Diesel injector pump throttle control query

[me3@neuralfibre.com]

When you move the throttle on a diesel, you adjust the rack in the injector pump. This varies the amount of fuel delivered to the injectors, possibly in combination with several other inputs, both electrical and mechanical.

The question is
Does the fuel delivery rate get adjusted as "cc per stroke" or "cc per minute"?

With the design I understand of a diesel pump it should be "per stroke", but this means that if you drop back a gear, then as the RPM increases more fuel/minute is being delivered, increasing the effective throttle position. That doesn't seem right to me.

Thanx
Paul

[dumbdunce]

With the design I understand of a diesel pump it should be "per stroke", but this means that if you drop back a gear, then as the RPM increases more fuel/minute is being delivered, increasing the effective throttle position. That doesn't seem right to me.

Thanx
Paul

on your 1HZ it's almost all mechanical, and yes it's more or less volume per stroke. of course you use more fuel in a lower gear if everything else is equal. the main other contributor to injection volume is the HAC or boost compensator, this varies the fuel delivery with the manifold pressure. the other major contributor to actual injected volume is the condition of the injector; a worn injector passes a fair bit more fuel, with inaccurate injection timing and crappy spray pattern, than a good one which is why exhaust smoke is most commonly caused by bad injectors.

think about it some more, you've more or less got it figured out.

[Rilux]

Hey, just passing through and noticed this...I don't really understand the question...

It would have to be measured by stroke tho? If you move your rack, basically you're moving the helix position (or metering valve), thus enabling you to have a shorter or larger effective stroke. The reason the RPM picks up if you drop it back a gear, is because of the gear set in the gearbox, and the engine speed picking up because of the ratio (because inversely this affects camshaft speed in the pump). Also depends on compensator's too as dumbdunce said..

I don't know if I'm on the right track or not me3, but would be happy to talk about it

[me3@neuralfibre.com]

That matches my thinking. But if the RPM increases then the cc/min delivered increases meaning more power in the lower gear. Normally if you shift down (I'm thinking auto to keep throttle position constant) you would expect more torque due to the ratio change, but approximately the same power (depending on engine power curves/rpm). I mean if I drop it back from overdrive to 3rd at 100km/hr and 2200rpm it doesn't start to accelerate away. With more fuel per second it should if the fuel is metered per stroke.

Mine is not boost compensated. I know there is some RPM compensation to prevent overrev, could this be tied in?

Paul

[Rilux]

You're actually at a lower rack position when you are in higher revs. There is a governor in there, controlling your rack position relative to your revs. Basically, at higher revs, a set of balance weights come out, push against the governor spring, and push it out of fuel. (Due to inertia etc. you don't require high fuel.) So basically, when the vehicle comes under load, the revolutions drop, the balance weights drop out, governor spring action takes over, pushes the rack into fuel, which then brings your torque up.

Basically, using Caterpillar and Cummins terminology:

You have Maximum No Load Speed and a rated speed, and rated speed is always about ~300rpm under your Maximum No Load Speed - rated speed is the highest torque.

So basically rack position at rated speed could be 11mm, and at Maximum No Load Speed, it could be anywhere from 6-7mm.

I hope this helps.

[Dzltec]

A rack is only fitted to inline pumps. If we are to talk about pumps that are on a 1hz, then they have a metering collar on the rotor.

Your throttle shaft externally is connected internally via a spring to the governor lever which connects to the collar. Your foot changes throttle position, this is setting the tension of the throttle spring so that it takes more revs for the flyweights in the governor cage to overcome spring tension. Once this happens your fuel delivery is decreased.

Going from 1/2 to full throttle at a speed lower than what the weights would flyout on doesn't alter fuel delivery, it only alters the revs at which fuel delivery is reduced.

I will post up specific fuel specs to show the fuel curve tomorrow when I have a test plan in front of me. In most other cases all pumps work the same, they are relying on a balance of spring tension vs governor weight movement to control fuel. No pumps that I know of have a direct coneection from throttle shaft to fuel delivery.

