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I've been using the regen braking paddles very actively for the past 2 months (since I bought my Insight). I use it when I am approaching to a full stop (traffic light, intersection) regardless if it's a downhill or not. And I will say it's helping with the mpg, not a lot but quiet enough to make you smile to see the difference!

However, I realized, if I am over certain speed like 50mph, and then try to apply the regen braking paddles, I hear a roaring sound from the engine, and it kinda makes me wonder why. If this paddles are only acting as brakes, why the engine struggles and makes the noise? Almost same noise as if you're trying to floor it after a full stop, anyone else experiencing this? Or am I not supposed to use paddles above certain speed?
 

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I realized, if I am over certain speed like 50mph, and then try to apply the regen braking paddles, I hear a roaring sound from the engine, and it kinda makes me wonder why. If this paddles are only acting as brakes, why the engine struggles and makes the noise? Almost same noise as if you're trying to floor it after a full stop, anyone else experiencing this? Or am I not supposed to use paddles above certain speed?
I've heard a sound like you described, though for me it was when accelerating while in a high-regen setting. I think the sound relates to the "engine-to-generator" transition happening as regen is added. To help the transition, I try to apply or release regen gradually at higher speeds.

The electric motor becomes a generator by running backwards as regen is applied. The level of regen (and paddle use) controls the degree of the motor being "generator" rather than engine. More regen means more "back-torque" applied in the reverse direction of the drive shaft, creating a net feeling of braking. It's really a complex set of transitions that are more technical than 'acting like brakes.'

It gets kind of technical, but the following are some video descriptions I've found, plus a simpler link/attachment with description of regen:
[0:21 - 2:23] Regen Braking1 - youtube.com/watch?v=BhOEoXfxHMc
[1:00 - 3:40] Induction Motor - youtube.com/watch?v=EWZkFX48vu0
[1:52 - 4:00] Regen Braking2 - youtube.com/watch?v=0b2i5ufN7k0
[see #4 - snapshot attached] autobytel.com/hybrid-cars/car-buying-guides/weird-noises-your-hybrid-makes-and-why-126954/
 

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I realized, if I am over certain speed like 50mph, and then try to apply the regen braking paddles, I hear a roaring sound from the engine, and it kinda makes me wonder why. If this paddles are only acting as brakes, why the engine struggles and makes the noise? Almost same noise as if you're trying to floor it after a full stop, anyone else experiencing this? Or am I not supposed to use paddles above certain speed?
The engine roar on deceleration occurs when the rate of charge is exceeded and the ICE needs to kick in (not using gas - just the clutch lock-up) to take the load off. This occurs during a very fast slowdown from high speed or when the battery is full and there's no place left to store the energy. At that point, engine braking kicks in. It's totally normal, but was scary the first time I had it happen! The engine isn't really struggling - it's helping you bleed off speed!
 

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I bought a 2007 Acura TSX used in 2010. The first time I was driving down a steep hill (on the middle and east of America you would call it a mountain) in the rain, it suddenly downshifted and the car started to skid. It happened more than once that winter and it was pretty scary. I was told there was some computerized system in it that decided that lower gear would be better. I guess that's similar to our regen braking kicking in.
 

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So I just did a trip from dc to Pittsburgh lastnight and the engine noise was let's say...less favorable. I had the car in sport mode mostly but that was because I enjoyed the immediate regen down hills. The strange thing was once the battery was full and I was going down a long hill without any throttle the engine freaking roared like I was engine braking down the hill the entire way. I thought that was so strange. I'm hoping on the way back Normal mode won't do that. I also like sport mode because it maintains a higher soc on the battery than normal or econ.

I'm wondering if some heavy duty sound dampening material on the engine firewall would reduce some of the low frequency noise...
 

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If your battery gets topped off, the Insight needs to put the regen energy somewhere, and that's through engine braking. It will get noticeably worse of the battery is topped off and you use the paddles to jack up regen - there's no place for it to go.
 

