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Hello Darin. Nice to hear from you. The reason that I use the 300 milli volt scale is for convince: (a) that's the scale of my meter (b) its a auto scale meter, so I can see the applied voltage to the glow plugs (on my trucks, the glow indicator light does not mean I am getting voltage to the glow plugs) (c) I do not have to worry about changing scales when the glow plugs are heating..........
I believe you are seeing why I recommend to check the glow plugs for "balance" under heated conditions instead of a cold check.................The only cold check I do on a glow plug is just that it has continuity (ohms).......I determine if the plug is good or bad under heated conditions.............even if not using the glow plug reading for tuning purposes, testing them hot and making sure they are "balanced" can improve cold starts markedly......... I predict you will get some "amazing" information under real driving conditions...............you should be able to "see" the value of any change you make.............including which way the wind is blowing........... regards, crossbones "If Your Engine is not happy, You are not going to be"....... a properly tuned engine will greatly add to your success of using VO as fuel........ |
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The circuit diagram I'll be working to:-
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about water temp and advancment. i am understanding from my findings and the diesel shop that advance gives a temp rise in coolant but helps mpg and power due to the fuel being under pressure and its heat longer to burn more complete which gives more power from the fuel but somewhat higher operating temp.
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Been very busy with one thing or another and not had any time for any practical development work. I also have had very little web time recently.
I've got a Mercedes 310 pick up. 2.9 ltr 5 cyl OM602 engine. Makes a strange tapping noise at high rpm. I was looking for any similar ecxperiences and came across this thread on a Merc forum http://www.mercedesshop.com/shopforum/showthread.php?t=152389 Nice to see some people testing this method. Spurred me to do some quick testing. Engine warm readings Cyl 1 .006V 8.5Ω .064(40mA scale) Later test .006V 8.2Ω Cyl 2 .007V 8.8Ω .066(40mA scale) Later test .006V 8.6Ω Cyl 3 .007V 9.4Ω .073(40mA scale) Later test .007V 9.3Ω Cyl 4 .006V 8.5Ω .065(40mA scale) Later test .006V 8.3Ω Cyl 5 .006V 8.0Ω .060(40mA scale) Later test .006V 7.8Ω Cylinders 3 & 5 both read a bit out of spec. I'm going to chage the plugs about and see what readings I get. Hopefully I'll get some time to do some more work with the TDi soon - although the Mercedes has been my transport for the past month or so (lots of things to carry, trailers to tow, work to do-and it runs on veg) Best Darren |
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With regards to my early mention of observing the combustion event using Peizo crystals see this link. http://www.optrand.com/products.htm
I had some chance to play with the Piezo crystal timing device. Unfortunately it came with a adaptor for a 1/4 inch injector pipe. I tried it on my Passat which had 6mm pipes. Could not dial adjustable strobe to fire on the TDC mark. Unfortunately I don't have access to that timing device any more - Have to sort something out..... |
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Took another set of data today on SVO and then ran the tank very low before refulling with 40.5 ltrs of diesel.
Then I took another set of data. The result are interesting. This is in an unmodified Mercesdes 310 OM602 engine. SVO Diesel CYL 1 V 0.006 0.006 Ω 8.7 8.3 40mA 0.067 0.064 CYL 2 V 0.007 0.006 Ω 9.2 8 40mA 0.069 0.062 CYL 3 V 0.007 0.007 Ω 9.1 9.5 40mA 0.070 0.073 CYL 4 V 0.006 0.007 Ω 8.7 9.1 40mA 0.066 0.07 CYL 5 V 0.006 0.006 Ω 8 8.6 40mA 0.061 0.067 It appears from the 3 sets of data when on SVO that the three scales (V/Ω/40mA) all follow each other. When I changed to diesel in three of the cylinders the values went up and for two cylinders they went down. If I'm understanding correctly in some cylinders combustion temp increased in others it decreased. Changing to diesel fuel effectively advances the combustion event as they fuel burns quicker. The only other effect I can think of that would have an effect on combustion would be improved injection with diesel fuel. Anybody got any ideas what is going on? When I tested a VW Tdi glowplug it read higher as it got hotter. In this post HERE crossbones is suggesting that lower readings are better??? I would have thought more heat in the combustion chamber would show that the fuel is burning better???? This message has been edited. Last edited by: vegburner.co.uk, |
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Disclaimer.....as I have been nursing a rotator cuff injury for several months and just now had the surgery I am typing with one hand........so no real testing in this time and for several months to come.........sorry if you think this is a long post...just think how long it took to type it...............I hope this tells you just how important I believe this is to the successful usage of VO as fuel
