According to a forum member on VFR World, it is possible to 'hotwire' the VTEC solenoid to make the bike run in VTEC mode all the time.
Here is the post..
The VTEC solenoid is located in the valley of the engine under the throttle bodies. It has a single wire, green with yellow stripe, connects to a sub harness that comes out to a six pin connector behind the left fairing. From there it goes up to the ECU pin B3. Disconnect that wire anywhere between the solenoid and the ECU. Connect the engine side to +12v to run four valves per cylinder at all times. Connect the ECU side of the G/Y wire (ECU B3) to one side of a 1k resistor, and the other side of the resistor to ground. The resistor will provide enough current on the VTEC circuit to pass the ECUs diagnostic check and eliminate an error, same as what is done for the O2 elims. You now have a non-VTEC 6th gen. Get a good tune and enjoy!
My only main gripe about the 6th gen VFR is the VTEC can be annoying at times, it's smooth as silk 95% of the time but it's that 'kick' and sometimes it does it, sometimes it doesn't and to eliminate it would make the bike perfect.
I am still surprised after all these years that there's no work-around, could this be it?
I once heard about somebody that was able to eliminate VTEC (i.e. all 16 valves were operational at all times.) I also remember reading the motor ran poorly. I'm not saying it's impossible to have a good running VTEC motor without the VTEC funcion. Had he played around with it long enough, who knows what he could have accomplished. Maybe he needed to port and polish the heads and regrind the cams, I don't know. Before and after dyno figures would have been interesting to look at but I never saw them.
One thing I know has been done is an Englishman on the European VFR forum swapped the VTEC motor with a 5th gen. motor. He ran into a number of issues with some of the wiring not having the same connectors, though. As far as I know, once he worked all the bugs out, it ran flawlessly. Now imagine a 6th gen. VFR with a torocharged 5th gen. motor. If you could get the packaging to fit, that would be way cool. :fing02:
Now imagine a 6th gen. VFR with a torocharged 5th gen. motor. If you could get the packaging to fit, that would be way cool :ohmy: :wheel: :ph34r: :wub: :wub:
I have been in touch with someone who can try this on my VFR so late this month or early January I'm going to ride down there and spend the whole day seeing if this is possible
[image: View Post]jasonsmith, on 05 December 2009 - 04:38 PM, said:
[image: View Post]soichiro, on 05 December 2009 - 12:10 PM, said:
It has been discussed many times. I think mapping is the biggest enemy. I love my vtec.
Mapping will be a must. A Power Commander and whole bunch of Dyno runs will be in order. I love my VTEC too.
I forgot to mention that. It's probably more important than doing any kind of head work (although I do think both would be necessary for optimum performance.)
[image: View Post]vfr_steve, on 06 December 2009 - 07:48 AM, said:
I have been in touch with someone who can try this on my VFR so late this month or early January I'm going to ride down there and spend the whole day seeing if this is possible
I shall let you all know how I get on
If your friend can pull it off, that would be awesome. I think I can speak for everyone on this forum in saying we'd like to see before & after dyno charts.
[image: View Post]rodm850g, on 06 December 2009 - 10:53 AM, said:
Guys,
I know I'm crazy ut I want a 6th gen bike with a new 5th gen motor....
Rod
You, too, huh? With a 5th gen. motor you wouldn't have to deal with CCTs and valve jobs cost half as much. However, I'd take a 6th gen. with a VTEC motor over a 5th gen. with a 5th gen. motor any time.
dont sell the vtec motors short...
one thing that they do have on their side,
ease of cylinder head milling, for added compression.
try and do that with gear driven cams. :goofy:
now with that being said, the fifth gen motors are a gem of an engine and have many more pluses than the vtec's, but i thought i would bring a good quality to the table.... :fing02:
There's no reason that I can think of beyond mapping of fuel and ignition (especially fuel) that a 6th gen motor couldn't be "on VTEC" at all times. What I would expect is, it will take a noticeable amount more fuel to run the bike on all 16 valves which make require a bit more spark lead. Which is going to be impossible to deal with with just a Power Commander and we come back to a solution like a Microsquirt. That said, this may not be the case, if we had a combustion engineer in the house maybe we could get a more authoritative answer.
