MPH to KPH Question

[shanklylfc]

Is the dial cluster responsible for displaying either MPH or KPH depending on country or some sort of signal from the gearbox?
Ive got a J spec car, and need to replace the dial cluster, now the car must have a converter sitting behind the dash somewhere, if I replace the cluster with one from a UK spec car will I need to remove the converter as well, or is the speed in MPH or KPH coming straight from the gearbox and sent to the cluster?

[uktotty]

dont the clocks just have both kmh and mph displayed?
Therefore 70 mph = 112.kph

[cclarke99]

Input to the speedo is a pulse signal from the ABS ECU, which is cleaned up and drives the meter in the speedo. It would be very difficult to modify this signal so my guess is that it is all the same, just the actual dial markings that are changed. Not the calibration of the markings, but just the presentation. So there should be no problem swapping speedos from any type of car.

[mrzwei]

That has to be right, for example, my Saab, and I think most other cars I have driven, have mph and kph marked on the same dial. We are one of the few countries to use mph so we have to do that.

[shanklylfc]

Is not as simple as saying read the mph instead of the kph on the dial. the odometer would be clocking up in Kilometers and not miles. What I wanted to find out is how the speedometer and odometer uses the speed pulse to know whether to display in MPH for the UK or KPH in Japan.
I thought that a speed pulse is taken off the gearbox (although cclarke99 says from the ABS ECU) and it will read in KPH, and cars destined for the UK market would have some sort of converter added at the factory, and if they do, then was it built into the dial cluster?
or is the speed pulse controlled by the ECU, and that is how it is changed to show MPH?
I was under the impression that speedo converters are just a simple set of resistors used to slow the pulse down by a certain ratio
If I put a cluster designed for the uk market on my jspec (which i presume has had a converter fitted behind the cluster) then the speed pulse would be converted twice and so showing the wrong speed and odometer readings.

[mrzwei]

Good point

[cclarke99]

Yes you're quite right about the odometer and i also see what you mean about the convertor. Fitting this in the input to the speedo presumably modifies the pulse rate so that the odometer runs in miles. This means that the speedo will read in mph, but on the kph scale (so you've got a 200mph speedometer) - is this true? The problem would be that, according to my circuits, the engine management and power steering would then receive the wrong speed signal. if you wanted to fit a UK speedo, then just emove the convertor. I imagine that the conversion at the factory is just done by fitting a different part number speedo, although I notice that there is an additional white/black wire going to earth in the diagram - is this what tells the speedo it is in miles?

[shanklylfc]

Thanks for taking an interest in this ccleark99
My clock reads upto 180 and is in MPH, it doesn't have a KPH scale on it. I dont know if it has had replacement dials and a converter, or a uk standard cluster and no converter or something else.
I haven't seen a UK car on the inside to compare it with, so I don't know how, or if it does, differ.
That's why I don't know whether to buy a cluster off a Jspec or UK car, because I don't know how the conversion to MPH is handled by the car in the first place. I thought it must be in the cluster as first, but could easily be handled through the ECU i suppose.

[mrzwei]

Not a lot of practical use but you're quite right to be concerned. My Saab manual says: 'Vehicles are fitted with an electronic transducer which measures the rotational speed of the transmission final drive, and converts the info into an electronic signal, which is then sent to the spedo module. The signal is also used as an imput by the ECU and the cruise control ECU, the trip computer and the traction control ECU.'  So a much more important bit of kit than I first thought. Sorry that's not Roadster specific.

