Flapper or PAIR? One of these is possibly causing issues.

So in a previous thread I mentioned how my used bike had a mouse in the airbox and it COMPLETELY clogged the stock filter. So I never knew the bike any other way.
With the clogged filter, the bike took off very nicely and no 5k flat spot. The engine did lug if I shifted into a lower gear too fast. The engine didn't have to "catch up" with the throttle though. What I twisted, I pretty much got out of the engine right away. I could kind of bark it in town and get that nice little torquey burst.

So I installed a new K&N and decided to do the PAIR, Flapper and Snorkel mod while I had the tank up.

So what changed?
1. There is a flat spot at 5k now.
2. The bike "catches up" with my throttle response at lower rpm. The engine bogs before it gets going. No more instant acceleration in quick bursts from ~3.5k-5k, like before. Maybe this is the snatchy feel people were talking about before they did the mods? I never had an issue with that at all though, it was never snatchy feeling in any way. Just acceleration when I wanted it.

Additionally:
The bike sounds much better, that snorkel mod does the trick. :smile-new:
The bike revs in VTEC much better as expected with the new air filter.

So, any ideas on what is going on? I'm wondering if the mouse filter created a different air/fuel mixture which somehow made it accelerate better at lower rpm? Or if the mods did something negative.


If you made it this far, Thanks!

 

Stock, the bike is very lean around 3-6k, okay above 7 and actually rich up top.
With a clogged filter the Air/fuel might have been okay down low, but pig rich up top.
With a KN and no snorkel/flapper/pair, I am sure its still about the same as stock, i.e. very lean around 5000 rpms.
Go ahead and install a Power Commander and o2 eliminators and I am sure it will be much better, just the same as the thousands of other VFR's out there.

 

Those mods typically help that flat spot, not create it.

 

true or it could just be a placebo due to the added noise

 

I love the placebo effect, sadly though there is a flat spot. Caused me to look down at the speedo a few times thinking "Am I out of gear or something?".

 

Exactly, and this is the whole point of this thread. I think I will enable the flapper and see what happens. The PAIR probably isn't the issue as that is only post combustion stuff going on.

 

Have you blocked off all the air hoses after the pair removal?
I'm not a great fan of the flapper mod, I don't think it achieves what people think it does.

 

There are actual dyno tests on here somewhere proving it does work.

You gained about 1 horsepower across the entire range. You lose a little on the low end and gain some on the mid-to-high Range

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OK, you've opened the flood gates...find said proof!

 

It's literally a chart showing -0.5-1.0 hp changes from a little over idle to redline. Nothing monumental lol

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here this is from veefer800canuck<br />
<br />
<br />
From: DynoWorks@aol.com [mailtoynoWorks@aol.com]<br />
Sent: Monday, 29 March 1999 5:20 PM<br />
To: vfr@cs.wisc.edu<br />
Subject: 800 snorkel dyno test (mostly data)<br />
<br />
<br />
Hello list ...<br />
<br />
Had the opportunity to do a back to back dyno test on the VFR800. We'll let<br />
the numbers tell the story.<br />
<br />
Dynojet Model 150 Chassis Dynamometer<br />
Eastside Harley Davidson, Bellevue, Washington<br />
DYNORUN #1, baseline, 4th gear roll-on - 3-27-99, 3:17PM<br />
DYNORUN #5, no snorkel, 4th gear roll-on - 3-27-99, 3:22PM<br />
<br />
DYNORUN #1 DYNORUN #5<br />
RPM SAE hp SAE hp<br />
3500 28.3 28.8<br />
4000 32.1 31.7<br />
4500 35.4 35.4<br />
5000 39.8 40.3<br />
5500 45.2 46.1<br />
6000 54.4 55.3<br />
6500 62.6 63.2<br />
7000 69.6 69.9<br />
7500 75.6 75.5<br />
8000 81.1 information not available<br />
8500 86.6 87.1<br />
9000 90.0 91.0<br />
9500 91.6 92.7<br />
10000 93.2 93.8<br />
10500 92.9 94.2<br />
11000 90.3 91.6<br />
11500 88.8 89.6<br />
<br />
Magnifying the resolution of the 500 rpms nearest the hp peak follows<br />
<br />
10000 93.2 93.8<br />
10100 93.4 94.1<br />
10200 93.5 94.3<br />
10300 93.6 94.6<br />
10400 93.3 94.6<br />
10500 92.9 94.2<br />
<br />
Magnifying the resolution of the 1000 rpm range nearest torque peak follows<br />
<br />
RPM SAE ft-lb SAE ft-lb<br />
8100 53.4 53.3<br />
8200 53.4 53.4<br />
8300 53.6 53.6<br />
8400 53.6 53.7<br />
8500 53.5 53.8<br />
8600 53.4 53.8<br />
8700 53.2 53.7<br />
8800 53.0 53.6<br />
8900 52.8 53.4<br />
9000 52.5 53.1<br />
<br />
Testing conditions: 29.66 in.Hg. absolute barometric pressure, Vapor<br />
pressure .44 in. hg., ambient air temperature 49.5 deg. F. Partly cloudy.<br />
All stock '98VFR800FI, 3,273 miles.<br />
<br />
Subjective comment: Noticeably louder intake noise. Doesn't sound like a<br />
sewing machine anymore. Changes the character of the engine. Feels raw,<br />
sharper edged. I will be leaving the snorkel out for now.<br />
<br />
Wayne Chan, WMRRA/OMRRA #326

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Yup. That's the thread.

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So I plugged in the Flapper back in and..... PROBLEM SOLVED. More oompmh at lower rpms and the bike takes off better. Slightly less sound. I don't know what to say but the bike is behaving properly now.

QUESTION: Isn't that data above for the Snorkel mod and NOT the flapper mod?

 

It was for both together if memory serves.

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He mentions the snorkel twice, no mention of flapper. The last thing that is said is. "I will be leaving the snorkel out for now."

I could see just the snorkel mod adding 1hp or so.

 

I'll have to dig it up again. There's more in that thread

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Funny. I have almost the same thing but I have done no mods. I had a mouse in the air box that chewed the air filter. I replaced the air filter with an OEM item. My 6th gen is box stock and it seems to have a slight hesitation, when under load. It's hard to enplane but it seems like it is hanging back a bit if you know what I mean. Also you cannot increase the revs incrementally from 3K to 5K (this is when the bike is not under load). It will just jump to 6K. I am sure this could be cured with a Power Commander.

 

And a throttle body synchronization will help in the 0-5% throttle area

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