This thread is about: function of the Exhaust ECU aka SDECU for slow-down ECU flashing slow down malfunction indicator light AKA SDMIL solid red slow down mil with engine performance reduction How to delete this terrible kluge only the Italians could have made. If Ferrari would just make decent parts that worked I would not feel the obligation to relieve the Ferrari driving public from this amazing plague. The SDMIL is an idiot light. These lights are supposed to save your bacon like the oil pressure light but the problem is that these SDMIL's have never been reliable. In 0ver 20 years of auto manufacture Ferrari still does not have this system right and they are nor cheap to fix nor do real pros have a longterm soultion for their bugginess. So how does the system work? Cats get hot and can cause car-b-ques or bad running as a result of improper combustion first. The SDECU monitors cat temps in a safe zone. That info plus O2 sensor info etc are all part of the closed loop combustion function of the motronic ECU. On the 355 the SDECU SDMIL's first warning is 1656-1792F. The second warning is 1728-1864F where the ECU cuts power to the car to force you to slow down and make less heat. On the 550 the first SDMIL warning is 1634-1806F and the second warning is 1692-1864F. So lets just say for convenience the first warning SDMIL is 1700F and the second warning is 1800F. I do not know if these numbers are consistent amoung Ferrari models You guys with different cars feel free to chime in. What I have found: 700F cats start to work 1000F at idle 1100F prolonged cruise 1300F about as hard as you can legally drive On the 550 there is a 4 pin plug where 3 are used for the SDECU and the SDECU's are by the bonnet hinges. I have back probed the wires. There is only 12V to the ECU with key on. SD ECU passenger side has: Green wire= 12v hot Black= ground White = trigger SD ECU Drivers side has: Blk/Brn wire = 12V hot Black= ground White = trigger Image Unavailable, Please Login Image Unavailable, Please Login
It was our genius Eric355 (he figured out how to clone the key fobs) who gave me the data and the idea to trick the SDECU's. I attached a 1.5V battery to the trigger and ground wire and the SDMIL would go out. How convenient I got tons for 1.5V batteries around. You can't just unplug the SDECU like you can on a 348 2.7 motronic. The 5.2 motronic is smarter and will throw a code without an SDECU input to the motronic. That input happens to be a voltage between 0 and 5V. More volts = SDMIL. 1.5V makes the SDlight very happy. So here is my kluge to kill the SDMIL and take the SDECU totally out of the system and my car has no clue its gone. Online you can buy from anywhere a 12v cigarette lighter power supply that outputs 1.5 volts for less than 10 bucks! I wired the SDECU plug ground to a chassis ground. I wired a trigger wire to the 1.5V output. I hardwired the cigarette lighter adapter near the driver's SDECU. I ran another 1.5V wire all the way over in the red silicone wrap to the passengerside SDECU trigger. So when the key goes on the old SDECU power turns on and powers my cigarette lighter adapter instead of the SDECU. That automatically puts out 1.5volts and defeats the SDECU system and the car runs perfectly. This has been tested for about 6 months now. So now you are on Manual! You need a way to monitor the cat temps visually like an oil pressure gage on your dash because you don't want to miss a flaming cat. Image Unavailable, Please Login Image Unavailable, Please Login
So to monitor the cat temps manually you can buy dual EGT guage with 2 thermocouples for about $140 bucks from Aircraft spruce and specialty. The threads in our cats are 8mm x 1 pitch for a direct screw in or you can weld a bung or drill and clamp the thermocouples if you want to retain the stock SDECU system TOO! I just unscrewed the ferrari thermocouples and screwed in the new thermocouples. I drilled a small hole under the aero-undertray and into the ECU kickpanel area. I TIG welded an aluminum box to fit the guage and welded the box onto the factory aluminum kick panel. Then the upholstery guy covered it. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
If I had a wish list one thing on it would be dual EGT gages AND the automatic SDECU system that works. You can do what I did and have no confidence in the Ferrari system and delete it and go manual. You can wire in the EGT guages and keep the Ferrari system and have maybe the best of both worlds. You would at least be able to verify that the SDlights were giving you the right info. You can just ignore my hot air and keep paying Ferrari for wonky parts. One of these days I'll build a better electronic SDECU that works with Japanese efficiency. If we are lucky we can get Dave Helms to make it. What do you think Dave? I know you need another project.
