XM entry at Wikipedia

[Peter.N.]

My last one wasn't, I had to replace the head gasket about 10 times while I had it because of the porous block. It was worth it though, best car I had ever driven.

Peter

[casalingua]

Fascinating digression...any other comments on the "Critical appraisal" section of the Wikipedia entry on the XM? You all own one. What do you make of the wisdom of the automotive scribes?

[marc61]

Yes the CX engine is essentially the same 5 bearing engine that went in the DS from 1966 on, but with a longer stroke, slightly different pistons to get it from 2347cc to 2500cc and it rotated the other way (presumably to stop people fitting CX engines to DSs). The last DS23 with injection made 130hp, the CX25 138bhp. The previous 3 bearing engine on which it was based dates back to the Traction Avant in the mid 1930s! Citroen made something in excess of 2 million DS and Tractions, so the heritage is based on decades of proof, timing chains and relatively easy maintenance.

The cam timing for the CX turbo is very similar to the DS so mechanically it's an under stressed ohv unit. All of which made it an excellent base for turbocharging, but Citroen didn't really push the envelope much and ran only about 8psi boost and dropped the mechanical CR to 7.5:1 with the Turbo 1; then 8psi and 8.5:1 with an intercooler for the Turbo 2. Provided it's run on super unleaded and the intake charge is well cooled, alot more boost is feasible and safe provided the fuelling and ignition map is right, which is what Maikonics figured out by drawing parallels with all the uprated turbo work done with Ford Cosworths at the time.

As Franklin says the standard clutch wont handle 15psi boost for long, mine just slipped and wore out in about 6 weeks which led to the fitment of a Group N clutch with a Citroen centre. It gripped like mad and with the engine, gearbox and driveshafts lasted 7 years in my ownership outputting 250hp.

Marc

[citroenxm]

Actually marc according to the book the "Original Citroen DS" the complete restores guide, the last 23 Efi DS was actually 143bhp because i clearly remember it surprising me that its more bhp then a s1 gti cx (n/a of course) a VERY desireable machine indeed...

[robert_e_smart]

The porus block was only a problem on the CX diesel engines.

[citroenxm]

The porus block was only a problem on the CX diesel engines.

Albeit on later S2 TD2 engines... The TD1 non intercooler lumps were fine..

[Dieselman]

Yes the CX engine is essentially the same 5 bearing engine that went in the DS from 1966 on, but with a longer stroke, slightly different pistons to get it from 2347cc to 2500cc and it rotated the other way (presumably to stop people fitting CX engines to DSs).

I don't think Citroen would give a hoot about people trying to fit a CX engine into a DS. The reason the engine rotated the other way is becasue the DS engine is mounted back to front.

[marc61]

Re the power ratings think there were two bhp values quoted, DIN and SAE, and SAE definitions changed at some point in the 70s or 80s. One is several hp higher than the other. I'm not sure which is which but AFAIK the lower max power value for the 2347cc CX GTi was 128hp, while the 2347cc DS EFi was a tad higher at 130hp, possibly because they backed off the compression ratio a little so the CX would run on slightly lower octane fuel? The 2500cc CX GTi made 138hp, enough to notice, but then they turbocharged it to 168hp which was big improvement. Then the Maikonics transformation took place - warp factor 10 Mr Spock

CX engine rotates opposite way to DS, put it in a D and you get 5 reverse gears!

Marc

[casalingua]

Has anyone read the Citroen XM book from 1989 by Jan P Norbye? There is a test drive of the V6 at the very end of the book. The car shown has no repeater indicator in between the front wheel arch and the front door. Are we to assume that when Norbye tested the car for a 1989 book that he was in fact testing a pre-production model? Similarly, were the cars used in the very early journalist tests real production cars or slightly special pre-production ones? I wonder this because all the early reviews are complimentary about the ride but later reviews are not.

[citroenxm]

but then they turbocharged it to 168hp which was big improvement. Then the Maikonics transformation took place - warp factor 10 Mr Spock


Marc

but before that.. the 168bhp was pre intercooler years and just a small turbo.. then the t2 was a bigger turbo plus an intercooler which resulted in an un publishised 200bhp!!!

Your gonna tell me adding a bigger turbo AND an intercooler will leave the quoted BHP at 168bhp?? I dont really think so?