Can We Reduce Engine Braking?

[Guest ohlarikd]

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...

Thanks for any ideas!

[CandyRedRC46]

lol bump up the idle.

I personally could use more engine braking.

[Rice]

Interesting question.

Someone on here has looked into the slipper clutch, which IIRC never happened.

[YoshiHNS]

Interesting question.

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.

[Guest rcracer]

Doesn't a free flowing aftermarket exhaust also helps reduce engine braking?

[Guest ohlarikd]

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.

At least that is my understanding.

[YoshiHNS]

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?

[Guest ohlarikd]

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.

Edited May 3, 2013 by ohlarikd

[Guest ohlarikd]

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.vfrdiscussion.com/forum/index.php/topic/73674-has-anyone-tried-this-yet-ecu-unleashed/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.

[Guest ohlarikd]

If I mess with the butterfly valves somehow to have them slightly open at Idle, it seems like the PowerCommander will allow me to calibrate the Throttle Position Sensor back to 0% when the throttle grip is fully closed:

TPS CALIBRATION

It is important that the PCV software TPS read 0% when the

bike is fully warmed up and at idle. If it needs to be reset

make sure the bike is fully warmed up before resetting. With

the engine on, click on Reset, open throttle to the stop and

close, then click OK.

[Guest ohlarikd]

Does anyone know if increasing the IDLE also adds more fuel? How is this IDLE increase accomplished - is it just opening the butterflies? I am wondering if I am performing the same effect by adjusting the butterflies, which may increase idle. I don't want that to happen.

All this will be clearer to me when I get the bike apart tonight or tomorrow...

[Beck]

I do not understand why a VFR might have more engine braking than any other 4 stroke, 4 cylinder bike and why this is all of the sudden a problem after all the previous 8 bikes you had (Some I assume were large multi-cylinder bikes like the VFR). could there be something other than the engine that's not letting your VFR to roll as easy as your previous bikes on off throttle?? could there be a drive chain adjustment needed as you might be getting too much lash from it, giving the impression of more than usual engine braking??

Beck

95 VFR

[Guest ohlarikd]

I do not understand why a VFR might have more engine braking than any other 4 stroke, 4 cylinder bike and why this is all of the sudden a problem after all the previous 8 bikes you had (Some I assume were large multi-cylinder bikes like the VFR). could there be something other than the engine that's not letting your VFR to roll as easy as your previous bikes on off throttle?? could there be a drive chain adjustment needed as you might be getting too much lash from it, giving the impression of more than usual engine braking??

Beck

95 VFR

Different bikes have different levels of engine braking, from what I have read on the web. BUT I had a 2006 R1 and a 1997 YZF1000R, a GSXR750 race bike, various supermotos, and I have never noticed a large amount of engine braking, relatively speaking. This VFR is really strong in that area. I had initially commented on engine braking 2 years ago when I got the bike, and it seems that it is normal for the 800. Don't ask me why it is more... wish I knew!

The bike has lash (another complaint), but once the lash is taken up within milliseconds, you can still feel the braking force as the revs drop.

As for other factors - I changed the tires a day ago, and both front and rear wheels spin freely, no drag. Plus, if I pull the clutch in a low speeds, it will roll freely as well.

I don't see any other factor other than the engine that is contributing to this, but I welcome any more ideas. I am not trying to make some breakthrough here, I just want it to feel 'right'.

PS - another theory I had was the cam profile, or quite possibly the VTEC. The way the cams are profiled and the way they only use TWO intake valves below ~6250 RPMs could contribute to a greater vaccuum. Just a thought, no real evidence. But VTEC is the main difference between this bike and my others.

Edited May 3, 2013 by ohlarikd

[AndyB]

The size and weight of the flywheel will affect the amount of engine braking.

[Rush2112]

Open your butterflys slightly... with your right wrist. If you don't like the max engine breaking reduce it with a little maintenance throttle instead of snapping the throttle completely closed. Our bikes don't have ride by wire so the ECU can't do it for you.

[Guest ohlarikd]

Open your butterflys slightly... with your right wrist. If you don't like the max engine breaking reduce it with a little maintenance throttle instead of snapping the throttle completely closed. Our bikes don't have ride by wire so the ECU can't do it for you.

Being a fellow Rush maniac, I will take your advice politely :) But in reality, none of my 7 other bikes were ride-by-wire, and I never gave it a second thought. I don't think I should have to ride around the issue (whether it is an issue is a matter of opinion, and what you are used to riding). Keeping the throttle slightly open while decelerating is quite odd. Again - when on a racetrack, you are simultaneously braking, blipping, downshifting in rapid succession - so this is NOT an issue. But daily commuting when you are on and off throttle all the time, it is quite irritating and unlike any other bike I've owned.

[2thdr]

I'd like to see a poll and see how many folks think this is an issue. I've been active around here for 3 years and this is the first thread I've seen on the complaint...

[Veefer800Canuck]

you could theoretically program a Power Commander to add more fuel at 0' throttle opening, and any RPM levels above idle. (say 2000RPM+?)

