How do these compare in terms of durability?
Obviously old low tech indirect injection diesels are where the 'indestructable diesels' legend comes from, but how less fragile is an older setup than CR?
For example, the VAG based 1.9 110hp that will be in the Toledo I buy, vs the HDi setup in my current car.
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An old style Diesel, so long as it gets a supply of air to breathe, will run underwater!
CR are great when they are running, but a nightmare when they go wrong. You are then totally in the hands of the repairers and (unless you know a lot about CR systems) you just have to pray they are competent as they spend your money....
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Only in cars did 'old' diesels use indirect injection. In trucks the more efficient DI was what was commonly employed.
I don't think diesel engines are more or less durable than petrol. They are certainly typically made of much beefier, but that is to cope with a more violent combustion process (and nowadays a much higher torque).
Engines rarely fail because they are not 'strong' enough... but they do degrade/fail through poor maintenance or some ancilliary part (timing belt, tensioner, pump). You might like the idea of an all iron block, but what really counts is that cheap piece of plastic...!
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For example, the VAG based 1.9 110hp that will be in the Toledo I buy, vs the HDi setup in my current car.
Are you sure that the Seat Toledo engine isn't a PD engine ?
In which case it would be more efficient than most common rail units.
I think it is a fair assumption that both IDI and DI diesels had the bullet-proof reputation due to their relative simplicity, having only a rotary injector pump and a set of 'dumb' injectors to worry about.
The only reason manufacturers (like Peugeot) used indirect injection was for quietness, as it knoks at least 10% off the efficiency of the engine compared with a comparable DI diesel.
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>> Are you sure that the Seat Toledo engine isn't a PD engine ? In which case it would be more efficient than most common rail units.
There is no evidence to suggest that PD is more efficient than Common Rail, to the contrary hence VAG have gone Common Rail on their new V6 engines.
PD and Common Rail are both more efficient than IDi or Di though a belt driven PD engine is such a illogical design.
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Fuel consumption on the PD engines, compared with say the Honda 2.2 or other CR engines? VAG moves to common rail for the V6 may be more to do with escalating cost: piezzo-electric control of multiple injection timing plus 6-off PD injectors might be a technology too far!
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What's PD, please?
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What's PD, please?
PD is an abbreviation for "Pumpe Duse" which translates to "Pump Injector" as confirmed by a German friend.
www.honestjohn.co.uk/forum/post/index.htm?v=e&t=39...2
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Thanks very much, SjB. The Canadian Driver link was to a very good little non-technical piece that explained the whole system beautifully and ended in an impassioned plea for frequent fuel filter changes. It made me want a V10 turbodiesel VW Phaeton more than ever.
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Thanks very much, SjB.
My pleasure!
I'm pleased your question was answered.
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The V6 VW diesel is common rail as opposed to PD (unit injector) for the simple reason that there is no space in the V6 head assembly to accomodate the drive system for unit injectors.
Either system will give the very high injection pressures and pilot injection required for current high performance DI diesels and an owner would be unlikely to be able to tell the difference. Unit injectors are very hard on the timing drive however - no problem on commercial vehicle diesels with a geared drive but likely to cause high stresses in a belt driven system. Maybe the recommended belt change intervals reflect this - compare the belt change requirements for the latest PSA HDi units, with that for the VW PD unit. The high pressure pump for the HDi is a much easier load for the drive belt.
659.
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Fuel consumption on the PD engines, compared with say the Honda 2.2 or other CR engines? VAG moves to common rail for the V6 may be more to do with escalating cost: piezzo-electric control of multiple injection timing plus 6-off PD injectors might be a technology too far!
The PD engines still give just about any CR diesel a run for their money on fuel-economy, having spoken to people driving BMW/SaaB and Honda diesels, although some of the state of the art units like the Honda and BMW are very quiet at tickover etc.
I raed an article in a VaG publication that said that the cylinder head design to accomodate the PD 'unitary' injectors was too difficult, plus the fact that the PD system has limited further scope for pilot injection and further emissions tuning.
I have a PD engined Audi which I love, but PD seems like a technology which has reached its summit.
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My Passat was pre-PD but the engine was quite amazing on fuel - by brimming measurement, over 60mpg on long runs. The consolation is that there is more to come from VAG, I think. Roll on SunFuel and CCS.
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>> >> >> Are you sure that the Seat Toledo engine isn't a PD >> engine ? >> In which case it would be more efficient than most common >> rail units. >> There is no evidence to suggest that PD is more efficient than Common Rail, to the contrary hence VAG have gone Common Rail on their new V6 engines.
