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Discussion Starter · #1 ·
I was thinking about this question recently:
  • What defines the optimal shifting strategy in Q50 red sport and how is this correlated to dyno results?
  • "optimal", as-in get from point A to point B as quick as possible
Why?
  • Looking at dyno logs on this forum/elsewhere, it seems like there might be enough variability in torque curves to not say "always shift at redline" and call it a day
Goal:
  • Use data to dynamically define optimal shift RPM across gears for a given tune
I decided to throw together a quick model that I/we can build from to answer this question. Taking some inspiration from Engineering Explained (Youtube video) I sketched out the model:
  • Variable for Optimization: acceleration (max)
  • Model parameters
    • Torque
    • Gear ratio
    • RPM
  • Model assumptions
    • Considering only straight-line acceleration scenario
    • 100% traction at all times
      • would be interesting to explore frictional force and a function for % traction ~ F(% throttle, RPM, Torque, Gear, tire friction coefficient) but leaving that out of scope for v1
        • maximize forward progress, minimize wheel spin
    • Final drive ratio, other gear reductions, and drivetrain loss are constant
    • Shift timing is constant, near 0
    • Assume wheel parameters are constant (same diameter, mass)
Q50 RS Gear RatioCorrect?
GearRatioGear Shift Ratio % Change (Hi to Lo)
1​
4.78​
54%​
2​
3.1​
57%​
3​
1.98​
45%​
4​
1.37​
37%​
5​
1​
15%​
6​
0.87​
12%​
7​
0.78​

Next steps:
  • Find sample dyno log data for Q50 with continuous Torque distribution and assess if there may be variable optimal shift strategies (please ping me if you have a sample data set)
Would love feedback on the modeling (I know we have some technical/engineering folks). It may be a fruitless endeavor with an obvious answer, but I am curious.

Also, feel free to chime in with how you shift to get the most out of your tune. I did not see much on this topic. I know there are a lot of factors (AWD vs. RWD, track vs. road, etc.) that won't be captured in a simple model, so good to get real-world feedback.
 

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I was thinking about this question recently:
  • What defines the optimal shifting strategy in Q50 red sport and how is this correlated to dyno results?
  • "optimal", as-in get from point A to point B as quick as possible
Why?
  • Looking at dyno logs on this forum/elsewhere, it seems like there might be enough variability in torque curves to not say "always shift at redline" and call it a day
Goal:
  • Use data to dynamically define optimal shift RPM across gears for a given tune
I decided to throw together a quick model that I/we can build from to answer this question. Taking some inspiration from Engineering Explained (Youtube video) I sketched out the model:
  • Variable for Optimization: acceleration (max)
  • Model parameters
    • Torque
    • Gear ratio
    • RPM
  • Model assumptions
    • Considering only straight-line acceleration scenario
    • 100% traction at all times
      • would be interesting to explore frictional force and a function for % traction ~ F(% throttle, RPM, Torque, Gear, tire friction coefficient) but leaving that out of scope for v1
        • maximize forward progress, minimize wheel spin
    • Final drive ratio, other gear reductions, and drivetrain loss are constant
    • Shift timing is constant, near 0
    • Assume wheel parameters are constant (same diameter, mass)

Q50 RS Gear RatioCorrect?
GearRatioGear Shift Ratio % Change (Hi to Lo)
1​
4.78​
54%​
2​
3.1​
57%​
3​
1.98​
45%​
4​
1.37​
37%​
5​
1​
15%​
6​
0.87​
12%​
7​
0.78​

Next steps:
  • Find sample dyno log data for Q50 with continuous Torque distribution and assess if there may be variable optimal shift strategies (please ping me if you have a sample data set)
Would love feedback on the modeling (I know we have some technical/engineering folks). It may be a fruitless endeavor with an obvious answer, but I am curious.

Also, feel free to chime in with how you shift to get the most out of your tune. I did not see much on this topic. I know there are a lot of factors (AWD vs. RWD, track vs. road, etc.) that won't be captured in a simple model, so good to get real-world feedback.
I applaud your effort but with all the variables associated with dyno data from multiple cars and dynos, I wonder if you'll find a definite answer.
 

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you're making this too difficult, just use this calc to determine everything youre looking for:


also, your calculations are correct, but also incorrect. its the wrong way to look at things.

1-2 is a 35% drop
2-3 is a 34% drop
3-4 is a 30.5% drop
4-5 is a 37% drop
5-6 is a 13% drop
6-7 is a 10% drop

the 4-5 shift is especially atrocious but you'd need a FAST Q50 in order to need 5th in the 1/4 mile. 4th tops out at 128mph with Sport final drive at 6500rpm. shifting in to 5th drops it down to 4700rpm. thats a huge drop at speed, all things considered. in lower gears, its less of a concern due to the length of time spent in gear. if i had a real fast Q50/60, id either hold 4th until i ran out of RPM or run a taller tire to stay in 4th if drag racing. for road racing, theres not really anything you can do.

most modern transmissions are designed with fuel economy in mind first, performance second. this applies to most sports cars as well and especially the Q50. look at the gearing, notice how 5-6-7 are very close? thats to maximize efficiency at highways speeds. due to the wide gear spacing (YES, even on 8/9/10 speeds), optimal shift point is nearly always redline, regardless of hp/tq curves.

lastly, maximum acceleration is not achieved at 0% tire slip, but rather somewhere between 5-10%. this is consistent across all types of tires. the reduction of slip percentage to near zero is why you see many vehicle lose mph but still drop ET when they go from street tires or DRs to slicks. the bias ply sucks up energy due to carcass design and the increased traction reduces slip to nearly 0% in many cases. suspension work restores most of the lost mph which then results in lower ETs.
 

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This has been discussed and calculated in several threads already. I posted the link from above as well as the results from multiple different dyno plots inputted. Conclusion was always the same. Rev her out, shift right before rev limiter/fuel cut. You would need a ridiculous torque drop off (much more than what the Q stock or fbo w/ tune etc… has) to justify short shifting.
 

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Discussion Starter · #5 ·
Cool thanks for the info! I guess I will save myself some time with that link. I have a tendency to jump straight into model building lol. Glad someone did it for me.

I will play around with the online calculator, but I can definitely believe it would take a dramatic drop-off to justify shifting early. Must have missed the other threads on this topic. Will have to dig a bit more to check them out.

Btw, the % change #'s were based on the analysis from the youtube video - basically defining the decision rule for when to short shift.. i.e. when the % gain from lower gear/higher GR is compensated by % change in engine torque when upshifting. Agree you could look at it either way depending on context.
 

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This has been discussed and calculated in several threads already. I posted the link from above as well as the results from multiple different dyno plots inputted. Conclusion was always the same. Rev her out, shift right before rev limiter/fuel cut. You would need a ridiculous torque drop off (much more than what the Q stock or fbo w/ tune etc… has) to justify short shifting.
This. I did the same thing and it always came out to shift at max RPM.
 

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The ideal shift time would depend on how the VR30 is tuned and the transmission gearing, the non RS models have a slightly
taller final drive but generally speaking you will always want to be closer to red-line for a shift for example.

If we used Boxy's dyno graph from a few year ago you can see he is making the most power around 4,800-6,000 RPM, so in order to remain
squarely in that portion of the powerband you'd want to shift around 6,200RPM.

So your short shifting just a little before red-line in order to get the most out of the engine, but its no means exact as the amount of
boost being tapered later in the RPM band varies based on a persons tune. Someone like Ddnspider who is running full catless DP's
and likely making more boost than Boxy will probably get the most going to Red-line instead.

101310
 

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The ideal shift time would depend on how the VR30 is tuned and the transmission gearing, the non RS models have a slightly
taller final drive but generally speaking you will always want to be closer to red-line for a shift for example.

If we used Boxy's dyno graph from a few year ago you can see he is making the most power around 4,800-6,000 RPM, so in order to remain
squarely in that portion of the powerband you'd want to shift around 6,200RPM.

So your short shifting just a little before red-line in order to get the most out of the engine, but its no means exact as the amount of
boost being tapered later in the RPM band varies based on a persons tune. Someone like Ddnspider who is running full catless DP's
and likely making more boost than Boxy will probably get the most going to Red-line instead.

View attachment 101310
This is entirely inaccurate.
See posts and links above.

you shift when the torque multiplied through the gearing to the wheel in the current gear is less than the torque multiplied through gearing to the wheel in the next gear. In that dyno you posted from boxy it would be redline/limiter. Not 6,200rpm.

i have calculated this with numerous dynos/varies builds. As mentioned in above post, You would need a crazy torque drop far acceeding even the Qs to warrant short shifting.
 
