Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: JueV6 on 12 December 2008, 21:17:54

Title: What's the difference between 2.5 and 3.0????
Post by: JueV6 on 12 December 2008, 21:17:54
Apart from 500cc's

After killing my 3.0, for the sake of a starter motor, (which I had spare) I took out the LPG kit.

I don't wanna take the Super mig off the road at the moment so thought, ok do it bit by bit.

So today i decided to swap the inlet manifold and plenom over.
Off with the 2.5 plenom and inlet and on with the 3.0 inlet. then the plenom ohh poo the hose from the coolant bridge was too short. off with the plenom and the skuttle panel. 3.0 pipe fitted, jobs a goodun', NOT.

cruise cable is too short, so changed that to 3.0 and then the throttle cable. OK now see what happens.

Turn the key and 3000 revs
unplug the ICV and 700 revs, Change the ICV and it was the same.
unplug it and 700 revs.

Off to pick Helen,  from town and guess what, IT WON'T CHANGE GEAR. 1st the 2nd thats it.

Spoke to TB and he couldn't throw any light on the problem.

OK put the 2.5 Plenom back on together withe the 2.5 cruise and throttle cables. boxed it all back together and it's like nothing had been changed. she runs like a dream.

Tank / Filler and Pipework tomorrow

SO..... whats the difference between the 2.5 and 3.0 apart from the physical size of the plenom and the kick down on the throttle cable.

TIA
Julian

PS. I didn't use the 2.5 plenom to start with because the 3.0 one already has the vacuum pipes drilled and tapped with the nozzles.

Title: Re: What's the difference between 2.5 and 3.0????
Post by: iainb on 12 December 2008, 21:55:41
The ECU map is totaly different.
There was a guy in Germany selling chips for 3.0l engines in the 2.5l cars, which meant you didnt have to change the ecu.
As I understand it if you put a 3l engine into a 2.5l it will run lean and burn out
 ::)
Title: Re: What's the difference between 2.5 and 3.0????
Post by: TheBoy on 12 December 2008, 22:18:33
Quote
Apart from 500cc's

After killing my 3.0, for the sake of a starter motor, (which I had spare) I took out the LPG kit.

I don't wanna take the Super mig off the road at the moment so thought, ok do it bit by bit.

So today i decided to swap the inlet manifold and plenom over.
Off with the 2.5 plenom and inlet and on with the 3.0 inlet. then the plenom ohh poo the hose from the coolant bridge was too short. off with the plenom and the skuttle panel. 3.0 pipe fitted, jobs a goodun', NOT.

cruise cable is too short, so changed that to 3.0 and then the throttle cable. OK now see what happens.

Turn the key and 3000 revs
unplug the ICV and 700 revs, Change the ICV and it was the same.
unplug it and 700 revs.

Off to pick Helen,  from town and guess what, IT WON'T CHANGE GEAR. 1st the 2nd thats it.

Spoke to TB and he couldn't throw any light on the problem.

OK put the 2.5 Plenom back on together withe the 2.5 cruise and throttle cables. boxed it all back together and it's like nothing had been changed. she runs like a dream.

Tank / Filler and Pipework tomorrow

SO..... whats the difference between the 2.5 and 3.0 apart from the physical size of the plenom and the kick down on the throttle cable.

TIA
Julian

PS. I didn't use the 2.5 plenom to start with because the 3.0 one already has the vacuum pipes drilled and tapped with the nozzles.

about 40bhp ;D

As said earlier, wondering if tps reads different...  ...thinking about it all evening, thats all I could still come up with.