My entirely subjective impression was that PD engines may be better at bottom of the rev range (~1500rpm). I'd be curious to see a comparison of torque curves.
I also thought PD engines could produce higher injection pressure but really nobody needed it - it is already enough to 'cut through glass'.
Many people say that old technology is much simpler, but it all looks complicated enough to me.
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Are you sure that the Seat Toledo engine isn't a PD engine ?
I don't think the 110hp is, no. At least, I hope not.
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>> Are you sure that the Seat Toledo engine isn't a PD >> engine ? I don't think the 110hp is, no. At least, I hope not.
The 110bhp is not a PD engine, it was an upgraded version of the original 90bhp TDI unit.
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>>The only reason manufacturers (like Peugeot) used indirect injection was for quietness...
I think there's a bit more to it than that. Until relatively recently (in the lifespan of the IC engine), it was quite difficult to get direct injection diesels to rev without producing lots of smoke.
The extra air motion that an indirect injection engine's pre-chamber gives aids rapid fuel/air mixing at higher engine speeds.
Better mathematical models, enabled by increasing computer power, and the more widespread use of CFD codes in the modelling of airflow in engines, have enabled modern direct injection designs to overcome this restriction.
Number_Cruncher
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Most of my working life has been spent working with diesel engines, mainly large marine or plant engines.
My ideal diesel engines are the ones where there are no electrical wires any where near them!
But alas to gain ever cleaner emissions and make automotive diesels more responsive, electronics are playing a bigger part, it's something we will have to get used. I can remeber as a apprentice the old hands had nothing but scorn for the DPA fuel injection (like on the old xud engines) pumps replacing Jerk inection pumps on small plant. Basicaly you can get away with even pumping water through a jerk pump (stands up to great deal of abuse) where as a DPA will destroy itself
Most large Plant engines still use Jerk type injection pumps. There are many that are becoming electicaly opperated and electronicaly controlled... Oh dear!
My point being we will possibly look back in a few years time, and wonder what all the fuss is about, as more electronic controlled diesel systems become either more reliable, or they become simpler to fix
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>>where as a DPA will destroy itself
I remeber my father always cursing about this pump, he had many of them fail on the various AECs in his fleet (Ergomatic cabbed, Marshalls, Mercurys, Mammoth Majors, and Mandators) at the time. The main drive shaft into the hydraulic head would snap, leaving the truck stranded at the side of the road. The failure was so common, he always kept a spare reconditioned pump in stock.
Long after he sold our last AEC, I enjoyed taking our spare DPA pump to pieces to see how it worked - one of many things that I never put back together again! :-)
Number_Cruncher
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My ideal diesel engines are the ones where there are no electrical wires any where near them! But alas to gain ever cleaner emissions and make automotive diesels
I know i'm repling to my own thread! BUT had a classic example of the above.
My son has been pestering me to get a old lister diesel thats been standing in out garage for at least 10 years started
Sure enough started 1st time HONEST! not a battery or wire in sight! point proven electrics = unreliability!
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Where I used to motocross in Lyne had an old dumper truck we used to grade the track with a drag at the back.
Must have been 30 years old, kept outside all the time, serviced once in a blue moon, oil looked like it had just come out the ground; it still (handle) started every week. (Petters engine)
It didn't die - a group of "travellers" {edit by DD} decided their need for it was greater than the clubs.
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Many years ago I bought an old boat to which someone had retro fitted an even older Petter twin cylinder diesel engine. No reverse and hand start !
I got caught out a couple of times early in my ownership with the boat sinking at it's moorings. If the boat settled on the wrong side when the tide went out, the incoming tide would enter the exhaust hole and fill the boat up. When the tide went out again, I had to fumble about in the bilges and find and remove a wooden bung to drain the thing. As for the engine, I just used to drain the water from the bottom of the sump, Change the fuel in the 1 gallon tank, bleed it, swing the engine over a few times with the decompressor levers on to clear water from the heads, let the levers go, and off she'd go - running as though nothing had happened. I don't suppose that the salt water did much for engine longevity but at least it used to go again. I can't see many of todays sophisticated and reliable diesels standing up to that sort of treatment.
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The dumper was a twin so it was probably the same engine. Think the maximum speed was 2000rpm...might've even been 200!
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If I remember correctly, It was a twin cylinder air cooled engine, about 8 hp @ 1200 rpm. According to the previous owner, it started life as an industrial water pump engine.
It had an exposed flywheel, was very noisy and vibrated like an earthquake, maybe thats why similar engines aren't fitted to modern cars.
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