Launching

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UCLAccord
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Launching

Post by UCLAccord »

Sorry for a new post, but I didn't want to bump up a bunch of threads with a few pages to ask a couple of questions about starting from a stop. I don't mean an aggressive, drag racing launch, but just a regular, casual, slow speed launch.

I've read that you should always try to stay above idle when launching. Other than stalling, what harm does it do to the car to launch below idle? Also, wouldn't all no-gas launches drop the RPMs to below idle, since you're starting at idle and not adding gas?

I've read that cars with more torque can launch at a lower RPM and cars with less torque can launch at a higher RPM. In my car, a 4 banger, if I rev to 1500-2000, once the clutch starts to engage, the revs dip to about 750 or idle-ish before picking back up. Is it bad to launch at such a high RPM? If I don't go to such a high RPM, what's my alternative? Do I just need to transition to more of a steady revs launch than a steady gas launch?

Thanks.
Nervous
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Post by Nervous »

Honestly, I HATE the revving to 1500-2k method. I mean, it's GREAT if your new to launching, but after a while, I think the best thing you can do is start to release the clutch and when you hit friction point, you start to give a tiny amount of gas and continue the release of the clutch, not stopping for it to grab or anything, the gas will pick the rev's back up.

When you're launching, you're not really doing any damage to your engine if you're RPM's drop below idle. I mean, alot of people say it's not good..but really, if you can stall the car so many times, putting it below idle is nothing serious. Almost 50% of my launches dip my RPM's under idle, and guess what? I'm still running strong.

But again, this method is after you're used to launching, if your new, I recommend just slipping the clutch a little longer. The RPM's are so low you're not doing anything serious to your clutch.
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Post by hockeystyx16 »

steady gas is good for beginners. it teaches you fine clutch control and only leaves 1 variable (clutch) for you to control. it does have some disadvantages.
1. for a torqueless honda engine like yours, (my honda v6 is pretty weak down low as well, but not as weak as your 4 banger) steady gas will take a week and a half to get the car moving because you need to engage the clutch so gently to not stall.
2. with cars behind you, it will get cars pissed at you. possibly rearended cuz slushies are so impatient. for them, green light means mash the gas

these disadvantages are something you are gonna have to put up with for a little while. depending how fast of a learner you are, you will eventually start feeding in a little gas while clutching out. dont force this. dont start feeding gas before you are comfortable with steady gas launches. let it come naturally when you launch like this, you are basically feeding power thru a slipping clutch, when you are good at it, you can launch quick while staying under 1000 rpms with very fast clutch engagement, this kind of rpms wont wear the clutch. as a novice, its easy to give it too much gas and glaze the clutch, in the long run, if you never learn the right way and keep doing it halfassed (for the lack of a better term :wink: ) will wear the clutch faster. this is why its important to let the gas come to you, not force it.

then you will be able to clutch out and gas in at the same time, and your launches will be much faster.
-Roman
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Prodigal Son
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Re: Launching

Post by Prodigal Son »

UCLAccord wrote: I've read that you should always try to stay above idle when launching.
I've read all sorts of things. Most of them are bunk. So it this.
UCLAccord wrote:Other than stalling, what harm does it do to the car to launch below idle?
I don't know why it is that people associate idle speed with stall speed. They are two quite different things. Why would manufacturers set the idle speeds at stall speed? That would make cars sitting at a light spontaneously stall, which would not be a good thing. Stall speed is a lot lower than idle speed.

Certainly you do not want to let your revs drop below stall speed when launching, because they you would stall. You also do not want to make your engine splutter, choke, labor while launching. But those are not things that happen at a particular RPM level, they are things that can happen at different levels depending on load and throttle. To avoid them, you do not look at your tach, you listen to your engine. If it is unhappy, it will complain. If it does not complain, it's happy.
UCLAccord wrote:Also, wouldn't all no-gas launches drop the RPMs to below idle, since you're starting at idle and not adding gas?
Yup. The entire launch is accomplished between idle speed and stall speed -- thus demonstrating that idle speed is not the same thing as stall speed.
UCLAccord wrote:I've read that cars with more torque can launch at a lower RPM and cars with less torque can launch at a higher RPM.
Yes, but the raw torque number that the manufacturer gives you is peak torque and is usually up around 4000 RPM. What really determines how low you can launch is low-end torque, which probably won't be mentioned in the glossy brochure unless it is really good.
UCLAccord wrote:In my car, a 4 banger, if I rev to 1500-2000, once the clutch starts to engage, the revs dip to about 750 or idle-ish before picking back up. Is it bad to launch at such a high RPM?
This is called the steady gas launch, and when you do this you are not launching at 1500-2000 RPM, you are launching at 750 RPM. The launch happend when the clutch engages and the when the clutch is engaging, the revs are at 750. Personally, I would go just a tad longer on the clutch and not let it dip quite so far, but if your car is comfortable with this launch, and you are too, there is nothing to worry about.

