Fuel Consumption ZX - 2.0i 8-Valve Volcane

Post by **Peter.N.** » 01 Jul 2005, 04:48

I concur with all that has been said but once you are used to driving a diesel, especially at motorway speeds, its hard to tell the difference. The XUD engine has a compression ratio of 21-23/1 but the gaskets usually last around 150k if not boiled. I have just changed my 2.1 td gasket at 122k and thats the shortest life I have had from one.
I have just been reading the spec of the new diesel Jag's, and they reckon you really cant tell the difference!

Chrispy · Post by **Chrispy** » 01 Jul 2005, 13:19

I think the main time you can tell is on cold startup. Diesel clatter is hardest to suppress at this point. The V6 diesel Jag is a good engine, but essentially it's a PSA TDCi which they've managed to redesign into 6 cylinders and upped the capacity to 2.7 litres. I'm sorry, but if you can't tell the difference then you've been driving some really crappy petrols! Hop behind the wheel of a BMW straight 6 (or even a Merc V6) and you'll know what I mean.
Tell you wht did surprise me....I was in a workmate's Mazda 626 2.0 TD yesterday (2000 W reg) and it was as rough as hell. The diesel knock could be felt through the whole car and it totally sounded like a taxi. Ugh! Strange when the PSA XUD engine manages to be very unobtrusive in the passenger cabin and that engine's been around for donkeys years! I think only the Germans have managed to beat the Frecnh at diesels and they're raising the bar well and truly. Even the Honda 2.2 I-CDTi is not as good as it should be from a manufacturer that prides itself on it's engines. BMW have squeezed more BHP per litre from the 320d and it's also quieter and more flexible.

Post by **Peter.N.** » 01 Jul 2005, 13:47

I agree entirely, even the most refined diesels have a slight knock at tickover, but it's getting more diffiult to tell when actually moving, even at low speeds. Listen to a Merc or BMW as its driving past in town. I think a lot of the refinement is due to the way the engines are mounted and insulated. The first really 'refined' diesel I ever drove and owned was the CX and although the engine sounded positivly agricultural at tickover, on the move it was quiet and virtually vibration free, the performance wasn't bad either, for the 1980s and the car itself was a delight to drive. After years of driving Perkins 4/108 powered vehicles it was sheer luxury. The XUD was a terrific leap forward, you could actually put your head under the bonnet without wearing ear protectors!

Paulee · Post by **Paulee** » 04 Jul 2005, 14:56

As a test I have driven my brothers 2004 1.9 TD Veloce Alfa which is chipped to 170 bhp and my other brothers Saab 9000 2.3 LP Turbo which also produces 170 bhp and both cars have similar torque so performance is similar (very quick) The Saab engine never intrudes ,is whisper quiet and swiss watch like.The Alfa is gruff and you can feel the vibration from it especially during hard acceleration plus the drive belt noise on the Alfa is horrendous , but it does around 15 mpg more than the Saab !!!

Chrispy · Post by **Chrispy** » 04 Jul 2005, 21:11

I was reading, and apparently it's much more difficult to suppress diesel knock on direct injection engines than indirect ones. Even now I think for smoothness the XUD takes some beating. Driving about, I can hear Ford Escort TD's over my own engine which just sounds like a gruff petrol! The HDi's I find have liess vibration intruding into the cabin, but they clatter like hell above 3,000 rpm. It's a real wimpy clatter too, rather than the roar of the XUD which sounds much beefier. I think it's to do with the ECU disable the pre-injection above a certain RPM speed to aid performance rather than suppress noise which is the main issue at idle and whilst tootling about.
I just think that PSA could've made both the XUD and the HDi so much better. They both are under powered (even the HDi 110's aren't that flash, needing an ECU flash to up them the 130bhp) and they both seem to ignore modern technology. I mean, why are they all 8v for example (barring the 2.1 which is 12v for some odd reason)? Even GM have 16v head on the DTi engines. And why the hell is there no intercooler on the HDi 90? Isn't that a requirement for turbocharged engines in hot weather? It seems PSA wanted to use better technology but for some reason didn't as the Ford TDCi (a PSA engine) has a 16v head and in 2.0 form whacks out 130+ bhp as standard. This engine was even good enough for Ford to slap in the Jag X type. I think the only thing they did take advantage of is the Piezo injector technology.
As for the Saab engine, with GM owning Saab, aren't the engines essentially Vauxhall DTi's? I know those engines are extremely quiet and punchy on their own even without being common rail.