Diesel hatch backs.

[st4]

BM diesels have never been very economical, and the older 'performance' ones were gutless compared to MB engines because they were tuned for power not torque.

The newer ones are, the published figures are really good, and even the SD Twin Turbo engine can sneak below 225g/km CO2. However reliability, in particular to turbo lifetime is woeful.

 

[timskemp]

It fits in the W204. And the BMW 5.0V12 could be made to fit the 3 compact, I don't see how given the money and inclination it wouldn't fit in any car in the merc range... Anyone for a rear drive A class with a V12 where the rear seats used to be?

 

[Dieselman]

The newer ones are, the published figures are really good, and even the SD Twin Turbo engine can sneak below 225g/km CO2. However reliability, in particular to turbo lifetime is woeful.

All MB 320 CDi come in well below 225 g/km and that's without massaging the figures with Stop-start function.

 

[timskemp]

All MB 320 CDi come in well below 225 g/km and that's without massaging the figures with Stop-start function.

Not the ML (254), or the GL (261).

 

[hawk20]

All MB 320 CDi come in well below 225 g/km and that's without massaging the figures with Stop-start function.

Um, not quite all. The LWB S320cdi class can be over 225 with the wrong wheels. And all the ML320cdis and R class 320cdis are over 225.

 

[Dieselman]

Hmm. I made the mistake of thinking because we were talking about 5 series 353D that we would keep this sensible.

 

[st4]

It fits in the W204. And the BMW 5.0V12 could be made to fit the 3 compact, I don't see how given the money and inclination it wouldn't fit in any car in the merc range... Anyone for a rear drive A class with a V12 where the rear seats used to be?

I remember the bonkers 3 series compact, it was a Norwegian tuner that did it IIRC. I like the sound of a V12 A Class. Reminds me of the Espace Renaut did with the F1 engine in the back

 

[Uberwagon]

I've driven some powerful diesels and not one of them has given the 3 main things a great performance engine needs.

Power
Torque
Noise

Now, diesels are great in lots of ways, in my perfect garage i'd certainly have a diesel, 535D touring, something similar. But compare the very modern diesels and then jump in a nigh on 15 year old E39 M5 and you realise that diesel still has a huge way to go.

For something the size of an S Class though I think i'd rather have the top of the range diesel than petrol though, mainly for the extra range.

Dave!

 

[st4]

I've driven some powerful diesels and not one of them has given the 3 main things a great performance engine needs.

Power
Torque
Noise

Erm power and Torque are accounted for. The 320cdi makes 224bhp. thats only 7 less than my 52 plate BMW 3.0i I6 made so we have c. 75bhp/litre, not a bad specific output. Torque is something a diesel gives loads of and is a key driving charactersitc of a diesel engine, doesn't the 320cdi make 370+lb/ft torque. An E350 must make over 100 less.

I was in a BM I6 diesel, it genuinely sounded good, and even my little 4 cylinder diesel makes a nice growl between 3k and 4k rpm.

Looking at this poll there is clearly demand for a V8 hatchback diesel and scope for a 6 cylinder diesel hatch, which I am suprised genuinely.

 

[Uberwagon]

Erm power and Torque are accounted for. The 320cdi makes 224bhp. thats only 7 less than my 52 plate BMW 3.0i I6 made so we have c. 75bhp/litre, not a bad specific output. Torque is something a diesel gives loads of and is a key driving charactersitc of a diesel engine, doesn't the 320cdi make 370+lb/ft torque. An E350 must make over 100 less.

I was in a BM I6 diesel, it genuinely sounded good, and even my little 4 cylinder diesel makes a nice growl between 3k and 4k rpm.

Looking at this poll there is clearly demand for a V8 hatchback diesel and scope for a 6 cylinder diesel hatch, which I am suprised genuinely.

How much power and torque ends up at the wheels though is a different matter indeed.

Pop a diesel gearboc onto a petrol car and see how much worse it makes it. It may make more torque at the flywheel but that wont transmit to the road.

Golf GT TDi 150hp 155lbs

0-60mph = 8.3
Top speed = 134mph

Golf GTI 150hp 236lbs

0-60mph = 8.2
Top speed = 134mph

All that extra torque isn't really giving any benefits?

I realise that economy is a big bonus, and that's why I had a GT TDi golf, the in gear times were nice, but once you put your foot down a little further and realise there is nothing left to give, it becomes tiring.

All the diesels i've driven seem to give 90% of the performance for 50% of the throttle travel.

Plus again we have the sound, if mine sounded like a modern diesel (WHich do have a certain charm, they are definitely not clatter monkeys of old) then I can guarantee the throttle wouldn't have been pressed to the floor as much as it has done.

Dave!

 

[st4]

How much power and torque ends up at the wheels though is a different matter indeed.

Pop a diesel gearboc onto a petrol car and see how much worse it makes it. It may make more torque at the flywheel but that wont transmit to the road.

