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[minifreek]

I have recently rebuilt the top end of my X25XE and installed 4 x G cams (3.0 cams) a 3.0 litre lower divider, 2.5V6 Vectra Challenge blueprinted heads port matched and knife edged to the 3.0 lower divider built by Swindon racing Engines...

I will be going to a rolling road with another Vauxhall car club and am expecting around 170BHP off a standard X25XE, with me having the 3 litre cams and divider etc.. and the ported heads would i be expecting around the 200BHP mark or just below or more...? I also need to fit a Facet adjustable fuel pressure regulator to help with the fuelling...

Anyone any ideas what i could expect...??

[Martin_1962]

Around 190bhp.

Exhaust manifolds are a big obstruction.

[cem_devecioglu]

Around 190bhp.

Exhaust manifolds are a big obstruction.

agreed..

[Marks DTM Calib]

Yes, to get close to the 200bhp you would need to at least for the manifolds from a the 2.6/3.2 which are imrpoved over the stock 2.5/3.0 ones.

[minifreek]

Would the 2.6/3.2 manifolds fit on the X25 heads...?

I would like to fit tubulars but they are so damn expensive, I know they are probably the best to use but out of my pocket range at the moment... unless I can get the flanges and I'll weld my own up

[cem_devecioglu]

if you want more power, bore to 3.0 or even bigger and use 3.2 crank

[minifreek]

I do want more power BUT i have a limited budget (as we all do) and want to know what 'off the shelf mods' there are for that little bit extra...

I could get a 3.2 and drop that in - for instant power BUT i also need the time to do it, and another car whilst this is off the road etc...

I'll live with what Iv got for now I guess

Which of the fuel lines do I connect the adjustable FPR to... ?

Is it the thicker of the 2 lines..? 1 is 19mm and the other is 17mm, I presume the 17mm is the return..?

[Marks DTM Calib]

Would the 2.6/3.2 manifolds fit on the X25 heads...?

I would like to fit tubulars but they are so damn expensive, I know they are probably the best to use but out of my pocket range at the moment... unless I can get the flanges and I'll weld my own up

Yes but you do have to trim 5mm off the front pipe (not hard)

[minifreek]

I presume the 3.2 manifolds are a bigger bore size...?

When you say you need to trim 5mm off the front, how do you mean please

And do the downpipes etc... just bolt up or do I need to get 3.0 litre downpipes and middle sections etc...?

Sorry for the questions but this Omega and the V6 is a learning curve for me at the moment as Im used to 4 pot engines...

[Entwood]

I do want more power BUT i have a limited budget (as we all do) and want to know what 'off the shelf mods' there are for that little bit extra...

I could get a 3.2 and drop that in - for instant power BUT i also need the time to do it, and another car whilst this is off the road etc...

I'll live with what Iv got for now I guess

Which of the fuel lines do I connect the adjustable FPR to... ?

Is it the thicker of the 2 lines..? 1 is 19mm and the other is 17mm, I presume the 17mm is the return..?

IMHO this is a total waste of time and money ...

Reasons : The combustion cycle is controlled in closed loop by the lambdas telling the ECU what the composition of the exhaust gases is... the ECU then "trims" the fuel to obtain the correct stoichiometric ratio. The fuel "trimming" is done by changing the open time of the fuel injectors. If you up the fuel pressure then for the first minute of closed loop operation you will get more fuel into each cylinder as the injector timing will be for the "old, low" pressure... the lambdas will sense an incorrect fuel/air mix and the ECU will shorten the injector open time to reduce the fuel input ..... hence negating the high fuel pressure... so the standard FPR is as good as any adjustable one .... 

To increase the power by using fuel you need both more fuel AND MORE AIR to maintain the stoichiometric ratio ...... so forced induction of some description ..

Just my thoughts .. nowt else 

[minifreek]

Thanks for that Entwood, I welcome your input and opinion, however, I have found that on my old car, a Vectra B with X20XEV installed, the adjustable FPR produced power.... I removed the original FPR 3.2 bar (?) and replaced with the Facet FPR it went from 135 BHP to just over 141 BHP on standard cams....

