Will the Digital speedometer have a fast refresh?

[Sport-Tech]

^ On the gear ratios - this is not what I wanted to see. If I want super-tall gearing that limits my shifting fun I'll buy a used Cayman...

[Blighty]

Originally Posted by Sport-Tech

^ On the gear ratios - this is not what I wanted to see. If I want super-tall gearing that limits my shifting fun I'll buy a used Cayman...

I wouldnt call it super tall.

Its about 40mph, probably hits between 60~62mph in 2nd at redline.

[Sport-Tech]

Originally Posted by Blighty

I wouldnt call it super tall.

Its about 40mph, probably hits between 60~62mph in 2nd at redline.

According to R&T, at release the FR-S hit 35 mph in first at 7400 rpm - and of course that's before the final drive was shortened. So there appears to be a substantial maximum speed gap in first that will only get wider in the higher gears.

[ermax]

Originally Posted by Blighty

If my stupid brain is working. I'm sure there is a google tool for this

Yep, there is a really good one here:
https://www.blocklayer.com/rpm-gear.aspx

Or this link which supplies all the details for a 2013 Twin with 6MT:
https://apx6u.app.goo.gl/XgGN

[timurrrr]

Originally Posted by Sport-Tech

According to R&T, at release the FR-S hit 35 mph in first at 7400 rpm - and of course that's before the final drive was shortened. So there appears to be a substantial maximum speed gap in first that will only get wider in the higher gears.

I don't have a recent data log of bouncing off the rev limiter in 1st in my '17 BRZ, but I do have a data log where 27.5 mph is recorded at 6000 rpm.
This means a '17 BRZ (i.e. with a shorter final drive) should do 34 mph in 1st.
I vaguely remember seeing 37 mph in 1st at one point, but don't remember if it was in my car or a pre-'17 rental; neither do I remember what rev limiter was set to.

Having rewatched that clip at 0:15 frame by frame (use ,/. keys in YouTube), I'm now even more suspicious of what's going on.
As the digital tachometer crosses 5k rpm, the digital speedometer changes from 61 to 62 km/h.
As the digital tachometer crosses 7k rpm, the digital speedometer changes from 64 to 65 km/h.
You don't need to be a math professor to know that if a car does 61–62 km/h at 5k, it should do ~86 km/h at 7k rpm in the same gear.
Similarly, if it does 64–65 km/h at 7k, it should be doing 46 km/h at 5k rpm.

Assuming both rpm and wheel speed sensors are responsive enough, this can only be explained by either:
- they were revving the engine in neutral (or with clutch pressed) while slowly accelerating downhill (not likely?),
- or there's too much artificial smoothing or latency going on (which makes me sad).

What's even more suspicious is that in the last couple of frames of that shot you can see the digital tachometer showing increasing rpms,
while the vertical line in the dyno plot on the left is already showing decreasing rpms.

[Transport3r]

Originally Posted by timurrrr

What's even more suspicious is that in the last couple of frames of that shot you can see the digital tachometer showing increasing rpms,
while the vertical line in the dyno plot on the left is already showing decreasing rpms.

Lol. So the one datapoint in this whole discussion turns out to be effects editing in a marketing video? Nice.

[p1l0t]

Sent from my SM-G975U using Tapatalk

[Blighty]

Originally Posted by timurrrr

I don't have a recent data log of bouncing off the rev limiter in 1st in my '17 BRZ, but I do have a data log where 27.5 mph is recorded at 6000 rpm.
This means a '17 BRZ (i.e. with a shorter final drive) should do 34 mph in 1st.
I vaguely remember seeing 37 mph in 1st at one point, but don't remember if it was in my car or a pre-'17 rental; neither do I remember what rev limiter was set to.

Having rewatched that clip at 0:15 frame by frame (use ,/. keys in YouTube), I'm now even more suspicious of what's going on.
As the digital tachometer crosses 5k rpm, the digital speedometer changes from 61 to 62 km/h.
As the digital tachometer crosses 7k rpm, the digital speedometer changes from 64 to 65 km/h.
You don't need to be a math professor to know that if a car does 61–62 km/h at 5k, it should do ~86 km/h at 7k rpm in the same gear.
Similarly, if it does 64–65 km/h at 7k, it should be doing 46 km/h at 5k rpm.

