Intake air path

[Black Sled]

Does anyone understand the path air travels on it's way to the airbox snorkel?  I once thought it came in the front, above or through the radiator.  But now I see there is a black plastic blocking plate across the front opening between engine and airbox.  So now I'm thinking the air must come up around the carbs and/or around back under the tank.

I have read that a Dyno run will indicate a rich condition at high RPM's because it does not replicate the "ram air" effect of highway driving.  I'm not sure I buy that now, after seeing the blocking plate there, and the fact that the airbox snorkel opening is pointed backwards.

Any thoughts?

[Ricky-D]

I think you're correct amigo!

***

[98valk]

Does anyone understand the path air travels on it's way to the airbox snorkel?  I once thought it came in the front, above or through the radiator.  But now I see there is a black plastic blocking plate across the front opening between engine and airbox.  So now I'm thinking the air must come up around the carbs and/or around back under the tank.
I have read that a Dyno run will indicate a rich condition at high RPM's because it does not replicate the "ram air" effect of highway driving.  I'm not sure I buy that now, after seeing the blocking plate there, and the fact that the airbox snorkel opening is pointed backwards.Any thoughts?

air flows from the front to the rear over the top of the airbox cover.  At speed the air flowing this way will actually create a low pressure area at the airbox opening restricting how much air can be drawn into the airbox IMO.  This is why I blocked off the rear opening and opened up the front of the airbox cover. this requires new main jets and tunning for the exhaust being used.

[sandy]

BigBF sells a spacer to raise up the front of the tank. This extra space allows more air to flow under the tank to the original air intake. I've run this way for several years and it doesn't run out of air at high speeds.

[John U.]

I did the same thing to my bikes. I found that the rubber bushings used for the upper  front shock absorber mounts for a Chevy pickup work very well when sanded flat on both sides. Cheap too if you already have them laying around.

[old grouch]

How do I find out where to get the BigBF spacer?  Thanks, Stan

[sandy]

www.bigbf.com 

[98valk]

I've run this way for several years and it doesn't run out of air at high speeds.

didn't say it will run out of air. It will not allow the engine to take in as much air as it could. Opening up the airbox lid as I describe required the use of a bigger main jet. It would not run past half throttle with the stock 100mj.

http://www.knfilters.com/filter_facts.htm    go down to the racing section and see the pic of how the inducted volume of air is reduced. This is how the stock airbox is set up. The oem airbox design is also partially for epa noise regs. This is all negated if the relationship of the tank to the airbox opening stops this airflow across the airbox opening.

[woefman]

HMM would that mean Baker Airwings have and adverse effect on this ?

Sounds Stupid I know .....But if your saying the Windshield Blocks Some , then that leaves ...

Air must come around the Bike to get into the Air Box.

If we have Baker Wings , this air could be swooshed around the Bike mostly.

Now I know many are in Love with their Baker Wings and would never admit this could happen.

However Interesting to think about it.

My Tank Is raised to Accept the Velocity Stacks.

[Black Sled]

doesn't the windshield/fairing block the front of the tank from forced incoming air flow?  Just trying to understand why a spacer would help at highway speed.  Is there any direct evidence (AFR or other) that the spacer allows more airflow into the box?  If so, I want one...

[Ricky-D]

I ride an I/S and it's easy to see how the fairing can impinge the air flow to the air box, although the total affect I think is negligible.

I think that Honda turned the intake to face rearward to avoid any charging effect that would affect the air/gas ratio.

I've read the posts about European Valkyries and their breather characteristics and also read posts about modifying the air boxes.

I think the air intake is located in the best possible location being decided by Honda experience to find the most quiet area of air. To help keep air intake as uniform as possible.  To me it is quite likely any alteration of the air box or air flow around the air box can cause unintended consequences to performance and reliability.

Is there a better configuration for the air box? Probably.

Without utilizing a dyno to document performance changes when altering the air box you must assume most comment are "seat of the pants" results and those you know, are totally subjective.

To the idea that there is such a large difference in change when modifying the air box as to need a change to the carburetor jetting I only add that there are some who go make changes to the jets regardless of any modification to the air box, and the common link I find is that all report success of whatever changes are made to the air box and/or the jets, but again, without dyno documentation, it to me is suspect and not necessarily something I would do based solely on a promise.

