Common Rail vs Direct Injection *Diesel*

[CatonaPC©]

So after reading all this I get the impression manufacturers are heading down the CR path, not necessarily because it's better than PD, but because it's cheaper?

From what I read, emissions are not an issue as PD can be tuned to comply with future standards. But CR certainly appears to be a simpler approach.

[Transporter]

So after reading all this I get the impression manufacturers are heading down the CR path, not necessarily because it's better than PD, but because it's cheaper?

From what I read, emissions are not an issue as PD can be tuned to comply with future standards. But CR certainly appears to be a simpler approach.

You don't know what the future emissons standards are, so how do you know that the Unit Injector System can be tuned to meet the future emissions standards?

[CatonaPC©]

You don't know what the future emissons standards are, so how do you know that the Unit Injector System can be tuned to meet the future emissions standards?

True. What I am saying is that from all that I have read CR may prove the easier option to meet those standards. But I don't see any reason why PD can't be developed to meet future standards other than cost or complexity.

[Transporter]

True. What I am saying is that from all that I have read CR may prove the easier option to meet those standards. But I don't see any reason why PD can't be developed to meet future standards other than cost or complexity.

The reason is the limitation of the Unit Injector System.

Since the unit injector is camshaft lobe operated it cannot control fuel injection as well as CR system. In CR system the fuel rail (common rail) is pressurised by

a high-pressure pump (the radial piston pump on the cars) that pressure is generated independently of the fuel injection cycle. ECU in CRD system uses fuel

injector similar to the one in todays EFI cars and it can inject fuel onto the cylinder at any time which result in the better control of the fuel injection.

In the Unit Injector System it is the diesel fuel high fuel pressure, which lift the nozzle and fuel is injected (the same diesel fuel pressure like on old mechanical

pump system - only much higher). ECU uses the solenoid in the Unit injector for precise control of injection timing, quantity and pressure.


Somebody made the decision that Common Rail is more suitable at this time.
It is possible that The Unit Injector System can come back in the future, who knows, but the one thing I know that CRD has less soot from the exhaust when there is no DPF fitted.

[recalibrate_ecu]

Hi,
Also the early versions of the common rail could not pressurise diesel as highly as a pd injector. Howver, the common rail system is cheaper - hence the 1.9 dti engine found in the holden astra/ saab 9-3 and alfa 147.

More recently common rail systems have developed to inject up to 2200 bar - yes that is almost 32000 psi which will puncture a hole in your finger should you decide to place it in the way.
More commonly (except audi r15 tdi race lmp1) injection pressure are around 1600 -1800 bar.
So common rail can now inject at the same pressure as pd and is cheaper.
Hope this helps?

Or Volkswagen Audi Grupe

[recalibrate_ecu]

Before I start the process I will complete a diagnostic engine check to ensure your vehicle doesn't have any faults.
If for any reason you require the vehicle to be returned to the 'stock' map I hope to do this for a nominal charge of approx. $50.

[Shifter]

Interesting!

A proper comman rail diesel engine, opposed piston, turbo charged 4 cylinder J type Doxford. This engine was proably built sometime in the mid to early 60's but Doxford comman rail (6000 psi) diesel engines have been around since the 30's not new technology. Interesting to note that most high speed marine diesel engiens are all mostly comman rail dervivatives.