Ok, I didn't quite understand what you meant by imperceptable - thank Honcho- that makes perfect sense. So it sounds like there are some parts other than just the gear set that you need? Right? A new mainshaft and bearings, yes - how much is that? I'm just tallying up the expense - cause I know I'll have to do this too.
-
Protip: Profile posts are public! Use Conversations to message other members privately. Everyone can see the content of a profile post.
Short Gear Review
- Thread starter Honcho
- Start date
Ok, I didn't quite understand what you meant by imperceptable - thank Honcho- that makes perfect sense. So it sounds like there are some parts other than just the gear set that you need? Right? A new mainshaft and bearings, yes - how much is that? I'm just tallying up the expense - cause I know I'll have to do this too.
Honda...way too conservative...should have...would have...could have...short gears should have been standard...among other things...!!!!
As "nsxtasy" has said. "Short gears" is a misnomer since the only thing 'short' about it is the 1-2 shift, while the 3-4 and 4-5 shifts have a (slightly) larger RPM drop than the standard US gear ratio.
*From a marketing standpoint. The 'all-important' 0-60 time is worse in the US ratio than the JDM gear set. Still dosn't make sense to even have the US ratio...
Where did these figures come from?
*From a marketing standpoint. The 'all-important' 0-60 time is worse in the US ratio than the JDM gear set. Still dosn't make sense to even have the US ratio...
Last edited:
+1 These figures have been referred to several times before, but to my experience make no sense. THREE-PLUS seconds more 70-150? I doubt it. Maybe those numbers are reversed?
Lots of folks just hit the internet and copy what they find -- doesn't have to be the actual facts.
Last edited:
If you only change out your second gear, then you are shortening the gap between first and second, but lengthening the gap between second and third. By changing out gears 2 through 4, the wider spacing is spread out more (between third and fourth, and between fourth and fifth).
I am only guessing, but I can think of two possible reasons. They may have done it to increase the car's fuel economy numbers. You'll recall that somewhere around that time, for the same reason, Chevrolet had a design "feature" on the Corvette in which the automatic upshifted from first to fourth unless you were really hammering the throttle. The other possibility is that they were optimizing the car's performance on the racetrack by having second through fifth, the gears used on the track, closely spaced, and having a big gap between first and second, where it doesn't matter.
They come from an extensive analysis that Bob Butler performed and published in a series of articles published in NSX Driver, the magazine of the NSX Club of America. The model, algorithms, and equations he used were explained in the article. He compared acceleration figures for each 10 mph interval (as well as for 1/4 mile acceleration) for the various gearsets and the various models and years of the NSX, as well as for hypothetical horsepower additions and weight reductions. The numbers produced by his model correlated just about perfectly with actual test results performed by the major automobile publications.
And yes, the stock gears really ARE over three seconds faster from 70 to 150, and the short gears really are 0.3 second faster from 0 to 70. Look at the gearing differences and you'll see why (numbers below assume the 4.062 R&P in both cases):
Up to 45 mph, both sets have the same gearing
From 45 mph to 73 mph, the short gears are 13 percent shorter
From 73 mph to 81 mph, the stock gears are 23 percent shorter
From 81 mph to 101 mph, the short gears are 14 percent shorter
From 101 mph to 114 mph, the stock gears are 19 percent shorter
From 114 mph to 139 mph, the short gears are 7 percent shorter
From 139 mph to 144 mph, the stock gears are 25 percent shorter
Above 144 mph, both sets have the same gearing
So the short gears are a little bit shorter (7-14 percent shorter) at speeds in which both gearsets are in the same gear, but the stock gears are a whole lot shorter (19-25 percent shorter) at speeds in which the short gears force you into a higher gear while the stock gears keep going up to a higher speed in the lower gear.
Last edited:
I always figured why the nsx can keep up with more powerful cars that weight similar on the higher speeds is because we were always in one gear lower than the other car at the same speed. I guess my theory did have some ground to stand on.
Yes, absolutely. Gearing has as much effect on acceleration as the torque that comes out of the engine. There's a very good write-up by Bruce Augenstein on torque, horsepower, and gearing, and what they all mean to acceleration; click here to read it.
nsxtasy;1356414 And yes said:
Last edited:
There's the challenge!
Gentlemen: Grab your magazines, start your arm chairs and.......GO!!!!:biggrin::biggrin:
Last edited:
Where do you get these cool pictures - you oughta be a comedic writer....lol - this is a good one Joe!
There's the challenge!
