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Lorne

eliminating VTEC on 6th Gen

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I don't recall anyone at VFRD experimenting with the VTEC system so as to force a 6th gen to operate all 16 valves all the time. Not even sure how to best accomplish this; monkey with the spool valve, or the slide pins, or ?

 

I've owned 5th and 6th gen and never noticed much difference in overall power. Sure, the transition to VTEC can be noticeable, but below and above that point both generations seemed equal.

 

Thoughts, anyone?

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I've wondered this myself. I suspect the proper way to do this would be to modify the slide pin holder so the slide pins are always engaged with the valves irrespective of the spool valve operation.   Or go the whole hog and replace the VTEC valves with the standard valve plus standard bucket and shim. I presume this would then lead to a need to adjust the FI system to suit. Sounds like a black hole down which one could tip money...

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Just thinking out loud, owners that have transplanted a 5th gen motor over have reported keeping the VTEC solenoid attached to the wiring harness to fool the ECU so it still thinks it's activating the VTEC.   Then I suppose it would require figuring out how the VTEC solenoid activates the 2nd set of valves - voltage applied or not.  If the former, maybe run a switched hot wire to the solenoid attached to the engine then to ground, forcing all 4 valves open all the time, then obtain a 2nd solenoid not attached to the engine to keep attached to the wiring harness to keep the ECU happy.  The only out of pocket would be the cost of the 2nd solenoid.  I may be off base on how the solenoid works, but AFAIK it's electrically actuated. 

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Easiest way for me was dropping my 5th gen engine in my 6th gen frame. Now I get the beautiful gear whine, and the wonderful sound of dual underseat staintunes 😁

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Is it not a better solution to get it remapped to smooth out the transition?

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My friend Makota San was a previous 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...  however for some

owners VTEC = Vacillating Torque Engine Compartment...


2013MakotoSanMrRC45_zps119ae64b.jpg

MakotaHRCTristan.jpg

 

Makota San also worked on the NR500 oval piston racer and he plans to
visit the Busy Little Shop some day because I have 2 cylinder blocks
off the NR500 that I packed out of Japan in 1981...

 

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

VTEC.jpg

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Thanks for all the replies. I have a hunch that VTEC is similar to eliminating gear-drive cams; they are solutions to a manufacturing problem that don't necessarily offer any benefit to the owner.

 

I don't particularly dislike VTEC, but am curious how well/badly a 6th gen would run with it disabled. Considering all the different mods folk have performed on their VFRs I am surprised that no one has monkeyed with the VTEC system.

 

To be clear, my biggest gripe with my 6th gen is the throttle response going from closed to slightly open. Secondarily, it's motor isn't as smooth as either of my 5th gens. Elsewise, I prefer the 6th gen - though I sorely miss my yellow '99.

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14 hours ago, BusyLittleShop said:

My friend Makota San was a previous 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...  however for some

owners VTEC = Vacillating Torque Engine Compartment...


2013MakotoSanMrRC45_zps119ae64b.jpg

MakotaHRCTristan.jpg

 

Makota San also worked on the NR500 oval piston racer and he plans to
visit the Busy Little Shop some day because I have 2 cylinder blocks
off the NR500 that I packed out of Japan in 1981...

 

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

VTEC.jpg

I visited the NR500 at the Honda Collection Hall at Motegi a few months back. They were very bold trying that.

 

P1010761.JPG

P1010763.JPG

P1010764.JPG

P1010765.JPG

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4 hours ago, Urbanengineer said:

Interested to see how this works for owners, but as a street bike why would you give up the best of both worlds situation?

 

That assumes facts not in evidence 😉. It remains unproven whether or not VTEC, as fitted to the VFR800, makes it better for the rider than the 5th gen. Would be interesting to see just how a de-VTEC'd 6th gen would run.

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I am sure I have read about this being tried before and the bike ran miserably. Wish I could remember where.

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I believe that this has been tried in the past, forcing the solenoid to engage all the time, and IIRC there was an issue with low oil pressure at low RPM.

Not good for any engine.

That is why I run a 5th gen in my 6th gen.

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2 hours ago, HighSideNZ said:

I believe that this has been tried in the past, forcing the solenoid to engage all the time, and IIRC there was an issue with low oil pressure at low RPM.

Not good for any engine.

That is why I run a 5th gen in my 6th gen.

 

Yeah, low oil pressure would be a major fail. A better long term solution would be to fit standard valve train - if possible.

 

Do I recall correctly that you had to use the VTec engine management module?

 

My biggest grip is the very twitchy off-on throttle response on my VTec. Hasn't improved over the past 75K km. By comparison, my 5th gens carburetted perfect.

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Yep, I just didn't like the VTec profile so went with the 5th gen.

You have no choice but to use the 6th gen ECU as the 5th gen is completely different as far as I know.

I've got a RapidBike Racing module on it and adjusted the ignition advance to suit as well as the fueling.

Sweet as a nut now and just like a real bike should be.

 

The other thing I did do to lessen the twitchy throttle was to change to a quick action throttle.

Used an HRC one with the standard VFR cables.

Just has to find a switch block to suit.

Might sound funny but the quicker action seems to make the low speed twitchiness  much less.

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The reason you have not seen this done, is the best way would be to pull the heads & replace the offending valves with non vtec ones, or fit the Vtec sliding pin in such a way that its always in the engaged position, mechanically. This would solve the oil pressure issue etc. The reason you have not seen this is most VFR owners do not go inside their engines. Same could be said for most bike owners, but more "sports" bike owners get serious work done on their bikes & most other bikes only have one cylinder head that would need pulled off to access the valves.

 

You might be able to modify or make a new slider pin holder that was configured to accept normal shims, otherwise you have to replace half the valve set. This is easily achieved, find a damaged engine from a breakers yard & steal the 4 normal vlave sets, lap the valves & job done, ASSUMING the Vtec valve spring seat is the same on both valves. I've not seen one so can't tell you.  But its a fair bit of home mechanicing, so most never bother.

 

 

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I forgot to say re the snatchy throttle, make sure your starter valves are adjusted corretcly, another PITA job on the Vtec, as you have to strip the airbox off to get to the adjusters. Then make sure you have zero or the absolute minimum throttle cable slack, remember the bar turn test when setting this to minimum, to avoid unwanted acceleration in a tight turn ! Then train your right wrist that a little is just a smidge ! 🙂

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This has been discussed here many moons ago, before 06+ remapping occurred. The consensus was that it wasn’t worth it. A lot of work for a theoretically very questionable gain. 

After 06, this has become moor. 

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