Petrol VS Diesel

[ca6]

Yes. Or was that a trick question?

 

[ruuman]

Re: Petrol VS Diesel

Petrol

are more reliable

You see I would argue that, most petrol engines get about 200,000 miles max before they are so worn that it's not worth replacing them. Your average diesel will live for much longer. Generally speaking diesel have longer service spans too. Think about it, most big trucks generators and large ships have diesel's not just for economy but reliablity.

Plus with a diesel you have the advanatages of being able to run on chip fat oil and biodiesel. If your an off roader waterproofing is not an issue.

As for starting at cold temps and fuel waxing, modern fuels don't seem so effected as old style diesel fuel.

Probably the worst thing about a sporty diesel is the low rev range and extra weight due to the higher compression ratio required.

Diesel
+ Fuel economy/ effeciency (30% efF)
+ torque
+ Reliability
+better for enviroment
-Heavy
-Small rev range
-Complex fuel pumps
-Glow plug warm up

Petrol
+Less weight
+Large rev range
+Larger BHP figure avalible
- In efficient (8% eff)

As for noisy and vibration, sure a diesel transit sounds like a bunch of spanners and shakes like a parkinson patient, but a high quallity d motor like a jag is very much a different machine. I if you want great noise go find a nice big supercharged straight 8, that will change your mind

At the end of the day though it's whatever is best for the job

Ruu

 

[idletask]

Re: Petrol VS Diesel

Think about it, most big trucks generators and large ships have diesel's not just for economy but reliablity.

OTOH truck Diesel engines don't even reach 3000 rpm...

Worse, supertanker Diesels don't even reach 200 rpm (yes, 200, not 2000).

 

[Jostyrostelli]

stupid poll

petrol?

diesel?

Yeah right....the first one btw is powered by an electric engine (which is driven by a diesel)

Not relevant anyway

 

[Mischief007]

I'd take diesel but only when the Diesel fuel changes here in Canada. Right now it's designed for trucks and not cars. Well not european diesel engines. There's too much sulphur in Canadian diesel, something like 500 ppm. By 2006 they are hoping that to be 15 ppm. So I'm hoping that happens and more manufacturers will carry the diesel engine.

 

[Daniel]

Well, I just watched the new Top Gear ep. and it seems like JC totally agrees with me. You buy a diesel only to save a little bit of money, wich is completely uncool.

Let them politicians and snobby people drive their diesels and let the real enthusiasts have some fun. Fun and enjoyment is what I look for in a car. Practicality and economy is like 4th on the list. If you wanna be an enthusiast, you have to make some sacrifices. Your wallet cant always be full, if it is you get paid to much or you are boring. (Unless your saving for obvious reasons like health, house and food.)

(I am being a bit extreme.)

 

[Cruzz563]

Diesels are getting better, the earlier ones revved low because they were OHV, anyone who has been in a GM vehicle (for the most part), knows they only usually rev to 5500 rpm. But now they have DOHC diesels that are starting to rev higher, because the demand for them to be just as smooth as petrol engines. I heard that E320 diesel Mercedes brought to the states and it doesn't sound too bad, it's a DOHC inline 6. Not too shabby.

Sorry if this has been discussed about the dohc thing, just skimmed thru

 

[bone]

there realy shouldn't be any debate going on... petrol is WAAAAY better than diesel.

the reason diesel is so powerfull these days, is that diesel engines are already tuned from the factory. the VW 2.0 TDI has a fucking compression of 19.5:1. if they put the same setup on a petrol engine, you"d have way to much hp.

2nd, diesel is MUCH worse for the environment, the exhaust gasses of a diesel are more poisonous than a petrol.

the only reason why diesel is so cheap, is because it's funded by the government. at first petrol and diesel were about the same price. but since all trucks and big transport things ride on diesel, the government wanted to support the economie, and lowered the taxes on diesel. and they still are and remember, a diesel car is more expensive to make/buy

and if there is anyone who claims that a diesel engines is more fun to drive, he hasn't driven a petrol and a diesel engine.


the only reason why diesel might be better, is that it creates loads of torque. there is for example a company that equips the VX220 with a diesel engine. i can image that must be fun
and even then... by the time you hit the end of the throttle, it's time to change gear

 

[idletask]

there realy shouldn't be any debate going on... petrol is WAAAAY better than diesel.

the reason diesel is so powerfull these days, is that diesel engines are already tuned from the factory. the VW 2.0 TDI has a fucking compression of 19.5:1. if they put the same setup on a petrol engine, you"d have way to much hp.

You don't know much about ICE, do you? If petrol engines have such "low" compression ratios it's simply because if there's more you get detonation! Have you ever wondered why turbocharged engines have lower compression ratios than NA ones?

Compression ignition _requires_ high compression ratios. And compression ignition is how Diesel engines work. You just can't do that with petrol, it's too volatile. And BTW the 535d has a 16.5:1 compression ratio, which is very low for a Diesel.

I won't do again the pollution stuff, I've explained it all in the 535d thread.

 

[idletask]

and if there is anyone who claims that a diesel engines is more fun to drive, he hasn't driven a petrol and a diesel engine.

