Grandma can't shift in .099 milliseconds!

[carracerptp]

I can't believe what I am reading. This is rolling way out of topic, but I have to correct this anyway. Honestly without any offence, anyone that believes that engine braking doesn't have an effect in braking is wrong. If it had not no racing driver would ever blip that throttle while downshifting.

The purpose for engine braking is for the motor to resist the circulating movement of the differential thus avoiding rear wheels to lock and shorten the braking distance also somewhat.

I am not saying that revving the life out of the engine is needed or worthy, just that some engine braking is needed for any modern or ancient race car. Otherwise no driver would ever go down all the gears.

The same effect can be used with a normal road going vehicle,
even while it is not particially usefull, though the effect is lessened somewhat.

We are not saying "engine braking" doesn't slow the car down (drop to 1st in any car and it will lock up the rears), it's just not "needed" in a race car or any modern car to stop/slowdown a car. The real brakes are more powerful.

 

[Johnnypenso]

Yes but in racing the car will take a greater amount of length to stop without engine braking (blipping the throttle ahile downshifting).

RattijuoppoFIN

Can you do some testing and show this is the case?

We are not saying "engine braking" doesn't slow the car down (drop to 1st in any car and it will lock up the rears), it's just not "needed" in a race car or any modern car to stop/slowdown a car. The real brakes are more powerful.

Agreed. There is no brake fade in GT and thus no need to use an engine braking effect to help slow the car because the brakes never deteriorate.

 

[eran0004]

I can't believe what I am reading. This is rolling way out of topic, but I have to correct this anyway. Honestly without any offence, anyone that believes that engine braking doesn't have an effect in braking is wrong. If it had not no racing driver would ever blip that throttle while downshifting.

The purpose for engine braking is for the motor to resist the circulating movement of the differential thus avoiding rear wheels to lock and shorten the braking distance also somewhat.

I am not saying that revving the life out of the engine is needed or worthy, just that some engine braking is needed for any modern or ancient race car. Otherwise no driver would ever go down all the gears.

The same effect can be used with a normal road going vehicle,
even while it is not particially usefull, though the effect is lessened somewhat.

Alright, it seems like there's a misunderstanding because of the terms involved. What you're describing is actually throttle blipping, not engine braking. Throttle blipping is a way to match the revs of the engine to the speed of your car while downshifting, in order to avoid the tires to slip during the time it takes for the engine to go from the low rpm of a higher gear to the high rpm of a lower gear. Braking would be improved because it would prevent the tires from locking up. Right? This technique is very useful in racing.

Engine braking is when you use the retarding forces of the engine to slow the car down, by using kinetic energy from the driving wheels to revolve the engine. As the throttle is closed, the air flow is restricted and for the engine to revolve it has to transport a lot of air through very tiny holes - like breathing through a straw. This takes a lot of energy and is effectively applying rolling resistance to the drive wheels. The higher the rpm, the more work the engine needs to do and the greater the retarding force will be. This technique is not very useful in racing, unless your brakes are gone (and at that point it would just serve the purpose of letting your car come to a halt in a somewhat controllable manner).

 

[niky]

We do roughly two to three hundred braking tests every year. On a street car, even with the gnarliest rubber, engine braking, even when done by an experienced racer (I couldn't heel-and-toe that fast to save my life) will not make a car brake to a complete stop any faster. Worse yet, it's a distraction in an emergency situation, where you should be focused on braking as hard as possible and steering out of trouble.

It has other benefits... adjusting the trim of the car, keeping the car attitude steady under braking through a corner... (though one instructor asks us to do all our shifting near the end of the braking period, not from the start) but you don't need the engine to slow down the car, not as long as the brakes work properly.

And without brake fade in Gran Turismo, the brakes always work properly.

(drop to 1st in any car and it will lock up the rears)

Right before you blow the engine.

 

[R.S]

Race drivers rev match so the clutch will engage asap, they could need power at any moment and there is no use to have the clutch slipping (and wearing) while the engine is being brought to speed.

Using engine braking does not increase traction of tires and modern brakes are plenty capable of out-gripping the tires on a car. Brakes are more predictable and controllable than engine braking.

Trucks use engine brakes because they carry shiploads of weight and travel thousands and thousands of miles, including down long grades on highways, saving costs on replacing brakes.

 

[RattijuoppoFIN]

Can you do some testing and show this is the case?

Agreed. There is no brake fade in GT and thus no need to use an engine braking effect to help slow the car because the brakes never deteriorate.

This is not something that you can test in a game iRacing or not. I do not have access to a race car. But if you say that engine braking is not needed nor used in race cars you have no idea what you are saying.

Yes you can stop a race car without it and the brakes go through most of the work, but the length of the braking period would be increased therefore all the drivers use it. That is why you can hear the car going back through gears. Otherwise they would just go i.e. from 5th to 3rd.

RattijuoppoFIN

 

[fifomaniak]

No. Drivers use engine braking it to get some load off the brakes, so they don't overheat and they don't wear too quickly. That's why they're downshifting during braking, also to be ready to accelerate in any given moment.

If the engine braking would be necessary, drivers would always lock up the drive wheels (in most cases rear), yet almost always lockups happen in front wheels only. That's because brakes are strong enough to lockup the wheels anyway.

 

[niky]

but the length of the braking period would be increased

Again... no it won't.

Again... testing brakes is one of my jobs. I've done more full-bore, 1g plus emergency stops than you'll do in your lifetime. Or several.

