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Open up the Airbox


chris2992

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The best engineers Honda has to offer have worked on optimizing the air intake of the VFR since its conception and you guys just blew it all away in one simple swipe of a Dremel. :goofy:

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I do know that after installing the PCII and O2 elim. and getting a good map in it, I still had a very moderate flat spot around 4500-5500.  Opening up the airbox has eliminated it, and the tank-lift was done at the same time.  I don't know if there is more top-end power, but the mid-range is much improved.

Interesting, but not unexpected. I found when playing around with the PCII that I had to LEAN the mixture out a bit at 5k rpm to get it to run right. I was sure initially that it needed more fuel, but the more I added, the worse it ran. So, I had a look at a few maps and found they had some minus figures there. Thinking about it, I suspect Honda allows for the effect of opening the flapper valve, and dumps more fuel in, but it's not quite right. Certainly leaning it out took away some hesitation.

So, it's possible your mods actually helped the standard map to not be slightly rich.

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It was a very quick seat of pants dyno, I'd say it still will need some work. Give me a few weeks to put some miles on it, and I'll post my tweaks.

<_< Still no pictures of the lovely Spokesmodel......

Without pictures, she does not exist. :P

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I did a similar mod....opened the box up, started running a BMC filter....definitely louder...you CAN really feel it in your chest. However, i noticed alot of bogging down especially with top gear rollover, etc. Doesn't seem to make as much power and my MPG has gone to shit. I'm considering looking for a new lid on ebay and going back to stock...you guys have any idea what's going on? I feel like more air should ALWAYS = better, however I'm not really reaping the benefit...

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  • 1 month later...
  • Member Contributer

Well I finally got my bike back for keeps now and have logged about 200 miles on the new setup. Much better. I have some tweaks that need to be made around 4-6k at WOT, seems to bog down then right at 6k it just snaps back up. Just crusing around is much nicer too, throttle control is much easier and the power band is wider and smoother. The intake sounds just mean, almost too loud, but I have been riding with no earplugs to listen to it. Exhaust note has changed some too, guessing due to pair valve removal. Engine braking is smoother too. I am very happy now and if I can tweak the map a bit it will be perfect. Now where did I put that dyno.

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Guest Flailer
Well I finally got my bike back for keeps now and have logged about 200 miles on the new setup. Much better.

I have some tweaks that need to be made around 4-6k at WOT, seems to bog down then right at 6k it just snaps back up. .....snip ... I am very happy now and if I can tweak the map a bit it will be perfect. Now where did I put that dyno.

Did i read that KeithBob corrected this by lifting his tank 1/4 inch - increasing air-flow further?

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  • 1 month later...
  • Member Contributer

here is an airbox

I did a similar mod....opened the box up, started running a BMC filter....definitely louder...you CAN really feel it in your chest.  However, i noticed alot of bogging down especially with top gear rollover, etc.  Doesn't seem to make as much power and my MPG has gone to shit.  I'm considering looking for a new lid on ebay and going back to stock...you guys have any idea what's going on?  I feel like more air should ALWAYS = better, however I'm not really reaping the benefit...

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  • 3 weeks later...
Guest H65mech

chris i was checking out your gallery, i love the red reflecting on the wheels.

Safer at night too. Do share???

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  • 2 months later...
  • Member Contributer

I did something a little different. I removed the lid completely. Plugged the control valve for the flapper with a rubber cap. Fabricated a custom filter with a K&N for a GM V6. Bigger filter area than a BMC. More direct air flow to the intake funnels. I have no issues with hesitation or flat throttle responce. I had a custom map done at an authorized tuneing center ( PC II ). After the mod.

I need to take photos and add them to my gallery.

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