PD vs CR engines

obi_waynne

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Which is better the PD engines or the newer CR engines? Have all the problems been ironed out of the CR engines?

Are they very different in the way the two fuel systems work?

What are the advantages if any of the older PD engines?
 
CR is superior in terms of allowing the ECU finer control of fuel timing. The PD engines create fuel pressure using camshaft driven pumps - one per cyllinder. This apparently puts HUGE strain on the camshaft drive mechanism

CR engines use a common high pressure pump - this is not timed at all. The injectors are controlled electrically by the ECU.

CR is definitely the way ahead in my opinion.
 
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PD was the VW groups answer to common rail in the late 1990s. PSA group (Peugeot) Citroen was first to market in Europe with common rail direct injection for car engines.

VWs PD engines offered impressive performance for their capacity but I always found that they were coarser than Peugeot's early HDi engines.

VW caved in subsequently and followed the pack.

I think there might yet be life in the PD approach, I reckon it is capable of generating even sillier fuel pressures than CR can currently achieve. If someone can find a way to achieve the super precise fuel timing that common rail offers and combine it with PD's potential for insane injector pressures I reckon you'd have a winner.
 
^^ Diesel engines have become horrifically complicated over the last 15 years or so ^^

Yes, the performance and refinement have come on by orders of magnitude and generally outshine similarly priced petrol models.

But, the original appeal of diesel was economy (both fuel economy and economic servicing and long term reliability). This has been compromised.

Personally I still prefer the midrange slam of a good modern diesel over an equally good petrol car but I think over ten years you're likely to spend all your fuel savings on maintenance.

At the moment petrol is getting a lot more investment, look at Ford's 1.0 and 1.3 litre Ecoboost petrol offerings, just by way of example.

Sadly there's no such thing as cheap motoring anyone. No such thing as cheap anything really :)
 
to add to the thought T9; i have some old books on diesel injection engineering, so looked up what PD= translates to in USA speak, cam actuated unit injector.

and remembering back around 1973 had an old boat(63ft) with GM detroit 6-71 engines(diesels). it smoked on startup for mosquito control, neighbors didnt like the smoke screen.
so studied up on that engine model, mine had original LP(low pressure) hi volume unit injectors, and GM just introduced an injector reffered to as N series units

bought a set for both engines, installed them and all smoke stopped and made more mid range torque, equal max output. and consumption went down around 25%.

anyway the N series unit injector has pressure ratings anywhere from 20,000 up to 40,000 psi , WOW!!! and we thought CR was high.

the engine patents were sold BY Penske detroit diesel corp. to China, wonder why china would buy old USA machinery anyway?

they are made now in metric form, and sold around the world.
 
Common rail systems are routinely operated at 2000 bar and above. That 28,000 PSI so the pressures are pretty similar to the system Ronbros mentions.

The clever thing with common rail is that the injection is done in phases rather than one hit. And it's all under ECU control.
 
the PD engines are supposed to be a lot better in terms of economy. it wasnt unusual to see even the 150bhp 1.9 give high 50s the 2.0 units didnt seem to be as good even before they were forced to introduce the DPFs
the downside is the way the run and the smoke they create doesnt please the nice people in brussels.
 
good thinking from you guys.

now if we could use electronic multi-phase injection with PD(cam operated unit injectors), we just maybe on to something, and i'm sure the engineers are working on it as we speak.

seems i recently read about same thing!

Ron
 
It's a shame that diesels when towards electronic injection. Tinkering with my 306 being a mechancally injected diesel was great fun. Very easy to fine tune the injection timing and make power all at the same time whilst increasing MPG. My actual understanding is some what limited compared to HDi for example, but I had a pretty good understanding.
 
The original simplicity of the diesel engine has been lost, that's for sure. Common rail engines to respond beautifully to remapping though.
 
All completely in my own experience and opinion...

Commonrail engines are a fantastic idea in theory. Max power v effiency, let the computer sort it all out. When it works, it's great, when it doesn't, it's just another bill at the end of the month.

PD, when a cylinder needs fuel, it gets it mechanically there and then, no electrics to rely on. Again, when it works, it's great but when it doesn't, it's just another bill.

I love the way CR engines run, particularly Peugeots HDi and Renaults DCi systems but again, when they break down, they can be a nightmare. It can be so hard to find the true source of the faults sometimes. Many people just plug the computer in, oh that sensor is broken, change it, but they don't see the true source of the fault instead, the sensor got blocked with filings from the pump because it's eating itself from the inside out.

I'm a big fan of old school direct injection, particularly the old Peugeot XUDs. If it ain't broke, why fix it?
 
The original simplicity of the diesel engine has been lost, that's for sure. Common rail engines to respond beautifully to remapping though.

A freind of mine had a Vauxhall Astra van, and that went like stink after he had it remapped.
 
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I had my 16 valve 2.2 HDi Peugeot remapped by Celtic tuning - that went like a missile afterwards, not that it was slow beforehand mind. It was a very 'petrol-like' diesel too - pulled happily to 5500rpm and extremely quiet to the point you' not know it was a diesel, never mind a four cylinder one apart from cold start.


