Speedometer Error

[jeddeano]

Good days mates!
I am having big trouble with my gauge. It is not accurate. I cross checked it with my GPS.

First time I checked my speed with my GPS, my set up was:

Tires: 195/55/r15
Speedometer reading: 120kph
GPS reading: 90kph

2nd time
Tires: 225/45/r17
Speedometer reading: 120kph
GPS reading: 110kph

Any input guys? Should I change my gauge? Btw,my tranny is locked into a 2wd. Space Wagon here in the Philippines is not on a 4wd configuration. I just put a hyper sports gear engine from Japan.

Thanks!

 

[Dave_GSR1.8]

I know that my Lancer CC GSR on stock wheels and tyres reads about 4 - 5kmh high at 110kmh, I don't mind this as it gives me a little bit of a safety margin, but if your 1st test was on stock tyres then that error is a bit too much. Youir second test was much better but you may have one error cancelling out another.

I would try and get a calibration on stock wheels and tyres; that way you can work out what your underlying error is.

Are "Tires: 195/55/r15" stock on a "Space Wagon" ? Also did you put a new gearbox in with your new engine ? I am not sure where the speedo take off is on your set up, if you swapped the gearbox this may be something to consider as having an effect.

Once you have done that, then you can decide what the next step is, I would not start changing gauges until you have pin pointed the source.

 

[4piknup]

First job would be to work out the odometer error. Gps may be bad for this as you have many hills.

Then there is 2 variables for the speedo. Needle position and spring preload. Preload on the spring will affect the rate of needle movement and needle position affects...well needle position.
spring preload is a pita to set right. But basically if your speedo is out 10kmh across the board then just shift the needle. This is why having odometer correct first is important as this sets up the spring preloading. If the odo is out 10%, you probably cant increase spring tension enough to compensate. You need to be in the ball park first.

But what you can do easily and quickly and will fix your issue sufficiently is needle position. Pullthe plastic front cover off the speedo. Lever off the needle. Go for drive and travel at 100kph and put the needle on to indicate this 100kph. You may need a few goes to allow for needle weight and whatever else.
its easier with cruise control and may need a friend to help. Very difficult by yourself on a windy road. And use common sense and be careful.
Think of excuse in case police pull you up.

 

[jeddeano]

I know that my Lancer CC GSR on stock wheels and tyres reads about 4 - 5kmh high at 110kmh, I don't mind this as it gives me a little bit of a safety margin, but if your 1st test was on stock tyres then that error is a bit too much. Youir second test was much better but you may have one error cancelling out another.

I would try and get a calibration on stock wheels and tyres; that way you can work out what your underlying error is.

Are "Tires: 195/55/r15" stock on a "Space Wagon" ? Also did you put a new gearbox in with your new engine ? I am not sure where the speedo take off is on your set up, if you swapped the gearbox this may be something to consider as having an effect.

Once you have done that, then you can decide what the next step is, I would not start changing gauges until you have pin pointed the source.

Stock tires of space wagon is 185/70/r14 with a 1.8 4g93. Stock gauge of space wagon here is like in the Europe edition with a top speed of 220kph. My gearbox is a stock hyper sports gear locked into a 2wd. I did that because what I got is only a front cut hyper sports. I didn't have the rear differential, propeller and gas tank. Right now my gauge is the original one from the hyper sports gear with a 180kph top speed and up to 9,000rpm tachometer. Thanks for your help mate, i just didn't know what to do. All asked all of my mechanic friends here in Manila and they are also confused.

 

[jeddeano]

First job would be to work out the odometer error. Gps may be bad for this as you have many hills.
Then there is 2 variables for the speedo. Needle position and spring preload. Preload on the spring will affect the rate of needle movement and needle position affects...well needle position.
spring preload is a pita to set right. But basically if your speedo is out 10kmh across the board then just shift the needle. This is why having odometer correct first is important as this sets up the spring preloading. If the odo is out 10%, you probably cant increase spring tension enough to compensate. You need to be in the ball park first.
But what you can do easily and quickly and will fix your issue sufficiently is needle position. Pullthe plastic front cover off the speedo. Lever off the needle. Go for drive and travel at 100kph and put the needle on to indicate this 100kph. You may need a few goes to allow for needle weight and whatever else.
its easier with cruise control and may need a friend to help. Very difficult by yourself on a windy road. And use common sense and be careful.
Think of excuse in case police pull you up.

Mr jack of all! Thanks for your inputs! That was amazing. But, how about my tach? My tachometer is match with my speedometer. I mean if I run 120kph my tach is indicating 3,500rpm which is I think it is correct. Right? I'm screwed up.

 

[jeddeano]

Sample of my speedomter.

 

[4piknup]

Dont worry about the tach. They cant book you for 3000 rpm in a 2500rpm zone.
Your tach is driven from the ignitor. It will be ok.

The 2 different gearbox ratios are roughly 10% different. But your tyres complicate the issue too.

 

[4piknup]

Is there a difference in the speedo drive gears on the end of the speedo cable? Ie no of teeth?

Might pay to change it if there is. Maybe it will make it closer to correct.

 

[4th]

Incorrect wheel size? You have a smaller diameter so spin faster registers higher but in reality you are going slower?

Tires: 195/55/r15
Speedometer reading: 120kph
GPS reading: 90kph

RVR Factory Wheel / Tyre Size: 15x7 @ 195/65 R15

215/65 R15 fit without front scrub at full lock on RSR spring

GPS isn't always accurate especially if cloudy with a chance of speeding fine

 

[Benzo4gT]

cloudy with a chance of speeding fine

HAHA, sounds exactly like the weather around my parts ATM

 

[jeddeano]

Is there a difference in the speedo drive gears on the end of the speedo cable? Ie no of teeth?
Might pay to change it if there is. Maybe it will make it closer to correct.