Well, I'm very sorry to say that a few years ago, I drove both a 330d and 330i because I hesitated on which one to buy. The d was more enjoyable on the road. That's it! More instant power at usual road speeds. When you drive more than 40k miles a year like I did, this is what you're looking for.

 

[idletask]

Compression ignition _requires_ high compression ratios. And compression ignition is how Diesel engines work. You just can't do that with petrol, it's too volatile.

Just as an added point. High compression ratio is the responsible for Diesel clatter. Now tell me you want that on a petrol engine

And that's why the trend to modern Diesel injection is more injections per cycle: smoothe out the pressure increase so that there's less clatter. Best systems do up to 6 injections per cycle. BMW's system only does 4, but then it has a very low (for a Diesel) compression ratio.

 

[Jostyrostelli]

GO IDLETASK GO IDLETASK

Exectament!
You don't switch a button and change your compression ratio, it has all to do with the fuel in it, diesel has to ignite on it's own and needs a higher compression ratio (higher temp) to ignite. Petrol has a sparkplug so they don't need the high temp (high compression ratio)

 

[idletask]

You don't switch a button and change your compression ratio, it has all to do with the fuel in it, diesel has to ignite on it's own and needs a higher compression ratio (higher temp) to ignite. Petrol has a sparkplug so they don't need the high temp (high compression ratio)

Acutally the frontier may well blurr in the coming years. Some manufacturers including Toyota and PSA are working on controlled compression ignition for petrol engines, and on the opposite side of things BMW is working for spark ignition on Diesel engines... So it may well be that one day we will end with only one type of fuel at the station anyway, and this debate will then definitely be obsolete, which it already is today.

It's the same on the French forum which I moderate, I quite feel at home here

 

[ruuman]

Compression ignition _requires_ high compression ratios. And compression ignition is how Diesel engines work. You just can't do that with petrol, it's too volatile. And BTW the 535d has a 16.5:1 compression ratio, which is very low for a Diesel.

I won't do again the pollution stuff, I've explained it all in the 535d thread.

16.5:1!!!!!! Jes that is stupidly low for a diesel, idletask you seem to be in the know about these things, have you seen anything recently about spark assist diesels?? I read an article early last year but never heard anything else.

Ruu

 

[Jostyrostelli]

You don't switch a button and change your compression ratio, it has all to do with the fuel in it, diesel has to ignite on it's own and needs a higher compression ratio (higher temp) to ignite. Petrol has a sparkplug so they don't need the high temp (high compression ratio)

Acutally the frontier may well blurr in the coming years. Some manufacturers including Toyota and PSA are working on controlled compression ignition for petrol engines, and on the opposite side of things BMW is working for spark ignition on Diesel engines... So it may well be that one day we will end with only one type of fuel at the station anyway, and this debate will then definitely be obsolete, which it already is today.

It's the same on the French forum which I moderate, I quite feel at home here

Really? How does that work? Diesel with a sparkplug? What's the use for that? They wanna have a lower compression ratio for Diesels?

If you have some links or more info on that...

 

[idletask]

16.5:1!!!!!! Jes that is stupidly low for a diesel

Indeed... At 13:1 it just won't ignite... But then it's turbocharged, so...

idletask you seem to be in the know about these things, have you seen anything recently about spark assist diesels?? I read an article early last year but never heard anything else.

I just know that BMW is working on it and that ends there. But given the chemical composition of Diesel it would require quite a spark, and I think we won't see that coming before cars turn to 42V. That's probably 10 years from now.

As to the goal it's simple: break the 5k rev barrier The only reason why Diesel engines don't rev (much) past that limit is because the expansion speed of the fuel/air mixture is limited, whereas it's insanely fast (detonation) with petrol (and that's why controlled compression ignition is hard to achieve with them too). Expansion speed limits also explain why ALL Diesels are either square or long stroke. A short stroke Diesel just makes no sense, as the longer the stroke the higher the torque. Short stroke is OK if you can rev high only, therefore petrol only.

 

[bone]

it seems i don't know that much about a diesel engine

it was very interested what you wrote until now. i assumed they were pretty much the same as petrol engine. well, this can't be, i'll do some research so ii know what i'm talking about

The only reason why Diesel engines don't rev (much) past that limit is because the expansion speed of the fuel/air mixture is limited, whereas it's insanely fast (detonation) with petrol (and that's why controlled compression ignition is hard to achieve with them too).

do you mean that a diesel engine without any electronics (and big enough intakes) would keep reving until it ceased?

 

[idletask]

do you mean that a diesel engine without any electronics (and big enough intakes) would keep reving until it ceased?

As long as you feed it with fuel, basically, yes. Electronics are just there to inject just the right amount at the right revving, and according to the throttle position (there's no throttle butterfly on a Diesel, only the amount of fuel injected matters!). Past 5k or so, the extra fuel will just go unburnt to the exhaust pipes, so...

 

[Jack Malmostoso]

I have a 156 Sportwagon Diesel and it is just great: it is fast (it really is), it is cheap and the car overall is great.

I see a lot of people here are against diesel, but give a try to a 53somethingd and then you tell me.

 

[Jostyrostelli]

Welcome Jack, I've driven the 156 JTD and I loved the turbosound on it!