The inescapable fact of launching is that when the clutch starts to engage, it will drag the revs down. There are two ways you can compensate for this. One is to give more revs initially (the steady gas method). The other it to use the gas pedal to raise the revs as the clutch engages (the steady revs or see-saw method).

No matter which one you use, you are still launching at the same revs and with the same amount of power. All that has changed is how you have compensated for the RPM drop when the clutch engages.

One is not better than the other, though steady gas is easier than steady revs. You can do it whichever way is comfortable to you.
UCLAccord wrote: If I don't go to such a high RPM, what's my alternative? Do I just need to transition to more of a steady revs launch than a steady gas launch?
You do not need to change unless you want to. One is not better than the other. They are just different.
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Post by Prodigal Son »

hockeystyx16 wrote: 1. for a torqueless honda engine like yours, (my honda v6 is pretty weak down low as well, but not as weak as your 4 banger) steady gas will take a week and a half to get the car moving because you need to engage the clutch so gently to not stall.
2. with cars behind you, it will get cars pissed at you. possibly rearended cuz slushies are so impatient. for them, green light means mash the gas
Not true. Steady gas is just as quick as steady-revs. In fact, unless you are really proficient at steady-revs, steady-gas is quicker, since steady-revs involves finessing the gas. There is no need to engage the clutch slowly. All you need to do is to set the initial revs at a suitable level for the speed of launch you want.
hockeystyx16 wrote:this kind of rpms wont wear the clutch.
RPMs don't wear the clutch. Torque wears the clutch.
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Nervous
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Post by Nervous »

Prodigal Son wrote:
hockeystyx16 wrote: 1. for a torqueless honda engine like yours, (my honda v6 is pretty weak down low as well, but not as weak as your 4 banger) steady gas will take a week and a half to get the car moving because you need to engage the clutch so gently to not stall.
2. with cars behind you, it will get cars pissed at you. possibly rearended cuz slushies are so impatient. for them, green light means mash the gas
Not true. Steady gas is just as quick as steady-revs. In fact, unless you are really proficient at steady-revs, steady-gas is quicker, since steady-revs involves finessing the gas. There is no need to engage the clutch slowly. All you need to do is to set the initial revs at a suitable level for the speed of launch you want.
hockeystyx16 wrote:this kind of rpms wont wear the clutch.
RPMs don't wear the clutch. Torque wears the clutch.
I gotta disagree with this whole post. I mean, Steady gas is probably slower because once the clutch is engaged, guess what? You're at a lower RPM. If you're proficient at steady rev's, when the clutch is engaged, your rev's are already up there. I use steady rev's all the time to keep it at just about 1k, and it doesn't take much "finessing" or timing, it's just natural for me now.

Edit: If you read what was here..I read it over and I couldn't get the idea out the right way, but whatever. RPM's wear the clutch, and so does Torque of the stationary car. No such thing as harmless RPM's if your clutch is ever slipping.
UCLAccord
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Re: Launching

Post by UCLAccord »

Prodigal Son wrote:
UCLAccord wrote:Other than stalling, what harm does it do to the car to launch below idle?
I don't know why it is that people associate idle speed with stall speed. They are two quite different things. Why would manufacturers set the idle speeds at stall speed? That would make cars sitting at a light spontaneously stall, which would not be a good thing. Stall speed is a lot lower than idle speed.

Certainly you do not want to let your revs drop below stall speed when launching, because they you would stall. You also do not want to make your engine splutter, choke, labor while launching. But those are not things that happen at a particular RPM level, they are things that can happen at different levels depending on load and throttle. To avoid them, you do not look at your tach, you listen to your engine. If it is unhappy, it will complain. If it does not complain, it's happy.
i guess i should clarify this question a bit. there are three scenarios that can happen when you're below idle - 1) stall, because you let the revs drop below stall speed, 2) you get going but your car struggles, bucks, splutters, chokes, labors, etc 3) you get going smoothly. what wear and tear occurs in scenario 1 and 2?
Prodigal Son wrote:
UCLAccord wrote:In my car, a 4 banger, if I rev to 1500-2000, once the clutch starts to engage, the revs dip to about 750 or idle-ish before picking back up. Is it bad to launch at such a high RPM?
This is called the steady gas launch, and when you do this you are not launching at 1500-2000 RPM, you are launching at 750 RPM. The launch happend when the clutch engages and the when the clutch is engaging, the revs are at 750. Personally, I would go just a tad longer on the clutch and not let it dip quite so far, but if your car is comfortable with this launch, and you are too, there is nothing to worry about.

