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Can We Reduce Engine Braking?


Guest ohlarikd

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Guest ohlarikd

Synching the starter valves and setting the idle correctly will definitely help the engine run smoother and I hope it corrects what you are experiencing... Summer is coming, get it right and get riding :cool:

Thanks! Riding has begun, and then ended already, but I am determined to fix this! I love the VFR, so I want to get it right. Clearly this is not normal.

I shall hold the Red Honda proudly high in hand!

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I repeat. Racebikes program their fuel injection to ADD fuel at 0% throttle openings, and high engine revs.

This reduces engine braking and helps with corner entry as the rear of the bike isn't skidding and pattering around, throwing the bike off line.

Yes, slipper clutches also serve this purpose, but they still dial in more fuel at trailing throttle to reduce engine braking.

Not sure how much, or at that RPM's.

Proof:

Haydon-1.jpg

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Guest ohlarikd

I repeat. Racebikes program their fuel injection to ADD fuel at 0% throttle openings, and high engine revs.

This reduces engine braking and helps with corner entry as the rear of the bike isn't skidding and pattering around, throwing the bike off line.

Yes, slipper clutches also serve this purpose, but they still dial in more fuel at trailing throttle to reduce engine braking.

Not sure how much, or at that RPM's.

Hey man, I am with you - I agree. I don't have access to this technology on a VFR though, and I can't do anything about it. I watch WSBK and MotoGP religiously (just watch Jerez Qualifying a few minutes ago). Even Yamaha Race ECUs offer Engine Braking Reduction flashes for their Race ECUs on R1s and R6s.

If someone made a tunable ECU for the VFR, that would be wonderful, but they don't. All I have, like I said before, are some screws and wires... In this case though, I think it may just be a tuning issue.

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I stopped reading when I realize you are an experienced rider that cannot control engine braking. So much so, that you broke into the engine to fix it.

-Drew

You are an idiot. Did you read anything. The bike has a problem.

I very clearly stated the point that I stopped reading.

-Drew

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OP - I sympathize and wish I could be more helpfu but I'm carbed. I got 99 problems but this aint one.

Speaking of alternate programmable ECU's and the like - and I only mention this after the influence of a few adult beverages - what about a Mega/Micro Squirt conversion? This would of course be only if everything else fails. If my brother can convert his '34 V-8 Ford Flathead, I'm sure it wouldn't be too difficult to convert an already FI bike.

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It's a great idea, but to achieve it you would need fly by wire throttle bodies. The main issue is that you want less engine braking, whilst decelerating & keeping, the throttle butterflies open with zero fuel supply will achieve this as you expect. With the TPS at zero & the engine turning, zero fuel is supplied, which is WHY the 5/6th gens have such a strong engine braking feeling. With carbs fuel is always added, so less apparent engine braking.

Now if you adjust the butterflies to be slightly open when TPS is at zero, the bike will stall when you stop, due to to much air & not enough fuel. It will also be impossible to balance the throttle bodies vacuum due to there being NO way to adjust the butterflies separately like you can on a carbed bike !

What you really want is a stepper motor with controller between your throttle cables & the throttle body butterfly actuator, i.e. take the cables OFF the throttle bodies & connect a stepper motor there. Then program the stepper to keep the throttle slightly open when bike speed is above say 10mph, but close fully when throttle is closed below that speed, thus preserving the idle & vacuum balance required at a stop. This would require an electronic throttle & some nifty programming & wire harness interface.

Alternately you can ditch the EFi & fit carbs, a much simpler solution potentially, but full of it's own pit falls !

Have fun.

Edited by Mohawk
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Guest ohlarikd

I stopped reading when I realize you are an experienced rider that cannot control engine braking. So much so, that you broke into the engine to fix it.

-Drew

You are an idiot. Did you read anything. The bike has a problem.

I very clearly stated the point that I stopped reading.

-Drew

I see. So you did not read the whole thread, assumed that I don't know how to ride, and figured I unnecessarily tried to fix something that must be due to my lack of experience. Got it.

My 18 years of riding 7 bikes on and off racetracks has led me to believe that my particular bike has excessive engine braking that I believe can be fixed through some adjustments. I no longer think this issue is per design.

OP - I sympathize and wish I could be more helpfu but I'm carbed. I got 99 problems but this aint one.

Speaking of alternate programmable ECU's and the like - and I only mention this after the influence of a few adult beverages - what about a Mega/Micro Squirt conversion? This would of course be only if everything else fails. If my brother can convert his '34 V-8 Ford Flathead, I'm sure it wouldn't be too difficult to convert an already FI bike.

No thanks, but thanks for thinking about it. Certainly not worth all that effort!

It's a great idea, but to achieve it you would need fly by wire throttle bodies. The main issue is that you want less engine braking, whilst decelerating & keeping, the throttle butterflies open with zero fuel supply will achieve this as you expect. With the TPS at zero & the engine turning, zero fuel is supplied, which is WHY the 5/6th gens have such a strong engine braking feeling. With carbs fuel is always added, so less apparent engine braking.