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The ideal shift time would depend on how the VR30 is tuned and the transmission gearing, the non RS models have a slightly
taller final drive but generally speaking you will always want to be closer to red-line for a shift for example.

If we used Boxy's dyno graph from a few year ago you can see he is making the most power around 4,800-6,000 RPM, so in order to remain
squarely in that portion of the powerband you'd want to shift around 6,200RPM.

So your short shifting just a little before red-line in order to get the most out of the engine, but its no means exact as the amount of
boost being tapered later in the RPM band varies based on a persons tune. Someone like Ddnspider who is running full catless DP's
and likely making more boost than Boxy will probably get the most going to Red-line instead.

View attachment 101310
super wrong. this is the plot using the dyno graph you provided with the correct trans and Sport final drive, though that won't change anything in this scenario. make sure you read the paragraph under the results, that will help you to understand why your logic is flawed.

Edit: oops, cut off the paragraph at the bottom, here it is:

How is this the correct method? For any point in time, the highest acceleration is acheived with the highest torque at the wheels. Gears multiply torque, so generally, the lowest gear provides the highest acceleration. The problem is, you can't go very fast in 1st gear, so you need to upshift to go faster, even though it means lower torque output. As long as the output torque in 1st gear is higher than output torque in 2nd for a given road speed, you should stay in 1st. Of course, you will soon run out of rpms and be forced to upshift.
Product Rectangle Font Slope Screenshot
 
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super wrong. this is the plot using the dyno graph you provided with the correct trans and Sport final drive, though that won't change anything in this scenario. make sure you read the paragraph under the results, that will help you to understand why your logic is flawed.

Edit: oops, cut off the paragraph at the bottom, here it is:
That's a pretty neat site I'll have to bookmark.

Buuuut you realize you confused the Torque and HP graphs at the higher RPM's when you entered that data right??? Which in fairness the dyno folks used the same damn color for the before/after results so an honest mistake.

But Boxy's dyno clearly showed he was making under 300 WTQ after 6,500 RPM, so plugging in the correct values
this is what we end up with these results...So as I alluded too in my previous post, due to the torque and power dropping off notably at higher RPM's there is value to short shifting.

101324
 

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That's a pretty neat site I'll have to bookmark.

Buuuut you realize you confused the Torque and HP graphs at the higher RPM's when you entered that data right??? Which in fairness the dyno folks used the same damn color for the before/after results so an honest mistake.

But Boxy's dyno clearly showed he was making under 300 WTQ after 6,500 RPM, so plugging in the correct values
this is what we end up with these results...So as I alluded too in my previous post, due to the torque and power dropping off notably at higher RPM's there is value to short shifting.

View attachment 101324
So a few things to note.
this is one of the biggest torque drop offs I’ve seen for this car. Most people don’t tune the car like that. As you even said this is an old dyno that even he doesn’t gimp the top end this much. No reason to.
I have ran this for stock red sport dynos, BMS JB4s highest map 6 dyno, as well as a few typical FBO tune, and FBO + E85 tune and they all had 6700+ shift points 1-4.

for the specific dyno that I’m not sure why anyone would run this tune especially now. When you input the correct information. (You had a few points incorrect)

You get 6.55, 6.7, 6.4, 6.3. But again this is the most pointlessly gimped top end. And even still I’d rev it out. Shifting pre fuel cut isnt 6800 you lose time banging limiter you shift just before to rev out but not hit limiter which is 6650-6700. definitely above 6200. And when using pretty much any other tune that most people would run you’ll find this rpm to hold true 1-4.

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hey thanks. im not sure what happened there, looks i got a few of the numbers wrong. i think i was distracted cause i was hungry and it was right before dinner, lol. thanks for the correction.

i dont think the data on that dyno run past 6500rpm is accurate. it looks like the run stopped at 6500. most other runs from tune only or light bolt on cars dont have a problem holding 300wtq (or more) to 6500rpm.

however, you initially indicated a red sport, so im guessing stock. i was more careful this time around and made sure to be correct, lol. i used red sport gearing and also used info from a stock dyno from fast intentions cause its a little less optimistic than a dyno from stillen or some other dynos around: https://www.fastintentions.com/imag...r Down Pipes/Q50_FICBE_LDP_vs_Stock_large.jpg

Font Rectangle Screenshot Parallel Technology


a tuned car might show slightly lower rpm shift points when plotted but the rpm spread is going to be fairly narrow, probably between 300-400rpm. i plotted two random tuned cars and the shift points didnt drop below 6700rpm until 3rd gear, and it didnt drop much after that either. theres potentially some merit to perfectly timed shifts but its not going to matter that much in the real world.

i do like the technical discussion though.
 
