Exhaust ECU

They only charged me $700 2 years ago.

 

The cat ecu's are the STUPIDEST thing Ferrari has put on the cars. I hated mine so much that I have completely removed them from the car, and have been running with out them for a few years now.

To answer your question, yes the car can run without the cat ecu's connected. However you will get a silent code stored in the Motronic ecu that is not getting a signal from the cat/s. Meaning that it will store the code but it won't give you a check engine light. The cat ecu's only monitor the temp of the cats, and then report that info to the Motronic's. The only time they affect the performance of the engine is if they are sending an "over heating" signal to the Motronic, which then the MOTRONIC will shut down the bank of cylinders that it is getting the over heating signal from, or THINKS it's getting a signal from. Other than that the stupid cat ecu's are good for squat in my opinion.

 

I think I have the same problem now. The slow-down 5-8 blinks and stay on for good 20-30 secs usually in 1st 5-10 mins from cold start and then disappears. There is no loss of power usually.

Best
P.

 

ferrparts.com sells the cat ECU for $600. you will get the updated one (with the green casing), I just got one about 1 month ago. I replaced one (1-4) which was giving false reading and shutting down my bank (my tech changed it and charged me about $800) and then bought another one as the 5-8 still has the old ECU and I was not getting the 5-8 test light when I first turned the car on. now the 5-8 comes on and goes off, so all is okay and I have an extra ECU. you can change the part yourself. $600 ain't no big deal to me, but if you only knew what was inside this thing, you would **** yourself. its probably some sort of amp and smoothing component that reads the voltage coming off the thermocouple, this is then connected to the motronic ECU. the cat ECU really isn't very sophisticated at all. actually, the thermocouple is a common type of wire pairing, so I bet this Cat ECU is pretty common too. other devices need to interpret this thermocouple just the same, it just won't be in the same fancy casing.

 

I have a set of custom cats in it now that don't have the bung holes for the thermocouples. But when I was running the old cats I just unplugged the cat ecu's and then took them out. Leaving the thermocouples screwed into the cat.

 

I'm going to hang onto my extra one for now... but there is not chip RAM chip inside that box. Its an amplifier and some logic (transistor logic) to send either 13v or 0v to the motronic ECU. I still don't know what is sent if the temp is within spec. I don't know when the AD595 integrated circuit chip was invented, but this chip does a lot and can be used for recreate this black box.

http://www.simplecircuitboards.com/Thermocouples.html

check this out, it's about 5 items down on he page

"EGT Version: $35.00

This board was designed for car enthusiasts who wish to monitor the temperature of their exhaust gas in order to fine tune their engine’s performance. The design is based on the Analog Devices AD595 (type K) Thermocouple Amplifier and has additional circuitry to enable its use in automotive applications.

Maximum output is 5V DC at 1000 degrees C (1832 F). This board is intended to be used with a DAC device to handle temperature conversion. Requires 12 to 24VDC power. Thermocouple is not included. Two, 3 and 4-channel versions of this board are available. Add $25.00 per additional channel. Please order the 2, 3, and 4-channel boards by emailing me with your request."

 

what do you mean splice the old into the new... don't mess up your new cat ECU.

the box is really not very sophisticated (the motronic ECU is the real brain). I think the motronic device accepts a signal state from the cat ECU box (that's all) and then knows how to react to it. if the cat ECU sends 13v to the motronic 2.7 it then shuts the bank down. this is what the service manual says.

so we hook up an amp to the thermocouple and then figure out how to intepret the reading from the amp to switch on 13v or 0v... still not sure what happens when the tempo is within spec.

Ernie - if you disconnect the 6-pin ECU plug (so no signal goes to the motronic) does the car react at all, any dash lights? I assume it kicks out an error code.

 

the schematics are very hard to follow and actually look different in the two places the cat ecu is show. here is what I have deduced so far

A - engine power ground
B - goes the slow-down light bulb
C - goes to fuse 6 in the passenger footwell (I think this is power in)
D - power out (goes to pin 52 on the ECU) 13vdc over 980 degrees
E - I think it goes to ground 150a/b
F - seems to go to check engine indicator 213a and something else

what kind of voltage is coming to pin C. test A, E to ground. in my experience the thermocouple did not fail. they are pretty reliable and I think if the thermocouple was the issue its probably the connector which is the cause. so what goes wrong in these little boxes (again I don't think its moisture)...

 

I just had a thought... the output that cuts the engine is seperate from the output that turns on the slow-down light. If you have a faulty cat ECU I think you could probably cut the wire coming off the ECU that goes to the motronic device, but leave the slow-down light connected. this way your engine will not cut out on you, but you will still be able to see if the slow-down light comes on. If the light comes on and your are suspicious about the cat overheating, you could pull over and see if the cats are glowing red. most likely they are not...

any thoughts??? I guess this will give you ECU error codes, but not the ones that will turn your check engine light on.

I'm also thinking about a way to test the thermocouple. we could probably do this at the thermocouple plug, just let the car get hot and then use a digital multimeter (Fluke 87 is a great instrument for $200) and see that you are getting the a millivolts output that is in range with a k type thermocouple.

Check this out.

http://designtools.analog.com/Thermocouple/Main.aspx#Top

Change the type to K (used in automobiles exhausts) and set the temp to 600 (?). I'm not sure what temp the cat should be at if the car is up to temperature and idling, if anyone knows, please tell us. not sure what the +vs or -vs is. seems like changing the ambient temp does not change the millivolts output expected from the thermocouple.

 

That's some good info.

 

I am working with the Cat ECU circuit to confirm if we could just cut the 13v wire that goes out to the ECU... seems to me this unit is packed in the rubber casing for two reasons, one to minimize the affect of vibration (which is what I thnk ends up killing these units) and second to deal with the engine bay heat. many of the components inside are rated to operate up to 85 deg cel.

 

If you swap the ECU from side to side and see the error move with the box, I think we can all safely assume it is the box that is malfunctioning and not the cat. Here is more detail about the wiring coming into the box

Black - ground
Red - power into the box (this essentially powers up the box)
Yellow - this goes out to the dash panel slow-down light
Pink - ground (for electronic devices)
Orange - 13vdc
Purple - out to Motronic 2.7 ECU pin 52

at rest and under normal operating temperatures the Purple wire is connected to the Pink wire thus sending 0v to the Motronic ECU. When the cat ECU detects an overheat condition (real or fake) it energize a small relay which connects the Purple wire to the Orange wire, thus sending 13vdc to the Motronic ECU and shuts down the bank.

So the idea would be to just connect the Purple to the Pink directly outside the cat ECU. this will keep 0vdc going to the cat at all times. The slow-down light should operate as normal. Hard to say if you would even get an error code on the ECU, this will depend on how the system is checked on start-up. If it tries to pulse the relay to see if 13vdc goes to the Motronic then yes you will have an error code. The engine should no longer shut down on you! I don't have a bad cat ECU anymore as mine was replaced and my bad one was completely dismantled...

 

Awesome!

That is some BIG TIME detective work you've done.

 

thanks Ernie, you are acutally my inspiration and your cluth removal post was truly the best.

If anyone has a box that is giving false readings please shoot me a PM. I would like to test this out... the modification can be done with the cat ECU removed from the car.

I suggest using what is known as a western union splice (a.k.a. lineman splice) its very strong and reliable. solder the joint and use heat shrink tubing to insulate.

http://www.claytonengineering.com/Training/myweb6/MElect/FM%2055-509-1%20Chptr%2012%20Electrical%20Conductors_files/fig12-15.gif