torqe /power

That's hardly better than my seven year old diesel which can do 0-84 mph in third gear. However, I usually 'want' to start off in 1st rather than 3rd because I have a little mechanical sympathy.

Exactly!

Am I really reading this from you..?

Inadequate for motor journos... Unfortunately manufacturers take account of that and equip cars with ridiculous low mph/1000rpm which can be very annoying for motorway driving, even at 70.

Remind me again how many rounds of the BTCC the diesel Seat won?

Remond me again what set the fastest lap and won the 2008 Le Mans 24hr? Oh yeah, an Audi TDI.

Where are the petrol engined lorries producing 2000lb/ft torque?

Yeah, but diesels are still unpleasant.

Probably North America.

The stench of petrol is foul and offensive.

Diesel, on the other hand, has a lovely scent.

And they all had as much *power* as their contemporary non-diesel opponents.

If they were, they'd not need 20+ gears to move a piddly 32 tonnes.

Beats me but as petrol engines run faster they don't need torque at flywheel, the gear box multiplies the torque. Wheel speed at 56mph

Fact is you don't need 450+bhp to haul 40tons at 56mph. You do need power to accelerate that load to 55mph. The accountant isn't too bothered about your driving enjoyment or transient performance. Because fuel efficiency of un-throttled TD is better than petrol at the part load cruise where most trucks spend most time the accountant buys you a TD. TD has low exhaust temps at 56mph cruise giving good turbo and exhaust valve life.

The market resistance to petrol turbos in USA is huge. Turbo petrol has higher exhaust temps, this led to a very bad reputation for short turbo life in commercial use and also in domestic cars. Water cooled turbos didn't arrive until the mid 80's with the series 2 Ford RST and R5 turbo but by then the USA market had decided that turbos were a useless device on petrol engines and bigger inefficient N/A engines were better (for cars). Water cooling of turbos is so badly understood as the definite fix for short turbo life on petrol engines that some idiots (AKA "professional tuners") are quite willing to remove the water cooling from the turbo on the grounds that it overloads the cooling system and causes "engine overheating". Exhaust temp also makes production of VNT for petrol engines a challenge.

SAD very SAD.

Oh yeah the LM rules are bent very much in favour of Diesels. Size of engine 5.5L TD v's 4L petrol turbo, size of hole in restrictor, permitted boost, number of turbos (LMP2 class petrol not allowed sequential or compound), VNT. Once they put different restrictions on classes or by fuel type using artificial limiters like different engine sizes, fuel tank sizes, inlet orifices and don't have totally open simple one engine size rule then it's easy to get it so wrong that unworthy crap can dominate. The limitations have stifled innovation and will not give car makers any useful input to future engine designs so they don't compete. They limit performance very close to "best" production and thus are not a worthy challenge for any engineer. Petrol 650bhp/4L is 162bhp/L, best production turbo is running 140bhp/L. Diesel 650bhp/5.5L is 118.2bhp/L and ALFA/GM TTiD is making over 90bhp/L. 160bhp/L petrol turbo is result of simple "bolt on" mods to a production engine, BSR claim "chipping" TTiD will yield

Then there is budget. It's estimated that if Peugeot the only other large manufacturer racing in LM is removed that Audi spent more than every other LM competitor combined. But the results are piss poor value as regulations prevent Audi engineers being innovators but force them to be plodding formalistic technicians, stepwise refinement is very expensive.

Each engine from JCB Dieselmax is 2.5L inline 4 and makes 750bhp (300bhp/L), makes Audi's 650bhp 5.5L V12 look pretty lame. But the JCB would be excluded from use in LM racing as their engine is TOO SMALL, it runs TOO MUCH boost and it doesn't have the right size intake hole. Would it last 24hours? Who knows but 100bhp "detune" will buy a lot of life.

On second thoughts better limit them to 1L as 2L 1000bhp spark ignition turbo is way too much, a 1L spark ignition engine with no idiot rules could make over 500bhp and have a 24 hour life. A 1L Diesel is unlikely to make much more than 300bhp so they won't be in the results. Compared to Ricardo engineers working on JCB Dieselmax, virtual amateurs are building petrol turbos that make 300bhp/L using production engine blocks and heads but they usually only last minutes. The race teams engineers challenge would be making them last 24hrs, a worthy challenge.

Do they run Olympic sprints by tying the competitors legs together to limit their stride?

Ultimately..there's no denying the truth..

large snippage of bits I agree with

I'd have to differ about petrol turbo engines making that power only lasting minutes. It's not even a particularly high target output for a 16v engine. I did the cylinder heads for a 2L Subaru Impreza last year that now makes 514 bhp on 2 bar of boost, (the porting work added over 100 bhp) still only with the standard cams and valve sizes and with tractability from just over idle. With bigger valves and hotter cams some tractability would be lost but close to 600 bhp could be found without even raising the boost level which at present isn't abnormally high. 800 bhp isn't an unreasonable target with cams, stronger internal bits and more boost. It might not last forever on a track but no race engine ever does but in road use I expect it to run happily for many thousands of miles.

Yes, but the MG will do it with noticeable acceleration right the way through. I have mechanical sympathy, it's not as though I spend my life just putting cars in one gear and leaving 'em there.

I don't hide the fact that I despise 90% of diesel engined vehicles. Diesel is a good fuel if you're exceptionally skint and don't care about refinement or driving pleasure. If you like cars, diesel is not the way to go.

Diesel is fine for trucks. In a truck you can fit a 14 litre V8 and 20 odd gears and pay someone else to drive it.

I don't own a diesel, but have driven my neighbour's newish 535 auto. Fooking brilliant. I'd have one tomorrow if I could afford to.

Good though it is, I don't think there's a current car with equivalent petrol and diesel options where the diesel would be a choice were running costs not important.

Try the twin turbo petrol BMW - it's way better than the twin turbo diesel - all the torque plus it revs out to lots of power too! Even applies to the proper superdiesels (Rangerover Sport V8, Audi A8) - what's the point when the economy plummets anyhow why buy the diesel?