Gentlemen: Grab your magazines, start your arm chairs and.......GO!!!!:biggrin::biggrin:
I wrote the articles that Ken is referring to and if you have any questions I can try to answer them from memory. The computations were a finite-difference model calculating acceleration with an inputted horsepower curve and assumed aerodynamic model. In my opinion this is the only way to properly compare gear sets because you can hold everything else constant. Pro race teams can do the same type analysis to determine the most likely optimal gear set for a particular track before they arrive. Changes to gearing in general are never always an improvement. For any given racetrack, one set of gearing will be better than another, but may be worse at a different track. The third article I wrote looked at gearing on road courses and specifically looked at the time lost or saved over a given distance starting from different corner exit speeds. An old thread and some of the graphs from that article can be found here:
http://www.nsxprime.com/forums/showthread.php?t=44961&page=2
I just noticed this is my 400th post in a little more than 10 years (not counting the old list serve).
Bob
http://www.nsxprime.com/forums/showthread.php?t=44961&page=2
I just noticed this is my 400th post in a little more than 10 years (not counting the old list serve).
Bob
Last edited:
Ah, the old listserve. :smile: I wish I could have kept my trap shut and just observed as much as you have.
But the articles that you wrote contain good information. Thanks for your input.
Last edited:
- Joined
- 15 May 2004
- Messages
- 6,898
Bob's post and graphs helped me a lot while deciding which route to go, short gears or short gears/4.23.
Congrats to your 400th post.
While gearing 1 may be good for one track and gearing 2 at another track there's also the distinction between cars being driven on the track and cars driven in a different scenario like mountains and speed-limits.
Congrats to your 400th post.
While gearing 1 may be good for one track and gearing 2 at another track there's also the distinction between cars being driven on the track and cars driven in a different scenario like mountains and speed-limits.
- Joined
- 15 May 2004
- Messages
- 6,898
Good old times. :wink:been awhile since I've seen that avitar Bob
Just was out "testing" my short gears. Cop pulled me over on the way home to compliment the car.
EDITED with US 91-94 & 95-96
According to my gear chart (using a 245/40-17 tire)
a) US (91-94)/4.06
b) US (95-96)/4.06
c) JDM/4.06
d) JDM/4.235
MPH @ 8,000RPM:
a) 47 - 84 - 118 - 150 - 188
b) 47 - 80 - 118 - 150 - 188
c) 47 - 74 - 103 - 140 - 188
d) 45 - 71 - 99 - 134 - 180
MPH @ 6,100RPM (V-tec crossover):
a) 36 - 64 - 90 - 114 - 143
b) 36 - 61 - 90 - 114 - 143
c) 36 - 57 - 79 - 107 - 143
d) 34 - 54 - 76 - 103 - 137
MPH @ 3,200RPM:
a) 19 - 34 - 47 -60 -75
b) 19 - 32 - 47 - 60 -75
c) 19 - 30 - 41 - 56 - 75
d) 18 - 28 - 40 - 54 - 72
RPM after Redline Up-shift:
a) - 4,499 - 5,698 - 6,289 - 6,378
b) - 4,689 - 5,467 - 6,289 - 6,378
c) - 5,085 - 5,738 - 5,903 - 5,971
d) - 5,085 - 5,738 - 5,903 - 5,971
RPM Drop
a) - 3,501 - 2,302 - 1,711 - 1,622
a) - 3,311 - 2,533 - 1,711 - 1,622
b) - 2,915 - 2,262 - 2,097 - 2,029
c) - 2,915 - 2,262 - 2,097 - 2,029
The RPM drop and gear spread of the JDM gear set is more even than the US gear set which has a much larger RPM drop from 1-2, similar 2-3, then shorter 3-4 and 4-5 shifts (keep in mind for most tracks the 4-5 shift is probably irrelevant since there aren't a ton of tracks where a stock NSX would get up over 150mph). Because of this, the JDM gear set should be faster in the first 3 gears (up to 118mph) and then start to lose ground above 118 slightly. I like the JDM gear ratio.
Billy
According to my gear chart (using a 245/40-17 tire)
a) US (91-94)/4.06
b) US (95-96)/4.06
c) JDM/4.06
d) JDM/4.235
MPH @ 8,000RPM:
a) 47 - 84 - 118 - 150 - 188
b) 47 - 80 - 118 - 150 - 188
c) 47 - 74 - 103 - 140 - 188
d) 45 - 71 - 99 - 134 - 180
MPH @ 6,100RPM (V-tec crossover):
a) 36 - 64 - 90 - 114 - 143
b) 36 - 61 - 90 - 114 - 143
c) 36 - 57 - 79 - 107 - 143
d) 34 - 54 - 76 - 103 - 137
MPH @ 3,200RPM:
a) 19 - 34 - 47 -60 -75
b) 19 - 32 - 47 - 60 -75
c) 19 - 30 - 41 - 56 - 75
d) 18 - 28 - 40 - 54 - 72
RPM after Redline Up-shift:
a) - 4,499 - 5,698 - 6,289 - 6,378
b) - 4,689 - 5,467 - 6,289 - 6,378
c) - 5,085 - 5,738 - 5,903 - 5,971
d) - 5,085 - 5,738 - 5,903 - 5,971
RPM Drop
a) - 3,501 - 2,302 - 1,711 - 1,622
a) - 3,311 - 2,533 - 1,711 - 1,622
b) - 2,915 - 2,262 - 2,097 - 2,029
c) - 2,915 - 2,262 - 2,097 - 2,029
The RPM drop and gear spread of the JDM gear set is more even than the US gear set which has a much larger RPM drop from 1-2, similar 2-3, then shorter 3-4 and 4-5 shifts (keep in mind for most tracks the 4-5 shift is probably irrelevant since there aren't a ton of tracks where a stock NSX would get up over 150mph). Because of this, the JDM gear set should be faster in the first 3 gears (up to 118mph) and then start to lose ground above 118 slightly. I like the JDM gear ratio.