Now if you adjust the butterflies to be slightly open when TPS is at zero, the bike will stall when you stop, due to to much air & not enough fuel. It will also be impossible to balance the throttle bodies vacuum due to there being NO way to adjust the butterflies separately like you can on a carbed bike !

What you really want is a stepper motor with controller between your throttle cables & the throttle body butterfly actuator, i.e. take the cables OFF the throttle bodies & connect a stepper motor there. Then program the stepper to keep the throttle slightly open when bike speed is above say 10mph, but close fully when throttle is closed below that speed, thus preserving the idle & vacuum balance required at a stop. This would require an electronic throttle & some nifty programming & wire harness interface.

Alternately you can ditch the EFi & fit carbs, a much simpler solution potentially, but full of it's own pit falls !

Have fun.

Believe it or not, I have thought about all this. I reasoned that if I just moved the butterflies, that I would screw up all kinds of situations at idle and on the gas, messing up the air/fuel ratio and run too lean. Luckily I found these air holes to mess with - hopefully I can achieve the same thing.

Then I thought of separately controlling the butterflies like you suggest to only partially open in particular situations, like upon 0% throttle and in certain gears, like when downshifting. Then at low speed the butterflies would close. Then I snapped out of it.

I came to reason that the bike must be mal-adjusted. It can't be THIS bad.

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I have always thought that engine is braking is directly related to engine low end torque and thus engine configuration. Example: given equal displacement a V4 typically has more low end torque than an inline 4 (due to firing order), a V twin even more due to larger cylinder displacement and a single the most. For a few years I split time between a KLR650, an SV650, a VFR800 and a Concours 14. The VFR and Connie had similar engine braking. The KLR had the most but it did not bother me because I rode it like a dirt bike. The SV gave me fits at first because I tried to ride it like the other two street bikes but the engine braking would spin the rear tire on downshifts. But within days I adjusted by simply staying in a higher gear when decelerating.

BTW my Concours 14 has secondary butterflies controlled by a stepper motor and the ECU but they are their to reduce abrupt acceleration in lower gears, has nothing to do with engine braking. The C14 has a slipper clutch to control engine braking but in 100,000 miles I have never noticed it. As for the secondary butterflies like many other owners, I removed mine to IMPROVE low speed driveability

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Guest ohlarikd

I have always thought that engine is braking is directly related to engine low end torque and thus engine configuration. Example: given equal displacement a V4 typically has more low end torque than an inline 4 (due to firing order), a V twin even more due to larger cylinder displacement and a single the most. For a few years I split time between a KLR650, an SV650, a VFR800 and a Concours 14. The VFR and Connie had similar engine braking. The KLR had the most but it did not bother me because I rode it like a dirt bike. The SV gave me fits at first because I tried to ride it like the other two street bikes but the engine braking would spin the rear tire on downshifts. But within days I adjusted by simply staying in a higher gear when decelerating.

BTW my Concours 14 has secondary butterflies controlled by a stepper motor and the ECU but they are their to reduce abrupt acceleration in lower gears, has nothing to do with engine braking. The C14 has a slipper clutch to control engine braking but in 100,000 miles I have never noticed it. As for the secondary butterflies like many other owners, I removed mine to IMPROVE low speed driveability

Interesting observations with many types of configurations. I don't think anyone will accuse the VFR of having a lot of low end torque. I have had a singles, inline 4s, and a V-four. Sadly no V-Twin, but some day. There is definitely differences in engine braking between bikes/engines. Must be some complicated interaction between displacement, cam profiles controlling when and how much valves are open, and how much air is let in on the intake stroke at 0% throttle.

The slipper clutch is not meant to control engine braking in normal situations, so yes it has no effect there. I had one on my supermoto where you downshift 3 times and drop the clutch into a turn - that is when it comes into play, sliding the rear end on purpose, not locking. On a super bike, it is not used to such extreme, but it does keep the rear from locking up in extreme corner entry situations hard on the brakes - I don't have slipper experience on a sportbike at the track though. A slipper is meant for advanced track riding, not really the street. I never understood why the Connie has a slipper clutch - was there ever an issue that they were trying to solve? Sort of like paddle-shifters in cars... they were meant for F1 drivers who can't possible let go of the steering wheel to shift. Why is it in an SUV or sedan?

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I don't think anyone will accuse the VFR of having a lot of low end torque.

Understatement of The Century! :wink:

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I have heard people say that a V-4 has more low end torque than an inline 4 of the same displacement due to the V-4 firing order. Aren't two cylinders firing at once whereas with in I4 only one fires at once or have I got that wrong? Anyway I agree the VFR is limp in first gear but I thought that was due to gearing.

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. Must be some complicated interaction between displacement, cam profiles controlling when and how much valves are open, and how much air is let in on the intake stroke at 0% throttle.

Yes but it is the compression stroke that actually creates the engine braking, right?.

I think it is mostly a factor of cylinder volume and compression ratio but I guess cam profiles are also a factor. Maybe VTEC has a big impact. Are you feeling the objectionable engine braking above or below the VTEC kick-in?

