Issues & Defects from factory

Majestik · 12-07-2009, 09:24 PM

I also read somewhere that it's incorrect on purpose so we have to service our cars sooner.
I dunno how that would work though...

GTRFAN · 12-07-2009, 09:48 PM

Quote:

Originally Posted by Majestik

I also read somewhere that it's incorrect on purpose so we have to service our cars sooner.
I dunno how that would work though...

It's because the car travels less distance and speed than indicated.

Am I the only geek who studied physics? I am bored at work, so here goes my explaination.

Imagine the entire road surface of the wheel as distance measurement of approximately 2m. (circumference)

The ECU is constantly counting how many times the wheel rotates and how many times per second this occurs via the ABS wheel sensors (or gearbox on some cars)

The ECU then multiplies the distance by the number of times and gets the total distance travelled. It can also calculate speed based on the number of rotations per second/minute/hour

Here's the problem....the ECU has a distance measurement for the wheels that it uses for all calculations. This figure is the innacurate part and is a bit longer than actual wheel circumference.

Majestik · 12-08-2009, 01:43 AM

Quote:

Originally Posted by GTRFAN

It's because the car travels less distance and speed than indicated.

Am I the only geek who studied physics? I am bored at work, so here goes my explaination.

Imagine the entire road surface of the wheel as distance measurement of approximately 2m. (circumference)

The ECU is constantly counting how many times the wheel rotates and how many times per second this occurs via the ABS wheel sensors (or gearbox on some cars)

The ECU then multiplies the distance by the number of times and gets the total distance travelled. It can also calculate speed based on the number of rotations per second/minute/hour

Here's the problem....the ECU has a distance measurement for the wheels that it uses for all calculations. This figure is the innacurate part and is a bit longer than actual wheel circumference.

Ahhh.. Now i feel stupid!

I thought it was magic!!

evse82 · 12-08-2009, 06:41 AM

It's ok Ronnie, he got his facts wrong:

Lets say for instance you are cruising at 100kph, if you, at any given time, lift up the storage compartments in the back (behind both driver and passenger seats) and unscrew the panel, you'll find what is causing the speedo to go out...... leprechauns.. two of them.. they actually sit in there and screw up the signals being sent to the ecu. I find the best solution is to leave cheese outside the car, when it's dark they'll jump out to feed, thats when you hit them with a shovel. Sell em on ebay for some quick cash, good for a sway bar.

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12-07-2009, 09:24 PM	#1 (permalink)
Majestik Track Member Join Date: Aug 2009 Location: SE Melbourne, Australia Posts: 800 Drives: '13 Jet Black R35GTR Rep Power: 19	I also read somewhere that it's incorrect on purpose so we have to service our cars sooner. I dunno how that would work though...

12-08-2009, 06:41 AM	#4 (permalink)
evse82 Track Member Join Date: Nov 2008 Location: Melbourne, AUS Posts: 609 Drives: Black 370z MT Rep Power: 19	It's ok Ronnie, he got his facts wrong: Lets say for instance you are cruising at 100kph, if you, at any given time, lift up the storage compartments in the back (behind both driver and passenger seats) and unscrew the panel, you'll find what is causing the speedo to go out...... leprechauns.. two of them.. they actually sit in there and screw up the signals being sent to the ecu. I find the best solution is to leave cheese outside the car, when it's dark they'll jump out to feed, thats when you hit them with a shovel. Sell em on ebay for some quick cash, good for a sway bar.