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[Webby the Bear]

lol this 3.0 vs 3.2 is just as silly as my thread 

anyways...some developments and testing results tht I'd like you to peruse and make comments as to whether theres a problem...

so, was quiet at work today so plummed in the vacuum gauge straight from the brake servo (and tee'd it in so it was all still plumbed up)....... got car up to temp and at idle it was holding a ROCK STEADY vacuum of 20inHG. Perfect!!!

I then brought the rpm's up to 3k and held it there.....again, rock steady vacuum of 23inHG. PERFECT! This confirms there's zero exhaust restrictions, zero vacuum leaks and the engine is very healthy. really really pleased actually.

I blipped the throttle a few times and all vacuum dropped to 0 and came back to a steady 20inHG at idle. i believe this to also be completely normal.

while car was in i got my infrared thermometer out and got one of the mechanics to jump in and hold it at 2500k rpm. i checked the inlet and outlet temp. of both cats. now, my understanding is that the outlet should be 100oF hotter than the inlet. however, i got similar readings on both....

drivers cat:
inlet 180oF
outlet 135oF

pass. cat:
inlet 230oF
outlet 180(ish)oF

Would this have any bearing on performance?

So anyone got any advice / opinions on my testing (other than shut up  )

so we got an engine that's performing well with no exhaust blockages. very well in fact and backed up by evidence. but we have two cats that don't appear to be working correctly (certainly according to the infrared test.

so. can non performing cats affect acceleration? could this be a worn/wearing transmission issue? could this be a worn diff problem?

discuss 

The 2.5 will struggle to better 10 seconds with a'portly' driver at the helm.

  I am actually losing some weight. lost 10lb since being full time at the garage 

ok, lets look at this in a different way.

I am totally satisfied my engine is doing really well. and I have lots of evidence to support this.

SO

This ''issue'' is one of the following.....

1.) the transmission has a fault/is worn and is not transmitting the engines power to the wheels
2.) the diff is worn (just seen taxi al's reply so this can be scratched off the list)
3.) as you suggested before opti, the way I timed the 0-60 dash is way off and actually my performance testing/timing is very flawed and the car's actually performing bang on if timed correctly
4.) the info on original Vauxhall testing is flawed: the current boss (had personal reply  ) says they add on 200kg to the kerb weight including the driver. however ian coomber (importantly head of Vauxhall when the omega was launched) SURMISED that the car would be tested with driver and low fuel to improve figures....if thiss the case my initial testing is good!

[Nick W]

Your biggest problem is timing consistency.


If you are starting/stopping the timer then you will be miles off each time you do so. A quick test for this is simple: get a stop watch, and repeatedly try and stop it at the same number of tenths of a second. Unless you can do this everytime, then you cannot make any worthwhile comparisons.  Even if you are consistent the comparisons only apply to your techniques/equipment, not other published figures. Don't forget that you are introducing another error if you are using a visual check of the speedo as a timing event: they aren't very accurate, and nor are you! Tenths of a second aren't a particularly precise measurement either.


You also need to consider how many runs you are using to make your comparisons: if you're not into double figures(at least!!) you might just as well have a couple of beers and make up some numbers.

[Webby the Bear]

Completely fair point Nick.

I therefore conclude I need to lay this to bed until I can get my grubby paw(s) on some proper timing equipment at a ''grippy'' test track like Santa Pod. 

[Broomies Mate]

Completely fair point Nick.

I therefore conclude I need to lay this to bed until I can get my grubby paw(s) on some proper timing equipment at a ''grippy'' test track like Santa Pod. 

Shut the front door!  Tickle my tits and call me Tracy!  Blow me down with a feather! etc etc etc 

[Field Marshal Dr. Opti]

Completely fair point Nick.

I therefore conclude I need to lay this to bed until I can get my grubby paw(s) on some proper timing equipment at a ''grippy'' test track like Santa Pod. 

Traction shouldn't be a problem.

[biggriffin]

Completely fair point Nick.

I therefore conclude I need to lay this to bed until I can get my grubby paw(s) on some proper timing equipment at a ''grippy'' test track like Santa Pod. 

Traction shouldn't be a problem.

just need the right amount !