Midrange was amazing with 320lbft (yes lbft, not Nm !!) on tap. 50-70 in about THREE seconds in FOURTH gear !!!
 
I had my 16 valve 2.2 HDi Peugeot remapped by Celtic tuning - that went like a missile afterwards, not that it was slow beforehand mind. It was a very 'petrol-like' diesel too - pulled happily to 5500rpm and extremely quiet to the point you' not know it was a diesel, never mind a four cylinder one apart from cold start.


Midrange was amazing with 320lbft (yes lbft, not Nm !!) on tap. 50-70 in about THREE seconds in FOURTH gear !!!

Jesus.... What models did the 2.2 litre unti come in?
 
406 Coupe.

406 Executive Saloon and Estate: GTX, Executive and later SE models.

No automatic transmission in the 406 2.2.

It was also used in the Peugeot 607 which I believe was available with A/T.

Engine code DW12TED4

Mine was a GTX saloon - very well specced up cars.
 
Big fan of the 406 coupe. They also had V6's didn't they?

I know the DW10 comes in the later 306 models, but was always put off by how difficult they were to extract power, cheaply any way.
 
HDI fun ; actually the pre-combustion chamber engines do inject fuel directly into the pre chambers.

we sometimes make comments about it, DI injects fuel into the piston crown!

anyway, most of us do know the principles involved.
 
a little thought about the newer Ford type Ecoboost petrol engines.

a friend of mine has two new 2013 Ford trucks, one is gas ecoboost, other is 2013 Ford Diesel power stroke.

he drives one or the other according to his needs of the day.

at light or no loads the gas one has good mpg, about same as diesel one, BUT when he hauls a trailer with weight in it, the diesel is much more stronger, and the gas one loses mpg quickly at hi-way speeds,same loads.

i guess its all about the torque.

i have been often asked,what is so different between a diesel and gas truck, simple, the diesel will make more money in the long haul!

example; a 4seat car with 4 big people, will be better of as a diesel, than petrol, on a long trip.
 
HDI fun ; actually the pre-combustion chamber engines do inject fuel directly into the pre chambers.

we sometimes make comments about it, DI injects fuel into the piston crown!

anyway, most of us do know the principles involved.

????

That's obvious - the injectors supply fuel to the pre chamber rather than the main combustion chamber. What did I infer??

Bit lost- this sudden heat is getting to me !!!
 
HDI,hope i didnt offend?

what i'm trying to convey,is, all diesels could be reffered to as Direct injection engines!

in reality, they all inject fuel into a chamber, no matter where its located, wether its in the head(pre-chamber) or in the piston crown.

both have some advantages, but for reducing fuel consumption ,chamber in piston has proven the best(so far).

DI in Piston,in the early mechanical inj., had noise and emission problems,(not able to control volume and timing properly). and very hi cylinder pressures(things had to be built heavy and strong). a disadvantage! and required hicomp.ratio to start in cold temps.

the advent of elec. Piezo injectors and a silly computor to manage multi-phase injection processes, has changed all that.

pre-chams. had extremly hi swirl and made cold starts easier,with glow plugs,(glow plgs were(are another system to fail).

it seems, finally after many yrs, that the latest designs,that lower comp.ratio and lighter component parts, things are better overall!

some thing that should be aware of,Diesel fuel itself has changed, from the 40-50s to new formula that is out today, higher Cetane and other added products, like combustion enhancing additives, the negative to the fuel is it does not give the MPG that the old fuels had ,BTUs per given volume, simply does not have the energy that the old had .

but it is a cleaner burning fuel, so we will have to just pay out more money to save the planet, course we do know that when the polluting humans are gone, the planet earth will still be here,changed but still here.
i'm ranting so???
 
In which case we could argue that all petrol cars are have direct injection because fuel is injected directly onto the back of the intake valves in some cases.

No - let's not - that's silly
 
all diesels inject fuel into a combustion chamber, an intake port is not a combustion chamber, if you have burning taking place there,YUP, you got a problem!

we probably should let this one drop, its all about how the words are used.
 
I agree - we both understand exactly how the various systems operate but other folks might not so let's keep the thread open.


I don't pretend to understand all of that, but I am learning all the time thanks to you chaps.
 
that peugeot 2.2L HDi, sounds like a great car, but i have never seen any Peugeot diesels cars in USA, except back around 1979-80, a 4cyl. wagon,no turbo, noisey and smokey.

i guess like everything , things have progressed lightyears ahead, along with astronomical costs.
 
That's the old thing mate isn't it. Cost effectiveness to us car buyers. We set the bar it seems.

Agree totally - there was nothing great about diesel cars in the 70s and 80s apart from fuel frugality.

And I to tend to agree now - diesel engines are horrifically complex now and require very prescriptive routine servicing.

To the point that I'd take gas for overall running cost efficiency!!! Diesel for the sublime low/mid range torque and sheer effortless driving feel. Performance if you will :D

Difficult times indeed Mr Ron
 

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