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So I just did a trip from dc to Pittsburgh lastnight and the engine noise was let's say...less favorable. I had the car in sport mode mostly but that was because I enjoyed the immediate regen down hills. The strange thing was once the battery was full and I was going down a long hill without any throttle the engine freaking roared like I was engine braking down the hill the entire way. I thought that was so strange. I'm hoping on the way back Normal mode won't do that. I also like sport mode because it maintains a higher soc on the battery than normal or econ.

I'm wondering if some heavy duty sound dampening material on the engine firewall would reduce some of the low frequency noise...
It was!! Hit the gas "feather foot will keep you in EV" and make a free mph run at the next hill !! :smile_big:
 

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So I just did a trip from dc to Pittsburgh last night and the engine noise was let's say...less favorable. I had the car in sport mode mostly but that was because I enjoyed the immediate regen down hills. The strange thing was once the battery was full and I was going down a long hill without any throttle the engine freaking roared like I was engine braking down the hill the entire way. I thought that was so strange. I'm hoping on the way back Normal mode won't do that. I also like sport mode because it maintains a higher soc on the battery than normal or econ.
As hasarad mentioned, it's kind of a pseudo-engine braking condition. I like and reference the explanation of it provided in a prior post - Engine Braking / Noise when HV Battery is Full. The electric motor is likely spinning the engine rather than consuming gas in this condition - Engine Noise Complaints

This is admittedly super geeky, but now owning a hybrid, I map out drives by terrain so I can avoid (or anticipate) where the engine would work hard and/or to pre-plan and optimize what modes to use when.

In terms your drive, the terrain from DC to Pittsburgh looks mostly uphill until a decline from Mt. Pleasant on. Sport mode maintained high SOC, and left little room for regen for the downhill stretch, triggering the high battery charge and engine/energy bleed-off. On next outbound trip, getting to a low battery level (turning off Sport?) before the downhill run would help maximize energy recovery (though the total decline looks steep enough that you'd max out battery charge anyhow).

Your return trip from Pittsburgh to DC looks mostly be downhill (after Somerset?), so Sport mode shouldn't be necessary since you'll naturally capture charge from the downhill stretches. Normal or EV mode will be better choices, to keep the battery level low enough to accept more/new charge.
 

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I was driving on the freeway and there was a downhill grade. I used my left paddle shift to slow down and regen. I noticed the battery level was pretty high and heard a high rpm from the engine, meaning it is also engine braking the vehicle.

My question is: Does the single speed transmission that engages at high speeds have variable ratios?

I read from many places saying that it is a single ratio direct connection. But then engine braking wouldn’t be possible.

Any thoughts? Thanks!
 

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I was driving on the freeway and there was a downhill grade. I used my left paddle shift to slow down and regen. I noticed the battery level was pretty high and heard a high rpm from the engine, meaning it is also engine braking the vehicle.

My question is: Does the single speed transmission that engages at high speeds have variable ratios?

I read from many places saying that it is a single ratio direct connection. But then engine braking wouldn’t be possible.

Any thoughts? Thanks!
The engine braking is from the main traction motor energy being dumped into the generator motor that will then use the engine as friction to electrically brake the traction motor. It's basically turning the engine into a resistor electrically. There's not transmission involved. The lockup clutch (direct engine clutch is only one ratio) essentially an overdrive gear - if you were to try using that to slow down the car it would never work.
 

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Thanks @Mobilcams that answers it!
What's interesting about it is in the morning when the engine and electrical system is not warmed up or ready, I have heard the engine braking when coming up to a stop sign at relatively low speeds. Pretty interesting way to bleed off excess power. I wonder how big of a resistor they would have to make to mimic the resistance the engine/battery offers.
 

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I've been using the regen braking paddles very actively for the past 2 months (since I bought my Insight). I use it when I am approaching to a full stop (traffic light, intersection) regardless if it's a downhill or not. And I will say it's helping with the mpg, not a lot but quiet enough to make you smile to see the difference!

