Umm... weight is the measure of gravity on a specifc mass? .... so that is why you weigh less at 50,000MSL vs. at MSL.. or more at 10,000 ft under MSL. so i guess the argument will go like - there is no weight in the car but the affect of mass and gravity as you move around a track... but i think folks are trying to explain an art - with science... its all great to figure it out, but knowing the formulas and science behind it - does not alow you to actually do it on a track in a car. I suggest watching on You tube Jackie Stewart's video on driving technique... done in the 80's its still very relevant today. he is driving a road car ( Fords) and even a old Trans AM car with 500-600HP... same principals apply... and you never hear him talk about using engine braking to either come to a stop, or corner more effectively.... I dont know how much more master class you can get than Sir Jackie!
4th gear, are you a motorcyclist by any chance? All you say about quickly reaching for the clutch when sliding and using engine braking to get the rear to slightly step out before corner entry are more of track motorcycles' racing techniques than cars'
ENGINE BRAKING EFFECTS ON WEIGHT TRANSFER IS NOT INTUITIVE I understand why you would say that... based on the formula for calculating weight or load transfer (under braking) being: weight x coefficient of friction x COG height / wheelbase Intuitively-speaking, one would not expect additional rear braking from engine braking (compression braking) to change any of these factors. I admit I did not enter into this conversation from my limited knowledge of the physics behind vehicle dynamics. I did so primarily based on my "butt dyno", what I feel when I drive and how I correlated that to analysis and discussions with other drivers or mechanics. What I'm doing now is to prove my assertions by looking up and applying the physics of vehicle dynamics. Engine braking or compression braking does not directly alter weight transfer but you will notice I made references to the car "hunkering down" when I use engine braking in my first post (post#6) and in post21. I said that because that's exactly what my car felt like when I applied engine braking. The suspension balanced and settled. So you see what I'm getting at - engine braking either retards or reverses the lifting of the rear chassis, thus retards or reverses the lifting of the COG. This then reduces weight transfer because COG height is reduced. I am not saying engine braking reduces the COG height when the car is at rest. I am saying normal braking tends to cause front brake bias, leading to higher vertical loads on the front suspension while reducing loads on the rear suspension, which then causes nose diving and the simultaneous raising of the COG. Since engine braking reduces brake bias, the raising of the COG is retarded (slowed or reduced) or reversed (if engine braking is applied after normal braking has started). ENGINE BRAKING IS NOT (ONLY DEPENDENT ON) DOWNSHIFTING At this point I think I also need to make sure everyone agrees that engine braking is not just downshifting because ANY TYPE of ENGINE COMPRESSION BRAKING is engine braking. So if you are already in a low gear and you reduce throttle, the compression of the engine from the resulting rise in engine speed will cause driveline drag and result in engine braking. We all engine brake whether you like it or not. You do not need to downshift to introduce engine braking. How much engine braking you get from your engine depends a lot on how your engine was designed, how much compression it has, normally-aspirated vs turbo, how many cylinders, volume, and how sharp the throttle cut-off is. GYROSCOPIC EFFECT FROM PRECESSION Finally just for laughs (and then maybe not), there is the interesting comment I made about the gyroscopic effect (of the reactive couple) that results from the momentum of the rotating engine with regard to cornering. jcurry is an aerospace engineer and recognized what I might have been alluding to, and asked a question, allegedly in jest about whether I had a preference in right or left turns. I replied that I preferred right turns. According to the technical reference that I posted, a car with an engine rotating clockwise (when viewed from the front) making a right turn would tend to lift its front and depress its rear. I checked, almost all car engines run clockwise when viewed from front. It is also interesting to note most F1 tracks are driven clockwise (mostly right turn). Ovals are not but they are also banked which lowers the COG and the angled banking reduces the need to brake for corners. Perhaps someone who knows more about these observations would care to comment? Image Unavailable, Please Login I mentioned gear-skipping because there are different types of corners and not all would benefit from engine braking. IMO, low speed corners (tight hairpins) only require 1 gear change but the driver might be threshold braking from 200 kph to 40 kph before a short turn-in to the apex so gear-skipping would be in order. The DCTs in F1 racing should be able to accommodate gear-skipping just like the ECU can drop DCT to 1st gear to avoid stalling. I then demonstrated using the F1 website, that automatic