Why Did My Z, Keep Revving? Video.

m4a1mustang · 02-03-2010, 09:54 AM

Well most people don't know a thing about cars... in a panic situation they just stand on the brakes.

Zsteve · 02-03-2010, 10:14 AM

Quote:

Originally Posted by m4a1mustang

Well most people don't know a thing about cars... in a panic situation they just stand on the brakes.

True dat, unless you are used to being in bad situations, when you are in one you wont think like you do when you are watching it or hearing about it, you just do what seems natural and slam on the brakes. Its like making good decisions in any situation, you have to have been there and done that before.

Ever come across those people that can answer every question of a game show while sitting on the couch? Get them at the studio and they freeze up.

ChrisSlicks · 02-03-2010, 10:24 AM

Quote:

Originally Posted by m4a1mustang

Well most people don't know a thing about cars... in a panic situation they just stand on the brakes.

Yes, they stand on the brakes, which of course promptly overheat and stop working thanks to their low noise, low dust organic formulation. Actually it's because they don't hit them hard enough, you need to stomp them hard, probably with both feet if you are a girl or a girly man. Of course the other obvious alternative is to shift to neutral or even shut of the ignition (although that's probably the last thing you want to do in a panic situation).

Here's an except from C & D this month. Surprisingly they could stop the cars only a few feet longer than in the regular braking test.

Quote:

Hit the Brakes

Certainly the most natural reaction to a stuck-throttle emergency is to stomp on the brake pedal, possibly with both feet. And despite dramatic horsepower increases since C/D’s 1987 unintended-acceleration test of an Audi 5000, brakes by and large can still overpower and rein in an engine roaring under full throttle. With the Camry’s throttle pinned while going 70 mph, the brakes easily overcame all 268 horsepower straining against them and stopped the car in 190 feet—that’s a foot shorter than the performance of a Ford Taurus without any gas-pedal problems and just 16 feet longer than with the Camry’s throttle closed. From 100 mph, the stopping-distance differential was 88 feet—noticeable to be sure, but the car still slowed enthusiastically enough to impart a feeling of confidence. We also tried one go-for-broke run at 120 mph, and, even then, the car quickly decelerated to about 10 mph before the brakes got excessively hot and the car refused to decelerate any further. So even in the most extreme case, it should be possible to get a car’s speed down to a point where a resulting accident should be a low-speed and relatively minor event.

Full article:
How To Deal With Unintended Acceleration - Tech Dept.

TheWeatherman · 02-03-2010, 10:56 AM

Hey ChrisSlicks, thanks for posting that C&D article. I see that Nissan/Infiniti has that throttle cut feature. For some reason, mine didn't do that. It was pulling faster with my foot on the brake. Here's the catch, I didn't slam on the brake, I just hit it light/moderate. (I was getting close to an exit on a 55MPH highway. I just hit the clutch and coasted down the ramp after I could feel the car pulling on me. It was speeding up over 60MPH with no cruise and no foot on the gas.) I wonder if there's a threshold of cutting the throttle. As I came to my first stop, I was revving over 4,500 RPM without any let-off on the RPM. Of course I knew to just hit the clutch and let the car do it's thing. It didn't feel very nice trying to have a decent start and burning the clutch though. I'm pretty sure if I would've popped it, the wheels would've slipped a bit... That's how much throttle was being applied to the car as I was taking off. She was on a mission, and that mission was to keep on revving. I still haven't heard a peep on what happened. Your C&D article makes this even more bizarre. I'm still positive it wasn't my floormats because when I got to my first "revved" stop, I pulled my floormats away from the pedal. I really just thought it was my mistake. 4,500 RPM is really up there. I started taking a video after I restarted the car twice. That was about 8 minutes after the 4,500 RPM events. Just trying to put it all in perspective for you.

ChrisSlicks · 02-03-2010, 12:13 PM

With the throttle cut feature on the Infiniti and our Nissans, you do have to press the brake reasonably firmly. With the brake pressed the throttle input is cut back (but not cut completely) if the throttle input is moderate to high. If the throttle input is light then it will let you press both pedals at the same time and wont interfere.

As it doesn't take a lot of throttle input to rev to 4500 rpm unloaded (out of gear) I'm guessing that the throttle input signal wasn't high enough to warrant a throttle cut. Even with a throttle cut you would feel the car pull on you a little as you braked but it would be easy to overcome by braking firmly.