[cclarke99]

The speedo in my car ('02 pre-facelift UK model) reads up to 150mph (with equivalent kph scale) and the manual shows the equivalent kph speedo for RHD cars reading up to 240kph (same as 150mph). So yours is not a standard mph or kph unit, although I'm not sure what was sold in the USA. As far as I can make out the speedo merely cleans up the pulses from the ABS unit before passing them onto the power steering and engine ECUs. So all three units will see the same pulse rate for a given wheel speed. For the production car this suggests that the only thing they change is the speedo (which has to have different dials in it as well) as otherwise the other two units would have to be changed to match. So my theory says that a set of UK dials would work fine in your car. It's also interesting that your speedo ended up with a max of 180mph as that does not correspond to the standard scale, which means that either the speedo or odometer will read slightly wrong (speedo 20% low or odometer 20% high or about 10% out for each). Alternatively they would have to modify the circuit inside the instrument assembly that drives the speedo to get that right. How accurate do you think the readings are on your car? The whole thing could be a crafty way to avoid changing the signals that go to the other ECUs by too much. Change the pulse rate to 0.75 of the original value (rather than 0.63) so that the other ECUs are not too confused, recalibrate the speedo by fitting the new dial (which they'd have to do anyway) and accept that the odometer overreads by 20% - but perhaps I'm reading too much into this!

There are a couple of related threads with links to people who make the converters below

 m http://www.mr2roc.org/phpBB3/viewtopic.php?f=11&t=12896 m

 m http://www.mr2roc.org/phpBB3/viewtopic.php?f=7&t=1488 m

[cclarke99]

Done some research re above on the excellent  w www.toyodiy.com w  site. These are based on '02 model with 5 speed manual

Instruments are different per market
RHD
 m http://www.toyodiy.com/parts/p_E_2002_T ... _8301.html m
Japan
 m http://www.toyodiy.com/parts/p_J_2002_T ... _8301.html m
USA (two types shown?)
 m http://www.toyodiy.com/parts/p_U_2002_T ... _8301.html m

ABS is the same for RHD & Japan, but different for USA
RHD
 m http://www.toyodiy.com/parts/p_E_2002_T ... _8414.html m
Japan
 m http://www.toyodiy.com/parts/p_E_2002_T ... _8414.html m
USA
 m http://www.toyodiy.com/parts/p_U_2002_T ... _8414.html m

Theres only one Engine management unit shown for Japan, three for RHD (South Africa, Hong Kong and the rest) and no less than eight for USA

[shanklylfc]

Thanks again for reply's guys, especially cclarke99

The readings on the gauge are out by about 10MPH, 30MPH is reading 20MPH, and past 30 just sticks until you come to a complete stop, It was like this when I bought It last month from someone on these forums. looking at some of his previous posts, he may have tried to replace dials, because he says in one post, "not to pull the needles off the dial because you will end up 10MPH out and about 200 rpm down".
I think I'll follow your advice and just get a second hand UK spec cluster, and see what is what. I'm a bit worried that the speed limiter will be back on at 112MPH when I remove the converter box, unless this is also determined by the cluster. Thanks also for pointing out the links, they pointed me towards these guys http://www.kmh-mph.co.uk/index.htm which may also be of help to others. If the second hand cluster works, then I will have to see if they will match up the new odometer, with my existing one. and if it doesn't work then I'll have to let them sort it out for me, and rely on a satnav for my speedo to get there.
I might try and remove the converter first though, to see if that is the problem, like in one of the posts you directed me to. It would be great if it was all down to a faulty converter box, I could just fit a new one and save so much hassle in trying to match up odometer readings, which may be the hardest thing to get sorted.

Edit: should I disconnect the battery before working on the cluster, am I likely to set off an airbag?

[cclarke99]

Just found what I think is the the previous post ( l viewtopic.php?f=11&t=27420 l  ?), and the fault described there could be easily caused by the convertor. It would be worth disconnecting it to see if it is the problem. Also it may be more prone to noise than the standard setup so make sure that the connections are good. It would be interesting to know how it is connected as that might give a clue as to how the speed limiter function works. I'd disconnect the battery, as working on the instruments you'll be in the firing line if the airbag goes off

[shanklylfc]