FBB you da man. We need to save this thread to show to those who say, "All those Luca era cars with their electronics are going to be disposable cars." Electricity is electricity. Like Dave Helms' avatar, there will always be someone who can figure out how to make it flow from one place to another. Dale
Why use batteries when a simple 2 resistor voltage divider produces the same result without having a yearly battery change?
Battery was used to test my theory. Continue reading I talk about hardwiring a voltage reducer that takes 12V source to 1.5V then my circuitry is active with the ignition key and uses the source voltage of the SDECU to help me eliminate itself.
Well done Carl !! I read your post about a voltage reducer to 1.5V. I don't think you need something too accurate for that particular application. A voltage divider with 2 resistors will be fine. The voltage will be a scaled value of the battery voltage, and will vary accordingly, but it will be more than enough to make the Motronic happy.
FBB, it should be trivial to make a small circuit - microcontroller w/ a DAC (PIC, Atmel AVR, etc) to handle the thermocouple and produce the right output voltage. (And cost like $30 to build - LOL) The key is to figure out what kind of thermocouple it is, what family so-to-speak, and then read the voltage thru an op-amp. A barebones thermocouple approach is at: http://www.circuitcellar.com/library/print/0503/moyer154/3.htm Any EE on FChat could design a board to do this.
Smart thinking BBob it always amuses me when you know there is absoluely nothing wrong with your car and a 1-4 or 5-8 light flashes on , in fact they are counterproductive as you learn to ignore them so your real time gauges are a great idea.
If the SDECU's are outputting DC voltage signals proportional to temperature, then they're probably not true ECU's, but are what we call thermocouple transducers or transmitters. These types of boxes take the thermocouple's millivolt signal in, and "amplify" it, as well as linearise it to have a 0-5 volt or 4-20ma signal (or similar) out. Ruggedized versions of these boxes are commercially available, so it probably wouldn't pay for someone to reinvent this wheel, unless the sole goal is to build something cheap, which I don't think is the true goal. What would be useful to know is: 1) What type of thermocouples are used (ie J, K, N, etc.), and 2) What is the range of output of the existing SD ECU? FBB, could you have a look at the color of the wires coming into the SDECU from the thermocouples? This will help indicate what type of thermocouples are installed. If the thermocouples are type K, and they follow the IEC color convention, there should be a black wire & a white one coming from the thermocouple. Since the system is Italian, I would expect the color code to follow the IEC convention in lieu of ANSI, which would be yellow & red for a type K. Once the type of thermocouple is known, a thermocouple simulator box could be connected to the SDECU in place of the thermocouple, and it could be ramped up to the maximum temperature expected, to see what the output of the SDECU is at that temperature. Once this is known, it would be fairly easy to specify the type of transducer required, then off we go to search for a ruggedised transducer/transmitter. However.......(playing devil's advocate for the moment) do we know definitively that it's the SDECU that is causing the problem? Perhaps it's the thermocouples themselves or their wiring to the SDECU? When dealing with millivolt signals, it doesn't take much of a problem to create bogus readings. But if FBB, or someone else, has already swapped SDECU's from right to left, and the problem follows the swap, then it's clearly the SDECU. If it's definitely the SDECU's causing the problem, and knowing the engine bay isn't the most hospitable environment for electronics to live in, it might be worthwhile to consider relocating the existing SDECU's under the dash, or in the console, etc. to see if that helps the problem before resorting to a non-Ferrari solution.
