Perfect Shifting?

[Scaff]

Ok, well my point is that Lethalchem was saying that you lose time because you have to break earlier. I was saying that is simply not the case.

Now, as far as reasons to do it. I like the overall smoothness that I get from it. I do it that way because when I drive, especially with others in the car, I want it to be smooth. I hate jerking people around in the car.

As I previously stated, the other way makes good sense when you have an extremely short throw. But think about it, as your depressing the throttle, you let up the clutch, then putting the clutch back in as you let off the gas and downshift to desired gear. It may be an extra step, but there is no time lost that I can see. Especially since you only need to put the clutch half down to get out of gear.

Don't disagree with you doing it if you want to, and you will note that I'm not saying it is that much (if at all) slower.

With regard to smoothness, if you heel and toe (without double clutching) correctly it is smooth. Thats the point, you match the engine revs to speed as you change down, thus avoiding any engine brakeing when you finish braking. You do not need to double clutch to achieve this level of smoothness.

Sorry, but I still do not see the reason (other than as I said, personal preference) to do it, yet in your post you clearly say

'There's plenty of reason to do it'

In regard to the extra step, as I say I do not dispute the speed issue (as we will never be able to prove it), but any process that contains unnecessary (as I see them) steps, leads to additional chances of an error occuring. To my mind I would remove them.

It an opinion, and everyone is entitled to one, but I do have to say you are the only person I have ever heard of who double clutches while heel and toe downshifting.

 

[Swift]

Don't disagree with you doing it if you want to, and you will note that I'm not saying it is that much (if at all) slower.

With regard to smoothness, if you heel and toe (without double clutching) correctly it is smooth. Thats the point, you match the engine revs to speed as you change down, thus avoiding any engine brakeing when you finish braking. You do not need to double clutch to achieve this level of smoothness.

Sorry, but I still do not see the reason (other than as I said, personal preference) to do it, yet in your post you clearly say

In regard to the extra step, as I say I do not dispute the speed issue (as we will never be able to prove it), but any process that contains unnecessary (as I see them) steps, leads to additional chances of an error occuring. To my mind I would remove them.

It an opinion, and everyone is entitled to one, but I do have to say you are the only person I have ever heard of who double clutches while heel and toe downshifting.

Well, that's the way I was tought and on a car with a longer throw it makes very good sense. YOu don't need to keep the clutch down as long AND reve the engine as high.

It's really all about how long you have to keep the clutch in. The longer it's down, the harder the timing.

 

[Scaff]

Well, that's the way I was tought and on a car with a longer throw it makes very good sense. YOu don't need to keep the clutch down as long AND reve the engine as high.

It's really all about how long you have to keep the clutch in. The longer it's down, the harder the timing.

Well, I must confess I have never had a problem with heel and toe downshifts due to the length of throw in a car.

The only problems I have come across in a car, is that some pedal layouts can make it difficult, if not impossible to heel and toe. For example, the Audi RS6 Avant has the brake pedal set about an inch higher that the throttle (quite a common Audi trait), this make Heel and Toe almost impossible. Its still a damn fast car, but this factor disapointed my no end and to a large degree spoilt the car for me.

Swift, I think that you and I will have to agree to disagree on this one (and its not really much of a disagreement), I still do not see the need to double clutch when heel and toe downshifting.

Now this may be down to a difference in our driving styles, driving position, etc; but personally I have never had a need to use a technique like this and have trouble imagining when I would in the future (on road or track).

 

[cubits]

YOu don't need to keep the clutch down as long AND reve the engine as high.

The shorter the shift time, the higher the revs need to go. Common sense that if you shift into the lower gear at higher speed, the engine needs to spin faster. The longer you take, the more the car slows (if you're braking) and the lower the revs need to go.

About the double clutching, i used to be able to not bother with it in the swift. I could take the car out of gear easily enough without the clutch and clutch to put it in the next gear. If i was shifting sans clutch, i'd blip just after i moved the stick out and feel it into the next gear as the revs changed. There is a very obvious point where the stick gets sucked into the slot (easier with a solid gearbox linkage), which you can find quite fast if done right, and avoid blind leaps of faith.

I actually upshifted without the clutch a few times too, although a clutchless upshift is mostly pointless, and a little clunky.

When using heel-toe, i am on the move with the stick at the same time as i am with the clutch, basically blending the half press into the full press.