Think this may be sorted now, but still need to get someone in front of me to check for certain.
I took the cluster out today, to look for the converter, but I could not see one behind the dash, so I took the cluster inside and took it apart. I was pushing on the needle and found if you push it up slightly, it would move up on its own up to about 60MPh and then stop, push a little more and it would go right to 180MPH, so it was getting stuck between 60 + 70MPH. so I pulled the needle off and put it to 0MPH but it was still doing the same, so I thought I would just put it back together and put it back in the car.
Drove off and had no speedo at all, so I thought I had completely knackered it. so I took off the surround and plastic clear cover and pushed the needle up while the car was ticking over, once I had pushed it past 60MPH it shot up to 150MPH on its own, so I took the needle back off and positioned it at 0MPH again, and now seems to be working ok. drove it round a few 30MPH areas behind other cars and dial was showing 32, drove it up to 60-70 a few times and it didn't get stuck. Ive probably spoke too soon though, and it still way off, i probably got behind a couple of Sunday drivers doing 20 or speeders doing 40, but Ive got my fingers crossed  s:D s:D .
 edit:
we must have been typing at the same time, I did disconnect the battery just in case the air bag went off. I didn't find the converter though, I wonder where they put it?
the link you put up was posted by the guy i bought the car off.

[mrzwei]

Just a thought, but you should be able to verify the speed via the rev counter / gear you are in if you know the gear ratios. According to my quick reference guide, the MRS has a final dif ratio of 4.312 whether US or Euro.
1st 3.116 (US/Euro)
2nd 1.904 (US / Euro)
3rd 1.392 (US)  1.310 (Euro)
4th 1.013 (US) 0.969 (Euro)
5th 0.815 (US / Euro)

Calculation would have to assume non SMT and stock wheels and tyres.

Haven't got a clue how to work it out though   s:D s:D

Or, just ask a willing fellow member with an MRS to record what the speedo reads at a particular revolution figure in a particular gear

[shanklylfc]

thanks mrzwei that is very handy to know, unfortunately the rev counter is also out, the guy i bought it from said about 200 revs. Ive just done the calculation and it says

                    1                2                3                 4                 5           
500      2.5       4.0       5.5       7.6             9.4           
1000     4.9       8.0       11.0      15.1      18.8           
1500     7.4       12.1      16.5      22.7      28.2           
2000     9.8       16.1      22.0      30.2      37.6           
2500     12.3      20.1      27.5      37.8      47.0           
3000     14.8      24.1      33.0      45.4      56.4           
3500     17.2      28.2      38.5      52.9      65.8           
4000     19.7      32.2      44.0      60.5      75.2           
4500     22.1      36.2      49.5      68.1      84.6           
5000     24.6      40.2      55.0      75.6      94.0           
5500     27.0      44.3      60.5      83.2      103.4           
6000     29.5      48.3      66.0      90.7      112.8    

so in 3rd gear at 3000 revs it should be showing about 31MPH if i factor in the 200 revs, I'll try it out later and post back.
Thanks again guys, you've been very helpful with my problem, I just hope it fixed now.

chart looks ok in edit but when posted goes a little funny, but still readable.

[shanklylfc]

Just borrowed a sat nav, reading at 30MPH, speedo is showing 35 -36MPH, 3000rpm in second gear, and at 60MPH on the satnav is 67MPH on speedo, so its looking like is out in the other direction now, but I don't know how accurate the sat nav is. but its not sticking, so that's a bonus.

[mrzwei]

Best 'control' is still to see what a similar MRS speedo reads at the same revs in the same gear 'cause the same signal might control the rev counter and the speedo so you get the same degree of error.
To eliminate further error, dont do it in third or fourth because of the difference between US and Euro ratios, 5th would be better. I'd do it, but I don't know whether a UK spec Roadster has the same ratios.

[cclarke99]

The satnav will be very accurate, much better than any speedo. The figures you give suggest that the speedo is scaled about right but overreading by about 6mph, so if you moved the needle back by 6mph it would read perfectly. Can you use the satnav to find out how accurate is the odometer? That will tell you if the pulse input is at the right speed. If the odometer was perfectly accurate you'd need a speedo with a 240mph dial to match. As this would look absurd, perhaps they've used a 180mph dial and then have corrected out the error by moving the speedo needle forward. This isn't a perfect fix as it will overread at low speeds and vice versa. In doing this they may have twisted the spring in the speedo, hence the sticking?