Golf GT TDi 150hp 155lbs

0-60mph = 8.3
Top speed = 134mph

Golf GTI 150hp 236lbs

0-60mph = 8.2
Top speed = 134mph

0-60 times aren't a really useful measure of performance for the following reasons

1. How often do you do a standing start to 60mph
2. Its dependent on initial traction i.e a mind engined car will do better
3. cars which can reach 60mph in 2nd gear (or even 1st gear) will do a lot better. For example the BMW 330i does the sprint in 6.5secs or so, it can hit 60 in 2nd, the Subaru Legacy 3 litre, deep in the 7s as it needs 3rd gear to hit 60. However road testers tout the Subaru as the faster car.

All that extra torque isn't really giving any benefits?

Wrong.

In gear from 30-70 and 50-70 tests diesels are much quicker, a BMW 320d matches a 330i in these tests and in the real world is just as quick but 1.5x more economical in fuel.

In your 2 examples the diesel car would have had much better in gear performance, meaning less gear changes, and a more relaxed drive.

Acoustically diesels have come a long way, and truth be told my pals 1.6TDCi focus sounds better than the 4 clyinder petrol.

 

[Uberwagon]

Of course the 0-60 times will be affected by the gearing if it needs a change to 3rd. The gearboxes are matched to the engine, so the performance figures are still very relevant.

They have their place but if at the top of the tree it's only because an equivilant petrol model wasn't made available.

The best way to gauge performance would be a 30 - 100 time, can anybody find one for the same model, say a CLS350 and CLS 320 CDI?

Dave!

 

[st4]

The best way to gauge performance would be a 30 - 100 time, can anybody find one for the same model, say a CLS350 and CLS 320 CDI?

Dave!

I wouldn't mind trying

 

[Uberwagon]

Sounds like a plan.

I tried what was once viewed as the best small performance diesel of the time (We wont mention handling as it was rubbish) and compared the the droney mess that is the 1.8T, it just didn't cut it.

If I cared about MPG though, then diesel wins hands down on long journeys and relaxed cruising. Just they aren't the 2 most important things I choose when after a performance.

Dave!

 

[st4]

Sounds like a plan.

I tried what was once viewed as the best small performance diesel of the time (We wont mention handling as it was rubbish) and compared the the droney mess that is the 1.8T, it just didn't cut it.

It wasn't a veedub golf GTi TDI 150 was it. These engines were really ratly, and if it was a MKIV golf the handling was no good anyway.

If I cared about MPG though, then diesel wins hands down on long journeys and relaxed cruising. Just they aren't the 2 most important things I choose when after a performance.

Dave!

Back on thread, a CLC with a 300bhp odd V8 diesel has a) plenty of BHP/ton on its own right b) heaps of Torque too.

New diesels (think 335d) give decent BHP and rival petrol engines (335i is only 15bhp more) but have more Torque and MPG. The engine doesn't rev as high in a diesel, but the peak torque is lower down and the gearing can be taller so it all works out.

 

[timskemp]

Trouble with performance figures and diesels is the fact that all that mid range torque comes from turbocharging. Off the line they have low torque, and being low RPM low power too so they have very low first gears, most are wrung out before 30mph, making 2nd a big leap if it goes much past 50.

Best way to get a good 0-60 (or 0-62) from such cars is to hold them on the handbrake at near max revs in second slipping the clutch to wind up the turbo, this is not recommended but can get good increases over the factory time by losing the 1-2 change time. Of course this is somewhat bad for the clutch. Changing flat from 1-2 and 2-3 is another way to help.

If anyone wants to loan me their manual performance diesel I'll demonstrate but you'll have to sign a waiver...

 

[Uberwagon]

The gearing is matched to the engine so it was designed for the best overall performance, cruising, acceleration etc etc

I like diesels, I was involved in test and development of them for 6 years and they are my bread and butter, but i've yet to drive one which will show an equivilant hp petrol engine that it is a better performance package.

Dave!​

 

[st4]

Trouble with performance figures and diesels is the fact that all that mid range torque comes from turbocharging. Off the line they have low torque, and being low RPM low power too so they have very low first gears, most are wrung out before 30mph, making 2nd a big leap if it goes much past 50.

Best way to get a good 0-60 (or 0-62) from such cars is to hold them on the handbrake at near max revs in second slipping the clutch to wind up the turbo, this is not recommended but can get good increases over the factory time by losing the 1-2 change time. Of course this is somewhat bad for the clutch. Changing flat from 1-2 and 2-3 is another way to help.

If anyone wants to loan me their manual performance diesel I'll demonstrate but you'll have to sign a waiver...

What if you have an Automatic.

 

[Bobby Dazzler]

Seems so tame these days, but I had a Rover 220 SDi in 1996 as it was just about the quickest diesel around at the time. With 105bhp in a car that was supposed to replace the Metro, it had some urge. Great car - my Dad still has it.

I think a V8 diesel may be a little heavy for a small hatchback though, which would have an effect on ride and handling, so I'd prefer the V6 with a Brabus box!!