problem with finding idle setting

[Sphere]

So my Hatz engine ended up on the bench and got modified to control the fuel pump instead of the governor. In practise this works really well. You can ride around and accelerate at will. Unfortunately there's also a downside. It seems rather impossible to find a good (comfortable) idle setting. So now the question is: is it at all possible to have fine grained control over the amount of fuel that passes through the pump, and would it then be a problem with the modification, or is it not feasible to set rpm through the fuel pump?

It seems like it would idle at 2000 rpm (at a guess) and when we would release the tension on the throttle cable it would still run at 2000 until a fair amount of twists of the idle screw passed, then suddenly it would die and stall, unless you rapidly reversed the process or gave a firm twist of the throttle. Unfortunately it's not an issue with the cable being stuck. Any ideas?

http://www.youtube.com/watch?v=Bl_PwmQtvDE

[sbrumby]

Can i just ask one question, why would you want to elimiate the govenor. Haveing one gives a built in cruise control. that all normal petrol bikes just dream about. Mine is the best feature of the bike.

[IgorVigor]

I may be mistaken but its so the throttle is a bit lighter

The governor would keep the engine idling a lot lower, as it would constantly be adjusting the fuel pump.

when you bypass it, you have basically done away with the low speed...

2 ways I can see of you getting it back...

1 - work out a way of getting the governor to control the fuel at low/no throttle opening and then you take control once its past 2000rpm

2 - revert back to using the governor...

if you decide to do the second, there is a way of making the throttle lighter...
modify your linkage so its longer as that will decrease the pressure required to twist the throttle...

good luck...

[Nanko]

One reason to do this mod was a lighter throttle
But another was to make accelerating less "digital"
a small movement of the thottle would activate
the governor in such way that the injection pump
was set on maximum volume.
We were hoping to improve fuel economy with by-
passing the governor.

[IgorVigor]

I see what you mean...

the governor acts to get the engine to desired RPM as quickly as possible.

as I said then, the only thing I can think to try is that the governor controls the engine under say 2000rpm and then the manual throttle bypasses it past 2000rpm

[Nanko]

as I said then, the only thing I can think to try is that the governor controls the engine under say 2000rpm and then the manual throttle bypasses it past 2000rpm

Agreed , have to find a way the governor works for idle and for max rpm.
Maybe a solenoid , activated with a switch attached at the throttle lever.
Twistgrip in idle position energizes solenoid and puts governor on low rpm

[IgorVigor]

just watched the video again.

I take it the throttle lever is the one on the right (outside the engine) [lever 1], and the governor is the one of the inside [lever 2].

both turn the springed rotating lever at the bottom of the screen. (fuel pump I presume) [lever 3]

unless I am the wrong way around, [lever 1] on the outside doesnt move [lever 3] far enough down to idle under 2000rpm...

[Nanko]

just watched the video again.

I take it the throttle lever is the one on the right (outside the engine) [lever 1], and the governor is the one of the inside [lever 2].

both turn the springed rotating lever at the bottom of the screen. (fuel pump I presume) [lever 3]

unless I am the wrong way around, [lever 1] on the outside doesnt move [lever 3] far enough down to idle under 2000rpm...

Correct

But with the twistgrip it is possible to set idle , problem is rpm is not stable when the throttle is
kept in the same position , or it stalls , or it runs at ~2000 rpm

[IgorVigor]

ah right, I understand better now...

I was watching the governor and fuel pump on my Petter AVA1, and when idling the governor arm is always adjusting the fueling...
when its got a constant load (alternator etc) they stay in one position...

good luck either way...

[John]

Hi Sphere. I'm not really sure what is was that you were trying to achieve originally. If the throttle grip is too heavy, then are you perhaps using too strong a spring rate on the governor lever, to overcome its resistance too quickly?
Since a diesel has no throttle, the only speed regulation it has is through the governing of the injection volume. Remove that, & you have an engine potentially ready to run away to destruction as soon as the load is removed. In side stepping the governor, effectively, you are inducing maximum fuel rate at all times above idle, even when cruising at steady speed, which is very wasteful & smokey.
When you open the twistgrip, you apply a force to the spring attached to the governor lever. If the engine speed is lower than the one you want to achieve, the flyweights of the governor offer little resistance, & injection volume is increased. When the rpm has attained the level appropriate to the force applied by the spring, the faster spinning flyweights of the governor then apply an equal force against the spring, & injection volume is held steady & in check. With the twistgrip held steady, if the load on the engine causes it to slow, the governor flyweights will move in slightly, causing a compensatory increase in the fuelling to try to resist the load, & get the engine rpm up back up to the level at which the spring force has set it. This is achieved automatically. If, on this steady twistgrip setting, you then head downhill, & overun causes the rpm to rise, the governor flyweights will move out further, & overcome the force applied by the spring, reducing injection volume automatically to try to restrain the engine speed down to that which has been set. A perfect set up! Why mess with it?
This is also the reason that manufacturers give 2 ratings for an industrial engine; Continuous power, which is the power the engine generates when rated speed is reached, with just sufficient fuelling to sustain the engine at that speed, - & maximum or overload power, which is achieved at the same 3600, but against sufficiently heavy resistance that the governor is forced to throw all the fuel it can muster into the cylinder. This is also why it is false economy to overgear our bikes. If the engine cannot reach its rated 3600 rpm in top under normal level road conditions easily, then the engine is continuously on overload condition, & economy will suffer. By allowing the engine to comfortably reach its rated speed in top, the governor can still restrain the fuelling even at maximum revs, thereby improving economy even with shorter gearing.

[Sphere]

Hi John. Thanks for your elaborate write up. I understood it the other way around, that the governor will cause the injector to deliver max fuel when not at desired rpm, and fractional fuel delivery would only be at that rpm. The idea was that this would be wasting fuel and it would be better to control the fuel pump directly.

Sadly the mod failed, but now that the throttle cable is attached to the governor lever, it isn't heavy on the wrist at all. All that's left to do is restore it to the original setup. I'm sure it will be fine after. You are right about overrevving, it's 2200 idle and 4100 max rpm or something. I suppose this is a clear cut example of "don't fix what isn't broken"