Are modern diesels just not worth the hassle and expense?

[Dieselman]

And it has been suggested that perhaps the move to 7 speed transmissions is down to the predominance of diesels in larger cars.

Like the Lexus eight speeder.....oh, hang on, no Lexus diesel for the LS.

Typically diesels require less gears due to having more torque so can pull wider ratios.
Low torque engines need more gears to keep within the power band.

 

[oldcro]

Turbochargers seem to need to be in that bag.

And it has been suggested that perhaps the move to 7 speed transmissions is down to the predominance of diesels in larger cars.

So the 'expense of adding anything' isn't necessarily that straightforward.

I'm not sure if you're agreeing or disagreeing with me Dryce, as my post was in response to NicDale's post No. 5.

 

[rf065]

Before anyone mentions 320 CDI vs 320 petrol, try sticking a turbo on the petrol

Yeh, then you could probably get it down to 9MPG. It would be faster than the diesel though.

Russ

 

[lynall]

Dont forget new diesel engines are getting harder to get cleaner so we now have an additive called adblue for the treatment of the exhaust gas.

Will be expensive when it goes wrong, thats not if but when

I am still waiting for someone to come up with a cheap way around the adblue system but have not seen anything yet.

Oh yes and some of the systems even have heated tanks tp prevent the adblue freezing



Lynall

 

[Dryce]

Like the Lexus eight speeder.....oh, hang on, no Lexus diesel for the LS.

I thought *you'd* probably come along with that. I can't figure Lexus on this oene wither - other than the "well we just can ... OK?" or "more is better",

Typically diesels require less gears due to having more torque so can pull wider ratios.

Having the torque low down means you generally pull taller gearing. It doesn't necessarily mean that you need fewer gears - that's down to the the shape of torque/power curves and the driving characteristics you're looking for under a given operational load.

Low torque engines need more gears to keep within the power band.

A low torque engine may have a wide power band.

I think it would be more general to say that engines with narrow powerbands require closer gear spacing (and likely more gears) in order to meet their operational needs.

AIUI modern turbo diesels still have a drop off on the torque curve at fairly low revs so the resulting torque band is quite peaky - with the power band being somewhere further up and again quite peaky. In effect a modern Diesel doesn't look so different to a motorcycle engine except the revs are around one third to half those of the m/c engine.

 

[Dryce]

I'm not sure if you're agreeing or disagreeing with me Dryce, as my post was in response to NicDale's post No. 5.

I'm just doing my GOM in the corner bit and pointing out these nice modern diesels maybe involve some extra engineering and compromises.

 

[Vlad]

Just reading some of the responses and it appears that maybe some people are trying to prop up the diesel v petrol argument by looking at performance from the respective technologies, whereas I'm really trying to focus on the long terms costs, which is the area I'm trying to get more comfort in....I'd be the first to say that as a day to day car, I prefer turbo diesels as I like the low down torque and mid range acceleration etc, however, the point I'm trying to decide upon is whether they will become a financial burden when they are 4-5 years old+ with 80-100,000 miles + on the clock......

Dieselman....interesting to see the life expectantcy of the piezo injectors....gulp....how much would one of those cost when it needs to be replaced?

 

[kusanku]

Just reading some of the responses and it appears that maybe some people are trying to prop up the diesel v petrol argument by looking at performance from the respective technologies, whereas I'm really trying to focus on the long terms costs, which is the area I'm trying to get more comfort in....I'd be the first to say that as a day to day car, I prefer turbo diesels as I like the low down torque and mid range acceleration etc, however, the point I'm trying to decide upon is whether they will become a financial burden when they are 4-5 years old+ with 80-100,000 miles + on the clock......

Dieselman....interesting to see the life expectantcy of the piezo injectors....gulp....how much would one of those cost when it needs to be replaced?

My last E320 cdi was seven years old, with coming up to 200,000 on the clock when I part-exed it last year. The reason I got rid of it was the infamous 210 series rust. Only engine work it needed was new glow plugs at about 120,000 miles, which was not really a big deal. They may not be as indestructable as the older, simpler models, but I still think they will last a lot longer than 80-100,000 miles. We'll see how long the current one lasts.

