OK, well, I should be able to hook up a VOM and get some readings while driving around. I'm particularly interested in seeing my readings on my "test hill" when the EGTs get up close to 1200 and my foot's on the floor

Sooner or later I should be able to get around to doing some individual plug measurements too....

 

Hello........Kevin ,,,,yes I compare all posted readings and the additional information provided by the poster....I make mental notes and I plug the numbers into my program and "Play what if"..........

general notes......
if you get a negative reading.......just reverse the leads of the meter........

at first, just hook the meter to the glow plug system, to get a feel of your readings...........checking individual glow plugs is needed If you make changes based on the readings...........once you do the individual test and get a balanced reading from all the plugs, you go back to the system hook up............

Kevin's and others posting about "Power Stroke Rattle"...........when tuning by ear, the very first thing that you have to know is if the engine is a DI or IDI.............the design of the engine changes "what you hear".....a properly tuned IDI is not going to sound the same as a properly tuned DI.............

NO matter if you are advancing or retarding the timing........you go in the direction that Lowers the readings........if you go in the direction that is lowering the reading, the readings will "flatten out" and then as you continue they will begin to rise............at this point of rising, you stop and go back to the flat setting........................................... ...........when you get to the flat area, you then can start "super tuning" with injectors, intakes, exhaust or what ever.............

Kevin.........you already have a "free dyno"

crossbones

 

With my now retarded timing, I no longer have the "pre-ignition rattle" with the cold advance on, also I've only driven it empty, but doesn't seem to be significant power changes,- hopefully I've gained some by reaching a more optimum timing. Does optimum timing- ie lowest GP reading translate into optimum power production, or buy your last post CD, go for lowest GP reading timing wise, then start adding fuel screw adjustments etc for power increases?

 

Kevin.......the glow plug readings are showing you the "net effect" of any and all changes you have made to your engine............timing is just one........the changes to the intake and exhaust flow, the change of your rebuilt IP, your injectors, any additive you put in the fuel, thermostat , compression, fuel viscosity, Cetane value of the fuel, even the fact that you live in B.C. verses Florida, USA ..........the list is very long, including engine wear........

Before you can get the "true potential power" from a engine, you must start with a effecient engine so the engine can take full advantage of the changes you make..............the readings gives you a relationship of the changes you make.......good or bad.................

The beauty of the glow plug method is you can stop at any point or you can take it to the "max"....it totally depends on your personal objectives..........it gives you a method based in science and math to value the changes you make to the engine.......good or bad..........

Let's get back to the cold start advance and diesel knock...........the true function of the CSA is to compensate for lack of heat..............heat is a tuning factor.......heat is a timing factor on the auto ignition timing......................as the heat in the cylinder rises, auto ignition timing increases (advances) and the quality of auto ignition increases.......the timing and quality of auto ignition is YOUR DIESEL KNOCK............

What I have read about the CSA system so far (I have not tested this information):
it advances the timing about 6°.......
the fast idle is activated .........
it maintains this condition until the engine temperature is about 120°F...............

there are two very critical factors to understand here as how they relate to diesel knock...................the first is engine rpm.................timing and engine rpm are in a direct relationship to each other...........they are bound together with math (real time in milliseconds) ...............................SO, the very first thing you do when you have a INCORRECT DIESEL KNOCK with the CSA system in play is to CHANGE THE FAST IDLE RPM

the second thing is that the relationship of timing and fast idle rpm is changing very quickly as the engine heats up...................

there is no way that I can tell you if you need to increase or decrease fast idle rpms........this is based on "what you hear" during this period that the CSA system is on and the engine is warming up..............there is no way to get this perfect during this period.............so we "just make the best we can of this period"

You should not make decisions about hot engine timing based on this period....................once you have hot engine timing if you can not "work out" the relationship of rpms and the and CSA.......you disconnect the CSA leaving the fast idle in place.................if you have properly tuned the engine at this point...........at most two cycles of the glow plugs will start the engine just fine................and it will not hardly smoke at all during warm up.................
crossbones

 

So to make that long story short, get the lowest GP reading you can with the engine hot.??, don't worry about the cold start advance condition. KISS

 

Kevin....yes, lowest reading on hot engine..........now, if you are looking for a power setting, get the lowest readings as long as power is not decreased............if you are looking for a economy setting, get the lowest reading as long as fuel mileage is increasing.................
crossbones

 

Ok i did the idle test and listened to the rattle. The truck sounds really smooth although i do not think that the idi's really sound like the PSD. The rattle sound seems to go away after the idle and the truck smooths out really good throught up to 2500 rpm...... I am a little disappointed in the new gas milage. It was 14.3 mpg when it used to be around 15. So it went down a little. It would be nice if i could have a couple more gears. So now what needs to be done?

