Thread: Diesel with LPG kit??

When i went to trade school we were taught EGR was to raise intake air temps. I remember this cause at the time it baffled me as to why you would cool intake air with a long intake tract and gigantic intercooler only to reheat it with exhaust gas!?!

I worked for a transport company that ran gas fumigation systems on their trucks, running 620 signatures. The mob that developed the systems came out and did a training day with our workshop. The gas was injected pre-turbo wich gave a more uniform mix. This system had egt feedback to its own ecu and also was on a boost switch so gas was only switched on under load (can't remember what pressure).
Anyway long story short, they showed us a heap of thermal imaging of the exhaust side of the head and inside the exhaust ports. Apparently the introduction of LPG made for a more complete and quicker burn INSIDE EACH POT and the flame front from combustion now didn't extend out into the exhaust port so far hence lowering egt's. Apparently this was also one of the reasons for gaining more power with better econemy as more energy from the fuel was being utilised within the cylinder before the exhaust valve opened rather than being sent out through the exhaust as heat. The quicker burn also apparantely made peak cylinder pressure sooner after the diesel injection occured so more of the energy was available with the piston higher in the bore so it then utilised more of the energy available before the exhaust valve opened.

Anyway thats just what i remember from the course we did with the gas system developers

Well going from what learnt everyone is on the same page it's just our face to face verbal skills are not matched by our computer typing ones . Pat

Even I screwed up, it's supposed to be ''from what I learnt''. Pat

Originally Posted by komaterpillar

I worked for a transport company that ran gas fumigation systems on their trucks, running 620 signatures. The mob that developed the systems came out and did a training day with our workshop. The gas was injected pre-turbo wich gave a more uniform mix. This system had egt feedback to its own ecu and also was on a boost switch so gas was only switched on under load (can't remember what pressure).
Anyway long story short, they showed us a heap of thermal imaging of the exhaust side of the head and inside the exhaust ports. Apparently the introduction of LPG made for a more complete and quicker burn INSIDE EACH POT and the flame front from combustion now didn't extend out into the exhaust port so far hence lowering egt's.

90% correct. diesel is only about 85% burnt in the combustion process. so its not heat out though the valve its unburnt fuel out the valve. fuel that is still burning . it is this still burning fuel that raises EGT. fuel finds itself in cold-spots within the chamber it is this fuel that is slower to burn or is not burnt and passes out though the valve.
it is the burning of this fule that gives more power. that's why if you add 1 Kw's worth of LPG you get 3 Kw of more power ( for example)
so not heat fule. a small detail.

Apparently this was also one of the reasons for gaining more power with better econemy as more energy from the fuel was being utilised within the cylinder before the exhaust valve opened rather than being sent out through the exhaust as heat. The quicker burn also apparantely made peak cylinder pressure sooner after the diesel injection occured so more of the energy was available with the piston higher in the bore so it then utilised more of the energy available before the exhaust valve opened.

Anyway thats just what i remember from the course we did with the gas system developers

Good

CAT went in a different direction, bi turbo, throttle body's, and extremely high pressure oil over diesel injection. IE no EGR valve

Originally Posted by 85 county

CAT went in a different direction, bi turbo, throttle body's, and extremely high pressure oil over diesel injection. IE no EGR valve

Are you referring to HEUI injection.

From memory these injectors where able to inject multiple times (ECU controlled) so rather than dumping bulk fuel in one injection it was broken up into multiple injections, this aloud the first smaller injection to ignite and build a flame front, the next injection was bigger and ignited quicker as it was assisted by the first injection which would already be lit. The last injection was a very small amount of fuel to reduce combustion chamber temps.

Now with even newer injectors and common rail systems the injection metering can be broken up to 4 or 5 separate injections.

Is this correct? or have I been led up the garden path on that as well.

Originally Posted by 85 county

diesel is only about 85% burnt in the combustion process. so its not heat out though the valve its unburnt fuel out the valve. fuel that is still burning . it is this still burning fuel that raises EGT. fuel finds itself in cold-spots within the chamber it is this fuel that is slower to burn or is not burnt and passes out though the valve.

Isn't that what i said? I said the flame front extends out into the exhaust port. What does a flame front need? Fuel. Implying that there is unburnt fuel exiting the pot still burning. Why the need to correct me on something and then give the exact same information in your answer?