Good news about the possibility of diesels returning to the US market . . . Does anyone know where one can get more technical details and discussion about the design of the current European CDIs? I'd like to know the principles behind the CDI design, turbo or not, common rail vs. injector pump, etc. Materials used, aluminum vs. cast iron, etc.

I clicked through the MB global website and was able to find only basic product specifications.

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04 GMC Yukon XL Denali, Black, 12k
02 New Beetle, TDI, Reflex Silver, 24k
89 300TE, Arctic White, 214k

90 300E, 142k (sold)
87 300TD, 128k (sold)
83 300D, 314k (sold)
79 300TD, 266k (sold)

Share your knowledge -

Wayne

I've got a technical article discussing the common rail/electropump systems, variable turbo's etc now massively used in tdi's and cdi's.

Let me know if you want it, because it's in Dutch and I will probably have to translate it for you?

Of versta je Nederlands? Dan zou het geen probleem mogen geven.

Greetings,

BB

I'm interested too. I'm Dutch also, but I can't translate it.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

Popular Science recently had an article about the technology in the newer diesel engines. I don't know which month it was in but I would check the issues a few months back. It was definitely either December, January or February.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

I used to work with a guy who rebuilt diesel fuel pumps when mine was acting up and got all the juicy details about how they all work. I'd be very interested how they work and even the direct injection gassers.

Thanks for the good replys. I will check the Popular Science Issues for their coverage. Also, I would very much appreciate the article in Dutch to be 'basically' translated.

__________________
04 GMC Yukon XL Denali, Black, 12k
02 New Beetle, TDI, Reflex Silver, 24k
89 300TE, Arctic White, 214k

90 300E, 142k (sold)
87 300TD, 128k (sold)
83 300D, 314k (sold)
79 300TD, 266k (sold)

Share your knowledge -

Wayne

I will translate it for you but I won't be able to do it until this weekend or maybe monday because I have a busy week now, but don't worry, you'll get it.

In essence, common rail injection is very much like electronic fuel injection for gasoline engines.

A feed pump at the tank pushes diesel fuel under low pressure to the engine compartment. At the engine compartment, there is another pump which produces several thousand psi of pressure. This high pressure fuel is distributed to an electronic or solenoid injector at each cylinder.

By using a crankshaft and camshaft position sensor, the ECU determines the time at which the injectors should fire, at which time it will energize the solenoid in the injector--just like a gasoline engine.

In order to control combustion noise and vibration, the ECU pulses the injector and injects the total quantity of required fuel over a period of time. This greatly reduces the noise level, and calms the engine's vibrations.

This system allows the advantages of indirect/prechamber injection (slower combustion) to be applied to direct inject engines--thus eliminating the inherent thermal inefficiency associated with indirect inject designs. The result is a clean, quiet, smooth, and extremely economical diesel engine that has a substantially higher specific output (more HP and torque).


-Joe G.

Awesome - it sounds like common rail is an alternative method of fuel introduction that provides similar benefits to indirect method and takes it a step beyond.

Question - How does common rail method compare to TDI method that VW uses? I imagine each has it's advantages and dissadvanteges?

__________________
04 GMC Yukon XL Denali, Black, 12k
02 New Beetle, TDI, Reflex Silver, 24k
89 300TE, Arctic White, 214k

90 300E, 142k (sold)
87 300TD, 128k (sold)
83 300D, 314k (sold)
79 300TD, 266k (sold)

Share your knowledge -

Wayne

Rougly said: the common rail method uses one injector pump, one *rail* which holds the pressure, on that rail, injectors are attached (directly or with injection lines), they are electronically activated so their injection point may be adjusted electronically, in opposition to the conventional method which has one and only injection timing.

Other methods (vw?) use a pump for each injector, so it doesn't use one (common) rail..


difference is that in the second method, there is not that much pressure involved in one single rail and the pressure and timing are regulated by the pump and electronic injectoractivation.. in common rail, the rail is constantly been held at a certain minimum pressure.

if the main injector pump fails in a common rail method; you are stranded, in the other method, your car will still be able to run if electronic engine management doesn't interfere and shuts down because of the engine not running smooth...

Greetings

Thanks Blackbenz - I am getting a feel for what some of the "old diesel" owners mean when they say modern diesels are getting more complex. I suppose only time will tell if "weekend" mechanics will be able to stay with the technology. If modern gasoline/petrol engines are any indication, my experience is they require very little service beyond fluid changes and, when something is amiss, designed-in diagnostics seem to help.

__________________
04 GMC Yukon XL Denali, Black, 12k
02 New Beetle, TDI, Reflex Silver, 24k
89 300TE, Arctic White, 214k

90 300E, 142k (sold)
87 300TD, 128k (sold)
83 300D, 314k (sold)
79 300TD, 266k (sold)

Share your knowledge -

Wayne

I am not sure how the VW TDi has been revised, but originally it just used a simple electronically controlled Bosch rotary injection pump. The pump was configured to fire a small "pilot" injection, which quietly started the combustion process. A split second later, the pump would inject the remainder of the required fuel.

This 2 stage injection process greatly reduced the noise and vibration that was normally associated with direct injection. An ECU controlled timing advance, idle speed, fuel shutoff on decel, etc.


-Joe G.

Xn6guy:

Sorry, I didn't know for sure the second method was used by vw or not, is the process you discribed one feature of either of both mentioned methods or is it simply a third one?

Wayne:

No problem. As a matter of fact, my mechanic started as a weekend mechanic and he has his own shop now but he doesn't has a specialty in one or more brands, for some errors, he says, you have to have access to brand-specific diagnostic computers, they have a much wider variety of error codes/diagnostic functions and maintenance/finetuning settings than the in-dash-display which is in most cases only useful for minor errordescription or resetting maintenance intervals.

The original VW TDi system that I described is not a common-rail system.

However, VW may have revised their TDi lineup recently to include a common-rail injection system, I do not know for sure.

The original TDi used an electronically controlled mechanical injection pump (rotary style). The injection process was divided into 2 parts--a small "pilot injection", and the primary injection.

Modern Common-rail systems used by Peugeot, Citroen, Mercedes-Benz, and BMW employ multiple injections in order to make the combustion process as smooth and quiet as possible.


-Joe G.

I work in the UK recovery industry if you went out to a diesel maybe someone put petrol in the tank, (which is very common) or something like that it was straightforward to fault find (fixing it was a different matter )

Now with common rail 'you have a warning light on sir, sorry dealer! '
Also in the good (bad?) old days when someone put the wrong fuel in, it was tank drained, refilled with diesel and off they went. the common rail diesels are not very tolerent to contaminated fuel and even a small amount of petrol can destroy the high pressure pump £££££ or $$$$$ !!