Omega Owners Forum
Chat Area => General Car Chat => Topic started by: Diamond Black Geezer on 06 September 2016, 16:25:23
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Lots has been spoken about taking various versions of the V6 but I've been looking at the internal dimensions and got wondering if it would be possible, by using the crankshaft and/or conrods from a 3-litre in a 2.5 (whichever alters the stroke) and making another 'Dr Frankenstein's Monster' of the 2.5 8)
Because...
X25XE = 81.6 mm bore 79.6 mm stroke
X30XE = 86 mm bore 85mm stroke
Y32SE = 87.5 mm bore 88mm stroke
The displacement would be increased from 2498cc to ...
3.0 crank/conrods = 2668cc
3.2 crank/conrods = 2762cc
for the purposes of this I'm asking no-one chip in with 'it's not worth it, just buy a 3-litre' etc, because I'm theorising, only. Certainly not the time or resources to do it! :) Just a bit of engineering fun. The road of 'what can you swap between the V6s?' is a well-trodden one, It just occurred to me that I don't recall anyone mentioning this particular change. :)
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Changing the crank is an effective way of 'stroking' an engine... A commonish mod on the Ford Cologne lump... Took the 2.8 to 3.7, with a useful increase in oomph.
Hypothetically, a 3.2 crank, in a 2.5 block with ported 2.6 heads, 3.2 manifolds, 3.0 injectors, throttle body, inlet and chipped 3.0 ecu with sports cats ought to shift...
Whether it would keep a manual 3.2 driven with no mechanical sympathy honest, or not, is anyone's guess... :-\
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Wasn't changing crank/rods the way they took the straight six 3l motor up to 3.6l for the LC?
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There's a load of other things you might need to consider before you create combinations that actually work: piston deck height, conrod length, compression heights, etc etc. The usual reason for doing this sort of job is to create combinations tailored to specific competition classes. So by fitting a shorter stoke crank in a big bore engine you could build a similar capacity engine that revs better - big bore means the potential for bigger valves and better topend breathing, combined with a shorter stroke crank that is less likely to break at those revs. Some of the famous engine capacities are a result of such parts matching: 302 and 327 Chevys, 340 Mopars, 1293 Minis, 1700 Crossflows, 2.1 Pintos and 2.0l Avenger engines(both of which use the 2.8 Cologne V6 piston) etc etc.
The other thing to bear in mind for your X27XE( ;) ) engine is you need access to both the big and small engines to build one. It would need to be noticeably 'better' - different is probably more likely - than an X32XE to be worthwhile.
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Pretty sure Daz combined a 3.0 bottom end with a 2.6 top end for some reason
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All interesting, and very helpful info, thanks, all.
Maybe some of this comes about from the 2.5 being 'tunable' whereas the 3.0/3.2 you can't fit the high-lift cams from the 'bigger engine' - because it already is the bigger engine, etc. :) Actually, may I ask why do you say ported 2.6 heads, Gollum? As far as I was aware the 'Y' engines have a lower compression ratio, so to pop one of them on a 'X' engine would actually cut power a chunk. Not nitpicking, just curious :y
Oh, and does anyone know whether it's crank and conrods, or just one, or the other to 'stroke' the engine, in this case? See to recall 3.0 cranks are 'stronger' though I'm not sure what the metallurgical difference is between 2.5 and 3.0? :)
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Swapping the cams is done because it's reasonably good value for the increase.
You can buy aftermarket performance cams, but you'll easily spend ten times as much on them. Tuning modern engines is an expensive business for small gains.
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Found on a Vectra forum that the actual engine they benchtested and got the '195bhp' on ST200 and GSi was actually fitted with Piper cams (or was it Courtney, anyway) but the 3.litre Omega cams being about 99% the same were actually fitted on the production line, presumably meaning Vauxhall could simply dip into a parts bin, rather than purchase hundreds of specially-made cams from an independent company. Actual GSi / ST200s are menat to be 192bhp because of this. And then we get into that no two engines are the same anyway. Some might do 200bhp, some might do 180bhp and so on...