 

[Swift]

The shorter the shift time, the higher the revs need to go. Common sense that if you shift into the lower gear at higher speed, the engine needs to spin faster. The longer you take, the more the car slows (if you're braking) and the lower the revs need to go.

When using heel-toe, i am on the move with the stick at the same time as i am with the clutch, basically blending the half press into the full press.

Uh, the speed of the engine that you need is detirmined by your current speed. The common thought is to weight till you've done 75-80% of the braking then downshift to avoid multiple downshifts and the like. What technique you use to downshift doesn't effect the actual RPM's needed to match the transmission, just the timing of it. So if I do my technique at the same time that Scaff does his, our RPM's needed for a smooth shift are going to be almost identical.

 

[Jmac279]

About shifting...

I remember my VW GOL (yes, gol, without "f"). The manual said the optimal RPM for shifting was 5650. The red line is 6150-8000.

I noticed that some cars starts to lose acceleration when too near of the red line. Just like an inverse log function, a limit equation. The accel only drops to negative when the fuel cut occurs in high rpms.

So, if GT4 is the RDS, it should match the real cars optimal point of shifting. Forget the silly NFSU style (when it reaches that red point, shift). Each car should have its ideal shift point without considering the red line, that is just there to indicate an overrotation of engine.

The optimum shift point typically isn't the same for each gear, unfortunately ...

In order to figure out optimum shift points, you need a calculator and a dyno graph ... Then you basically calculate the force at each 100 RPM in each gear ... Basically you want to shift at a point where the Force in say 2nd is slightly greater than the Force in 3rd ... You'll need to calculate the RPM change shifting from 2nd into 3rd (RPMs will be lower in 3rd) ... If the Force in 2nd at the rev-limiter is greater than at any point in 3rd, then you should shift just prior to the rev limiter for maximum acceleration ...

Force (lbs) = Wheel Torque (lb-ft) * Gear Ratio * Final Drive Ratio * 24 / Tire Diamater (outer, in)
Force (N) = Wheel Torque (Nm) * Gear Ratio * Final Drive Ratio * 200 / Tire Diameter (outer, cm)
Tire Diameter (outer, cm) = Rim Diameter (in) * 2.54 + 0.2 * Width (mm) * Profile (%)
Tire Diameter (outer, in) = Rim Diameter (in) + 2 * Width (mm) * Profile (%) / 25.4
Example = P205/50R15 Tires ... 205 = Width (mm), 50 = Profile (%) and 15 = Rim Diameter (in) ... 15*2.54 + 0.2*205*0.50 = 58.6 cm ... 15 + 2*205*0.5/25.4 = 23.07086614" ... To verify, 23.07086614*2.54 = 58.6 cm
MPH = RPM * Diameter (outer, in) / (Gear Ratio * Final Drive Ratio * 336)
KM/H = RPM * Diameter (outer, cm) / (Gear Ratio * Final Drive Ratio * 530.30303...)
RPM = MPH * Gear Ratio * Final Drive Ratio * 336 / Diameter (outer, in)
RPM = KM/H * Gear Ratio * Final Drive Ratio * 530.303... / Diameter (outer, cm)
Diameter (outer, in) = MPH * Gear Ratio * Final Drive Ratio * 336 / RPM
Diameter (outer, cm) = KM/H * Gear Ratio * Final Drive Ratio * 530.303... / RPM

 

[Jmac279]

If you put a car on the dyno, the wheels act like giant propellors, stirring the air. Any extra drag here resists power, and hence reduces power at the wheels.

Never thought of it like that ... Makes sense, though

 

[cubits]

Yes, your current speed, which is decreasing while you shift. The shorter you make the shift, the higher you will need to be revving (because at the time of gear meshing, the car will be travelling faster than if you took longer to shift). That's all i meant.

 

[MasterGT]

Thats a good question, I never really know what torque is in relation to horsepower. If somone could explain exactly what torque is that would be great

Power is how fast you hit the barn.
Torque is how far you can pull the barn off its foundation.

I think Jay Leno's Tank Car is a good example, since it has huge torque in relation to power. It only will go so fast, but look at what the engine could pull (a 110,000 lb fully loaded tank).

Cheers,

MasterGT

 

[cubits]

WRC cars have only got 300hp but can do 0-100 in under 3 seconds on tarmac. Probably because they have a pretty flat 600'ish Nm of torque from 1500rpm to about 5000rpm. Vrooooom!

