Eric Maurier
Veteran Member
Hi all!
Some may remember my very theoritical thread about the coolant glow plugs and under which conditions they were turned on.
After some experiments, I discovered that the IAT (intake air temp) that triggered the thing was about -10°C on my ECU, provided the coolant temp was under 55°C.
This condition on the IAT was achievable when the IAT sensor G72 was at a resistance of about 10KOhms. So I figured out a way to add 10KOhms to the G72, so that it would always read below -10°C and therefore trigger the coolant glow plugs when the engine is cold. Well, not really "always" but when I want it to. This means a switch in the car.
In order not to forget to put it back to normal when the coolant is warm, I integrated a red light that turns on when you hit up the switch.
Here's the scheme:
And I though to myself, it would be good as well to know when the glow is really working. So I added a flashing LED, triggered on a relay. Which one? The J359, that's to say low heat output. This relay feeds plug #1 (out of 3), the plug that's in the middle . The J360 is the high heat output and it feeds plugs #2 and #3. I found those two relays under the hood thanks to the engine output tests with VAG-COM (heard them click!). J359 was marked 53 and J360 was marked 100. Here's the scheme:
All this material was made to fit in a round photo film box. State of the art for french size reduction in electronics! ;-) Sorry no picture for now, I have no equipment for this
Now, time for test drive!
Cold start, few degrees above freezing, a few seconds to demonstrate how it works and then I cranked the engine. On the top of the graph are 3 binary values: afterglow in brown, low heat output in blue, high heat output in red. If I had put them on the same line, it wouldn't have been understandable.
Afterglow starts right after the engine (be careful, afterglow is about the ENGINE glow plugs).
About ten seconds after the start of the engine, there is no restriction to a start of the coolant glow plugs (all bits turned to 0, not visible on the graph) but the thing starts only a few seconds after that.
There we go!
Low heat output until the end of the afterglow. Then, once the afterglow is finished, it's high heat output that's used. We have some time on hi and then BOTH (that's the three glow plugs) are activated. I didn't find any reason for the change but the 200 seconds between the beginning of hi and the beginning of hi+lo.
Then we go all the way with hi+lo, until the coolant reaches 80°C. It is then stopped. I already hear you: I said the temp was 55°C. Well, that may not be incompatible. Maybe the thing triggers at 55°C but stops at 80°C.
Afterwards, I switched down my mod, which explains the sudden rise in IAT. Well, sudden, not that much: the rise seems to be damped by the ECU.
Special for Velvetfoot: you'll notice I included generator loading. And you were wondering the load given the afterglow. Well, VW engineers must have been concerned as well, since as we've just seen, they prevent hi output while there's an afterglow. So the alternator load didn't go beyond 70%.
For the heating: it triggers NOTHING at all. I tried to put it for a few seconds to max heat, max fan speed, and it didn't change a thing, for each and every stage. So for an optimal engine warm-up and a 038 906 012 H ECU, I advise to leave the heating at cold. Others ECU: please try to see if it differs!
Now, my biggest concern before the ride: the impact of IAT on specified boost. I say before, because just watch those graphs:
1)The overview of a short run on a motorway, at moderated speed (90-130 km/h).
I found 2-3 places where I could switch up the mod and lower the IAT to about -15°C and see the impact on group 11 (boost), at real steady speed at throttle position. Plus the idling at the end.
Now, let's have some kind of zoom. You can refer to the overview graph using the X axis, the time in seconds.
2)
3)
4)
So, as I said, the effect is obvious. First, I must acknowledge that there is indeed as consequence, though I still don't see no real need for it. The consequence is a slight decrease in specified boost, should it be at light (90 km/h), medium (130 km/h) load or idling. So, what more could I ask? No only this mod warms my engine faster, but what's more it protects (a little bit) my turbo by requesting less boost. There's as well enough air to burn the fuel, since my EGR unfortunately doesn't work ;-) Those Skodas aren't reliable cars, that's true... :-D
If I didn't make myself clear enough, this mod will only be used for a coolant temp under 80°C, since I don't need it when above and it could make the engine smoke at full load.
Comments and questions welcome as usual
Some may remember my very theoritical thread about the coolant glow plugs and under which conditions they were turned on.
After some experiments, I discovered that the IAT (intake air temp) that triggered the thing was about -10°C on my ECU, provided the coolant temp was under 55°C.
This condition on the IAT was achievable when the IAT sensor G72 was at a resistance of about 10KOhms. So I figured out a way to add 10KOhms to the G72, so that it would always read below -10°C and therefore trigger the coolant glow plugs when the engine is cold. Well, not really "always" but when I want it to. This means a switch in the car.
In order not to forget to put it back to normal when the coolant is warm, I integrated a red light that turns on when you hit up the switch.
Here's the scheme:
And I though to myself, it would be good as well to know when the glow is really working. So I added a flashing LED, triggered on a relay. Which one? The J359, that's to say low heat output. This relay feeds plug #1 (out of 3), the plug that's in the middle . The J360 is the high heat output and it feeds plugs #2 and #3. I found those two relays under the hood thanks to the engine output tests with VAG-COM (heard them click!). J359 was marked 53 and J360 was marked 100. Here's the scheme:
All this material was made to fit in a round photo film box. State of the art for french size reduction in electronics! ;-) Sorry no picture for now, I have no equipment for this
Now, time for test drive!
Cold start, few degrees above freezing, a few seconds to demonstrate how it works and then I cranked the engine. On the top of the graph are 3 binary values: afterglow in brown, low heat output in blue, high heat output in red. If I had put them on the same line, it wouldn't have been understandable.
Afterglow starts right after the engine (be careful, afterglow is about the ENGINE glow plugs).
About ten seconds after the start of the engine, there is no restriction to a start of the coolant glow plugs (all bits turned to 0, not visible on the graph) but the thing starts only a few seconds after that.
There we go!
Low heat output until the end of the afterglow. Then, once the afterglow is finished, it's high heat output that's used. We have some time on hi and then BOTH (that's the three glow plugs) are activated. I didn't find any reason for the change but the 200 seconds between the beginning of hi and the beginning of hi+lo.
Then we go all the way with hi+lo, until the coolant reaches 80°C. It is then stopped. I already hear you: I said the temp was 55°C. Well, that may not be incompatible. Maybe the thing triggers at 55°C but stops at 80°C.
Afterwards, I switched down my mod, which explains the sudden rise in IAT. Well, sudden, not that much: the rise seems to be damped by the ECU.
Special for Velvetfoot: you'll notice I included generator loading. And you were wondering the load given the afterglow. Well, VW engineers must have been concerned as well, since as we've just seen, they prevent hi output while there's an afterglow. So the alternator load didn't go beyond 70%.
For the heating: it triggers NOTHING at all. I tried to put it for a few seconds to max heat, max fan speed, and it didn't change a thing, for each and every stage. So for an optimal engine warm-up and a 038 906 012 H ECU, I advise to leave the heating at cold. Others ECU: please try to see if it differs!
Now, my biggest concern before the ride: the impact of IAT on specified boost. I say before, because just watch those graphs:
1)The overview of a short run on a motorway, at moderated speed (90-130 km/h).
I found 2-3 places where I could switch up the mod and lower the IAT to about -15°C and see the impact on group 11 (boost), at real steady speed at throttle position. Plus the idling at the end.
Now, let's have some kind of zoom. You can refer to the overview graph using the X axis, the time in seconds.
2)
3)
4)
So, as I said, the effect is obvious. First, I must acknowledge that there is indeed as consequence, though I still don't see no real need for it. The consequence is a slight decrease in specified boost, should it be at light (90 km/h), medium (130 km/h) load or idling. So, what more could I ask? No only this mod warms my engine faster, but what's more it protects (a little bit) my turbo by requesting less boost. There's as well enough air to burn the fuel, since my EGR unfortunately doesn't work ;-) Those Skodas aren't reliable cars, that's true... :-D
If I didn't make myself clear enough, this mod will only be used for a coolant temp under 80°C, since I don't need it when above and it could make the engine smoke at full load.
Comments and questions welcome as usual