Under full braking power, the contribution of engine braking is less than the random noise inherent in a braking test.

We do tests in sets of three to four, and sometimes experiment with aggressive engine braking, and it never makes for shorter stopping distances.

Never.

Perhaps if we were still driving around cars with unboosted four-wheel drum brakes, maybe... but nowadays? No.

-

Of course, if you want a longer answer, refer to here:
https://www.gtplanet.net/forum/showthread.php?p=6193870#post6193870

My response to the exact same question two years ago.

 

[carracerptp]

Yes you can stop a race car without it and the brakes go through most of the work, but the length of the braking period would be increased therefore all the drivers use it. That is why you can hear the car going back through gears. Otherwise they would just go i.e. from 5th to 3rd.

RattijuoppoFIN

Car A will be using disk brakes all around, stopping with the clutch in so the engine is disengaged so that the engine braking will not affect it. Car B will use the brakes and engine braking.

Both cars will do a "panic stop" with ABS off.

Car A is driving along, slams the brakes, locks all four wheels up, skids to a stop.

Car B is driving along, slams on the brakes (locks up all four tires), skips down two gears, all four tires are still locked up, skids to a stop.

Both cars locked up all four tires so they're stopping at the same point in time. They both have the same stopping potential. The only difference being one guy down-shifted two gears. If the brakes can overpower the tires' grip, then it is pointless to add more stopping power. It won't make you stop faster. The only thing that could make you stop faster is better tires.

The reason people synchronize downshifts is so they can stay on the powerband, not jar the drivetrain, and it's easier on the components (if done right).

Another reason you don't want to use engine braking as any significant form of slowing down is it causes a rear brake bias in a rear-wheel drive car (the majority of racecars). Most brake biases have less brake in the rear than in the front. Stability under braking is significantly improved by having the front wheels do the work (unless you're driving a DeltaWing).

So, to reiterate, if your brakes can exceed the maximum grip of the tires, you don't need anymore braking power. You're already over the maximum.

 

[Screbz]

I'm sorry but do you guys mean "breaking" as in malfunctioning, or "braking" as in slow down? I can't tell, maybe it's a combination of the two but it's hard to follow this thread.

 

[Brunol]

This is not something that you can test in a game iRacing or not. I do not have access to a race car. But if you say that engine braking is not needed nor used in race cars you have no idea what you are saying.

Yes you can stop a race car without it and the brakes go through most of the work, but the length of the braking period would be increased therefore all the drivers use it. That is why you can hear the car going back through gears. Otherwise they would just go i.e. from 5th to 3rd.

RattijuoppoFIN

Go search on youtube and you'll see many racing drivers skipping gears on downshifts, like from 5th to 3rd. Jackie Stewart did it a lot. It doesn't happen that frequently anymore because most of the racing cars have sequential 'boxes.

And it doesn't have anything to do with stopping power...

 

[eran0004]

Again, it's throttle blipping (or rev matching), not engine braking.

Throttle blipping is used to prevent the drive wheels from locking up when shifting down. If your wheels lock you're obviously going to have a longer braking distance, or possibly spin out of control. That is why a race car driver would blip the throttle during downshift. It doesn't add extra braking force, it simply prevents you from losing braking force (and control).

Engine braking is something else, and I think you may have got the terms mixed up.

 

[Scaff]

Engine braking should be the kind of thing that gives aggressively braking
drivers an advantage when deaccelerating.

RattijuoppoFIN

Engine braking is not a technique that should be used on the track and unless your brakes are incapable of exceeding the grip limit of the tyres (and every modern car has brakes that are and all cars in GT5 are) then its not going to slow you down any quicker at all.

Its actually more likely to lock up the tyres and if the cars rear wheel drive also cause control issues.

https://www.gtplanet.net/forum/showpost.php?p=1785601&postcount=361

I can't believe what I am reading. This is rolling way out of topic, but I have to correct this anyway. Honestly without any offence, anyone that believes that engine braking doesn't have an effect in braking is wrong. If it had not no racing driver would ever blip that throttle while downshifting.

That's not engine braking, that's a heel and toe throttle blip, which is done specifically to avoid engine braking!

The purpose for engine braking is for the motor to resist the circulating movement of the differential thus avoiding rear wheels to lock and shorten the braking distance also somewhat.

That's still not engine braking

The same effect can be used with a normal road going vehicle,
even while it is not particially usefull, though the effect is lessened somewhat.

Its quite useful in spirited driving and I do it everyday, its effect is also not lessened as you vary the amount you rev match to the situation, its not a one size fits all process.

This is not something that you can test in a game iRacing or not. I do not have access to a race car. But if you say that engine braking is not needed nor used in race cars you have no idea what you are saying.

Once again your not describing engine braking, and I can assure you that Niky and myself have more than enough experience to know exactly what we are talking about.

Yes you can stop a race car without it and the brakes go through most of the work, but the length of the braking period would be increased therefore all the drivers use it. That is why you can hear the car going back through gears. Otherwise they would just go i.e. from 5th to 3rd.

Utter and complete nonsense.

First off your mixing up engine braking and heel and toe shifts (the later of which is done to avoid the former) and to say that you have to use engine compression to stop a car effectively is totally and utterly incorrect.

Now feel free to provide a source and/or describe the physics involved to prove us wrong, but I know for a fact you can't (and if you like I am more than able to back up what I have said with both).