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[05omegav6]

Not driven it for a few weeks , but iirc 80 in mine is a touch under 3000rpm. Diff is def 3.7, but not sure if lsd or not. Car is quite reluctant to light up the back end. :-/

[Kevin Wood]

Keeping things simple for a second  an idicated 80 in an auto plod spec car gives 3500. An indicated 80 in mine gives lass than that. Needs another 250 rpm at 80. As I understand it.

Definitely Auto? 'cos the manual box would give you slightly lower gearing again. Otherwise, we're looking for a diff ratio > 4.22:1. Might have been a plod special, I suppose. :-/

What tyres were on this car?
.. and do you know the speedo was reading correctly / with known error?

[2woody]

there are no higher diffs than 4.22.

a 4.22 will give you 51.9 mph in 3rd at 3000 revs
a 4.22 will give you 72.1 mph in 4th at 3000 revs

Chris - YHM !

[feeutfo]

Keeping things simple for a second  an idicated 80 in an auto plod spec car gives 3500. An indicated 80 in mine gives lass than that. Needs another 250 rpm at 80. As I understand it.

Definitely Auto? 'cos the manual box would give you slightly lower gearing again. Otherwise, we're looking for a diff ratio > 4.22:1. Might have been a plod special, I suppose. :-/

What tyres were on this car?
.. and do you know the speedo was reading correctly / with known error?

Def plod auto, I changed the cam belt on it, and the hbv. It's 04 registered and was ordered but never actually purchased by the police hence the private owner had it from new. He said a dealer bought them all from vx and where all lined up in a row as a job lot.

Tyres where stock size 235 45 17 Dunlop sp 9000 with stock 03 wheels. I drove it several times after cam belt fitting, and also after he lpg'd the car with a 100 litre tank in the boot to see if it lagged as my old car did on gas. It didn't.

I do remember commenting his steering box was suitably tight. It was lower than stock mv6 and firmer. Suspension was boge.


Re speedo can't remember if it was calibrated or not. If it was that might explain it...?

Last I heard the car was up for sale. A while ago now though.

Owner has since bought a Black Elite. He doesn't like the suspension. 

[feeutfo]

He just replied to my text. Speedo is calibrated with confirmation sticker on the dial.

Also the car is currently on auto trader. 

White 3.2 saloon. 

[Kevin Wood]

Remember there are several potential sources of error in what you have observed. Speedo reading is one. If the car was a special order it might have ended up with a dash configured for different WRPM than the wheels that ended up bolted to it. It might have had a calibrated speedo which was never properly configured, or been destined to get a calibrated speedo so they just slapped a standard dash in before sale.

Then there's the tachometer. It's a relatively crude gauge. Not impossible that it was a couple of hundred RPM out.

Owner has since bought a Black Elite. He doesn't like the suspension.

Here we go again..

[Kevin Wood]

He just replied to my text. Speedo is calibrated with confirmation sticker on the dial.

Of course, calibrated doesn't mean accurate, it means verified to be reading within given tolerances (unknown to us).

I think it's highly unlikely that a bespoke diff would have been made for this car, so the difference must be in calibration of the dash. :-/

We have a new FAQ on this subject thanks to some rather useful graphs contributed by 2woody:

http://www.omegaowners.com/forum/YaBB.pl?num=1312469626

Kevin

[feeutfo]

He just replied to my text. Speedo is calibrated with confirmation sticker on the dial.

Of course, calibrated doesn't mean accurate, it means verified to be reading within given tolerances (unknown to us).

I think it's highly unlikely that a bespoke diff would have been made for this car, so the difference must be in calibration of the dash. :-/

We have a new FAQ on this subject thanks to some rather useful graphs contributed by 2woody:

http://www.omegaowners.com/forum/YaBB.pl?num=1312469626

Kevin

Yes thanks 2woody. 

So with my wheel size in mind, some of the effect of the 4.2 will have bern lost...? If so, how much? Is it quantifiable...?  :-/

With the LPG tank as well hopefully should be at least back to square one or better.

Also wonder when 2woody is down again. Springs for dif seem a fair swap...  

[feeutfo]

And another q, possibly a stupid one, but is there anything to gain put of setting the wheel size by tech2?

Will that bring the speedo in to line with actual speed?

[2woody]

I'm around next week as it happens...

the Omega size of tyre gives 817 wrpm, so your 821 gives only a 0.4% error. not worth correcting

[Kevin Wood]

Wheel size was the difference between 3074 and 3036 RPM. Not significant at all.

Configuration via Tech 2 is only to adjust for different Omega wheel sizes, you can't tweak it freely. It might be that one of the other sizes is a better match but I doubt it, given that your WRPM has changed by only just over 1%. There's probably more variation between different brands of tyre.

[Martin_1962]

Ok thanks Kev. 

So that proves that, which is good. But it also proves plod spec is lower geared/higher rpm at 80.

Keeping things simple for a second  an idicated 80 in an auto plod spec car gives 3500. An indicated 80 in mine gives lass than that. Needs another 250 rpm at 80. As I understand it.

Calibrated speedo may be the culprit

[Kevin Wood]

I'm around next week as it happens...

It is about time for someone to say "Curry"?

[feeutfo]

"CURRY" ....? 

Or whatever.

[Kevin Wood]

"CURRY" ....? 

Thought so.

Or whatever.

You can experiment if you like. I'll stick to what I know, thanks.