Diesel>Petrol

[mintaka]

The old Diesel V Petrol argument...

Remember, that the following is from a total, self confessed diesel fan...

I have two cars. The CDTi, and a '91 Carolla GTi. The engine stats come to the following;

CDTi 1.9 L - 110 kw @ 4000 rpm - 320 nm @2000 - 2700 rpm
GTI 1.6 L - 100 kw @ 7200 rpm - 148 nm @ 5000 (approx)

Now get this, I love driving both cars!

Clearly the Astra urinates all over the Carolla for torque. In fact the CDTi has more torque at idle that the GTI max torque. What that means in practice is that the Astra has more kw that the GTI right through the rev range. The CDTi in fact will have more kw than a Commodore V6 until 3000 rpm!

This is why it feels relaxing and powerful to drive a diesel at low to middling revs. And remember, that's were you do 90% of normal driving.

Now, I can get the GTI to go like a scalled cat, but I have to rev it well past 4000 rpm before it feels powerful. And I have to keep it above that rev point in order to keep that powerful feeling. Don't get me wrong, I love wringing its neck, and it loves being thrashed.

BUT

Try driving it from here (Sydney) to Melbourne. Not that relaxing, and not the same feeling of instant omph under the foot. I would have to drive constantly in 4th gear to get the same sort of feeling that the CDTi has in 6th.

And really, that's what I like. The feeling of V6 levels of torque for small petrol 4 levels of consumption.

On a race track, you bring an engine to the top of it's rev range and try to keep it there. Although torque is important, in that situation, it's how fast you can rev and multiply that torque that will win the day for you. That's why petrol engines will continue to dominate because they can rev well past the 5000 rpm (or so) limit of a diesel, and thus make much more power from much less torque.

But in real world driving, if you had your petrol motor close to peak power all the time, a number of things would happen;
- The cops would think your a hoon
- Your engine life would be considerably shorter
- Your fuel consumption would be appalling
- It wouldn't be very nice for your passengers

Now because a diesel produces huge amounts of torque at low revs, it means that you can gear them much higher than a petrol engine. Even though a diesel can be out reved by a petrol, it can do more 'work' with the revs it's got. So I get the same "feeling" of instant power at much lower revs. Yes, I know that is a bit deceptive, but I've done the numbers (yes, I have no life) and for all intents I've got V6 under the bonnet, not a 1.9 L 4, for 95% of my diving experience.

So, what, it any conclusion can be drawn from the above ramblings?

If you want to drive at 10/10 th's all the time, get a petrol car, something like a WRX or SS.

If you want to have a car that "feels" powerful enough when being driven at 3/10 th's to 9/10 th's (normal driving) get a turbo - diesel.

Of course, this is just my opinion. I respect the differing opinions of the others here today.

:-)

Mintaka

[entice]

Well put Mintaka. By far the most rational of the diesel bunch. I disagree with your logic on syd/mel run, as most of the time both engines wouldnt be labopuring at all.. but the efficiently undoubtedly would be with the CDTI (as a side note, my 225 width sticky rubber clad 18" wheels on my CDX astra wagon with Tubby me driving, returns an average of 8.6L/100Kms... the difference in efficiency isnt really THAT much)

But, dont forget, you have a 16 yr gap in engines that you're comparing, and a naturally aspirated 1.6 Vs a forced induction 1.9.

Now, dare I ask... which one is more "FUN" to drive.....

[Wraith]

Yes that's all well and good, but what about these newer petrol turbo engines as I've stated above which produce their 100% torque outputs at well below 1,500rpm ?? ....... and you still have the benefit of the rest of the petrol engine performance regime !

The only good agreeable/sellable point for the oilers is their frugality.....

[mintaka]

No Entice, I haven't forgotten that my GTI is 16 years old. What amazes me is that after all these years, there still isn't many 1.6 L stock normally aspirated engines that can give better power figures. (The Honda VTEC 1.6 comes to mind, can anyone think of others?)

Certianally the GTI doesn't labor in anyway in 5th gear doing freeway speeds. But to highlight the difference, if anyone here is familiar with the Hume freeway by-passing Mittagong, there is a number of really long, steep sections. The GTI will need to change down to 4th near the top of the climbs, while the CDTi barrels over them in 6th like they're not there. It's that level of constant pull that I find so appealing.

Of course the more "Fun" thing to do would be to put the GTI into 3rd at the start of the climb and give it the beans! And when I was 22 that's exactly what I did.

But now I'm nearing 40, I want something a bit different.

The Astra is more "FUN". It's newer, more powerful (whether by kw or torque) much better handler and much more comfortable. But for short trips I'm never disappointed that I may have to take the Carolla. And there are some roads in the Blue Mountains, in the right time of day, with no traffic around where the old girl can still put the same smile on my face she did 16 years ago!

Any car is a compromise. A balance between power - economy, handling - ride comfort, price, size etc. Very often the car that suits you and your particular set of circumstances would be the very things that put some else off. And you're own requirements change over time. The car you want at 21 is not always the car you buy at 35 (when you have the money!)

For my own situation, semi rural trips within a hilly / mountainous environment interspersed with long intrastate runs, a high performance long legged turbo-diesel hatch fits the bill nicely.

Of course if I had the money, I would have a chipped BMW 535 D

Mintaka

[dieselhead]

mintaka, that's very well written. i couldn't spell it that well myself cuz i'm an engineer, and you know what they say about us: intelligent folk, but can't express themselves...

just got back to the office from a 3 hour trip, driving a VE on gas. what a joke of a car that is, compared to my Astra! it is a Berlina, $38k plus onroads, with a boot not much larger than my Astra's due to the gas tank... i really struggle to understand it's use to be honest.

[Wraith]

I'm an engineer, but hopefully I'm having no problems expressing myself too

So far none of the diesel people have responded to any of my comments....

Now I think we all know that you can't seriously compare an atmo LPG powered engine to a petrol or diesel turbo engine BTW was it an 8 or 6....

I don't think you'll have too much to complain about regarding torque output, from even a stock atmo V8 on LPG or not

[entice]

now....

umm...

i'l watch this one out.. for the moment....

my head hurts. Too many words! can't remember what I was going to respond to.

Maybe, in this case I'm not qualified to.

wrong letters after my name

[mintaka]

I'm an engineer, but hopefully I'm having no problems expressing myself too

So far none of the diesel people have responded to any of my comments....

LOL Sorry Wraith I can't type that quick!

Your comment in your earlier post is true, but I guess it's the way you look at it. I prefer to think that with the CDTi, I get the same performance experience as turbo-petrol for 95% of my driving and get 30% better fuel economy. And at this point in my life, fuel economy IS a big deal. Again, if I was 21 and wanted the ultimate, bleeding edge experience (and had the money and willingness) then I might make a difference choice.

Dieselhead - I too have to drive alot of hire cars, Falcodores for the most part. I find them to be a bland, truth be told. I don't get the same sort of turbo 'kick' that I get from the CDTi (I would assume the same holds true for a turbo-petrol)

To throw a spanner in the works, go to this site http://www.teslamotors.com/performance/performance.php and take a look at the torque curve on that!!! Holy freaking Mother.... Love to have a drive of that!!!


Mintaka

[entice]

100 ft-pds torque.. that aint that much

also they dont graph the petrol power curve.. wonder why

[digifish]

...while the CDTi barrels over them in 6th like they're not there. It's that level of constant pull that I find so appealing.

That was the point I was making also. It's the way the manual CDTi makes hills dissapear. It's an addictive sensation...as is the mid-range acceleration, it has a V8 like quality about it.

I am approaching 40 too, perhaps it's an age thing

digifish