As you say, gets expensive for very little gains. Actually hence why I'm shopping in the GM parts bin, so to speak. Get in at the right person and the right time and the price advantages are obvious.
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Actually, may I ask why do you say ported 2.6 heads, Gollum? As far as I was aware the 'Y' engines have a lower compression ratio, so to pop one of them on a 'X' engine would actually cut power a chunk. Not nitpicking, just curious :y
The lower compression on the 2,6 and 3,2 is achieved by the dishes in the top of the Pistons, the heads don't play a part in lowering compression.
A late 2.5 x25xe head will be the same as a 2,6 y26se Head and is interchangeable. Same applies to a late 3.0 head is interchangeable with any 3,2 y32se
By fitting a 2,5 head to a 3.0, for example, this will increase compression due to the leaser volume of the valve area
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Pretty sure Daz combined a 3.0 bottom end with a 2.6 top end for some reason
The car started off as a 2.6 FL
He dropped the 3.0 engine and cats in. Fitted the 2.6's exhaust manifolds and kept the top bit for the ecu / dbw throttle iirc.
Engine came from "Vader" iirc :-* :'( :'( :'(
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You can actually fit an early 2.5 head to a late 2.6. It will run fine but is considered a bodge as there are no bolt holes for the coil packs on early heads
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Just drop a 3ltr long nosed engine c/w 2.6 / 3.2 manifolds and a proper gearbox.
Keep the 3.9 diff from your automatic then LPG the lot :y
I've just done Skeg Vegas last week in the Mv6 and had a mixture of town work, sensible driving and :-X :D driving when the dog wasn't in the back.
Filled up yesterday and using the fill to fill method, I got 21mpg @ 51.7 pence a litre :)
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A 300hp V6 shouldn't be too hard to build. Use a 3.2 block, crank and rods, with custom pistons. Some properly developed heads will be expensive, but necessary. Sticking your finger down a port isn't development! Custom ground cams to suit the heads and compression. Vernier pulleys to time the cams properly, which will be time consuming. Jenvey do a manifold for six throttle bodies, so I'd use that with an aftermarket ECU. Add some designed headers.
Sounds good to me, until you see a rough cost: I doubt you would see any change from £10k. When a 2.2 Astra turbo engine is a simple bolt-in and 350hp needs little more than a bigger turbo, it's never going to happen.
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More good info - never considered the lower CR was down to the pistons, that's worth knowing
To Nick, indeed. And it's always baffling when you see people sticking the V6 in Astras etc (I even saw one guy fitted a X25XE to a Frod KA!) when the power isn't really much, it's a big old lump, vs a 4-pot, and as you say, there's surely more compact and tuneable engines out there.
Tiger's - we know that The Devil's fuel is Diesel, but surely Judas Iscariot used LPG? ;) I like the sound of the rest, though, I've got the long nose plenum and G cams and now 2.6 manifolds.
Which is it that has sodium exhaust valves? the 3.0 if memory serves, or was it all the Y engines? Also why do I want sodium on my valves? ;D
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More good info - never considered the lower CR was down to the pistons, that's worth knowing
To Nick, indeed. And it's always baffling when you see people sticking the V6 in Astras etc (I even saw one guy fitted a X25XE to a Frod KA!) when the power isn't really much, it's a big old lump, vs a 4-pot, and as you say, there's surely more compact and tuneable engines out there.
Tiger's - we know that The Devil's fuel is Diesel, but surely Judas Iscariot used LPG? ;) I like the sound of the rest, though, I've got the long nose plenum and G cams and now 2.6 manifolds.
Which is it that has sodium exhaust valves? the 3.0 if memory serves, or was it all the Y engines? Also why do I want sodium on my valves? ;D
For cooling, in my youth training on Merlin and Centaurus engines, IIRC sodium filled valves were used somewhere, clearly not Centaurus, which were sleeve valve.
