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[markrnorton]

What is the limiting factor on internals in order ?

Crank, rods, pistons ?

do these engines expire easily at the limit then ?

[cem_devecioglu]

before everything, these engines are designed to work hot for some emission reasons..  so first issue is cooling..
 
from all models only 3.2 have steel crank .. if you want some serious power gain internals must be changed to forged steel..

[Kevin Wood]

What is the limiting factor on internals in order ?

Crank, rods, pistons ?

do these engines expire easily at the limit then ?

Part of the problem is that not enough people seriously tune them to find out. There's folklore about the bottom ends failing and the rear cylinders overheating when tuned but not enough people have been down that path to build a solid picture, IMHO.

Then you have to consider what type of tuning you are going to go for. Forced induction? Hot cams, ported heads and higher revs? Each will do the job, but with vastly different demands on the bottom end.

Given that the crank is quite a complex shape to accommodate the 54 degree V angle, and the stock rev limit is close to 7K as it is, I'm not sure I'd trust it at higher revs. On the other hand, bottom end problems are not unheard-of on standard cars so how much forced induction will they take?

Answering these questions is free of charge if you pick an engine that has been extensively modified in the past, and potentially very expensive if you are a trailblazer, as you would be with this engine.

Hence the V8 / C20LET conversion tends to be the only serious tuning you see on Omegas.

[horsecow]

Would 3.2 manifolds fit onto my 2.6???

[markrnorton]

What is the limiting factor on internals in order ?

Crank, rods, pistons ?

do these engines expire easily at the limit then ?

Part of the problem is that not enough people seriously tune them to find out. There's folklore about the bottom ends failing and the rear cylinders overheating when tuned but not enough people have been down that path to build a solid picture, IMHO.

Then you have to consider what type of tuning you are going to go for. Forced induction? Hot cams, ported heads and higher revs? Each will do the job, but with vastly different demands on the bottom end.

Given that the crank is quite a complex shape to accommodate the 54 degree V angle, and the stock rev limit is close to 7K as it is, I'm not sure I'd trust it at higher revs. On the other hand, bottom end problems are not unheard-of on standard cars so how much forced induction will they take?

Answering these questions is free of charge if you pick an engine that has been extensively modified in the past, and potentially very expensive if you are a trailblazer, as you would be with this engine.

Hence the V8 / C20LET conversion tends to be the only serious tuning you see on Omegas.

Thanks for the response
my 2.5 is going in a kit car, so ultimate power is not really an issue. i believe the 2.5 can be tuned to circa 200hp in NA form
I am/have in the past supercharged and turbo'd alot of engines. I was thinking about a low pressure set-up on this engine eventually.
I will put up a build thread soon, as i am using alot of Omega donor parts (these are having to be modified to suit the car)

sorry to hi-jack the thread

[Kevin Wood]

Thanks for the response
my 2.5 is going in a kit car, so ultimate power is not really an issue. i believe the 2.5 can be tuned to circa 200hp in NA form
I am/have in the past supercharged and turbo'd alot of engines. I was thinking about a low pressure set-up on this engine eventually.
I will put up a build thread soon, as i am using alot of Omega donor parts (these are having to be modified to suit the car)

sorry to hi-jack the thread

Well, 3.0 cams would be a no-brainer for your application. It's a proven mod that is reliable and any small lack of low-down torque in exchange for top-end power will not be a problem in a light car.

Next on the list would be exhaust manifolds. Get some tubular headers made up rather than the standard manifolds.

Then it comes to engine management. If staying with the standard ECU you probably want to use as much of the standard induction setup as you can fit under the bonnet. In standard tune the multiram setup is worth maintaining as it'll improve low down torque.

If going for an aftermarket mappable ECU you are more flexible. Ditch the MAF and multirams, etc. and duct air straight into your throttle bodies, keeping it as cold as you can then use a speed density map so you use a MAP sensor to measure load.

Ultimately, you could go for individual throttle bodies - 2nd hand bike throttle bodies with a bit of fabrication or these if you have deep pockets: http://www.jenvey.co.uk/home/standard-kits/jenvey-dynamics/opel-vx-v6-sfs45-kit-ckvx06 . You might want to consider porting the heads and some hot cams if going this far, and, for that matter, whether it wouldn't be more sensible to swap to a 3.0 engine and get most of the power for free before spending a lot tuning a 2.5.

Good luck with the project anyway, and keep us updated.

[cem_devecioglu]

Thanks for the response
my 2.5 is going in a kit car, so ultimate power is not really an issue. i believe the 2.5 can be tuned to circa 200hp in NA form
I am/have in the past supercharged and turbo'd alot of engines. I was thinking about a low pressure set-up on this engine eventually.
I will put up a build thread soon, as i am using alot of Omega donor parts (these are having to be modified to suit the car)

sorry to hi-jack the thread

Well, 3.0 cams would be a no-brainer for your application. It's a proven mod that is reliable and any small lack of low-down torque in exchange for top-end power will not be a problem in a light car.