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Here is when I plotted BMS JB4 e30 +7psi map, also note the torque at 6000-6700 vs that boxy one and this is just a JB4 not custom tune which should be more. Given it has a lot less mid range than boxy dyno, but with that 6k+ torque added to the boxy dyno it still changes shift points up.
101334
 

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hey thanks. im not sure what happened there, looks i got a few of the numbers wrong. i think i was distracted cause i was hungry and it was right before dinner, lol. thanks for the correction.

i dont think the data on that dyno run past 6500rpm is accurate. it looks like the run stopped at 6500. most other runs from tune only or light bolt on cars dont have a problem holding 300wtq (or more) to 6500rpm.

however, you initially indicated a red sport, so im guessing stock. i was more careful this time around and made sure to be correct, lol. i used red sport gearing and also used info from a stock dyno from fast intentions cause its a little less optimistic than a dyno from stillen or some other dynos around: https://www.fastintentions.com/images/hosted_images/Infiniti/Q50 Sedan/Lower Down Pipes/Q50_FICBE_LDP_vs_Stock_large.jpg

a tuned car might show slightly lower rpm shift points when plotted but the rpm spread is going to be fairly narrow, probably between 300-400rpm. i plotted two random tuned cars and the shift points didnt drop below 6700rpm until 3rd gear, and it didnt drop much after that either. theres potentially some merit to perfectly timed shifts but its not going to matter that much in the real world.

i do like the technical discussion though.
Hah its all good, the tuner was a mad-man for using the same colors in his graph!

I think the data on the run itself is accurate they did stop the run shortly before red-line which is a bit odd but the reason for the lower WTQ numbers is likely because its a JB4 tune
rather than a ECUTEK as JB4 owners usually trim boost a fair bit at higher RPMs as the turbos are well outside their efficiency range. Which is why I had pointed out tuning being
a factor in my original post. ;)

With that said I agree the merits of a timed shifts on this platform aren't going to major in the real world
and I'm always happy to see a thread like this one pop up.
 
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the reason for the lower WTQ numbers is likely because its a JB4 tune rather than a ECUTEK as JB4 owners usually trim boost a fair bit at higher RPMs as the turbos are well outside their efficiency range. Which is why I had pointed out tuning being
a factor in my original post. ;)
It clearly says ecutek in the dyno graph you posted, also no JB4 is making that much WTQ in the mid range.

101335
 

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It clearly says ecutek in the dyno graph you posted, also no JB4 is making that much WTQ in the mid range.

View attachment 101335
Grabbed it off the link of the Q50 Dyno thread for Boxy's and it he was on JB4 according to the post at that time,
so not sure what's going on there. Maybe the tuner miss-labeled the file or I copied on the wrong link.

But in any event the type of tune being JB4 or ECUTEK itself isn't a huge deal, the results of the tune itself are what matter
and anyone with a tuned car would need to plugin their own numbers to see what shift-points work best for them as the Tune
is such a large variable.
 

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The results of the tune itself are what matter
and anyone with a tuned car would need to plugin their own numbers to see what shift-points work best for them as the Tune
is such a large variable.
This I agree with, I think generally speaking for majority of people redline will be most optimal, and what I would typically recommend if someone didn't have a personal dyno to reference, but agreed there definitely can be situations where this wouldn't necessarily be the case, most likely on a subpar ecutek tune as it is really unnecessary for such a drastic torque drop that would warrant a short shift.
 
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This I agree with, I think generally speaking for majority of people redline will be most optimal, and what I would typically recommend if someone didn't have a personal dyno to reference, but agreed there definitely can be situations where this wouldn't necessarily be the case, most likely on a subpar ecutek tune as it is really unnecessary for such a drastic torque drop that would warrant a short shift.
Mash the go pedal to the floor, hang on the steering wheel with both hands, and let the A/T do the shifting. Easy peasy!
 
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