Let's assume a Power Commander could be enough to deal with this. Eventually I would want to remove the solenoid entirely so there is one less failure point and less needless complexity on the bike. Can this be done, to run the oil circuit wide open at all times? I've never examined how the VTEC solenoid actually interacts with the cam drive to bring the bike in and out of VTEC.
Its also possible, (but I'm only guessing) that the valve timing on the vtec valves may be a bit more radical than on the non vtec valves, leading to poor low speed running and torque at lower RPMs.
The other problem that comes to mind is the vtec system is operated by oil pressure, and what if the oil pressure drops, say when idling on a hot day, would it cause the vtec to drop out intermittently?
Has anyone explored the possibility of replacing the vtec buckets with standard buckets and shims? This would be a better way to do it if you are going to do it at all, if it is possible IMO.
Having said that, I have no problem with my vtec. The last few rides that Ive had since I gutted the cat and loaded a new map, I wondered if the vtec was working because I could not detect the transition at all.
[image: View Post]dogman, on 07 December 2009 - 07:03 PM, said:
Its also possible, (but I'm only guessing) that the valve timing on the vtec valves may be a bit more radical than on the non vtec valves, leading to poor low speed running and torque at lower RPMs.
I am also guessing that one of the reasons for the two-valve operation was to induce a "swirl" when filling the cylinder which would've helped low-speed combustion. Not sure how much of that efficiency can be regained with a new map, or if it matters...
Some of you have read this already, I posted it a few months back in a similar discussion. It's an engineer's analysis of the effects of running on 2/4 valves. Interesting info for all.
I've had a little think about your dilemma.
When a 4 valve combustion chamber runs as a 2 valve the in cylinder motion will increase alot. This is good for a fast burn and good if you want to dilute your charge at part load by leaning off the mixture or perhaps running alot of Exhaust Gas Residual for good fuel economy.
Sometimes too much motion can lead to excessive heat loss and a slightly harsher combustion, but this is slight and I doubt you would notice it on a motorbike over all the other noises. I cant see at all how running in 2 valve mode could cause a snatchy and surgey throttle progression. I also don't see any difficulty in 'tuning the fuel delivery' while in two valve mode- this is a relatively simple task-especially on a fuel injected engine.
The only things that spring to mind is that the engine runs ALOT of overlap- so alot of exhaust gas residual stays in the cylinder- which degrades the combustion. This factor will have a marked effect. Perhaps Honda tried to remedy this in part by running the engine as a two valve to increase EGR tolerance. However perhaps this wasn't enough. At higher speeds- the gas dynamics in the cylinder from efficient intake and exhausting is such that the exhaust residual left in the cylinder is very much lower so this roughness is longer apparent.
So to reiterate I'm 95% sure it's not to do with the two valve operation mode itself. I've run many 4 valve engines in 2 valve mode- on Valvetronic type projects with no detrimental effects.
IMO there is extensive engineering thought going into a modern engine's design, most of it is beyond the common man's (such as myself) understanding and/or development capability. Making any change may provide marginal improvements in theory but there will be downsides in practice. Honda engineers did their homework in optimizing a long list of parameters with this engine.
[image: View Post]dogman, on 07 December 2009 - 07:03 PM, said:
Its also possible, (but I'm only guessing) that the valve timing on the vtec valves may be a bit more radical than on the non vtec valves, leading to poor low speed running and torque at lower RPMs.
The other problem that comes to mind is the vtec system is operated by oil pressure, and what if the oil pressure drops, say when idling on a hot day, would it cause the vtec to drop out intermittently?
Has anyone explored the possibility of replacing the vtec buckets with standard buckets and shims? This would be a better way to do it if you are going to do it at all, if it is possible IMO.
Having said that, I have no problem with my vtec. The last few rides that Ive had since I gutted the cat and loaded a new map, I wondered if the vtec was working because I could not detect the transition at all.
The Vtec valves are different that the regular valves, with an extra spring or something...I just adjusted my valves and the spring comes out, so I assume there is another or something to hold the valve closed. I imagine you could just leave the adjuster buttons in to force the valves open, but I think the effort to make them stay open and still run correctly would be nearly insurmountable...just take Timmy's advice and shoehorn a 5th gen motor in...the wiring would be simpler and more straightforward to adapt.
End of thread · 20 posts recoveredWayback Machine snapshot 12 Apr 2010