Diesels can't rev as high not because of weight, but because burning diesel fuel cannot expand as rapidly as gasoline...at high rpms, burning/expanding diesel fuel cannot move as fast as the piston is moving.

 

Okay. Thank you.

 

But diesels have to be geared numerically lower than gas engines, right?

 

[quote=wsalopek]Hmmmm...I disagree...diesels have a LOT of torque, and torque = acceleration.

Horsepower equals acceleration. Because hp indirectly involves gearing while torque does not.

A gas engine may have a narrow band of more torque than a diesel,

Not usually. But the rev range is greater (and that's a huge advantage because you can change the gearing).

but that means it's a poorly designed gas engine

F1 cars and Ferraris have very little low-end torque. Would you tell them that they don't know how to design engines?

...and in any case, if you compare to engines of equal displacement, I think think the turbo-diesel engine will out accelerate the gas engine every time, AND get 30% better mpg's.

Okay. Give me two examples.
.

 

If they make a Mini with a Diesel engine (turbo-diesel), I would most definately by, I'd even plunk down $1k right now as a deposit to be one of the first to get it!

I think performance can be properly engineerined into a diesel engine, take for example the Audi A8 tdi: http://www.edmunds.com/insideline/do...ticleId=108977

I saw an episode of Top Gear where they tested the A8 TDI and could go 0-60 in 5.5 seconds and also easily drove the "saloon" to see what kind of mileage they could stretch it to at 65Mph (if I recall correctly) - they almost got 40MPG!! In that HUGE thing! New technologies for Diesels such as Common rail injection and sequential turbos are doing amazing things in diesel engines. Half of all cars sold in Europe are Diesel, we need to bring that here so the savings can begin.

The governor of Montana is pushing for the US to start refining a Diesel derived from coal (first done by the germans in WII), the amazing thing is that it is totally clear! Between that and ehtanol, our nation could be off the "arab heroin" within a decade, if we were a country with a governmen less corrupt and willing to make short term sacrifices for the sake of our nation and next generation (i.e. not going to happen).

 

then Mercedes will be bringing the E series deisel to the US..... Or so says Motor Trend...

Matt

 

The E320CDI is already here. Maybe you're talking about continuing it or bringing over the European 3.2 (we have the old one).

 

one of the best threads on NAM in the last 2 years.

i agree with most of the comments. i love diesels, we have 2004 tdi that my wife adores, it is not a fast car by any stretch, but beleive it or not 60-100 is very close to my 2006 mk5 gti, uhmmm, at least the stock one before the mods.

it is so true that more than half of the cars in Europe, especially Western Europe are diesels. BMW has a good variety 1.8lt, 2.0lt, 3.0lt and if i am not mistaking 4.0 lt diesels. Audis 3.2 diesel is as fast as the 3.2 petrol motor, and the bigger V8 version is a beast. On the smaller cars, VWs, Peugeots and Citroens lead the market.

europeans are wayyyyyy far on this issue, and honestly we missed the bandwagon, it is pretty late

 

Are you aware that diesel is taxed less than gas in Europe?

 

VW has a prototype car they call Ecoracer. Miata-sized open roadster, it had low 6-second 0-60 times and gets over 65mpg. I have been telling people for years that diesel is the way to go not only for fuel efficiency, but easily tuneable power as well.

One other aspect of diesel power that many overlook (or are not aware of) is that the fuel itself is much 'friendlier'. Unlike gasoline, which is highly volatile and explosive, diesel fuel is far less volatile. You dont have the evaporative emissions to contend with. Place a open cup of both gasoline and diesel fuel out in the open. In a few days, the gasoline will be gone, evaporated into the atmosphere. The diesel fuel will mostly not have budged. Both the car and the fueling station does not need anywhere near the extra equipment needed to handle and dispose of the vapors. Gasoline vapors are a large component of air pollution.

Relating to the above, diesel is much safer to handle and store than gasoline. Spill some gasoline onto a concrete floor and toss a match into it. You will have a rather severe fire on your hands (or actually, on the floor). Do the same with diesel fuel and the match will extinguish itself.

Diesel fuel does not require the same level of refining and added components. This leaves more of the actual energy content in the fuel, which is also another reason for a diesel engine's added efficiency. Pound for pound, diesel has a significantly higher energy content.

A diesel engine has a far greater volumetric efficiency in low or part throttle operating conditions than does a gas engine. unlike a gas engine, a diesel engine does not have a throttle valve. To regulate the speed and power of a gas engine, you have to keep the balance of fuel and air optimized for clean, consistent burning. Throttling a gas engine (which occurs any time that you foot is not stomped to the floor) limits the airflow into the engine. This results in pumping losses (your engine is now a vacuum pump) and incomplete cylinder filling. A cylinder only partially filled with air and fuel often has problems fully burning and utilizing the fuel-air charge. This must be cleaned up afterwards using catalysts and other emissions control devices. In a diesel engine, the cylinder is completely filled with air during all phases of operation, and the engine speed/power is regulated by adjusting only the fuel amount. This, especially coupled with cleaner deisel fuels, helps reduce emissions and does amazing things for fuel economy. If you think about it, how much time does your average street engine spend at part throttle?