[mrzwei]

All I would add to that is you still have a problem with the rev counter, so for me, the pragmatic comparison test still stands. How accurate are these things anyway? Supposed to read low so we keep our speed down? Interesting thread.

[shanklylfc]

sorry I forgot to add, the speedo looks like this one, except it does not have the inner gauge readings http://www.thor-racing.co.uk/images/mrs_dials4.jpg and when I had it apart earlier you can see the K of the km/h has been covered over.
The odometer is reading perfectly against my mk 1, I went round the block earlier, and both just ticked over to 1.5 miles as I pulled in through the gates.
I don't know how I could move the needle back though, is isn't spring loaded to move to a fixed position, if the odometer trip button and the 0mph sticky out bit wasn't there, then it would just go round and round, it looks like a small motor, about the size of four 10p pieces stacked. Ill try to push it back a bit when im driving, and see if that works

Edit:
just found this thread http://www.mr2roc.org/phpBB3/viewtopic.php?f=9&t=26796&p=330092&hilit= looks like this car is reading out by 5mph so maybe about right, or we both got a problem
edit
saying that according to this PDF http://www.northwestmr2.com/incoming/dutch/Toyota/mr2%20spyder/Repair%20Information/Repair%20Manual/20%20-%20Body%20Electrical/21%20-%20Combination%20Meter%20-%20Inspection.pdf it shouldn't be that far out

[rabscott2003]

I just bought a 2001 mrs Import the guy before me had a problem with the speedometer not working properly jumping on anf off. He gotthe clocks changed from KPH afer this problem and didnt work, then changed the cable from the gearbox still doesnt work,i bought the car with it not working and the clock needs reset to the MOT's figures in miles when i get it working again. How can i get it working? Can i just replace the speedometer sensor on the gearbox to work? What happens about the conversion do i need to change anything since the clock is changed? Its a 180MPH speedometer.
Should i check the mechanic connected the cable correctly?

I would like your comments from someone who has experienced this.

Thanks again

Robert
Hawick
Scottish Borders

[Cap]

If you read the Previous Posts..  you will understand the Gear Box is not responsible for making the Spedo Work..  The ABS Computer is..

If the Spedo Cluster is not working..  then the Spedo Cluster is the Likely Problem Child..  As the Engine ECU receives it's Spedo Sig FROM the Spedo Cluster..  and if the Engine ECU was not getting that Sig, the Engine would be tossing a Check Engine Lite at you..  

Get a Different Spedo Cluster, and Swap it in..  

Cap

[onion86]

I thought about this the other day because I was thinking about getting hold of the Neon speedo dials from the GB.

I haven't got the best pic, but my speedo dial goes to 180 (km/h) as per:


I'm assuming this must've been modified in some way to convert it on import as it reads perfectly in mph (about 2mph out from satnav at 70mph). I'm guessing though that it's not a standard type thing in the dash that has been discussed earlier in this thread as it still has the stock kmph dials which obviously aren't the same as the positions of the UK mph dials.

I was wondering whether there was any chance to get this changed without having to make custom dials. I was also hoping to get hold of mph dials so that I can see how fast I'm going in kmph for if I go over to drive in Europe.

[rabscott2003]

If you read the Previous Posts..  you will understand the Gear Box is not responsible for making the Spedo Work..  The ABS Computer is..

If the Spedo Cluster is not working..  then the Spedo Cluster is the Likely Problem Child..  As the Engine ECU receives it's Spedo Sig FROM the Spedo Cluster..  and if the Engine ECU was not getting that Sig, the Engine would be tossing a Check Engine Lite at you..  

Get a Different Spedo Cluster, and Swap it in..  

Cap

I dont know what the spedo cluster is? If the dials are new and should work with a new cluster what kind of operation do i need to make to perform the replacement? And how much would it cost roughly?

Thanks again