Date: Mon, 10 Feb 2003 06:46:30 -0000 From: "DervMan" <dervmannopsamail.com> Subject: Re: Saab 93 Sports Saloon 2.2 Tid
"Johannes H Andersen" <johsnopsamsizefitterzzzz.com> wrote in message news:3E46ABDA.1A133BC0nopsamsizefitterzzzz.com... > DervMan wrote: > > > [...] > > > > > > I'm not much for diesels; my 9000 CSE 2.0 LPT will do over 40 mpg on > > motorway > > > driving if I don't drive like crazy. > > > > There's a lot more to it than just plumbing along at a constant speed on the > > motorway. Diesels don't run a richer fuel mixture when cold, so there's a > > saving here (note that many run the engine a little quicker, but this is to > > make it smoother - they don't need to in order to run, and it's simply > > effectively holding the "throttle" open rather than running a richer > > mixture). > > > > I've returned over 50 mpg from these size of cars, but their older cousins - > > the first generation Mondeo TD, for example, and our fleet's 406 and Laguna > > (indirect injection engines) would also return 47 - 53 mpg on a motorway > > run. That's 25% more efficient than their petrol brethern. > > The noise level at motorway driving is of utmost importance to me; I couldn't > live with a noisy car. I sometimes drive two hours a day on motorways and any > excessive noise wear me down. Luckily this old 9000 2.0 LPT has high gearing > about 25 mph/1000 rpm while newer cars oddly have faster gearing of 20-22 > rpm/1000 rpm, this can be quite frustrating since you often hear a drone at > 70 mph. At motorway speeds, the highest source of noise is rarely the engine - indeed, wind and tyre noise are bugbears in most cars. Small cars suffer more from wind noise, larger cars from engine noise, as a rule of thumb. Sound insulation seems to be better at removing lower frequencies than higher, and diesel engine noise tends to be at a lower frequency than petrol engines . . . which is why many diesels are relatively (or discretely) quieter at a motorway cruise. Then you add in gearing, although many manufacturers have an alarming trait of using long gearing for all versions, which traditionally has been higher in the diesel version. > > > Anyway, the first I would look for in a > > > diesel is differences in noise and vibration since this is the main > > bugbear > > > and where I expect the technology is advancing. > > > > It's advancing across the whole spectrum, though. > > Petrols are also advancing. Wonder what happened to the Saab SVC engine? > Was there a noise/vibration problem? Agreed; diesels are merely playing catch-up for all the advances in petrol engines. -- The DervMan www.dervman.com