 

[Jmac279]

WRC cars have only got 300hp but can do 0-100 in under 3 seconds on tarmac. Probably because they have a pretty flat 600'ish Nm of torque from 1500rpm to about 5000rpm. Vrooooom!

That's probably due to a flat power curve (torque isn't limited, so they make as much torque as possible at each RPM while staying below 300 hp), wicked traction, and proper gearing, IMO ...

A flat torque curve would mean it would only be 300 hp at 1 point ... However, if torque peaked severely at a low RPM and gradually dropped off, you could get a flat power curve ...

 

[chameleon2]

Uhmmm...all the time. Unless we've got our definitions crossed, heel-toe shifting has nothing to do with double clutching. Perhaps we're not on the same page concerning what double clutcing is?

This is how I think about it:
Changing gears in really old cars, like how it was used to be, required synchronizing. This was done by double clutching and rev matching by heel and toe. With the arrival of the synchromeshes double clutching wasn't needed anymore. Commen sense proves that synchros are well designed to take a blow, cause if almost everyone learns driving without the need to double clutch and most importantly rev matchin, the regular person puts pretty huge forces on m at at all times. I suppose manufactorers take this into account when designing the gearbox. This confirms the theory that double clutch is not really needed, with heel and toe the synchromeshes have to work a lot less harder, but the minimal work they have to do will cause minimal wear. I don't know anyone in my area that heel en toe's, let alone double clutching, none of the people I know, even know what it is. So many people I know do shift down when braking, but do pure engine braking. If they can drive their gearboxes 100.000 km + without a broken gearbox or something, double clutching is not really needed. It does make the job seem to go smoother, at the expense of a lot of extra work. Like you said it, in an enduro I would be worn out a lot faster than the synchros. Plus the fact that if you need to do hard braking before a corner and shift from 5th to 2nd, you'd be dumping the clutch 6 times, while it could be done with 3. The last two days I've purposedly left out the double clutching, and all of a sudden the heel and toe is so much easier. It might not feel as smooth as when double clutching but the timing and such is much easier and such little work now to downshift. And it sounds a lot better too When double clutching I couldn't always get the rpms perfectly matched (without a tacho yea), because if you're off a bit it was obvious to hear and feel. Learning to properly double clutch, then leave it out again, sortof feels like starting a game in hard mode, the after completing it you play the game on easy. Might sound weird but it did help me, especially for the right amount of throttle. I can get to no other conclusion than that people double clutch because they find it a fun thing to do. But effective in time and racing? No not really.....

The amount of slip? I'm not sure what you mean by that. The only time I slip a clutch is when launching at the drags or at the begining of an autocross run. Do you mean rev-matching?

Yea sorry I was a bit unclear, I left out "from the point of standing still" I'd like to decrease the amount of slip as much as possible, cause in that audi which is from my moms, from standing still she's always let the clutch slipping until it grabs. There's a lot of slipping! and I see 90% of the people doing it. Just mind your average john doe at the traffic lights, open the window or something and listen to their engines. Now what I noticed in that audi, that after 80.000 km the gear lever doesn't go in 1st as smooth as it used to go. I suppose this is what is said here about worn out synchros and 1st gear being the biggest ratio difference, it makes sense that when wearing out the 1st gear is up first. So I suppose if she wouldn't have slipped the clutch as much, she wouldn't have this problem?

You don't have a tach?? I can't see doing any kind of performance driving successfully without one.

Whahah can you imagine how good I am!! HAHA JK I really miss it though, but I'll manage. You'll get used to it if you don't have one. (I have an analog clock there)

When hell-toe shifting, you're not having to match the rpms perfectly, you're just blipping it up high enough that the engine isn't going to be dragged down when the clutch is released. This can upset the balance of a car when braking to get set up for a turn.

Well, if give to little it'll drag down like you said. If i put in a little too much you'll feel it getting a little blow. Which makes me wonder, which is worse, too less throthle or too much. I assume it's too much, giving the gears a bigger blow than dragging it down.

BTW, GT4's clutch always does heel en toe, doesn't it?

