Power vs Torque : Petrol vs Diesel

JHMEG

545i vs 535d on Top Gear from a few years back.

https://www.youtube.com/watch?v=_6WVRrMY32c

farva

I'd love to have a 535d, I'd say its an amazing car! My dad used to have an E39 530d MSport Auto years ago and it was an amazing car at the time, the 535d is the spiritual successor in my opinion!

Its a bit unfair putting the 535d against a 545i, they should have put the 535d up against a similarly priced and powered 530i or 540i(although I dont think it was around back when did that clip) and not a 545i.

Andrewf20

I saw a 535d sit on my tail on the M2 once at 70mph. Then it accelerated. Couldnt believe how quick it was. In my mind, its almost a perfect car.

JHMEG

It's a fair enough comparison as the petrol has more power but less torque. The reason I posted was to show which is better.

farva

JHMEG wrote: »

It's a fair enough comparison as the petrol has more power but less torque. The reason I posted was to show which is better.

You obviously aren't a diesel fan judging by your sig. I mean obviously on a track the lighter,more powerful, free revving petrol V8 will be faster on a track, especially when being driven by a pro race driver. But in fairness for everyday use the torque of the diesel is far more useful and practical then the power of the petrol.

JHMEG

farva wrote: »

But in fairness for everyday use the torque of the diesel is far more useful and practical then the power of the petrol.

Petrols have adequete torque for every day use aswell.

TheBazman

I'm a little biased as I have just gotten a 535d but I dont think it was a fair comparison - a 530i would have been better (I believe there is a 535i now in the States).

I used to have a petrol V6 with around 280bhp (roughly the same as the 535d) and if you were to floor both at 50 or 60kph I think the 535d would open up a pretty decent gap

Biro

A 530i isn't a fair comparison to a 535d. You can compare a 530i with a 530d. Unless a 535i comes out here, then you have to go for the 545i, which is going to be better.

Captain Slow IRL

JHMEG wrote: »

545i vs 535d on Top Gear from a few years back

You kinda spoil it with your sig:rolleyes:

maidhc

JHMEG wrote: »

Petrols have adequete torque for every day use aswell.

I can only compare a tricked out Pinto to a TDCi, but, yes, if you drop to third the Pinto will move, but you can overtake in the diesel in 5th..

This has an impact on drivability and economy!

unkel

Typical topgear. A quasi objective-result in the race between "the stig" and Clarkson, the former being clearly the better driver. Why didn't they swap cars after the first race?

The one thing that did surprise me was that the diesel was quiter than the V8 petrol at 70MPH

unkel

unkel wrote: »

Typical topgear. A quasi objective-result in the race between "the stig" and Clarkson, the former being clearly the better driver. Why didn't they swap cars after the first race?

The one thing that did surprise me was that the diesel was quiter than the V8 petrol at 70MPH

https://www.youtube.com/watch?v=OuNtw5XbxJg

^^^ listen out for the turbos OH YEAH

oh and for the TOP GEAR comparison to be fair the petrol would need to have a turbo too!!

maidhc

unkel wrote: »

The one thing that did surprise me was that the diesel was quiter than the V8 petrol at 70MPH

It shouldn't. Diesels are generally as quiet if not quieter than their petrol counterparts once away from the traffic lights. The fact they are geared much higher helps a lot.

unkel

maidhc wrote: »

It shouldn't. Diesels are generally as quiet if not quieter than their petrol counterparts once away from the traffic lights. The fact they are geared much higher helps a lot.

I'd have thought the 4.4l petrol is running at a lower RPM than the 3.0l diesel @70MPH both in highest gear. But I guess I'm probably wrong

tossy

What a silly silly comparison

A 4.5L petrol car weighing 1600kgs driven by a pro driver

Versus

A 3.5L diesel car weighing 1750kgs driven by a cycnical funny bastard (but by no means a decent driver)

This counts for nada like every other biased topgear comparison!

