Is 200 Final Drive Ratio

[ScifiPaul]

Hello Team, as a new IS 200 owner (one week and counting) I noticed that the car seemed very smooth for the indicated speed so I cabled up my GPS and checked it out. With the speedo indicating 80 mph the GPS read 72 mph. This was repeated for several steady state speeds. It looks like the speedo is 10% optimistic. I would like a second opinion so I have tried to find the final drive ratio for a 2001 IS 200 SE Auto but my searches have come up blank - I even searched the forums !

Does anyone out there have access to a workshop manual or incredible amounts of knowledge and could they find me the data please ? (final drive ratio in mph per 1000 rpm )

Thanks,

ScifiPaul

[Mr Morse]

Speedo -vs- Gps 10% high is about right. At least it gives the driver the benefit of the doubt! :D

Welcome to the club! :D

[Dave-Ellen]

think its 21 mph per 1000 rpm in 6th

[ScifiPaul]

Thanks Mike, my old Prelude felt so different - just a but lower to the ground - but a choice of 3 on the speed front would put my mind at rest as I sail past the speed cameras.

ScifiPaul

[Kazi]

It has to be optimistic, lets face it, its no flying machine!

[jasestu]

Can't you just tailgate a mate who's driving at a known speed and check that way?

[SpOcK]

Do you still have the original size tires (215/45-17)? If you have smaller diameter wheels, the car/speedo thinks it's going faster than it is...

Speedos are usually optimistic "by nature", cause are allowed to show more than you are doing, but NOT less.

I've changed the tyre size to 225/35-19 and as it has a slightly (15mm) bigger diameter than the original size, my speedo now shows _exactly_ correct speed. I've checked this against my gps.

[SpOcK]

think its 21 mph per 1000 rpm in 6th

←

ScifiPaul has an Auto, so he doesn't have a "6th"...

[ScifiPaul]

Thanks to all the members for your input;

yes, tailgating a mate up the M4 is a possibility but I was trying to avoid the attentions of the law in the first place - still I will resort to this if I can't work out a preed from the gear ratio.

Well spotted spOck, I think that the Auto final drive ratio must be higher than the manual - I get just under 3000 rpm at an indicated 80 mph (which is about 70 GPS mph) and would equate to about 65 in a manual ?

Cheers,

ScifiPaul

[RX-Men-8]

See here mate, 4th post.

Cheers,

RX-Men-8

[ScifiPaul]

Perfect !! thanks RX-Men-8. I had tried searching - honest, but must not have tried hard enough. Now, where's that calculator ?

Cheers,

ScifiPaul :)

[ScifiPaul]

Thanks to the help of all the members I now have my answer;

The IS200 Auto has an overdrive top gear (0.73:1 plus diff of 4.1:1) giving 334.1 wheel revolutions per 1000 engine revs in top (4th)

Standard 215/45R17 tyres have a circumpherence of 77.3"

(checkout; www.powerdog.com/tiresize.cgi)

Final answer; 24.4 mph per 1000 rpm in top

My GPS is right, 3000 rpm = 73mph ! (and the speedo reads 80 mph)

Now what happens if I pump up my tyres a bit ?

Cheers,

ScifiPaul

[lexus boy]

think most cars do this

just how they are

[New Bhoy]

I Have notice the same with my IS300 auto sportcross

Speedo have a faster reading than my road angel, between 8 and 10%.

Was a bit puzzled at first but decided to trust the new fangled technology of GPS.