Interesting Timing info

[WrickM]

Mel, for the record thus far i have been talking about Waste Vegetable Oil not so much WMO. Even the diesel fuel t the pump only has a minimum cetane rating, and we are all aware that the quality of diesel can vary from pump to pump. Still we a trying to tune for the average diesel, and i am trying to tune for the average WVO.

The more i think about the pulse method the less valid it seems to be. it's simply a measure of when the fuel is injected and has nothing to do with when the power is actually being delivered by the fuel. Not only can cetane rating effect the timing, but engine wear and blow-by would make a major difference. if the engine doesn't have great compression than the heat needed to ignite fuel would be created later in the stroke. etc.

The length of burning is a good point.

As far as where you timing should be set using luminosity on each fuel while there may be some very small differences i believe they should all be the same. It's an issue of mechanical advantage vs engine wear. the most power from the fuel is delivered just after ignition (whenever that happens) and the engine seem to like that to be at 0-3atdc(using luminosity) during the crank revolution to create the most leverage on the crank without damaging the bearings.

so i agree that the only way to have a "perfect tune" is to tune every tank of whatever, but i do think an average tuning can be done for each fuel. switching between the two presents more problems.

 

[SLC97SR5]

I have a question regarding different fuels and timing...here is what I'm thinking:

PLEASE correct me...

Fuel with a lower energy content, kerosine for example would require advancing the timing to aid starting, regain some power and reduce gray chugging smoke at idle.

-And-

Fuel with a higher energy content, LSD or WMO requires retarded (factory spec) timing to prevent engine damage.

 

[FordGuy100]

Actually we calculated you needed to advance the timing more with ULSD as I think the cetane rating is higher? Went from 7.5* to 9.7* of timing with luminosity I believe.

 

[Sycostang67]

It's 9.7* with pulse, 0-0.5* with luminosity. I tried 9.7* with luminosity and it sucked...royally. Delayed throttle response and constant smoking, not to mention the motor sounded horrible.

 

[WrickM]

yeah 9.7 with luminosity in any direction would make an engine run like crap lol

SLC i am not sure how energy content plays into the equation. The cetane rating of a fuel determines when you want to adjust injection timing so that your ignition timing* is at 0-3atdc (luminosity). i.e. you want the fuel to burn at 0-3 after the piston reached TDC becasue that is when the most mechanical advantage is created. You don't want to go before then because ifthe fuel begin to ignite before the piston reaches TDC then the rotation of the crank if fighting the expanding gasses. that isn't good for the engine. So whatever the energy content of the fuel you want it igniting at that sweet spot of 0-3atdc.

*that's something i think people are overlooking when thinking about timing. That adjusting the IP is adjusting the Injection Timing, in order to change the ignition timing. They are by no means one and the same.

 

[SLC97SR5]

I guess what I'm getting at is that a fuel with a lower cetane rating requires advancing the IP to get drivability performance similar to a fuel with a higher cetane rating.

I brought up the lower BTU rating of Kerosine because I understand mileage and power will both suffer compared to ULSD since less work is being performed given the same amount of fuel.

With Kerosine my 100K 7.3 IDIT chugs and huffs gray smoke, is difficult to start warm or cold and drops RPM at idle yet when run on ULSD it performs great, good power, smooth idle and zero smoke.

I'm wondering if advancing the IP would help the idle, starting and driveability on Kerosine?

I hope I'm not throwing this thread OT, if so I'll create another.

 

[A37782X]

EXCELLENT info, WrickM, I just found this topic. I also just received my MT480, and I have an pulse based meter on its way. My theory was that the old 8.5 BTDC (pulse) factory spec may be totally off because diesel fuel has changed so much during recent years, and that using the 0.5-2 ATDC (lumy) spec is the only way to get back on track with diesel timing. There is just such a huge confusion about diesel timing on any forum that it's not even funny.

A great point was the burn rate, but whatever the rate is, ignition should probably happen at 0.5-2 ATDC (lumy) anyway. If it's still burning when exhaust valve opens, the fuel needs to change, not timing. Anyway, I'll be looking more into this once i have my junk set up.

 

[WrickM]

SLC yes you would have to adjust the IP timing on each fuel to get the ignition timing to 0-3 atdc. It's not the BTU rating that matters, it's the Cetane rating. You may never get as good a burn out of kerosene as you do ULSD but the engine geometry wants it to burn at 0-3 atdc to get the most out of it.

I don't know wether to advance or retard timing on kerosene because i don't know if the cetane rating is higher or lower, but in general in the cetane is higher than 40 you might have to retard the IP to compensate for the faster ignition, conversely if the cetane rating is lower you would advance IP timing to make up for the slower ignition

 

[SLC97SR5]

, but in general in the cetane is higher than 40 you might have to retard the IP to compensate for the faster ignition, conversely if the cetane rating is lower you would advance IP timing to make up for the slower ignition

Exactly what I was looking for...should have just asked that!

FYI the Cetane rating for Kerosine is indeed lower than ULSD.

 

[FordGuy100]

My bad, with pulse. Anyways we had to change it due to the ULSD. Thats my point

 

[Alex S]

Thats good to know, I'll make sure to check and see what kind of bio it is before I pump it.

good idea

Having done some work in a small bio-diesel company, that s**t is evel to any natural rubber or paint or anything it will slowly destroy it. A pair of work boots would last maybe a month before they turned into a pile of goo.
Honestly having seen what i have seen i would not run any threw my motor for a long duration unless i have gone over everything and changed all the rubber bits, and who knows what kind of rubber is in the IP

some evidence on how it can destroy enamel paint!

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just a bio-diesel filter that has had some bio fule splashed on it over and over again

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[A37782X]

I took some measurements with my MT 480. Timing was 5` ATDC @ 1400 rpm. Fuel was diesel with 2 stroke at 1:100, and PowerService diesel supplement. Before adjusting the pump, I'll wait until i fill up at the station where i always felt they have better diesel, and remeasure.

I noticed a weird dip in the timing curve, though. At idle (625) it was 7`-8`, but dipped to 10` ATDC between 800-1000 rpm, came back to the 5` at 1400 rpm and kept advancing toward zero until i lost signal around 1800.

The dip coincides with a funny shudder i've noticed going around sharp corners in 3rd gear around 1000 rpm. I thought it was a u-joint or simply lugging the engine, but...?

Do you have a timing dip like that when transitioning from idle to higher rpms?

 

[WrickM]

i have noticed the same small dip as the rpms begin to rise, but i do not have a shudder or anything with it.

 

[A37782X]

ok, cool, the shudder is most likely unrelated then, could just be a stiff u-joint.
The timing dip could be an artifact anyway (=not real), according to the instructions obtaining an accurate reading takes a two minute steady run at 1400rpm.

 

[Sycostang67]

Since the timing we have all mostly agreed upon is based on low sulfur fuel. I was wondering if adding sulfur would affect anything? I found sulfur substitute at work and have been adding it to my last few tankfuls. My truck seems quieter and runs alot better. The performance is more likely a result of work done recently though.