Best way to slow down.

Edit: JWeiss, you are 100% correct. At this point I think it's pretty clear this whole thread has been punked by this guy.. he's speaking gibberish just to get everyone going.. I would suggest everyone disengage and stop giving him the satisfaction.

 

I just don't think he likes to be told he is wrong, so he just keeps massaging the argument to try to win some imaginary debate he is having. It's somewhat humorous to be lectured on racing by someone who has never even set foot in a real race car.

And 4th gear, that is not what trail braking is. Trail braking is simply having the brakes applied as you turn in. It has nothing to do w a specific amount of pressure. It helps point the car because race cars are set up to have front bias brakes, so it slows the front tires more, loads them, and rotates the car. It has nothing to do with threshold braking which is applying max pressure to the brakes before the tires lock and you start a skid. Most formula cars also have a brake bias adjustment in cabin. Lifting off the throttle doesn't change the bias, it changes the weight distribution and the contact patch of the tires. As already explained.

 

Michael, perhaps you should take a bit of a risk and dare to try and learn.

Whether here on the debate-filled internet, or by getting in your Ferrari, slapping on a GoPro, and having a professional teach you. Mosport is just down the street from you, they have a great skidpad and car control program, and it won't hurt your Cali a bit. Better yet, go to Mont Tremblant and take the driving program - use their Californias on the wet skid pad and learn all about weight transfer, braking, throttle application (or not). Believe me, you'll leave a better driver and know a lot more.

It seems so.

 

Applying throttle would actually remove engine braking but it can be part of that balancing we've been discussing.

As for why the driver would do that that I think it really depends on what is on his mind... wanting to go faster because he can or trying to yaw the rear end because he wants to maintain speed but needs to dial back understeer without slowing down.

I reviewed your assertions with my experience and they don't correlate. Here's why.

The rear will only hunker down if you add throttle while the car is going straight. But we're not going straight, we are actually braking (trailbraking) in mid-corner while still in gear and under throttle so the car is already cornering as fast as it can while under control. If you then add more throttle under those conditions, one of the effects will be an increase in the load transfer from the inside to the outside wheels with the effect most dramatic at the rear, the inside rear will want to rise towards the outside front. In a worse case, the car will tip outward onto 3 wheels and the rear inside wheel will be off the ground.

Conversely, if you lift throttle while trailbraking in a corner, centrifugal forces will drop and the inside rear will settle back down. Lifting throttle would only raise the rear if the car was accelerating straight.

 

Thanks for your suggestion. Mont Tremblant is probably a smarter idea than Mosport track days with my Cali and perhaps I will do that some day, but not at the moment. My driving skills are serving my needs just fine.

In the meantime, nobody here has convinced me that engine braking is not useful.

 

Why is anyone still engaging on this thread.. he is a troll that is simply antagonizing everyone.. let it go.

 

^^This^^

 

ProCoach has the most credentials so we all have to shut up and listen to him.

 

As Wayne mentioned, we've seen a lot of these debates go by. They fall into a lot of different categories, some are simply preference A vs preference B, to which there is generally no resolution, while others are a mix of expert vs amateur vs naif.

In perusing the thread, it appears you've not made any claims to be an expert, but instead claimed the effective status of amateur. Given that there are engineer-experts and driving-experts on the thread that are explicitly contradicting you, it seems to me that the burden is not on them to convince you, but rather for you to convince them.

The odd thing about internet forums is that it creates the impression that everyone's posts and opinions are just as valid as any one else's. There is no way to stop someone from posting any theory or opinion they care to post (short of a mod intervening for rules violations) or to stop others from leaving if they get frustrated at what they consider persistently inane posts.

This forum used to be populated by knowledgeable Ferrari techs who were quite willing to help DIY-ers fix their cars with advice and tips. As the forum grew, most of those techs stopped being so helpful and stopped posting. Why? Because they became frustrated at getting into arguments with DIY'ers answering a question with wrong info, that might have worked for that guy once, but was actually a bad practice or a failure waiting to happen to an unsuspecting reader. In their attempts to save the questioner from a disaster they would argue with the self-appointed responder, who considered himself just as knowledgeable as the techs, based on fixing a car once. It became clear that the techs couldn't win those arguments, simply because the DIY responder refused to acknowledge that the tech had more actual experience and knowledge than they did. The expert techs, taking time out of their livelihood, to help someone for free, eventually decided that was not a worthwhile exercise and stopped getting involved, leaving bad info more prevalent.

Now, I'm not saying your theory is right or wrong nor that your perceptions are invalid. What I am saying is that if you acknowledge that you're an amateur driver and an amateur physicist/engineer, then it seems to me the burden is on you to convince the experts rather than that they should convince you. I do see you've made numerous posts in that attempt, but I've also seem some portion of those posts have elicited responses asking you to correct some of your force diagrams or pointing out some misperceptions, so you're both exchanging your viewpoints to some extent.

