6 speed vs. 5 speed acceleration comparison

I posted this at the bottom of another topic, but I thought I would re-post this here to get a little more discussion.

There is a lot of discussion of which is better the 5 or 6 speed, and a lot of talk about how the 6 speed is slower or that it will be slower to 60 (as if that arbitrary number is god).

I thought I would devote some time to actually plotting and discussing the acceleration of typical setups, here you go:

In an effort to fully disclose, I will say that I am in favor of the 6 speed. I like the idea of having the next gear. I like the idea of possibly getting better gas mileage. I like the cachet associated with the 6 speed. I like the known durability of the 6 speed, and the possibly better clutch.

That said, I tried to be as scientific as possible about this, I did not try to skew the results to benefit the 6 speed in any way. I used the same HP numbers, and same driver shift speeds. Both cars are using the optimum shift points (not always redline), and have the weights adjusted appropriately.

I use a program called Car Test 2000. It is a vehicle acceleration simulator. I use it very often to compare acceleration times. It is, in my experience, accurate to within .1 in the 1/4 mile, and 3-4 mph in top speed. I highly recommend it.

It will accept actual at wheels hp numbers and is very customizable. For example, I found I was regularly getting better numbers at the track than it estimated, so I lowered the shift times and the numbers lined right up (I guess I am awesome at shifting).

I have attached 4 PDF files with acceleration plots comparing the 07 spec B to a 05 GT. Stock gear ratios and stock wheel sizes.

The first plot is Stock engine (also default shifting speeds). The spec B is teal, the GT pink. You can see that as predicted the 0 to 60 is slower for the spec b because of the shift point. You can also see that the 6 speed is faster to 50, 70, 80, slower to 90, but much faster to 100, and continues to pull away at higher speeds. This is to be expected because how the car makes power at high rpm when stock. This is why peaky cars like a s2k or TSX really need that extra gear. *NOTE: I did not take into account the fact that spec b's may actually be making more power when stock, as discussed in Rallitek's dyno comparison. For this test (and all of the other ones), both cars are EXACTLY the same in power.

What about a stage 2 car? It makes its power at a lower rpm, and makes a LOT of torque at low rpm, it is advisable to short shift the 5 speed a little, let alone a 6 speed, so how does the spec b do?

For the stage 2 comparison, colors are the same (pink: GT, teal: Spec B), I used my actual dyno plot, higher redline (7200 rpm) and quicker shifts.

As you can see the 0-60 that people care so much about is exactly the same. In fact the plot shows identical performance except during those tenths of seconds where the GT is in the lower gear. I am calling this a tie, but if you want to get technical the GT is faster to a couple of points, and MIGHT have a slight edge at the high end of the speeds recorded here.

For Shifts and Giggles I plugged in the dyno numbers from the TDC 40BB turbo, which has Stg2 VF40 spool, but a MUCH better top end. Even this turbo is falling off at the high rpm, most likely because of the still stock cat back in this dyno. Same colors, same shift speeds and high redline as in the stg 2 plot.

Here the VERY slight edge goes to the spec B, probably because of the higher rpm power.

To conclude, the better driver of any of these cars is going to win. Same driver, the winner will swap back and forth, no matter the power levels. The differences are so small as to be inconsequential in terms of actual acceleration between the two cars. The only differences come when there is high end power (like a big turbo), then the advantage will go to the spec B for its ability to keep the rpm up, because of the closer gear ratio's. Also if you run the 1/4 a lot, and have BIG power, you may have to shift out of 4th to cross the finish line (like with traps over 118 mph), this could hurt a little. Also the slightly shorter 2nd gear might be bad in a fast autocross.

Since acceleration is the same, the other benefits of the 6 speed seal the deal for me. Better theoretical gas mileage, less wear and tear on the engine at highway speeds, better gear choices on the twistys, or a road course, being cooler because of the 6th speed . The ONLY downfalls are the extra cost associated with the Spec B, and possibly having less power to pass at highway speeds (although I have also plotted this, and the difference above 65 is minor). I plan on stepping up to a 08 spec B, and not looking back at my 5 speed GT.

EDIT: Added more turbos

Stock.pdf

Stage 2.pdf

Stg 3 40BB.pdf

AVO 420.pdf

TDC GT30.pdf

Speed in Gears 7200 redline.pdf

Here I'll briefly talk about what is, in my opinion, the biggest drawback to the 6th gear. That is top gear acceleration. Right now my stage 2 5mt is REDICULOUS fast in 5th. I mean engage the cruise control and hit resume and people complain and sue me for whiplash.

I like this, even though it results in terrible gas mileage and excess oil consumption. It is nice to pass on a two lane road and not downshift.

Here are the time differences in acceleration in top gear and best possible gear (in seconds):

Stock Top gear

...............5MT.......6MT

30-50......29.........80

50-70......11.........23

70-90......8...........10

Stock Best Possible (downshifting)

................5MT......6MT

30-50.......2.3.......2.2

50-70.......3.6.......3.4

70-90.......5.5.......5.0

Stage 2 Top Gear

................5MT......6MT

30-50.......9.8.......13.6

50-70.......5.6.......9.2

70-90.......4.6.......5.7

Stage 2 Best Possible (downshifting)

................5MT......6MT

30-50......1.63.....1.58

50-70......2.44.....2.39

70-90......3.19.....3.26

For comparison here are the times for a couple of Stock cars (I might add to this if I have time):

.................TSX.....A4 2.0T.....S40 T5 AWD

30-50.......12.2.........18.5.............123.06

50-70.......11.8.........11.3.................38.6

70-90.......13.7.........14.8.................15.7

Nice write-up!

I am all for the 6-speed as well. 1/4 mile times of the STI suffered due to shifting to fourth, but our 6-speed has different ratios so I don't think it would matter much.

Out of curiousity did you account for the app 100lb weight difference?

If the SpecB is actually more powerful than a regular LGT, isn't the test flawed from the start?

Possibly if you are talking about stock vs. stock, but that was one dyno that was high, and the difference could also be accounted for because of the lower actual ratio in third that the pull is done in.

In short, there is no proof that all spec b's have more horsepower stock.

Either way this is a discussion about the transmission ONLY.

Nice write-up!

 

I am all for the 6-speed as well. 1/4 mile times of the STI suffered due to shifting to fourth, but our 6-speed has different ratios so I don't think it would matter much.

 

Out of curiousity did you account for the app 100lb weight difference?

Thanks, yes I did take the extra weight into account.

isn't the 0-60 of the spec.B supposed to be somewhere around 5.4 seconds?

I don't think anyone has actually tested the 6 speed yet. But the actual numbers are not the point here, this is a comparison between the different transmissions.

wow! GREAT write up!

Very interesting. I think that program would be a lot of fun to play with

wow! GREAT write up!

 

Very interesting. I think that program would be a lot of fun to play with

Thanks!

Here's the link to the software I used:

http://www.cartestsoftware.com/cartest2000/index.html

Awesome info, so when are you trading in for the 08 spec b?

Thanks!

Not going to trade my baby in for a little while yet. I still love my car and am trying to build some equity in it first...

I just wanted to dispel some of the "the Spec B is going to be teh slower, because of the 6 speed, oh noes!!!!!111one" and similar comments.

isn't the 0-60 of the spec.B supposed to be somewhere around 5.4 seconds?

Best published time for the 06 Spec.B is 5.1 seconds.

Best published time for the 06 Spec.B is 5.1 seconds.

06 has the 5 speed... But you know that don't you?

06 has the 5 speed... But you know that don't you?

Hence the faster 0-60 time. Then there is also that direct dyno comparison result that showed an 07 Spec.B engine to have more power than an 05 LGT.

It would be interesting (and beyond my ability) to deduce hp/torque based upon published 0-60 times using that software.

Hence the faster 0-60 time.

So?

The 07 will be faster to 50, 70, 80 and all speeds over 95. Because of the 6 speed. (As shown above.)

Why is there this obsession with 0-60? It is an arbitrary number...

Seems to me that there was a time when 0-60 times were indicative of a car's power:weight ratio, and they are still widely believed to be so.

At some point the manufacturers realized that with the right gearing and redline they could hit 60 in 2nd to shave a fraction of a second. This may or may not have been a good thing for drivability in general, but it probably sells more cars.

Want to see the average sports car's 2nd gear get taller? Persuade a few car magazines to start using 0-70 instead.

But mostly I just wanted to say thanks to trabbic for doing the numbers. Math FTW!

My main objection is that the extra shifting just isn't worth it. I drove an STi for an hour and knew I wouldn't want it long-term. The Spec B isn't that short but it isn't far from it either. Even if the 6spd was a tenth of a second quicker, I'd be tired of all the extra gear changes during normal driving. Hell, I complain about the 5spd's too-short gearing! My 92 Stealth had a 5spd that could do 90 in second (not a typo) and 125 in third, yet it suffered no issues with acceleration as evidenced by its 12.9 @ 105 timeslips with a downpipe & MBC (an improvement of a full second over stock).