Hello Darin. Nice to hear about your testing. Your different glow plug readings with the different fuels are indeed coming from a change in the AIT event timing ...I call this the auto ignition timing of the fuel.....and the amount of raw fuel in the chamber at the time of AI TIMING........... There are many factors that have a net effect on these changes in the cylinder temperature/pressure and their important s vary greatly until the engine has reached operating temperature at which time these factors begin to be more predictable...... In order to be simple in nature with this, let's start at the period when the factors are more predictable. The more predictable period is when  this is for diesel fuel)a) the engine block core temperature has reached about 150F( upper hose temperature of 195F usually get the core temperature in this range) b) the intake air inlet temperature is about 80F(non turbo engine) c) the actual compression of the cylinder measured in PSI is with in factory specks(this will give you your Effective Compression Ratio....) ....get the square root of your PSI reading ...ex. 441 PSI reading would result in a ECR of 21 d) fuel temperature of about 115F e) fuel with a cetane of about 62.5 to 65 f) a injector that is set to the correct pop off pressure and does not drip or leak down at just a few pounds under pop off pressure setting for hours!!!!!!!!! controlling the quantity of fuel and the timing of the beginning and ending of the injection period is critical...................... It is very important to note that any change in the above changes the following injector timing speck.......( and is the very reason I started using the glow plug readings to give me a relationship of the net effect of any of the changes) Now, if we have all of the a through f conditions in place, and we are using a engine that ran continuously at 1500 RPM´s the injector timing would be 13 degrees BTDC.............of which would produce the conditions from the very beginning of the injection for the very smallest droplets of fuel to reach its auto ignition temperature and a small flame front is started.......during this physical time period there are several things happening....the piston is still rising increasing temperature-pressures, the flame front is providing more temperature-pressures and the injector is still injecting more and more fuel............this is where the ¨balancing act begins.......... The balancing is just this...........in this period of both crank shaft rotation in relationship to TDC, the quantity of fuel injected, the temperatures in the cylinder and the physical amount of time available for the fuel to absorb this heat in order for it to reach auto ignition...........if we have to much fuel in the cylinder when the temperatures in the cylinder is at the point that all remaining fuel is going to ignite simultaneously....then we have a small bomb effect.........this produces higher temperatures-pressures...................hence.............. Higher Glow Plug Readings Well, at first thought, we have just burned all of the remaining fuel...........but now we have a major problem.................The injector is still injecting raw fuel after TDC and all of those good conditions that promoted combustion before TDC are very rapidly declining as the piston is now going down (expansion stroke)..........plus we now have to deal with the bomb effect.....(ever seen how they extinguish a oil well fire).........I think it very easy to conclude that if the conditions before TDC are not favorable to a more complete combustion that after TDC they are even worse...... Do not be lured into thinking that when using VO as fuel and diesel knock is substantially less that this is better for your engine............as we are going through this event of physical crank shaft rotation and time a certain amount of the bomb effect (diesel knock) is of great benefit after TDC in providing the temperature-pressures to provide a more complete combustion of the fuel injected after TDC. My testing using glow plug readings and having a dynamic timing light that I can use under driving conditions I have made the following observations and conclusions.......... engine core temperature has a direct bearing on the readings......cooler temperature produces higher readings.... cooler intake inlet air temperature than about 80F produces higher readings(non turbo) injectors that are dripping or not set to OEM pop off speck produce very high readings........ when using a mechanical injection pump and the pump is having supply problems due to viscosity, restriction or plugging filter produces very high readings (changes the ability of the injection pump to maintain the proper injector timing) on my style Bosch VE injection pump, it is not capable from the factory (has a total range of 8 degrees advance) in maintaining the proper injector timing through out the total RPM range of my engine...............this produces higher readings when in RPM´s above this limit in advance........ load on the engine produces higher readings.......... a glow plug that is going bad, but just has not totally failed will produce high readings brand new glow plugs are not constant in having the same reading among them carbon build up in the chamber-cylinder produces higher readings on my engines, 2.2 Isuzu the difference in readings from a non turbo to a turbo engine is about 1 millivolt higher per PSI increase in boost there is no way for me to get exact with the difference of readings between diesel fuel and VO as both fuels vary so much over the world............the best I can say is the range of higher readings when changing from diesel to VO without making any other changes can vary from .3 to 1.8 millivolts depending on RPM(this is using math to predict cylinder temperature-pressures) you are getting all variables very close when after the engine is at operating temperature and any timing advance has been canceled for cold start.........from idle, you slowly increase the RPM´s up to operating RPM and the readings do not increase much more than 1 millivolt.............it is not unusual during this range of RPM´s for the readings to drop and then to proceed higher as RPM´s are increased............this combination