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Go Back   TDIClub Forums > VW TDI Discussion Areas > Alternative Diesel Fuels (Biodiesel, WVO, SVO, BTL, GTL etc)

Alternative Diesel Fuels (Biodiesel, WVO, SVO, BTL, GTL etc) Discussions about alternative fuels for use in our TDI's. This includes biodiesel WVO (Waste Vegetable Oil), SVO (Straight Vegetable Oil), BTL (Biomass to Liquid), GTL (Gas to Liquids) etc. Please note the Fuel Disclaimer.

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Old August 30th, 2008, 19:51   #1
T'sTDI
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Default Observations On WVO Using VAG COM

VAG COM is such a great tool to have and it has proven a worth while asset while burning WVO. It has given me answers to a lot of the questions that I have had and I will explain what I have found. More than likely some of you have found this but to reiterate, allow me to share my findings.

There are a lot of variables involved with timing done by the ECU. Whether it be coolant temp, air temp, fuel temp, engine temp or mechanical variables such as pop pressures, there are a lot of things monitored and involved with timing in a TDI engine.

The conclusions that I have drawn from what I monitored, measuring block 004 and measuring block 007 is that the ECU indeed retards timing due to extreme fuel temperatures. (nothing new)

My timing at idle on diesel fuel is set advanced. It is tyipcally halfway between the middle and top line of the graph. My engine at operating temp with coolant of 190 and fuel temps of around 100 degrees is 2.0-2.2 deg BTDC (advanced)

I was only on diesel fuel for a short while before I switched to WVO but in any driving situation during that time, I never saw any readings of ATDC (retarded timing) Whether it be high RPM, high load or low RPM, low load

After switching to WVO I found a lot of things that may interest the WVO community.

1) Greasecar with the FPHE is the absolute s***. I am seeing consistent 180-185 oil temps all the time read right off the fuel temp sendor.

2) I have a fuel temp sendor on my return line. My return line temps stay between 150-165 depending on fuel demand. Which proves that the oil cools off between the IP and the injectors, at least IMO. Proving injection line heaters worth it.

3) Back to timing.... Timing was alot less advanced and infact retarded in low load situations. All of my tests were done at a consistent 2500 RPM (cruise control) for 20-30 minutes straight monitoring timing. High load (going up decent grades) showed advanced timing anywhere from 2-4 degrees advanced which seemed a bit low to me beings I was seeing 2-2.2 at idle on diesel.
At low load, flat road situations I finally saw retarded timing numbers. .4 deg ATDC was the lowest I saw but again, retarded timing is never good on WVO. A lot of the time, timing was sitting at 0 deg being neither advanced or retarded. An interesting note, group 4 has two categories one being specifed timing and one being actual timing. It seemed at low load operations specified timing always wanted to be more retarded (1.6 ATDC) however actual always stayed within .4 ATDC and above. It seems the ECU wanted to pull timing back even further, however the mechanical aspects of the pump did not allow it to do so.

So this leads me into my point. The fuel temp sendor modification is VERY IMPORTANT. I have not done this yet but will do so very soon and again perform the same tests. I believe this will solve any issues of retarded timing and if not I can raise a deg or two by using VAG COM in adaption 4.

Another note of importance. My timing is advanced by nature on diesel. It is how it is physically set up to be. .4 deg retarded may or may not be a problem but I know advanced timing on WVO is always better. For people who don't have a VAG COM or don't do their own work on there car, they do not know where there timing is set on regular diesel fuel. If your timing is not set advanced you may run into MUCH more problems with retarded timing on higher fuel temperatures. Going back to how specified and actual were different, it seems to me that if your timing is set up in the middle of the graph or towards the bottom of the graph (retarded) the ECU may be capable of pulling timing back even further.

The ECU retards timing on higher fuel temps, this is a definite. However, this is the bigger problem with this. How much retardation to the point where it could cause combustability problems is different on everyones car. If your timing is set on the middle line of the graph or even part way retarded, you could have major problems with running retarded, i.e problems with combustion, deposits....you know the drill.

As a wrap up. It seems the ECU is very capable of pulling back 2-3 degrees of timing in normal highway, consistent RPM driving. Depending on where your timing is set to be, this could be a huge problem or maybe a small concern. For my car it seems to be a small concern, however I will still do the fuel temp sendor mod. 2 deg more advanced on WVO seems to be a great number to shoot for collected from different forums.

Just my two cents....I will report again with fuel temp sendor mod in effect. Tonight I also may have the opportunity to idle on WVO after my long highway run to maybe see where timing is on my TDI graph.

VAG COM is a great tool!!!!
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WVO no More 187k

Last edited by T'sTDI; August 30th, 2008 at 19:57.
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Old August 30th, 2008, 21:47   #2
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Haven't been running WVO for a while, but when I was......

1. After a TB job at a local import shop, my timing was set halfway between center and bottom. I didn't know that until many 1000s of miles later when I got access to a VagCom. I set it to halfway between center and top. Never measured timing while driving, but at idle, I seemed to stay about wher it was set regardless of fuel temp.

2. My WVO temps INCREASED post IP, usually 10-20 degrees (170 in, 180 out). I think this is why there is a fuel sensor in the IP. Since the IP loops the diesel and is connected to the block, heat from combustion will transfer to fuel in the IP. Now, my preIP sensor was on the supply valve outlet and my post-ip sensor was in the WVO filter head, so maybe it was just cooling from filter to supply valve, but my vegtherm was in that line, so I doubt it. FYI, YRMV.

I have always wondered if the "reported timing" is the actual timing or just the raw data the ECU is using to makes its decision?
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Old August 31st, 2008, 07:25   #3
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T's, with the fuel temp sensor mod, be aware that a few folks got a CEL with this mod. On mine it took several days before the CEL appeared. FWIW. Seems to happen on newer cars, mine's an 03.
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Old August 31st, 2008, 10:28   #4
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Quote:
Originally Posted by Honeydew
T's, with the fuel temp sensor mod, be aware that a few folks got a CEL with this mod. On mine it took several days before the CEL appeared. FWIW. Seems to happen on newer cars, mine's an 03.
Heh been there done that already. Got that "off road use" EGR block off right now and I get the BS "excessive flow...blah blah" code that I stare at all the time. It makes me want to get chipped just so I can ask them to put it out.

I thought codes were being set when they did both the fuel temp sendor and air intake (FAT mod, if you will) From what I gathered in that thread the fuel temp resistor took well but the ECU set the code when doing the same thing with the air intake.
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Old August 31st, 2008, 10:37   #5
T'sTDI
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Quote:
Originally Posted by sdeck
My WVO temps INCREASED post IP, usually 10-20 degrees (170 in, 180 out). I think this is why there is a fuel sensor in the IP. Since the IP loops the diesel and is connected to the block, heat from combustion will transfer to fuel in the IP. Now, my preIP sensor was on the supply valve outlet and my post-ip sensor was in the WVO filter head, so maybe it was just cooling from filter to supply valve, but my vegtherm was in that line, so I doubt it. FYI, YRMV.
I think my temp sendors are placed in more accurate spots to make the conclusion that it cools the oil. I was reading 180-185 in through VAG COM readings in group 4. My 150-165 is read right off the return line from the pump. Theres about 4 inches of hose and then my temp sendor. Your temp sendor could be giving false readings because yours is located where oil is being heated from coolant, IMO.
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Old August 31st, 2008, 11:01   #6
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Quote:
Originally Posted by T'sTDI
I thought codes were being set when they did both the fuel temp sendor and air intake (FAT mod, if you will) From what I gathered in that thread the fuel temp resistor took well but the ECU set the code when doing the same thing with the air intake.
I got fuel temp sensor implausible with the fuel temp sensor mod only, air intake stock.

Edit: another 03 w/ same experience

Last edited by Honeydew; September 2nd, 2008 at 14:28.
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Old August 31st, 2008, 18:53   #7
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Quote:
Originally Posted by T'sTDI
I think my temp sendors are placed in more accurate spots to make the conclusion that it cools the oil. I was reading 180-185 in through VAG COM readings in group 4. My 150-165 is read right off the return line from the pump. Theres about 4 inches of hose and then my temp sendor. Your temp sendor could be giving false readings because yours is located where oil is being heated from coolant, IMO.
Perfectly plausible by me. FWIW, I seemed to have a disconnect between my temp sender and the VagCom reading. Always seemed about 20 degrees off between them. IDK which is right. I also noticed that if I grounded my vegtherm near the temp sender ground, it really screwed up the sender reading. Also, when running on WVO (VT off) in summer traffic, my pre-IP readings would often get to >220F (I would switch back to dino). I don't think the heat could come from the coolant heater since my thermostat always reads 190 (I know dash gauge +/- 50 or so), so I always assumed IP was heating it up. Can't prove it either way from my end, just my 2/100ths of a buck
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Old August 31st, 2008, 21:32   #8
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Quote:
Originally Posted by sdeck
Perfectly plausible by me. FWIW, I seemed to have a disconnect between my temp sender and the VagCom reading. Always seemed about 20 degrees off between them. IDK which is right. I also noticed that if I grounded my vegtherm near the temp sender ground, it really screwed up the sender reading. Also, when running on WVO (VT off) in summer traffic, my pre-IP readings would often get to >220F (I would switch back to dino). I don't think the heat could come from the coolant heater since my thermostat always reads 190 (I know dash gauge +/- 50 or so), so I always assumed IP was heating it up. Can't prove it either way from my end, just my 2/100ths of a buck
Its funny I have the same sort of problem with my temp sendor off of my FPHE. I wanted it to be as close as possible to my FPHE to know when I could switch over the fastest. Our coolant is 190 deg, or so the gauge reads.... my FPHE temp sendor has shown temps in excess of 225 just as yours seems to do also. So what gives??? Unless our coolant temp gauges are lying, I have no idea where I'm getting the extra heat. It truly baffles me.

I hooked up VAG COM and was very pleased and relieved to find the fuel temps at the sensor in the pump showing 180-185 deg. This "mystery" if you will, could be the reason for our discrepencies.

Quote:
Originally Posted by sdeck
just my 2/100ths of a buck
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Old August 31st, 2008, 22:47   #9
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I would reccommend having the mechanical timing at the top of the graph. You can also set the idle adaptation to 3-4 deg BTDC at idle (I have no issues).. but I am not sure if that should be set on WVO or not because I don't run that. I am thinking that idle timing isn't affected by the fuel temp, because when I did the fuel and air temp mod, I didn't notice any timing change at idle.

Good luck and hope you can keep your grease burners happy with advanced timing!
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Old September 1st, 2008, 19:15   #10
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Update

I performed the fuel temp mod. Fuel temps were reading 9.8 deg C instead of the 30 or so it was reading before. Timing went up from 2.2 deg before the mod to 2.4-2.6 deg BTDC. I also bumped up the timing a bit in adpation 4 to 2.6-3.0 deg BTDC and I am very happy with that. I noted less smoke at idle, which I have had problems with and more low end power at lower RPM. Overall, car feels much more stronger.

Heres where it gets even better. Injecting vegetable oil at 180-185 temps (VAG COM confirmed) with the fuel temp sendor in effect, the temps were only reading a maximum 20.5 deg C. Timing also stayed in check especially in low load conditions. I stated above that timing was somewhat retarded in low load situations, .4 ATDC.

Timing was never seen below 1.3 deg BTDC on vegetable oil. Timing was even more impressive on acceleration as it seemed to adjust timing just like it was on diesel fuel.

I noted less EGTS 50 deg or so.... and it seemed on veg it was more responsive, not that it was lacking response by no means. Another thing I noticed is before the mod my engine was a lot more quiet when injecting WVO. This has nothing to do with the lubrication of WVO but has everything to do with combustion. It is quieter because of the retarded timing. After the fuel mod my engine sounded very similar, such as that on diesel fuel.

I can't emphasize how important the fuel temp sendor mod is for the WVO crowd. I can't emphasize how important knowing where your timing is while burning WVO. Retarded timing is a problem and is IMO, one of the reasons why deposits occur on WVO. Timing NEEDS to be advanced for the longevity of your engine internally. Sure it will run fine on retarded timing, however the combustability is not that of what it was on diesel fuel.

This is a very easy modification and a very important one!!!!
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Old September 1st, 2008, 19:21   #11
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Good data Tony, keep it coming. Would you recommend that members either have vag-com or a scangauge to run a setup like yours to keep track of timing?
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Old September 1st, 2008, 20:07   #12
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Quote:
Originally Posted by nicklockard
Good data Tony, keep it coming. Would you recommend that members either have vag-com or a scangauge to run a setup like yours to keep track of timing?
Speaking only from experience with VAG COM, I think its a very important tool to have period but it really shines when you have questions burning WVO (at least I did). There are important things to know that VAG COM provdies that can contribute to a long life on WVO or a very short one.

I love knowing exactly what the oil temp in my IP is. With finding this, I found there is a good amount of support that proves the IP actually cools the oil before it hits the injectors. I know for certain that the oil does actually cool and that just because its 180 in the IP does not mean its 180 at the injectors.

Having a VAG COM not only will give you timing in any situation you can put your car through, but it will show you that hot fuel temps will indeed pull timing back to where it could be a problem. Assuming that mechanically your Cam shaft timing is setup right, you can adjust timing to what you want it to be, no more than 3 deg adv or 2 deg retarded is what popular opinion is here.

Group 13 in measuring blocks has to be the most useful information it can provide. Off the top of my head I don't know what its called, but in laymans terms it shows how hard the ECU is working the IP to derive a smooth idle across all 4 cylinders (at least in my words). All four injectors are monitored at idle and it can be a great way to catch an injector not up to Pop pressure spec or a streaming injector. AKA huge problems and major engine damage if let go for enough time.

I feel some engine modifications are needed on the TDI to be successful. For those who are not running the resistor inline with your fuel temp sendor, I can assure you in many cases your running retarded timing which is not a good thing. Popular opinion by a lot of people from the IDI crowd feel timing should be adjusted 2 deg advanced and this makes sense to me. It gives the oil the max amount of time to atomize and burn, and I will also note, I see no smoke through rearview headlights at night on the highway on veggie.

This is only the tip of the iceberg that I have done with my car to burn WVO but having a VAG tool to take readings and doing the fuel temp resistor mod are both simple and good ideas while on WVO.

By the way.... I took timing readings at idle with the TDI timing graph and the fuel temp resistor mod in effect and it was uneffected. It basically read the same thing and came up with a fuel temp of 70 deg, could of very well been the actual fuel temp, however when I rechecked group 4 the fuel temp was 10 deg C. Interesting.....
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WVO no More 187k

Last edited by T'sTDI; September 2nd, 2008 at 14:34.
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Old September 2nd, 2008, 12:38   #13
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What resistance did you use for the fuel temp? Was it the same as listed in the thread for the mod? Also, did you do the intake air temp too? I did it, since supposedly warmer air retards timing too, which is probably due to NOx concerns originally.
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Old September 2nd, 2008, 14:08   #14
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Quote:
Originally Posted by T'sTDI

I love knowing exactly what the oil temp in my IP is. With finding this, I found there is a good amount of support that proves the IP actually cools the oil before it hits the injectors. I know for certain that the oil does actually cool and that just because its 180 in the IP does not mean its 180 at the injectors.
I really like all the work you are doing determining the how timing affects combustion and think this is important stuff in moving towards a better WVO system. and increased reliablility.

This is the one part i am kind of uncomfortable with. When you use an inline temp sensor on the IP return line and compare that value against the IP's built-in temp sensor, i think you may be making some assumptions that may skew your results. The 2 sensors are not calibrated the same and will have some variation in scale that can be affected by a number of variables. You may be correct in saying that the WVO temp decreases from the time it enters the IP to the time it gets to the injector, but i'm not quite sure about it. I think that the best way to measure how much the IP causes the fuel to heat up or cool down is by using two identical sensors. OIne placed on the IP supply line as close to the IP as possible, and one placed on the return line as close to the IP as possible. The returned fuel should be a fairly accurate measure of the injector fuel temp since the returned fuel actually comes from the injector itself, with some factor taken into account for any losses along the way.

Anyways, likle i said, i like the work you're doing and as soon as i get some time, i will look into the sensor mod.

Steve
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Old September 2nd, 2008, 14:11   #15
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Quote:
Originally Posted by robnitro
What resistance did you use for the fuel temp? Was it the same as listed in the thread for the mod? Also, did you do the intake air temp too? I did it, since supposedly warmer air retards timing too, which is probably due to NOx concerns originally.
I chose not to do the air intake because from what I gathered in the thread, that was where people were having problems with throwing CEL's. IMO, I feel fuel temps may have more of an impact on timing then air temp because we are purposely injecting extreme oil temps that the ECU was never suppose to see. However, I don't know if this is true or not because I myself have not experimented with it.

One reason is I don't feel I need to because I am seeing timing where I want it to be. Timing was taken in the summer so my timing is set up for hotter temperature and again timing is where I want it to be, so I don't see it as a huge issue.

I may have the opportunity to take some readings at idle on VO tonight back home from my commute.

What I have learned from all of this research is that a few deg of timing makes one hell of a difference. Without a doubt, I can audibly hear differences with combustion noises before I messed with timing parameters and I knew that was not a good thing. After performing the modification, there are very few differences between my car on d2 and on oil.

Knowing the above, I feel TDI's need to address this because they are a unique breed that logs many parameters with timing. Old IDI's never had this capability. Food for thought.....

O yeah... by the way the resistor was the same as used in the thread. 2.5K 1/4 watt, I followed exactly what jackbombay did. I have mine setup to where I can remove it very easily. I removed the resistor (open circuit) and temp readings defaulted to -5.4 deg C and also threw a code (FYI). I made it removable because I was unsure if a 2.5k resistor would be enough to accomplish what I wanted. I was pleased to see that it keeps temps very close to what they are when you start your engine. It definitely "resists" and slows readings. On an hour drive I saw my temps only go up about 10 deg and it held steady on VO. So it don't look like I will need a different resistor.
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WVO no More 187k

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