Yet, you've failed to convince them and they've failed to convince you. So is it more likely that 1 or 2 amateurs are being stubborn or is it more likely that up to 16 experts/amateurs are being stubborn?

 

I am positive, if I flip my racecar it will lose all four tires contact patch. I am also positive if I followed the physics of one poster here, I would prove the validity of the previous statement sooner than later.

 

Concur.

...and it's a privilege to have experts like him around also!

 

There are some master class lessons being taught in this thread, and I'm not talking about the driving dynamics/car control discussion!

Wow....

 

There was one thing that came up in a discussion with a racing friend of mine... that i forgot, that may point to some of what our Engine braking friend is noticing...

Flywheel effect. the larger the mass of they flywheel you will feel an enging braking effect as the wheel slows and then speeds back up during a shift- but this really only in manual trans. cars. The modern Ferrari road cars have such a small fly wheel the gearbox take cares of that ( senses the speed etc.. ) in a racing engine there is almost no flywheel.

 

Yin, with all due respect, no one on this forum has provided definitive proof that he/she is an "engineer-experts and driving-experts". Self-proclamation is not definitive proof and intimidation tactics are also not considered definitive proof of anything except a display of bad manners.

As regards claims of "engineer-experts", I have explained and provided external references that show the gyroscopic effect to be a significant physical phenomenon in vehicle dynamics and yet jcurry, who is supposed to be an aersospace engineer by his profile, has been curiously silent even when confronted by the external references. No other "engineer-experts" on this thread have tried to prove or disprove the significance of the gyroscopic effect. So what good is a person's professional claim when he fails to exercise his claimed expertise?

Please understand this is not a legitimate court of justice where I am a prosecutor trying to prove someone is guilty. I am not even disproving anyone's cornering technique. I am just reminding people that there is another way to slow down in a corner and that cars using traditional brake and engine management by the driver can benefit from using engine braking. I hope you understand why I do not accept your premise that my detractors, "experts" or otherwise, do not owe anyone, least myself, any explanations for their claims.

I also recall when I first tried, innocently, to politely suggest Ferrari might include a NEUTRAL button on their F1-style steering wheel to make it easier to engage neutral in an emergency recovery maneuver. To my utter surprise and disappointment, it was greeted with vehement personal ridicule and many of my detractors even called me a troll, alluding to my not actually owning an Fcar; never mind the fact that they didn't own an Fcar either. A month later, my new Cali30 arrived and they had to eat their words. Unfortunately, the mountain of personal verbal abuse I already endured in that thread had more than waylaid any level-headed discussion of the subject. The damage had been done to intellectual discourse and to me.

It is only with polite explanations and discourse that people can respect and learn from each other. A couple of my detractors here have generally tried to do this on this thread and I respect them for it. However, one of them has yet to provide technical arguments to prove engine braking is devoid of benefit and the other one has only provided indirect credible claims that at the least, do not disprove my assertions about the usefulness of engine braking; and at most, would seem to provide indirect validation. I hope these persons will remain objective and that others will follow.

IMO, you should not automatically believe anything you read on the Internet (even website of legitimate authorities have been hacked before). However, do pay attention when people bother to explain their claims and walk yourself through their explanations (I have gone to the extent to even make complex and well-executed technical drawings which take a lot of time to do). All the better if they uses credible external technical references to back up their claims and explanations. Try to be fair and analytical in your assessment, and try to respond in the same reasoned manner if you wish to discuss your idea or critique. Be wary when someone engages in personal attacks and summary dismissal of ideas they don't like.

I say this with 100% honesty. Enjoy your day.

 

+1

About the size of a hamburger.

This fact also obviously pretty much rules out any "gyroscopic effect" too of course.

I've managed to keep quiet so far (unusual I know! ), but must admit I've had some good chuckles at some of the nonsense that's been posted herein.

Vehicle dynamics is a pretty well understood field, and high performance driving, particularly in this "data driven age", maybe even more so. I'm sorry, but comparing the dynamics of a race car with a friggin' *bicycle* is ludicrous!

Cheers,
Ian

 

Yes thanks, I have noticed a similar phenomenon. I also suspect flat-plane Fcar engines probably exhibit less of the gyroscopic effect.

FWIW, I sat in my truck yesterday, flipped the transmission to NEUTRAL and revved the 5.7L Hemi several times to at least 4,000 RPM. Sure enough, the truck wagged noticeably from one side to the other. The Hemi has its own mechanical characteristics which may play a role in this phenomenon but if we consider traditional cross-plane crankshafts with heavy counterweights, the gyroscopic and flywheel effects through the driveline and engine mounts would be worth considering. Big-displacement old-fashioned engines will definitely move the vehicle about if you rev them in neutral... consider then their torque effect with all the transmission hardware attached while the vehicle is in motion.

