Gear Ratios

[shirakawaa]

I am hoping that there is at least some correlation between the computed results and the actual results.[...]

As I said previously, as a general guide your spreadsheet is ok, perhaps good enough in most cases. For "fine tuning", however, it lacks some data that affect car acceleration over time, and that GT5 is using as far as I can see.

Can data logger help in gathering data?

Unfortunately the data logger in GT5 is pretty much useless for any advanced task. It doesn't use a meaningful/useful scale for any axis, and data can't be exported for further processing.

 

[AlphaGnomeo]

And if we could ever figure out how GT5 computes their gear ratios along with the max/min for each gear, we might be able to / have to use a spreadsheet to compute the odd settings you need to get the exact gears that you want.

 

[No_OBsT33R]

I hate to say it is "all" we will need, but - at least in theory - it should be a large part.

I've tested out the rpm calculator. I've got it set up to tell me the rpm I'll be in after I shift, it's spot on... This is good, a good first sign.

 

[turbo.928]

Hi Thank you very much for sharing the excel but I can't unzip it.

 

[Basilea]

I think another problem is when the power-/ torqueline don't cross themselves at 5250rpm.
This happens especially with the low and mid rpm turbo.

Something that keeps me wondering about this is, that it only crosses at 5250rpm with HP/ftlb but if you use kW/Nm it is somewhere around 9300rpm?

The formulas are hp = torque * RPM / 5252 and kW = Nm * rpm / 9554 so this doesn't make sense to me, because it can only cross at one point, or what am I missing here?

 

[Rotary Junkie]

^Seems kW/Nm should cross at 9554rpm then.

 

[niky]

And if we could ever figure out how GT5 computes their gear ratios along with the max/min for each gear, we might be able to / have to use a spreadsheet to compute the odd settings you need to get the exact gears that you want.

The gear ratios are pretty standard. My calculator is adapted from one I use for real world cars and the numbers work out.

What you want is a supplemental calculator to derive wheel size from maximum speed in gear and gear ratios. (I have one, too... have to dig up the calculations later and format it so it's not an unreadable string of gibberish)

Unless you are talking about the auto-settings... though those are relatively straight-forward. Whatever auto-setting you put for the top speed, GT5 creates a gear set where the top gear ends at that speed and all the gears are evenly spaced below it.

 

[dr_slump]

^Seems kW/Nm should cross at 9554rpm then.

EDIT: ahhhh wait... Yes it's correct!

 

[AlphaGnomeo]

I had planned to overlay a line called "HP required" on the HP charts, expecting that it might help with gear ratios since excess HP is what causes the car to accelerate faster and because lack of which eventually causes the car to stop accelerating.
However, I am having trouble making the "HP required" and "HP at axle" lines instersect. Using the Corvette, I am assuming that the Coefficient of Drag is .3 and that the frontal area is 20 sq.ft. At 237 mph, my equations show that you need 562.4 HP.
However, at 7,900 rpm, the engine is producing 709 HP and with a top gear of .808, a final gear of 3.420, and drivetrain loss of 15%, that equals 1,664 HP at the axle.
Even if I run it up to 300 mph, I get required HP of 1,155 and axle HP of 1,309 (with a top gear of .636). And I know that a Corvette will never hit 300 mph - in the game or elsewhere.
I can add rolling resistance, but that is not big enough to make much of a difference.
The formula that I am using for drag is:
HP = ((Cd*A)*(.5*P/32.1)*(V*22/15)^3)/550
where:
Cd = .3
A = 20
P = .08
V = 237

 

[AlphaGnomeo]

Unless you are talking about the auto-settings... though those are relatively straight-forward. Whatever auto-setting you put for the top speed, GT5 creates a gear set where the top gear ends at that speed and all the gears are evenly spaced below it.

Yes, these are the ones I can't figure out. They do look nice and evenly spaced with the min RPM increasing with each gear. But I can't figure out what formula they are using to come up with those evenly spaced gears.

 

[No_OBsT33R]

What do you guys think of this

Direct data. I ran the car through each gear and noted the speed at the rpm then calculated the resistance with the rolling radius.

The values after hitting the rev limiter I carried over to flatten the line at peak.

The test mule is a Scoobie 22B Dynoed here

Gear torque

 

[shirakawaa]

Try of using speed instead of RPM, and the chart will make much more sense.
The speeds at which the curves cross will be the optimal shifting points.

 

[No_OBsT33R]

Try of using speed instead of RPM, and the chart will make much more sense.
The speeds at which the curves cross will be the optimal shifting points.