 

[Fady]

Not forgetting that diesels generally need servicing sooner and are still slower. Before anyone mentions 320 CDI vs 320 petrol, try sticking a turbo on the petrol

So why have Mercedes themselves not thought of sticking a turbo on a 320 petrol then

 

[Dryce]

So why have Mercedes themselves not thought of sticking a turbo on a 320 petrol then

More likely that it would be a supercharger given that it's MB.

Presumably they don't see a market given the strength of the diesels.

 

[W210 Fan]

looking at most manufactures and Brians CLS320 CDI thread it appears they are spending their money on fancy cup holder engineering and not compression ignition engine longevity, stick to big petrol engines I say, not a lot of stress on the motor and there is not replacement for sure displacement!!!

 

[lynall]

Isnt the C32 fitted with a supercharger to the 3.2 v6 lump? 300hp ish



Lynall

 

[ringway]

Following a discussion down the pub with a mate looking to buy a newish used diesel, it kind of got me thinking as to whether state of the art modern diesel engined cars are just future financial liabilities and whether you are better off just buying a petrol engined car as it appears that modern diesels can give their owners some nasty surprises in terms of maintenance costs and reliability once they start getting past 80,000miles

In the not too distant past, diesel engined cars were simple things and as a result reliability was first class....ie a W210 E300TD is a fine example...bomb proof engine with very little to go wrong other than changing the glow plugs, which can be a bit of a pain. Whereas an equivalent petrol engined car could always be prone to ignition issues which clearly don't effect a diesel, thus making them less reliable.

However if you then look at the later E320CDi....you start getting injector seals failing, injectors packing up (very expensive) etc. Removal of injectors being problematical which could result in a new cylinder head being required.

Then you start reading about other manufacturer's diesel engines and you start getting tales of woe regarding sticking EGR valves...downside of a sticking EGR being that the engine can end up consuming its own engine oil and will do so until it goes pop. Turbo seal failures also crop up a lot and again can lead to engines going pop....the one name that fairs the worst on all of this is Renault!.

You then hear of BMW having problems with the inlet manifolds and turbo failures on their 4 cylinder diesels and the story goes on and on.

Its clear that modern diesels have a hard job to do in meeting ever increasing emission legislation and this has lead to injectors becoming ever more complex and working to even tighter tolerances, but this just makes me think that once a modern diesel has done 80,000+ and is, say, out of warranty, that its just a ticking time bomb in terms of maintenance costs and in terms of buying one you would be better off with a petrol engined car, which to be fair have taken some great strides forward in terms of fuel economy in recent years, but do not appear to be affected by the same sorts of reliability issues that higher mileage modern diesels have.

Any thoughts on this?.....and does anybody have anymore info on other manufacturer's diesel engines....for example I've not heard of Toyota diesels suffering the sort of problems that European manufacturers have, or is that because I'm just not aware of them?

Oh and by the way here's a tale of woe from another friend who had the misfortune of buying a Renault Laguna 2.2DCi, but had the fortune of having an extended warranty!

In the time he owned the car which was 3 years and 75,000 miles (purchased at a year old and 10,000 miles), he had a replacement ECU, Turbo, 1x Injector, Glow Plug, another failed injector/seal which caused such a mess that a new cylinder head was needed....total cost in warranty claims from memory over the 3 years was something like £6000

Or there's the other story of a business colleague who came running into the office like a mad man shouting help and pointing at his 2.2DCi Laguna in the car park belching out a huge amount of black smoke as the engine lunched on its own engine oil and didn't stop until it went pop....provided a bit of entertainment for the day!

Cracking Post Vlad

 

[Uberwagon]

I love diesel engines, but in performance terms they just don't get close to petrols still. I await the reference to 0-60 times and 50-70 and 155mph top speeds etc but as this isn't pub talk there is far more to a performance engine than numbers. Response, feel, enjoyment etc all leave me wanting when in a diesel.

I'd still like to own one as a daily driver but it would have to be pretty special as it wouldn't cover very large mileages.

With regards to the expense, give it a few years, the technology is still relatively new so the cost of the special items, the flywheels, the injectors etc will come down as has everything else.

Diesel has its place, but not for me, it's not fun enough yet and the engine aren't good enough.

Dave!

 

[Bobby Dazzler]

So why have Mercedes themselves not thought of sticking a turbo on a 320 petrol then

vvvv lynall beat me to it!! vvvv

Isnt the C32 fitted with a supercharger to the 3.2 v6 lump? 300hp ish

The supercharged 3.2 has 349bhp, and after a run of only a few years was then replaced with the NA 5.4 V8.

Presumably they don't see a market given the strength of the diesels.

Given the tiny numbers of C32 and SLK32 I think it's fair to say the market is very limited in the UK - was much more popular in the US. Whether it would be so popular today would be a different question.

Even cars fitted with NA 5.4 V8 sold in tiny numbers in the UK, W208/9 CLK55, R171 SLK55, W203 C55.

Interestingly Audi are going down a similar route with a supercharged 3.0 engine.

 

[gIzzE]

vvvv lynall beat me to it!! vvvv



The supercharged 3.2 has 349bhp, and after a run of only a few years was then replaced with the NA 5.4 V8.



Given the tiny numbers of C32 and SLK32 I think it's fair to say the market is very limited in the UK - was much more popular in the US. Whether it would be so popular today would be a different question.

Even cars fitted with NA 5.4 V8 sold in tiny numbers in the UK, W208/9 CLK55, R171 SLK55, W203 C55.

Interestingly Audi are going down a similar route with a supercharged 3.0 engine.

Give it time, we will start to see loads more FI petrol engines, as you say Audi are using a supercharger and a turbo on their 3.0 V6 petrols to give more power than the 4.2 V8 it is replacing and the consumption is up by around 30% too.

BMW have said they are going back to a straight six with FI on it for the next M cars.

The new C180k is a 1.6 with a supercharger, it gets fairly good results and really good consumption.
I think we will see a 350 with supercharger soon, maybe not from AMG, but I reckon we will see one in one of the cars, maybe the new E Coupe or CLS.


Having said that do we really need FI?? if done right isn't a NA engine even sweeter??
Take the new BMW 330i, it is a NA straight six 3 litre petrol. It has 272bhp and does 0-60mph in 6.1 seconds, so almost identical as the twin turbo diesel 335d, while returning absolutely stunning mpg.
The one I had for two days return 38mpg and did 500 miles on one tank.

But again, I bet we see problems with the direct injection system as they get older, but the tech will evolve and mature no doubt.

 

[scumbag]

Having said that do we really need FI?? if done right isn't a NA engine even sweeter??
Take the new BMW 330i, it is a NA straight six 3 litre petrol. It has 272bhp and does 0-60mph in 6.1 seconds, so almost identical as the twin turbo diesel 335d, while returning absolutely stunning mpg.
The one I had for two days return 38mpg and did 500 miles on one tank.

.

Now there was I thinking the 330i was a twin turbo.
you learn something new everyday.

 

[gIzzE]

The twin turbo 3.0 litre is the 335i, but it uses the older steel block engine, which is now 2 generations old.

I think the 740i uses the new 3.0 litre alu block with two turbos on it so I'm sure the 3 and 5 series will get it soon.


What is it with these companies at the moment.

C180k is a 1.6
C200k is a 1.8
C230 is a 2.5
C280 is a 3.0

C200 is a 2.2
c320 is a 3.0


318i is a 2.0
325i is a 3.0
335i is a 3.0
318d is a 2.0
325d is a 3.0
335d is a 3.0


Even the Merc dealer was adamant that the C180K was a detuned 2.0 the other day, so even they don't know what is what any more.

 

[hawk20]

The trouble with petrols (unless you go very big) is that they lack the real world performance of the modern diesel, unless you wind the petrol engine up to high revs. In modern British traffic conditions, the instantly-on-tap torque-driven thrust of a diesel, available at normal traffic-following revs, is a real joy to drive. The 320cdi can be sitting at under 2k revs and when a gap appears there is instant kick-in-the-back acceleration available -just effortless and so relaxing on a long run.

Only a big V8 equals it and they appear to be on the way out with sales barely warranting their production nowadays.

Even the 220cdi, I now have, offers remarkable reponsiveness for normal use.

 

[stumpy1]

IIRC there is a VW engine of only 1.4 but with a Turbo and a S/C to give a good economy / performance ratio. I've not driven it, nor heard much about it so maybe it's not that great.

Our 535d is remarkable in every way but I just hate the process of filling the thing up. You have to stand in all that goo spilt by white van man and you end up stinking all day.