hmmm trying to upload the dyno graphs for both engines...will take me a while.
okay done, 2.5td and PRV 12v:
My point, and only point, on the PRV vs. 2.5td comparison, was the responsiveness issue that Dieselman also refers to. Still adamant on that, wont' repeat it...Anything else, *I* did not claim....
I'd like to say that the primary indicator of force is torque. Horsepower is a product measure, showing how often this force is produced. You multiply how many times-per-minute a torque value is produced, and u get horsepower. If some engine does 200bhp at 2,000rpm and another 100bhp at 2,000rpm, it follows that the first produces twice the amount of torque at 2,000rpm at every stroke beat. The talk of "torquey" and "not torquey" engines is a misinterpretation for the general public -with the intention perhaps to distinguish engines to those that produce good hp from low revs by those that only produce good hp after mid-revs and undeperfom below that -as if it's black or white. What u want to know is hp or torque in connection to rpm -knowing just peak hp or peak torque without an rpm reference, is equally useless. At 2,000rpm, the 2.5td produces about 80hp, while the PRV 12v just about 60hp -without looking at the graphs, it follows the 2.5 produces about 33% more torque at 2,000rpm -and that's the max differential advantage noted for the 2.5td. From the graphs, at 4,600rpm, the PRV produces 38% more torque than the 2.5td -and tha's the max advantage recorded for the PRV (what's the limiter for the 2.5td??).
Now, power production-wise, PRV 12v vs. 2.5td:
In absolute terms the PRV 12v produces a peak 23.5mdan of torque and the 2.5td 28.5mdan (+21%).
Remark the coincidence, both the PRV and 2.5td both make 130hp at 4,000. That's the end for the 2.5, while the PRV goes to 170 at 5,600rpm.
Remark the torque of the PRV starting at above 21kg below idle. You DO feel that when driving a manual 12v, makes lazy city driving totally relaxing, impossible to stall the engine.
Remark another coincidence, both meet at 3,500rpm in terms of torque, about 23mdan. 2.5.td has already peaked and is on its way down, while PRV is coming from down and going for peak.
At each rpm below 3,500, the 2.5 makes more hp than the PRV, due to the higher torque.
The 2.5's advantage area is between about 1500 and 3,500rpm. If both had, say, the same exact 5 gears, the 2.5 would be a clear winner in any within-gear acceleration from 1,500 to 3,500rpm. For an in-gear acceleration from 3,500 to 4,300, the PRV wins, thereafter the 2.5td meets its cutter (I guess). It's difficult to say who's the winner in a full-range acceleration from idle to 4,300, depends on how much better one is doing compared to the other in their own respective range of dominance (pro/post 3,500rpm). As there's no sufficient range for the PRV to make a difference (just 800rpm more till 4,300), I'd think the 2.5td would prob win.
All the above doesn't mean anything of course, because gearing is different. Note that the PRV peaks at 5,600rpm and the 2.5 at 4,000, i.e. the PRV has a 40% larger effective rpm range. E.g. this means that to reach the same (desirable) top speed, the PRV can have a 40% shorter gearing in 5fth. E.g. to top at 120mph, the PRV could have a 5th giving 22mph/1,000rpm (22*5.6=120), while the 2.5td needs a 5fth giving 31.25mph/1,000rpm.
Question is: how longer actually is the 2.5's gearing in the case of the XMs? Only this would say which car wins in the various acceleration exercises. The 28.5mdan@2,000rpm of the 2.5td could effectively translate to less force on the wheel than the (30% less) 22mdan@2,000rpm of the V6 if gearing is longer above some threshold. In real life, the PRV 12v has a 5fth that gives 24.2mph/1,000rpm. How's the 2.5's 5fth? Looking at other XMs, I'd assume a top speed of about 128mph at 4,000rpm for the 2.5, then its 5fth should give about 32mph/1,000rpm. This happens to be precisely a 32% longer 5th gear than the PRV; which happens to be precisely the max absolute advantage on torque for the 2.5td (33%). Although the torque differential for the RPV grows somewhat as revs go up (becoming +38% at 4,600, assuming 2.5 can make 4,600; this not meaningful for 5th gear obviously).
Consequently, would all this mean the 2 would score quasi identical in various 5fth gear in-gear accelerations?
Anybody has any acceleration data for the 2.5td? Other gears ratios? I don't.
I'd be very keen on comparing my manual V6 12v with Dj's 2.5td on various tasks, just for the heck of it and to have records, with cameras and timers, it depends on how naughty Dj feels like. The area we live allows for safe testing when everybody else -except for the cows- has gone to bed -it's just dessert. Was planning to do it on my own anyway. Will need to put a new bearing at the NS though.
cheers
George
ps. Anybody fancy putting these 2 graphs one over the other -Andrew the p'shop-guru? The rpm scale difference is quite deceiving.
. Re-reading those lines, I can't believe it's the same Dj I had met, that wrote these things. Somewhere I feel I must have hurt him somehow, but I'm missing something -surely it can't only be the fact I quoted him a couple of times as having said "this is sporty!". Can't be *that* that made for this tone.... 
Especially when anything else I ever wrote, anywhere, was *my* observations, which I still maintain 100% btw, and nothing to do with his person -just with his auto-.
) of your XM collection, or perhaps searching for those elusive headlight washer covers? This is the place to do it.