Sorry for not keeping up lately got to get good grades in school. School before truck...

 

turboman24 and all forum members..................I want you to think about the statement below and apply pure logic to it:
"The rattle sound seems to go away after the idle and the truck smooths out really good through up to 2500 rpm"

assuming this was a hot engine test:

should the diesel knock change as rpms change?
what caused the diesel knock to change?
why would a IDI sound different than a DI..........
why should a PSD have diesel knock at high way speeds and why/why not a IDI ................

crossbones

 

Crossbones--The diesel knock changed because of timing, either by increase piston speed and or the ip retarding. This brings up some confusion on my part because I know the ip retards as you increase rpm and if you think of a gasser--as piston speed increases so does the timing.

My understanding of IDI sound verses DI is the combustion starting in the pre cup then spreading into the combustion chamber whereas the DI combustion begins and ends in the chamber.

The PSD knock at hwy speed would be advanced timing. The IDI ---well thats were I'm confused about IDI timing.

I'll take a WAG and say it all has to do with the difference in the speed of the combustion event between the two.

Dennis

 

Well I have a 'test' lead perminatly hooked up now, and went for a drive with my meter today, with the timing retarded some from my previous setting, cruising with slight acceleration with 500 on the EGT has lowered my overall reading from 16.4 mv on my original test run, to 13.8 today@ 500 EGT, so even though the EGT is the constant in this case, I assume that the lower GP reading indicates that my in combustion temps are lower, and the engine is therefore producing power more efficently! Comments- does this sound right? If I believe the timing is optimun now based on GP readings, the next step is to increase the fuel screw!!

 

Kevin........you are still having "hints" of the timing not yet correct................IMVHO........you should continue to retard your timing as long as the readings are decreasing OR until you see a very slight rise in exhaust temperature.............as well, you should be monitoring water jacket temperature......you may not see to much of a drop in water temperature at this point............but we do not want to see a increase in water temperature...................imvho, it not time to change the fuel setting...............

crossbones

 

Dennis..............a diesel engine and a gas engine are exactly the same when it comes to "real clock time" in relationship to engine rpms ...................we have three "very fixed" things to consider...........

the very first is that there are only so many seconds in a minute..............(fixed, no matter the rpm)

second, the explosion event takes a fairly constant amount of "real clock time" each time it happens.....(fixed,within reason no matter the rpm)

third, in order to get maximum power from the explosion, it needs to happen at a fixed degree of crank shaft rotation no matter the rpm............(fixed no matter the rpm)

now, variables that can change.............

when a diesel fuel is said to have a Cetane value of say 65.............this comes from the very old and established way of comparing the different grades of diesel fuel................this value of 65 is the "real clock time" measured in milliseconds from the beginning of the injection to auto ignition............now in the early 1900's the typical grade of diesel fuel used in lab test had a ".65 millisecond delay" hence had a Cetane value of 65...........................now do not ask me why the scale goes this way....................but a Cetane value fuel of 45 such as todays typical #2 diesel has a .85 millisecond delay.............................the point I am try to make here is that if both a IDI and a DI engine are using typical # 2 diesel fuel............(then we have the forth Fixed time relationship no matter the rpm)

so with all of the very fixed time relationships above, we are left with the BIG VARIABLE........RPMS

as rpms increase the physical amount of time available for these very fixed time events to happen and still happen at the degree of crank shaft rotation to get maximum power in decreases................................SO, THE ONLY OPTION WE HAVE AVAILABLE is to advance the beginning of the injection period at a rate equal to the rate of decreasing time available............

it does not matter if its a IDI or DI, as long as the exact same fuel is used.................and the degree of crank shaft rotation (in order to get maximum power) is the same................then the timing is the same..............

