interest in slow down light / cat ECU substitute?

Love it. Same thing we did with the NLA oil pressure sender. Nicely done.

 

I have an '83 GTS QV so have two cats and two slow-down units.

One of my thermocouples is broken at the cat, I have a replacement which I bought used for $60, but its all waiting for the day I feel like ripping up my interior to thread the new thermocouple cable from the cat to the passenger footwell. It may be that the module is shot too as I have never tested it.

If you are redesigning these things, I wonder if it makes sense to subsitute new themocouples (with short wires) and relocate the modules to the the trunk ingnition module area. That way plain and simple wires could be run up to the instrument cluster and any future failures would only need futzing around in the back of the car.

As for the urgency, well, I have a fuel injectied car, so getting a major fuel dump into the cats is much less likely and will be associated with major misfiring, so I'm not sure I'd be in for $225 solutions. Then again, I'll think differently if my car burns to the ground.

 

... alright, alright, I am pretty compulsive about having everything working on my cars so, if my module is shot, I would probably spring for the $225 to get a new one.

How do you test the system to see if it is working in the first place?

 

Wow (more 'lectricity genius). I was thinking about just taking a propane torch to the thermocouple to see what happened.

The dimensions of the 1983 308 boxes are 4 3/8" x 2 1/4" x 3/4". Probably this is the same for all years. They look like old solid blocks of white plastic.

It is interesting that the 328 boxes are in the trunk. Much smarter than the way they did it in the 308. Do thermocouples die or last forever? (... What WOULD happen if I heated the thermocouple with a propane torch??)

 

Put me on the list for one! Been thinking about buying a factory version for my '89 328, as my light will come on every once in while. I have checked the system, and the box is most likely going bad…… So please put me on the list…..

 

I'd be interested. I removed the cat/installed a straight pipe on my 89 328 a few years ago because the slow down warning "computer" quit functioning. I would rather have a cat installed but not without the slow down light working properly.

If your unit will work exactly as the OEM does (did) for my 328, let me know. I'll be happy to buy the first one in "production." Or maybe the second one after Bob.

 

This is a true question, because I honestly don't know: Isn't the Slow Down Light system a carryover from the carburetor days and obsolete for fuel injected cars? With fuel injection, what fuel management / ignition malfunction would cause the catalytic converters to overheat? I had never seen "Slow Down" lights before in a car until I bought my 308.

 

Anything that would affect the firing of one or more cylinders - bad plug wire, bad spark plug, faulty ignition on an entire bank, etc - will result in dumping unburned fuel into the cat which can then cause it to quickly overheat/ possibly cause a fire. The ignition computer on the car does not detect such things/make any related adjustments, nor does the mechanical fuel injection system.

The 3x8's 180 degree crankshaft results in misfires being much less apparent than on a 360 crank. So, what would be an obvious misfire on, say, a Chevy v8, isn't apparent at all on the 3x8 engine. So the only warning you have on a 3x8 that is misfiring/Cat overheating as you are in cruise, running down the road, is that slow-down light.

Without a Cat, it is meaningless whether fuel is being dumped into the exhaust - as far as fire danger is concerned. So if you don't want the cat and install bypass pipe, there is no need for the slo down system to work as far as car operation is concerned.

 

I would be interested even though at present mine is functioning fine ( I know this because I got the firing order wrong when I put in new plug wires) just in case. $ 225 would be a drop in the bucket if this one goes TU in 3 or 10 years.

 

I would be in for one at $225 for my 87 328

 

hmmm, I do look for "self test" SD light flash at start up... I would assume a bulb failure first and then go check the ECU after... will your new box do the startup light flash?

 

I agree, it should duplicate exactly what the oem unit does as far as the dash light is concerned. Other capabilities at the unit itself are fine, as long as the dash light illuminates during the self test, blinks at (I forgot what temp) and stays on at the higher temp (I forgot what temp THAT is as well).

 

I think a stutter flash or some other distinctive flash at startup or even during running for a failed thermocouple would be a good improvement... but i wouldnt be that upset if it was difficult to implement. Mine works , at least most of the time.. but then it comes on while i am driving and i need to break out the infrared thermometer and check the exhaust for overheat... its a hassle. it hasnt failed enough to pull the bulb so i am leaving it active...

I would rather have the system operational... so your new box would be a great way to do that.

Thanks for thinking of us.

 

Bravo! I would be interested just in the preservation factor. My good one is in a box on the shelf.

 

If you build it, I'll buy it!

 

There is also Lamborghini Diablo's that uses same "ecu" there are market for those...

 

Let me know when you want my $225 and how you would like it sent!

I'll be happy to be able to remove the straight pipe and put the cat back!

 

I spend a little time today troubleshooting my “Slow Down” system on my 1983 308 GTS QV.

After some monkeying around, both modules now show normal function on the start-up check by lighting their respective slow-down lights for a few seconds after I turn on the ignition switch.

I tried to simulate a cat-overheat situation by connecting my spare (used) thermocouple to a module and heating it with a propane torch. I could not get either module to cause the slow-down light to blink or light despite heating the thermocouple to the point where it was just starting to glow slightly orange. (I got nervous heating the thermocouple beyond that point.) Did I just not heat it enough?

I also connected the thermocouple directly to my multi-meter and heated the thermocouple. Voltage rose to where the thermocouple was generating about 29m volts at the point where it began to glow. Is this sufficient voltage to trigger the slow-down light?

Anything suspicious here?