of RPM and injector timing when the drop occurs is where all variables have combined net effects for the best combustion for that engine load......if you have the means to check all of the temperature variables and that they are easily maintained at that temperature, injector timing and RPM´s, then it is very simple to apply the math(time available per degree of crank shaft rotation for the RPM range that you wish to use and develop a variable injector timing advancement scale that in my theory, the glow plug readings would be the same through out the RPM range with the same load on the engine.......... I hope many people will explore this idea..........it´s not new,,,,,,,I have found hints to it from the 1920´s and 30´s and several glow plug manufactures have patents as new as 2005 in the basic area...........and I am cocky enough to say they have the boat in the water.......but they still are not in the damn boat................................... regards, crossbones "If Your Engine is not happy, You are not going to be"....... a properly tuned engine will greatly add to your success of using VO as fuel........ |
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Crossbones,
Sorry to hear about your shoulder. Mine is giving me grief damaged it a few years back digging christmas tree stumps from a field, normally I don't notice it, but I have been digging holes for fence posts recently and now it constantly aches - I'm thankfull its nothing compared to what you are going through. Thanks for spending the time on your post. Things are making more sense. Did some searching the other nite and came across some of your posts on other forums that throws a bit more light on the subject. I'll order up a load of glow plugs and a set of injector nozzles. Might be a while untill I get a chance to install everything - need to gather the tools up (My life is very 'scattered' at the moment) and find some time. What is the failure rate on new nozzles you have tested to your drip criterior? Best Darren |
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Hello Darren. So far I have not tested a brand new injector. In order to have a good base line for my test, I have purchased a total of 9 trucks that have the same Isuzu 2.2 engine both N/A and turbo...they have had a large range of disrepair...........two of these truck either would not start at all or would run so poorly you could not drive them..........both of these two trucks had the injectors cleaned and set just before I purchased them trying to get them to run correctly........when I tested the injectors I found a mixed bag of pop off pressures and most did drip or leak..........the fact that my style injector has a adjuster screw that is used to set the pop off pressure which makes it fairly easy to set the pop off and finding that these injectors were as much as 18% off from OEM speck puzzled me............especially after cleaning and setting them to OEM speck and making sure they did not drip, these two truck then come to life and are the best running trucks I have.......they run as good as new now after what I call a simple tune up...............I started asking a lot of older diesel mechanics and pump shop repairmen about this...........basically, the common response was a "rule of thumb" that you never set old or new injectors to full pop off speck........close was "good enough"............And Most used about 300 to 500 PSI for the drip test.........so after thinking about just how much time it takes me to get a set of injectors to my specks and how much the shops in my area charge for this, it is easy to see they could not make any money "setting them just right"
........so the human nature and money rule applies...............And this rule will not cut it with VO usage...it barely does with diesel fuel............. I look at injectors as timing devices........not atomization devices............ I have purchased trucks that were running ok, check the glow plug readings and then pull and replaced them with clean/set injectors and retested the readings and have a 5-6 millivolt drop in readings, pulled the clean injectors and replaced them with the dirty injectors and then did all kinds of changes trying to get a equal drop in readings..................then changing engine temperature showed the largest change in readings, but not equal to I look at engine block temperature as a timing device.........think on this a moment.....you have a clean set of injectors in place and you are looking at your glow plug readings........when the engine is cold, the readings are a little higher and as it warms up they start to go down..............Has atomization of the fuel changed?????.....or has the amount of available heat increased and decreased the amount of time that it takes for the fuel to reach auto ignition?????.........time is timing........ Compression, intake temperature, engine oil temperature and valve settings are all timing devices...... Next we have the IP........we all know this is a timing device...........ok, math tells us that as RPM's increase the physical amount of time for the fuel to absorb the heat required Decreases........so in order to have the correct amount of time, we have to advance the injection timing to get this..........there are three basic ways to have a controlled advance mechanism: centrifugal, hydraulic or computer............... Now for the people that do not have a computer...........when you have a plugged filter, how does this effect engine performance????.....more diesel smoke???.....diesel smoke is unburned Excess fuel............I have found a plugged filter to raise the glow plug readings as much as 12 millivolts.........under load conditions So, the fuel supply to the IP on some engines is a timing device.......................it effects the IP's ability to keep the correct timing................ The kind of fuel you are using is a timing device........think about it.........viscosity effects the supply side of the IP............the cetane value effects the auto ignition timing.............the autoignition temperature of the fuel effects the auto ignition timing....................the temperature of the fuel effects auto ignition timing.................. So, which is the controlling factor for a more complete combustion: all of the effects on timing or atomization of the nozzle ?? Everything I have mentioned, at one time or another I have been able to see a "relationship" when changing things with glow plug readings............... Opinions welcomed.... regards, crossbones "If Your Engine is not happy, You are not going to be"....... a properly tuned engine will greatly add to your success of using VO as fuel........ |
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Managed to log readings from glow plug no.1 using a multimeter (my new laptop has a serial port so I could use the software that came with my meter)
Results of first run:- http://vegburner.co.uk/images2/MercGPLog1.gif Log completed from cold start at 9 deg celcius ambient 16:46 Connection to multimeter fails and is reconnected 16:53 Short full acceleration run on motorway 17:05 Engine shut down for 5 mins, carboard covering placed over 50% of radiator 17:48 Engine shut down for 50 minutes 18:43 signal lost for 12 minutes 18:56 - 58 Long hard uphill run from standing start Max coolant temp read from top hose is 71 deg celcius using a sensor attached to the outside of the hose(dodgy thermostat?!?)- same with longer runs Diesel Fuel Im planning to service/replace injector nozzles tommorrow (well later today) will do some more logging after the change |
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Wow, this is a great topic. Not that I need any more projects, but I can't resist considering trying this out....
I'm curious how much the difference in "unbalanced" glow plug readings relates to resistance/voltage drop differences when the glow plugs are activated. If there was found to be a correlation, then perhaps a correction could be made to the millivolt readings? I would think that if using resistance instead of millivolts, that would be the case... Bummer my truck has the glow plugs under the valve cover, makes switching GP's to test a pain. |
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Hello Darren..Excellent work my friend..... A few comments about the readings on the data log......
over all the engine is doing a very good job in maintaining a good balance of fuel quantity and timing... the high spikes of about .019 under load are on target with the information I have about VW's tuning for fuel economy (a 4 bar increase in cylinder pressure)........now what I do not know for sure is if this reading is a max or maintained reading .............with my testing so far, I am inclined to think it is a max reading.......... just for fun at this point.......if I change the injector timing in my math program to match up to the .019 volt readings.............. glow plug reading in millivolts............. 1.98 Pressure Increase in Bar.....................4.13 It is my personal opinion this increase in cylinder temperature/pressure is the factor of incomplete combustion............ It will be very interesting what you find after changing the injectors.............. P.S. A few weeks back you mentioned using a extended reach glow plug.......I give a opinion (guesstimate) ......I was not happy guessing........so after days of thought and research it is no longer so much of a guess  ..............If I am correct, the glow plug readings will show it...........When attaching the temperature sensor to the outside of the top hose, the temperature reading can be much lower than the water temperature due to the cooling affect of the fan and the ambient air coming thru the engine compartment.......... Keep up the excellent work! crossbones "If Your Engine is not happy, You are not going to be"....... a properly tuned engine will greatly add to your success of using VO as fuel........ |
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Crossbones,
The readings are from the Mercedes 310D pick-up. The multimeter software logs once a second. When reading voltage the reading does appear fairly stable steadily rising and falling in time to the work the engine is performing. I did some logging today (although the laptop shut down after 10 mins - didn't yesterday?) I tried changing to the ohm scale which has more definition and noticed some raopid jumps in the reading? The display on the meter which updates somewhat quicker than once a second was jumping about quite a bit. I made the graph using Excel. The day escaped me and I won't have a chance to do the injectors until late next week. I will have the opportunity to do some more logging before then. I'll try and get some readings for later comparison; warm engine, sustained 55mph etc. Glow Plugs... The local courier tried to deliver once, did not leave a note and after sitting in their depot for a week or so the plugs are very slowly winding their way back to Germany. I'm waiting for them to get there and then be sent back. Still one step at a time makes most sense to me (pity about my step rate). It'll be interesting to see what my tinkering changes. Best Darren |
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Hello Darren. I am looking at the relationship of the data log more so than what kind of vehicle produced them........the fuel is the common link, not the engine...........the engine is designed for the fuel used....this has to be a universal factor.........