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Also, I'm crying a bit Mr Gonads, as I'm on about that average mpg from my little economical 2.5 versus your beefy 3.2...in fact did a brim test to compare what the trip comp says vs. real, and found it basically spot on, so that's good.
It's a tantalising thought, a X27XE, as Nick quite rightly calls it :y
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Shackeng, Your training sounds a damn sight more interesting than mine!!!
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Shackeng, Your training sounds a damn sight more interesting than mine!!!
It was certainly interesting looking back from here! :y
In the years I spent as a fitter before aviating, I worked on Merlins, Derwents, Hercules, Centaurus, & Cheetahs amongst others. :y
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Chatting to an old boy and good friend who started in the RAF in the very late 40s (sadly no longer with us as of this year) he told me had a fabulous time. New Jets, new engines, new technology, new electrics, new systems, he really, really enjoyed his time and it was a great decade of invention and innovation. (as most on here will be aware we had the largest auto and aero industry in the world in the 50s)
That's something I'd adore doing one day, be part of renovation projects for the BBMF, Shuttleworth, etc... can't think of anythign better than mucking around on old engines and other mechanics all day, then one day in a few years, seeing the thing take flight, preseving our heritage for another generation. Apologies for the twee and sloppy tone, but it's true :)
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So.....from the stock GM parts bin.
3.2 inlet with injectors or fit 3.0 and the FPR from a 2.6/3.2 (slight increased rail pressure, worth having as it costs nothing)
3.2/3.0 inlet divider plate
2.5/2.6 heads which must be ported to match the inlet divider (2.5/2.6 heads have smaller ports than the 3.0/3.2) and 3.0/3.2 exhaust valves (sodium filled)
3.0 cams
3.2 bottom end
2.6/3.2 exhaust manifolds
2.5/3.0 front pipes and cats
3.0 electronics including DIS pack ecu etc with EGR blanked/removed and SAI removed
This gives the better injection setup (3.0), largest cc (3.2 which includes forged crank) with compression ratio restored (2.5/2.6 heads have a smaller combustion chamber), best flowing inlet and exhaust setup.
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So.....from the stock GM parts bin.
3.2 inlet with injectors or fit 3.0 and the FPR from a 2.6/3.2 (slight increased rail pressure, worth having as it costs nothing)
3.2/3.0 inlet divider plate
2.5/2.6 heads which must be ported to match the inlet divider (2.5/2.6 heads have smaller ports than the 3.0/3.2) and 3.0/3.2 exhaust valves (sodium filled)
3.0 cams
3.2 bottom end
2.6/3.2 exhaust manifolds
2.5/3.0 front pipes and cats
3.0 electronics including DIS pack ecu etc with EGR blanked/removed and SAI removed
This gives the better injection setup (3.0), largest cc (3.2 which includes forged crank) with compression ratio restored (2.5/2.6 heads have a smaller combustion chamber), best flowing inlet and exhaust setup.
Looks like i'm just around the corner from your gaff (Keyworth) from tomorrow after all ::)
I'll drop you 50 quid off and i'll expect it ready by Monday night when I finish :P ;D ;D
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Also, I'm crying a bit Mr Gonads, as I'm on about that average mpg from my little economical 2.5 versus your beefy 3.2...in fact did a brim test to compare what the trip comp says vs. real, and found it basically spot on, so that's good.
It's a tantalising thought, a X27XE, as Nick quite rightly calls it :y
Lpg is great if you can live without a little boot space and want to make a Omega usable for mere mortals wallets on a day to day basis :y
At the end of the day, you can fantasise and spend thousands on this, that and the other and its still a 15 + year old Vauxhall saloon car which will rot away sooner than later :(
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This is it, do you treat your car as day-to-day transport, or a hobby, or even classic car? All have different criteria and budgets... and breaking points!