Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Dave W, How could you?

Dave W,
How could you sign off your page in Miscellany Just when we were about to find out how your new cat works and all the details?

My 4/4 Sport with the Sigma engine and Librands 4 branch exhaust headers with 200 cell Cat fails the MOT every year!
I'm waiting on your news before changing mine to a 300 cell Cat and finding out how you went about it?
The Librands header ends with a triple bolt flange which the Librands Triple flanged Cat bolts onto, ( that's a bit of a tongue twister), The only Cats I can find seem to have only 2 bolt flanges?

Come on Dave, get back and "finish what you started" That's a song isn't it lol

Also, I think I've read somewhere that a new Cat needs to be run for several miles before it becomes fully activated?
Does anyone know if that's true?
I'm sure I read that someone's car failed on a faulty Cat, bought a new one and went back to the MOT Station and it failed straight away as it hadn't become active yet?
What's the score with this?
Cheers

Admittedly an AI overview but it makes sense.

Yes, a new catalytic converter needs a proper break-in, often involving a specific driving cycle or heat-up/cool-down period, to seat the internal matting correctly and allow the car's OBD-II monitors to reset, which is crucial for passing emissions tests and ensuring it functions optimally to meet regulations. Failing to do the break-in can lead to reduced flow, premature failure, or issues setting the readiness monitors needed for inspection.

I think the end chapter will appear this month. Although the new cat was fine on Lambda, the mixture was way off. From memory now, the CO limit at fast revs over 2500rpm is 0.20. I got 0.5+. Way over, even after multiple tries. The only thing I had left was to reinstate the standard ECU parameters, so losing the AR upgrade.
The dealer did the deed. The CO dropped to 0.015 (would need to check, but way below).

The AR exhaust system brings a big improvement without the AR chip, so it's staying that way. Of course, the sooty tailpipe which I had from new is back. But it runs and revs fine.

I’m a bit confused with this. To me, a sooty exhaust signifies over-rich running and in turn, over-rich running causes higher CO emissions. So how does it now satisfy the MOT in this condition?
Also, I guess that by reverting back to the OEM ECU settings that fuel consumption will drop a bit…and what about that twitchy throttle response that was associated with the car when new?

None of this has made any sense Doug. The sooty black tailpipe was from new. The AR flash cleaned it up. But the MoT has always been really marginal.

The bad running a year last October lasted for about 30 minutes in a trip which lasted 1hr 30. It suggested bad fuel, or electrical, but cleared completely after getting home, apart from the return of the sooty black tailpipe.

Going to the MoT, which is 55 miles gave a clean tailpipe, but the emissions were off the scale.Remember also that when I first added the AR exhaust, I was surprised that the sensor ahead of the cat was clean, but after the cat was black soot. That was similar when I changed the cat and the sensors this time. Getting back from the MoT, another 55 miles I have the sooty black tailpipe.

The upgraded standard ECU flash, which dealers hold, was to address the sharp throttle response. Now it's not quite as relaxed as it was but nowhere near the almost undrivable state it was in from new.

It makes no sense that the AR flash was a huge MoT fail. In theory the settings can't change and yet it was hopeless, and left me with the only option, to got back to the original settings. I knew that the exhaust alone gives a much crisper response, and that the flash really only adds cleaner revving at the top end. Coming home on real roads, there was no real difference.

I can only conclude that the standard flash provides good emissions up to the 2,500/3,000rpm MOT limit, and maybe after that goes rich. For me it's not worth the bother of paying again to have the AR flash, when the likelyhood is that it will not pass the next MoT. It's classic Morgan. The same models perform differently. We've seen that on models which suffer from throttle hang.

Baffles me

AI came up with this answer to rich running GDI engine

It is not a normal characteristic for a properly functioning Ford GDI (Gasoline Direct Injection) engine to run excessively rich above 3000 rpm. The engine control unit (ECU) is designed to maintain an optimal air/fuel ratio for both performance and reliability, although a slightly richer mixture is often commanded by the ECU at high RPM and load to manage combustion chamber temperatures and prevent engine damage.
If a GDI engine runs too rich (beyond the normal operating parameters) at or above 3000 rpm, it indicates a problem that needs diagnosis and repair.
Potential Causes of a Rich Mixture at High RPM
A number of issues can cause an engine to run rich at higher RPMs, often due to the engine receiving too much fuel or insufficient air.
Faulty Oxygen (Lambda) Sensor: A malfunctioning O2 sensor can send incorrect data to the ECU, leading the computer to add excessive fuel. A flat-line reading on an O2 sensor graph at the top end (indicating a constant rich signal) is a strong symptom.
Leaking Fuel Injectors: Direct injection systems operate at very high fuel pressures. A leaking or clogged injector can deliver an incorrect amount of fuel to the cylinder, leading to a rich condition and potentially misfires.
Stuck Open Purge Valve or EGR Valve: A stuck-open evaporative emissions (EVAP) purge valve or Exhaust Gas Recirculation (EGR) valve can introduce unmetered fuel vapors or alter expected airflow, causing a rich mixture.
Contaminated or Faulty Mass Airflow (MAF) Sensor: A dirty MAF sensor underreports the amount of incoming air, causing the ECU to inject an incorrect amount of fuel relative to the actual air intake.
Faulty Engine Coolant Temperature (ECT) Sensor: If the ECU receives an incorrect signal indicating the engine is always cold, it will continuously enrich the fuel mixture as a "cold start" strategy, even when warm.
Fuel System Issues: Problems with fuel pressure regulation, such as a leaking fuel pressure regulator or a clogged fuel return line, can lead to excessively high fuel pressure in the system, forcing too much fuel into the engine.
Restricted Airflow: A significantly dirty or clogged air filter can restrict air intake, causing the air/fuel ratio to become rich.
Engine in "Limp Home" Mode: If a sensor detects a serious fault, the ECU may put the engine into "limp mode," which often limits RPM and can run a rich, protective map to prevent damage, but this should trigger a check engine light.

My 2011 4/4 has had a sooty exhaust from new. An ECU flash done at 3 years old improved performance but still has sooty exhaust. Unless I really warm the cat up prior to MOT it will fail on the Lambda. Reading shows a lean mixture. HC is usually around 8 with a limit of 200ppm.
Think if you note exhausts on nearly all modern vehicles using unleaded petrol they have a sooty exhaust exhibited (UK). How the Cats survive I have no idea.

After discussing the whole issue at the Dealers, we concluded that the bad running was the cat internals disintegrating and part blocking the exhaust. At that point it would start normally but not rev at all beyond 800rpm, except for a sporadic super rev, like it was clearing out. There was no engine light.

Everything checks out OK. The sensors are new and the relays are new. It starts well hot or cold, it revs well, it runs well, and I know what an over-mixture sounds and feels like and it does none of that. So I can only conclude that this is how it is.

In theory a 300 cell cat should rob "a couple" of BHP over a 200 cell cat, and the standard ECU set up the same, and yet it really doesn't feel any different on the road.
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