I guess the bottomline is, double clutching isn't necessary, it's fun and it doens't wear out your synchros, but they're very strong and won't wear out if you heel and toe all the time. I also looked a lot at the footwork of the BM drivers, and I've only seen Gan-san do it once attacking the nismo skyline I guess he was so pre-occupied focusing on the attack, he shifted as how he used to shift most of his life. If performed right it does look crazy though At least I'm skipping practising it, I've done it for six months, didn't perfect the technique but at least know how to properly perform it. None of the pro drivers I've ever seen do it, so I don't see no need for it anymore. Thanks for enlightning me It did help me perfecting the amount to blip though

The only problems I have come across in a car, is that some pedal layouts can make it difficult, if not impossible to heel and toe. For example, the Audi RS6 Avant has the brake pedal set about an inch higher that the throttle (quite a common Audi trait), this make Heel and Toe almost impossible.

Right, that's it. The pedal placement. I have the same in an A4. It's very much possible to do it, though, but because the brake pedal is a little higher, plus that it has strong brakes, there's little time span to (practise) heel and toe, all must be done pretty good or you'll mess up.

 

[chameleon2]

That's probably due to a flat power curve (torque isn't limited, so they make as much torque as possible at each RPM while staying below 300 hp), wicked traction, and proper gearing, IMO ...

A flat torque curve would mean it would only be 300 hp at 1 point ... However, if torque peaked severely at a low RPM and gradually dropped off, you could get a flat power curve ...

I don't get it.....'mean I'm trying to get what you're saying, but I don't. Torque and power are sort of in relation aren't they? Isn't torque just how they divide the HP over the powerband? I mean I'm willing to believe you about getting a flat power curve by having peak torque at low rpm gradually dropping off, but wouldn't that mean that high revving is never needed in WRC cars?

 

[Jmac279]

I don't get it.....'mean I'm trying to get what you're saying, but I don't. Torque and power are sort of in relation aren't they? Isn't torque just how they divide the HP over the powerband? I mean I'm willing to believe you about getting a flat power curve by having peak torque at low rpm gradually dropping off, but wouldn't that mean that high revving is never needed in WRC cars?

Horsepower = Torque (lb-ft)*RPM/5252

So if you have 300 hp from say 4000 RPM to 8000 RPM, torque at 4000 RPM would be ...

300 = Torque (lb-ft) *4000/5252
300*5252/4000 = 393.9 lb-ft

At 8000 RPM, torque would be down to ...

300 = Torque (lb-ft) * 8000/5252
300*5252/8000 = 196.95 lb-ft

So Torque has dropped by half, but Horsepower remains the same ...

Now, to get to your question... A higher-revving engine would allow a higher gear ratio to achieve the same speed, which translates into more force ...

Force (lbs) = Wheel Torque (lb-ft) * Gear Ratio * Final Drive Ratio * 24 / Tire Diamater (outer, in)

MPH = RPM * Diameter (outer, in) / (Gear Ratio * Final Drive Ratio * 336)

At 60 MPH at 4000 RPM with a 2 foot diameter tire and a 4.0 final drive ratio ...

60 = 4000*24/(GR*4*336)
GR = 4000*24/(24*4*336)
GR = 1.190

At 60 MPH at 8000 RPM with a 2 foot diameter tire and a 4.0 final drive ratio ...

GR = 8000*24/(60*4*336)
GR = 2.381

As you can see, the gear ratio has doubled and, therefore, Force will be be the same (196.95 * 2 = 393.9 *1) ...

So Force would be equal at those RPMs with their respective gear ratios, but AVERAGE Force would be greater with the higher-revving engine ...

At 4000 RPM with the 1.190 gear ratio, Force would be ...

Force (lbs) = 393.9*1.19*4*24/24
Force = 1874.964 lbs

At 4000 RPM with the 2.381 gear ratio, Force would be ...

Force (lbs) = 393.9*2.381*4*24/24
Force = 3751.5036 lbs

So Force will have doubled at 4000 RPM and will be equal at 8000 RPM, meaning a much greater Force (1.5x more average Force to be exact) than the PEAK force of the engine shifted at 4000 RPM ...

And, since Acceleration = Force/Mass, 1.5x more Force = 1.5x greater acceleration

 

[kikie]

from standing still she's always let the clutch slipping until it grabs. There's a lot of slipping! and I see 90% of the people doing it. Just mind your average john doe at the traffic lights, open the window or something and listen to their engines. Now what I noticed in that audi, that after 80.000 km the gear lever doesn't go in 1st as smooth as it used to go. I suppose this is what is said here about worn out synchros and 1st gear being the biggest ratio difference, it makes sense that when wearing out the 1st gear is up first. So I suppose if she wouldn't have slipped the clutch as much, she wouldn't have this problem?

