Rev counter tricks !

[Tom_S14]

Sorry if this is really sad by the way....
I've always suspected the speedo and rev counter were playing tricks with me, so last night I did a little test, comparing the indicated speed and revs against the speed and revs the ECU knows but lies to the driver about (using my gadget).

In 5th gear, revs are accurate upto 4k (indicated 100mph actually 90mph). Over this, it starts fibbing badly. At 5k revs it's already over-reading by 400 revs... and the trend continues.

So don't worry if you're in 5th gear with your rev counter buried in the red - you're probably only doing about 6k revs and you're fine.

It's not that my rev counter is broken because I tested that it doesn't do it in any other gear (well ok I didn't test reverse).
Just thought I'd let you know anyway http://300zx.co.uk/200sx/ubb/smile.gif
Tom

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1996 Blue/Green S14 (manual)
K&N cone filter
2.5" Tube-torque Cat Back Exhaust.
TechTom MDM-100
Race-Technology AP-22
http://tom.marshall.tripod.com

[geoff_s14]

Originally posted by Tom_S14:


It's not that my rev counter is broken because I tested that it doesn't do it in any other gear (well ok I didn't test reverse).
Just thought I'd let you know anyway http://300zx.co.uk/200sx/ubb/smile.gif
Tom


Tom,

So you're saying that the tacho is accurate in every other forward gear other than top? What about neutral?

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Geoff
Emerald S14a

http://www.animfactory.com/animations/transportation/cars/mirror_md_clr.gif

[Tom_S14]

Geoff,
Yep, that's what I reckon.
Neutral... haven't tried that one yet. I'll give it a go http://300zx.co.uk/200sx/ubb/smile.gif

Must be a deliberate thing... but why ?

Tom

[geoff_s14]

Originally posted by Tom_S14:
Geoff,
Yep, that's what I reckon.
Neutral... haven't tried that one yet. I'll give it a go http://300zx.co.uk/200sx/ubb/smile.gif

Must be a deliberate thing... but why ?

Tom

Could you also cross-check the speedo accuracy through the gears? I'm wondering if the speedo is set up to deliberately over read when in top, and the tacho set accordingly in order to maintain the appropriate relationship between indicated speed and revs.

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Geoff
Emerald S14a

http://www.animfactory.com/animations/transportation/cars/mirror_md_clr.gif

[Papa Lazarou]

Sorry wrong post!!

[This message has been edited by Papa Lazarou (edited 26-10-2001).]

[Tom_S14]

Geoff,
Exactly the same thing crossed my mind actually.
As far as I've worked out, the speedo basically over-reads by 10% in all gears at all speeds. Worst is indicated 80, which is actually 70, most probably completely deliberate, since the whole world thinks it's cruising at 80mph wondering why the police don't take an interest http://300zx.co.uk/200sx/ubb/biggrin.gif
I've only had the car upto around 145 indicated, and it was still 10% in error.

So, in short, yes.
Becuase in 5th, the 10% is a lot more obvious to the driver, and the rev counter is just fibbing to make you think that the car really is doing it's top speed, and it really is near the red line.


Tom

[This message has been edited by Tom_S14 (edited 26-10-2001).]

[Tom_S14]

Ok, I know this is totally uninteresting...
Geoff,
In gears 1-4, you can expect the rev counter to over read by a maximum of 200-300 revs. I didn't really notice this before, because I don't normally hold 6k revs in 3rd for a while to check.... but anyway.... I'm done....
Tom

[Actual_Ben_Taylor]

I used to work in a place where they made instrument clusters, and they are designed to over read. I remember there was a trick you could do in the original Puma's to put the cluster in diagnostic mode and it would display the revs, speed, etc in the LCD section where the milage shows up normally. It was always well out compared to the needle on the dial. Wonder if you can do this on the nissan cluster??