Not sure what you mean, I used speed & rpm with each gear

Do you mean hit a speed and note the RPM?

What I see is the rate of acceleration is relatively constant, as is the resistance.

This is past peek tq, hp, redline, all the way to the limiter.

 

[No_OBsT33R]

To do the test with speed I need a car with a digital tach, so I can note accurate RPM @ a given speed.

You guys know one to use?

I took the graph added a shift rpm calculator and

BOOM!!! A lil work and I manually got the optimum shift points.

Refined shift points show something interesting.

Final refinement

Optimum shift points become

1 / 2 @ 7000rpm
2 / 3 @ 7750rpm
3 / 4 @ 8500rpm
4 / 5 @ 8000rpm
5 / 6 @ 7500rpm

What do you this? Where to go from here?

 

[AlphaGnomeo]

Not sure what you mean, I used speed & rpm with each gear

I think he means to put speed on the horizontal axis and RPM/torque on the vertical axis, so that you get a visual indicator of the shift points.

In my analysis, I assume that everyone will shift at the same preprogrammed RPM for all gears. As you have shown, this may not always be the best optimal shift point. However, I am not sure whether you are supposed to shift when the torque lines cross or when the HP lines cross. I have seen arguments for both (which is why I plotted both on my spreadsheet).

Looks like you are getting the hang of working with Excel.

 

[No_OBsT33R]

I think he means to put speed on the horizontal axis and RPM/torque on the vertical axis, so that you get a visual indicator of the shift points.

In my analysis, I assume that everyone will shift at the same preprogrammed RPM for all gears. As you have shown, this may not always be the best optimal shift point. However, I am not sure whether you are supposed to shift when the torque lines cross or when the HP lines cross. I have seen arguments for both (which is why I plotted both on my spreadsheet).

Looks like you are getting the hang of working with Excel.

Thanks, been told Im a fast learner

I want to do that, but accurate rpm's at a given speed seem hard to get without a digital numerical tachometer. I can guesstimate but that would cause inaccuracies that would mess up the accuracy of the results.

I can see in the chart where speed in current gear meets speed in the next gear, but I'm eye-balling the shift point then comparing the speed at the rpm's I'll be at in the next gear after shift.


I've tested the shift points on the track, and it feels great, steady acceleration, however the difference from just shifting at red line is very minimal, could even be negligible.

Grab a 22b, fully tune it, use the gears in the graph then try the shift points. What do you think?

Is there a way to get data from one chart to cross reference data from another?

 

[Adrenaline]

Is there a way to get data from one chart to cross reference data from another?

The '+' sign allows you to transfer data between pages of spreadsheets.

 

[No_OBsT33R]

The '+' sign allows you to transfer data between pages of spreadsheets.

Okay, what I want to be able to do is use the shift calculations with the chart.

As you can see I have shift points and rpm's for the following gear. I want to be able to change the shift point (this will at the same time change the rpm's for the next gear with my formula) and have it display the corresponding speeds for the 2 rpm's in the 2 gears hopefully displaying a line between the 2 and the speed.

Any thoughts?

 

[No_OBsT33R]

I posted up the set up for the 22b (in my Garage) in case anybody wants to confirm my Data.

 

[niky]

In any in-gear calculation, ignore HP. HP on a dynochart is calculated based on torque, rpm and an assumed 1:1 drive ratio... Recalculating it back based on that gearing gives you a number that doesn't mean anything. Torque at the wheels more accurately represents how much acceleration in "G's" you will get in a particular gear.

Still, that old saying "HP sells cars, torque wins races" is not entirely correct... It's more like "Peak HP / torque sells cars, average HP wins races..."

 

[No_OBsT33R]

In any in-gear calculation, ignore HP. HP on a dynochart is calculated based on torque, rpm and an assumed 1:1 drive ratio... Recalculating it back based on that gearing gives you a number that doesn't mean anything. Torque at the wheels more accurately represents how much acceleration in "G's" you will get in a particular gear.

Still, that old saying "HP sells cars, torque wins races" is not entirely correct... It's more like "Peak HP / torque sells cars, average HP wins races..."

I'm using rpm, gear, & speed real time data. I'm able to graph the chart but I haven't figured out out to automatically plot the shift points, I have to manually eyeball it. However it follows an interesting pattern, I'm going to test a few other cars to see if there are any consistencies, it just takes a while to collect the real time data manually.

 

[No_OBsT33R]

Finished calculations for the Scooby 22B & current state of the Optimum Shift Point Calculator.