transmissions (gear skipping) are currently forbidden... because they want the drivers to demonstrate driver's skill. So the sequential downshift for a tight hairpin is simply a casualty of this regulation. FYI, DCTs can work this way. If you've read the FChat threads on DCT malfunctions, one of them is when one clutch no longer works the DCT will then only shift the even or the odd gears depending on which set is still working... skipping gears. And of course there is a good reason to allow DCTs to skip gears... like to avoid stalling. It's just software programming of whatever engine RPM you want to use as a parameter to select a specific gear when: A) the driver wants to downshift, or B) if the primary ECU control software determines the car should downshift (like COMFORT vs SPORT mode or KICK-DOWN situations with automatic transmissions). You answered to my original point and I showed you the F1 material... and now you say it's pointless. So why did you answer in the first place? YOUR IDEA OF BALANCE(BALANCING BY THROTTLE) IS SIMPLY ENGINE BRAKING Your definition of balance is simply playing with the throttle, which as I already stated, is just engine-braking. So the balancing you describe IS engine braking. Engine braking is not only limited to the instantaneous moments when you downshift to cause what some people insist is always uncontrolled driveline drag. F1 transmission cars can be and are downshifted smoothly while cornering, to facilitate engine braking (playing the throttle). DCT downshifts do not result in any differences in torque delivery, you must reduce throttle to actually change torque delivery when you downshift a DCT. You need to understand what engine braking actually is - just simply compression braking.
I know that. I'm just using the DCT term generically because F1 cars also use dual-barrel transmissions. They are functionally similar to Getrag DCTs.
Well, that's not quite what I was trying to say. Yes, I would de-clutch if the car were sliding out of control, simply to allow the tires to regain traction under steering effort, but that would only be a low speed scenario or at the final stage of coming out of a high speed spin as the car slows. Declutching lets the tires run as the steering points them. Once they start rolling free you have control again, along with traction. But I don't declutch if the car is sliding a little bit but still under control, I would probably just adjust the throttle slightly to tuck the rear back in. I don't use engine braking to get the rear to step out. I use it to brake and to settle the suspension. If I want the rear to step out I would use throttle to lighten the rear end, promote more oversteer. At low speeds, a handbrake turn would be a lot more controllable than suddenly dropping the engine into low gear and high revs. Engine braking is fine control of engine compression effects on the driveline. We all do that when we slow down in gear, without brakes.
Can I ask what your driving education and/or racing experience is? You are giving some pretty dangerous advice. Correcting a slide requires steering input as the initial recovery mechanism. Both Skip Barber and BMW teach CPR - Correction, Pause, Recovery. The correction is steering angle, not throttle as you suggest. The correction may be accompanied by a throttle adjustment, or it may not. Thinking that simply removing throttle will correct a slide is an indication that you are likely use to car control nannies helping you by actuating the brakes to stabilize the car. If the rear is sliding and you keep the same steering angle and remove throttle, it will increase the slide, not decrease it. Now the rear end is continuing in the same direction it was going with no steering input to correct it. You have exacerbated the slide because removing throttle will transfer weight forward and unload the rear tires which are sliding and need traction. In your technique, you are *hoping* that the tires will have enough grip to regain traction as speed decreases. This is totally incorrect and you have no idea which way the car will be pointed when it finally does regain traction. It may work under the right conditions up to a certain low speed, but it will send you into a violent spin if you are driving on the limit. Neutral has no place in recovering a slide. Neutral is simply engaged so you don't stall the engine and you can get the correct gear once the EDIT:spin is over. Also potentially so you don't roll backwards in gear with the clutch engaged. If you are in a spin, you want to lock the brakes and spin in a straight line. Trying to drive out of a spin is a sure way to shoot across a track or a road and get someone killed. No driving school in the world teaches "engine braking to settle the suspension" which you have repeatedly suggested is a valid technique. Because engine braking doesn't stabilize the car, it transfers weight forward as the car decelerates. It's the same reason (physics) why you can get a car to turn more, mid-turn, by simply lifting from say 100% throttle to 25% throttle without changing the steering angle. That will transfer weight to the front wheels so they have more grip, and away from the rear so that it allows the car to rotate.
