I don't know, but the other day when I was playing Forza Motorsports on my xbox i noticed that I would stop quicker when down shifting. But that's with racing tires j/k. But yeah, the limiting factor is the tires, hence abs. If you can get abs to kick in you've maxed out your tires.

 

sure i *** around in my car, but not to a point where an emergency situation would arise. just wait till you hit a kid, so he can sue your family and u can spent a few years in jail.

 

lol

but the down shift does slow down faster and no i was not around people just i had some problems with the road ahead on an empty side road

 

No... downshifting does not slow you down faster than max braking on a Z. Using the engine to slow down is very useful on downhill section where you don't want brake fade, but it is not recommended for maximum braking. In fact, hard "braking", with the engine, only uses the rear wheels on a Z whereas max braking is obtained from the front wheels using the brakes. I have used an engine brake on a motorcycle on a steep downhill section, but here we are talking about control and the need to avoid going head over heels. Engine "braking" is also useful entering a corner at times, but still not as effective as getting on the brakes.

 

im pretty sure downshifting will help you brake faster. All about that rotational mass. Yes the tires and their contact with the road is what does it, and not until you reach an abs point have you maxed out the braking ability. Adding the increased rpms absorbs more energy than lower rpms. Idk what the ecu does, but lets say the fuel is cut and the engine internals spin freely, requiring a force from the wheels/drivetrain to keep the engine spinning. Hence the engine slows down naturally because its taking energy from the wheels.

Now add in the brakes, are you braking the wheels, or the wheels and the enigine, idk! But it seems like it helps.

plumpzz, settle down man. grampa! go pester some kids at the park with your cane and air breater.

 

So was it your f**king around that caused the emergency situation? At any rate, the time it took you to process and execute the downshift was valuable time wasted that should have been applied to simply hitting the brakes as hard as possible and letting the ABS do it's job; that'll get you to a stop faster than anything. I never worry about what's in front of me in panic stops, but what's behind me, the Z's brakes are so good.

 

I buried the tach three times in a matter of 3 days (thus wondering if it lead to my noticable 'tick' I've developed). Managed to pull a 3-2 (intended 3-4) shift at 94mph... *sigh*

Ironically, and sadly, I'm the guy that always when I hear/see people 'misshift' - ah well...

 

uh...94mph in third gear? I thought 3rd only goes to 85mph.

 

Unless you have a 3.3 rear with your turbo

JoeDirtPharmD <---- has turbo w/ 3.3, good for 33mph 1st, 64 in 2nd, 94 in 3rd, 119 in 4th, 141 in 5th...

 

Only reason is cuz hes a total retard. US HSM or hraevsleg would've totally riped him to shreds if they were to come in here.

 

why not use your brakes?

I'd doubt you damaged anything although there's a good chance for valve float and spun bearings...

 

This would be true in _max_ braking only if the brakes could not generate lock up power by themselves. This is not true on the Z cause the brakes are plenty strong enough to lock up all the tires all by themselves. If you doubt, go test it yourself, panic stop as you pass a cone using brakes only, and then panic stop as you pass a cone with downshift and braking. Post your stopping distances with a standard deviation.

I am not arguing that downshifting is not a useful technique in controlling speed. I am emphatically stating that downshifting and braking is not going to help in a _panic_ stop when compared to using the brakes alone on a Z.

 

Those of you who have made downshifts instead of upshifts, have you noticed any irregularities at all? Anyone here know for sure they've floated a valve? What did it take for them to float?

 

i accidently let my cousin drive my car one time. he was redlining it at 3rd gear. usually one would do a 3-4 shift. however, he thought a 3-2 shift would be fun (accidently) and wow did i get scared. the nose dipped and tires squealed. was really scared, luckily i was getting a new tranny anyway

 

I made the mistake once of letting my buddy drive my Firebird down HWY5.

He asked if he could jump on it. I said, "You pay the ticket, OK with me."

Unfortunately, he hasn't driven too many manual transmissions before. So, as he is approaching top of third gear he shifts into second. The motor overevs so much that the rear tires start skidding. I like OMG (In my mind cause it was too fast). My buddy had presence to shove the clutch back in and let off the gas.

Lucked out, on a car with push rods you would normally bend the heck out of them and cause at least a ticking of the valves. Or, spin some rod or journal bearings. Not this time. Whew, and the car has been raced a lot since. So, we lucked out that night. I'm glad the motor didn't let go.

Now on overhead cam cars (Z's), the thing you have to worry about is the bearings. Hopefully, I never experience that.

Needless to say, I have never let my buddy drive my 350Z.

He ended up bending push rods on another car later that year with a manual valve bodied automatic. "I was just screwing around showing off to my buddy." That ended cost him over 2K and us about a month of tear down and rebuild on his 327. The worst part is he took the car to LA for a year and left the motor out in the rain. Motor had to be rebuilt again. Doh !!! Some people just don't do good things to motors.

 

Funny topic. MulhollandDrive is right about the braking bit. But it's still fun to read some guys theories...

If the engine runs fine now, it's probably ok. Floating a valve and hitting it is usually noticible...

 

only one way to find out. do a compression test, and next time you change your oil send it off to be analayzed.

the comp test will let you know if you bent a valve. and the oil test will tell if your bearings are worn.

 

hehe, that's funny right there you just brought back old memories of statistics

if you think about it, at some point the brakes will not be able to lock up the tires. by that I mean simply taking into account the rotational velocity and inertia of the wheel itself, at some speed the brakes will not be able to lock up against the total energy in the system. so once you have passsed this speed then engine braking will be able to assist braking. now is this at 90mph? idk. but doing a stopping test at 20mph isn't going to prove anything versus the given situation. now, slamming on the brakes at 120, that I'll leave up to someone else

hey CUxtopher, go ask Dr. Law what he thinks about this would ya?
-Paul

 

You are wrong, but it’s okay. You can still hang around. Bench racers are everywhere…

Stating imaginary laws of physics and ignoring other (like the weight transfer of a car under braking, reducing available grip on the rear tires and necessary brake bias) is fun. But don’t help your case.

Anybody who feels the car brakes more with engine braking is:

1-Not heel and toeing properly. The car should not jerk around when downshifting under braking
2-Not braking hard enough.

But the real world limiting factor that make just hitting the brakes better is it’s easier to manage. Concentrate on one thing: the brake pedal (forget blipping, moving your feet, shifting or clutching).

 

I'm not ignoring the dynamics of the problem but merely simplifing it. I could go through and explain the multiple degrees of freedom for a vehicle dynamics problem such as this but there is no need. Simply put: the brakes can only apply a limited amout of force and dissapate so much energy. Like I said before, at what speed this happens, idk. For those of us who do not have bbk or brembos, the stock brakes are not that great. Making it more difficult to stop quickly. If you line up a Track model vs a Base (both with OEM tires) and check the 0-60 braking distance, who do you think would win? If you noticed Bee Ess Pee's sig you would have seen he only has pads listed, not a bbk.

But I do agree with you on this. If you really have to stop quickly, just hit the brake as quick as possibly and don't waste the time it takes to shift. But I wouldn't push my clutch in either, unless I was at a stopping speed.
-Paul