The inescapable fact of launching is that when the clutch starts to engage, it will drag the revs down. There are two ways you can compensate for this. One is to give more revs initially (the steady gas method). The other it to use the gas pedal to raise the revs as the clutch engages (the steady revs or see-saw method).

No matter which one you use, you are still launching at the same revs and with the same amount of power. All that has changed is how you have compensated for the RPM drop when the clutch engages.

One is not better than the other, though steady gas is easier than steady revs. You can do it whichever way is comfortable to you.
so, the launch actually occurs when RPMs dip as the clutch starts to engage? the wear occurs more so during the time you slip the clutch to start to move, right? so, it really doesn't matter what RPM you rev to as long as you don't slip as much? so why do people say rev around this range, etc? does more RPMs = more time slipping the clutch?

and i'm going to go do some more thorough searches on this one, but at what point would you say the clutch is fully synched up and you can stop slipping? is it when the car starts to move, or is there something else that i should try to feel for?

Thanks.
Nervous
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Re: Launching

Post by Nervous »

UCLAccord wrote:
Prodigal Son wrote:
UCLAccord wrote:Other than stalling, what harm does it do to the car to launch below idle?
I don't know why it is that people associate idle speed with stall speed. They are two quite different things. Why would manufacturers set the idle speeds at stall speed? That would make cars sitting at a light spontaneously stall, which would not be a good thing. Stall speed is a lot lower than idle speed.

Certainly you do not want to let your revs drop below stall speed when launching, because they you would stall. You also do not want to make your engine splutter, choke, labor while launching. But those are not things that happen at a particular RPM level, they are things that can happen at different levels depending on load and throttle. To avoid them, you do not look at your tach, you listen to your engine. If it is unhappy, it will complain. If it does not complain, it's happy.
i guess i should clarify this question a bit. there are three scenarios that can happen when you're below idle - 1) stall, because you let the revs drop below stall speed, 2) you get going but your car struggles, bucks, splutters, chokes, labors, etc 3) you get going smoothly. what wear and tear occurs in scenario 1 and 2?
Prodigal Son wrote:
UCLAccord wrote:In my car, a 4 banger, if I rev to 1500-2000, once the clutch starts to engage, the revs dip to about 750 or idle-ish before picking back up. Is it bad to launch at such a high RPM?
This is called the steady gas launch, and when you do this you are not launching at 1500-2000 RPM, you are launching at 750 RPM. The launch happend when the clutch engages and the when the clutch is engaging, the revs are at 750. Personally, I would go just a tad longer on the clutch and not let it dip quite so far, but if your car is comfortable with this launch, and you are too, there is nothing to worry about.

The inescapable fact of launching is that when the clutch starts to engage, it will drag the revs down. There are two ways you can compensate for this. One is to give more revs initially (the steady gas method). The other it to use the gas pedal to raise the revs as the clutch engages (the steady revs or see-saw method).

No matter which one you use, you are still launching at the same revs and with the same amount of power. All that has changed is how you have compensated for the RPM drop when the clutch engages.

One is not better than the other, though steady gas is easier than steady revs. You can do it whichever way is comfortable to you.
so, the launch actually occurs when RPMs dip as the clutch starts to engage? the wear occurs more so during the time you slip the clutch to start to move, right? so, it really doesn't matter what RPM you rev to as long as you don't slip as much? so why do people say rev around this range, etc? does more RPMs = more time slipping the clutch?

and i'm going to go do some more thorough searches on this one, but at what point would you say the clutch is fully synched up and you can stop slipping? is it when the car starts to move, or is there something else that i should try to feel for?

Thanks.
Rule of Thumb: Clutch is FULLY engaged when your foot is OFF the pedal. (Don't mind the Freeplay...)
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Post by Prodigal Son »

Nervous wrote: I gotta disagree with this whole post. I mean, Steady gas is probably slower because once the clutch is engaged, guess what? You're at a lower RPM.
You are at a lower RPM than you initially set the revs to. You are at the same RPM you would have been at if you had done the launch as a steady-revs.

