https://vatire.com/car-maintenance-t...ngine-braking/
Assuming this is the complete article you posted snips of??
The true subject of the article is how engine braking can help reduce brake component wear.
I don't have a dog in this debate, but I'm skeptical of screen shots of articles.
2011 Camaro 2SS Convertible L99 Bone Stock for now
2003 Dodge 2500 5.9 Cummins QC 4x4. Airaid, 2nd Gen Intake, Grid Heater Delete, D-Tech 62/65/12, Magnaflow. Bully Dog: Propane Injection, Triple Dog W/Outlook Crazy Larry. Edge EZ, BD Flow-Max, 48RE: Sonnax Sure Cure/Transgo combination, Derale turbulator, billet input, Triple Disc, Super servo, 4 ring Accumulator. :beer
I think you just don't like to admit defeat. Cmon show me some math already heres mine
Clearly a huge advantage to coast in gear (engine braking) than stop suddenly and waste all the energy with brakes.
I'm confused where all your recovered energy gets stored at...Originally Posted by kingtal0n
We aren't storing it, thats why its called BRAKING. WHen you BRAKE with normal brakes the energy turns to HEAT.
WHen you BRAKE with the engine, the energy is used to maintain the angular momentum of the engine.
One way turns it to heat, WASTED. The other way RECOVERS IT by making up for the fact no fuel is going into the engine.
Now you're getting it. Any force that resists you on your way to your destination reduces fuel economy.... Any. Force.
Ah, the way I work is this. First, I conceptualize the ideology for many years. In this case, 20 years or so, I've known about engine braking. All cars use engine braking to my knowledge. Every single vehicle I've ever tuned shuts down it's fuel injectors to conserve fuel during a deceleration in gear, where applicable.
Then, I take that experience and combine with mechanical engineering mathematics. In this case, kinetic and momentum energy which is invested into drivetrain parts via fuel input. Fuel turns to energy, gets parts moving. Its... pretty basic.
Then, we get here, and there seems to be a need for additional supplemental materials. So I go out and find articles, videos, papers, published documents, whatever. Anything and everything for critical evaluation.
So, those links and pictures and crap I post, isn't what I base my opinion or research or idea on. It has nothing to do with what I am saying other than the fact it supports my arguments.
In other words, I don't ever make ANY argument using online materials. I am also highly skeptical of those resources. Even published research is often sketchy and needs a careful criticism. Thus, when I make any assertions, it is from my own personal mathematical and experience that I derive those theory and ideas, not something I READ on the internet (LOL).
If you have to stop for a stoplight there is no choice. I think you are considering a constant speed condition which is impossible to maintain from stoplight to stoplight.
You are acting like nobody ever uses their normal brakes. Thats just crazy, everybody has to brake eventually. That turns energy to HEAT. Better that is doesn't turn to heat. Its as simple as that. I never "got" anything its just common knowledge as an engineer or scientist or whatever.
I'm sure we'd all love to remove our brakes and just go 1 constant speed everywhere rofl
great discussion. Smokeshow lives in a place where nobody uses their brakes and never has to stop. You just, roll out of the car while its still moving? Who parks it- wait. How do you park a car without stopping it? Thats a good one, smoke.
I recommend not making claims that are dead wrong. If you don't want to get called on it. Engine braking does not give you anything back. I know because I had to mitigate precisely that excessive engine braking to fix a fuel economy problem for an OEM
There is nothing wrong with avoiding the use of brakes by slowing a vehicle down using engine braking. Energy can turn to HEAT using normal brakes, Or it can turn into rotating force, you choose whether to step on the brake pedal or use the engine to slow you down. One or the other. Turning to heat is wasteful. Never use your normal brakes. Only use the engine to brake the vehicle. It is far superior. You didn't call shit sorry.
Matlab model for jakebrake- compression engine braking to avoid using friction braking system.
https://www.mathworks.com/help/physm...e-braking.html
https://www.researchgate.net/publica...DIESEL_ENGINES
Auxiliary braking systems, which include also the Jake brake system, have a decisive role in issues such as road safety and optimization of fuel consumption.