Billy
Last edited:
These number illustrations are interesting but do they tell the whole story?
Of course the taller gears are going to top out at a higher mph BUT doesn't it take longer to do so? Wouldn't the shorter gears put that car out ahead since it reaches it's speed quicker? I'm referring to on a road course more than a drag strip.
Pulling out of a corner with less of a rev drop, wouldn't the short gears put that car up the track ahead of the other car?
Of course the taller gears are going to top out at a higher mph BUT doesn't it take longer to do so? Wouldn't the shorter gears put that car out ahead since it reaches it's speed quicker? I'm referring to on a road course more than a drag strip.
Pulling out of a corner with less of a rev drop, wouldn't the short gears put that car up the track ahead of the other car?
Woops - Joe you're applying logic again - I don't know but that sure sounds right to me....:wink: I can't believe you didn't include some really deranged picture to make that point.
All seriousness - that really does seem like it what the gear set is supposed to do. That sounds like what ole Honcho was describing in his own personal testing.
- I don't know but that sure sounds right to me....:wink: I can't believe you didn't include some really deranged picture to make that point. All seriousness - that really does seem like it what the gear set is supposed to do. That sounds like what ole Honcho was describing in his own personal testing.
The top speeds, actual gear ratios, and RPM drops are shown in the FAQ/Wiki at http://www.nsxprime.com/FAQ/Technical/gearratios.htm
Billy, I think somethings wrong in your numbers. I haven't checked all of them, but for example, you show an RPM drop to 5467 when upshifting from second gear to third with the stock USIM gears. The FAQ/Wiki says that number should be 5698, which is also what you get when you calculate it based on the gear ratios (1.230/1.727*8000=5698). That's why I said the proportional gap between second and third, and the corresponding RPM drop, are virtually identical between the JDM gears and the USIM gears (5738 vs 5698 RPM after the 2-3 upshift).
Let me see if I can illustrate.
Lets just say we have two identical NSXs except the gearing. Lets say both NSX's come out of a turn at the same speed and next to each other and are under full acceleration. Both cars are in second gear at 60mph at full throttle. The car with the short gears is at about 6500 RPM, and the car with OEM gears is at 6000 RPM. For the next second or so (before It hits red line) the car with short gears is slightly faster due to the second gear ratio. but then the car with short gears hits red line and shifts.
Now the NSX with OEM gears doesn't need to shift yet, so it can stay in second. So the NSX with short gears is in third, and the NSX with OEM gears is still in second. Guess which one is faster now! until the NSX with OEM gears has to shift it will be faster.
Same thing happens when the cars get to the point where the short geared car needs to shift into fouth, only now the difference is even more.
You may notice the NSX with short gears is staying in Vtec range more than the OEM gearing, but it does not matter because the there is really no torque difference before, during, or after the Vtec switch over point.
But aren't you still at max torque in both cars whether in second or third - and if your coming out of a turn and the US car is still in second and the JDM car is now in third with a lot more room with shorter gearing in third he's gonna leave you while you shift into third at a lower rpm. Isn't that the real difference?
In my mind - maybe that's the only place this works - but it seems like they wouldn't be putting short gears in an NSX-R if it didn't make it more responsive and faster at the track.
In my mind - maybe that's the only place this works
- but it seems like they wouldn't be putting short gears in an NSX-R if it didn't make it more responsive and faster at the track. No, not the same torque. It may be the same torque at the engine but different torque at the wheels if they are in different gears or gear ratios. Remember the transmittion gears acts as a torque multiplier.
That's a good analogy.
One other thing worth mentioning is that the car with short gears will SEEM faster because it takes less time until you need to upshift. However, much of that perception is simply perception rather than actual acceleration, because the upshift takes place at a lower road speed, which doesn't register in terms of perception the way the time to shifting does.
As H notes, the transmission gears act as a multiplier, but the torque doesn't vary much. With the NSX, the torque curve (torque at the crankshaft) is very flat, with less than 10 percent variation in torque between something like 4000 and 7500 RPM. So what matters is gearing, rather than engine torque. At any given speed (above 25 mph), whichever NSX has shorter gearing is faster.
Last edited:
