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I don't think the post-shutdown run-on is going to do anything to save an engine. The water pump is no longer running, and the hot parts of the engine are above the radiator so there's going to be no convection to keep the water moving either. Mostly (I think) it's just done to prevent boil-over as the heat-soak transfers from the engine to the water and the pressure goes up.
Hi jeyjey,
I believe Devia is referring to the DME overheating. The electronics are experiencing higher current draw when retarding the spark for lower octane fuel to avoid pre-ignition.
Yes, the low speed radiator fan runs after the ignition is turned off to lower coolant temperature. There is a possibility that the engine coolant temperature could increase sufficiently to blow the head gasket, all aluminum engine, without removing coolant heat from the radiator.
I think what is going on with the S2 is a small leakage current form the fan switch. In theory, there is enough current to activate the high-speed fans, but not enough to illuminate the LED. I have redesigned the fan activation circuit to account for this, I should have a new round of prototypes in a couple weeks.
- Joe
Since the engine was running at idle and not that warm, after the fans ran for a bit at SLOW speed they would have normally cycle off... which they started to do, but when they started to shut off they immediately jumped to FAST mode, and stayed that way for as long as the engine was running. I let the engine idle for quite awhile and the fans continued to run on FAST. It was like they got latched in that mode. I then shut the engine off and the fans stopped, but turning the key to ON, the fans ran again and at the FAST speed. Guess I need to see if this happens with my stock relay too. It does seem like there's an issue with the radiator thermal switch.
What would be the benefit for me to have a solid state relay, I have a 951 1986 twin fan of course. I deleted the A/C with all the parts that came with it (radiator, etc..)
Does these relays have the habit to fail like the ECU/fuel pump relay ?
Thanks,
Charles
If you live in a cooler climate then I suppose you can get away with deleting the AC system. I live in basically Phoenix AZ, so I invested heavily in restoring the AC in my 951. I plan to invest even more in my 944NA AC system, the 951 still struggles when it is above 110F (43C) outside. I plan to try a bidirectional condenser this time rather than the serpentine type. Does your windshield fog up when it rains? I would still keep the AC in my car for no other reason than to pull the moisture out of the defroster.
Porsche superseded the fan relay design no less than four times, that is a clear indicator to me they where having issues much like the DME Relay. I believe these relays do fail in a verity of ways, mostly with diminished and/or intermittent functionally. It is likely many 944s and 968s (Duel Fan) are running entirely on high-speed fans because the low-speed circuit failed, possibly many years ago. Of course low-speed can fail due other issues like the temperature switch, or resistors and associated wiring. So I would guess the "diagnostics" version of the Solid-State Fan Relay will be popular for no other reason than to identify these other failure points.
Since the engine was running at idle and not that warm, after the fans ran for a bit at SLOW speed they would have normally cycle off... which they started to do, but when they started to shut off they immediately jumped to FAST mode, and stayed that way for as long as the engine was running. I let the engine idle for quite awhile and the fans continued to run on FAST. It was like they got latched in that mode. I then shut the engine off and the fans stopped, but turning the key to ON, the fans ran again and at the FAST speed. Guess I need to see if this happens with my stock relay too. It does seem like there's an issue with the radiator thermal switch.
This will not happen with a stock fan relay, it is not normal operation. The factory relay needs a significant amount of current to energize the coil to close the mechanical contacts, a small amount leakage will not be enough. The SSR Fan Relay, on the other hand, requires basically no current, it is activates entirely off voltage. The updated SSR Fan Relay will resolve this, It now has a circuit that explicitly programs the fan activation threshold. I will send you one for testing once I have it build up.
If you live in a cooler climate then I suppose you can get away with deleting the AC system. I live in basically Phoenix AZ, so I invested heavily in restoring the AC in my 951. I plan to invest even more in my 944NA AC system, the 951 still struggles when it is above 110F (43C) outside. I plan to try a bidirectional condenser this time rather than the serpentine type. Does your windshield fog up when it rains? I would still keep the AC in my car for no other reason than to pull the moisture out of the defroster.
Porsche superseded the fan relay design no less than four times, that is a clear indicator to me they where having issues much like the DME Relay. I believe these relays do fail in a verity of ways, mostly with diminished and/or intermittent functionally. It is likely many 944s and 968s (Duel Fan) are running entirely on high-speed fans because the low-speed circuit failed, possibly many years ago. Of course low-speed can fail due other issues like the temperature switch, or resistors and associated wiring. So I would guess the "diagnostics" version of the Solid-State Fan Relay will be popular for no other reason than to identify these other failure points.
Living in Québec, Canada has pros and cons. Pros are that we have a very nice weather from May until October with peak temperature at 35C in July for about a week or two, humidity @ 100% is very unpleasent that is if you live in or around Montreal . Outside of Montreal, it never get's over 30 C 50% humidity. Even close to St-Laurence river, bring a coat... It gets cold at night (15-10 C) with a nice wind. That's why I deleted my A/C. Cons is winter... No, you don't ride your 944 on snow... Bad idea.
