8v71 govenor

[bevans6]

To me droop makes a lot of sense intuitively.  At no-load, the governor is shutting off fuel at the injectors to limit speed, and the injectors are only delivering minimal fuel to develop the quite small power needed to overcome the internal load of the engine - not much.  At full load the injectors are delivering full fuel right up to the point where they back off to limit further acceleration of the engine, hitting the governed limit.  Totally different operating conditions.  The dyno will pull down the engine speed as far as it can with increasing load (that's how it measures the torque twisting the brake load cell) until it reaches a balance point where the load and the power equal each other, at the governed RPM.   I suspect that if you are truly loading the engine fully, it will not be accelerating and so the governor isn't what is limiting the RPM, the dyno brake is.  For full power the governor isn't limiting speed by backing out fuel.  At less than full power, the injectors can deliver additional fuel to reach a higher RPM so the governor is what is limiting speed.  My dyno experience is with gasoline 4 stroke race engines, mind you... 

How do you measure droop at 425 hp on a 525 hp engine?  Lower RPM?  Set the engine at a speed, and increase the dyno brake to see what maximum power you can pull at that speed?

[Geoff]

The short answer is that you run the DD2stroke on the dyno at your top no load RPM and increase load until you are at HP for the size injector according to the book.  The rpms tell you what the actual droop is.  You also use a screwdriver in the buffer screw hole and check travel every time you increase the load until at full load the screwdriver bottoms out pushing against the governor link.  You have to be careful not to increase the load past the advertsed HP after the linkage bottoms​ out to get an accurate droop


--Geoff

[bevans6]

So you run it at max no-load, load it to the setting you want to achieve based on specification of the engine, and see how far it droops when you achieve that HP.  If you have an engine that could reach 525, and you only load it to 500, it would droop less and stay closer to max no-load.  If you loaded it to 550 you would pull it down farther and have more droop (if you could load it that high).

Race engine guys do similar things to get great HP numbers.  What we did is sneak up on it from below, run the engine at roughly 500 rpm steps from say 5,000 to 8000 rpm, and bring the load up to where it balanced with the engine at full throttle at that rpm.  Another way to do it is to let the brake pull the engine down from a high rpm to a low rpm.  It takes more brake torque to pull the engine down than to just barely balance it, so if you want a really big number you pull it down hard and boom, 15% more power than you actually have.  But it's on a computer readout, so it must be right...      Depends if you are selling engines or winning races. the only dyno that really counts is the back straight on the track, or that hill in a bus...

[luvrbus]

The 8v92 wasn't done on a water brake dyno, it was a new computerized Eddy Current dyno 31 sensors and told all

[Geoff]

The 8v92 wasn't done on a water brake dyno, it was a new computerized Eddy Current dyno 31 sensors and told all

So if Eddy Current told all,  what was the cause of your 125 RPM power droop?

--Geoff

[luvrbus]

So if Eddy Current told all,  what was the cause of your 125 RPM power droop?

--Geoff

It tells and shows you on the screen or you print out a 6 ft long graph where the droop begins it is not quite smart enough to tell you how to fix or stop the droop that is why I asked the brains here and other places.I would like to have 0 droop   

[Geoff]

The governor weights​ might​ not be equally adjusted.  If you use a screwdriver to spread the weights​ to set the governor gap, check/adjust one weight, bar the engine over and see if the other weight is the same gap.  A lot of times they are not equal and you have to pull the governor, pull the weight assembly off, check for slop, and lastly grind the stops so when you spread the weights they touch the spool exactly the same.  Most shops would not bother.  Also if you need the bronze bushings for the weights I should have some left.  I am going by Kingman Thursday morning and like to stop and visit. Call me at 928 771 0045.

--Geoff

[luvrbus]

Geoff, I will give you call right now I am out of service anyways a friggn handle came out of a grinder and got loose and I look like have a zipper on my hand

[Utahclaimjumper]

  A sure sign of OLD AGE!!>>>Dan

[kyle4501]

You ain't old if people laugh when you fall down.

If they come running over . . . . you are officially old