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What Exactly Causes the Jake Brake on Decel Sound? (with side pipes open)

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I just put 3/4 baffles in my pipes (after running none for 6 months). The burble is still there and prominent. That being said, it reminds me of the Cobra rep with a 351W and sidepipes I drove last summer, and that's why I love it!
 
four-walling said:
Sounds like we are talking about 2 different issues here?

One is the annoying jake brake ( big rig diesel truck) sound the Boss makes using engine braking on a big downhill.

The other sound is the wonderful snap, crackle and pop of a quick downshift to a stop.

Yes, you're right. I love the popping sounds. I don't like the jake brake sound. It was the semi-truck-like jake brake sound I was originally asking about.
 
aircare84 said:
The only way I've found to reduce it, it to limit the side pipes opening. I tried running the side pipes with the baffles removed, & also did not care for the 'Jake Brake' sound on decal. Went with 3/4" side pipe baffles & found a good balance.
Have to just adjust your cutouts to a tone you want.

I'd need to open them each time I accelerate and close them down each time I downshift to decelerate. I suppose I could do that but it would get a little tedious. ::)
 
After reading up on how a Jake brake actually works, it seems like a logically conclusion that all modern engines will work like that to decelerate when fuel is cut. Especially with engines that can rapidly change valve timing while cutting fuel to effectively do the same thing a Jake brake does. Add our already loud exhaust and just enjoy the noise! Plus we know the track key increases engine braking. I bet this is how. But for the track I would rather have the air pumping in and right out to cool down the engine a bit while braking. Compressing air creates a lot of heat when you could be cooling instead.
 

four-walling

Kerry, San Diego
302BOB said:
Maybe a Tesla....no jake brake noise there.. ;D

They have their own noise issues:

(from: Seeking Alpha)
http://seekingalpha.com/article/2225563-increasing-hum-poses-problems-for-tesla?uprof=46

Increasing Hum Poses Problems For Tesla

The Advantage of the EV

Although Tesla (TSLA) owners like to brag about saving money on gas, the reality of the Model S that makes it exceptional is its acceleration and regenerative braking. The ability of the car to instantly jump when you hit the accelerator pedal and the ease of driving with regenerative braking is what the drivers love. In order for this to happen, full available power must be applied to the drive inverter instantly. The acceleration occurs and as you reach your new desired speed, the inverter output is adjusted to maintain the new speed and you go on your way.

The Problem: On some cars, however, as your speed levels out, you hear a hum as if there is a truck passing you. This hum remains as you drive in the 65-85 mph range. Owners have reported it starting as low as 44 mph. It seems to come with age.

The Answer: The answer is probably the one engineers call "Closing the Loop," and on the Model S, this might be the problem.

What is the Loop?

The Loop, or feedback loop, is the means of maintaining a device's output by comparing it to a known reference and keeping it at a desired output based on this reference. If the loop speed is too fast, it can overshoot, and then undershoot when trying to recover, causing an oscillation.

In an Internal Combustion Engine (ICE) vehicle, when you step on the gas there is a delay before the ICE can accelerate. The car accelerates from 55-65 mph; at 65, you back off the gas and maintain a steady 65. In this case, you closed the loop when you backed slowly off the gas; your feedback reference was provided by the speedometer and your foot action.

Suppose Tesla did the same thing. You hit the accelerator, and suddenly, you are at 70 mph before you can take your foot off. You take your foot off and you drop to 60; foot back on - bingo, back to 68 - you keep bouncing or oscillating. Tesla realizes this problem and adjusts the response time of the inverter to correct for it, yet it wants to maintain the "instant acceleration" thrill, so it still tries to keep it as fast as possible. It probably does this by closing the loop itself based on the position of the accelerator pedal. As an example, if the accelerator pedal produced a voltage that would vary between 0 and 10 volts and the speedometer provided a voltage of 0-10 volts corresponding to 0-100 mph, a control circuit to the inverter could maintain any speed depending upon the accelerator pedal's position.

Loop Description:

The accelerator pedal is pressed down to a 60 mph level, the inverter turns on full power, the three phase induction motor roars to life, and as the car approaches 60 mph, the inverter output backs off and the car settles at a steady 60 mph.

What happens after tens of thousand of miles and the bearings are a bit tight slowing the ability of the motor's response, just enough that the error signal overreacts and the speed overshoots slightly. It then begins a slow speed oscillation at a low frequency, which creates a hum.

This description is my own guess based upon reading the tales of woe on the Tesla 65-75 mph hum problems and spending a lifetime stabilizing power circuits with bode plots.

Conclusion: Closing the loop in a complete electronic circuit is relatively easy to do because the component values never change. When you add a three-phase inverter and induction motor and a 5000 lb. car to the loop, response times will vary with age and torque settings, etc. If what is described is the case, Tesla will probably have to slow the response time in future designs. If the problem requires changing bearings or motor mounts, Tesla might face another recall on all its cars, as the hum problem seems to come with age and miles driven. This problem could also haunt the Model X with four-wheel drive.
 
