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FZ-07 Engine Braking


bornagainbiker

FZ-07 Engine Braking  

52 members have voted

  1. 1. How do You Feel About the FZ-07 Engine Braking?

    • I like it.
      23
    • I don't like it.
      20
    • I don't care one way or the other.
      9


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I hope I can be forgiven for doing this and I mean no disrespect but I don't like being left wondering who is right about something so I went WIKI and this is what they say is the major cause of engine braking and wheel hop. 

 

"The term 'engine braking' refers to the braking effect that occurs in gasoline engines when the accelerator pedal is released.

When the accelerator is released, the butterfly valve that controls intake airflow (the throttle valve) is closed and the air flow through the intake is greatly restricted (but not cut off completely). This causes a high manifold vacuum which the cylinders have to work against - this saps energy and is where the majority of the engine braking force comes from. The concept can be illustrated by the amount of effort required to blow/suck through a narrow tube vs. a wider one. It is the work the engine has to do against this restricted air flow that provides the braking effect.

While some of the braking force is due to friction in the drive train, this is negligible compared to the effect from the manifold vacuum caused by the air-flow restriction."

 

"Improper engine braking technique can cause the wheels to skid (also called shift-locking), especially on slippery surfaces such as ice or snow, as a result of too much deceleration. As in a skid caused by over braking, the vehicle will not regain traction until the wheels are allowed to turn more quickly. If the driver reduces engine braking by shifting back up, or disengaging the clutch on a manual transmission, traction can be regained."

 

"A slipping or disengaged clutch, or a torque converter, would disengage the wheels or absorb braking energy." - WIKI

 

It appears now that gregjet was right and the slipper clutch he mentioned IS JUSTIFIED, according to wiki. I'm done thinking on it, I'm convinced. Stay frosty, yall!

Beemer

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"Improper engine braking technique can cause the wheels to skid"

 

Nuff Said.


 

Quote

It appears now that gregjet was right and the slipper clutch he mentioned IS JUSTIFIED, according to wiki. I'm done thinking on it, I'm convinced. Stay frosty, yall!

Nuff Said Again.

 

This makes everyone wrong but @Beemer @gregjet and of course Me :)

“Laws that forbid the carrying of arms disarm only those who are neither inclined nor determined to commit crimes.” --Thomas Jefferson quoting Cesare Beccaria

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10 minutes ago, r1limited said:

"Improper engine braking technique can cause the wheels to skid"

 

Nuff Said.


 

Nuff Said Again.

 

This makes everyone wrong but @Beemer @gregjet and of course Me :)

Didn't mean to leave anyone out but gregjet was right on all three points so that's why I said what I did. Still,

cheers.jpg

Beemer

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Well back in the day when slipper clutches and all tha fancy stuff was not made for bikes. Engine braking was all part of the experiance.  Engine braking designed to allow a racer to back a bike in, scrub speed etc.  Smokers came along and true was easier to control but the use of compression releases was an art form to back a bike in.  When the mighty 4 strokers came back slippers started to appear thanks to rekluse.  Advancments in tech thanks to MotoGP began bringing the mighty 4 stroke to a point the average schmuck could ride ;)

No one seems to remember the Big 4 Honda CB750, KZs Etc that would engine brake so bad you would go over the bars or high side.  It was art to learn to ride, not like today with all that fly by wire crap.  Do not get me wrong, my R1 I set the rev limiter to 10.5k for a bit until I figured out the beast because after 10.5 it did things that would make your ass suck up to your ears.  SO when I got the 07, I was in heaven, like a long lost friend  

“Laws that forbid the carrying of arms disarm only those who are neither inclined nor determined to commit crimes.” --Thomas Jefferson quoting Cesare Beccaria

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Kinda like what R1 is saying, I like the extra degree of control. If you don't want to lock up the rear, just rev match. Midcorner, I like being able to adjust the speed up or down with just subtle throttle. I am far too new to a bike to push it, but in the cars I'll use engine braking to really influence handling at the limit. 

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2 hours ago, Beemer said:

I hope I can be forgiven for doing this and I mean no disrespect but I don't like being left wondering who is right about something so I went WIKI and this is what they say is the major cause of engine braking and wheel hop. 

 

"The term 'engine braking' refers to the braking effect that occurs in gasoline engines when the accelerator pedal is released.

When the accelerator is released, the butterfly valve that controls intake airflow (the throttle valve) is closed and the air flow through the intake is greatly restricted (but not cut off completely). This causes a high manifold vacuum which the cylinders have to work against - this saps energy and is where the majority of the engine braking force comes from. The concept can be illustrated by the amount of effort required to blow/suck through a narrow tube vs. a wider one. It is the work the engine has to do against this restricted air flow that provides the braking effect.

While some of the braking force is due to friction in the drive train, this is negligible compared to the effect from the manifold vacuum caused by the air-flow restriction."

