A meanignful discussion on Diesel Vs Petrol

[Mark]

Performance Diesel Vs VXR8

Well it made me laugh, but that in itself is no particular achievement:shy:

 

[Phil]

Mark:
Neat video. I have seen the diesels in large trucks undergo a major revolution in the last 15 years or so with the introduction of computer controls.
The technology has trickled down to mid size trucks, then pickups, now performance engined vehicles. Just watching LeMans the last few years saw the diesels totally dominate.
I remember not too long ago, 70's & early 80's, the large diesels were mostly under 300 hp, somewhere in the 700 to 900 cu in displacement range, and got 3 1/2 or if you were lucky 4 mpg.
Engines now run a lot less displacement, most are turbocharged or dual turbo with one feeding the other, intercooled, and run at much lower rpm. It is not uncommon to see ratings like 450 or 500 hp in a 600 cu in motor, with torque in the 1150 to 1200 lbs/ft range. Most engines will pull full torque and horsepower down near 1100 or 1200 rpm, and highway speeds are acheived at 1400 to 1500 rpm.
Everything turns slower with less friction and hp is up with fuel economy in the 7 to 7 1/2 mpg fully loaded.
Variable timing, precise injector control and overhead camshafts have replaced the old designs, and engines are much cleaner running.
These new engines also lend themselves well to dynamic braking, and I have seen wheels almost lock in full mode.
I recently saw an add for the new Ford 6.7 L powerstoke diesel that while pulling a 10,000 lb trailer managed to lite up the rear tires.
The only limiting factor seems to be rpm, as the fuel has a rather long burn duration, but its not needed when proper gearing is used.
Cheers
Phil

 

[Jim Rosenthal]

Right. The word's been out on diesels for performance in marine applications for decades; if you want to go fast on the water, you don't bother with gasoline engines unless you are running a Donzi or a Formula or a Fountain, etc- and even some of those are diesel-powered now. Real boats- boats you can fish offshore with, go places on, etc- all runs diesels.

Oh, and who won Le Mans for the last four or five years? Not gasoline engine cars.

 

[Dalton Veitch]

It's been quite a revolution, hasn't it. When I was young (cue the violins) diesels were big, slow, heavy engines that were basically efficient at constant speed and lasted forever. Applicable for long distance trucking, say. They were built heavy to withstand the compression ratio needed for combustion, which was much higher than a petrol engine, and as a byproduct of this strength and weight they had a long life, but didn't move fast. The lack of electrics meant they would operate underwater on a four wheel drive river crossing, and didn't need black boxes to keep them going. Bullet-proof in the Aussie bush. Now they have got the black boxes, are small, light, efficient, have a better rev range, turbos etc., and are very different. They have gained a lot, but lost their inherent simplicity in the process. My 2c worth.

 

[Keith]

Absoutely right Dalton, they have taken an bullet proof system and made it fragile, but that was bound to happen. They must make fortunes on the sale of spare gizmos.

But, I can still fix my own Trooper - no sensors - no electronics - no black box and nearly 20 years old -with 200,000 on the clock. Funny thing is though, apart from service parts, I have had to change/fix nothing at all, ever, zilch.

Meanwhile my friends (Caterpillar designed engine) all singing black box controlled dual mass flywheeled 35 mpg rocketship has self detonated at least 3 times and is on his second gearbox. All that aggro for just 10 mpg less fuel consumption!

Wouldn't mind at all though if the little black disc shaped thingy with 2 wires coming out of it and who's failure didn't a) put the machine into 'limp' mode and b) cost £300 and take a tech 5 minutes to replace.

 

[TimB]

Right. The word's been out on diesels for performance in marine applications for decades; if you want to go fast on the water, you don't bother with gasoline engines unless you are running a Donzi or a Formula or a Fountain, etc- and even some of those are diesel-powered now. Real boats- boats you can fish offshore with, go places on, etc- all runs diesels.

Oh, and who won Le Mans for the last four or five years? Not gasoline engine cars.

Marine diesels can do that because they don't have to worry about being able to shed all that heat through a radiator. I agree marine is where the performance is but if I tried to apply the same turbos and injectors to my vehicle based detroit diesel it wouldn't last long