This would have the effect of reducing engine braking on trailing throttle.

They have done this on WSB racebikes to make corner entry easier.

Most notably the Foggy Petronas FP-1. That thing would belch fire out the exhausts something fierce!

[Guest ohlarikd]

I'd like to see a poll and see how many folks think this is an issue. I've been active around here for 3 years and this is the first thread I've seen on the complaint...

Not interested in a poll. If I think its a problem, then its a problem. If someone does not agree, then they can move along.

[YoshiHNS]

Open your butterflys slightly... with your right wrist. If you don't like the max engine breaking reduce it with a little maintenance throttle instead of snapping the throttle completely closed. Our bikes don't have ride by wire so the ECU can't do it for you.

Being a fellow Rush maniac, I will take your advice politely :) But in reality, none of my 7 other bikes were ride-by-wire, and I never gave it a second thought. I don't think I should have to ride around the issue (whether it is an issue is a matter of opinion, and what you are used to riding). Keeping the throttle slightly open while decelerating is quite odd. Again - when on a racetrack, you are simultaneously braking, blipping, downshifting in rapid succession - so this is NOT an issue. But daily commuting when you are on and off throttle all the time, it is quite irritating and unlike any other bike I've owned.

Other than playing around with the PC, it might just be something you have to ride around. This bike isn't your other 7 bikes, so it's no surprise that it feels different. In fact, I would bet a fiver that all those other bikes all have different amount of engine braking, and the VFR's just stands out more. I have three different generation VFRs in the garage, and they are all pretty different from each other, and I ride them all a little different because of it. I really can't offer a solution that meets your needs other than not closing the throttle off completely, staying lower in the revs, and playing with the PC.

[Guest ohlarikd]

Other than playing around with the PC, it might just be something you have to ride around. This bike isn't your other 7 bikes, so it's no surprise that it feels different. In fact, I would bet a fiver that all those other bikes all have different amount of engine braking, and the VFR's just stands out more. I have three different generation VFRs in the garage, and they are all pretty different from each other, and I ride them all a little different because of it. I really can't offer a solution that meets your needs other than not closing the throttle off completely, staying lower in the revs, and playing with the PC.

Thanks Yosh. Yeah, I have been riding around it for two years, but for some reason I decided today that I would see if there was a solution. I'm gonna give it a whirl. I don't know if raising the IDLE will help at all, unless that results in the butterflies being open at IDLE. Curious - must investigate!

I really don't have many options here, given the lack of aftermarket support in terms of engine parts and electronics for the VFR.

[Alaskan]

I noticed the same thing when I first got my 6th Gen. IMO, this isn't so much engine braking per se as it is the lousy stock fueling at small throttle openings. It was either "on the gas" or it was "off the gas" - annoying as hell. It felt like I was chopping the throttle all the time. A more careful right wrist is one solution, but this problem disappeared after I installed a PCIII and paid for a dynotune.

[Guest ohlarikd]

I noticed the same thing when I first got my 6th Gen. IMO, this isn't so much engine braking per se as it is the lousy stock fueling at small throttle openings. It was either "on the gas" or it was "off the gas" - annoying as hell. It felt like I was chopping the throttle all the time. A more careful right wrist is one solution, but this problem disappeared after I installed a PCIII and paid for a dynotune.

Yes, that is a definite issue, which is why I got the PC5 and a new throttle cam immediately. And the VTEC issue... all solved!

I don't think engine braking can be solved by the PC5, but I may be able to mess with it at IDLE settings and TPS settings.

[Beck]

So, is this more of an EFI/fueling/FI issue then?

IIRC, at least with carburetors, the butterflies usually have small bleed holes on them so the air supply is not totally shut on off throttle. Not sure if they were meant more for idling but maybe they also help to keep transition to off throttle to be less abrupt?

As for my 4th gen, I never found it to have too much engine braking as I enjoy very much the off-throttle run on burble I get from the bike and I never felt the bike slow down too much when doing so....could it be you are just in too low a gear when you go off throttle??... Maybe its also more of a subjective perception thing on what might be too much engine braking for an individual might be quite normal to the next guy.....

[Guest ohlarikd]

So, is this more of an EFI/fueling/FI issue then?

IIRC, at least with carburetors, the butterflies usually have small bleed holes on them so the air supply is not totally shut on off throttle. Not sure if they were meant more for idling but maybe they also help to keep transition to off throttle to be less abrupt?

As for my 4th gen, I never found it to have too much engine braking as I enjoy very much the off-throttle run on burble I get from the bike and I never felt the bike slow down too much when doing so....could it be you are just in too low a gear when you go off throttle??... Maybe its also more of a subjective perception thing on what might be too much engine braking for an individual might be quite normal to the next guy.....

Well I definitely agree that perception is part of it. Depends on what you are used to, and what you've ridden before, or if this is your first bike. I don't think its fuel, but more on the vacuum side.

On my way home, IF I could manage to keep the butterflies open a bit, it will throw off my fuel mapping. But maybe the Autotune can self correct that. Anyway, step one is to see if I can open the butterflies at all at IDLE, and if it has any effect...