I'm sorry but you would appear have a distorted agenda, whether it is conscious or not. Your inaccurate comments about my discussion saying that would "get someone killed" are simply incendiary and outrageous. You have ignored what I actually wrote and then twisted the rest of it, making references to an old thread in your own words in a way that suits your arguments. I find that simply bizarre. I clearly wrote "I would de-clutch if the car were sliding out of control, simply to allow the tires to regain traction under steering effort" ... can you read? I said "...under steering effort". I also said "...that would only be a low speed scenario". Igor Ound posted his message partly in reference to my having discussed using NEUTRAL to steer out of a spin, again, in low speed scenarios. Since you obviously don't bother to carefully read my post and would like to drag in unrelated material that no sensible person would like to have to verify, I won't comment on the rest of the wrongheaded diatribe you just posted. I hope your lack of care in reading is not a reflection on the way you drive. I will ask the moderator to have your comments deleted. You sir, are way out of order.
I do have an agenda. It is to correct incorrect information which might get someone in trouble. I read it. I just chose to only respond to the worst errors. Which is incorrect. De-clutching the car will not help the car gain traction. Using the CPR technique will - regardless of speed or conditions, it is the correct method to recover from a slide. Neither the clutch, nor neutral are part of it. I have no idea what thread you are talking about. That's a classic debate tactic to opt out of defending your statements - accusing me of not reading what you wrote properly. Fortunately for me, nothing in my post violates the rules here. Vehement disagreement is allowed and really the premise of a discussion board anyway.
Also - my original post should read: Neutral is simply engaged so you don't stall the engine and you can get the correct gear once the SPIN (not slide) is over. Also potentially so you don't roll backwards in gear with the clutch engaged.
Really. You make it sound like misrepresenting other people's words and ideas, refusing to apologize for blatant errors and hysterical personal accusations are something you and this forum would be proud of. Bravo!
4th_gear and singletrack: The two of you have reached a point where you've both stated your arguments fully, neither will concede any point to the other, and the only place left to go with this is "I said/you said" and personal insults. I've seen enough threads like this one to know where it's headed. My suggestion to you both is to just move on.
Your first reply to spirot was the same - that he didn't understand what you wrote. No idea what errors I made because you didn't care to address them. My statements are accurate to my knowledge and based on my training and experience. I welcome correction to them if they are inaccurate because it will improve my knowledge. No one is hysterical, and no one made personal attacks. I don't represent this forum aside from being a contributing member. Sounds good sir.
Well, it's nice to have you finally say something. It would have been better though, if a moderator had simply reminded singletrack not to make (inaccurate) hysterical accusations using incendiary language like "getting someone killed". As far as I can tell, I did not post anything unusual or dangerous in my short reply to Igor Ound's innocent remark. Please. I had made a reasoned and polite request when I immediately reported singletrack's unwarranted remarks. I then waited for a moderator to respond rather than further confront singletrack, who was clearly in a self-inflicted riled state. A simple reminder at the right time from a moderator would have resolved matters. It took singletrack's further remarks to inform me that no moderator would be intervening. That's when I made my final reply. Was there no moderator on duty at the time? As for a reasoned and polite discussion of engine braking and methods of slowing, I see no reason to end my discussion with any other member who cares to politely discuss the topics.
