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2015vfr

Loss of Power during VTEC transition

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Does anybody else experience a brief loss of power when transitioning to VTEC?

 

It does not happen all the time, and does not seem to be related to which gear or what speed, but when going past the VTEC threshold I seem to sometimes have a very brief reduction in power before picking up sharply as the RPMs rise.

 

It is very jarring when it happens, and does not inspire confidence while riding.

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That’s not right, mine feels like a 2 stroke hitting the pipe when the VTEC cuts in, no pause in acceleration 

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Agreed... No hesitation, just a sudden burst of power, though it can be a bit abrupt if it happens mid curve.

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I'll never understand why they put vtec in a motorcycle, it's just a wrong idea from the start.

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Thanks everybody, looks like it'll have to go into the shop. Any idea what could cause the hesitation?

 

EDIT: I'll check the oil level tonight to see if that is good, seems like it could cause the issue

Edited by 2015vfr

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4 hours ago, 2015vfr said:

 looks like it'll have to go into the shop.

good luck finding a shop capable of fixing something complicated.

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Is that straight from starting and riding off when engine is cold or mid run?

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1 hour ago, fink said:

Is that straight from starting and riding off when engine is cold or mid run?

Last time it happened I had been riding for over 10 minutes, in 5th gear accelerating on the freeway, at the transition, brief loss of power (bike jerks/hesitates for half a second) and then more power as the revs climb.

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Whacking the throttle open in a high gear at relatively lower speeds will do this.

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7 minutes ago, Egg on Leggs said:

Whacking the throttle open in a high gear at relatively lower speeds will do this.

Throttle is being applied, but this does not happen when the throttle is first applied, it happens exactly when the vtec transition occurs, and only when the vtec transition occurs, so I'm fairly certain that it is tied to that system somehow

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1 minute ago, 2015vfr said:

Throttle is being applied, but this does not happen when the throttle is first applied, it happens exactly when the vtec transition occurs, and only when the vtec transition occurs, so I'm fairly certain that it is tied to that system somehow

OK, let me put it another way, if there was a system fault it would happen all the time. I can make my bike do it at will by being in the wrong gear. 

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Bear in mind I am new to this form and I have a 2015 VFR800 I just purchased (with only 3450 miles) trading in a 2017 CBR500R. When I was doing all my research on the 2014-15 VFR800's, all the official reviews that had dynos all noted a slight drop in HP just as the VTEC kicked in and then took off. You could see it right in the charts. Also, I purchased a Delkevic 8" slip-on exhaust and the dyno chart they provided showed the exact same, slight drop in HP before rocketing upward. The chart graphs were similar in shape regardless if it was a slip-on or a full exhaust. So based on all the reviews I read on this bike, I am going to say this is how Honda solved the "explosive" kick in complaints of the extra valves from the previous generation to make the transition smoother.

 

I am by no means an authority on this - just my two cents.

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^^^^^. What he said. You can’t just go from two valve cross swirl to 4 valve without disrupting the induction pulses. Most Dyno charts show that dip in power at Vtec transition point.

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Yup, mine does this, and most noticeably the first time after starting (even if the engine is warm by then).

 

I'm pretty sure I read more than one review before I bought, that said the same thing.

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Overall the VTEC transition has been greatly improved on the 8gen when compared to the 6gen. Is there any chance you could test ride another 8gen as a comparison. Can honestly say I'm not experiencing what you've described on my own 8gen.

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I checked the oil and level is right between the lines.

 

The power loss is severe enough to jerk me forward when it happens, 

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4 hours ago, 2015vfr said:

I checked the oil and level is right between the lines.

 

The power loss is severe enough to jerk me forward when it happens, 

That is definitely not right 

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My friend Makota San previous job was Chief Engineer Honda R&D who
invented Honda's VTEC... he calls VTEC "his baby" and recalls his boss
being super skeptical of the idea working at all...

 

Owners have their doubts too even naming VTEC Vacillating Torque Engine Compartment... granted it worked

on heavy cars but it's more of a unwanted bump in the powerband on a light bike...


2013MakotoSanMrRC45_zps119ae64b.jpg

 

gallery_3131_5511_17541.jpg

Makota San down on cannery row...
gallery_3131_5511_48694.jpg

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Personally, I'm in the pro-VTEC camp. My only real criticism (6th gen experience specifically here...) is that it would be a more usable system if the VTEC transition point was on a curve... If I'm at 20% throttle, I probably don't need the extra valves until higher in the rev range. The one time I really don't like it is when I'm just easing into the throttle coming out of a curve and I suddenly pass the threshold and without warning I suddenly have more juice.

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I forget who I swapped Mr.RC45 for their VTEC VFR north of Eureka Ca... I was so surprised to feel the hit in Honda's famous linear power ban that I thought I was bumped from behind... it was like I was back on the old cammy hit I4s...

H36WestCoastMeet.jpg

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On 7/10/2019 at 1:51 PM, 2015vfr said:

Last time it happened I had been riding for over 10 minutes, in 5th gear accelerating on the freeway, at the transition, brief loss of power (bike jerks/hesitates for half a second) and then more power as the revs climb.

I'm willing to bet you're not giving enough throttle input. The less time your rev counter spends in the transition zone, the smoother it becomes. Change your shift points accordingly. 

 

 

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No problem here, ever on two VTEC VFR's.  The argument that VTEC doesn't belong on bikes has gone on at least 8 million times now.  It just doesn't matter any longer....

 

Adapt, adjust, and overcome.  

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3 hours ago, SEBSPEED said:

I'm willing to bet you're not giving enough throttle input. The less time your rev counter spends in the transition zone, the smoother it becomes. Change your shift points accordingly. 

 

 

My thought exactly, same with quickshifters

 

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2 hours ago, Bent said:

No problem here, ever on two VTEC VFR's.  The argument that VTEC doesn't belong on bikes has gone on at least 8 million times now.  It just doesn't matter any longer....

 

Adapt, adjust, and overcome.  

 

Well said.   

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On 7/10/2019 at 12:32 AM, Saoirse said:

I'll never understand why they put vtec in a motorcycle, it's just a wrong idea from the start.

Agreed, I just hear an increase in the noise and not much more. It makes the valve adjustment more complicated. I don't really care I like this bike anyway. 😊

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