Nervous wrote:If you're proficient at steady rev's, when the clutch is engaged, your rev's are already up there.
At the point at which the clutch is hooked up, the revs are at the same level no matter which launch you use. The difference is only in whether you compensate for the rev drop before you engage the clutch or while you are engaging the clutch. Once the clutch is engaged, you are at the same revs no matter which approach you use.
Nervous wrote:I use steady rev's all the time to keep it at just about 1k, and it doesn't take much "finessing" or timing, it's just natural for me now.
Naturally the method you use most often will seem the quickest and most natural to you. That does not mean that it is inherently quicker or more natural, just that you are more practiced in it.

I've done both styles over the 20+ years I have driven stick. I'm proficient in both. I find steady gas quicker by a hair. But it is not enough of a difference to use as the basis of your decisions about which one to use.
Nervous wrote: No such thing as harmless RPM's if your clutch is ever slipping.
No, but it is torque that does the real damage. Try rubbing your hands together lightly. Then try rubbing them at the same speed only pressing hard. Which one generates the most heat? Torque is what kills you.
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Post by Nervous »

Prodigal Son wrote:
Nervous wrote: I gotta disagree with this whole post. I mean, Steady gas is probably slower because once the clutch is engaged, guess what? You're at a lower RPM.
You are at a lower RPM than you initially set the revs to. You are at the same RPM you would have been at if you had done the launch as a steady-revs.

Nervous wrote:If you're proficient at steady rev's, when the clutch is engaged, your rev's are already up there.
At the point at which the clutch is hooked up, the revs are at the same level no matter which launch you use. The difference is only in whether you compensate for the rev drop before you engage the clutch or while you are engaging the clutch. Once the clutch is engaged, you are at the same revs no matter which approach you use.
Nervous wrote:I use steady rev's all the time to keep it at just about 1k, and it doesn't take much "finessing" or timing, it's just natural for me now.
Naturally the method you use most often will seem the quickest and most natural to you. That does not mean that it is inherently quicker or more natural, just that you are more practiced in it.

I've done both styles over the 20+ years I have driven stick. I'm proficient in both. I find steady gas quicker by a hair. But it is not enough of a difference to use as the basis of your decisions about which one to use.
Nervous wrote: No such thing as harmless RPM's if your clutch is ever slipping.
No, but it is torque that does the real damage. Try rubbing your hands together lightly. Then try rubbing them at the same speed only pressing hard. Which one generates the most heat? Torque is what kills you.
First off...either I'm Confused, or your Confused. You DON'T end up at the same rev's if you do steady gas vs steady rev's.

You only end up at the same rev's if you steady gas and slip the clutch longer, which is slowing down your launch. If you use steady rev's you have the ability to release the clutch as fast as you can give gas, and therefore can be done instantly, or as slow as you want.

As for the Torque comment, I'm trying to think about it but I ain't in the mood, but I will come up with an answer, whether it agree's with your or not!
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Re: Launching

Post by Prodigal Son »

UCLAccord wrote:i guess i should clarify this question a bit. there are three scenarios that can happen when you're below idle - 1) stall, because you let the revs drop below stall speed, 2) you get going but your car struggles, bucks, splutters, chokes, labors, etc 3) you get going smoothly. what wear and tear occurs in scenario 1 and 2?
Not too much if you don't do it to often. But obviously the reason that you avoid stalling and struggling is not because of wear but because it is no way to drive. If you get your car going smartly, not taking more than a couple of seconds to launch, and not peeling out, you will be fine and your car will be fine.
UCLAccord wrote: so, the launch actually occurs when RPMs dip as the clutch starts to engage?
Yes. That dip in RPM occurs because the engine is running free with no load and as you engage the clutch you put the entire weight of the car on the engine. If you put all that weight on instantaneously, you would just stall the engine, so you have to put it on gradually by slipping the clutch. The faster you release the clutch, the more quickly you transfer the weight to engine, and the lower the revs will drop.
UCLAccord wrote:the wear occurs more so during the time you slip the clutch to start to move, right? so, it really doesn't matter what RPM you rev to as long as you don't slip as much?
The wear occurs when the clutch is slipping the torque of the stationary car against the torque of the engine under power. The wear is proportional to the amount of torque transferred, not the amount of time it takes to make the transfer.
UCLAccord wrote:so why do people say rev around this range, etc? does more RPMs = more time slipping the clutch?
The higher the RPMs at the time the clutch is engaging, the more torque is being transferred through the slipping clutch, and thus the more wear occurs. Choosing a steady-rev vs. a steady-gas launch does not make any material difference. It is the revs at which the actual engagement takes place that matter.

