Thread: Diesel with LPG kit??

Originally Posted by lambrover

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.

no quite correct but 1/2 the story. Cat developed the HEUI injection at a time when mechanical injection was the norm. so in one way you could call it a transition system, or the basis for modern common rail systems.

tghe elecrical/ ecu side of HEUI is practically the same as modern common rail systems today. a few little differences but there is not much in it. it is the ecu that controls the injector patten or number and timing of injections.

the real difference is in how the Diesel pressure is produced. in a common rail system the diesel pump produced the pressure and the rail is always under pressure.

in the HEUI, the diesel pump is low pressure, say only about 7-12 psi. the actual injection pressure comes from a second Oil pump, that takes oil from the sump at high pressure, this oil is pumped ver a rail to the top of the injectors. there is a piston eltrocly fired like normal. but the piston being much bigger Dia than the diesel injectors piston increases the pressure again

the pressure from the dedicated oil pump and the injector pistons produce diesel pressure or injection pressure, many times higher than a common rail system.

Originally Posted by komaterpillar

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!?!

your thinking is correct, the 2.2 puma has a heat exchanger in the block to cool the EGR gasses before it enters the inlet. that's 1 example

Originally Posted by 85 county

no quite correct but 1/2 the story. Cat developed the HEUI injection at a time when mechanical injection was the norm. so in one way you could call it a transition system, or the basis for modern common rail systems.

tghe elecrical/ ecu side of HEUI is practically the same as modern common rail systems today. a few little differences but there is not much in it. it is the ecu that controls the injector patten or number and timing of injections.

the real difference is in how the Diesel pressure is produced. in a common rail system the diesel pump produced the pressure and the rail is always under pressure.

in the HEUI, the diesel pump is low pressure, say only about 7-12 psi. the actual injection pressure comes from a second Oil pump, that takes oil from the sump at high pressure, this oil is pumped ver a rail to the top of the injectors. there is a piston eltrocly fired like normal. but the piston being much bigger Dia than the diesel injectors piston increases the pressure again

the pressure from the dedicated oil pump and the injector pistons produce diesel pressure or injection pressure, many times higher than a common rail system.

I know HEUI was pre common rail, and I do remember what you are talking about, an intensifier piston in the injector, I think it was called.

As an apprentice we rebuilt a couple of CAT 3126 marine engines.

Originally Posted by lambrover

I know HEUI was pre common rail, and I do remember what you are talking about, an intensifier piston in the injector, I think it was called.

As an apprentice we rebuilt a couple of CAT 3126 marine engines.

yes thats the one, very high oil pressure, about 2000-4000 psi. then the added "intensifier" as you call it. a facter of 8mm2 over 0.4mm2 ( of the top of my head)


Ford power, Isuzu also used in the the 3ltr jakaroo etc. but that motor was a bit problematic for a number of reasons

AHHH CAT 3126 shove one of them in a 130 with an AT545 behind it.

I loved the sound of them spooling up

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. 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

I dont know that much about engines, but doea this mean that peak cylinder pressure is increased? And if so, what effect would that have on the head, valves head bolts etc?

Komaterpillar, did they give any info on cylinder pressures? From what ive read here and elsewhere, it doesn't seem as though it's the EGT is causing problems, but rather problems with the head.

Like I said, I don't know that much about the ins and outs of motors and whats good or bad as far as fuel mix and egr etc. Just wanting to learn a bit more.

Cheers

Dan

So gentlemen if the EGR on a 2.7 TDV6 is blanked off does that Lower or increase exhaust gas temperatures?

Originally Posted by TerryO

So gentlemen if the EGR on a 2.7 TDV6 is blanked off does that Lower or increase exhaust gas temperatures?

lower, but having said that the valve will only be open on light throttle at light cruising speeds. it will be closed at high loads when EGTs clime. so on a system like the early 2.7 you would not notice much