Also standing still in first gear, pushing down the clutch all the time is also very demanding on a certain part of the clutch. It is better to put the car in neutral when standing still.

I still have to use double clutching every day. The fifth gear in the "vehicle" I have to drive every day is busted. I have to use double clutching every day, just for the fifth gear. I push down the clutch , put in neutral, blip the throttle, push down the clutch again and voilà, I've fifth gear. After blibbing the throttle you can't wait too long, otherwise the RPM will drop too far.

 

[Swift]

Yes, your current speed, which is decreasing while you shift. The shorter you make the shift, the higher you will need to be revving (because at the time of gear meshing, the car will be travelling faster than if you took longer to shift). That's all i meant.

Uh, no. You seem to not understand the way to double clutch. The only difference is that I put the clutch in again before I put the car in gear. The speed doesn't have to be any different for the engine or the transmission. It's about the timing.

BTW, technically, with my technique, you'd take LONGER to shift. So, your theory would be reversed would it be true.

 

[Lethalchem]

Just about any of the video links on that page contain foot-cam shots, just thought you were after some footage.

However, from what I can remember in none of them do you see ant driver double-clutching on a heel and toe downshift.

Exactly, that's what I thought. Hopefully Swift will watch them himself. Thanks for showing some examples of what I've been trying to say to thi sguy. 👍

Swift, as for your statement about racing technique and daily driving, I recall stating several posts back that when shifting for daily driving purposes, it's really all about driver preference. Personally, I don't bother with any sort of heel-toe action at all when I'm just driving around town, let alone obsolete double-clutching.

 

[Track_Veteran]

Horsepower = Torque (lb-ft)*RPM/5252

So if you have 300 hp from say 4000 RPM to 8000 RPM, torque at 4000 RPM would be ...

300 = Torque (lb-ft) *4000/5252
300*5252/4000 = 393.9 lb-ft

At 8000 RPM, torque would be down to ...

300 = Torque (lb-ft) * 8000/5252
300*5252/8000 = 196.95 lb-ft

So Torque has dropped by half, but Horsepower remains the same ...

Now, to get to your question... A higher-revving engine would allow a higher gear ratio to achieve the same speed, which translates into more force ...

Force (lbs) = Wheel Torque (lb-ft) * Gear Ratio * Final Drive Ratio * 24 / Tire Diamater (outer, in)

MPH = RPM * Diameter (outer, in) / (Gear Ratio * Final Drive Ratio * 336)

At 60 MPH at 4000 RPM with a 2 foot diameter tire and a 4.0 final drive ratio ...

60 = 4000*24/(GR*4*336)
GR = 4000*24/(24*4*336)
GR = 1.190

At 60 MPH at 8000 RPM with a 2 foot diameter tire and a 4.0 final drive ratio ...

GR = 8000*24/(60*4*336)
GR = 2.381

As you can see, the gear ratio has doubled and, therefore, Force will be be the same (196.95 * 2 = 393.9 *1) ...

So Force would be equal at those RPMs with their respective gear ratios, but AVERAGE Force would be greater with the higher-revving engine ...

At 4000 RPM with the 1.190 gear ratio, Force would be ...

Force (lbs) = 393.9*1.19*4*24/24
Force = 1874.964 lbs

At 4000 RPM with the 2.381 gear ratio, Force would be ...

Force (lbs) = 393.9*2.381*4*24/24
Force = 3751.5036 lbs

So Force will have doubled at 4000 RPM and will be equal at 8000 RPM, meaning a much greater Force (1.5x more average Force to be exact) than the PEAK force of the engine shifted at 4000 RPM ...

And, since Acceleration = Force/Mass, 1.5x more Force = 1.5x greater acceleration

To expand a little...

The whole object of racing is to maximize the amount of torque to the wheels for the maximum amount of time. This is done with gears. Gears are torque multipliers. They give a motor a mechanical advantage. Imagine gears working like this: You are trying to turn a ratchet. Your hand is all the way by the socket. Even by using your maximum force, the bolt won't turn. Now move your hand to the end of the handle. By using less than your maximum force the bolt will turn.

Torque is the amount of twisting force the motor can apply to the crankshaft and horsepower is the amount of work the motor can perform over time (rpm).