Hmmm. But currently I am using the stock gauge of hyper sports gear. From speedo cable to tranny to gauge. All are from the half cut.

 

[jeddeano]

Incorrect wheel size? You have a smaller diameter so spin faster registers higher but in reality you are going slower?



RVR Factory Wheel / Tyre Size: 15x7 @ 195/65 R15

215/65 R15 fit without front scrub at full lock on RSR spring

GPS isn't always accurate especially if cloudy with a chance of speeding fine

That's my first suspect my tire size. So from 195/55r15 I changed it to 225/45r17. Error is still there, 10kph

 

[4piknup]

How many teeth on your old spacewagon speedo drive gear and how many on the sportsgear drive gear. Is the drive gear the same?

Maybe there is 10% different number of teeth on gear and you can swap them to be all fixed.

 

[EVO-00X]

Your speedo gears are different. Unbolt it from the top of the gearbox and pull it out. Count the number of teeth on it.
Here's a pic of GSR, EVO I-III speedo gears.

Below I have listed the number of teeth found on the RVR/Spacewagon variations:
The N23W has 28 teeth. One early model has 29 teeth which was manufactured Jan 91 to Aug 92. The rest had 28 teeth up to 1997.
The N23WG has 27 teeth.
The N43W has 29 teeth.

 

[Super Top]

Incorrect wheel size? You have a smaller diameter so spin faster registers higher but in reality you are going slower?


RVR Factory Wheel / Tyre Size: 15x7 @ 195/65 R15

215/65 R15 fit without front scrub at full lock on RSR spring

GPS isn't always accurate especially if cloudy with a chance of speeding fine

N23WG Factory tyre size is: 215/65-R15 15x6J

N23W Facory tyre size is: 185/70-R14, 205/65-R14 or 205/65-R15

According to ASA.

If you are using an HSG box and speedo I think your problem lies in your tyres. They're too small.
Stock tyre size on an HSG is 215/65-R15. So your tyres are about 4% too small. That alone leads to at least 4 km/h speed difference between the speed on the speedometer and the actual ground speed.
Every speedo has a certain deviation that accounts for some difference between the speed readings.

My HSG has the factory snow 215/65-R15 tyres. My summer tyres are 235/45-R17 even they are 2.6% smaller than the factory size.

 

[Django]

EVO-00X to the rescue once again!

 

[4piknup]

So they are in 5% increments basically. Op needs to pull his gear and count the teeth. Then get the one that makes it more correct.
but really as I said, the gear corrects the odometer. You need to get this right then the speedo.

 

[EVO-00X]

[SIZE=10pt]Ahhh yes, thanks for the info about the stock sizes.[/SIZE]

[SIZE=10pt]Overall tyre diameter.[/SIZE]
[SIZE=10pt]185/70/14 = 615mm[/SIZE]
[SIZE=10pt]205/65/14 = 622mm[/SIZE]
[SIZE=10pt]195/65/15 = 634.5mm[/SIZE]
[SIZE=10pt]215/65/15 = 661mm[/SIZE]
235/45/17 = 643mm

[SIZE=10pt]The 215/65/15 is larger than the acceptable 15mm difference in overall diameter and technically contravenes ADR unless you get your speedo recalibrated or change your overall outside tyre diameter. [/SIZE][SIZE=10pt]Yes it will throw your speedo out a fair bit.[/SIZE]
[SIZE=10pt]Go for a wheel/tyre combination similar to stock to maintain speedo accuracy.[/SIZE]
[SIZE=10pt]The closer you get to the oem figure, the more accurate the speedo will be.[/SIZE]
[SIZE=10pt]Any excuse to throw on a set of new mags and tyres is a good one! [/SIZE]

[SIZE=10pt]Here's some info when I was engineering my car:[/SIZE]
[SIZE=10pt]The overall outside diameter of the wheel and tyre combination must be no more than 15mm over the largest diameter wheel and tyre combination specified for the vehicle and not more than 15mm below the smallest diameter wheel and tyre combination specified for the vehicle. [/SIZE]

[SIZE=10pt]Manufacturer Overall Outside Diameter measurements as per tyre placards on Lancer Evolution[/SIZE]
[SIZE=10pt]195/65/15 = 634.5mm 205/60/15 = 627mm[/SIZE] 205/55/15 = 605.5mm

[SIZE=10pt]Therefore the wheel and tyre combinations allowable under section LS would include, but not be limited to, the following which fall within manufacturer overall diameter specifications:[/SIZE]
[SIZE=10pt]205/45/16 = 591mm 205/50/16 = 611mm[/SIZE] 215/50/16 = 621mm
[SIZE=10pt]205/40/17 = 596mm 215/40/17 = 604mm[/SIZE] 205/45/17 = 616mm
[SIZE=10pt]215/45/17 = 625mm 205/40/18 = 621mm[/SIZE] 215/40/18 = 629mm
[SIZE=10pt]215/35/18 = 608mm 215/30/19 = 611mm[/SIZE] 215/35/19 = 633mm

 

[4th]

depending how the speed registers but another route might be a speedohealer

really great for motorbikes when you change sprockets -1 +2 etc, unsure about cars

http://www.healtech-electronics.com/products/sh/

https://www.youtube.com/watch?v=omSabPhy0Dc

 

[evo-gsr]

Considering the OP is in the Phillipines I dont think the ADRs will bother him too much Rob.