What I learned this week

David G · Oct 26, 2018

I worked on fuel valves and electronic governors for natural gas engines this week. It really helped that I did the fuel injection on the MH a few years ago, and worked with the vendor on the fuel injection in MN last year on the natural gas engines.

The fuel valve is locked at a certain position during cranking, much like duration on an injector. You pick a small position, and keep raising that position until it fires. On the natural gas engines you have to purge the engine out between attempts so you do not leave all that gas in the manifolds and cylinder, so it does take a while. You then ramp the fuel valve open until it idles at the right RPM, then allow the governor to take over once it is warmed up and can go online. The compressor is open to the discharge and has a bypass valve so it stays full, the inlet valve is opened while the bypass valve is closed to load the compressor.

It took about a day of trials to get the first engine running, then we knew where to put the settings.

These do not have temperature compensation, so I might need to go back this winter and open up these settings for cold weather.

David G · Oct 26, 2018

Some of these have a throttle plate for air control, and others just control the boost to maintain air fuel ratio. The turbo's use compressed air to spool them up and provide boost until they are working.

We sometimes retard the timing about 10 degrees to get enough heat in the turbo to provide boost so there is enough air. The engines will detonate under these rich conditions of too little boost. Once the engine is working, there is plenty of energy to spin the turbos. It is a balancing act to get the engine to produce enough torque to load up with the timing that slow so it can produce its own boost, then you can advance the timing.

centash · Oct 26, 2018

You got a cool job!Ben

David G · Oct 26, 2018

I do have that, big iron rules.

UncleTom · Oct 27, 2018

Just like setting the carb on engines so to speak, only electronicly. You do have a good job.

rlp in Co. · Oct 27, 2018

I see you have it backwards again! A lean condition is what causes detonation. Always start out rich to protect an engine. More boost leans the mixture so you have to add more fuel as the boost increases. In the old Cummins engines the fuel was increased with an Android valve as the boost increased. Of course with a diesel engine they never detonate, they just get better economy when they run lean. In modern gas engines the fuel mixture is set rich like maybe 12 to one, then the oxygen sensor leans out the mixture so even if the oxygen sensor fails the engine will just run a little rich and won't be destroyed. Those big engines might need to be backed off to 5 degrees or even 0 degrees at start up. On my Toyota pickup, the timing is set at 0 degrees. First time I have seen that but that's what the book says.

westga · Oct 27, 2018

David are these engines hand cranked or cranked by computer? I like to follow your post on these engines. Also when cranking the engine is the station online or off line?

The Clarks (HBA 5T) and (HLA 10T) started with 28 degree retard to help the jet air spin the turbo up and would run 0 tdc at minimum speed until engine loaded. Not an engine made that can detonate like a Clark.

David G · Oct 27, 2018

RLP,

These are 2000 -10000 HP engines, when you know what you are talking about, please join in.

What I learned this week

David G

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David G

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centash

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David G

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UncleTom

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rlp in Co.

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westga

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David G

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