I love the decel snaps/pops, but if my dad was around today he'd tell me that brake pads are cheaper/easier than new rings. :p But it's addicting like driving with the red key. I must have it when I drive...lol.
 
four-walling said:
They have their own noise issues:

(from: Seeking Alpha)
http://seekingalpha.com/article/2225563-increasing-hum-poses-problems-for-tesla?uprof=46

Increasing Hum Poses Problems For Tesla

The Advantage of the EV

Although Tesla (TSLA) owners like to brag about saving money on gas, the reality of the Model S that makes it exceptional is its acceleration and regenerative braking. The ability of the car to instantly jump when you hit the accelerator pedal and the ease of driving with regenerative braking is what the drivers love. In order for this to happen, full available power must be applied to the drive inverter instantly. The acceleration occurs and as you reach your new desired speed, the inverter output is adjusted to maintain the new speed and you go on your way.

The Problem: On some cars, however, as your speed levels out, you hear a hum as if there is a truck passing you. This hum remains as you drive in the 65-85 mph range. Owners have reported it starting as low as 44 mph. It seems to come with age.

The Answer: The answer is probably the one engineers call "Closing the Loop," and on the Model S, this might be the problem.

What is the Loop?

The Loop, or feedback loop, is the means of maintaining a device's output by comparing it to a known reference and keeping it at a desired output based on this reference. If the loop speed is too fast, it can overshoot, and then undershoot when trying to recover, causing an oscillation.

In an Internal Combustion Engine (ICE) vehicle, when you step on the gas there is a delay before the ICE can accelerate. The car accelerates from 55-65 mph; at 65, you back off the gas and maintain a steady 65. In this case, you closed the loop when you backed slowly off the gas; your feedback reference was provided by the speedometer and your foot action.

Suppose Tesla did the same thing. You hit the accelerator, and suddenly, you are at 70 mph before you can take your foot off. You take your foot off and you drop to 60; foot back on - bingo, back to 68 - you keep bouncing or oscillating. Tesla realizes this problem and adjusts the response time of the inverter to correct for it, yet it wants to maintain the "instant acceleration" thrill, so it still tries to keep it as fast as possible. It probably does this by closing the loop itself based on the position of the accelerator pedal. As an example, if the accelerator pedal produced a voltage that would vary between 0 and 10 volts and the speedometer provided a voltage of 0-10 volts corresponding to 0-100 mph, a control circuit to the inverter could maintain any speed depending upon the accelerator pedal's position.

Loop Description:

The accelerator pedal is pressed down to a 60 mph level, the inverter turns on full power, the three phase induction motor roars to life, and as the car approaches 60 mph, the inverter output backs off and the car settles at a steady 60 mph.

What happens after tens of thousand of miles and the bearings are a bit tight slowing the ability of the motor's response, just enough that the error signal overreacts and the speed overshoots slightly. It then begins a slow speed oscillation at a low frequency, which creates a hum.

This description is my own guess based upon reading the tales of woe on the Tesla 65-75 mph hum problems and spending a lifetime stabilizing power circuits with bode plots.

Conclusion: Closing the loop in a complete electronic circuit is relatively easy to do because the component values never change. When you add a three-phase inverter and induction motor and a 5000 lb. car to the loop, response times will vary with age and torque settings, etc. If what is described is the case, Tesla will probably have to slow the response time in future designs. If the problem requires changing bearings or motor mounts, Tesla might face another recall on all its cars, as the hum problem seems to come with age and miles driven. This problem could also haunt the Model X with four-wheel drive.

If Tesla is having problems tuning their PID loops for their motor control they need to hire some real electrical engineers.... A properly designed motor controller won't have oscillation issues.
 
Forget it folks, getting a different car ain't gonna happen and getting rid of the side pipes ain't gonna happen either! :mad:

Practically everyone here mods their car in small or large ways. That doesn't mean they don't like the car. I love my Boss and may just have it until the day I die.
 

Domestic Product

Big fat tires and everything !
Gotta go with the I like it camp. What other factory car sounds like this ? (with disks out and track key in especially )
My solution when driving down the big hill from my house right by the Sheriffs house :mad: is to put it in 4th or 5th gear at 25mph and use the brakes. He still stares at me as the track pads squeal past his house down the hill.
Lets face it you are not sneaking up or away from anybody in the Boss sound wise. It is a loud car. But to each his own. I think if you get rid of the jake brake sound you will also loose the snap, crack and pop of the car. They go together I think.
 
95
0
My boss has a ORX, deleted resonators, and slp loudmouths (muffler deletes) I like the jake brake sound but sometimes it gets annoying when trying to be quiet cuz it'll actually get louder when slowing down than it is in throttle.


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