Would be interesting to see what voltage the APPS (accelerator pedal position sensor) is sending out in the misbehaving case. From that you could determine if it was a bad sensor or if the ECU needs to recalibrate a new up-pedal voltage. Bad sensors are rare because they do send out 2 redundant signals. It could be that the dealer screwed up the calibration by disconnecting the harness when you took it in for something else. I'll check if the car sends out throttle position or voltage as and available data point on the OBDII/CAN.

TamZ · 02-05-2010, 11:40 AM

Quote:

Originally Posted by m4a1mustang

Well most people don't know a thing about cars... in a panic situation they just stand on the brakes.

This is exactly what happened to me when a semi-truck forgot I was in front of him at a stop light and he just hammered it and ran right into the back of me..He didn't even know he hit me (how he didn't know, I will never understand!)..I was in my little Nissan 240sx and what did I do? Slammed on my brakes. As if I was going to stop the semi-truck who didn't even know I was down there in front of him. He was shifting gears, had no idea I was there and I was hitting the brakes?!? I should have hit the throttle. I was young and it scared the $#@$ out of me. Totaled my car. I'm lucky to be alive, he pushed me for a couple hundred feet before he realized he was hooked on to the back of my hatchback! (he only noticed because my car, being stuck (his big bumper sort of rolled up on my car I guess?) started to turn sideways and he slammed me into a guardrail. What I remember most about that accident is when he sheared off my radio antenae all I could hear was the static!

02-03-2010, 09:54 AM	#1 (permalink)
m4a1mustang A True Z Fanatic Join Date: Feb 2009 Location: Northern VA Posts: 55,385 Drives: on two wheels Rep Power: 6963	Well most people don't know a thing about cars... in a panic situation they just stand on the brakes. __________________ - Steve Zs & Coffee - Saturdays at 10AM in Fairfax, VA and Columbia, MD (Click the banner!) LIKE us on Facebook!

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02-03-2010, 10:56 AM	#4 (permalink)
TheWeatherman Enthusiast Member Join Date: Mar 2009 Location: Milwaukee, WI Posts: 265 Drives: 2009 370Z 6MTw/Sport Rep Power: 17	Hey ChrisSlicks, thanks for posting that C&D article. I see that Nissan/Infiniti has that throttle cut feature. For some reason, mine didn't do that. It was pulling faster with my foot on the brake. Here's the catch, I didn't slam on the brake, I just hit it light/moderate. (I was getting close to an exit on a 55MPH highway. I just hit the clutch and coasted down the ramp after I could feel the car pulling on me. It was speeding up over 60MPH with no cruise and no foot on the gas.) I wonder if there's a threshold of cutting the throttle. As I came to my first stop, I was revving over 4,500 RPM without any let-off on the RPM. Of course I knew to just hit the clutch and let the car do it's thing. It didn't feel very nice trying to have a decent start and burning the clutch though. I'm pretty sure if I would've popped it, the wheels would've slipped a bit... That's how much throttle was being applied to the car as I was taking off. She was on a mission, and that mission was to keep on revving. I still haven't heard a peep on what happened. Your C&D article makes this even more bizarre. I'm still positive it wasn't my floormats because when I got to my first "revved" stop, I pulled my floormats away from the pedal. I really just thought it was my mistake. 4,500 RPM is really up there. I started taking a video after I restarted the car twice. That was about 8 minutes after the 4,500 RPM events. Just trying to put it all in perspective for you.

02-03-2010, 12:13 PM	#5 (permalink)
ChrisSlicks A True Z Fanatic Join Date: Mar 2009 Location: North East Posts: 6,203 Drives: 09 370Z Sport M6 Rep Power: 654	With the throttle cut feature on the Infiniti and our Nissans, you do have to press the brake reasonably firmly. With the brake pressed the throttle input is cut back (but not cut completely) if the throttle input is moderate to high. If the throttle input is light then it will let you press both pedals at the same time and wont interfere. As it doesn't take a lot of throttle input to rev to 4500 rpm unloaded (out of gear) I'm guessing that the throttle input signal wasn't high enough to warrant a throttle cut. Even with a throttle cut you would feel the car pull on you a little as you braked but it would be easy to overcome by braking firmly. Would be interesting to see what voltage the APPS (accelerator pedal position sensor) is sending out in the misbehaving case. From that you could determine if it was a bad sensor or if the ECU needs to recalibrate a new up-pedal voltage. Bad sensors are rare because they do send out 2 redundant signals. It could be that the dealer screwed up the calibration by disconnecting the harness when you took it in for something else. I'll check if the car sends out throttle position or voltage as and available data point on the OBDII/CAN.