Timing adjustment methods - Page 8 - PeachParts Mercedes-Benz Forum

RichC · #**106** 01-24-2011, 11:36 AM

Well I have proof of my ideas.
They are driving the roads every day.

Have you guys ever timed one of these engines ???

And the answer to the question you would never get.

" How do you paint a perfect Mona Lisa with a 4 inch brush "

Is

Broaden your canvas !

funola · #**107** 01-24-2011, 11:37 AM

Quote:

Originally Posted by ForcedInduction

Correct; combustion = pressure.

Incorrect. Please explain why compressed air engines work without any heat.

only ne

Because compressed air engines 'burn' compressed air, not diesel. lol

babymog · #**108** 01-24-2011, 05:05 PM

I think that the answer to Funola's question is:

Heat causes expansion. Expansion causes pressure. Pressure moves the piston.

Now making the assumption that more heat causes more expansion is correct, however this expansion is only producing work if it is during the power stroke, before TDC is reducing the energy converted into work, so the actual temperature can be one indicator of potential energy, but the timing of that peak temperature / peak pressure is extremely important.

Also, mentioned above is how excess fuel can be used to cool the piston etc., but that is in a direct injection engine where in an IDI engine excess fuel will NOT cool the piston.

leathermang · #**109** 01-24-2011, 07:10 PM

Quote:

Originally Posted by whunter

As a theoretical exercise I will comment on the idea:

* Each cylinder is a totally separate environment.

* On an OM617 the math breaks down like this: 850 RPM ÷ 60 seconds = 212.5 power strokes ÷ 5 cylinders = 42.5 power strokes per cylinder = roughly 0.708 second of combustion data per cycle + immediately followed by exhaust (cooling), intake (cooling).

I hate to bring this up since Whunter Agreed with me...and was correct in the direction he was headed...
but I do not believe that the ' word math problem' was set up correctly... and thus came up with the wrong number as a result...
Anyone else see a/the discrepancy ? I left the part about 'each cylinder' in because keeping that in mind can help simplify the setup.

I believe the answer to be: 1.0 / = power strokes time (combustion access time) per second per cylinder at 850 rpm.
I used the inverse of one second to figure the access time.

850 divided by 2 is the number of four stroke cycles per minute per cylinder... with one power stroke in each.

425 power strokes per cylinder per minute divided by 60 is power strokes per second equals 7.08333333 power strokes per second.
or 1 / 7.08333333 =

IE, seven combustions per second into one second.

OR one second divided by seven combustions..

0.141176471 seconds as the access time. ( seconds of combustion data per cycle )...
IE,
One Tenth of a second sensing access by this non thermocouple ( rounded off )...
I could be wrong....But it would be the first time ....

whunter · #**110** 01-24-2011, 08:22 PM

Quote:

Originally Posted by leathermang

I hate to bring this up since Whunter Agreed with me...and was correct in the direction he was headed...
but I do not believe that the ' word math problem' was set up correctly... and thus came up with the wrong number as a result...
Anyone else see a/the discrepancy ? I left the part about 'each cylinder' in because keeping that in mind can help simplify the setup.

I believe the answer to be: 1.0 / = power strokes time (combustion access time) per second per cylinder at 850 rpm.
I used the inverse of one second to figure the access time.

850 divided by 2 is the number of four stroke cycles per minute per cylinder... with one power stroke in each.

425 power strokes per cylinder per minute divided by 60 is power strokes per second equals 7.08333333 power strokes per second.
or 1 / 7.08333333 =

IE, seven combustions per second into one second.

OR one second divided by seven combustions..

0.141176471 seconds as the access time. ( seconds of combustion data per cycle )...
IE,
One Tenth of a second sensing access by this non thermocouple ( rounded off )...
I could be wrong....But it would be the first time ....

No doubt you are correct.
I am not a mathmagician..

0.708 or 0.141176471 are both far beyond thermocouple accuracy.

.

casioqv · #**111** 01-24-2011, 08:29 PM

This thread is hilarious.

I prefer to use a dowsing rod for setting my injection timing. If you hold the rod in one hand while adjusting timing with the other, it will twitch when it's just right

leathermang · #**112** 01-24-2011, 08:37 PM

Quote:

Originally Posted by whunter

No doubt you are correct.
I am not a mathmagician..
0.708 or 0.141176471 are both far beyond thermocouple accuracy. .

Absolutely. And it isn't even a thermocouple in the first place... LOL... as you pointed out...

leathermang · #**113** 01-24-2011, 08:47 PM

Quote:

Originally Posted by casioqv

This thread is hilarious.
I prefer to use a dowsing rod for setting my injection timing. If you hold the rod in one hand while adjusting timing with the other, it will twitch when it's just right

We try to entertain...
You must have the record for 'speed of infraction'.. one before 22 posts ?
Stay away from the Open Forum if that is where you got that.... dangerous place to go...

casioqv · #**114** 01-24-2011, 09:00 PM

Quote:

Originally Posted by leathermang

You must have the record for 'speed of infraction'.. one before 22 posts ?

Hopefully I don't get banned before I finish my 190D head gasket, since I'm going to have a lot of questions!

I got my infraction here in the Diesel forum for posting a link to "illegal software" aka a PDF of the factory service manual containing information someone needed to fix their car.

