5-60 SLOWER than 0-60- WHY...?!
02-22-2007, 09:17 PM
#11
5th Gear Member
Join Date: Mar 2006
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Posts: 3,758
RE: 5-60 SLOWER than 0-60- WHY...?!
When you launch from a dig, you can build up a lot of energy. When you gun it from a really low roll, you only get to use the power that you make at that low rpm at first.
Example: Powerbrake and brake stand an automatic versus just flooring it, or high rev clutch slip launch in a manual versus just flooring it from 2k rpm.
Example: Powerbrake and brake stand an automatic versus just flooring it, or high rev clutch slip launch in a manual versus just flooring it from 2k rpm.
02-22-2007, 09:41 PM
#12
4th Gear Member
Join Date: Mar 2006
Location: CA
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RE: 5-60 SLOWER than 0-60- WHY...?!
pretty much what Sleeper05 said,
Crazy Al is right about the stored energy. Slipping the clutch from high rpms transfers more of the power that is made at those rpms, so when you go from a stop in a manual and quickly transmit 70% of the engines torque at 2500+ rpms you start in the engine's sweet spot. If you are engaged at 800 rpms, you have to wait for the revs to climb to make and transmit most of the torque. What are the rpms at 5mph, 900-1000rpms? So you have to wait after you went to WOT for the revs to climb and start making good power, hence that waiting time is what makes those 5-60mph times slower. I am no automatic tranny expert but from a stop when you punch the gas, don't the revs climb and once to a certain rpm engage the stall/torque converter? Then you actually start transmitting torque to the rear wheels after your revs are up. However, when you start from a roll, the converter is already engaged so you too have the wait for the revs to climb before your engine starts making good power.
I took physics a long time ago so it's a little rusty, but when you are at 5mph and go WOT your acceleration curve will not be as steep as the acceleration curve when starting from a stop because you started in the lower, less powerful rpm range. And a slower acceration curve means it takes longer to reach the same distance/speed.
Crazy Al is right about the stored energy. Slipping the clutch from high rpms transfers more of the power that is made at those rpms, so when you go from a stop in a manual and quickly transmit 70% of the engines torque at 2500+ rpms you start in the engine's sweet spot. If you are engaged at 800 rpms, you have to wait for the revs to climb to make and transmit most of the torque. What are the rpms at 5mph, 900-1000rpms? So you have to wait after you went to WOT for the revs to climb and start making good power, hence that waiting time is what makes those 5-60mph times slower. I am no automatic tranny expert but from a stop when you punch the gas, don't the revs climb and once to a certain rpm engage the stall/torque converter? Then you actually start transmitting torque to the rear wheels after your revs are up. However, when you start from a roll, the converter is already engaged so you too have the wait for the revs to climb before your engine starts making good power.
I took physics a long time ago so it's a little rusty, but when you are at 5mph and go WOT your acceleration curve will not be as steep as the acceleration curve when starting from a stop because you started in the lower, less powerful rpm range. And a slower acceration curve means it takes longer to reach the same distance/speed.
02-22-2007, 10:02 PM
#13
3rd Gear Member
Thread Starter
Join Date: Nov 2006
Location: New Jersey
Posts: 983
RE: 5-60 SLOWER than 0-60- WHY...?!
ORIGINAL: UrS4
pretty much what Sleeper05 said,
Crazy Al is right about the stored energy. Slipping the clutch from high rpms transfers more of the power that is made at those rpms, so when you go from a stop in a manual and quickly transmit 70% of the engines torque at 2500+ rpms you start in the engine's sweet spot. If you are engaged at 800 rpms, you have to wait for the revs to climb to make and transmit most of the torque. What are the rpms at 5mph, 900-1000rpms? So you have to wait after you went to WOT for the revs to climb and start making good power, hence that waiting time is what makes those 5-60mph times slower. I am no automatic tranny expert but from a stop when you punch the gas, don't the revs climb and once to a certain rpm engage the stall/torque converter? Then you actually start transmitting torque to the rear wheels after your revs are up. However, when you start from a roll, the converter is already engaged so you too have the wait for the revs to climb before your engine starts making good power.
