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

[Anonymous]

I'd been waiting a long time to try out the '2 again on the Circuit du Laquais (one of the great wee circuits we go to regularly as it's not too far from Geneva)...

If you're ever somewhere near Lyon in France, I would recommend a visit...
http://www.circuitdulaquais.com/


... and I'm totally amazed at the difference the new gear box has made... it's a real pleasure to have better acceleration (155-160 kph at end of straight instead of 145) and the right gear ratio in every situation. In fact I'm now able to go round the circuit with less gear changes than before as 3rd and 4th are now perfect.

Must say the new TRD WayDo struts and Sportivo springs also made a huge difference.

At first the car felt a little bit too "nervous", it was almost like discovering a new car: Turn-in is much more sudden and sensitive (tho' I did get the wheel alignment done), braking also feels more "involving" and the car now stays perfectly horizontal in all situations (unless you flip the car over in one of the sand banks -- something I try to avoid as much as possible   s:P s:P   )

I found that setting the front struts to "medium" (2 or 3) and the rear on "hardest" (4) produced the best results (in dry hot conditions anyway)

Really happy with my lap times (3s less than last April) eventhough my tires were getting a real beating on the overheated tarmac. (My best times were almost always the first 2-3 laps of each series.)

Another member of the French MR2 club joined us in the afternoon. Took him on board for a few laps and he's been completely converted. He's now searching for either a C56 gearbox or a 6sp C60 Celica gear box to fit to his '2... I think he's probably also going to uprate his suspension   s:wink: :wink: s:wink:

[Anonymous]

Yeah, but your 0-60 times rubbish   s:twisted: :twisted: s:twisted:  

(Only joking)

BTW That track looks amazing, I've been round silverstone south circuit but thats it.  I'd really like to get into track days, but with only one car, way too scared i'd trash it (which i most definitly would).

[Anonymous]

Yeah, but your 0-60 times rubbish   s:twisted: :twisted: s:twisted:  

I'm crap at 0-60 anyways (hate that fried clutch smell! I prefer the smell of burning rubber   s:twisted: :twisted: s:twisted:  )

BTW That track looks amazing, I've been round silverstone south circuit but thats it.

I'd love to try one of the "classic" circuits. I think in the UK you're spoilt for choice! I don't know how long that circuit will stay open --you won't believe the problems they have with some of the locals, the "green talibans" and the government -- they are all out to ban track days altogether there and in France in general...   s:roll: :roll: s:roll:  

I'd really like to get into track days, but with only one car, way too scared i'd trash it (which i most definitly would).

I know the feeling and that's why we generally stick to the "better organised" events that tend to be safer (than some anarchic, overcrowded events) ... at the end of the day, you have to be able to drive home with the same car...

[Anonymous]

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...

Table bashing?   s:P s:P    (only joking!)

Seriously, there's nothing wrong with the figures... unless Tirerack data is totally rubbish (i would have to go and measure the wheel manually in that case...)

Based on Yoko and Bridgestone S03 tire specs (from tirerack): where average betwen front and rear wheel is 910 revs per mile (1609m): that gives us 1.768m for one wheel revolution.

6500 rpm = 108.3 rps (revolutions per second)

If the wheel was directly attached to the engine, at 6500 rpm we would have 108.3 x 1.768m = 191.5 m/s (a swift 689km/h, or 428mph... but lets get real here, it's a 1.8l 103 kW engine   s:wink: :wink: s:wink: )

So here comes the gear and differential (final) ratios: basically the ratios in our gear box reduce the rate of rotation, so for example at 6500 rpm in 5th gear (ration 0.815 and Euro diff ratio of 3.941) 0.815 x 3.941 = 3.212

Use this to divide the engine (input shaft) rpm and you get output rpm at the wheels.

In our example, 6500 rpm at a 1:1 ratio would be 689 km/h or 428mph. With the combined 5th gear and diff ratio (divide by 3.212) we get 214.5 km/h and 133.3mph.

In order to reach 150 mph (using standard size wheels and the Euro transaxle) the engine would need to run at 7300 rpm.