The cams where then replaced for FR cams and it then produced 150BHP at standard pressure, with the adjustable FPR it made 159... a good increase.... for not a lot of outlay...

It should have ran 135-139 BHP standard - I was happy with the results...

As to my question, which fuel line do I connect the FPR to....? is it the thick or thin fuel line...

The FPR was taken from a Westfield track car which suffered a lot of damage from impact as was too far gone to repair - unfortunately.... the owner of the Westfield would adjust the FPR from 3.2 Bar for road use and when on track would adjust it to 5 bar, if it didnt work then I dont think he would have bothered with it... he was that kind of bloke..

[Entwood]

Thanks for that Entwood, I welcome your input and opinion, however, I have found that on my old car, a Vectra B with X20XEV installed, the adjustable FPR produced power.... I removed the original FPR 3.2 bar (?) and replaced with the Facet FPR it went from 135 BHP to just over 141 BHP on standard cams....

The cams where then replaced for FR cams and it then produced 150BHP at standard pressure, with the adjustable FPR it made 159... a good increase.... for not a lot of outlay...

It should have ran 135-139 BHP standard - I was happy with the results...

As to my question, which fuel line do I connect the FPR to....? is it the thick or thin fuel line...

The FPR was taken from a Westfield track car which suffered a lot of damage from impact as was too far gone to repair - unfortunately.... the owner of the Westfield would adjust the FPR from 3.2 Bar for road use and when on track would adjust it to 5 bar, if it didnt work then I dont think he would have bothered with it... he was that kind of bloke..

The Westfield probably didn't have a lambda controlled closed loop ECU.....  in which case overfueling could increase power; deliberate overfueling can be used to lower the initial temperature of the charge air, and to prevent overheating of the "burned" charge .... I don't dispute that..... on many cars I have fitted larger jets to carbs to increase the fuel/air ratio ... my point here is quite simple ... on a closed loop lambda/ECU system with full fuel trimming via variable timed injectors it simply won't make any difference without re-mapping the ECU... ..   

[Martin_1962]

I MAY have some 2.6 manifolds avaialble if it dries up this weekend enough to unbolt the exhausts

[minifreek]

Thanks for that Entwood, I welcome your input and opinion, however, I have found that on my old car, a Vectra B with X20XEV installed, the adjustable FPR produced power.... I removed the original FPR 3.2 bar (?) and replaced with the Facet FPR it went from 135 BHP to just over 141 BHP on standard cams....

The cams where then replaced for FR cams and it then produced 150BHP at standard pressure, with the adjustable FPR it made 159... a good increase.... for not a lot of outlay...

It should have ran 135-139 BHP standard - I was happy with the results...

As to my question, which fuel line do I connect the FPR to....? is it the thick or thin fuel line...

The FPR was taken from a Westfield track car which suffered a lot of damage from impact as was too far gone to repair - unfortunately.... the owner of the Westfield would adjust the FPR from 3.2 Bar for road use and when on track would adjust it to 5 bar, if it didnt work then I dont think he would have bothered with it... he was that kind of bloke..

The Westfield probably didn't have a lambda controlled closed loop ECU.....  in which case overfueling could increase power; deliberate overfueling can be used to lower the initial temperature of the charge air, and to prevent overheating of the "burned" charge .... I don't dispute that..... on many cars I have fitted larger jets to carbs to increase the fuel/air ratio ... my point here is quite simple ... on a closed loop lambda/ECU system with full fuel trimming via variable timed injectors it simply won't make any difference without re-mapping the ECU... ..   

OK I understand exactly what you are saying.... the engine was a C20XE.....

[minifreek]

I MAY have some 2.6 manifolds avaialble if it dries up this weekend enough to unbolt the exhausts

Your miles away LOL would cost a fortune to courier them Id have thought...?