However, I realized, if I am over certain speed like 50mph, and then try to apply the regen braking paddles, I hear a roaring sound from the engine, and it kinda makes me wonder why. If this paddles are only acting as brakes, why the engine struggles and makes the noise? Almost same noise as if you're trying to floor it after a full stop, anyone else experiencing this? Or am I not supposed to use paddles above certain speed?
Hopefully I'm not oversimplifying this too much, but if the battery is fully charged why would you try to force regen? It seems to me that you would just use the brake pedal to slow the car. Unless of course you are in a mountainous area where it would heat the brakes excessively, then I could see using engine braking to slow the car. Just my 2 cents worth.
 

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Hopefully I'm not oversimplifying this too much, but if the battery is fully charged why would you try to force regen? It seems to me that you would just use the brake pedal to slow the car. Unless of course you are in a mountainous area where it would heat the brakes excessively, then I could see using engine braking to slow the car. Just my 2 cents worth.
Welcome to the forum. There are a couple tricky parts that we can't manage once the HV battery is full:
1) the car's hybrid/charging algorithms - even after full, the charging algorithms still sends power to the HV battery.
2) initial travel of the brake pedal is regenerative - friction braking only kicks in at speeds of 10-15 mph and/or during emergency braking; even if you "think" you're using the brakes when the HV battery is full, you're actually still triggering regenerative energy to be sent to the HV battery
 

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Welcome to the forum. There are a couple tricky parts that we can't manage once the HV battery is full:
1) the car's hybrid/charging algorithms - even after full, the charging algorithms still sends power to the HV battery.
2) initial travel of the brake pedal is regenerative - friction braking only kicks in at speeds of 10-15 mph and/or during emergency braking; even if you "think" you're using the brakes when the HV battery is full, you're actually still triggering regenerative energy to be sent to the HV battery
Insightfully respectfully, I doubt that this is true.

1) The battery management system will not allow the batteries to receive a charge after they are full. This would cause permanent damage to them, possibly catastrophic. I sort of verified this with Eli at Bumblebee Battery when I was asking him about grid charging the 3rd Gen battery a while back. He said that they couldn't be charged without the BMS system active for fear of damaging the batteries, even at a trickle level (350ma). Lithium Ion batteries are not forgiving like the old 1st Gen NiMH which would happily accept a very low 350ma trickle to balance the individual cells.
So we can't force power into the batteries when they are full so we must be engaging the direct drive clutch to use engine braking in this situation.

2) "The initial travel of the brake pedal is regenerative." I agree with this part. There is a switch on the brake pedal just like the brake light switch that activates the regen. It is then controlled by the computers based on speed, battery charge level, ABS activity, and the left hand paddle switch input. This is very similar to the way the Gen 1 system works, only more elegant. Speculation from here. I doubt that the brakes are disabled when the brake pedal is pushed beyond the first 1/2 inch of travel (free play). I don't think that the NHTSA would allow any car on the road with "Brake by Wire" systems. The master cylinder is still attached to the brake pedal and works normally past the free play in the pedal. Regenerative braking only acts on the front wheels by design and could quickly become a safety issue. If you are indeed correct about no friction braking they must be using the ABS controller to block pressure to the front brakes.
 

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Speculation from here. I doubt that the brakes are disabled when the brake pedal is pushed beyond the first 1/2 inch of travel (free play). I don't think that the NHTSA would allow any car on the road with "Brake by Wire" systems. The master cylinder is still attached to the brake pedal and works normally past the free play in the pedal. Regenerative braking only acts on the front wheels by design and could quickly become a safety issue. If you are indeed correct about no friction braking they must be using the ABS controller to block pressure to the front brakes.
If helpful, @Mobilcams shared info on braking system operation, and some additional content on regen vs braking, and what we understand of the Insight's servo braking summarized separately.
 

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If helpful, @Mobilcams shared info on braking system operation, and some additional content on regen vs braking, and what we understand of the Insight's servo braking summarized separately.
It is def a good read.. The braking is actually controlled by a servo booster, with the master cylinder being piped to a pressure simulator (a spring/piston with a sensor in it). The computer uses this information to know how much regen/physical braking is needed or if emergency braking is needed.. The master cylinder is able to function normally in situations where the braking system is abnormal and you can feel this check sometimes when you start the car (the pedal moves a bit with a pop)... I know it's scary sounding, but it is safe or the NHTSA would not allow these systems.. You can look under the hood on the passenger side, you will see another "master" brake cylinder that has a servo system attached to it. This braking system is state of the art and pretty cool. Enjoy the tech!
 