The torque at wheels of the car or truck is what gets the vehicle moving. The torque at the engine crankshaft is multiplied (increased) to the wheels by an amount equal to the gear ratio in the transmission. Thus, the torque at the wheels of the car is much higher than the torque generated at the engine crankshaft. For example, take a gear ratio that is 8.55:1 in first gear, the torque being delivered to the wheels is equal to this number multiplied
by the engine torque at whatever RPM you're at. It's actually a little lower than that because energy is lost through the transmission, commonly refered to as mechanical or parasitic loss, however, you get the point.

Suppose the engine RPM is 5600 RPM, then the maximum speed the car can go in first gear is equal to 5600 divided by 8.55 (the gear ratio), which equals 655 RPM, or 50 mph. This 655 RPM is how fast the wheels are rotating, and based on the size of the tire, this translates into a forward speed of 50 mph for the car. And from 0-50 mph, the torque being generated at the wheels of the car is equal to gear ratio (8.55) multiplied by the engine torque. As you go up in gear, the gear ratio decreases so that the torque delivered to the wheels is less.

Now again, for racing or acceleration, you want to maximize the amount of torque at the wheels for the longest period of time. Without going into a lengthy explanation, you achieve this by using an engine that makes alot of torque at high RPM, i.e, horsepower according to the famous equation relating torque to horsepower. mentioned above. Since these values cross at 5252 rpms, torque will be higher than horsepower below that number and horsepower will be higher than torque above that number. Ever wonder why old muscle cars have higher torque ratings vs horsepower ratings? Bingo- low redlines. But of course peak numbers don't tell the whole story.

Having an engine that makes alot of torque at high RPM (i.e, hp) means that you can do either:
(1) Have high gear ratios in your transmission, which means the torque delivered to the wheels is high because the transmission is increasing the engine torque by a large factor (for example., 15:1 in 1st gear in a honda S2000), or
(2) Stay in the lower gears at higher speeds since your redline is very high. Since the gear ratios are higher in the lower gears, the torque at the wheels will be higher as well, and thus, you accelerate quicker.

Trucks are not designed to go fast at high speeds, nor are they designed to accelerate quickly. They must, however, move a large amount of mass from a standstill, and thus have engines that make alot of engine torque at low RPM's. However, because of the fact that they make low horsepower and have a low redline, the torque generated at the wheels of the truck decreases rapidly as their speed increases. That's okay though, it's a truck. It's not meant to "let's go from a roll".

At the other extreme, F1 and Indy Cart racing cars have very high horsepower (~800 hp) and low engine torque (~250 ft-lbs). However, because these engines
generate their engine torque at high RPM's (~14,000 RPM), they can use high gear ratios so that the torque generated at the wheels is VERY high.
Conversely, they can use low gear ratios, which means they can stay in the lower gears at much higher speeds. Either way, the torque being delivered
the the wheels of the car from 0-150 mph is much higher than if they had an engine that made 250 hp and 800 ft-lbs.

Ok, I'm done blabbing.


BTW - Good post jmac

 

[Lethalchem]

Ok, well my point is that Lethalchem was saying that you lose time because you have to break earlier. I was saying that is simply not the case.

Now, as far as reasons to do it. I like the overall smoothness that I get from it. I do it that way because when I drive, especially with others in the car, I want it to be smooth. I hate jerking people around in the car.

As I previously stated, the other way makes good sense when you have an extremely short throw. But think about it, as your depressing the throttle, you let up the clutch, then putting the clutch back in as you let off the gas and downshift to desired gear. It may be an extra step, but there is no time lost that I can see. Especially since you only need to put the clutch half down to get out of gear.

That was only one very small aspect of my main point. 💡

 

[MasterGT]

Re: perfect shifting

I've asked about this before, but never got an answer, so I was hoping someone would have brought it up in this thread already.

When using the manual transmission and changing down a gear, in the game, I frequently make the engine hit the rev limiter. I've only been using manual for a few months, but I haven't figured this out yet.

What am I doing wrong? How do I control this?

 

[G.T]

Re: perfect shifting

I've asked about this before, but never got an answer, so I was hoping someone would have brought it up in this thread already.

When using the manual transmission and changing down a gear, in the game, I frequently make the engine hit the rev limiter. I've only been using manual for a few months, but I haven't figured this out yet.

What am I doing wrong? How do I control this?

Experience is a good friend. It looks like some people can't get used to manual gears at all and some people get used to it straight away like me.

One thing that might help is remember what the engine sounds like before you change down a gear, making sure it's not revving so much it hits the limiter.

