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[Webby the Bear]

As above, doing some revision for my up and coming exam. Usually my theory notes are packed but it seems I have either misplaced this info or I didn't type my notes up 

Anyhoo, can some kind soul tell me the following in PSI please:

1.) Pressure of diesel between tank and injection pump (I believe it's low like 4 psi???)
2.) Pressure of diesel between injection pump and injectors (very high iirc)
3.) Pressure of diesel sprayed from injector in to the combustion chamber

4.) Pressure of petrol between tank and injectors
5.) Pressure of petrol sprayed from injectors in to the combustion chamber.

Cheers lads

[martin42]

Bring your laptop sunday,will put autodata on it and torque wrench,no idea on the fuel pressure tho 

[Webby the Bear]

Bring your laptop sunday,will put autodata on it and torque wrench,no idea on the fuel pressure tho 

nice one mate, cheers. which torque wrench do you need mate?

[Marks DTM Calib]

A bit of info as there are no hard and fast rules, all in Bar as that is what you will find speciifed these days (as Psi in the design and engineering world is long gone....thankfuly)


1.) Pressure of diesel between tank and injection pump (I believe it's low like 4 psi???)

Its very dependent on the engine/model e.g. if its a VP44 (and many other setups e.g. CAV's etc) type application then there will be a slight vaccum as there is no lift pump in the tank. Others such as the Omega 2.5TD havea  lift pump that runs during cranking and then shuts down.

2.) Pressure of diesel between injection pump and injectors (very high iirc)

Again, VERY application dependent and will often be linked to the dynamic compression ratio and many other factors, 240 bar is pretty typical pop pressure in my experience although some older setups are less with common rail systems running around the 400+ bar mark up to the order of 1800 bar for the very latest Gen 3.

3.) Pressure of diesel sprayed from injector in to the combustion chamber

Enough to cut your finger off ! (no joke!). Reality is that at the point it exits the injector it will be close to the pop pressure or rail pressure.....the further from the nozzle, the less (obviously)

4.) Pressure of petrol between tank and injectors

Typicaly 3-4bar

5.) Pressure of petrol sprayed from injectors in to the combustion chamber.

For a start, the only system that sprays the fuel actualy into the combustion chamber is a direct injection setup where the pressure is 25-around 200bar dependent on the system and operating conditions.

For those that spray into the inlet (usualy the back of the valve), its as per the fuel pressure e.g. 3-4bar at the point it exits the nozzle

[Andy B]

....

3.) Pressure of diesel sprayed from injector in to the combustion chamber

Enough to cut your finger off ! (no joke!). Reality is that at the point it exits the injector it will be close to the pop pressure or rail pressure.....the further from the nozzle, the less (obviously) ....

Isn't it around 100+ BAR?     

[Marks DTM Calib]

As above, depends and is normaly slightly more (older system possibly about that) , if its common rail then its much much higher...

[Andy B]

..... if its common rail then its much much higher...

It's not something you want a crack/split in then 

[Webby the Bear]

Thanks guys for the info. sorry didnt reply but was busy getting a year older over the weekend

somebody quoted in class that 80 bar was enough to split you in half. lol