The stig in a 530d and a 530i around the same track on the same day and we see how we fare out.

conneem-TT

tossy wrote: »

What a silly silly comparison

A 4.5L petrol car weighing 1600kgs driven by a pro driver

Versus

A 3.5L diesel car weighing 1750kgs driven by a cycnical funny bastard (but by no means a decent driver)

This counts for nada like every other biased topgear comparison!

The stig in a 530d and a 530i around the same track on the same day and we see how we fare out.

The 535d has a ~3 litre twin turbo diesel engine and weights 1735kg and a 550i weights 1735kg (can't find a weight for the 545i as it's discontinued).

JHMEG

As I've already said aswell, the 535d has more torque than the petrol. The petrol has a bit more power.

Matt Simis

JHMEG wrote: »

It's a fair enough comparison as the petrol has more power but less torque. The reason I posted was to show which is better.

If the video was meant to show anything more than the entertaining banter of JC, then you failed.

Why do you start a diesel bashing thread every other week? I mean really, why does this personally bug you so much you online persona seems to revolve around it?

JHMEG

Matt Simis wrote: »

If the video was meant to show anything more than the entertaining banter of JC, then you failed.

You didn't see Clarkson and the Stig plant the accelerators on the first straight (which requires no skill) and the petrol pulled off into the lead?

If you don't like the thread you don't have to read it, never mind start moaning on it.

Cyrus

i dont know why everyone wants to see a 530i vs a 530d

in e39 guise at any rate, despite the delusions of the 530d owners, a std 530i was quicker than a standard 530d in 9 out of 10 situations.

From what ive seen the 335i is a better car than the 335d aswell, bit of course its horses for courses,

i do very little mileage so i would never take a derv over a petrol

peasant

Surely, the decision on what is "better" from a perspective buyer's point of view would also involve some element of cost?

And all of a sudden the diesel which is some 10.000 £ cheaper doesn't look so bad anymore. (Never mind the better fuel economy)

JHMEG

peasant wrote: »

Surely, the decision on what is "better" from a perspective buyer's point of view would also involve some element of cost?

Better is totally subjective, and I meant it that way.

maidhc

JHMEG wrote: »

Better is totally subjective, and I meant it that way.

In which case your repeated efforts to objectively justify that petrols are better than diesels is completely misplaced!

And at the end of the day it is a moot point which one is better than the other. They are different cars to suit a different buyer.

peasant

JHMEG wrote: »

Better is totally subjective, and I meant it that way.

...but we already know that you hate diesels :D:D

Instead of posting the link you could have just written:

"btw ...in case anyone has forgotten ...I still hate diesels!"

Would have saved us all a lengthy, pointless discussion

Ferris

peasant wrote: »

Surely, the decision on what is "better" from a perspective buyer's point of view would also involve some element of cost?

And all of a sudden the diesel which is some 10.000 £ cheaper doesn't look so bad anymore. (Never mind the better fuel economy)

+1

It all about what you need from a car. If you do big miles (15k+ p.a) buy a diesel, if you don't then buy petrol.

Look at the golf 2L tdi vs the 2L GTi in bog standard form. Both are turbo'ed. 137hp vs 197hp, 320Nm vs 280Nm, and 9s 0-60 vs 7s.

This doesn't take away from the achievements of some manufacturers improvements to diesel engine, BMW with their 123d for example with over 100hp to a Litre, but petrols are still better performance cars.

Personally I have a diesel and its great, really good to drive, so im not diesel bashing.

craichoe

conneem-TT wrote: »

The 535d has a ~3 litre twin turbo diesel engine and weights 1735kg and a 550i weights 1735kg (can't find a weight for the 545i as it's discontinued).

It has a Sequential turbo, having a twin turbo lump would cause severe turbo lag.

Anyways, silly comparison, its a touring car for Autobahn and the odd jaunt on a track.

Top Gear is not about practical comparison, its about entertainment, hence the blowing up caravans and firing Minis off ski jumps with rockets on the back of them. The Cool and Uncool chart is not really an objective guide .. especially from Clarkson.

A racing car for the track would have all the seats, sound proofing, cd changer, sat nav, aircon, electric windows and every other piece of unncessary equipment ripped out before it would be used as a RACE car on a track.