[Diamond Black Geezer]

....
4.) the info on original Vauxhall testing is flawed: the current boss (had personal reply  ) says they add on 200kg to the kerb weight including the driver. however ian coomber (importantly head of Vauxhall when the omega was launched) SURMISED that the car would be tested with driver and low fuel to improve figures....if thiss the case my initial testing is good!

Ahh! glad you got in touch with him, very nice chap when I've spoken to him. He's passionate about the brand 

[Webby the Bear]

Yeah, really nice chap, DBG. Thanks for letting me know his details 

So, as I mentioned, i'll borrow (assuming that's still ok) Nick's accelerometer and get to the track when I can (though obviously weather's against us now).

In the mean time, let's assume it's down on power for the purposes of the discussion. I've proved the engine's working at it's best. Could wear in the transmission cause poor acceleration. if so can someone explain how?

 

[Andy H]

I cannot remember if yours is auto or manual

If you have a manual box it is probably the time it takes to change gear that would have the biggest impact - by the time I got rid of my old 2.5 it had done over 200,000 miles and the synchro hubs were shagged. Changing gear was a bit of a chore and couldn't be rushed

If you have an auto then wear in the clutch plates will mean that it takes longer for each ratio to engage (because it takes more fluid to up the slack) and might result in clutch slip.

[Webby the Bear]

I cannot remember if yours is auto or manual

If you have a manual box it is probably the time it takes to change gear that would have the biggest impact - by the time I got rid of my old 2.5 it had done over 200,000 miles and the synchro hubs were shagged. Changing gear was a bit of a chore and couldn't be rushed

If you have an auto then wear in the clutch plates will mean that it takes longer for each ratio to engage (because it takes more fluid to up the slack) and might result in clutch slip.

Thanks Andy.

It's auto with the AR25 box 

Will wear in the clutch plates affect acceleration through the Rev range or is this solely an issue when it physically changes gear? And could this account for a good second of acceleration time on a 0-60? 

History of the box is that it's never had an oil or filter drain, there is some leakage from the pinion seal at the rear but I did check the level last year and it hasn't lost hardly any (despite the mess on the outside. . . Though I presume that's dos the prop shaft would spin it all around and make it look bad 

[Webby the Bear]

I cannot remember if yours is auto or manual

If you have a manual box it is probably the time it takes to change gear that would have the biggest impact - by the time I got rid of my old 2.5 it had done over 200,000 miles and the synchro hubs were shagged. Changing gear was a bit of a chore and couldn't be rushed

If you have an auto then wear in the clutch plates will mean that it takes longer for each ratio to engage (because it takes more fluid to up the slack) and might result in clutch slip.

Thanks Andy.

It's auto with the AR25 box 

Will wear in the clutch plates affect acceleration through the Rev range or is this solely an issue when it physically changes gear? And could this account for a good second of acceleration time on a 0-60? 

History of the box is that it's never had an oil or filter drain, there is some leakage from the pinion seal at the rear but I did check the level last year and it hasn't lost hardly any (despite the mess on the outside. . . Though I presume that's dos the prop shaft would spin it all around and make it look bad 

Also. Just to add to some info on the box. . . When I'm cruising I'll floor it (in sport) and sometimes it will kick down, drop a cog and give that satisfying loin girding and then fly off. . . Other times it will stay in the gear and simply rise in revs.... Very unsatisfying! Is that normal auto box operation? Or should it kick down every time I demand full acceleration?

[05omegav6]

Kickdown depends on certain conditions being met... throttle position/RPM/current gear/Road speed etc

To be certain of it kicking down... Lift off the throttle completely then instantly bury the pedal again...

Should force it down to second everytime

[biggriffin]

Kickdown depends on certain conditions being met... throttle position/RPM/current gear/Road speed etc

To be certain of it kicking down... Lift off the throttle completely then instantly bury the pedal again...

Should force it down to second everytime

Bah. Just launch in S mode foot on tut floor.

[05omegav6]

S button merely changes the shift criteria

[Webby the Bear]

so the fact that it doesn't always kick down (I'd say most of the time it does) even if I floor it in sport, that is normal operation?

So coming back to the original question. .  .

The possible wear in the tranny could cause acceleration loss?