Interesting observation when decelerating.

Higgs Boson said:

air injection which is commonly referred to as PAIR on motorcycles. injects clean air into exhaust to help burn off additional emissions. skews AFR readings so some people delete the system before getting on the dyno.

Click to expand...

Ahh, I gotcha. On my Triumph it's known as SAI (Secondary Air Injection). Where exactly is it located on the bike, and how difficult is it to remove? It's not the same as the gas fume canister injection system is it? I already removed that and blocked it off.

I love the pop. Especially with full throttle changes at low rpms when it's real loud

mdracer76 said:

Correct, I realize this. What I am curious about is if other owners experience the same 'popping' on deceleration while attempting to upshift with DQS enabled.

Click to expand...

I have not had this one, my bike is track ready only. Do not think I've decelerated while trying to up shift with DQS on. Generally I'm accelerating on up shifts with DQS.

MacaveliMC said:

Ahh, I gotcha. On my Triumph it's known as SAI (Secondary Air Injection). Where exactly is it located on the bike, and how difficult is it to remove? It's not the same as the gas fume canister injection system is it? I already removed that and blocked it off.

Click to expand...

Theres a little pump between the airbox and the heads. You just remove it all and put on the block off plates and plug the airbox.... you need software like Tuneboy to turn off the error light or maybe the dealer can do it.

weltonrk said:

I have not had this one, my bike is track ready only. Do not think I've decelerated while trying to up shift with DQS on. Generally I'm accelerating on up shifts with DQS.

Click to expand...

Agreed. my career is testing things.... guess I just try weird .....

Bump to see if anyone else was able to replicate the same thing over the weekend...

Higgs Boson said:

Theres a little pump between the airbox and the heads. You just remove it all and put on the block off plates and plug the airbox.... you need software like Tuneboy to turn off the error light or maybe the dealer can do it.

Click to expand...

You don't need to do this (not throwing any codes). Leave the connector and sensor in place, cap it there...

mdracer76 said:

Bump to see if anyone else was able to replicate the same thing over the weekend...

Click to expand...

Haha, I thought about this thread when I was riding yesterday and just for grins tried upshifting as the bike was decelerating without using the clutch as you describe, with DQS on (I don't turn mine off). Like you originally described, the bike would not shift into a higher gear but every time I stabbed at the lever (I have reverse shift), I got a "pop". I did it a few times and it was very consistent.

It's not anything I would normally do but I was able to replicate the effect you described. I do believe it is due to what has been discussed. The shift rod DQS sensor detects upshift movement of the lever and cuts the ignition momentarily. The bit of fuel left unburned by the cut in spark hits the hot headers and explodes inside the exhaust system, creating the pop or boom depending upon how much fuel is unburned. This can be a bit bad on your exhaust packing, but I love the sound of it so much I won't mind having to repack the exhaust a bit earlier than normal.

TransNone13 said:

You don't need to do this (not throwing any codes). Leave the connector and sensor in place, cap it there...

Click to expand...

true, good point.

Higgs Boson said:

-1

The DQS does not cut fuel and cause a lean spot. Like JeffD said, it cuts ignition and leaves unburnt fuel to pop in the hot exhaust pipes, not a backfire. A backfire is when combustion takes place in the intake manifold, common with carburated engines. I haven't seen or heard a backfire since the 1980's.

This is where your exhaust flames come from, combustion in the header. A backfire would set your air filter on fire, lol.

This is totally normal and the same thing will even happen on the rev limiter, or if you use a two-step or any other spark retarding rev limiter.

The reason you want to stay on the gas is because when it is done limiting, in this case when the shift is complete, you want fuel ready to go so the shift is smooth, otherwise it will clunk as you roll back on the throttle.

Click to expand...

Winner winner chicken dinner.

Question.... WTF would you upshift while decelerating? Are you just playing around with the bike.

CrazyDuc said:

Question.... WTF would you upshift while decelerating? Are you just playing around with the bike.

Click to expand...

Lol I thought they meant up shifting. Why would you for that lol.

CrazyDuc said:

Question.... WTF would you upshift while decelerating? Are you just playing around with the bike.

Click to expand...

Happens all the time on the street.

For example you are riding aggressively as you should not be but are anyways because you can and you reach a point in the road where it is time to slow down for example coming up to a slower speed limit with for example a cop sitting a few hundred yards past it and you need to hit the brakes to for example slow down and upshift to get the bike to shut up but still make it look like you are for example going along normally so no suspicions are raised.

I can think of more.

Higgs Boson said:

Happens all the time on the street.

For example you are riding aggressively as you should not be but are anyways because you can and you reach a point in the road where it is time to slow down for example coming up to a slower speed limit with for example a cop sitting a few hundred yards past it and you need to hit the brakes to for example slow down and upshift to get the bike to shut up but still make it look like you are for example going along normally so no suspicions are raised.

I can think of more.

Click to expand...

Ok ok I can see that happening... I'm going to try this today and see if I spit fire, sounds pretty cool to tell the truth