I took physics a long time ago so it's a little rusty, but when you are at 5mph and go WOT your acceleration curve will not be as steep as the acceleration curve when starting from a stop because you started in the lower, less powerful rpm range. And a slower acceration curve means it takes longer to reach the same distance/speed.
pretty much what Sleeper05 said,
Crazy Al is right about the stored energy. Slipping the clutch from high rpms transfers more of the power that is made at those rpms, so when you go from a stop in a manual and quickly transmit 70% of the engines torque at 2500+ rpms you start in the engine's sweet spot. If you are engaged at 800 rpms, you have to wait for the revs to climb to make and transmit most of the torque. What are the rpms at 5mph, 900-1000rpms? So you have to wait after you went to WOT for the revs to climb and start making good power, hence that waiting time is what makes those 5-60mph times slower. I am no automatic tranny expert but from a stop when you punch the gas, don't the revs climb and once to a certain rpm engage the stall/torque converter? Then you actually start transmitting torque to the rear wheels after your revs are up. However, when you start from a roll, the converter is already engaged so you too have the wait for the revs to climb before your engine starts making good power.
I took physics a long time ago so it's a little rusty, but when you are at 5mph and go WOT your acceleration curve will not be as steep as the acceleration curve when starting from a stop because you started in the lower, less powerful rpm range. And a slower acceration curve means it takes longer to reach the same distance/speed.
Thanks guys- it's really great to have so many knowledgable people here on the MF to answer just about ANY technical question that arises!
I am unfortunately woefully ignorant about any and all such matters, but if any of you ever have questions about hypnosis
(I was a clinical hypnotherapist for 25 years), then maybe I can return the favor someday...
02-23-2007, 03:42 AM
#14
Banned
Join Date: Nov 2006
Posts: 651
RE: 5-60 SLOWER than 0-60- WHY...?!
I would guess 2 reasons:
1. Engine not in powerbad. When they test from a stop, they brake torque autos or drop the clutch on manuals. This is not done in 5-60 times. Cars with a lot of torque down low don't suffer as much as high reving, no torque down low vehicles. Turbo vehicles suffer greatly.
2. The tires will have a lot more traction launching from a stop than they will trying to launch while already moving. You get more weight transfer from a stop which is going to give you better traction. Tires don't seems to tolerate as much power when you are already move and you have to modulate more to keep from lighting them up.
1. Engine not in powerbad. When they test from a stop, they brake torque autos or drop the clutch on manuals. This is not done in 5-60 times. Cars with a lot of torque down low don't suffer as much as high reving, no torque down low vehicles. Turbo vehicles suffer greatly.
2. The tires will have a lot more traction launching from a stop than they will trying to launch while already moving. You get more weight transfer from a stop which is going to give you better traction. Tires don't seems to tolerate as much power when you are already move and you have to modulate more to keep from lighting them up.
02-23-2007, 03:52 AM
#15
2nd Gear Member
Join Date: Jan 2007
Location: Virginia
Posts: 337
RE: 5-60 SLOWER than 0-60- WHY...?!
This is good to know. You could challenge someone to race and tell them that they can have the advantage of a slow rolling start. When they pull alongside you'll take off. Then you kick their *** and they think you spotted them a rolling start. Cool.
02-23-2007, 04:41 AM
#16
5th Gear Member
Join Date: Oct 2006
Location: Baytown, TX
Posts: 3,115
RE: 5-60 SLOWER than 0-60- WHY...?!
the answer is in the launch
I know for me I cut my 1/4 times by about a sec by launching instead of a dead idle to wot run
the Torque converter on 05-06 Mustang GTs fully locks at about 2450RPM so you can rev it just a little short of that at a dead stop with the brake down
but a 5mph your not even close to 2450RPMs so the differanve in energy between 5MPH roll and 2300 RPM is a fair amount
but also you can't rev to 2400 without wheel spin or better tires so they most likely spent time to find the sweet spot or just reved it to 1500
I know for me I cut my 1/4 times by about a sec by launching instead of a dead idle to wot run
the Torque converter on 05-06 Mustang GTs fully locks at about 2450RPM so you can rev it just a little short of that at a dead stop with the brake down
but a 5mph your not even close to 2450RPMs so the differanve in energy between 5MPH roll and 2300 RPM is a fair amount
but also you can't rev to 2400 without wheel spin or better tires so they most likely spent time to find the sweet spot or just reved it to 1500
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