FRS stock top speed

[humfrz]

Originally Posted by paulca

Okay, fair point on "indicated" speed. But the stock speedo overreads by around 10%. So his 149 indicated is probably more like 136 actual.

If you don't believe this, look up the mechanical limit of 2nd gear, I believe it is 59.8mph or something similar. Now go and bounce the car off the limiter in 2nd and see what speed it reads, I've seen mine read 65mph. Then check on a GPS.

Wheels/Tyres make a difference, even tyre pressures make a difference. The speedo only counts how many times the wheels go round, via a gearbox sensor and multiply it by the circumference of the tyre. If you put smaller wheels, even by a few mm smaller the speedo will read high. Even worn tyres can add a few percent to your indicated speed. If you changed your wheels and tyres and did not match the sizes exactly to achieve the same total circumference of stock your speedo is now inaccurate. In the UK insurance companies get awful annoyed about this and refuse to pay in some circumstances.

As I worked out on another thread. The difference in horse power between 139 and 160mph is 64bhp! The car needs 264bhp to do 160mph. That is assuming the 139 is it's genuine max actual speed.

You see adding 10mph here or there is not a small thing at top speed. Every mph needs more and more power. The simple rule is, to double the speed you need 4 times the horsepower. Anyone with a basic college education can rearrange that to work out the horse power difference needed to change their vmax by a given amount.

A down hill will not make as much difference as a tailwind would. Air resistance is such a big factor that mechanical drag is all but negligible at top speed.

With that said, in theory with a constant 20 mph tailwind I suppose 150 might be achievable. However finding such a steady wind that would allow the car long enough to accelerate to 150 is going to be very hard to find.

OK.

I challenge you (or anyone else) to do the math with the formula shown in post # 272.

If you accept, please indicate what factors you used for the variables in the formula.




humfrz

[humfrz]

Originally Posted by Ultramaroon

I agree with your conclusion regarding your own speedo but disagree with the generalization. By all verifiable techniques, mine is dead on.

I've pulled 112 on the front straight at PIR. That's plenty fast enough for me.

Old men shouldn't be driving over 100 mph ....... why? ....... because of "brain shake" .......



humfrz

[paulca]

Originally Posted by humfrz

OK.

I challenge you (or anyone else) to do the math with the formula shown in post # 272.

If you accept, please indicate what factors you used for the variables in the formula.
humfrz

Do we even have the information we need? Exact frontal area, exact average co-efficient of drag?

My point was to get across that small increases in speed require lots of power increase. So claims of cars going 23 mph faster than the stated manufacturer number (137mph I believe, from memory) are highly unlikely.

Also that speedo readings are also highly unreliable.

GPS for that matter isn't much better. It greatly depends on the GPS used, it's accuracy and refresh rate and any equations used to smooth the usually jumpy data. Also depends on how straight and level the road is.

A proper calibrated laser or radar reading or a track day timing beam speed trap I might put more value in.

[humfrz]

Originally Posted by paulca

Do we even have the information we need? Exact frontal area, exact average co-efficient of drag?

My point was to get across that small increases in speed require lots of power increase. So claims of cars going 23 mph faster than the stated manufacturer number (137mph I believe, from memory) are highly unlikely.

Also that speedo readings are also highly unreliable.

GPS for that matter isn't much better. It greatly depends on the GPS used, it's accuracy and refresh rate and any equations used to smooth the usually jumpy data. Also depends on how straight and level the road is.

A proper calibrated laser or radar reading or a track day timing beam speed trap I might put more value in.

Well, DANG, there, paulca, I reckon one would have to make some estimates to plug into the formula.

The published COD for a 2013 FR-S is 0.27.

The frontal area could be estimated (just take a look see at it from the front. OR, someone who has a CAD program could calculate it.

So, are you gonna do the math or not ...... ??

I would, but it's my nap time .....


humfrz

[PNW-BRZ]

When people post their speeds, it would be good to know if they are stage 1/2/3 and if Manual or Auto or have changed their Final Drive Ratio. Also many tunes remove the speed limiter. As to this thread giving the cars a bad rep, it's too late. These are one of the most ticketed vehicles. People just need to try to speed "Safely". Also be aware that negligent driving is a felony in Canada, so if you get busted in the US for Negligent you are not eligible to travel to our Neighbor in the North.

[Somerandom18]

So everyday driver europe did a run and hit 149 mph in a 2017 Toyota 86. That's with a 4.3 FD.

Sent from my Pixel XL using Tapatalk

[paulca]

Originally Posted by humfrz

Well, DANG, there, paulca, I reckon one would have to make some estimates to plug into the formula.

The published COD for a 2013 FR-S is 0.27.

