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[Diamond Black Geezer]

Well familiar with the G Cam route, didn't know about fitting a 3.0 ECU, though? I know that fitting G Cams is basically turning the X25XE it into the Vectra Supertouring engine, at 195bhp... but after several years and Vx... well, basically lying saying The Supertouring had a special remapped ECU, the Vectra boys discovered it is in fact the same ECU as any other 2.5 V6...

so very interested to know if the 3.0 ECU is worth doing. 

[Webby the Bear]

Well, this thread has some really divided opinion. Some say it will iron out flat spots. Others say it won't. And others say it's all rubbish.

I guess the only way is to try it and report back the results.

As for fitting a 3L ECU...is this straight up plug n play? What about this immobiliser thang? Would i have to fit the 3L cams with the 3L ECU? More details please Cem 

[Diamond Black Geezer]

Consensus as I've always known it, Webby, is fit 2 x G cams (you can fit 4, but this loses too much low-down 'grunt' but ok if it's a track day car bounding off the rev limiter all day) and a lighter flywheel helps driveability too. The G cams actually create a bit of a dip in the power (or torque, I forget which, or both) curve which the long plenum is supposed to iron out, so the long plenum is an ideal must if you do the G Cam mod. Finally the dividers, are also worth fitting from the 3.0, too. these are also meant to help with the 'mod'

Welcome for anyone to correct me or add to 

[05omegav6]

Well, this thread has some really divided opinion. Some say it will iron out flat spots. Others say it won't. And others say it's all rubbish.

I guess the only way is to try it and report back the results.

As for fitting a 3L ECU...is this straight up plug n play? What about this immobiliser thang? Would i have to fit the 3L cams with the 3L ECU? More details please Cem 

Webby, if you must scratch this itch, then as an experiment, fit the following from a facelift 3.0...
ECU (with the immobiliser gubbins),
3.0 throttle body (if different),
Long nose plenum,
3.0 inlet manifold (if different-pretty certain these are all the same),
3.0 fuel rail with injectors and fpr (should come attached to manifold ),
3.0 Maf (if different).

You might find it makes sod all difference, in which case swap the cams next time the belt is done and try again, but it will be cheaper than getting it chipped/mapped The 2.6/3.2 intake manifolds are the same as late 3.0, but you might find the 2.5 intakes are slightly smaller. The fuel rail is the same except for the pressure regulator and possibly the injectors, in which case you might be able to use your existing inlet manifold/fuel rail and simply fit the 3.0 fpr.

Failing that, try a 3.2 and buy some new pants

[Webby the Bear]

Thanks Al,

So just to confirm....

Are my 2.5 inlets/injectors the same as a 3.0l? i thought they were... 

[05omegav6]

I don't know, hence all the ifs

They probably are, but I'll not assume so on your behalf

The fpr is a higher pressure on the 3.0 than the 2.5 iirc...

[Webby the Bear]

Thanks Al, got ya

TBH I was thinking about re-doing the cambelt earlier (its been on there 18 months) than scheduled as it has been dowsed in coolant. So may take the opportunity to install those cams.

[Webby the Bear]

...although i have to say i'm still tempted by the chip....

[Webby the Bear]

PPS, if i did want to explore the 3.0 ECU.... this is essentiaslly like remapping.... as it has a different map....?

[05omegav6]

PPS, if i did want to explore the 3.0 ECU.... this is essentiaslly like remapping.... as it has a different map....?

Yup

[Webby the Bear]

...and whats all this immobiliser stuff about? once i get it does it plug n play? and presumably i can get a cheap one off here?

[Diamond Black Geezer]

I think, from what I've read over the years, thought it's not going to be slower, with all the 3.0 bits n bobs, there'll be practically no difference, maybe 5 bhp or some similar nominal figure. And I'm assuming (never assume, of course) that people who've said 'meh fitting them G cams were a waste of time', may not have fitted all the 3.0 gear as listed above, just the cams. I've always seen it as a bit of a 'do one, do all' thing.

As I say I'm not going to say don't do it, and replacing the cams is certainly not a 5 minute job, but in my case when I do the '3 litre mod', as I'll call it, I'll be fitting the cams, too, purely because it means literally taking off all that plenum, fuel rail, dividers etc malarkey twice, otherwise.


EDIT: but I am really interested to see what just changing everything but the cams does do to the performance. Feel free to be my guinea pig, Mr Webby   

[Kevin Wood]

PPS, if i did want to explore the 3.0 ECU.... this is essentiaslly like remapping.... as it has a different map....?

Yup

Well, there was a school of thought that they are actually the same map but I haven't compared them myself.

The thing is, the ECU injects fuel based on the mass air flow into the engine. If the map is for a 3.0 engine, it will still see a smaller mass air flow on a 2.5 and inject fuel accordingly, so it's not like it will be changing the fuelling significantly. (not that more fuel will give more power, of course). I would, therefore, expect swapping to a 3.0 ECU to be a total waste of time.

Manufacturers tend to map their engines on the safe side, so normally a tad richer than ideal fuel mixture at full throttle just to ensure it doesn't go lean and burn a valve / piston. The mixture for maximum power on a modern-ish engine with an efficient combustion chamber is actually perilously close to going too lean, and the lambda sensors don't work in this region, so there is no way to ensure the mixture doesn't stray into damage territory. Hence, they play on the safe side.

Ditto with the ignition timing, it may well be more conservative than ideal for reasons of self-preservation. So, try the Superchips, as it might resolve both of these issues, but swapping the ECU for one not even designed for the right engine is a bit hit and miss.

The biggest thing you can do for a 2.5 is to swap the cams, as, IMHO, GM crippled the engine to differentiate it from the 3.0 by fitting mild cams. If that's not enough, get a 3.0 / 3.2.

[Webby the Bear]

Thanks Kev,

So just to get this correct in my own mind.... fitting a 3.0l ECU is an absolute waste of time. But it's possible that the Superchips one could be an improvement.

Just re-reading your post... by remapping with a superchips am i getting in to danger territory do you think?

[Kevin Wood]

You're removing some of the margins the manufacturer designed in, that's what all modifications do, but enough people have been using them on here that we can be pretty sure it won't cause a problem.