Assuming both rpm and wheel speed sensors are responsive enough, this can only be explained by either:
- they were revving the engine in neutral (or with clutch pressed) while slowly accelerating downhill (not likely?),
- or there's too much artificial smoothing or latency going on (which makes me sad).

What's even more suspicious is that in the last couple of frames of that shot you can see the digital tachometer showing increasing rpms,
while the vertical line in the dyno plot on the left is already showing decreasing rpms.

Great pickup.

If its faked then its faked. Pretty good fakery though, they even included the dyno animation.

If its real then its possible that this is a second gear wheel spin. Wheel speed isn't the only thing they use to calculate real speed - you wont find your car reporting your speed based on a burnouts tire velocity But all this certainly makes it much harder to garner anything at all (apart from perhaps the shift point up to 2nd was down between 55-60kph - which actually starts to put it back in the ballpark of a 4.1 ratio (57kph at 7400).

[Dzmitry]

Before we get too deep into this conversation, and this may have been mentioned, I just skimmed through everything - but keep in mind there are different final gear ratio's in different regions due to regulations. So this video may not be telling us much of anything related to the actual final drive U.S. specs.

[Blighty]

Originally Posted by Dzmitry

Before we get too deep into this conversation, and this may have been mentioned, I just skimmed through everything - but keep in mind there are different final gear ratio's in different regions due to regulations. So this video may not be telling us much of anything related to the actual final drive U.S. specs.

Yes it would be safe to assume its from the JDM STI showcar, but I doubt there would be a difference.

Are there different final drives in the 86/BRZ across different regions? I thought that, apart from the change with the 16+ cars, they were all the same.

[timurrrr]

Originally Posted by Blighty

If its real then its possible that this is a second gear wheel spin.

Finally someone mentions wheel spin!

Originally Posted by Blighty

Wheel speed isn't the only thing they use to calculate real speed - you wont find your car reporting your speed based on a burnouts tire velocity

Hmm, are you sure?
The speed data on the CAN bus (and OBD-II) certainly reports whatever the speed the rear wheels are rotating at.

When I launch at autox and get wheel spin, or when I go sideways at the skidpad, I certainly see the CAN speed not matching the GPS speed, but still being in sync with the rpms.
I just reviewed a few of my onboards, and whenever I see the digital speedo, it matches the virtual gauges in my overlay created from the CAN data (except for the lag due to terrible refresh rate).

I have to admit I never tried doing a standing burnout in my BRZ to be able to say for sure that they only use the speed sensors on the rear wheels to calculate speed displayed on the digital speedometer.

Originally Posted by Dzmitry

keep in mind there are different final gear ratio's in different regions due to regulations

Possibly! But if I were to make a bet, I'd expect them to use one final drive everywhere for this new gen, at least for the first few model years.

Originally Posted by Blighty

Are there different final drives in the 86/BRZ across different regions? I thought that, apart from the change with the 16+ cars, they were all the same.

I think I heard that they kept the taller FD in Europe for '17+.

[Sasquachulator]

Some places didnt get the +5hp/trq and the red intake plenum with the manual.

Gonna assume the FD didnt change when those didnt change either.

[timurrrr]

Originally Posted by timurrrr

Hmm, are you sure?
The speed data on the CAN bus (and OBD-II) certainly reports whatever the speed the rear wheels are rotating at.

When I launch at autox and get wheel spin, or when I go sideways at the skidpad, I certainly see the CAN speed not matching the GPS speed, but still being in sync with the rpms.

Here's CAN data.
On all the three graphs, green line is GPS speed.


Cyan — CAN speed
Purple — RPM


Cyan — CAN speed
Orange, purple — Rear wheel speeds


Cyan — CAN speed
Orange, purple — Front wheel speeds

[Kronk]

0:59 .