To get rid of fog, I followed my uncle suggestions, he has a small fleet of Cessna to cary hunters and fishing tourists to remote spots. To get rid of fog, he jus open a bit of the side window. Bingo, it's all gone. On my 944, it happened on a heavy storm so I just opened the roof on the highway, no fog. In the morning it's caused by dew point... No big deal.
I plan to change my hatch back window for a 3/16 inch Lexan. Much lighter and supposablyfog free... Available here: https://www.gt-racing.com/porsche-windows/
I need to redo it anyway, like all 944s, it leaks and tend to detach on the top...
Reading on your comments, I will put this in my list. Just the amps saving and diags are very good. Will wait for it to be available...
I just got the Live Graphs basically working, and should have an update on the website soon! This is a huge step forwarded, the ability the graph sensors relative to each other is by far the most powerful way to diagnose and evaluate your engine. In the video below, I am graphing 4 related sensors: RPM, AFM, NBO2 and Injection Pulse Width. Note how the AFM signal mirrors the Injection Pulse Width. And also how the Injection Pulse Width has a smaller ripple riding on it that is the inverse mirror of the Narrow Band O2 Sensor. This is normal and how the DME maintains the air-to-fuel ratio at stoichiometric. As I mentioned in a previous post, the NBO2 can only tell the DME if the fuel mixture is rich or lean, but not by how much. So the DME must constantly cross the lean/rich threshold to know it is hitting its AFR target. Now you can actually see this relationship working in real time!
In this video I am stopped and about to accelerate to merge with traffic on the freeway. I am intentionally pressing the throttle at odd times to see the effect on the graph. Sorry about the quality and wind noise, it is over 100 degrees out and no AC in my 944 NA. My Windows Tablet is getting very hot and reducing the CPU speed, this is why the frame and video quality is less than ideal. The software captures perfectly sooth in real life, I will try to post anther video in a day or two.
Getting closer to releasing Live Graphs for the FocusOBD software! This video is one of the first test drives. Note how the AFM signal mirrors the Injection Pulse Width. And also how the Injection Pulse Width has a smaller ripple riding on it that is the inverse mirror of the Narrow Band O2 Sensor. This is normal and how the DME maintains the air-to-fuel ratio at stoichiometric. The NBO2 can only tell the DME if the fuel mixture is rich or lean, but not by how much. So the DME must constantly cross the lean/rich threshold to know it is hitting its target.
Does this indicate that the RPM sensor gives a wrong output ? It is bran new but I'm not sure if it is correctly installled (distance from the sensor to the starter whee hard to tell...)
Other question, the starter ring has 132 tooths... Why does it shows the double ?
Does this indicate that the RPM sensor gives a wrong output ? It is brans new but I'm not sure if it is correctly installled (distabnce fromn the sensor to the starter wheel)
If you look at the "Flywheel Starter Ring" sensor, note that 264 teeth was counted on the last revolution. The expected flywheel sensor count for your 944 Turbo is 132 teeth, anything more than 132 or less than 129 less will increment the error count. If OBD+ sees the flywheel tooth count to be 130 or 132 it will assume your 944 is a NA or Turbo respectively, the error tolerance at that point will be +/- one tooth.
Are you able to start the engine?
Does the "Flywheel Starter Ring" count jump around different values or is it consistent? Note, the last few values captured as the engine stops rotating can be invalid.
If you look at the "Flywheel Starter Ring" sensor, note that 264 teeth was counted on the last revolution. The expected flywheel sensor count for your 944 Turbo is 132 teeth, anything more than 132 or less than 129 less will increment the error count. If OBD+ sees the flywheel tooth count to be 130 or 132 it will assume your 944 is a NA or Turbo respectively, the error tolerance at that point will be +/- one tooth.
Are you able to start the engine?
Does the "Flywheel Starter Ring" count jump around different values or is it consistent? Note, the last few values captured as the engine stops rotating can be invalid.
- Joe
Yes the engine starts. I just notices the tooth count after I shutdown the engine so that snapshot is when the engine was stoped,
The engines runs correctly, idle stables, untill the loop closed and the ECU startes reading all the sensors. I noticed this exacly when the dash oil pressure starts displaying a reading the idle drops and become erratical... That's when I strated looking at the RPM sensor error count...
I'm just questionning the starter ring sensor not being at 0.8mm from the ring...
I willl do more runs tomorrow. I do not do test runs on street as the engine is not stable... I'm trying to find the cause of this.
Yes the engine starts. I just notices the tooth count after I shutdown the engine so that snapshot is when the engine was stoped,
The engines runs correctly, idle stables, untill the loop closed and the ECU startes reading all the sensors. I noticed this exacly when the dash oil pressure starts displaying a reading the idle drops and become erratical... That's when I strated looking at the RPM sensor error count...
I'm just questionning the starter ring sensor not being at 0.8mm from the ring...
I willl do more runs tomorrow. I do not do test runs on street as the engine is not stable... I'm trying to find the cause of this.
Thanks,
Charles
Shoot... Now it's at 0 RPM... Will check the wiring...
05-17-2021, 12:33 PM
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