Even so, if you are not jack rabbiting every start, you really don't have anything to worry about. Just get the car hooked up quickly and smoothly and drive. You are not going to kill your clutch. If you fret about it too much, though, you may kill your enjoyment of driving.
UCLAccord wrote: at what point would you say the clutch is fully synched up and you can stop slipping? is it when the car starts to move, or is there something else that i should try to feel for?
The clutch is a friction coupling. It stops slipping when its friction overcomes the torque differential between the engine and the transmission, neither sooner nor later.

You, through the clutch pedal, control the amount of force with which the clutch is pressed against the flywheel, which increases the friction, which speeds up the equalization of torque. But there is no one point in the clutch travel when the clutch must stop slipping. If there is no torque differential, the clutch will stop slipping even if very little pressure is applied. If the torque differential is high enough, it may continue slipping even after your foot is off the pedal.

But your job is not to figure out when the clutch has stopped slipping. Your job is simply to get your foot off the clutch pedal as quickly as you possibly can without stalling the car. NEVER pause in your clutch release. Always keep the clutch pedal coming up as quickly as you can without bogging down the car. Do that and you do not need to worry about when the clutch stops slipping.
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Post by Prodigal Son »

Nervous wrote: First off...either I'm Confused, or your Confused. You DON'T end up at the same rev's if you do steady gas vs steady rev's.

You only end up at the same rev's if you steady gas and slip the clutch longer, which is slowing down your launch. If you use steady rev's you have the ability to release the clutch as fast as you can give gas, and therefore can be done instantly, or as slow as you want.
I think you are confusing steady gas with no gas. Compare the scenarios:

Target is to launch at 1000 RPM (BTW, setting launch RPM targets is silly -- you should focus on the car not the tach)

Steady revs: Set the revs at 1000. Begin to engage clutch. Revs start to drop. Add gas to keep revs at 1000. Repeat until engaged. Result: car launches at 1000 RPM.

Steady gas: Set the revs to 1800 and hold the gas steady. Begin to bring up the clutch. Revs drop to 1000. Clutch hooks up. Result: car launches at 1000 RPM.

Steady revs can be as quick as steady gas, but only if you modulate the gas just right to prevent the revs ever falling below 1000. If they fall below your target your launch will be slower. Conversely, if you let them creep up, you will delay the engagement, accelerate through the slipping clutch, and wear the clutch more.

Done correctly both are quick, efficient, and easy on the equipment. But there is more to go wrong in a steady-revs launch.
Nervous wrote:As for the Torque comment, I'm trying to think about it but I ain't in the mood, but I will come up with an answer, whether it agree's with your or not!
I'm rubbing my hands together in anticipation! :lol:
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Post by eaglecatcher »

I may have a somewhat noob launch still, but it works for me. The way I do it, is I rev to about 1200 or so, and then I let the clutch out and add gas, keeping the revs steady. The faster I let out the clutch, the more gas I give. The slower, the less, etc. It works really good for me, because when I get it down just right, I slip the clutch for very little time, it practically hooks up immediately.
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UCLAccord
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Re: Launching

Post by UCLAccord »

I'm glad I signed up and started posting. I learned a lot as a lurker, and it helped me get through my first week (this is my second), but asking questions has engaged my brain more and i think i'm starting to understand better.
Prodigal Son wrote:
UCLAccord wrote:so why do people say rev around this range, etc? does more RPMs = more time slipping the clutch?
The higher the RPMs at the time the clutch is engaging, the more torque is being transferred through the slipping clutch, and thus the more wear occurs. Choosing a steady-rev vs. a steady-gas launch does not make any material difference. It is the revs at which the actual engagement takes place that matter.

Even so, if you are not jack rabbiting every start, you really don't have anything to worry about. Just get the car hooked up quickly and smoothly and drive. You are not going to kill your clutch. If you fret about it too much, though, you may kill your enjoyment of driving.
Steady rev - rev to 1k and keep them there by adding gas as necessary, car moves
Steady gas - rev to 2k, bring clutch to FP, RPM drops to 700, car moves

would you consider the actual engagement at 1000 and 700, respectively? would steady gas then lead to less wear? or are you considering the actual engagement as whatever RPM you are at when you are fully off the clutch?

Hooked up = car in motion from standstill?
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Post by Ecmslee »

"Hooked up" means that the flywheel and clutch are fully synchronized. At this point you can even dump the clutch pedal and incur no wear since the rate that the clutch is spinning at matches the rate of the flywheel, thus no more slip.
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