If the rev limiter is set at 6800 rpm, if you reach it in 5th you will be doing 206.4 km/h 128mph (J/US Spec) and  225.8 km/h 140mph (Euro spec).

[Tem]

Based on Yoko and Bridgestone S03 tire specs (from tirerack): where average betwen front and rear wheel is 910 revs per mile (1609m): that gives us 1.768m for one wheel revolution.

Average between front and rear?  s:o s:o

You lost me there...what average? And why do you need to consider the front wheels at all? You're doing the same mph at same rpm in same gear every time, even if your front wheels would be locked or in the air...

[Anonymous]

Based on Yoko and Bridgestone S03 tire specs (from tirerack): where average betwen front and rear wheel is 910 revs per mile (1609m): that gives us 1.768m for one wheel revolution.

Average between front and rear?  s:o s:o

You lost me there...what average? And why do you need to consider the front wheels at all? You're doing the same mph at same rpm in same gear every time, even if your front wheels would be locked or in the air...

OK this part was a bit confusing   s:) s:)  . I shouldn't have bothered including it as its impact on the speed figures is less than 2% anyway (well within speedometer error margins). But here's the explanation anyway   s:wink: :wink: s:wink:  

Front tyre is slightly smaller (in circ.) than rear and about the same size as the stock rear Yokos. Taking the average was a way of getting a figure for a partly worn S03.

Interesting though how the data in the table can be so "shocking"   s:shock: :shock: s:shock:   I don't get it   s:? :? s:?  

  s:) s:)

[mph]

I've done the numbers this morning, slightly differently to you, but come to broadly the same conclusion - something isn't adding up.  (see below)

I know my speedo is accurate at 100mph (rolling road) and that GPS also concurs at that speed.

Another approach is this: I reckon that 5th/3000rpm is 66mph - something that can be checked on the road (anyone please verify?). Given gears are linear, this would indicate 143mph is at 6500rpm and 150mph is at 6820rpm. While I admit this doesn't tie in with what I recall the rev counter saying, I certainly do remember 150mph on the GPS (digital display); further, 6820rpm is at least possible. Re-doing the numbers would mean this equates to a combined gearing of 3.12:1. Still doesn't add up, but is a little closer...

Thoughts?

205/50R15
=> wheel = 381mm
=> sidewall = 102.5mm
=> circumference = 1841mm

6500rpm = 108.3rps
150mph = 67.056m/s
67.056/1.841 = 36.42 wheel rps

Combined drive ratio required = 2.97:1

Stated drive ratio from original post = 3.514:1

[Tem]

Here's what I get...

205/50/15 -> circumference of 1.841m
1000rpm at engine is ~1227rpm after 5th gear and ~313rpm after final drive. That's ~577m/min, which is ~34kmh@1000rpm.

So that's ~242kmh@7000rpm, which is ~150mph.


Of course that's VERY dependant on the tyre circumference, which in reality isn't just that. You should measure your tyres to get the real data.

[Anonymous]

You appear to have a turbo fitted in your '2. Perhaps the gear box has been changed/modified ?

The speedo on any car is often set to indicate 5-10% more "speed" than reality. (This is usually quite cool as it sometimes avoids getting speeding tickets   s:P s:P  )

I use GPS receivers a lot (especially for sailing, etc.). The only thing I can think of that could provide an explanation for an "inaccurate" 150mph reading (if it was inaccurate) is a high GPS DOP (dilution of precision) this can produce "jerks" in speed measurements (and they often show up as an exagerated max. speed -- on boats anyway)

It's a mystery... (twilight zone music)   s:lol: :lol: s:lol:

[Anonymous]

Here's what I get...
205/50/15 -> circumference of 1.841m

Tem, have you got tractor wheels fitted to your car or what?  s:lol: :lol: s:lol:  

Here's are the official specifications for the S03 tires:

http://www.bridgestonetire.com/dpp/sizespecs.asp?passproductid=227

On the 7th row (205/50/15) you find 560 RPK (revolutions per km) (= 902 RPM)...

