Dos Secondary Air Injection System Can Help to pass Euro 4 level with under body cat? 1

[SoCal2024]

Hi every body. It is an old vehicle matches Euro 2 standard requirements with under-body Catalyst. We added a close cuple Catalyst to improve it to Euro 4, but back pressure raised so as the output power is not satisfactory. I need to know if anybody has the experience to use secondary air injection system? And may it can help to shorten warm up phase to reach light off temperature?
Thanks

Amir

 

[BrianPetersen]

Maybe. Only thing I can tell you is that most motorcycle engines nowadays have a secondary air injection system and a catalyst that is after the header pipes, and the air injection point is inside the cylinder heads as close to the exhaust valves as possible. The valve that activates the system nowadays is controlled by the ECU. If the engine has closed-loop control (which it had better, if you want any hope of reaching that emissions level) the air injection has to shut down the moment the engine is capable of running at stoichiometric air/fuel ratio, otherwise the "unmetered air" will cause the engine to run rich.

Whether it will help in your situation, is anybody's guess. If the issue that you are having is warm-up emissions and it's OK once warmed up, a catalyst heat-up strategy may help. There is an order of magnitude in the allowable emission levels between Euro 2 and Euro 4. If you are missing it by just a little bit, it may help. If you are nowhere close, it may still help but not by enough to get to where you need to go.

Don't forget other catalyst warm-up strategies; Raise the idle speed during warm-up sufficiently to allow the engine itself to run at stoichiometric without secondary air and retard the ignition timing to raise exhaust temperature. All such strategies should end as soon as (A) the engine will take it and (B) the catalyst is working.

The tricks the hot-rodders use to keep heat out of the engine compartment also serve to keep heat in the exhaust system. Low-mass exhaust headers (so that they don't act like a big heat sink) with ceramic coating (to keep heat in).