The pollution angle on diesels being worse than petrol .. its completely subjective, you can mash stats any way you want. Yes, diesel contain Particulates which are carcenogenic, but so is every other material we use thats derivied from crude oil.

If your so concerned that Diesel causes cancer, then don't drive a car at all, because burning Petrol causes cancer too and while your at it, don't use any more plastic containers at home, keep your food outside rather than use a fridge and walk to work.

The Co2 emmisions , and the tax is there to try to bring us closer to the numbers set out in the Kyoto protocol, not to address other emmisions at the moment.

If you have an issue with that, then contact your local MEP, and they can take it up on your behalf in the European parliament.

Link

JHMEG

Point of the thread was power vs torque, best illustrated by almost identical petrol vs diesel cars. One has more power, one has more torque. People can watch the video and decide for themselves which is better, power or torque.

I didn't think this'd turn into another "why does JHMEG post about how much he dislikes diesel" moan thread. How many of the moaners are moaning only because they own (slow) diesels themselves.

Matt Simis

Ferris wrote: »

+1

It all about what you need from a car. If you do big miles (15k+ p.a) buy a diesel, if you don't then buy petrol.

Look at the golf 2L tdi vs the 2L GTi in bog standard form. Both are turbo'ed. 137hp vs 197hp, 320Nm vs 280Nm, and 9s 0-60 vs 7s.

I thought it was commonly accepted the Golf "GT" TDIs have 0-60 times very close to the GTIs (petrol), but product ranging requires them to have slightly inflated book figures. I know on my car 0.8sec can be shaved from the 5.0 TDI (6.9sec) vs the 6.0 Petrol engine (5.9sec). The TDI is a over 150kg heavier (of course).

E92

JHMEG wrote: »

You didn't see Clarkson and the Stig plant the accelerators on the first straight (which requires no skill) and the petrol pulled off into the lead?

If you don't like the thread you don't have to read it, never mind start moaning on it.

+1

FWIW I had a very interesting yesterday, which is very relevent to this discussion.

Not only was it my first time driving a diesel, but the first time doing a back to back comparison between a diesel and a petrol. I even got to compare hydraulic vs electric power steering.

The car in question can only be the current Toyota Avensis.

I drove the D-4D 125 yesterday, as well as the 1.8 petrol.

Now any car mag I've read raves about the D-4D. It is one of the best diesels of it's kind so I'm told. The petrol is meant to be a good engine but not a patch on the oil burner.

I started off driving the petrol, and then got into the diesel. In terms of refinement, both were pretty similar expect when at idle. The petrol engine is still vastly superior, but at speed, apart from a different engine note, they were as far as I could tell pretty much the same.

Obviously the diesel would offer superior fuel consumption to the petrol, though I never bothered to check how much superior it was.

Both engines have almost the same amount of power, 126 bhp for the diesel, versus 129 bhp for the petrol, and it was the same car, so I've made it as objective as possible.

The first thing I noticed about driving them is that the diesel is more fun to drive. That is hardly surprising because the diesel has proper power steering i.e. a good old fashioned hydraulic power steering system, while the petrol has the crappy electric setup.

The petrol steers better because it weighs less, but the diesel feels more solid on the road and the steering is more informative thanks to the proper power steering.

That said a car that's supposedly rubbish to drive, the Volvo S40 grips the road better than either and feels more solid on the roads overall.

None of these 3 cars is going to leave you with a smile on your face but I found the Volvo to be the best of the 3 to drive, and the petrol Avensis the worst of the 3. There isn't a huge gap between the Volvo and the oil burning Avensis but there is a big gap between the petrol and diesel Avensis IMO.

In terms of engine performance, I never thought the 1.8 Avensis was any great shakes. It was good but not exciting. I'm rather underwhelmed by anything smaller than a 1.8 petrol anyway:D. The diesel wiped the floor performance wise. It wasn't even funny how much faster it was, no need to drop down gears or anything like that, just press the loud pedal down more and it was well able to move. Try the same thing in a petrol and you got nothing. The petrol has zero response below about 2000 rpm. Nothing. Zilch. Zip. Zada. Even flooring it got nowhere. By comparison the diesel at only 1,600 rpm was full of enthusiasm and had no difficulty getting up to speed when this was done.