 

"Improper engine braking technique can cause the wheels to skid (also called shift-locking), especially on slippery surfaces such as ice or snow, as a result of too much deceleration. As in a skid caused by over braking, the vehicle will not regain traction until the wheels are allowed to turn more quickly. If the driver reduces engine braking by shifting back up, or disengaging the clutch on a manual transmission, traction can be regained."

 

"A slipping or disengaged clutch, or a torque converter, would disengage the wheels or absorb braking energy." - WIKI

 

It appears now that gregjet was right and the slipper clutch he mentioned IS JUSTIFIED, according to wiki. I'm done thinking on it, I'm convinced. Stay frosty, yall!

Actually, in a fuel injected motor, when you close the throttles, the butterflies in the throttle bodies are completely (and I do mean no air gets past) closed. The only air that gets into the motor is thru the idle air control valve - and that's electronically controlled by the ECU.

 

But even with the throttles slammed shut, the amount of engine braking can be modified by how much fuel is injected and maybe in conjunction with an adjustment to that IAC valve's position as well. . More fuel squirts (and/or air allowed past the IAC) will result in less braking effect and less fuel will result in more. Get the FZ reflashed to add more fuel (and/or air)  at high RPMs with the throttle shut and engine braking can be reduced. It's the less fuel scenario that gives the FZ its engine braking and great fuel economy.

 

Slipper clutches (I have one on my Aprilia and love) allow one to be a wee bit sloppy while matching revs and that's a good thing as it's hard to be perfect all the time. Doesn't mean that you couldn't induce a back wheel skid by being big time sloppy, but they sure do smooth out less than perfect hands.

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46 minutes ago, rick said:

Actually, in a fuel injected motor, when you close the throttles, the butterflies in the throttle bodies are completely (and I do mean no air gets past) closed.

That's not true at all

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The compressing of the non firing charge causes wheelhop, but it ISN"T the only cause. It is just magnified on motors with a stroke with a power stroke, and one with NO power stroke where the cyls are compressing. Overlap the compression strokes and it gets sticky. Vtwins with usual crank angles and singles both allow you to feel the compression/power stroke difference, that's all. On dec there is nothing to help overcome the wheel road contact resistance.

However, as pointed out, other things can, and do, cause rear wheel hop on decell. My first experience of rear wheel brake hop ( brake chatter, although it was more of a sermon than chatter) ) was on an NSR250 mc23. The rear shock was old and very tired and the rear wheel was the frightening ancestor of the current Bridgestone fitted to the 07, the BT-23. Any resemblence ot traction, either living or dead, was purely coincidental. My very first race( and I mean my VERY first) and I headed into the end of the straight into a double right hairpin. Put the brakes on and back wheel hopped straight off the track...Yes the NSR was a Vtwin...but it was a 2x125cc twostroke. No engine braking.

 

Did I say I love slippers...The big thing is brake CONTROL.

Go forth and modify my son...go forth and modify...

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Beemer, I think shaft drives are more prone to wheel hop because of the massive nonfloating extra unsprung weight of the shaft and housing. The CX500 used to do it to some extent as well, though Honda's slight reluctance to downshift easily and requiring a clutch action to get a good shift, helped mitigate it a bit. A small blessing in disguise.

BMW's engine speed clutches didn't help...

 

Go forth and modify my son...go forth and modify...

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im fine with the engine braking with my setup...

 

on the FJ-09 forum a select few members have to have a slip/assist type clutch found in the XSR-09 bike(its some mental thing from my perspective) for about $350 in parts to add slip/assit to the FJ-09

2015 fz-07- Hordpower Edition...2015 fj-09- 120whp- Graves Exhaust w/Woolich Race Kit- tuned by 2WDW
 

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18 hours ago, cyow5 said:

That's not true at all

OK< well, maybe saying every single FI motor was too black/white, I've only had my hands on 10 or so. - but  pull off the airbox and have a look.

 

My Aprilia's throttles are closed tight as is my Subaru's. My Aprilia's throttle bodies are notorious for getting a varnish build-up right on the bore where they close/touch that causes the throttle to get a bit sticky after 10k miles or so. A little lacquer thinner on a swab and it's good to go again.

 

If you mess with the throttle stop screw and then re-zero the TPS  thru the ECU, the motor will not have a proper mixture w/o carefully resetting that closed position. To that, many bikes come with those stop screws painted so they can't move. My '96 K11RS BMW and my Aprilia are examples. Change a Guzzi's throttle stop screws (also fixed with paint ), Well, I've read the throttle bodies would have to go back to the factory to get them set properly again.

 

If those plates were allowed to stay open, these motors would not really need an IAC( idle air control valve) - the FZ's sits right between the throttle bodies on the back of the motor) . Fast idle when the motor is cold would also have to be done thru some other mechanism as the IAC assists there as well.

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44 minutes ago, rick said:

OK< well, maybe saying every single FI motor was too black/white, I've only had my hands on 10 or so. - but  pull off the airbox and have a look.

 

My Aprilia's throttles are closed tight as is my Subaru's. My Aprilia's throttle bodies are notorious for getting a varnish build-up right on the bore where they close/touch that causes the throttle to get a bit sticky after 10k miles or so. A little lacquer thinner on a swab and it's good to go again.