Why is everyone so sure the Legacy-spec 6spd is so much more durable than the 5spd? Has anyone broken the 5spd yet? It's not an 02 WRX!

For the stock turbo, the 6spd extracts the max performance. Once you upgrade, I'll bet a larger turbo will benefit from the longer power band of the 5spd. More shifting would just net more lag instead of uninterrupted acceleration.

Once you've owned a car with a worthwhile 6spd, having one just for the sake of six gears isn't enough. In my 94 Stealth, 70 in second was nice (as opposed to the 5spd's 90 mentioned above), as was 2300 rpm at 70 in 6th. That's the kind of spacing a car with the Legacy's power needs, not Civic gearing. Turbo cars make v8-like power with v8-like delivery; why not gear them similarly as well?

I don't see a 6spd as a status symbol. They've been commonplace for maybe 15+ years and you can find them on a dozen or more cars now. If it is available on a Sentra, it isn't fancy!

If my math is right, the 6MT Legacy should also do 2300 rpm at 70, and it should do 66 at 7000rpm in 2nd. Is that not close enough to what you are looking for?

And 97mph in 3rd. Whoah.

My main objection is that the extra shifting just isn't worth it. I drove an STi for an hour and knew I wouldn't want it long-term. The Spec B isn't that short but it isn't far from it either. Even if the 6spd was a tenth of a second quicker, I'd be tired of all the extra gear changes during normal driving. Hell, I complain about the 5spd's too-short gearing! My 92 Stealth had a 5spd that could do 90 in second (not a typo) and 125 in third, yet it suffered no issues with acceleration as evidenced by its 12.9 @ 105 timeslips with a downpipe & MBC (an improvement of a full second over stock).

The problem is, that with gearing that tall in first, you are putting a LOT more stress on the gears during a launch than with the short first gear we have now, and the even shorter first gear in the 6 speed. The advantage is that we can have the short first gear (to put less stress on the transmission and clutch) and still keep that high final drive.

Why is everyone so sure the Legacy-spec 6spd is so much more durable than the 5spd? Has anyone broken the 5spd yet? It's not an 02 WRX!

I am having a similar argument in another thread, and I agree with you, I know the 5 speed is VERY durable, it is just that the 6 speed is more proven, there are a heck of a lot of STi's running around with more power that any legacy.

For the stock turbo, the 6spd extracts the max performance. Once you upgrade, I'll bet a larger turbo will benefit from the longer power band of the 5spd. More shifting would just net more lag instead of uninterrupted acceleration.

I compared this (a 40BB), at best it closes the gap with the 6 speed, the 6 speed still comes out ahead. If you want I will do a big turbo like a 20g or something bigger if I can find a dyno.

Once you've owned a car with a worthwhile 6spd, having one just for the sake of six gears isn't enough. In my 94 Stealth, 70 in second was nice (as opposed to the 5spd's 90 mentioned above), as was 2300 rpm at 70 in 6th. That's the kind of spacing a car with the Legacy's power needs, not Civic gearing. Turbo cars make v8-like power with v8-like delivery; why not gear them similarly as well?

All V8 cars today that come with a stick have a 6 speed (Mustang GT=exception). The gearing is the Spec B is very similar to what you mention above, especially with an increased redline from a tune. @7300 rpm (my redline) 2nd gear is 65mph, 2500 rpm @70 mph.

I don't see a 6spd as a status symbol. They've been commonplace for maybe 15+ years and you can find them on a dozen or more cars now. If it is available on a Sentra, it isn't fancy!

Exactly! The Legacy is lacking behind. Name one sporty car (not Mustang GT, or WRX ) with a 5 Speeed. As you said even a Sentra has a 6 speed!

If you want I will do a big turbo like a 20g or something bigger if I can find a dyno.

I posted up some bigger turbo's, an AVO420, and a TDC GT30.

The 5 speed is better at speeds above 150 when the shift into 6th happens. I didn't graph it, the 6 speeds top speed is higher, because the 5 speed runs out of gear

Either way the graph is so close below 140 or so, as to make them virtually the same.

The program also does Time to Distance (kind of like a drag race), and for all these comparison, except the stock one, the difference is not measurable. In the stock one the difference puts the 6 speed about 20 feet ahead at speeds over 100, until then it is pretty close.

If the SpecB is actually more powerful than a regular LGT, isn't the test flawed from the start?

There is no difference is specs between a spec b motor and a regular LGT motor:icon_mrgr

^ The 2.5l turbo boxer doesn't really need a six speed and there is that weight penalty. However if you plan to mod the engine, having a more robust tranny can be considered a definite plus.

I really need one:icon_bigg