Test pipe/Cat delete 348

I assume that you mean the threading is a fine metric M8x1 (versus standard M8x1.25)? Try McMaster-Carr. You may have to buy a box of 10 or 25, but still the relative cost is inexpensive.

 

I recall on early (other) cars the cat thermocouple systems were early warning and/or overtemp indicators. Unless their ECUs tie in and communicate with the fuel systems I can't think of their need if the cats are removed.

But without the schematics in front of me I'm interested to know...

 

For whatever it's worth, the threads on my converters and test pipes are 5/16 fine thread (24, I think), not 8mm.

Wade, I'm not sure if the TC circuit talks to the ECU in order to cut fuel but even if it does it's not required if no converters are present to overheat. The only downside I see is that the TCs in conjunction with converters provide early warning of a rich condition that might cause engine damage in the long term, but without converters present there wouldn't be enough heat generated for the TC circuit to "trip" anyway.

 

Just what I was thinking, yes. But I haven't delved into removing the cat ECUs as well.

 

Seems like I've seen posts claiming that there is no issue with removing them on a 348. It's on my to-do list but haven't gotten there yet.

 

You have to go to a bolt supply shop. Take the test pipe with you and have them find an acorn nut that will fit.

 

I have threaded the inside and put an M5 screw in it
You will get an SDL or
You can replace the TK with a 20Ohm resistor

 

It should be the opposite, high exhaust gas temperature (EGT) means too lean condition which can be detrimental to the engine, especially the pistons (burnt/melted), and the converters (if present). My 348 2.7 is a non-cat version but it still has the TC-s to give warning of engine running lean. I would keep the EGT system.

 

The Motronic will only store a silent code but it will not illuminate the slow down light if the thermocouple signal is not present.

 

What Causes an Overheated Catalytic Converter?

 

My 348GTB does
Maybe different between US vs Euro cars

 

Thanks for the info Mike. I have never had a car with a cat-converter so did not have to learn about what can overheat it (I thought only very high EGT, when running lean, does it).

 

That is the first time I have heard of that on a 348. My guess is because the GTB/S run was one of the last of the 348s and probably a program "update" for the later Motronic 2.7s. My car is a 1990 and it does not illuminate the SDL nor the CEL. It does store a code, but no light. There is always the other option, just take out the SDL bulbs if the car does not have cats.

Anyhow thanks for the info, I learned something new.

 

Yr welcome
I have bought a 348TS 1991 so that must be M2.5
Will arrive at my place in 2 weeks
I will check SDL by unplugging the TK

 

Late '90 and up 2.7, '89 cars had the 2.5. The easy tell is, if there are two throttle position sensor = 2.7, if there is only one tps = 2.5.

 

Thanks for the update, glad to hear it's running fine.

 

Cool deal. Did you notice an increase in throttle response and overall power? What muffler you you have, BTW?

What did you wind up doing about the thermocouples and exhaust ECUs?

Been meaning to come back to this thread and update my earlier reply where I said that you should be able to remove the thermocouple ECUs and not get CELs, which I could almost swear I read here at some point in the past. I started getting an intermittent 1-4 CEL, which eventually turned solid. The code (4121 IIRC) turned out to be for the exhaust ECU, so apparently removing the exhaust ECUs will result in CELs, at least on the later cars. Still need to confirm that 100% by unplugging an ECU with no CELs showing. I did run the car with that side ECU disconnected and still had a light, but it later dawned on me that I hadn't cleared the old codes. FWIW, my car is a '91 2.7 (obviously), but it has been updated to what I believe are the very latest Motronics ECUs, as well as the latest chips. No idea if that matters with regard to exhaust ECU CELs though.

BTW, not 100% confident yet, but I think I resolved the problem by leaving DeOxit contact cleaner on all of the contacts for several days, then spray cleaning them with CRC contact cleaner, and then applying DeOxit Gold to the contacts. Ran the car for quite a few miles yesterday and no CEL so far.

Congrats on getting your test pipes installed. Now curious if you're getting CELs if you removed your thermocouples and ECUs.

 

Thanks for the followup, hercfe. Need to double check to make 100% certain, but at this point it looks like my car will show CELs if the exhaust ECU is disconnected. Interesting trying to figure out the minor variations on these cars.

 

I would like to buy 200Cel hi flow cats.

Can I delete the thermocouples and ecu's as well? Eu 1992 348 tb car.

Any pics or a DIY available?

 

If you have converters of any type you should retain the warning system. It's there for a reason.

 

Don't understand why
They are not that expensive