So: 1000m/560 = 1.7857m

For the (bigger) yoko A043s: we have 1000m/558=1.792m

So once again, I restate that the data in the table is correct    s:roll: :roll: s:roll:    (sorry)

Furthermore, with a stock 1ZZ engine and a Euro gearbox you will not get anywhere near the rev limiter in 5th gear (unless pulled along by a GT3, or going down a steep hill or something   s:wink: :wink: s:wink:  ) Even if you could, at 6800 rpm you are still "only" doing around 226 km/h (140mph). However, I am sure that your speedo will be indicating much more (240km/h or 150mph) would be perfectly reasonable.

If you add a turbo, I am also sure you *will* be able to go all the way up to the redline even with the longer euro gear box. If you tweaked the engine ECU to push back the rev limiter (to say 7000rpm) you would reach maybe 145 mph (over 150 mph on the speedo)...

But anyway, what are we talking about?   s:? :? s:?   Where would you drive at 150 mph? And even if you could, what's the point, you could't hear your car stereo anymore!   s:lol: :lol: s:lol:

[Tem]

Tem, have you got tractor wheels fitted to your car or what?  s:lol: :lol: s:lol:  

That's the stock wheel size  s;) s;)  But like I said:
"Of course that's VERY dependant on the tyre circumference, which in reality isn't just that. You should measure your tyres to get the real data."

Furthermore, with a stock 1ZZ engine and a Euro gearbox you will not get anywhere near the rev limiter in 5th gear

I know and I'm not saying I could, just saying I think your table is wrong  s;) s;)  My limiter is at 7600rpm anyway  s;) s;)

you could't hear your car stereo anymore!   s:lol: :lol: s:lol:

I hope not, cause mine's in the garage  s:lol: :lol: s:lol:

[Tem]

Here are the reference numbers and approx. prices:
Final ratio: 33402-12041 $93.51
3rd ratio:   33034-12130 $80.24
4th ratio:   33035-20170 $80.25

Does this mean that two new gears are only $160?  s:shock: :shock: s:shock:  

(seems I might have to open my gearbox, so might as well see if I can get those in)

[kanujunkie]

and a lot of money to fit em Tem  s:? :? s:?   good luck though, unless you feel capable of doing this yourself and have a press

[Tem]

and a lot of money to fit em Tem  s:? :? s:?   good luck though, unless you feel capable of doing this yourself and have a press

Yeah, I was thinking of trying it myself. I do have a press.

[kanujunkie]

and a lot of money to fit em Tem  s:? :? s:?   good luck though, unless you feel capable of doing this yourself and have a press

Yeah, I was thinking of trying it myself. I do have a press.

lucky bastard  s:wink: :wink: s:wink:  

you must have a nice workshop then

[Tem]

lucky b*****d  s:wink: :wink: s:wink:  

you must have a nice workshop then

It's really nothing special  s:lol: :lol: s:lol:

12ton press is only like 100 euros anyway...it's pretty much just a large hydraulic bottle jack with some steel around it.

[aaronjb]

12ton press is only like 100 euros anyway...it's pretty much just a large hydraulic bottle jack with some steel around it.

I think we need to start importing more stuff from Finland  s;) s;)  The cheapest (10ton bench press) is over twice that price in this country..

[Tem]

12ton press is only like 100 euros anyway...it's pretty much just a large hydraulic bottle jack with some steel around it.

I think we need to start importing more stuff from Finland  s;) s;)  The cheapest (10ton bench press) is over twice that price in this country..

  s:shock: :shock: s:shock:  

Then again, mine's more basic...doesn't have fancy lines like that  s:lol: :lol: s:lol:

It's not this one, but looks similar:
 m http://www.biltema.fi/osteri/osteri.cgi ... yhmaid=143 m

[Tem]

Here are the reference numbers and approx. prices:
Final ratio: 33402-12041 $93.51
3rd ratio:   33034-12130 $80.24
4th ratio:   33035-20170 $80.25

Where did you get these prices...? Local Toyota quotes over $200 for each  s:? :? s:?