4 replies to this topic

[coyttl]

So a friend and I got into this over a brew yesterday, and I figured I'd seen what everyone here thought.

The basic question:
On an SPI or MPI Mini, can you remove all or most of the smog control stuff easily?

We got into the discussion, and soon had to assume that it didn't matter if it was legal or not - so ignore the fact that you won't pass MOT or whatnot - we're talking mechanically.

My argument was that you could - with little effect on the engine.
He swore that if you did, it would affect engine (idling and such) alot more, and the ecu wouldn't like having the purge valve undone, etc.

Thoughts?

[Edit: No, I'm not actually saying this should be done. Again, it was just an intellectual discussion on the workings of the smog system in the SPI/MPI minis.]

[xrocketengineer]

Hi,
As far as i can tell, there are three things that you can remove and the last one is iffy:
1. You can remove the Thermac valve and associated flapper and exhaust stove that provides hot air into the intake snorkel of the air cleaner. This is standard procedure when you us the K&N cone filter. This might affect start up and drive-ability in cold weather.
2. You can remove the catalytic converter.
3. You could disconnect the Lambda sensor and the mixture would be adjusted by the ECU using the MAP sensor, coolant sensor, air temp sensor, etc. I have done that on a Hyundai and it flags an error code and the check engine light comes on but the car ran fine. Obviously, on the Mini, the error code has to be read with diagnostics like the SP ACR. I do not know if you could run the car indefinitely with no Lambda sensor. However, based on what I have read in the SP ACR manual, it appears that some early SPI engines where "open loop" meaning there was no sensor.

I am not sure of the results of disconnecting the "crankcase emissions control system" or the "evaporative emission control system" would be worthwhile. Maybe somebody else can comment on that.

Ivan

[coyttl]

Apologies, revisiting an old thread of mine..

We (my friend and I having the conversation) were both aware of the Cat and the Air Thermac valve - we were more debating over the crankcase / evaporative systems.

For the purge valve, you could remove it and the charcoal canister, and block off the associated port on the intake. The ECU wouldn't care - rather, it wouldn't know the purge valve wasn't connected up, and there's no harm to fumes there, they'll just continue to get re-ignited in the engine. However, the other ones, I'm iffy about, he says that in theory you could disconnect them and drive away.

--Mike.

[Dan]

we were more debating over the crankcase / evaporative systems.

Neither are related to smog! The smog controls would essentially be the cat and closed loop system, the cat you could remove but the lambda has to stay really. Without it the engine is in limp mode I believe. In return for all that work, you'll get maybe 1 or 2 extra horsepower right at the top of the range.

The evaporative loss system could be dispensed with, the ECU would not care if the valve actually opened when signalled to as the Lambda would automatically correct for it.

The PCV system again could be removed, the lambda would correct for it (close the connection anyway). The PCV system does much good for the engine though, it keeps the crankcase clean and the oil fresh and doesn't reduce power in any way that you'll notice.

[coyttl]

we were more debating over the crankcase / evaporative systems.

Neither are related to smog! The smog controls would essentially be the cat and closed loop system, the cat you could remove but the lambda has to stay really. Without it the engine is in limp mode I believe. In return for all that work, you'll get maybe 1 or 2 extra horsepower right at the top of the range.

The evaporative loss system could be dispensed with, the ECU would not care if the valve actually opened when signalled to as the Lambda would automatically correct for it.

The PCV system again could be removed, the lambda would correct for it (close the connection anyway). The PCV system does much good for the engine though, it keeps the crankcase clean and the oil fresh and doesn't reduce power in any way that you'll notice.

Good point - this is my bad as well. Here in the US, anything related to those hoses, recirculation, PCV, etc are all 'generally' lumped under 'smog' or 'emissions'.

Thanks for the notes - good to know I was wrong then. I owe him a pint.