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I don't think anyone will accuse the VFR of having a lot of low end torque.

Understatement of The Century! :wink:

Depends on everyone's interpretation of "low end", right? For some, it's anything below 5000 RPM. Or 3000 RPM. Etc, etc...

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A friend of mine has The Ducati Panigale, virtually every parameter is adjustable on that baby.. including engine braking.. and IIRR this adjustment was achieved by the system modifying The exhaust valve position.

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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!

I dont rate the VFR engine braking as excessive , but it is there, freer exhaust should loosen it up some, or just learn to use it.

Did you come from 2 strokes?

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Turning the throttle open will reduce engine braking and make the bike corner better. Setting your corner speed in a straight is the only time I am completely off throttle down shifting and use the engine braking. Turning in I begin to open the throttle significantly to adjust my corner speed and open it up as I exit. You just need to get familiar with the power and handling of the bike and shift smoothly. I have over 90k miles riding my 98 and have ridden the 6th gen as well. You don't need to modify the bike. Just keep riding it and adjust your riding to the bike.

My Tuono has a clutch mechinism that mimics a slipper clutch somewhat at closed throttle. It's a V twin so engine braking can be an issue with handling.

The V four is such a sweet power plant in that it give a very nice flat torque curve through out the power band. It doesn't get much better than that.

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Guest ohlarikd

I understand how to set all the Starter Valves now, so I will try that. Going to get some vacuum testers and give this a try.

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Yesterday I took off my PAIR valve and hoses and capped the inlets. Today my bike decelerates much more smoothly, more like a motorcycle should.

I also disconnected the battery for ten minutes, reconnected started and let it go through a couple of fan on/off cycles without touching the throttle. Saw something about it on biker's oracle for the gen7, it's supposed to baseline the EFI system. Unfortunately, I didn't get a chance to take it out between that and removing the PAIR.

Might be worth a shot for you to try, it made a noticable difference on mine. Also smoothed the roll on. Down side of taking out the PAIR is possible plugging off the cat. Good reason to get headers. ;o)

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The "PAIR" system injects air into the exhaust outlet ports after the valves, outside of the combustion chanbers to promote continuing burn of any unburnt gasses leaving the combustion system. Not really sure how taking that system off a bike will affect running performance...... unless maybe it might speed up exhaust evacuation in the manifolds. I always thought that removing PAR was mostly an exercise to remove weight from the bike.... :rolleyes:

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Yep. Problem is they dump the fresh air in the exhaust directly in front of the O2 sensors, ECU thinks the motor just went REAL lean and bumps the duty cycle way up, makes the motor run really fat. Makes it really snatchy at small throttle openings. It makes the emissions look better, but screws up the mixture big time. And weighs at least 4 oz. ;o)

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Yep. Problem is they dump the fresh air in the exhaust directly in front of the O2 sensors, ECU thinks the motor just went REAL lean and bumps the duty cycle way up, makes the motor run really fat. Makes it really snatchy at small throttle openings. It makes the emissions look better, but screws up the mixture big time. And weighs at least 4 oz. ;o)

Oh, it's mostly an O2 sensor/EFI issue then with PAIR.......Thanks for clearing that up for me.....

I assume then that carbed/non-O2 sensored VFRs with PAIR systems need not worry then....

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Nope, shouldn't make any difference on those at all, will just make pipe emissions lower if you're doing smog testing.

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Guest ohlarikd

Ok, thankfully I took pictures 'before' I went haywire. Got things back in order using the manual and YouTube (KaldekBock), no more crazy 4000 RPM spike in 1st gear (not sure what that was).

Need to order a 4-gauge vacuum gauge to sync, so it will be a few days I guess.



i can not wrap my head around why you opened up the starter valves instead of just cranking up the idle screw on the side of the bike.

anyways there is a pdf of the service manual in the downloads section of the site.



http://www.vfrdiscussion.com/forum/index.php/files/category/2-owners-manuals-and-other/

Well well, now that I understand how all this works, I can see now why you said turn up the Idle. It directly opens those same valves by pushing on the plate. Live and learn!

Once I get them synced again, I will mess with the Idle which should reduce the engine breaking... fine! I get it now :)

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Good to know my videos are still out there helping folks even though I've moved onto BMWs...

Anyway, the engine braking was one of my FAVOURITE things about my VFR. I used to love slamming it down a gear from high revs and just letting the bike slow me down while roaring its head off. *Especially* in traffic! The sound of a VFR with aftermarket pipes on the overrun is something I will miss forever.

Even after ten years, my 2002 VFR800 still turned heads with its fat baby-eight exhaust note. If only the fuel injection wasn't so wonky...

Also worth pointing out that I believe Ducati controls engine braking in the new Panigale motor by keeping the valves open on the overrun (I think it was exhaust valves). Doesn't help with the VFR of course, but people have solutions to the problem out there.

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PS: The idle thing that would open and close by itself is part of the wax idle unit. Read up on it.

There are at least a couple threads about how to make your own manometer for under $20, and a few threads on how to do a sync.

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