My conclusion is this.  Go ahead and make the changes you want.  Always retain the ability to get back to the starting line when the change just didn't work out the way you had hoped.  In the case of modifying the air box, I would strongly recommend having a spare box available so you can get back to where you first started.

By now you know that I am a Honda booster and consider that Honda has always gone the walk to produce the best and there is very little we as the consumer can do to improve upon the engineering and research that Honda has done.  I also accept the idea that due to constraints, Honda has had to make compromises at times, but I think when they have had to do such, it's always been in our interest which coincides with their interest in manufacturing the best motorcycle in the world.

***

[roboto65]

Well thinking in an all weather stance do you think injesting water in the engine is a good idea maybe thats what the engineers had in mind.
Now if you are just a fairweather rider then hey no problem!!
I had a Magna before this and the snorkel is the same rearward facing and to say it does not suck enough well I have found dragonflys on top of my airfilter  ??? ???

[Black Sled]

I agree totally - seems like a pretty well engineered system.  And I too have found bits of grass, etc, on top of my filter.

The reason I brought all of this up - I rejetted my bike some time ago to 105 mains.  I thought it ran really well, especially after installing the K&N with the Cobra pipes.  When I finally had the opportunity to Dyno it, I found it was running really rich above 4K.

Since I agree with the insights posted here, and don't believe there is much of a "ram air" effect, I am going to go back to smaller mains.  I haven't decided between 100's and 102's as I don't know how much benefit the K&N provides at WOT.  I am convinced it makes a big difference in the mid-range, but I rather think that the snorkel limits the maximum amount of air which can enter.  So I am kinda leaning toward going back to 100's.

Thanks for your thoughts on this.

[98valk]

I agree totally - seems like a pretty well engineered system.  And I too have found bits of grass, etc, on top of my filter.

The reason I brought all of this up - I rejetted my bike some time ago to 105 mains.  I thought it ran really well, especially after installing the K&N with the Cobra pipes.  When I finally had the opportunity to Dyno it, I found it was running really rich above 4K.

Thanks for your thoughts on this.

at what temp was your richness indicated at and what was the air/fuel ratio?  To maintain max power a mj change is required for every 25 degree temp change.

[98valk]

Well thinking in an all weather stance do you think injesting water in the engine is a good idea maybe thats what the engineers had in mind.
Now if you are just a fairweather rider then hey no problem!!
I had a Magna before this and the snorkel is the same rearward facing and to say it does not suck enough well I have found dragonflys on top of my airfilter  ??? ???

I have never had a problem with rain, and I have been in some heavy downpours.

[Black Sled]

at what temp was your richness indicated at and what was the air/fuel ratio?  To maintain max power a mj change is required for every 25 degree temp change.

---------------------------------------------

dyno was done at 79 degF and about 1,000 ft higher elevation than where I live.  AFR dropped down to around 10 and was pretty flat with a blip to 11 around 5200 RPM.  Even correcting for these effects I am too rich with the 105's.  I am agonizing over going to 102s or back to 100s, but am leaning toward the 100's for summer and mountain driving.  I don't anticipate alot of cold weather riding anytime soon. 

[Black Sled]

oh - another interesting point about the dyno results - I ran all the curves on the Dyna 3000.  Curve 7 gave the best HP and Torque - about 3.5 HP better than curve 2, which is supposed to be same as the stock curve.  I know for a fact the gas milage is 3 - 5 mpg better using 7 as well.  But of course premium fuel is required....

[98valk]

oh - another interesting point about the dyno results - I ran all the curves on the Dyna 3000.  Curve 7 gave the best HP and Torque - about 3.5 HP better than curve 2, which is supposed to be same as the stock curve.  I know for a fact the gas milage is 3 - 5 mpg better using 7 as well.  But of course premium fuel is required....

premium is not required. I run #7 plus 6 TW above 2500rpms and no problems. with the -10degrees w/the dyna switch same advance as stock I/S ICM +1 degree.
what airbox and exhasut mods do u have that justified larger mj? only allowing much more air in and not w/a K&n will u need a larger mj.
should have made max power on curve 8 "According to Hondatek's data the 1520 will actually lose 1 HP per degree over 26 total."   http://timskelton.com/valkyrie/tech/trigger_wheel_plus_dyna3000.htm

[Black Sled]

I didn't test curve 8.  In fact, I never have run curve 8.  I always figured it was for blown engines or some other extreme mod.   Will have to give it a go.  BTW, I don't have a trigger wheel - just the Dyna.