 

If you mess with the throttle stop screw and then re-zero the TPS  thru the ECU, the motor will not have a proper mixture w/o carefully resetting that closed position. To that, many bikes come with those stop screws painted so they can't move. My '96 K11RS BMW and my Aprilia are examples. Change a Guzzi's throttle stop screws (also fixed with paint ), Well, I've read the throttle bodies would have to go back to the factory to get them set properly again.

 

If those plates were allowed to stay open, these motors would not really need an IAC( idle air control valve) - the FZ's sits right between the throttle bodies on the back of the motor) . Fast idle when the motor is cold would also have to be done thru some other mechanism as the IAC assists there as well.

The throttle stop screw means that when the throttle is closed, significant air gets by, so the plate is still very much open. The balance setting also allows air by, so there are two major pathways for air to get through even when "closed". The third is then the IAC which is most useful when cold, as you noted. I have worked on plenty of race motors that did not have an IAC or ETC, so they just idled a little higher when warm. Idle speed was controlled with spark, so EGTs limited idle speed when warmed up, and the throttle stops would be set such that it would idle cold fine. 

 

Even if the throttle stops allowed the blade to go to 0*, and even if there was no balancing bypass, air would still get by since there HAS to be slop for the blade to safely move. When that slop goes away due to buildup, you get a sticky throttle which is bad, so slop is necessary. That's why I say your post was inaccurate. 

 

As an aside, a perfectly blocked throttle can actually make for less engine braking, since there is reduced pump work since there is no intake air to even pump. BMW, for instance, deactivates the valve lift on one bank of their v motors when doing cylinder deactivation since it reduces pumping losses over just turning off the injectors and allowing air to pump through. 

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This is like asking someone "What's the best way to have your coffee?" 

Everyone has a personal preference. 

 

I do like the bike better with the ECU flash done and decel cut removed. This still provides a nice amount engine brake without crackin the family jewels!

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Rick, I too have a Subaru ( XV crosstrek). I have had the fuel shutoff flashed out on it as well. Makes the car so much easier to drive at low speed ( particularly off bitumen) and got rid of what I thought was clutch shudder. Now I just wish I could deactivate the engine stop at traffic lights. Twice been run into when the engine failed to start first time. Bloody dangerous. Both were just touches thankfully ( on my Towbar).

Go forth and modify my son...go forth and modify...

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"but in the cars I'll use engine braking to really influence handling at the limit."

Cars are different in that they have huge mass and gigantic tyre footprint to drive quite small piston areas ( in comparison). They rarely lock up and also ( except in unusual circumstances) rarley have sequential gearboxes that allow accidential overshifts. I agree in cars that engine braking is useful and serves more than one purpose.

Go forth and modify my son...go forth and modify...

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4 hours ago, gregjet said:

"but in the cars I'll use engine braking to really influence handling at the limit."

Cars are different in that they have huge mass and gigantic tyre footprint to drive quite small piston areas ( in comparison). They rarely lock up and also ( except in unusual circumstances) rarley have sequential gearboxes that allow accidential overshifts. I agree in cars that engine braking is useful and serves more than one purpose.

Having accidentally money-shifted an ariel atom once on track, an H pattern can definitely allow accidental overshift and lock the rear up, haha. But even in more normal situations like threshold braking, the tires will chirp and kick out without good rev-matching, but not as easily as on a bike for sure. The heaviest car I own though is still less than 3,000lbs, so I am definitely more biased to lightweight cars where engine braking is more prevalent, especially with the Elise. I took it out this afternoon after the FZ, and the engine braking is actually very similar - I can just about come to a stop in normal traffic with engine braking alone on both. 

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I've said it before, you can always just let the bike slow down and let the engine get down into lower rpm's before you downshift (rev match) and the engine braking won't be as bad. Edit: just brake first and when the revs are down then down shift. The bike isn't such a beast when you do it that way.

Beemer

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On 10/16/2017 at 3:43 PM, gregjet said:

Beemer, I think shaft drives are more prone to wheel hop because of the massive nonfloating extra unsprung weight of the shaft and housing. The CX500 used to do it to some extent as well, though Honda's slight reluctance to downshift easily and requiring a clutch action to get a good shift, helped mitigate it a bit. A small blessing in disguise.

BMW's engine speed clutches didn't help...

 

I do remember my bike feeling light in the rear. Almost every time I downshifted at high rpm in a lower gear like 2nd and just touched that rear brake it would go into a crazy hop.

Beemer

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8 hours ago, Beemer said:

I've said it before, you can always just let the bike slow down and let the engine get down into lower rpm's before you downshift (rev match) and the engine braking won't be as bad. 

Exactly what I do - just adjust my riding to the engine braking characteristics.

 

This bike does have high relatively levels of engine braking, the only time this is an issue is when you're first learning its character (just as with any bike).

 

I'm very comfortable with the engine braking but this will depend on how you ride. If you really want to reduce it it's good to know there are options out there.

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