Michael, Many of the moderators are at the FCA meet at Pebble Beach, so responses will be a little slower at the moment. In my view, both you and singletrack made your cases vigorously, strenuously disagreed, and readers have sufficient information to decide which viewpoint they'll accept. I don't think he was hysterical in the manner you suggest, and see nothing so far from either of you that requires sanitising from the board. Let's please let the matter drop before it escalates to something that will require more active moderation. It's a beautiful Sunday, perhaps it's a good time to go enjoy a drive. All the best, Andrew.
The day did indeed looked pretty good but then so did the last few days here. Unfortunately we've also been issued HEAT WARNINGs from the authorities; nothing really dangerous but just uncomfortable enough to spoil roof-down excursions. As for the FCA meet, perhaps someone will share their experiences... when they recover from the event.
I tried my hand at some fishing but, sadly, failed miserably and had some wine instead. I'm looking forward to some FCA meet photos. I'm sure someone will have taken some. All the best, Andrew.
I got a short note back from my F-1 "friend" ... in short he said WTF? engine braking in modern F1 does not happen at all. its all on the brakes because of the ERS and KYERS... he did say that keeping the balance from braking to acceleration in mid corner is the key to a fast lap, and recommended looking at both Hamilton and Vettel in how deep they brake / acclerate. Lastly he stated that having driven a number of modern Ferrari's the latest being the La Ferrari at Abu Dhabi... that simply taking your foot off the gas in a straight line produces no real braking effect... but in an F-1 car becuase of the aero & drag package its about 1G lateral forces you feel in your shoulders and neck. he did say that La Ferrari has about the closest braking feel to F-1 ... but he has yet to drive the P-1. for those who are questioning / wondering... he wears a kilt and dates supermodels....
What you relate from your "be-kilted F1 friend" about the latest developments in F1 braking is true. KERS, and now ERS, exert a lot more rear braking power than engine braking would otherwise exert. This along with electronic control of throttle and braking means that engine braking essentially no longer exists. Indeed, to quote your own words: "...[size=+1]engine braking in modern F1[/size] does not happen at all. its all on the brakes [size=+1]because of the ERS and KYERS[/size](sic)...". The current ERS essentially replaces KERS and previous to that, engine braking, as the potent internal rear braking force. Drive-by-wire and brake-by-wire controls are used to balance out the dramatic contributing effects ERS has on rear braking. This probably explains why some test drivers find the brake feel weird in the new hypercars that use KERS and ERS. Here is part of what I was reading a few days ago in this article on F1 technology. Image Unavailable, Please Login However, unless you are privileged to own an LaF, P1 or 918, KERS/ERS technology does not apply to the track toys the rest of us can have at our disposal and nearly all driving enthusiasts will still be going around circuits in their Miatas, corvettes, 308s,... and 458s for quite some time to come. So my discussion of engine braking remains relevant. The replacement of engine braking by KERS and ERS serves to cast light on what is commonly referred to in technical parlance as "internal braking forces"... BTW for those new to this term (as I was), "external braking forces" refer to friction at the contact patches as opposed to braking effects like engine braking and ERS, which occur inside the car. The replacement of engine braking by KERS and now, by ERS, has been discussed by track enthusiasts for quite some time already. Here's a 2014 discussion on a Miata discusssion forum in a thread titled "F1 engine braking" under "Professional Motorsports". BTW, I'm sure we all hope your friend would remain in the F1 scene for many more years to come.
Very cool. Also interesting to note that this is also where you find all the speed in something as basic as a Formula Ford. Trail braking in to point the car and carry momentum, then making a smooth transition to throttle to keep the car composed and carrying as much speed as possible - as I'm sure you know. No engine braking involved. Awesome stats - thanks for sharing. Really amazing aero. As a basis for comparison, a basic formula car can pull about 1-1.5g's threshold braking. The F1 cars pull the same deceleration g's just from downforce! Nuts!