Diesel engines respond remarkably to forced induction. Turbocharge a typical diesel engine, and not only will you make more power (because you can also add more fuel too) but your overall efficiency goes up (and with it fuel economy) and emissions decreases during 'part throttle' operation.

So many benefits, so few cars available in the US (still).

 

Europeans never had to put up with CRAPPY Oldsmobile V8's that were converted from gasoline to Diesel.

Had GM given us Diesels that were designed from day one to be a Deisel, things may have been different here in the states. Another thing that the aftermarket has missed, the Import Tuner croud. All of the stuff that go for making more power for the trailer towing croud could have made products for the import VW's and made TONS of proffit. But alas we have high sulfur diesel....

I can only imagine a MINI One TD with water spray on the intercooler and nitrous as well as propane injection. 60 foot drag races anyone?

 

Their E320 CDI does 0-62 MPH is 6.8 sec, 2,987 cc deisel
Their E350 gas does 0-62 MPH in 6.9 sec, 3,498 cc gas

But I was refering to the launch of the new E320 CDI Bluetec....

Matt

 

Here is another little known fact about diesels as well. They respond pretty well to nitrous injection. However, unlike gas motors, where strict attention has to be paid to fuel mixtures and nitrous flow lest you blow your engine up, in a diesel, all you need to do is inject the nitrous into the intake tract. If you 'overspray' the motor, it simply stops producing extra power and starts bogging down. No blowups. It's almost 'self regulating'.

 

I'm pretty sure that gasoline has more energy by weight than diesel, but diesel has more energy by volume (and that's what matters, because fuel is sold by volume).

 

if they do let the td into the us Banks would make that car scream and would be the best sleeper take a look around there page at http://www.bankspower.com/high-performance.cfm

 

check this out, VW has a turbo AND supercharged engine!:
http://www.popsci.com/popsci/automot...cbccdrcrd.html

 

here's the thread.... It has the link.

https://www.northamericanmotoring.co...ad.php?t=61684

Matt

 

Not exactly. Torque is needed to to get the crank, transmission, and wheels to turn. More torque, faster rotation, more acceleration.
But this link also explains why low torque F1 cars acclerate fast.... (if you read between the lines--note the 900hp at 19k rpm)


http://vettenet.org/torquehp.html


I think the best racing series to watch this year will be the American Le Mans series where Audi's new r10 diesel racecar takes on the gassers.

 

Greatbear, are you sure about the throttling of diesel engines? What you describe is much like an Atkin cycle engine where there is no real throttle body. The intake valves remain open for a portion of the compression stroke allowing air to flow out of the cylinder (thus reducing pumping losses) but the exhaust valves remain closed for the entire power strike...basically making an 8:1 compression ratio and a 10:1 expansion ratio.

From what I've seen, a diesel still runs on a modified Otto cycle that has a throttle body. The throttle body is what reduces the light-throttle efficiency of gas (and diesel?) engines.

The fact that diesels have higher compression ratio's than gas engines is why they have more power (torque). This causes the combustion temps to be higher (basic thermodynamics...higher temperature difference = higher power potential). This also is the reason they have more emissions. As the fuel is injected into the compressed air, there are lean and rich parts of the cylinder. Lean causes NOx to form (due to the higher combustion temps) and rich causes hydrocarbons. While newer diesel technology has reduced emissions, the basic nature of the engine means it will produce more than gas engines (while still yielding higher fuel economy).

wsalopek, I also don't quite agree with you on why diesels can't rev. You say that diesel fuel can't burn as fast as gas. Where is this info from? Diesel fuel is heavier and less refined then gas but the actual octane rating of diesel doesn't have to be as high as gas. This is because it's injected directly into the compressed cylinder and doesn't have to go through the entire compression stroke resisting combustion. The fuel ignites as soon as it gets out of the injector anyway so there is no need for a high octane rating. I'm not quite sure about this, though, because I've never seen an octane rating given to diesel fuel.

That said, diesel engines DO have to be made stronger, thus heavier, in order to resist the compression ratios that can get over 25:1. These heavy components definitely limit the redline. It's also why diesel engines last so long.

 

I don't think you understand what I'm saying.

 

force = mass times acceleration, or torque = moment times angular acceleration. Horsepower is work per unit time.

HP= Torque * RPM....

The linear equivalent is work per unit time = force times velocity (these last two are within a conversion factor).

Matt

 

I think it is time to get the TDs in the USA and stop waiting. The cars have been in Europe and Asia for a while and if the people here don't believe saving the fuel and still get the power the new small diesels have now they are dense. I say the soooner the better for getting them on the market, I would buy one tomorrow if it was available. Plus it is direct competition for the other companies planning on bringing TDs or have brought them in already.

 

that you want the low sulpher deisel here now, with no delay. It's scheduled for oct/nov (refineries are supposed to be producing it june 1st) but there's been a bit of a relaxation already because it's hard and expensive to measure 15 ppm sulpher in diesel....

Matt

 

All you diesel fans may want to read this: MINI USA & MotoringFile Bring you the Answers

It's an interview with MINI product manager Jeff Stracco and the Diesel question is asked.

 

What's your point?