Continued: adjusting idle speed to compensate for lean engine condition??

[potatobroxd]

I've popped back in the dealership that help installed the exhaust for me for my Vulcan 650. He told me that he purposefully lowered the idle speed so the bike would run smoother (and richer?) after I complained that the exhaust made the bike run lean and very jittery (not smooth) and that the engine braking was WAYY too powerful.

So the result of lowering of the idle speed was: lower idle speed! and MUCH smoother throttle control and less engine braking, the bike feels so much better to ride

HOWEVER, the engine was not remapped and ecu was not flashed after exhaust installation, so would LOWERING the idle speed be an ALTERNATIVE to these processes? I've never heard of this method and is afraid that low idle speed may cause engine damage.

For reference:

Warm idle speed now: 1000

Warm recommended owners manual idle speed: 1250-1350

QUESTION: Why does this engine idle adjustment make the bike run smoother? Will it damage the engine? Thanks!

Edited June 17, 2019 by potatobroxd

[Mississippi Bullfrog]

Everyone I know has their own take on this. Some guys fit alternative exhausts and remap, some don't. Some fit power adapters that fool the ECU into thinking the engine is running cool so the mix is richer. Other's just run on original manufacturer's spec. So much depends on the bike and original settings so it's probably worth checking on an owners' forum for previous experience.

If it's running lean I'd be wary in the long run, just depends on the characteristics of the new system.

[megawatt]

It's dangerous to run an engine lean for long periods. Get it on a Dyno to establish air fuel ratios at different revs and get it remapped to suit.

[Mr Fro]

Lowering the idle speed will do knack all to the air fuel ratio on any part of the rev range. All it will do is potentially provide slightly more engine braking.

You can have the engine remapped - you may need a new ECU for this... Before you do anything, have a look and see if your bike has a lambda/oxygen sensor. If it has then the fuelling should take care of itself i.e. run within safe parameters. This also may be why you noticed a difference in performance directly after fitting - the ECU was learning.

[potatobroxd]

Lowering the idle speed will do knack all to the air fuel ratio on any part of the rev range. All it will do is potentially provide slightly more engine braking.

You can have the engine remapped - you may need a new ECU for this... Before you do anything, have a look and see if your bike has a lambda/oxygen sensor. If it has then the fuelling should take care of itself i.e. run within safe parameters. This also may be why you noticed a difference in performance directly after fitting - the ECU was learning.

 

By 'fitting' are you referring to the exhaust or the power commander? If it is the former then do you mean that the ecu will adapt to the new air-fuel ratio from the new exhaust given that the bike is equipped with a oxygen sensor?

Throughly appreciate the response!