 

[Jmac279]

Re: perfect shifting

I've asked about this before, but never got an answer, so I was hoping someone would have brought it up in this thread already.

When using the manual transmission and changing down a gear, in the game, I frequently make the engine hit the rev limiter. I've only been using manual for a few months, but I haven't figured this out yet.

What am I doing wrong? How do I control this?

Example Car Specs ...

Rev-Limit - 7500 RPM
Final Drive Ratio - 4
Tire Diameter - 24"
Gear Ratios ... 1st - 3 ... 2nd - 2 ... 3rd - 1

So you're travelling at 125 MPH in 3rd gear and you need to brake down to 30 MPH, so you want to be in 1st gear for the corner ...

You don't want to hit the rev-limiter as it will cause your tires to lock up temporarily, reducing brake power and control ...

So you want to shift so that you hit 2nd just below the rev-limt of 7500 RPM and same when you downshift from 2nd to 1st ...

MPH = RPM * Tire Diameter (outer, in) / (Gear Ratio * Final Drive Ratio * 336)
MPH = 7250*24/(2*4*336)
MPH = 64.743 MPH

So you want to downshift into 2nd at 64.7 MPH ...

MPH = 7250*24/(3*4*336)
MPH = 43.155 MPH

And you want to downshift into 1st at 43.1 MPH

You can easily figure this out with your own car in GT4... the tricky part is figuring out the tire diameter in the game if it isn't given to you ...

You can also figure it out when to downshift simply by practicing ...

 

[Lethalchem]

Re: perfect shifting

I've asked about this before, but never got an answer, so I was hoping someone would have brought it up in this thread already.

When using the manual transmission and changing down a gear, in the game, I frequently make the engine hit the rev limiter. I've only been using manual for a few months, but I haven't figured this out yet.

What am I doing wrong? How do I control this?

You're downshifting too soon. Or, more accurately, you're downshifting into a certain gear at too high a speed. Let's say 2nd gear will take you to 75mph before you hit redline. If you are doing 90mph and try to go from 3rd to 2nd then you'll overrev it and bounce of the limiter. You have to slow down more before shifting down. 👍

 

[MasterGT]

You're downshifting too soon. Or, more accurately, you're downshifting into a certain gear at too high a speed. Let's say 2nd gear will take you to 75mph before you hit redline. If you are doing 90mph and try to go from 3rd to 2nd then you'll overrev it and bounce of the limiter. You have to slow down more before shifting down. 👍

Ah, I get it. I think this is what I'm doing.
I sometimes shift down as soon as I've hit the brakes.

Thanks for the other details, too, guys.

OK, back to practicing.

Cheers,

 

[kikie]

To expand a little...

The whole object of racing is to maximize the amount of torque to the wheels for the maximum amount of time. This is done with gears. Gears are torque multipliers. They give a motor a mechanical advantage. Imagine gears working like this: You are trying to turn a ratchet. Your hand is all the way by the socket. Even by using your maximum force, the bolt won't turn. Now move your hand to the end of the handle. By using less than your maximum force the bolt will turn.

Torque is the amount of twisting force the motor can apply to the crankshaft and horsepower is the amount of work the motor can perform over time (rpm).

The torque at wheels of the car or truck is what gets the vehicle moving. The torque at the engine crankshaft is multiplied (increased) to the wheels by an amount equal to the gear ratio in the transmission. Thus, the torque at the wheels of the car is much higher than the torque generated at the engine crankshaft. For example, take a gear ratio that is 8.55:1 in first gear, the torque being delivered to the wheels is equal to this number multiplied
by the engine torque at whatever RPM you're at. It's actually a little lower than that because energy is lost through the transmission, commonly refered to as mechanical or parasitic loss, however, you get the point.

Suppose the engine RPM is 5600 RPM, then the maximum speed the car can go in first gear is equal to 5600 divided by 8.55 (the gear ratio), which equals 655 RPM, or 50 mph. This 655 RPM is how fast the wheels are rotating, and based on the size of the tire, this translates into a forward speed of 50 mph for the car. And from 0-50 mph, the torque being generated at the wheels of the car is equal to gear ratio (8.55) multiplied by the engine torque. As you go up in gear, the gear ratio decreases so that the torque delivered to the wheels is less.