If the injector timing is correct at idle and this produces a diesel knock (fixed degree of crank rotation for maximum power) and the correct fixed degree of crank shaft rotation is maintained at all rpms...............

then logic tells us that diesel knock Should be at all RPMs and it should "sound basically the same at all RPMs"

logic tells us that mathematically, as RPM's increase........injector timing Must Advance at a equal rate as the time available decreases.........................

logic tells us that the more heat is instantaneously converted into mechanical energy at the correct degree of crank shaft rotation...........................less heat is available to go out the exhaust, into the water jacket.................and what about them "glow plugs"

crossbones

 

Crossbones---If I'm reading you right, when the rattle lessens as rpm increases we are too far advanced at idle or the advance curve of the ip is wrong..?

 

OK, I've done some more tinkering with the following results: (nothing has changed except the timing)
Original timing 1/2 scribe advanced, cold knock:
Ilde gp reading 9.7mv, cruising town driving EGT 400- 14.4mv, accelerating 500EGT 16.4mv, loud exhaust- headers

Retarded scribe width: no more cold knock:
Idle gp reading 8.6, accelerating EGT 500-13.8mv- less exhaust rap

Retarded 1/16":
Idle 7.9mv, crusing town EGT 400-mv 10.4, accelerating 500 EGT -12.8
Exhaust rap almost gone unless I boot it. power change, not sure because of less noise, but acceleration seems not to have lost anything, and a stall torque rpm has not changed! I feel that any further retarding will result in power loss at this point, however , I will run it at this setting until I can check milage, and/or see how it performs with a load. The sribe lines on the orignal IP were retarded about the same amount FWIW.

 

Dennis.............a diesel engine is suppose to rattle............the reason is again proved with math......when the small end of the connecting rod is exactly at TDC, the piston is "free to rock back and forth" due to the clearance between the piston skirt and the cylinder wall........now at the big end of the connecting rod...........due to the fact of rotation of the big end around the crank shaft, there is a period of rotation of the big end that the small end is not moving or is so small that the piston skirt thrust side has not come back into contact with the cylinder wall..............this is call "piston dwell time".............now on a typical diesel, the piston dwell time is inside of the degree of crank shaft rotation where the best conversion of heat into energy usually begins......................from -TDC to about .5° to 1.5° ATDC depending on the rod length..................

There are at least four types of diesel knock..........

the first and most damaging is when auto ignition happens before TDC............

the second is when auto ignition is in the "window of best heat conversion into power..................as you can see above, its a small window...............

the third diesel knock is when there is to Much Fuel in the Cylinder at the time of auto ignition (the explosion (the bomb is to big)) not only do we then have to much heat to convert efficiency and its wasted..........we now have to deal with the "bomb effect"

the bomb effect is something that is simple to under stand the effect of....................ever seen on TV when they put out a oil well fire...................the injection of fuel in a diesel works the exact same way.........once the explosion (fire).........there is raw fuel continuing to be pumped into the fire..............

a 1% over fueling can equate into a 10% decrease in efficiency and power.........

the fourth diesel knock is the "quite one"..........the timing of auto ignition is so far "away" from the "free piston dwell" the diesel knock is quite and the heat to energy conversion low...............But the Sonic (energy) wave is dispersed lower in the cylinder....................Hello cavitation...........................

there is another issue with the "quite one".............Coking..... (Critical Issue if using VO for fuel).....if the beginning of injection is late, then auto ignition will be late, and the end of injection will be late......if the fuel is injected so late that either it does not have the physical clock time to reach complete combustion or the rod angle has degraded to a point that the heat can not be converted into mechanical energy ,,,,,then the remaining fuel goes into (what I call) a "slow burn" and this leaves carbon residue.....................((Note: this slow burn period produces a huge rise in temperature in the cylinder, exhaust and water jacket)........in the very old lab reports, this period was very briefly described......just as if it was common knowledge of why temperature rises.......I have not found a report that explained the "slow burn" in detail or even the technical name of it..............I just know it is there.............

all of the above just says, there should be a diesel knock at all rpms,,,,,but it has to be the correct diesel knock.........this why I do not rely completely on "tuning by ear"......................

crossbones