All fuel delivery is measured in mm3 per 100, 200 or 1000 strokes.

Hope this helps

Andy

[cruiser60series]

i know i have a very primitive understanding but.. i always thought that your foot tells the governor (and the governor alone) to increase/decrease fuel to meet the rpm the throttle "demands".

So putting your foot down doesn't directly add more fuel but tells the governor a certain demand of rpm and the governor works it's magic inside the pump to accomplish this by +/- fuel.

And also why use manifold pressure and hoses to link your right foot to the governor? why not directly to the pump with a cable or something? Is there some feedback situation with engine speed and air pressure. (my only experience is with a 2H)

tell me if I'm not right cause i'm quite curious about this stuff.

[Tapage]

Pretty interesting thread ..

The 2H IP have a rev limiter how it function ?

I know there is a fuel delivery adjust ( actually a nut ) that it's the same attached to HAC reducing or increasing the fuel at altitude ..



And you have other option to adjust it with advance or retarding the time ( I recently discover that it's posible in inline pumps .. ) that gives more kickoff aceleration but less long term ( end ) speed .. ( sorry for my underestanding about timing in Diesels )

I have my 1HD-T IP advanced more coz it's automatic tranny and the kick from stop it's pretty nice .. but my top end speed it's poor ( well anycase it's not a rice car .. and at 140km/h I'm pretty happy )

Comments .. ?

[me3@neuralfibre.com]

A rack is only fitted to inline pumps. If we are to talk about pumps that are on a 1hz, then they have a metering collar on the rotor.

Your throttle shaft externally is connected internally via a spring to the governor lever which connects to the collar. Your foot changes throttle position, this is setting the tension of the throttle spring so that it takes more revs for the flyweights in the governor cage to overcome spring tension. Once this happens your fuel delivery is decreased.

Going from 1/2 to full throttle at a speed lower than what the weights would flyout on doesn't alter fuel delivery, it only alters the revs at which fuel delivery is reduced.

I will post up specific fuel specs to show the fuel curve tomorrow when I have a test plan in front of me. In most other cases all pumps work the same, they are relying on a balance of spring tension vs governor weight movement to control fuel. No pumps that I know of have a direct coneection from throttle shaft to fuel delivery.

All fuel delivery is measured in mm3 per 100, 200 or 1000 strokes.

Hope this helps

Andy

So the throttle sets a balance point between delivery and RPM controlled by the govenor. Basically then you end up with a (close enough) effect of the throttle controlling cc/min as opposed to cc/sttroke.

ie. Assuming same load and throttle position, dropping back a gear increases RPM. More strokes / sec = more fuel per sec. BUT, the increased RPM throws the govenor out further which decreses the fuel delivery by about the same amount, resulting in a similar power output at a higher RPM.

That probably means the overrev govenor is seperate to the normal throttle govenor as their behavior would be different.

I would be interested in seeing the fuel delivery curves. Most i have seen are at WOT, whereas the behaviour would be quite different at 30% for example.

Paul

[Dzltec]

A 2h pump has what they call a combined governor. It uses a vacuum signal to contol idle and midrange, then a mechanical unit that controls maximum revs. When we are talking about vacuum we a talking about a signal less than 1.8"- 2" hg.

There is no seperate section for maximum speedin a 1hdt pump or any rotary pump. It all has to do with spring tension vs weight throwout, eventually weight throw out wins, this then cuts fuel back.

There are quite a few pumps for a 1hz. Here are the fuel delivery settings at full throttle speed is pump speed, ie 1/2 engine speed.

500rpm- 10cc @ 200 shots
1200- 11.7
2000- 11
2200- 8
2300- 4
2400- less than 2

There is only one setting for part throttle and that is set while watching internal pressure. The rest is idle settings, pressure and advance piston travel.

Andy

Just to throw a little curve, there are 2 governor systems, one is an all speed, the other a min max. They control fuelling in diff ways.