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[feeutfo]

the omega was built the way legislation allowed for at the time  that is a compromise between emissions v consumption and power v weight.

the v6 engine was indeed tuned for a fat and flat torque curve as it is torque that gets a vehicle moving not bhp. 4 pot petrol omegas use more or less fuel as the six pot cos their power is devloped higher up the rev range. 2.0 16 valve is 100kw@5600 and 185nm @ 4000 V 2.5 v6 24 valve 125kw @ 6000 and 227nm @ 3200 3.0 v6 24 valve 155 nm @ 6200 and 270nm @ 3600.

although the outputs stated give the maximum output at the revs stated you need to understand that the 2.0 16 torque curve is steep very little torque below 2000 revs then 110nm rising to 185nm at 4000 back down to100nm by 5000 revs. the v6s by comparison deliver over 180nm from 1600 revs to 5200revs with the peak coming in in the middle of the range.

I shall concentrate on the v6 now. You can gain a higher torque figure for a longer rev range by altering the cam phasing without making the power delivery peaky,by fitting reprofiled cams that are only altered from standard by 8 degrees this still gives a fat and flat torque curve however instead of 180nm between 1600 and 5200 you get 195 nm. not alot more i grant you but enough to lower in gear acceleration by about 1.1 seconds over standard.

I have done quite abit to my 2.5 manual the only thing left to do is the exhaust side of the combustion cycle. I fitted a cold air feed air filter to reduce the temp of the air entring the engine making the air denser therefore  giving a better responce when mixed with fuel and fed in to the engine. i have reprofiled cams to alter the valve times to allow better combustion had head work done on the valves size and shape a remap done while the car was being driven to get rid of flat spots sports cats and stainless cat back exhuast to get the spent gases out quicker lightened flywheel to aid throttle responce.
While i can drive around on a light throttle in town and still get 20 to 22.5 mpg when you start puttin your foot down that dips to 15 to 17 mpg yet while crusing to liverpool at a steady 80 i get 31 or 32 mpg.
I will admit that the cost of the modifactions i have done are not cheap or practical but to me they are worth every penny ive spent.

As for tubular manifolds and/or forced induction the cast iron exhaust manifolds fitted to all mass produced cars are tuned for economy and built for a low price they will always be restrictive it is weather you can afford to or want to change them from standard however i have in the past fitted tubular manifolds to various vauxhall carltons and senators with 3.0 engines and they have only improved performance and sound with no negitive side affects.

hi Dan, interesting stuff,
did you buy these manifolds off the shelf, or have them made? and if, made to what spec.?
cheers

[omegadan67]

Hi Chris
  the manifolds for the carlton/senator where sold by a german tuning company and indeed where "off the shelf" they did do a bespoke manifold/exhaust system for the senator whoever that ment going to germany for 3 days.

The last senator i had back in1992 was a 24 valve 3.0 manual which i tuned to the limit, ported and polished head 285 piper cams veneir pullies alpha weber ignition/injection manifolds from germany exhaust from ashley stainless in leeds rollin road set-up net result was 320 bhp up from 204 and 296 lbs/foot t up from 199

[Albatross]

I'm pursuing this line of questioning elsewhere (ABS) too just to see if I can get any further insight or wisdom. I have had a bit of feedback which concerns me slightly.

can't comment on this particular setup, but I know in many cases those trumpets although look restrictive will actually help airflow at the top end of the rev range and increase power (less air turbulence as the air is directed into the AMM)

Now don't worry too much as this is specifically in reference to the top half "trumpet" and not the bottom half fibrous pipe which was what I believe the Chipped UK man was talking about and that you have already had cut flush in your air-box Steve. The trumpet may be something that we shouldn't be taking out. Noise is nice, but not at the expense of performance.

I rang Chipped UK again today for further clarification, but the technical guru there who originally advised me was "away filming with Top Gear" for the day (How cool is that?). I will call him again tomorrow to find out exactly what his take is on each of the two pipes. He did say "cut the pipe so it is flush and you'll gain horsepower, it is there as a restriction".

The trumpet piece in the top does not need "cutting" so I am guessing at this stage that he was referring to the bottom pipe only given the quote above.

I'll update tomorrow.

OK, an update:

Cut the fibrous pipe out as this has been verified by over 5 discrete sources as being added specifically to restrict air-flow and keep the 3.2 within a certain power tax bracket for company car use. Cutting it flush does increase performance and not noise.

Do not remove the trumpet shaped affair in the top of the air-box as this is needed. Removing it is actually detrimental and caused my car symptoms which reconcile with what I read on a German forum. With the trumpet removed my car would occasionally stall from a warm start as the idle would drop too low.

Will be checking out exhaust mid sections with sports cats now and the benefits (or not) of a balanced cross over and if this is good where should it go for the best balance of torque gains.

Tubular manifolds will be following that shortly, but the jury is out on that one as to whether it will be of much benefit.

I am going to a fully qualified Vx Omega tuning specialist in January (with Dan ^^) who tuned all of the Nottinghamshire plod Omegas who will give me some more insight.

[ngrainqey]

you'll have to let us know what modifications there are and what sort of price we're looking at if neither you or him mind