotational inertia increases with the square of the distance of the axis or rotation. Removing weight on the edge of the flywheel is 4 times as good as from the midpoint between the center and the edge. Finally, a flywheel will not show much of a gain in horsepower on a dyno because it doesn't increase fuel or air and can't increase horsepower. Remember, you're not actually improving your car's power, just how quickly it can get to that power. An inertial dyno will show gains by the engine reaching a predetermined rpm sooner with a lightened flywheel.

[aaronjb]

I purchased here - primarily coz I needed a clutch pronto and there wasn't a lot of choice (and Paul had helped me out before..)  m http://www.ppeengineering.com/PPEindex.htm m

Assuming you got the RPS, Martin, all I can say is - excellent choice, sir  s;) s;)

I have one on t'other car, and quite apart from being an absolute work of art (really, they are..), they're ridiculously light through the main body being billet aluminium - only the contact plates are steel, which are removable and replaceable. Indeed, you can rebuild the whole flywheel to accept a carbon/carbon clutch setup  s:) s:)  (Though that would be overkill on a '2  s:) s:) )

[Tem]

FWIW, TRD quotes this for their flywheel:
"Weight: 4,500g (-38%) Moment of inertia: -55%"