Question about Engine Braking

[RCinNC]

Well, here's a weird one...has anyone ever felt like there was an increase in their engine braking while they owned their bike?

I have a 2014 S10, with a little over 32,000 miles on it. About a month ago I had the valve clearance check done, with no adjustments necessary. New plugs were installed at that point. The bike ran normally after the valve check.

Just recently I installed new brake pads on the rear, after running the pads all the way down to metal, and I replaced them with EBC pads. At first I thought the pads might have been dragging too much on the rotor, because it seemed like the bike was slowing down a lot faster than it used to when I would let off the throttle. I checked the rotor and caliper after a ride; the caliper wasn't hot at all, and the rotor was no warmer than usual. If I let off the throttle and pull in the clutch, the drag is really reduced, so I figured what I was feeling was engine braking and not drag on the rear brake. The thing is, the engine braking never felt that harsh in S mode, prior to when I changed the rear pads. In T mode, engine braking feels normal.

Has anyone here ever experienced an increase in the engine braking feeling? I can't imagine that anything I did when I changed the pads would result in that happening. I know that dragging pads would seem to be the obvious reason, but believe me, if I was dragging the rear pads on the rotor during an hour long ride hard enough to make the bike feel like it does now, that rotor should be hotter than a frying pan, and it's not.

I know it sounds crazy, but the engine braking definitely feels more harsh than it used to.

 

[klunsford]

My 2014 S10 feels like it has more engine brake in S mode than T mode. Of course on the acceleration side, it has more of that too. I think what you are feeling in the Torquey feeling of the engine in S mode. it decels harder and Accels more abruptly. I think it is normal.

 

[RCinNC]

Oh, i agree that the engine braking is common with the S10. What's weird is that is feels like it has increased in a very noticeable manner.

 

[VRODE]

I know my engine braking always felt harsh in S mode (hence the reflash). With your bike on the center stand,check for the brakes dragging front or rear. If they're not, it's probably normal.

 

[Pterodactyl]

Are you a drink'n man RC? Best explanation I can come up with.

The difference between T and S modes on my 2012 Tenere is noticeable, but nothing to crow about. I just leave it in T for the smoother throttle. Now on my 2013 FJR the difference between T and S is remarkable. I stay in S unless I'm in a low traction situation. In that case the T mode offers better throttle control.

 

[WJBertrand]

After flashing mine, the T mode shows stronger compression braking than S mode. I like the reduced engine braking in S mode as it helps smoothen the on/off throttle transitions in the twisty bits.


Sent from my iPhone using Tapatalk

 

[RCinNC]

I wish the answer was that simple, Pterodactyl.

Like I said, it's not the difference between S and T mode; it's that the feeling of engine braking in Sport mode is noticeably different now than it was before I changed the rear brake pads. I'm not suggesting for a second that the rear pads have anything to do with engine braking; only that I can pin the time the change occurred down to a specific time. I always ride in Sport mode; up until the other day, I hadn't used Touring mode in over a year. I was accustomed to the way the engine braking felt in Sport mode, and it now feels different. I know that there are O2 sensors that are part of the fuel mapping system, and I wondered if maybe a malfunctioning sensor had caused this, but diagnosing something like that (if it's even possible that could be a cause) is well above my pay grade.

I've been riding this bike since August 2014, for over 32,000 miles, and I'm pretty accustomed to how it rides and feels. There has been a noticeable change in how the engine braking feels.

 

[Sierra1]

You advised that the brakes were metal to metal? What's the chance that the brakes were lightly applied, reducing the " perceived" difference in engine braking. Now, with new pads, the feels like more engine braking. (I know what I am trying to say, not sure it came out right)

 

[RCinNC]

No, I totally get what you're saying, but i feel the difference when I let off the throttle, without applying the brakes.

I've even thought about pulling off the rear caliper, tying it to the bike, and sandwiching a piece of plywood between the pads so that when I activate the brakes, the rear brake won't even be on the rear rotor. At least that way I could remove the rear brake from the whole equation.

 

[Kurgan]

Did you take off the rear master cylinder cover before pushing the piston back in the caliper to fit the new pads? If not, that may be a contributing factor.

Also, I noticed that when I ran EBC HH pads on several different bikes, they all had more "drag". We measured overall width (backing plates and the brake pad material) and the EBC's were slightly thicker than stock or Galfer pads, causing a bit more drag until I was able to wear them down a bit. It was a pain in the ass, I pulled them and replaced them with Galfer, end of weird issues.

 

[RCinNC]

I didn't take the master cylinder reservoir cover off when I pushed the piston back into the caliper. After I changed the rear pads it felt like there was more drag on the rear brakes than there should be, and someone on another thread I started on the brakes pointed out the issue with the reservoir cover. I took it off then, and released a tiny bit of pressurized air.