Now again, for racing or acceleration, you want to maximize the amount of torque at the wheels for the longest period of time. Without going into a lengthy explanation, you achieve this by using an engine that makes alot of torque at high RPM, i.e, horsepower according to the famous equation relating torque to horsepower. mentioned above. Since these values cross at 5252 rpms, torque will be higher than horsepower below that number and horsepower will be higher than torque above that number. Ever wonder why old muscle cars have higher torque ratings vs horsepower ratings? Bingo- low redlines. But of course peak numbers don't tell the whole story.

Having an engine that makes alot of torque at high RPM (i.e, hp) means that you can do either:
(1) Have high gear ratios in your transmission, which means the torque delivered to the wheels is high because the transmission is increasing the engine torque by a large factor (for example., 15:1 in 1st gear in a honda S2000), or
(2) Stay in the lower gears at higher speeds since your redline is very high. Since the gear ratios are higher in the lower gears, the torque at the wheels will be higher as well, and thus, you accelerate quicker.

Trucks are not designed to go fast at high speeds, nor are they designed to accelerate quickly. They must, however, move a large amount of mass from a standstill, and thus have engines that make alot of engine torque at low RPM's. However, because of the fact that they make low horsepower and have a low redline, the torque generated at the wheels of the truck decreases rapidly as their speed increases. That's okay though, it's a truck. It's not meant to "let's go from a roll".

At the other extreme, F1 and Indy Cart racing cars have very high horsepower (~800 hp) and low engine torque (~250 ft-lbs). However, because these engines
generate their engine torque at high RPM's (~14,000 RPM), they can use high gear ratios so that the torque generated at the wheels is VERY high.
Conversely, they can use low gear ratios, which means they can stay in the lower gears at much higher speeds. Either way, the torque being delivered
the the wheels of the car from 0-150 mph is much higher than if they had an engine that made 250 hp and 800 ft-lbs.

Ok, I'm done blabbing.


BTW - Good post jmac

No, don't stop "blabbing".

I Like your "blabbing". It is very interesting!!!! 👍 👍

and jmac's posts too!!!!

 

[lnasphinx]

i have one question:

in aspec mode, do you get more points if you drive with Manual Transmission?
(because i saw that kind of a option in Enthusia)

 

[Swift]

Example Car Specs ...

Rev-Limit - 7500 RPM
Final Drive Ratio - 4
Tire Diameter - 24"
Gear Ratios ... 1st - 3 ... 2nd - 2 ... 3rd - 1

So you're travelling at 125 MPH in 3rd gear and you need to brake down to 30 MPH, so you want to be in 1st gear for the corner ...

You don't want to hit the rev-limiter as it will cause your tires to lock up temporarily, reducing brake power and control ...

So you want to shift so that you hit 2nd just below the rev-limt of 7500 RPM and same when you downshift from 2nd to 1st ...

MPH = RPM * Tire Diameter (outer, in) / (Gear Ratio * Final Drive Ratio * 336)
MPH = 7250*24/(2*4*336)
MPH = 64.743 MPH

So you want to downshift into 2nd at 64.7 MPH ...

MPH = 7250*24/(3*4*336)
MPH = 43.155 MPH

And you want to downshift into 1st at 43.1 MPH

You can easily figure this out with your own car in GT4... the tricky part is figuring out the tire diameter in the game if it isn't given to you ...

You can also figure it out when to downshift simply by practicing ...

I like the breakdown very much. But I think your last line was the best! heh heh.

 

[F310B]

For sure manual has been faster for me. I got all gold licenses in GT3, and then decided to do them with manual. I had never driven manual before but within 40 minutes I was beating my old gold laptimes. The test I was trying it on was the S-6 test in the Viper at Laguna Seca. Within half an hour or so I was consistently getting 20.1s for the first sector as opposed to 20.5 being my best *ever* using automatic.

 

[Z32]

I feel you brotha. The automatic seems so slushy. It seems like it shifts slower, revs lower, and accelarates out of corners slower. Manuel you dont have to think of when to shift. A good driver just knows when to shift. Its just a reaction my fingers do. I love to engine break(in real life it helps your brakes last longer!) I usaully take a car out on a track, beat the living **** out of it, and then i understand the physics of the car.

engine braking heavily wears down your engine. much easier to replace brake pads then to rebuild your engine 👍

So no, an automatic is not better. There is no automatic transmission in GT. The "shifting help" that is an option simply makes driving in GT easier if you can't manage the gears yourself, and is, in fact, for girls.

LMAO!!!!!

 

[Gabkicks]

the sad part is there are no girls here to take offense to that statement