nitz

iTrader: (3)

Hey All,
I need some advice regarding a transmission upgrade to get the best out of my EvoGreen setup. Relevant mods are as follows.
Mitsubishi Evolution VI RS
Revolver Cams (set straight up with cam gears, degree wheel and dial guage.
They were anything but correct at 0,0. Actual setting to achieve published specs were -11,0!!)
Ported stock intake manifold, exhaust manifold and throttle body
Tubular 02 housing and 3" exhaust
Greddy Spec M Intercooler (47C @ 7500rpm with 23C Ambient)
EvoGreen ported, 18psi Actuator
2.2Bar @ 3900RPM - 6800RPM then tapering to 1.8Bar by 7500rpm
JDM RS Transmission
1st 2.785
2nd 1.950
3rd 1.444
4th 1.096
5th 0.825
Final Drive 4.875

Unfortunately, I don't have access to a dyno in order to figure out my optimal shift points from the torque curve. However, best guess by feel and looking at the rate of tacometer movement would be.

1st - 7300 - 40mph
2nd - 7100 - 56mph
3rd - 6900 - 73mph
4th - 6800 - 95mph
5th - 116mph@6200rpm

On my only 1/4 run this netted me 11.6@116 with a 1.9 60'. I know most people hold fourth, but with this ratio and cams, you are going to have to shift 5th anyway so you might as well make more use of the power band. On this run I didn't do a very good job of meeting my shift points.

Well on to my question. I'm wondering if a different ratio would help my setup stay in the sweet spot longer and lead to a quicker drag time. Would it be best to put a 4.11 final drive in my current transmission or replace it entirely with a Evo VIII 5-speed? Below are some of the rpm/mph to expect with both. I have to say though that my current ratio is a blast on tight roads, and wouldn't want to stray to far from it.

Evo VI RS with 4.11 Final Drive

rpm 1 2 3 4

6800 45 64 86 114
6900 45 65 88 115
7000 46 66 89 117
7100 47 67 90 119
7200 47 68 91 120
7300 48 69 93 122
7400 49 70 94 124
7500 49 70 95 125
7600 50 71 96 127
7700 51 72 98 129
7800 51 73 99 130


Evo VIII with 4.529 Final Drive

rpm 1 2 3 4

6800 39 58 80 110
6900 39 59 82 111
7000 40 60 83 113
7100 40 61 84 115
7200 41 61 85 116
7300 41 62 86 118
7400 42 63 87 119
7500 43 64 89 121
7600 43 65 90 123
7700 44 66 91 124
7800 44 67 92 126


Thanks for the help.

nitz

iTrader: (3)

anyone??

9sec9

iTrader: (2)

nitz, In the OKIX car, we use the stock IX 1-3rd and the VIII 4th gear. Stock final drive of 4.529. I think SLIGHTLY better than that would be the VIII 3rd gear, but not by much. As far as final drive ratio, the smaller turbos can use the 4.529 to help with the power on the street. It only comes in to play when you're going to spin past 8000 in 4th and the need to go to a taller gear (5th in this case) to get you to the finish line. If you're really close to the line, you can hold 4th and raise the rpm slightly. If you're a couple hundred feet away and already at 8000, look at your tire height first, compare that to the 60' times and make a decision there. If the 60's could handle a taller tire and you have the power to 'pull it', then go to the taller tire. If you're stock and don't have the power to pull a taller tire and it would adversely affect your mph on the topend, then raise your rpm limit and run it out. Going to a taller final drive like 4.11 will give you more room at the top, but could adversely affect the 60' times. The benefit to the 4.11 over a taller tire would be the rotating weight of the tire. Short tires, short gears give great 60's and maybe 1/8th mph/times, but at the expense of topend charge. They usually will run out of breath. The benefit using a 4.11 with our stock or hybrid gearing is more room up top, but that usually indicates that the car needed it to begin with, which would normally be a much larger turbo, therefore more power in the higher rpms. An individuals power and where it makes it comes into play when making final drive/tire height decisions. Each turbo/engine combination could be different. Not really one good or right answer. You could easily make the change and lose et/mph. Calculate your rpm range by reviewing your power band on the dyno. This should give you your shift points and massage the gearing/tire combinations that keep you in YOUR desired power band. Hope this helps.

nitz

iTrader: (3)

9sec9, thanks for all the great info. i dont have access to dyno, but may try using one of those accelerometers that log to look at my powerband. i ended up getting a stock used viii 5-speed, and will see what results i get with that first since it's big difference in ratios to what i have now.