The smaller plenum is probably better for 2.5 anyway
Title: Re: What's the difference between 2.5 and 3.0????
Post by: TheBoy on 12 December 2008, 22:19:40
Quote
The ECU map is totaly different.
There was a guy in Germany selling chips for 3.0l engines in the 2.5l cars, which meant you didnt have to change the ecu.
As I understand it if you put a 3l engine into a 2.5l it will run lean and burn out
 ::)
Not sure the programmed map is different...
Title: Re: What's the difference between 2.5 and 3.0????
Post by: damon80 on 12 December 2008, 23:36:35
Would you not be able to switch ECU's to test, or would it be too much of a ball-ache?  Because I'd also assume that you'd need to switch the immobiliser transponder over from the key too...  :-/
Title: Re: What's the difference between 2.5 and 3.0????
Post by: markey mark on 12 December 2008, 23:47:50
funny this jue i have the same problem on the 2.5 i have fitted a 3.0 with ext plenum !!  :-? :-?
Title: Re: What's the difference between 2.5 and 3.0????
Post by: MutantCav on 13 December 2008, 11:29:31
As I understand it the longer plenum (which is only fitted to 3.0 engines so presumably there is a reason) gives better airflow and higher torque in lower gears...the lower and upper inlets on the 3.0 has bigger holes so presumably so does the plenum as it sits on top of them...cant shed any light on the why for this but hopefully this info might help somehow??
Title: Re: What's the difference between 2.5 and 3.0????
Post by: Kevin Wood on 13 December 2008, 11:47:27
Assuming there were no air leaks with either setup I'm with TB. There must be a difference in the throttle position sensor. This would give a poor engine load reading which is why the autobox was playing up, at a guess. :-/

Whilst there are clearly differences in plenum volume and port diameter these would not affect the engine so fundamentally IMO.

Kevin
Title: Re: What's the difference between 2.5 and 3.0????
Post by: MutantCav on 13 December 2008, 12:06:51
Just a thought (that came to mind when talking about TPS) is the accelerator cable shorter on the 2.5 thus struggling to reach properly to the position on the longer plenum affecting the pull on the TPS??

Could adjusting the little clip help sort this issue?
Title: Re: What's the difference between 2.5 and 3.0????
Post by: Kevin Wood on 13 December 2008, 12:12:26
Quote
Just a thought (that came to mind when talking about TPS) is the accelerator cable shorter on the 2.5 thus struggling to reach properly to the position on the longer plenum affecting the pull on the TPS??

Could adjusting the little clip help sort this issue?

Hmm. that's a point. Could be something odd going on with the kickdown switch too, perhaps, hence the odd gearbox behaviour. :-/

Kevin
Title: Re: What's the difference between 2.5 and 3.0????
Post by: TheBoy on 13 December 2008, 12:56:43
I know JueV6 swapped the throttle cable etc over as well.
Title: Re: What's the difference between 2.5 and 3.0????
Post by: markey mark on 13 December 2008, 13:41:45
im just about to fit 2.5 tps will let you know shortly ! :y
Title: Re: What's the difference between 2.5 and 3.0????
Post by: JueV6 on 13 December 2008, 14:01:52
The car is no sitting with.

X25XE
complete.

But has the X30XE inlet manifold / injectors / Fuel Rail. and any other bits that are connected to the Manifold.

Everything else was changed BACK to the 2.5
Runs perfect

Injectors have the same part numbers and the only difference is the port diameter as far as I can see.

Even The Boy is at a loss.
Title: Re: What's the difference between 2.5 and 3.0????
Post by: TheBoy on 13 December 2008, 14:39:35
epc implies the tps (in fact the entire throttle body) is identical between 2.5 and 3.0, so I'm back to the theory of massive airleak...
Title: Re: What's the difference between 2.5 and 3.0????
Post by: Essex_Andy on 13 December 2008, 14:49:01
I fitted a 3.0 throttle body on to my 2.5 plenum.

I had to fit the 2.5 tps onto the 3.0 body.

Different plug on the 2.5 loom
Title: Re: What's the difference between 2.5 and 3.0????
Post by: Andy B on 13 December 2008, 15:07:09
Quote
Assuming there were no air leaks with either setup I'm with TB. There must be a difference in the throttle position sensor. This would give a poor engine load reading which is why the autobox was playing up, at a guess. :-/

.......
Kevin

I know that if you forget to plug your TPS in then you get a gearbox fault on the display  ::). Mine wouldn't change gear at all though
Title: Re: What's the difference between 2.5 and 3.0????
Post by: markey mark on 13 December 2008, 15:22:50
right tps did no good at all ! its the throttle body thats different ! the tps has the same part number ! the spindle location is at a different postion ! so need to fit 2.5 throttle body to sort it out !! :y :y
Title: Re: What's the difference between 2.5 and 3.0????
Post by: JueV6 on 13 December 2008, 16:04:48
Nice one Marky,