Things I have found that produce "bouncing" readings are bad grounds.......use the block and not the battery ground............. As you do more testing you will find the readings to be very sensitive.......a small grade or head wind will show up......even a passenger............. As you proceed with your testing and what you will be able to see with the glow plug readings will be the opposite of modern excepted thought for mileage,emissions and alternative fuels............ crossbones "If Your Engine is not happy, You are not going to be"....... a properly tuned engine will greatly add to your success of using VO as fuel........ |
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Finally got some time to update.
Used some diesel purge through the engine noticed a difference in performance and engine ran smoother - previously would judder a bit when pulling from low revs. Pulled the injectors and tested opening pressures all between 100 and 115 bar Injector 4 leaked when held below opening pressure for a few seconds. The rest were in reasonable condition. Had already ordered a new set of Bosch nozzles fitted and tested the first which was terrible. Noticed they were made in India tried a few more which were better but not ideal. Ordered some Delphi nozzles. These all tested good set them all between 127 and 130 bar (slightly higher than standard) I've been logging a fair bit of data from the glow plugs  After injectors changed long run engine warmed up with a couple of minuates drive before logging. I messed up the other graphs I made I'll post some more data when I have time. Observation would be that the engine appears to be running hotter (supported by the cylinder temps and the coolant gauge readings) I damaged one of the injector housings when changing the nozzles and I'm not sure if it is sealing properly I've got another housing and will be putting things right in the next few days. I did however pass the smoke test on my MOT (road worthyness test) respectably the other day with the engine like this. I have got the tdi running again and am going to get a data loggerso I can collect from multiple data points ( up to 16 ) I should be able to start collecting some useful data sets soon. As always time is limited but things are moving in the right direction....Best Darren |
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Hello Darren, nice to hear about your testing. Just a couple of general comments. When you up the pop off pressure from OEM Speck, it has the effect of a injector timing delay. I usually find that delaying the injector timing raises the engine temperature. The biggest problem I have with engine temperature is when advancing the injector timing to the correct timing is getting the engine temperature back up to a good operating temperature...........you will need a thermostat that does not open at all until about 170°F to achieve a good operating temperature and most likely a radiator bib........if you are driving in very low ambient temperatures you will need to seal almost all of the frontal area of the grill as this air flow across the engine has about a 10-15% cooling factor on engine temperature..........
Basically, the closer you get the injector timing, more "heat" is being transformed to power and less goes to water and exhaust temperatures............... Keep up the good work....it is all there.......... regards, crossbones "If Your Engine is not happy, You are not going to be"....... a properly tuned engine will greatly add to your success of using VO as fuel........ |
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Hello,
I've been running a fair few logs on diesel. I just got myself a labjack UE9-Pro http://www.labjack.com/details.php?prodId=46&category=2 to allow for some more rigorous testing. I'm impressed with the results so far  The graph shows the signal from one Bosch Duraterm Chromium glow plug and then me removing the jumpers and testing another nine, each in turn. Then finally I attach a Bosch Duraterm. Grasp the end in my hand for a few seconds. Then hold it over a flame for a couple of seconds and remove. The signal from the first few plugs may well show that I was not being so carefull - with the later plugs I made sure I did not touch the end with my hands. Can't wait to gather a selection of suitable sensors and get them all calibrated/set up. In the mean time I'm going to play some more with the plugs I've got in and out of the vehicle. Best Darren |
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Hello Darren. Good to see you are still testing....I just returned from a little vacation on your "side of the big pond". One thing that I observed was almost no tail pipe smoke on the diesel cars and trucks that I saw....a good indicator of better fuel or better tuned engines than in the USA.....
keep up the good work, crossbones "If Your Engine is not happy, You are not going to be"....... a properly tuned engine will greatly add to your success of using VO as fuel........ |
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