They went through a *LOT* Of trouble to get this engine brake thing working for diesel applications.It was developed
by Cummins in the `60s and presented in [1] as a result of increased braking efficiency achieved by transforming
the engine into a huge compressor.
https://www.roadandtrack.com/car-cul...than-coasting/Leaving the car in gear can actually use a lot less fuel than leaving it in neutral, since the computers need to inject fuel to keep it running in neutral, but not when the engine is spinning while the engine is braking.
This shit is all over the internet. Its really obvious too.
https://brakeexperts.com/why-does-braking-use-fuel/So why does braking use fuel? It’s the way you brake, rather than braking itself. Continuously slamming the brakes causes less fuel efficiency as the car works harder to accelerate, so taking it slow and easing to a stop or using engine braking is a better solution to saving fuel.
Common sense
https://www.jstor.org/stable/4461120...LpsvT15L&seq=1
Ya don't say!In order to enhance the overall economy....
Okay I'm bored. People can use their normal brakes to slow down which turns energy to heat, all is lost.
*Or* we can use engine braking to slow down the vehicle which cuts fuel to the engine, saving fuel, while maintaining the engine rotation to keep it from stalling due to no fuel going in. This way you can slow down and recover some energy that was spent from fuel earlier.
Its common knowledge. Believe what you want
I'm confused as to what point you are constructing your counterpoint against lol. Nobody ever said to drive around two footing the pedals so you can have your mind blown by the fact that not doing that conserves fuel. You're right, coasting to a stop (ideally with a calibration that minimizes engine braking) is better on the fuel mileage than smashing on the brakes immediately after letting off the throttle. That said...I can calibrate an engine to plant your face into the steering wheel with engine braking by choking the engine with a throttle snapped completely shut. The effect is the same as mashing on the brakes. It is momentum lost and therefore wasted energy. To address your curiosity in post #5...this is precisely why GM and any other manufacturer of ICE engine passenger vehicles aims to reduce engine braking. They don't decel hard enough to choke you on the seat belt for a reason. The net effect is the same as hitting the brake pedal. So again, to your original point in this thread in the comment below...engine braking does NOT recover ANY energy. The ideal situation would be none at all, but a balanced set of requirements must be met. So every vehicle will have some amount of natural engine braking. It's not doing your gas gauge any favors though. Less is more here...that's just classical mechanics.
I sort of think the two of you are maybe not comparing the exact same things. Kingtal0n maybe correct in particular circumstances such as using engine braking when descending a hill but not coming to a stop might be more efficient using engine compression as a spring to store some energy. Smokeshow is more than likely talking more about all around driving and taking into account different driving habits across many conditions.
But what do I know, look at my post count. But I have seen gmtech16450yz talk about the ecotec platform getting better mileage by increasing cam overlap to decrease pumping losses when in cruise loading.
Its pretty basic engineering. Disc brakes turn kinetic energy and momentum into heat- wasted energy. Never use your brakes if you wish to conserve fuel.
Engine braking turns kinetic energy and momentum into WORK at the crankshaft, inputs energy to the engine while reducing the energy of the vehicle and it's rotating parts to help slow you down.
Engine braking is an essential component of fuel economy and to reduce brake wear.
I think he just wants to sound smart on the internet. Smoke resorts to name calling and insults. He fails to use engineering terminology such as kinetic energy. He fails to provide mathematical reasoning. I do not think he is really an engineer.
Of course you could shut off all fuel but maybe a little is beneficial to the cooling of the rings and valve lands if you were just WOT the moment before? I saw an advertisement from Chevy about the wonderful new 2.7 L turbo Silverado and the fact that it will turn itself off while you sit waiting for the traffic lights to turn. I can’t wait to see the average life span that engine will have before it is turned to junk by such nonsense. Clearly better planning is needed for good fuel economy. Why don’t we all just put a nice single cylinder motorcycle engine in the trunk that we normally use to get here and there and then start up our V8s for the times we want to have fun or tow something? I must be losing it.
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--- What am I doing??? Why did I do that???---
DFCO does absolutely give you back something. My Express van on a long downhill coast will actually accelerate to the point of having to downshift to 3rd or step on the brakes. I have seen it in DFCO for 2-5 miles coasting down a long grade that was not even that steep. GM 4spd Automatics have an over run clutch anyway that allows them to coast. Your Dodge example does not apply well to modern GMs because engine braking in overdrive is already very limited and what little there is limits the engine RPM drastically so you are not losing much however ZERO fuel is flowing. With my travel trailer behind me I often have to put it in 2nd at highway speeds to get enough engine braking to prevent 12,500 lbs from wanting to accelerate to 80+ MPH. So regardless what you learned tuning some 4 banger box of a Jeep does not equally apply to some GM vehicles. The energy you used climbing a grade in your vehicle is stored in the height it has gained and the weight, coasting downhill the energy is returned. Pretty simple physics. You can either burn the brakes up with heat engine on coasting or engine brake with zero fuel flow. Even with modern grade braking the fast lane truck guys have seen as many as 12 brake applications in the 7 miles or so they travel coming down the Eisenhower.I recommend not making claims that are dead wrong. If you don't want to get called on it. Engine braking does not give you anything back. I know because I had to mitigate precisely that excessive engine braking to fix a fuel economy problem for an OEM
Last edited by Fast4.7; 01-07-2023 at 06:58 PM.
You will not smash your face in a GM, the over running clutch when it is in overdrive prevents that. You will have to pull it down a gear so that the over run clutch applies hydraulically before you get engine braking like that.
I will also throw in something I forgot to mention earlier. EVERY vehicle I have driven in the past 10 years is tuned insanely horrible for coasting to a stop or slowing down. The OEM CALIBRATORS are making them act as if the cruise control is engaged. They should all be FIRED for it IMO. The way I set the vehicles up that I tune, you could drive though whole states and not have to smash on the service brakes a single time, unless you need to come to a complete stop, had a sudden traffic signal change or a car pulled out in front of you at the last second. In city driving I actually hold the vehicles out of overdrive as well, more engine braking and the torque converter will lockup sooner. If you know how to drive, the fuel mileage is better having noticeable engine braking with the throttle at 0%. The brake pads in these newer cars and trucks do not last well either. Those of us that leave room in front of us to allow for off-throttle coasting rather than standing on the brakes and can modulate the gas pedal short of a OFF/ON light switch get better mileage with a vehicle that enters DFCO and actually slows down. On the P01/P59 GMs one of the first things I do is HALF the Throttle Cracker airflow. On Nissans I set the Throttle mapping to higher negative torque numbers with throttle off. This prevents them from having a cruise control feel when I am off throttle. My city mileage increases noticeably as much as 2-3 mpg when I do this and both the intensity and number of brake applications I have to make are reduced dramatically. It is really easy to know why this happens too. My foot is on the pedal with light changes of throttle to control speed and distance, I can actually accelerate, coast or slow down merely moving my right foot. It is a far more efficient way to control a vehicle and saves wear and tear on the brake pads and rotors. I got 100K out of the last set of pads on my 2007 G35 and that was driving mostly around Dallas-Fort Worth. Once I remapped the throttle in that car it became a joy to drive even in heavy traffic. At high speeds it will even downshift to 4th gear off throttle to meet the negative torque value drive force which starts slowing the car before you can even get your foot from the throttle to the brake pedal.
FOR ANY OEM READING THIS, if I wanted cruise control when I let off the throttle, I would have the cruise control set!
Last edited by Fast4.7; 01-07-2023 at 06:08 PM.
Not when you are actually intentionally trying to slow down completely off throttle. When I am coasting, 100% off the throttle, ZERO TPS value, and the engine is still running not providing engine braking, you are reducing my fuel mileage and forcing me to make a brake application that did not otherwise need to be made. It is guys like you with you flawed logic that have created the stupidly calibrated modern vehicles we have today. If my foot is completely off the throttle my intention is to slow down, not have cruise control at X MPH I was traveling at prior to letting my foot off the throttle. At say 30 mph a vehicle should slow down to idle creep speed in no more distance than if would if it were engine off coasting and in all respect I prefer it to shut down in 1/2 that distance of just coasting, it just makes sense. I see a redlight a block ahead, I let off the throttle and the vehicle slows down rather than continuing to motor along. If I am traveling at 30 mph and want to continue traveling 30 mph, my foot would be on the throttle at whatever TPS position the powertrain requires to move the vehicle along at 30 mph. DFCO and ENGINE BRAKING are my MAIN braking force in normal driving in a PROPERLY calibrated vehicle. I seldom use the service brakes in a properly calibrated vehicle even in city or stop and go traffic.
Last edited by Fast4.7; 01-07-2023 at 06:30 PM.
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