My 6th Gen VFR has a tremendous amount of engine braking. I don't think its just mine since I have read others comment. I think it is way too much and wonder if it can be reduced when the throttle is shut off.
I am just thinking out loud, so any ideas or 'no-goes' are helpful. There are 4 butterfly throttle plates, correct? If I could get half of them to remain very slightly OPEN when the throttle is shut, would it reduce vaccuum? I understand that would make the cylinders uneven when throttle is open more, but in theory? Or is there a screw-stop that can be adjusted to leave all 4 plates open slightly when throttle is off?
Basically, I don't want any fuel going in when throttle is closed but butterflies are partially open - is that even possible? I don't know what sensor will cause the injectors to fire...
Someone on here has looked into the slipper clutch, which IIRC never happened.
Nope. Slipper clutch has been successfully fitted to a 4th gen VFR. I don't think that's what is really going to help.
Leaving half the butterflies off from the other is going to make the engine run uneven and probably really poor in general. You should just increase the idle if that's how you want to go about it.
Of course, the absolute simplest solution is to stay in a higher gear, or just pull the clutch in, or not let off the throttle as much. All things you can do right now, no downpayment or modification necessary. :beer:
Thanks for the replies! I have had slipper clutches, but they really shouldn't be engaging on the street in normal riding. To be honest - engine braking at this extreme level is not such a huge problem on a track. But day to day commuiting, it is quite a chore.
I had mentioned leaving some butterflies open, but then figured it would have poor throttle response. So I would need them all cracked open equally, but still have the Throttle Position sensor at 0 to avoid fuel. I have a Power Commander V, maybe I can mess with that to adjust fueling if I somehow manage to keep the throttle plates open at IDLE.
I know about increasing the IDLE, but I'd rather not have it that high normally if I can help it. Might be worth a try to adjust it though - but I can't imagine finding a happy medium there.
And yes, I understand the lower gear, changing sprockets, pulling clutches in... this is my 7th or 8th motorcycle, and the first time I have had to to actively reduce engine braking. So other than working around the issue, I am curious about a technical solution.
I will remove the tank this weekend and take a cursory examination of the situation. Can I get the butterflies to remain open with Fuel still at 0?
Doesn't a free flowing aftermarket exhaust also helps reduce engine braking?
Well backpressure is something different than engine braking. As far as I can tell, engine braking is caused by the vaccuum in the cylinder when it is on the intake stroke, but the throttle plates are closed, not allowing any air to enter the cylinder. This vaccuum is what you feel. The exhaust valves are open when getting air OUT of the cylinder, which is not a large source of engine braking.
Maybe with your power commander. Maybe. Other than that I'm really not sure how else, other than by staying in a higher gear to lower the rpms when you're letting off the throttle. Aftermarket header might help if it flows more freely, but I don't know if that's the best for the overall engine performance. And it's expensive.
Thinking about it, what will having 0 fuel and the butterflies open do to reduce engine braking?
Thinking about it, what will having 0 fuel and the butterflies open do to reduce engine braking?
On the intake stroke, having the butterflies slightly open will allow air into the cylinder and reduce vaccuum, and thus engine braking. You don't want fuel in there since that is going to light and produce power - almost like increasing the idle basically. Again, this is just my understanding at this point.
I have read of race ECUs on some bikes that can keep the secondary butterflies open a bit to have this reduced vaccuum effect. We don't have such secondaries however, but the theory is the same. I think Yamaha has an engine brake reduction component in the race ECU.
I'm not at all familiar with this topic but just trying to be helpful.
In the thread below luv2leanit (sp?) in post #30 says he altered engine braking on a Yamaha with an ecu reflash. Maybe a similar function is burried in your power commander or maybe a reflash could solve your problem?
I'm not at all familiar with this topic but just trying to be helpful.
In the thread below luv2leanit (sp?) in post #30 says he altered engine braking on a Yamaha with an ecu reflash. Maybe a similar function is burried in your power commander or maybe a reflash could solve your problem?
Good luck!
http://www.vfrdiscus...nleashed/page-3
Thanks for the link. If there was such a device available for the VFR800, then it would be most helpful. But the VFR is just not supported with anything other than the Power Commander. Also, I believe the success of many of these ECU flashers is due to throttle-by-wire on newer bikes, which greatly opens up the options when it comes to tuning.
We have mecahnical cables, screws. and the power commander to work with, as far as I can tell.
I have always adjusted the idle to 1400 on all 3 VFR800s I have had.. remember, the manual says 1200+/-100.. so I'm only a smidgen over that spec.. The weak charging system on these bikes also benefits from this slight increase, compensating for low charge at idle when fan comes on.
I must say though, my recent substitution of the OEM exhaust for Laser Extremes really backed the engine braking off considerably, to the point where I have had to conscientiously adjust my braking habits to avoid blowing corner entry.. had a few heart in mouth experiences at first.
Well, I put the IDLE back to 1200. For some reason, [when I set the Idle to 1800] the bike would hang at 3000 RPMs in I think 2nd or 3rd with no throttle input. I guess that little extra air, the fuel mapping, the ECU, FI, etc. all conspire to just not like a 1800 Idle.
So - I put it back down to stock 1200 and it rides perfectly now. Well it rides as it was designed. So my 12 page thread turns out to be what everyone told me - a waste of time! :)
I can take a beating. At least I know now and can let things be.
Little question, did you remove valve-pairing and flapper?
In short, did you remove the CO2-maffia rubbish that kills the real handling of the bike?
As idle and low speed problems are typical a problem of Valve-pairing-system (that you want to remove/kill) and Flapper (that you also want to kill).
When you do that, you end up with a new bike that rides a 1000x times better then stock.
And fun part, it costs only 5 cents to do it in a screw (flapper vacume-tube close) and 5 cents pairing (marbles to block it.)
This crap is on all new bikes, not just the VFR's. Remove the CO2 maffia crap and it runs far better then anything you tried so far :cheerleader: