New take on an old camshaft

[Powdermonkey]

Folks- I'm a bit of an engine geek, and less of an electronics geek.  I sure appreciate those folks who share knowledge about AVR's and capacitors.  I love to learn...

So...in thanks, I post my latest findings regarding the old listers and lister clones...

If you scour the internet about injector timing for slow-speed Diesel engines, you'll find a few articles published by MIT and some "foreign" universities about optimization of injector timing.  And they're using Listeroids in those tests.  Those articles are by-and-large consistent in optimization of standard diesel products in these engines. 

The magic number is 27-degrees.  Sure, I'll grant you that the advancement optimization does change with load and RPM.  But...18-to-20 degrees consistently fails comparatively poorly to this 27-degree number. 

So, being I am who I am, I decided to get a piece of correct alloy round-stock (not from Habib's scrap bin...), and re-cut my entire cam location.  I mapped everything out on the original cam, and cut a new one.  BUT...I placed the fuel pump cam locator pins 3-degrees advanced from their original location.  As cams go, that means I've essentially advanced the "start" by 6-degrees of engine rotation. 

I do use the technique of using a spare injector, placed directly over the flywheel AT Top Dead Center to define my "start" location.  Works well, in my humble opinion.  The fuel pattern on the flat face of the flywheel defines true "injector timing".  I'd sure like to hear from knowledgeable folks if this method is of poor judgement...On my twin, I've got both cylinders timed for "right about" 26 degrees BTDC. 

Why not simply increase the throw on the cam follower bolt?  Well, by my measurements, it seems to me that I'm coming dangerously close to bottoming out the fuel pump, and potentially wrecking parts and pieces, when I attempt to advance past about 20-degrees.  Likewise, I don't know that by simply changing the length of the cam follower, that you truly do "much".  The "start" essentially remains the "start", and the "peak" essentially remains "the peak".  You've JUST got more throw.  But...if you change the location of that fuel pump cam, then one is certainly "doing the do". 

Results indicate less fuel consumption for same load, less smoke (for sure), and satisfaction (so far) for the monkey who turns the wrench.  Also, certainly less "dripage" from the mufflers. 

So, if you KNOW about these things, I'd truly like your input.  If you "think" "that's not how the engine was designed"...maybe not so much.   

[cobbadog]

It's out of my fild of expertise but admire your attempts at making improvements. Do you think the torque would have changed or HP rating?

[Powdermonkey]

http://www.ijetsi.org/uploads/ijetsi_02__62.pdf

This PDF references BSHP.  But given constant RPM, there's a direct relation between torque and HP. 

[Willw]

Being something of an engine geek myself I find this article very interesting... thank you for sharing.

I may be missing something but I believe the engine from the test paper is a Petteroid, and if I understand mechanical injection, more RPM requires more injection timing advance.

So the 20 degree figure may be right for a Listeroid turning around 650 RPM, but it would likely be retarded for a different engine turning 1500 RPM.
I would expect that a Listeroid turning 650RPM would have quite a knock with injection timing set at  27 degrees BTDC, but I've never tried it so I don't know.

Most of what I've learned is thanks to members of this very website, that being said I've never heard of a Listeroid turning more than 1000 RPM.

I am very interested to know whether your engine is a Listeroid, Petteroid or something else, and what RPM you are turning yours which may reveal to us whether 27 degrees is indeed a magic number.

[Powdermonkey]

WillW- Thanks for taking interest.  When the engine was new, it smoked (white) at 20 degrees BTDC.  I attempted to advance the fuel pump timing, by way of increasing the length of the cam follower.  I came to believe that I was getting dangerously close to overdriving the fuel pump.  Likewise, I realized that by lengthening the cam follower, I was really only potentially STARTING the fuel pump sooner in the stroke.  But the peak remained the peak.  No change to the peak.  Thus, my endeavors to create a "true" advancement in fuel pump timing, beyond the 20-degrees. 

I'm now running the listeroid twin (16-2) at 25-26 degrees BTDC.  Engine speed is a confirmed 680 rpm.  At both high and low compression (I've got the change-over valves), the engine purrs along, with no sounds of knocking.  White smoke is gone.  Drippage from the mufflers is gone.  While not scientific, I am sure my fuel consumption has decreased. 

I'm pulling a load (at maximum) that approaches 3/4 the hp rating of the engine, through a 22 KW generator head.  YES, I know the head is oversized for the engine.  Matters not.  The added inductance if the 22 KW head is beneficial to me, for inductive motor start-ups.  I monitor the frequency coming off the generator, and at no time has the 16/2 faltered outside of the 63-to-59 hZ I require. 

[cobbadog]

Sounds like a good outcome for you. If no fuel dripping from the muffler that alone would be a fuel saver. All the detail you have described is outside of my knowledge because I never have had to delve into this side of a diesel engine. Maybe one I will and usually with me it is being hands on that teaches me best.

[Willw]

Powdermonkey - +1 on the good outcome, and going out on a limb to prove and explain your theory clearly. Advancing the cam lobe does make sense as opposed to just changing the start of injection

[dkmc]

Very interesting post, thanks for sharing this info.