I wondered about the thickness of the EBC pads. Up until this point I'd used OEM pads with no issues. When I put the EBC pads on, the brakes definitely had more drag. Took the caliper off, cleaned it thoroughly, and even extended the piston a bit so I could clean it up too. They seem to be seating in now, and the drag is reduced from what it was when I first changed the pads.

I think that if the brakes were dragging so bad that they were the cause of this new increased feeling of engine braking, then the rotor would be super hot and so would the caliper. If I'm just duckwalking the bike through my driveway, I don't feel any resistance from the brakes at all, so I really doubt that they are responsible for the increased feeling of drag I get when I let off the throttle.

 

[tomatocity]

I liked the stock engine braking of my 2012. Then I bought a 2015 ES and really like the stock engine braking. Now I can ride the west side of Berryessa ( https://goo.gl/maps/cqbqtEz6rMq ) ten miles an hour faster (50-55 mph) and not use brakes. The 2015 throttle is that much better than my 2012 throttle. All of this is in T mode. I am not good enough to ride in S mode.

Do I like the Tenere throttle... No. For me it is the worst part of the Tenere. Should I get the ECU remapped... Yes.

 

[Gobear]

From wikipedia

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.

Doesn't seem logical it could in anyway be caused by the rear brake ..IMHO

 

[RCinNC]

Doesn't seem logical it could in anyway be caused by the rear brake ..IMHO

I agree.

 

[2daMax]

One way to determine if it is not the brakes is to 'free' the gear or pull in the clutch when the bike is in motion and see if there are any difference. Pulling the clutch would remove the engine braking factor.

I did notice greater engine breaking after changing oil. Old oil was 9k km old and was probably sheared down in its viscosity. Compression has improved (better throttle response) with new oil and so is the engine braking.

I would recommend a throttle sync to remove it from the equation.

Other areas might be a clogged or increase restriction on the exhaust where the exhaust gases are struggling to get out. This will slow the pistons as it evacuates the gases on the Exhaust cycle. This would also mean that the bike would suffer on acceleration.

 

[RCinNC]

I've pulled the clutch in while allowing the bike to slow down just with engine braking; you can feel the resistance lessen when you do it, but that's to be expected. My S10 has always had a certain amount of engine braking. The brakes almost certainly are not at the bottom of whatever it is that seems to be causing this feeling of additional resistance.

Interesting, about the oil change. I'd forgotten I'd done that, about a week prior to changing the brake pads. However, I've always changed the oil every 4000 miles, and never experienced this in any of the approximately 8 or 9 oil changes I've done previously.

The bike accelerates normally. I can't say for sure about any clogs in the exhaust. The exhaust hasn't been damaged from any sort of crash, and I've never removed it for any reason. The bike is always parked in a rodent free garage, and it's never been submerged in anything like water or mud that might have gotten into the exhaust.

I haven't synched the throttle bodies for a while, but would that have anything to do with the symptoms I described? I can see the idle being rough with unsynchronized TB's, but I don't know how that would create the symptom I described.

 

[Dogdaze]

Hi RC, could it be just your heightened sense, because you had mechanical issue? I know that when something goes wrong on the bike (or anything) I start noticing other things, whether real or perceived, until I get 'use' to it and 'it' becomes the new normal. Not sure if that conveys what I'm trying to say.......

 

[RCinNC]

No, I get what you're saying, Dogdaze, and it's not that I haven't had those moments in the past with one bike or another where I thought "hmm, something doesn't seem right here" that ended up being nothing. This was a lot more pronounced than my usual odd sensation of a rattling sound, or a weird vibration.

If I don't hear from anyone on here who's ever experienced this and has an actual reason for it, I guess I'm just going to assume that I'm imagining it.

 

[Squibb]

Strange - reminds me of my wife's PHEV car when the regen braking is set on max.

Were the TBs re-synced after the valve check?

My thought was, maybe the TBs were just slightly out previously, which allowed one cylinder to have it's butterfly held open just a tiny tad on a closed throttle, so reducing the drag of the engine on the overrun. This would usually reveal itself with the odd stumble on the overrun & idle. Could be the TPS was out - I assume no codes were showing.

To my mind, with no loss of performance, the bike sounds perfectly normal. However, if it were mine, I would just check out the throttle cable action/free play at the grip (both opening & closing), making sure they operate freely, are not pinched anywhere on their run & are located correctly both ends. I have known a taut closing cable on my old KTM to produce a strange feel, including an over-aggresive shut down, but that did have a QA cam on the twist grip barrel . Then I would re-check the TBs just to be sure.

Peace of mind is always nice & it would not be very time consuming just to double check.

Ride Safe ..................... KEN

 

[RCinNC]

No TB synch was done during the valve check. If I recall, I did the last one myself at around 18,000 miles. Nothing about the way the bike was running would have led me to think the throttle bodies weren't in synch, but I will go check it just to make sure.