I had tried to touch on one aspect of the gyroscopic effect but it's much too complicated an area for me to even attempt to fully understand or give a full picture. So with the help of the external technical reference I provided, I only displayed enough information to cause people to think about it.

Keep in mind also, that the flywheel and gyroscopic effects are supplemental driveline effects and do not cancel out combustion braking, which constitutes the bulk of the effects from engine braking.

 

Reminds me of a story one of my instructors told me. He had a former Olympic speed skater in his class. This guy could not believe that the optimum path around a corner was not to hug the inside radius, as they do in speed skating. He had an argument for everything, then got out on track and learned quickly exactly how much he did not know or understand.

 

You'd suspect wrong then - Sorry! The flat plane cranks advantages are many - don't need the huge counterweights used in a cross plane for one. Hence lighter and therefore faster revving.

But think about the forces involved here; There's a torque reaction of course, often made "worse" by the counterweights. But any "gyroscopic" effect/reaction will be pretty much the same between the two.

That's torque effect and the (flexible) engine mounts are trying to absorb it. nothing to do with any gyroscopic effect. Remember though that real race cars have their engines mounted rigidly - often as stressed members. Ergo, those loads are fed back into the car, and they don't "wag noticeably" when revved.

As Tom noted, and Procoach confirmed; "I can categorically state that no professional driver coach that I've been instructed by has ever stated that engine braking is used to slow the car."

Cheers,
Ian

 

Page 10 of this thread seems a good round number to move on. I dont think 4th gear is going to accept any of our feedback, its pointless to keep blathering on.

I don't see an F-1 drive in my near future so - whatever forces are at work in F-1 I will not experience first hand ( might get some Sim time in an up coming trip...) Nor will I be using engine braking as a primary or secondary means to slow down on purpose ( missed shift - possible )... I do however beleive that I'm competent in driving, and perhps a tad bit better than your average driver. World Champion ( in anything is also not on my future) ... so I propose this... We who have been trained in the traditional method of driving practice what we preach... and same goes for 4th gear. I do ask one thing, from Mr. 4th Gear. please let people know about your driving ideas BEFORE you get on track with them I would want to know so I can stay back appropriate distance... and I'd reccommend Lockton Insurance be on speed dial.

All the best
tom

 

We agree to disagree...

 

WOW, I just came across this thread and all I can say is WOW!

 

When you comprehend the principles of Engr 101 (static 2-D bicycle free-body-diagram) and dismiss your notions that rear wheel braking, whether by 'exterior' or 'internal' forces, does not cause forward shifting of 'weight' then I will discuss higher order mechanics.

 

Yes, I know that. That's why I specifically pointed to heavy counterweights used in cross-plane engines.

OK, I will accept your assertion if that's your experience and assessment. However, one reason why I pointed to the cross-plane engine counterweights is because their greater mass may result in a more massive crankshaft and thus a stronger gyroscopic effect.

I think the back-forth movement of the engine is probably caused by reaction couples from opposing engine mounts.

An inherent imbalance in the engine creates the original precession couple which pushes the engine against one set of engine mounts (gyroscopic tilt). In fact, if I were to maintain throttle, I suspect the engine would simply press hard against one side of the engine mounts and stay in that position as long as I maintain throttle.

The engine would then recoil back once I lift throttle because the precession couples from the engine's inherent imbalance would reduce with less throttle and the reaction couple from the compressed engine mount would then push the engine back the opposite direction until the opposing engine mount's reaction couple overcomes the initial reaction from the other engine mounts and pushes the engine back the other way and so on... hence the "wag".

OK, I will also take your word for that. However, I still say we all use engine braking every time we drive. Every time you let the car coast and slow without brakes, engine braking occurs. So perhaps our differences regarding engine braking is in what we consider as engine braking.

I view engine braking as using the engine's compression and driveline inertia to cause a drag on the car, from the point of downshift to when I allow a lower throttle position to decelerate the driveline faster than the car is decelerating (i.e. the wheels are turning faster than the transmission will allow them to turn).

I suspect driving coaches are more concerned about learner drivers not braking hard enough for the corners and also worry they may upset the chassis if they are too heavy with downshifts trying to add engine braking. I don't think it's due to coaches and experts like yourself believing engine braking doesn't work. The main beef I hear is that engine braking is too difficult to control. I agree that may be true for some drivers, but if a driver plays effectively with the throttle in the middle of a corner, he's using engine braking to good effect.

 

No. Some of your comments are not "blathering". I also think it's interesting that there is such a big difference in "opinion" on engine braking. I do see the point in driving coaches not wanting to encourage new students to engine brake... perhaps at least not until they are competent enough on the track to find out for themselves.

As for myself, high performance driving insurance is a big deal... not because of engine braking but because sh*t happens and I may also find myself behind someone who has a bad day at the track. But not to worry, I am used to racing and I work my way up gradually. In the beginning it's always more important to be smooth than to be fast.

Cheers!

 

That might take a while so let's at least call it a night then .