Manual Trans Questions

[drivehard]

How can I figure out the RPM I should be shifting at for different cars? In settings they have a simple line graph that must be useful in someway. Do I want to shift where HP and Torque intersect? I know the answer isn't that simple. Any help would be appreciated.

While cornering, sometimes you're required to break below the third gear threshold, but stay in third and accelerate out from there. If I were to drop down to second I would feel a massive acceleration increase. Dropping down to second seems faster but dosen't seem to be wiser. Which is better under normal or predictable conditions? Thanks in advance.

 

[Kishkuman]

Actually the answer may be incredibly simple. If dropping down gives greater acceleration then do that. Imagine coming-out of that same corner against your buddy that just stayed in 3rd you would end up in front. Keep your foot down until you hit the red line and not a moment before. Simple as that!

 

[Praetorr]

My very basic understanding is that you (usually) want to shift up at max HP. Which may or may not be the redline.

In the tuning section of each car there's a little tab where you can see the specific RPM where this occurs.

 

[Kishkuman]

Well that is true and I think it's also it's to do with enough torque being available in the rev range of the gear your going into otherwise you risk getting bogged down. I'm no specialist ether but in all the motor sports Iv watched Iv never seen them change gear in "normal and predictable" conditions at any other point other than the red line

 

[drivehard]

Actually the answer may be incredibly simple. If dropping down gives greater acceleration then do that. Imagine coming-out of that same corner against your buddy that just stayed in 3rd you would end up in front. Keep your foot down until you hit the red line and not a moment before. Simple as that!

Ya thats basically what I do. When I'm a bit hot, as bspec would put it, I manhandle the machine. But I've noticed in all the license test examples, special events examples, etc. They always tough it out through the higher gear. As if there shunning acceleration for more speed???

 

[Kishkuman]

Ya thats basically what I do. When I'm a bit hot, as bspec would put it, I manhandle the machine. But I've noticed in all the license test examples, special events examples, etc. They always tough it out through the higher gear. As if there shunning acceleration for more speed???

I think I almost fully understand you but not quite. Its late and I might be not reading properly but I don't think it's possible to shun acceleration for speed. Unless your talking about gear ratios. I thought we were just talking about when's the best time Change gear.

 

[drivehard]

I think I almost fully understand you but not quite. Its late and I might be not reading properly but I don't think it's possible to shun acceleration for speed. Unless your talking about gear ratios. I thought we were just talking about when's the best time Change gear.

Hence the three question marks.

Say you're entering a corner in third gear. You need to brake so much that you really belong in second gear. However, all the examples in GT5 would have you stay in third. As if you were saving more time by not shifting??? Or something. I don't understand the reasoning is why I'm asking.

 

[Kishkuman]

Oh ok Im with you now. I can't say Iv noticed GT5 behaving like that but you are right it doesn't seem to make sense. Iv always assumed you change gear if it's going to make you even a little bit faster. There will be instances where it's probably not worth changing like if you are in a series of corners where you would loose speed by changing. How ever my skills on this game are not even close to where I would notice a minute difference in a situation like that. Did any of that make sense? I should probably go to bed

 

[Zenmervolt]

My very basic understanding is that you (usually) want to shift up at max HP. Which may or may not be the redline.

Nope, that's most definitely not what you want to do.

I posted this the other day, but will repeat here as well:

What you want to do is shift at either:

1) The point just before the rev limiter kicks in,

or

2) The point at which the overall gear ratio for the next higher gear supplies more torque to the drive wheels than the current gear ratio.

In most cars, the gears and the engine's torque curve are spaced such that (1) is the best option, but if a car has an absolutely massive (and I do mean massive) falloff in torque in the upper part of the rev range, it can sometimes be best to slightly short shift.

Remember, a car is propelled forward by the torque at the drive wheels. This varies not just with engine RPM, but with the gear selected as well. If you have a 1:1 gear ratio, the engine torque and wheel torque are the same, if you have a 2:1 gear ratio, the torque at the wheels is double the torque at the engine. What you want to do is always maximize the torque at the wheels, which means you don't want to shift immediately at the engine's peak since you lose the torque multiplication from the lower gear. In general, you're better off holding the lower gear and keeping the torque multiplication than grabbing the higher gear and putting the engine at a lower RPM where it makes more torque.

For example, using purely invented numbers just to illustrate the math, let's say that an engine hits peak torque of 75 ft-lbs at 5,000 RPM, makes only 65 ft-lbs at 6,000 RPM and falls off further to 55 ft-lbs at the 7,000 RPM redline. Let's say that 1st gear has a 3.5:1 ratio and 2nd has a 2:1 ratio. At redline, the engine is only making 55 ft-lbs of torque, but because of the gear ratio, the wheels are actually getting 55*3.5 or 192.5 ft-lbs of torque. Even at the engine's peak output of 75 ft-lbs, shifting to 2nd only gives the wheels 75*2 or 150 ft-lbs of torque.

Even though you're past the engine's power peak, the wheels still get the most torque by waiting until redline to shift because of the way gearing works.

For a more detailed treatment, I highly recommend this link: http://vettenet.org/torquehp.html

 

[blaktek]

The obvious answer would be "stay in the powerband". But things are never that simple.

Shifting takes time, and in some cases, a lot of it. You also have to be able to control your car, so being in the powerband with a big engine on a tight curve will demand concentration and throttle control.

The situation will also influence the shift timing. If you are chased, you could exit the turn in 2nd gear with a sidestep and a little smoke to unsettle your adversary. Control your acceleration to be "efficient". Or stay in 3rd, so you will be able to floor it with no traction loss, sparing the 2nd to 3rd shifting time to take that bit of advantage.

The most efficient shifting depends a lot on your driving style as well as your car, the type of corner, your race situation.

Shifting on a straight is primarily dependent on the car, and how it reacts. With an engine set at 8,000 RPM redline and 8,500 RPM ruptor, your shifts could be more efficient with 2nd and 3rd at 8,500 RPM, 4th and 5th at 8,000, and 6th at 7,500.

In the end, it's basically up to you to find the right timing.

 

[onearmbandit]

Hp = (torque x rpm) / 5252. Ie at 5252rpm torque = hp. So the point they intersect at is simply that, (if the scale is correct) 5252rpm.

As far as when to shift, a number of things dictate this point. You can 'short-shift', ie change gear up lower in the rev range. You might do this exiting a tight corner that eases out to a gradual turn. In a straight line, you want to be changing at peak hp, no sense in 'over-running' it. However, there is some times when over running it can be of benefit, ie approaching a tight bend in 3rd, still not at the corner but now past peak hp, there is no sense in upshifting to 4th if you are immediately going to go back down to 2nd. This will help the car maintain it's balance better.

Of course this is all assuming that your gear ratios are correct, so that when you change up you're best utilising the torque available for that gear change.