I understand PeachParts doesn't want to be held potentially liable for illegally distributing copyrighted materials but I do think that sharing factory service manuals illegally to help keep these vintage cars from getting scrapped and replaced with lower quality new ones is the right thing to do hands down. People should buy the manuals if they can afford them- but if they can't, they should download and use them anyway.

leathermang · #**115** 01-24-2011, 09:16 PM

Casioqv, Well, that is certainly one of the ' kinder gentler' ways to get an infraction that I have heard of... most others work hard for months to earn theirs. Good luck...

babymog · #**116** 01-24-2011, 10:46 PM

Sorry but those manuals are just not that expensive on CD, much cheaper than a tank of fuel or an oil change, and there are copyright laws for a reason. It isn't right to give away someone else's work, nor to take it without paying for it, nor selling it without permission, period.

I spent years writing patents, working to be sure that the Engineers and company which spent the time and money developing new products and processes were legally protected so that they would hopefully eventually profit from their work, which is the only reason that most people and companies are willing to spend said time and money in the persuit of a "better mousetrap".

If the manuals are copyrighted, pony up or do without.

ForcedInduction · #**117** 01-25-2011, 12:47 AM

Quote:

Originally Posted by RichC

Well I have proof of my ideas.
They are driving the roads every day.

Thats not proof, thats an anecdote.

Quote:

I got my infraction here in the Diesel forum for posting a link to "illegal software" aka a PDF of the factory service manual containing information someone needed to fix their car.

Thats why you only post an image of a specific part, not the whole file.

Quote:

I do think that sharing factory service manuals illegally to help keep these vintage cars from getting scrapped and replaced with lower quality new ones is the right thing to do hands down.

Spending $20 to own the entire service manual is the right thing to do. Stealing is never an option, no matter how poor/greedy/selfish.
If $20 is that much of a stretch then I doubt they would be owning a car in the first place.

Stretch · #**118** 01-25-2011, 05:07 AM

Quote:

Originally Posted by whunter

No doubt you are correct.
I am not a mathmagician..

0.708 or 0.141176471 are both far beyond thermocouple accuracy.

.

I agree with these figures at idle of 850 rpm you are getting 7.08 bangs per second

The time between each bang is the reciprocal of this number = 0.14 seconds.

If you were to (be stupid and) rev your OM617 to 6000 rpm - the camshaft would be rotating at 3000 rpm - which would mean as you get one bang per rotation of the camshaft - you would get 50 bangs per second.

Bangs per second is like saying cycles per second which is often described by the unit Hertz (Hz).

So we are working in a frequency range between 7Hz and 50Hz. For most frequency analysers, data loggers, and computers this is really slow - really low frequency stuff - as you'd expect from a mechanical machine.

Thermocouples are used to measure frequencies up to 1000Hz (1kHz). See this pdf for example:-

http://www.grc.nasa.gov/WWW/sensors/PhySen/docs/RSI%20Fralick.pdf

On the first page you will see this text:-

"For example, the measurement of fluctuating temper-
atures in the high speed exhaust of a gas turbine engine
combustor is required to characterize the local gas density
gradients or convective heat transfer.’ Although thermo-
couples are suitable for the measurement of high frequency
temperature fluctuations ( < 1 kHz) in a flowing gas or
liquid, the measured signal must be compensated since the
frequency of the time dependent fluid temperature is nor-
mally much higher than the natural frequency of the ther-
mocouple probe."

So it is saying here that thermocouples are used to measure high frequency temperature fluctuations but compensations need to be made when the changes in the fluid being measured are faster than the natural frequency of the thermocouple.

So I argue that thermocouples are used to measure high frequency temperature fluctuations and if you were to use an appropriate thermocouple as a transducer you could probably pick out the heat pulses created during ignition.

As for any transducer it needs to be suitable / appropriate - and a glow plug is not designed to act like a thermocouple. This is why I suggested that the first step of proving or disproving this myth would be to ascertain the behaviour of the glow plug when you are asking it to do the job of a thermocouple.

layback40 · #**119** 01-25-2011, 05:29 AM

[QUOTE=funola;2644248]

Quote:

Originally Posted by layback40

You havent considered the original false assumption that the idle or for that matter at any rpm hottest combustion temp is optimal or is what is best for the motor. It is not.QUOTE]

The diesel engine operates on heat. It is heat that drives the piston downward. You are saying hotter combustion temp is not optimal?

Please re-read my posts. There NO connection between setting the injection timing for highest temperature of combustion at idle & how the motor runs at normal operating revs.
It is NOT heat that drives the piston downward, it is expanding gas.
Motors start injection prior to TDC & there is some initial compression of the burning mixture. This causes increased temperature of the burning charge. Too much temp increase & the fuel explodes instead of burning.

The fuel must burn in a controlled manner & not explode or go "bang". Best you learn what Centane Number means.

In the case of WVO the combustion characteristics are so poor that you need to preheat the fuel to get it to burn sufficiently as to not gum rings. You may notice that sum advance injector timing to try & help when running on WVO.

Please do not throw these one liners in that have no scientific basis.

layback40 · #**120** 01-25-2011, 05:44 AM

Quote:

Originally Posted by funola

Incorrect. Without pressure, there is no leverage. Without heat, there is no pressure. Atomized diesel is ignited by heat which generates pressure.

This statement is absolute C##P !!!
A high school physics/chemistry student could shoot this claim of yours to pieces.
You need to go & get an education about thermodynamics !!!

Time to stop throwing in old wives tales to a discussion that is clearly well above the level of technical competence of many.

If you wish to understand things I would recommend;

Introduction to Chemical Engineering Thermodynamics
by Smith & Van Ness

& Chemical Engineering Kinetics
By Smith

If you have a strong enough back ground in Maths, you will understand them.
Best not throw in some half baked idea with no proper technical justification.