 

[AlphaGnomeo]

Still, that old saying "HP sells cars, torque wins races" is not entirely correct... It's more like "Peak HP / torque sells cars, average HP wins races..."

So is that where it helps to compute the "area under the curve" since that shows the total torque (or HP) for specific gear settings?

One reason I need a HP chart is to have a place to plot "required HP", unless you can think of a way to computed "required torque".

I am still having trouble coming up with enough drag and friction so that the required HP and available HP lines intersect at a reasonable location. From reading comments about GT4, it sounds like they did too - and that this was one reason they had to limit the gears, so that people would not adjust the gears and travel at unrealistic speeds.

I wonder if the missing component isn't some kind of induced drag. From my experience with modeling aircraft performance, this is a big component in aircraft performance. This could also affect the performance of a car, because at higher speeds, the car needs some of the features of an upside-down wing, either through body shape or attachments, to keep the car on the ground.

 

[AlphaGnomeo]

No_OBsT33R, nicely done.

 

[No_OBsT33R]

Thanks, I appreciate it, still figuring out Excel, awesome program, it does so much work for you.

It Works well, however it's taking a bit of getting used to checking my rpm for the right shift rpm, I'm so used to going off engine sound, hitting the optimum shift points takes precision and it's different each gear, you need the rhythm.

I'm going to run some
more cars and see if any patterns form.

Cheers!

 

[niky]

So is that where it helps to compute the "area under the curve" since that shows the total torque (or HP) for specific gear settings?

One reason I need a HP chart is to have a place to plot "required HP", unless you can think of a way to computed "required torque".

I am still having trouble coming up with enough drag and friction so that the required HP and available HP lines intersect at a reasonable location. From reading comments about GT4, it sounds like they did too - and that this was one reason they had to limit the gears, so that people would not adjust the gears and travel at unrealistic speeds.

I wonder if the missing component isn't some kind of induced drag. From my experience with modeling aircraft performance, this is a big component in aircraft performance. This could also affect the performance of a car, because at higher speeds, the car needs some of the features of an upside-down wing, either through body shape or attachments, to keep the car on the ground.

I just have the program back-calculate HP from torque. So all I do is input torque figures, and try to match peak HP by fudging the torque figure at the peak HP rpm. Works so far.

If you're creative with the top speed slider, you can get any car geared to go well over 500 km/h. Can't recall the highest I've seen, but it's around 1,2000 km/h. No car in GT5 has nearly enough power to pull to those speeds, though.... and there's no track remotely near long enough.

 

[phil_75]

I did a test on Fuji with slider set at 180mph and then at varying increments all the way to the right and got virtually exact same lap times,(within a couple of tenths) car was yellowhat gt-r 518bhp?????

 

[niky]

You need to do A-B-A style tests to validate your results. Finding the right gear setting should be good for at least half-a-second a lap, unless the "stock" setting is already optimal.

 

[AlphaGnomeo]

I did a test on Fuji with slider set at 180mph and then at varying increments all the way to the right and got virtually exact same lap times,(within a couple of tenths) car was yellowhat gt-r 518bhp?????

There should be a point at which HP available should equal HP required to overcome drag and rolling friction. And increasing the slider to show more speed should be counterproductive it should actually reduce the HP available at the wheels. To get maximum speed, you would need to adjust the slider to somewhere a bit above the maximum speed. That would require trial and error.

But on a racecourse, I think the answer is a lot simpler. First, figure out your maximum speed on the track and set the speed to a bit above that. Second, figure out the speeds around the corners. Third, adjust the intermediate gears to develop somewhere around the maximum torque at those speeds.

 

[TT3AZ]

There should be a point at which HP available should equal HP required to overcome drag and rolling friction. And increasing the slider to show more speed should be counterproductive it should actually reduce the HP available at the wheels. To get maximum speed, you would need to adjust the slider to somewhere a bit above the maximum speed. That would require trial and error.

But on a racecourse, I think the answer is a lot simpler. First, figure out your maximum speed on the track and set the speed to a bit above that. Second, figure out the speeds around the corners. Third, adjust the intermediate gears to develop somewhere around the maximum torque at those speeds.

This is true for circuit racing, but for drag racing, you achieve much higher top speed with longer last gear, even though your output tq is lower to the wheels. I have experienced that if you are past the peak hp rpm you wont hit as high speed in a certain distance. For example if we race ssr7, at the end of the tunnel I aim so my rpm will be like 200-500 rpm past peak hp, and i will also exit with greater top speed.