The frontal area could be estimated (just take a look see at it from the front. OR, someone who has a CAD program could calculate it.

So, are you gonna do the math or not ...... ??

I would, but it's my nap time .....

For what it's worth, I plugged in some numbers. The equation is not that scary. However it's a bit basic and does include anything for rolling resistance etc. which while small would shave a few percent off.

power=147000 (fly wheel watts)
aird=1.3
area=2.28 (sq m)
cod=0.27
x = (2*power) / (aird * cod * area )
v = e(l(x)/3) (this is a cube root)
v * 2.23694 (m/s to mph)
160.20993999770118933534

The frontal area is a guess from the total width and total height on the spec.

147,000 watts = 197 bhp.

When we modify that to "wheel hp" from a bit of googling we get:

power=117000 (157 wheel hp)
x = (2*power) / (aird * cod * area )
v = e(l(x)/3)
v * 2.23694
148.47236739928096565100

[humfrz]

Originally Posted by paulca

For what it's worth, I plugged in some numbers. The equation is not that scary. However it's a bit basic and does include anything for rolling resistance etc. which while small would shave a few percent off.

power=147000 (fly wheel watts)
aird=1.3
area=2.28 (sq m)
cod=0.27
x = (2*power) / (aird * cod * area )
v = e(l(x)/3) (this is a cube root)
v * 2.23694 (m/s to mph)
160.20993999770118933534

The frontal area is a guess from the total width and total height on the spec.

147,000 watts = 197 bhp.

When we modify that to "wheel hp" from a bit of googling we get:

power=117000 (157 wheel hp)
x = (2*power) / (aird * cod * area )
v = e(l(x)/3)
v * 2.23694
148.47236739928096565100

Hi ya, paulca

Your figuring appears to be accurate ........

However, the values I used are a bit different.

I used:

160 WHP (averaging several values reported on the internet)

density = 1.3

Cd = .27

frontal area = 21.2 sq. ft. (figure published by Car & Driver)

Plugging those numbers into the formula, my abacus gives me a calculated top speed of a stock 2013 FR-S, of roughly ......

157 MPH.

(I think your estimated frontal area of 2.28 m squared is a bit high)

Your thoughts ......??


humfrz

[Borchert97]

So I did another speed test last night on I-405, I got it to 134 again, kept going, but it wouldn't climb anymore, I suppose the MY17 is electronically limited to 134, I was getting rev bounce like you'd see while bouncing off the rev limiter, but this was only at like 5.5kish in 6th, and the needle was bouncing slightly and not letting me go faster, so my speed limiter is 134.

[humfrz]

Originally Posted by Borchert97

So I did another speed test last night on I-405, I got it to 134 again, kept going, but it wouldn't climb anymore, I suppose the MY17 is electronically limited to 134, I was getting rev bounce like you'd see while bouncing off the rev limiter, but this was only at like 5.5kish in 6th, and the needle was bouncing slightly and not letting me go faster, so my speed limiter is 134.

hmmm......are the MY17s electronically speed limited....??

I wouldn't think so, but I don't know .....


humfrz

[MurderousPandas]

Originally Posted by PNW-BRZ

When people post their speeds, it would be good to know if they are stage 1/2/3 and if Manual or Auto or have changed their Final Drive Ratio. Also many tunes remove the speed limiter. As to this thread giving the cars a bad rep, it's too late. These are one of the most ticketed vehicles. People just need to try to speed "Safely". Also be aware that negligent driving is a felony in Canada, so if you get busted in the US for Negligent you are not eligible to travel to our Neighbor in the North.

Define stage 1, 2, and 3

Sent from my HTC6535LVW using Tapatalk

[Borchert97]

Originally Posted by humfrz

hmmm......are the MY17s electronically speed limited....??

I wouldn't think so, but I don't know .....


humfrz

It certainly felt like it, it's also hot as ass in our state right now, so maybe the conditions weren't as good as they could be. But it certainly felt like the revs were bouncing as if it were limited.

[humfrz]

Originally Posted by Borchert97

It certainly felt like it, it's also hot as ass in our state right now, so maybe the conditions weren't as good as they could be. But it certainly felt like the revs were bouncing as if it were limited.

Maybe your car is not used to these temperatures and was having a ...... heat stroke .......




humfrz

[Overdrive]

Could be Europe and the rest of the world don't have any limitations in place (Autobahn needs make a good case, after all), but looks like it's just shy of 150 if you have enough time and road to get there. Tom certainly loves what it can do at any speed.


[ame="https://www.youtube.com/watch?v=dPtX42Ttkqo&t=1s"]2017 Toyota GT86 (86, BRZ) Review - Autobahn and Hatch Comparisons - Everyday Driver Europe - YouTube[/ame]