inaccurate tripmeter reading...

[fabianyee]

For the last couple of years, the consumption seemed to be bad when I calculate based on the fuel pumped in and distance shown on the tripmeter... Then for my past few work trip down to Johor, I started counterchecking the tripmeter with :-1) those roadmarkers at every 100m intervals on PLUS highway.2) Garmin GPS cyclometer I used for my cycling. Both showed that my tripmeter is underreading by ~30%!!!!! Meaning when the tripmeter showed 100, the car have actually travelled 130km... a 330km journey only registered ~250km on the tripmeter.... No wonder the car fuel consumption looks bad!!!! No issue with the speedometer, it overreads by about 5-7kph which is normal... So that means the meter cluster is receiving the correct signals from the rear axle. Speedo showing almost correct speed. OK... Only the tripmeter (and odometer) showing significantly lower reading... something not right...So what could be the culprit??? Anyone had this issue before? My first suspect is the failing plastic gears. Mine had been replaced before some 8-9 years ago.. Maybe some bits had broken off, causing it to make lesser rotations for the tripmeter. A 'higher level' problem could be failing electric motor which spins the plastic gears. What do u guys think?

 

[BlackCat]

Fab, you may have just answered your own question... The 8-9 years old gears may have lost a few teeth imo

A 'quick' check may help...

 

[fabianyee]

That would require taking out the instrument cluster... Malas...

Anyway, my intention was to share my issue with the underreading... See if anyone else having the same issue...

 

[pussy]

ha ha... you having the same problem i had earlier... very easy fix...plus you will need a spare speedo unit on the worst case... my reading now perfect...heheh

 

[mizhan]

i'm experiencing the same phenomenon as well with my stock M20B25. odo says RM70 of RON95 covers only about 250kms..

 

[jarance]

It could be the gear ration is wrong when you change it 8 years ago.

 

[Keano]

i'm experiencing the same phenomenon as well with my stock M20B25. odo says RM70 of RON95 covers only about 250kms..

I think your mileage & petrol consumption appears normal.

Typically, I get ~350km from ~50 litres of RON95 or only 7km/lt on my M40B18. Mainly bumper-to-bumper traffic in my case.

 

[pussy]

I think your mileage & petrol consumption appears normal.

Typically, I get ~350km from ~50 litres of RON95 or only 7km/lt on my M40B18. Mainly bumper-to-bumper traffic in my case.

i m getting 420km per full tank of petrol of 52 liters... mind you it's a 325i manual....and i m raping the car everyday when i drive...

 

[fabianyee]

It could be the gear ration is wrong when you change it 8 years ago.

Not for BMW rear diff design for the pulse generator.. The reading is the same for any ratio.. Anyway, the speedo reading is within tolerance so the speed signal from the rear diff is correct.

 

[jarance]

have a look here. there are many gear ratio available.
http://www.odometergears.com/products/BMW/3+Series+E30++82-94+Non-US/25

 

[Keano]

i m getting 420km per full tank of petrol of 52 liters... mind you it's a 325i manual....and i m raping the car everyday when i drive...

What the nos. indicate is that "raping" your E30 is less detrimental to the E30's fuel consumption as compared to an E30 caught in bumper-to-bumper traffic.

 

[astroboy]

So your oil change interval supposedly every 10k km, but it's actually 13k km.. I see some saving there.. :stupido2:

 

[julianpang]

Borrow an accurate meter from a fellow friend swap it in to test.

That will tell you if its the gear/meter or not.

 

[mizhan]

just compare speedo to GPS speed.

 

[pussy]

just compare speedo to GPS speed.

sorry Mihzan, that's half right... the speed of the car is at the differential, not at the wheels, so if the rims/tyres are off the 3% allowed, the speed of the car does not tally with the speed of the shown diff turning, hence with the GPS, it will give you the correct reading.

the second half right, the odometer millage is taken from the differential, that means the distance covered is correct on the odometer, but on the 'off reading due to the tyres' it will be either less or more, in mostly 'less' .

what fabian is trying to say, his one does not tally with his GPS on distance covered based on his odometer reading (lesser), but his tyres are within the allocated %.



But, for me, it's not about the distance or lesser petrol burned, it's the 'JOY' of driving a iconic e30 !!

 

[pussy]

What the nos. indicate is that "raping" your E30 is less detrimental to the E30's fuel consumption as compared to an E30 caught in bumper-to-bumper traffic.

yes, correcto my friend...i rather have the car raped in open road, then suffer in traffic !

 

[fabianyee]

have a look here. there are many gear ratio available.
http://www.odometergears.com/products/BMW/3+Series+E30++82-94+Non-US/25

ah... I see what u mean, but I had also counterchecked way back using the PLUS highway roadmarkers... It was off by 5 -10%, I forgot exactly by how much but it wasn't significant. I used to get >400km per tank back then leh, sometimes even get close to 500km before the light comes on...

 

[Ecc0]

well..bright side is that, your car will show less KM as it actually did, once you decide to sell it, and its not cheat..wwoohohohoh

 

[fabianyee]

well..bright side is that, your car will show less KM as it actually did, once you decide to sell it, and its not cheat..wwoohohohoh

my odometer aledi showing 392,xxxkm now... don't think it'll make much difference..

 

[julianpang]

Come... We set our trip meter to zero and we drive side by side to compare.