Citroen XM Forum

Very interesting stuff Dean. Having enjoyed my manual 12v PRV alot, one thing it's great at is torque from idle. In an auto perhaps it'd go less noticed, but with the manual you could drive very relaxedly. This narrow exhaust port must be a main reason for that -and on the other hand makes that the engine goes out of breath at 5,600rpm. But although torque peaks at 4,600 (if memory serves), in practice you're on a wave of torque from idle -there's no hollow at the low end. The 12v actually produces more torque up to 2,000rpm, than the 24v.

I'd really like to know why the un-matching design of manifold Vs exhaust port! Some developmental mismanagement of some sort at PSA maybe? One scenario I could think of is, they maybe underestimated the yield of the full diameter exhaust ports, but already had had the exhaust manifolds ready to produce, then they say "ok how do we limit that engine to around 170hp? Let's add a restriction to the exhaust flow, then adapt the cam profile, and that's us". So they could clearly differentiate between the purpose of the 12v and 24v targeting "around 200hp". It looks like if this restriction was not there, the 12v could jump to 180hp easily... OR could it be that the exhaust manifols were borrowed from an existing PRV variant, just to limit costs? A mystery!

The exhaust ports are probably restricted to increase gas flow and cylinder scavanging to give torque, as opposed to outright power at high revs only.

Some manufacturers used to get this wrong and throttling the ports actually increased torque and driveability.

Thank you Paul for seeing this through at your end for me, Yog has now landed in Hove ready for her trip to the south island next week, frantic grouting, sealing and painting is currently taking place so i will be available for light tinkering at all available moments.
Citroen xm V6 Donor arrives by Deanxm, on Flickr

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Wow!... Nothing like an incentive!

That is quite some trailer Dean!! With regards, Matthew T.

Yes Matthew, room for two small cars so i understand!
The fruits of my labour over the past 3 years, wait no. Its only been about 4 weeks!

Before
photo(73) by Deanxm, on Flickr
During
photo(66) by Deanxm, on Flickr
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photo(70) by Deanxm, on Flickr

Before
photo(71) by Deanxm, on Flickr
During
photo(68) by Deanxm, on Flickr
During
photo(67) by Deanxm, on Flickr
After
photo(69) by Deanxm, on Flickr
After
photo(65) by Deanxm, on Flickr

Just paint the ceiling then do about 6 dump runs and then freedom!!!!!

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Wow Dean, you have been busy. That's a very impressive bathroom. Nice job. Kitchens and bathrooms are hell to live without but once done, you don't know yourself!

But now the real fun begins...... after the dump runs of course!

it was a right mare doing the bathroom, 3 days we had a tent errected over the manhole cover in the garden with the old toilet pan perched over the endge of said manhole and driving 3 miles to the mil's house for a bath, it was like all the bad bits of camping! Done (ish) now though, the last room in the house too!, really pleased with how it turned out but it has been 7 or so years in the planning.

Now the fun does indeed begin, cant wait to tinker!

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That bathroom is impressive Dean, I hope the missus allows you hours of tinkering after all that hard work!

Dean wrote:it was a right mare doing the bathroom, 3 days we had a tent errected over the manhole cover in the garden with the old toilet pan perched over the endge of said manhole
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LOL. The TOP GEAR boys would have been proud of you.