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The master cylinder is still attached to the brake pedal and works normally past the free play in the pedal. Regenerative braking only acts on the front wheels by design and could quickly become a safety issue. If you are indeed correct about no friction braking they must be using the ABS controller to block pressure to the front brakes.
The system is smart enough to detect an emergency braking system and manipulate the brakes as needed. Believe me, I've had a few, and one of them - it hit the brakes harder and faster than I could have. We aren't talking about a dumb analog system. As for only braking on the front, in normal situations (coming to a stop light) that is all that is needed, normal car braking is tuned where 75% of braking is done with the front brakes.. If you are driving along on a curve and you start braking hard, the car has sensors that tell it the forces that are felt on the car and will activate brakes as needed.. Actually in our car, this braking can happen without pushing on the brakes in a high speed turn - it's part of Honda's Agile Handling Assist
 

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Here's a section from the 2019 Insight Press Release:

Electric Servo Brake System
Employing a microprocessor-controlled combination of electronic regenerative braking and hydraulic braking, Insight provides a smooth and linear braking response in all driving conditions, while also improving fuel efficiency.
The electric servo braking system is fully hydraulic from the master cylinder all the way to the 4-wheel disc brakes, just like a traditional braking system. The key difference is that the braking function is electronically controlled rather than a purely mechanical activation, allowing regenerative braking from the electric drive motor to slow the vehicle, rather than the hydraulic friction brakes under many circumstances. Besides its efficiency payoffs, the system offers excellent feel and feedback through the brake pedal.
When the driver applies the brake pedal, a signal is sent to the vehicle's Electronic Control Unit (ECU), which determines the appropriate amount of braking force to assign to regenerative braking through the electric drive motor and to the hydraulic friction braking system. In many light-to-moderate braking situations, friction braking is not needed until the vehicle speed drops below 5 mph, as the vehicle slows to a final stop. When the ECU determines that friction braking is needed, the dual hydraulic master cylinder pumps brake fluid through the system. Midway between the master cylinder and the calipers is a separate motorized electronic actuator. This actuator receives an electronic signal, generated in the master cylinder module that precisely defines how the driver has applied the brakes – soft or hard, slow or fast. The actuator then directly apportions hydraulic pressure to the brake calipers at each wheel. To maximize the Insight's accident-avoidance capabilities, the system delivers an extra-strong braking response when the driver increases the pedal force.
The 2019 Insight is equipped with 11.1-inch diameter ventilated front brake rotors (0.9-inch rotor thickness) clamped by single-piston brake calipers. The rear disc brakes incorporate 10.2-inch diameter solid rotors (0.4-inch rotor thickness) paired with single-piston brake calipers. The low-friction design of the brake calipers reduces energy losses when the brakes are not in use, directly improving fuel efficiency.
 

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1) The battery management system will not allow the batteries to receive a charge after they are full. This would cause permanent damage to them, possibly catastrophic. I sort of verified this with Eli at Bumblebee Battery when I was asking him about grid charging the 3rd Gen battery a while back. He said that they couldn't be charged without the BMS system active for fear of damaging the batteries, even at a trickle level (350ma). Lithium Ion batteries are not forgiving like the old 1st Gen NiMH which would happily accept a very low 350ma trickle to balance the individual cells.
So we can't force power into the batteries when they are full so we must be engaging the direct drive clutch to use engine braking in this situation.
I've been thinking about this one for a while... what I couldn't reconcile was that the HV battery level didn't drop (i.e. if charge stopped flowing to the HV battery, battery usage/depletion should occur pretty rapidly). But if direct drive engages once the HV battery is full, does hybrid/EV function disconnect entirely and just leaves the battery full for later?
 
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