5 vs 6 Speed /w K24a2

[Slip_Angle]

Guys,

I have an EP3 with K24a2 and stock 5 Speed with LSD. I've been pondering changing to a 6 speed but wonder what the actual difference would be in terms of acceleration / 1/4 mile times. The engine makes 221whp and 190tq.

I tried to find a 1/4 mile calc that allows the input of gear ratios but had no luck. Any of you drag racers have feedback you can provide?

5 Speed Ratios

FD:4.764
1st:3.062
2nd:1.769
3rd:1.212
4th:.921
5th:.738

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http://www.zealautowerks.com/transcalc.php

I graphed the 05-06 RSX-S Transmission and the EP3 5 Speed with 215/45/17 tires and an 8000rpm redline.

The EP3 5 Speed reaches 101.52mph in 3rd gear @8000rpm

The RSX-S 6 Speed reaches 88mph in 3rd so needs a shift to 4th where it can reach 116mph. So, given the 6 speed needs that extra shift, is the 5speed more suited for the 1/4 mile in this case or is the 6 speed better?

[Ba82Ep3]

Theres a sticky on k20a.org with pretty much all k trans combinations mapped out with theoretical mphs too.

The 06+SI 6 speed is pretty close to the ITR/CTR trans (ratio wise). An EP 5 speed with the TSX/FG 6th gear set combined with the 5.0 CTR final drive gets you damn close to an ITR trans with a 4.7 final. You just dont have triple synchros on all the gears with the EP trans.

[Slip_Angle]

Theres a sticky on k20a.org with pretty much all k trans combinations mapped out with theoretical mphs too.

The 06+SI 6 speed is pretty close to the ITR/CTR trans (ratio wise). An EP 5 speed with the TSX/FG 6th gear set combined with the 5.0 CTR final drive gets you damn close to an ITR trans with a 4.7 final. You just dont have triple synchros on all the gears with the EP trans.

So you're saying get a 6 Speed?

[Ba82Ep3]

Or at least swap the guts of your EP trans with 6 speed parts. Theyre interchangeable.

Triple syncs are nice to have with short gears and a decent amount of power.

I started a 6 speed rebuild thread in the trans section. Its pretty detailed but unfinished as of yet. Life has a way of altering plans...

[AKEP]

back in the day someone did a rsx 6 speed swap, stock a3 motor. same 1/4 times. its like 200hp area is the grey spot where you don't benefit from gear ratios or something. at least in 1/4 mile. auto-x, you would def benefit from shorter gears around slow areas to stay in the powerband.
but like ba82 was saying, swap out the z3 trans guts and see if you like those instead. you can keep your lsd just swap the ring gear (and replace those bolts) - usually less shifting is better, unless the rev drops too low to produce power, then that is when you want shorter ratios.

[Ba82Ep3]

Definitely. If youre going to a shorter gear and or higher (not taller) final drive, youre gonna be shifting sooner. The benefit of the higher ratio will be negated by longer shift times for fear of grinding the syncs. IMO, if youre gonna crack the trans open... do it up and do it right.

But there IS a less expensive option for those who just want the shorter gear pull w/o all the work... just add the 6th gearset and the 5.0FD. Like anything performance related... it depends on your end use.

[Slip_Angle]

I found a TSX transmission with 32K on it. Price is 900 delivered. How hard is it to swap the guts?

Alternatively I found an 06 Si transmission with 85K for $950 delivered.

What's easier / better?

[Slip_Angle]

back in the day someone did a rsx 6 speed swap, stock a3 motor. same 1/4 times. its like 200hp area is the grey spot where you don't benefit from gear ratios or something. at least in 1/4 mile. auto-x, you would def benefit from shorter gears around slow areas to stay in the powerband.
but like ba82 was saying, swap out the z3 trans guts and see if you like those instead. you can keep your lsd just swap the ring gear (and replace those bolts) - usually less shifting is better, unless the rev drops too low to produce power, then that is when you want shorter ratios.

I'd like to see this information. I'm right on the 200whp mark with the k24 and am debating if it's worth going to a 6 speed. From what I understand 1st and 2nd are effectively the same between the EP3 5 Speed and 02-04 RSX-S 6 Speed. The big difference is the long 3rd gear in the 5 speed.

Does the power I have in the K24 make up for it vs. the extra shift required for the 6 speed or is the 6 still superior and by how much in say the 1/4 mile?