Next on the list would be exhaust manifolds. Get some tubular headers made up rather than the standard manifolds.

Then it comes to engine management. If staying with the standard ECU you probably want to use as much of the standard induction setup as you can fit under the bonnet. In standard tune the multiram setup is worth maintaining as it'll improve low down torque.

If going for an aftermarket mappable ECU you are more flexible. Ditch the MAF and multirams, etc. and duct air straight into your throttle bodies, keeping it as cold as you can then use a speed density map so you use a MAP sensor to measure load.

Ultimately, you could go for individual throttle bodies - 2nd hand bike throttle bodies with a bit of fabrication or these if you have deep pockets: http://www.jenvey.co.uk/home/standard-kits/jenvey-dynamics/opel-vx-v6-sfs45-kit-ckvx06 . You might want to consider porting the heads and some hot cams if going this far, and, for that matter, whether it wouldn't be more sensible to swap to a 3.0 engine and get most of the power for free before spending a lot tuning a 2.5.

Good luck with the project anyway, and keep us updated.

[markrnorton]

i want to retain the 2.5

outline would be
Omex or Emerald engine management
Exhaust mainfolds have to be fabricated to fit in the side pods, so would be tubular
map sensor/alpha N - no maf
cold air feed/intake and retain duel intake
lightweight underdrive front pulley
loose the power steering and ac pumps, smaller belt/jockey wheels
lightweight flywheel
3.0 inlet cams

[Kevin Wood]

i want to retain the 2.5

outline would be
Omex or Emerald engine management
Exhaust mainfolds have to be fabricated to fit in the side pods, so would be tubular
map sensor/alpha N - no maf
cold air feed/intake and retain duel intake
lightweight underdrive front pulley
loose the power steering and ac pumps, smaller belt/jockey wheels
lightweight flywheel
3.0 inlet cams

oh, yes. As you said on the previous page, in fact.

That setup ought to be good for 200 BHP, IMHO.

[jtypecav]

98' Omega 3.0 happily alive and running in the Ascona - best engine I've ever had. On Cavalier 2.5 management was rr'd at 254bhp (255 last year so close enough) and that was a different place. Ditching cast manifold and going custom made a huge difference. The later ones are an improvement, but still hold it back. Being a 30 year old car it also has no opportunity to take advantage of dual ram or even any other air box system and runs flawlessly on a cone. I'd never dream of doing that to the MV6 though - I think the MK2 is so much more exposed to the elements which is where the problems start.

Also - whilst I agree with the "global corporation" designs such and such.. (e.g. always fitting an oil cooler to an XE or SEH Cav as GM did - even though they discarded them on later models - mummy knows best!) But mummy also wants to make a quiet, refined, compromised (but still fantastic) jack of all trades luxury barge. If you forgo refinement there is ALWAYS more power. It's just not that suited to an OMG.

Incidentally live data was really illuminating from the ascona X30XE. Now my gold F/L MV6 will be looking for a new home and I jump on the train to head up North to collect it's replacement I can't wait to see the difference between pre-fly-by-wire X30 to Y26SE'ness!

Friend added full set of 3.0 cams and got 7bhp. I did it on a cavalier 2.5 (pre and post a rr'd and got 10) so if it ever needs any significant work although I'm keeping it standard I'll be seriously tempted to chuck them in again!

[markrnorton]

98' Omega 3.0 happily alive and running in the Ascona - best engine I've ever had. On Cavalier 2.5 management was rr'd at 254bhp (255 last year so close enough) and that was a different place. Ditching cast manifold and going custom made a huge difference. The later ones are an improvement, but still hold it back. Being a 30 year old car it also has no opportunity to take advantage of dual ram or even any other air box system and runs flawlessly on a cone. I'd never dream of doing that to the MV6 though - I think the MK2 is so much more exposed to the elements which is where the problems start.

Also - whilst I agree with the "global corporation" designs such and such.. (e.g. always fitting an oil cooler to an XE or SEH Cav as GM did - even though they discarded them on later models - mummy knows best!) But mummy also wants to make a quiet, refined, compromised (but still fantastic) jack of all trades luxury barge. If you forgo refinement there is ALWAYS more power. It's just not that suited to an OMG.

Incidentally live data was really illuminating from the ascona X30XE. Now my gold F/L MV6 will be looking for a new home and I jump on the train to head up North to collect it's replacement I can't wait to see the difference between pre-fly-by-wire X30 to Y26SE'ness!

Friend added full set of 3.0 cams and got 7bhp. I did it on a cavalier 2.5 (pre and post a rr'd and got 10) so if it ever needs any significant work although I'm keeping it standard I'll be seriously tempted to chuck them in again!

when you replace the cams, did you change the followers/tappets for new or just use the old ones ?