Cribbj Just to make this project complete I would like to work on this project with you. My brother is an EE but is not a ferrari guy and has no interest. We could ask him any specific questions but that is about it. The Ferrari Tcouple is red/yellow. The ones I used came with the gage and iirc are blk/white. Personally I don't trust the Ferrari Tcouple naymore than the SDECU. It is well known that the Ferrari Tcouples fail too but the SDECUs fail continually. I say just source a rugged box and compatable Tcouples with proper extension wires. The extension wires are important because I forget the reason but you need the right wires because the Millivolts are small etc etc... Then I would source the new SDECU box to produce x volts at 1700 and y volts at 1800. The range of needed voltage is 0-5V. I would need a way to accurately produce 1700 on a Ferrari Tcouple and working SDECU to find out its output voltage and then at 1800F or perhaps there is data that shows the output voltage at these temps. I kind of think I have seen such data on one of the diagnosis sheets. I'll have to ask Dave Helms. If I can find that kind of data can you find me the box?
Great, I look forward to assisting with this, in any way I can. I'm a EE (although I haven't really practiced the techie stuff in years) and a 550 owner & a hotrodder. It's interesting that the OEM thermocouple wiring is yellow/red. That could indicate that the thermocouple is using the ANSI color standard, and perhaps both it and the SDECU were designed/manufactured in North America. That conclusion might be a bit of a stretch, but it's possible. The extension wiring is important because all thermocouples operate on the basis of the voltage produced at the junction of two dissimilar metals. These same two metals must be maintained in all the wiring, and even the lugs where the wires are terminated, else errors will be introduced. That's where the thermocouple simulator (or calibrator) box comes in. Once the type of thermocouple has been identified and is known, you would unplug the thermocouple from the SDECU, and plug this box in instead, set the type of thermocouple desired, and dial in the temperature you want to simulate - it then produces exactly the millivolt output that that type of thermocouple would produce at that temperature. These boxes are commonly used in industry to do just what we're doing - finding the point of failure in a temperature control/alarm system. I can certainly find a ruggedised thermocouple transmitter box which is setup to output a linearised voltage signal for a thermocouple input, however a point of caution: we have to ensure that it produces exactly the same voltage output at exactly the same temperature as the original system. Otherwise the box at the other end of the SDECU signal (presumably the Motronic ECU?) won't be happy and the points at which the MIL's illuminate will be different, which is not what we want. The danger here is assuming that the Ferrari system conforms to an industry norm, and it may not. So we may need to "calibrate" the transmitter box to match the Ferrari system. That's why it's important to: 1) Identify the type of thermocouple which is used in the OEM system, which you've just about done. 2) Setup the calibrator box to simulate this type of thermocouple and substitute it in the circuit for the thermocouple 3) Ramp the calibrator through the expected range of temperatures, and confirm the MIL's illuminate at the expected points. At each point the MIL is illuminated, it's important to measure the output voltage of the SDECU. 4) Substitute a new ruggedised transmitter in the circuit for the SDECU, and ramp the calibrator through the temps again, and confirm the MIL's still illuminate at the same points. If not, it must be recalibrated to match the SDECU's output. (in principle, not difficult) If your EE brother has a thermocouple calibrator/simulator box, you can do these tests yourself, otherwise I can run them on my 550 when I return home (I'm out of the country for another 4 weeks)
........ watching and reading with interest. I look forward to seeing how you guys get on with this. Fair whack for giving it a whirl!
Ha! Little did I know when I expressed an interest in this how quickly I would find the information useful! Mine is a 360 and the other day I replaced the gearbox mount which involves working in close proximity of the thermocouples. I guess the wires inside the braided lines were very brittle because despite very delicate handling on my part, after reassembly I got the slow down flashing light within about 2 minutes of start up and clearly way before the cats could possibly be overheating. A few minutes investigation revealed a trigger out voltage of 1v on Bank 1 and 5v on Bank 2. I then tested the thermocouple with a resistance meter and found continuity on Bank 1 but no continuity on Bank 2. I left the meter on the plug for the Bank 2 sensor and did a little pushing, pulling and twisting on the shielded wire to the thermocouple and sure enough, I found that continuity came and went as I moved the wire this way and that. Quick fix to stop the slow down light - I bridged a few slivers of speaker wire from one side of the thermocouple plug to the other and then re-inserted it to the ECU, effectively giving it continuity again. Output on the other side of the ECU dropped to 4v, then 3 then 2 and finally to a pleasing 1v just like the good side. Quick battery re-set and Slow Down light now extinguished. Any joy on finding a replacement thermocouple? I guess since I only need one I might just go ahead and order it and be done with the problem but I'm conscious that the other one is probably as close to failure too. Additionally (of course) both my ECUs show signs of the (black) epoxy having separated from the side of the box. Obviously I've resealed with gasket goo but sure it's only a matter of time before one or other of them fails too isn't it? Anyway, thanks for the thread and tips above. With the information posted here I was able to easily diagnose the faulty component and achieve a simple work around so as not to have to endure that infernal light flashing away constantly. I will keep a close eye on the Cats though in the meantime!
