I read some info somewhere but cant seem to find it now. Does swapping out to a KDX Snorkel improve the performance or fuel mixture on an EFI bike.
Does it make it richer, leaner, or does the EFI adjust?
And in the future if I just install a Yoshimura Slip on will that effect the mixture. Or will the EFI compensate for both.
I do not intend to get a tuner at this stage. Marginal HP increase is ok. Currently the engine sounds overly muffled and a little unhealthy.
And the Yoshi or some other brands look like quality add on pieces.

 

I run both a free flowing KDX snorkel...



....as well as a free flowing exhaust...


...and the stock ECU compensates just fine with normal air/fuel ratio symptoms (grey spark plug insulator, black sooty muffler, and NO popping).

 

That is awesome. Thank you for the feedback !

 

You're welcome.

Just to add... most normal riding is closed loop. This means the O2 sensor is regulating the air/fuel ratio.

Full throttle is open loop where the air/fuel ratio is preprogrammed by the ECU and not the O2 sensor..
So full throttle will likely be lean with intake'exhaust mods,
and regular riding will be fine with the O2 sensor controlling the a/f mix.

I ride regular all the time so I don't have any lean mixture issues.
If I do happen to open up the throttle once in a while, even though the mixture is lean, it's not long enough to matter.

 

I think I read with one of Klxster explanations/debate (still trying to find that discussion tread), forgot the topic that by allowing more air into the airbox it creates a richer mix. Is that correct. Am I making a correct recollection of that thread?

If so wouldn't that compensate for a lean mix when using a more open slip on like a Yoshimura. even when in the open loop with a wider throttle openings ?
I am wondering how often we use more than half throttle if one is not racing. To create a dangerous lean condition assuming these changes were made.

 

I'm no authority on EFI, but do know a bit about fluid flow. Gasses and liquids are fluids and have some common traits. Everything depends on flow through the intake through the head and out the exhaust. Restrictions at either end will affect a variety of things.

The stock snorkel is about 1/2 the cross section of the KDX snorkel. The KDX snorkel is the same cross sectional area size as the air boot between the air box and manifold. So odds are it is flowing enough air for the size of the EFI injector body. Now all depends on the ability for the ECU to compensate for full flow, but I doubt it would run richer, it should make adjustments for the flow or hit the limit on how much fuel it can add per volume of air at the given rpm. I know that carburetors definitely will lean out if there was any restriction in air flow, the freer flow will allow more air volume and fuel intake.

When it comes to fluid flow (fuel mix is fluid) the thing that makes sense is the air box should flow fine at the lower throttle levels based on cross sectional area needed at a given throttle opening. The smaller OEM snorkel will eventually choke off the air flow as rpm rise and engine intake need is greater, the larger KDX snorkel should allow significantly more flow at double the size. The engine will only take what it needs. It also seems somewhat logical that the snorkel, being the same size as the air boot between the air box and throttle body, should likely allow as much air as needed. The KDX snorkel will allow open flow, it will emphasize leanness if there is any.

 

Double the cross sectional area makes perfect sense as the KDX snorkel is for a 2 stroke engine. Two combustion cycles occur for every single one. The 2 cycle exhaust note is high pitched because everything is happening twice as fast.

 

I will be going down the snorkel and pipe mod next. I have a feeling the factory open loop setting is probably a tad rich stock from the factory for engine safety reasons. So the once in a while wide open throttle is probably less of a problem. I guess if you need a lot of speed on the freeway and for a long time you may run into open loop issues?

 

I don't know for sure. The KLX300 has TPS (throttle position sensor). With SM road gearing (37T rear sprocket) the engine turns 6,000 rpm @ 60 mph. So once I'm up to speed, the throttle isn't open all that much. I wouldn't be suprized if it was still running closed loop.