I came to the conclusion that in everyday driving, diesel is indeed not just kind of better, but completely and utterly better than petrol. You don't have to change gears as often, in situations such as going up hills at a decent speed where you have to drop a gear or maybe 2 with the petrol, just put your foot down on the loud pedal a bit more in the diesel and that was sufficient.

Then I went back in the petrol and it felt rubbish compared to the diesel, having been blown away by the performance of it compared to the petrol. As I was driving it along, whatever way I looked I saw i had the rev counter above 4,000 rpm. I decided to give the petrol one last chance. And then I realised that I was driving the petrol all wrong. Above 4,000 rpm, and up towards 5,000-5,500 rpm it was a completely different ball game. Much more like the diesel at low revs. But a much more interesting sound. Much better reponse to pressing the loud pedal a bit more. I realised that actually petrols still are very good. The problem with the petrol wasn't the engine: it was with the driver. It's much more fun having to get a petrol in the upper half of the rev counter and hearing the engine work hard:D!

If Toyota gave both cars the same steering setup and the VRT system wasn't changing, then I'd take the petrol in a heartbeat. As it is, with the different steering setups, the diesel is better and with the new VRT system, then you'd want to be mad to consider the petrol variant.

If you drive a petrol like you drive a diesel, you're bound to think they suck.

A lot of people who have posted in this thread evidently drive petrols the way you should drive a diesel. I'm guilty of it myself. Of course for environmentally conscious driving doing what I did isn't going to save the planet. But if you're bothered about the environment then what are you doing trying to put your foot down for a bit of power in any car in the first place? If you're prepared to give a petrol a bit of stick they will reward you for your effort!

If you want something that's pleasant and relaxing to drive, then get the diesel. If you want something that requires a bit of effort on your part, but really rewards those who take it by the scruff of it's neck and a bit of fun to work hard, then petrol is the only option.

The 2 engines are like chalk and cheese. You have to drive them completely differently. If you're not prepared to give petrols a bit of stick and allow them get into the upper half of the rev counter then you'll think diesel is far superior, but do what I say and they're still more than a match for diesel, but more thrilling. Speed isn't everything in making driving fun.

The best comparison is still bhp then. Torque is great, but high revs and bhp is just as good!

I like both engines - both are good in their own completely different way. It would come down to which was cheaper for me. Lower running costs are a big appeal for diesels. If there was no such thing as running costs and the environment I'd have petrol every time though.

If running costs were the same for both, the better noise and ever so slightly better refinement as well as the ability to perform when you open the taps and give it a bit of welly make petrol a better choice. In today's world, where cars cost ever more to run, as well as "environmental" pressures, it makes the choice very hard. All that torque is useful when you're a bit lazy and don't feel like using the gearbox too much though! Unquestionably in July, diesel is the only way to go for most cars though.

Ferris

I have heard that the 140tdi's are closer to 150 from the guy that services my dads A6 2L tdi.

Haven't driven a MK 5 diesel golf but have driven the mk5 GTi and it was quick from the off and great through the gears. Can't see how a similarly sized diesel could touch it to be honest (bar the 123d).

craichoe

JHMEG wrote: »

Point of the thread was power vs torque, best illustrated by almost identical petrol vs diesel cars. One has more power, one has more torque. People can watch the video and decide for themselves which is better, power or torque.

I didn't think this'd turn into another "why does JHMEG post about how much he dislikes diesel" moan thread. How many of the moaners are moaning only because they own diesels themselves.

It is now, since you edited your post to remove your sig

C'mon man, if thats in there how can you not expect people to pick up on it.

by almost identical petrol vs diesel cars

both are BMW, their both cars i guess. Except ones heavier (plus Clarkson must add about 15 kilos)

One runs on Petrol, the other runs on Diesel.

Reminds me of the v-twin vs in-line 4 comparison, can't really compare, their just different.