Awesome! I've been trying to think of a way to do this too, I was only thinking of resistors and possibly a potentiometer but the batter charger idea is a great one and I will be trying this in the next few days. Does milliamp output of the battery charger come into play? If so, what's the maximum I should be looking for?
Just got back home after 4 weeks, picked up the car today and hopefully will be doing some simulations this weekend.
Look forward to it John. Jeff milliamps is not an issue just voltage. All the commercial 12V to 1.5V converters are probably less than 200ma. Just make sure you monitor exhaust temps another way. This system is important.
Eric355, Would you happen to know what size resistors would need to be used? Or do you need to know the miliamps going through the signal wire? I tried to measure the m/a's but couldn't for some reason get any reading at all with 2 different multimeters. I got voltage of over 5v at startup, and then drops to less than a volt at idle but no m/a's. Also, to do the voltage divider, am I right -> do you run a wire from the negative lead from the ECU through a resistor to a ground on the frame, then run a wire from the positive lead from the ECU through another resistor then attach to signal wire going back to ECU? If so and you know the sizes, please be specific as to which one goes where, thanks a ton! Jeff
I provided comprehensive engineering a while back for a resistive divider where 1.5v was required: http://www.ferrarichat.com/forum/showpost.php?p=140416240&postcount=9 It's easy to modify parameters for other outputs but the engineering must be complete, not seat-of-pants hobby guesses which, sadly, I'm seeing a lot of. We're talking a Ferrari and it deserves better.
FBB, I remember my 360 had cat ECU's that went bad...looked the exact same as the ones on your 550. Is the point of doing this so that you don't have to spend money on replacing these expensive ecu's each time they go bad? Regards, Pete
No. My original point was to find a reliable way to monitor the cats and or have some clue as to quality of engine running by using EGT. Every Ferrari owner since the 348 has had problems with this system failing resulting in anything from simple nuisance with loss of money to serious meltdown. Can you imagine how much Ferrari has made off of us because they choose not to fix the system? So the options are delete the system and monitor with EGT, or ensure that the system is reporting real data by verification with EGT as proposed here or redesigning the entire system to function as originally intended by cribbj (he is working on it) and forgetting about EGT. I chose option 1 as the quick initial fix having no faith in ferrari systems. Someone else will choose option 2 and straddle the fence. I hope we all get option 3 when it becomes available.
Thanks Paul, I'm experimenting with a 50ohm 10watt resistor and 3 10ohm resistors in series (80 total), then my voltage out, followed by another 10ohm 10watt resistor to the ground. I tested the voltage on my maxima, (putting all this on a breadboard and hooking it up to the car battery) and my voltage out was 1.58, perfect! I also looked for cell phone charges that output 1.5v and had no luck so I'm leaning toward this resistors on bb approach. Hmm, you think I need a fuse? Question to FBB: You describe running a wire from the side where the cp charger is to the other side. On the other side, do you simply run it to the signal wire and do nothing with the power and ground? You think this would cause cel to throw code like 'short to ground' or something like that? I also need to run to my third SDECU that goes up to the bypass valve.
Thanks everybody, I've implemented the resistor method on drivers side and test drove, went well, now must do passengers and bypass, I will post a new thread with my results and the reasons why I wanted to do this later, I don't want to divert this thread from fbb's design which I think is good. Thanks for the inspiration.
