Built 6 speed turbo guys, quick question
04-22-2014, 07:40 AM
#1
Built 6 speed turbo guys, quick question What gear ratio would you go with in your trans?
Option 1
2.97
2.07
1.46
1.00
0.80 or 0.74
0.63 or 0.50
or
Option 2
2.97
1.78
1.30
1.00
0.80 or 0.74
0.63 or 0.50
Car will be 800+whp this year and 1000+ next year. I run a 28in DR at all times and have a 3.50 rear gear. I currently shift at 6000rpm to help keep the stocker alive, which seems to be working quite well.
This is NOT a track car, most races are done on mexican highways aka 40 and 60 rolls. That being said, it will see some track time this year.
My thoughts are option 2 with a .8 5th and .63 6th because then they are atleast usable under normal driving. This ratio also means i have more time in each gear which in the turbo world, is a good thing. 40 rolls will start at 3000rpm which is right before peak torque and brake boosting works well there. 60 rolls are slightly higher around 3300 rpm.
Option 1 just seems like i will be shifting all the time/too quickly BUT i spend all my time in 4th gear which is the money gear. 40 rolls here start around 3500rpm but im afraid ill blow the tires off once i start making more power since im so close to peak torque. 60 rolls start at 3700rpm.
Thoughts?
Gear calc. im using: http://www.f-body.org/gears/
Dyno sheet to get an idea of the curve im working with.
Option 1
2.97
2.07
1.46
1.00
0.80 or 0.74
0.63 or 0.50
or
Option 2
2.97
1.78
1.30
1.00
0.80 or 0.74
0.63 or 0.50
Car will be 800+whp this year and 1000+ next year. I run a 28in DR at all times and have a 3.50 rear gear. I currently shift at 6000rpm to help keep the stocker alive, which seems to be working quite well.
This is NOT a track car, most races are done on mexican highways aka 40 and 60 rolls. That being said, it will see some track time this year.
My thoughts are option 2 with a .8 5th and .63 6th because then they are atleast usable under normal driving. This ratio also means i have more time in each gear which in the turbo world, is a good thing. 40 rolls will start at 3000rpm which is right before peak torque and brake boosting works well there. 60 rolls are slightly higher around 3300 rpm.
Option 1 just seems like i will be shifting all the time/too quickly BUT i spend all my time in 4th gear which is the money gear. 40 rolls here start around 3500rpm but im afraid ill blow the tires off once i start making more power since im so close to peak torque. 60 rolls start at 3700rpm.
Thoughts?
Gear calc. im using: http://www.f-body.org/gears/
Dyno sheet to get an idea of the curve im working with.
04-22-2014, 09:07 AM
#3
Pretty sure im going to go with option 2. Its the standard C6Z set while the first option is the Z51 package. Being a turbo car that sees a lot of mexican highways, i just cant see the benefit of swapping to a more aggressive gear set. In an N/A or centri track car, i think it would be great though.
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04-22-2014, 09:58 PM
#8
On The Tree
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I enjoy seeing other M6 turbo cars. I'm getting so much **** from all the guys around here about staying with my man pedal over switching to a 4l80. LS3/T56/PT8847/9" combo in the works here.
04-23-2014, 07:13 AM
#10
You sir, are not in the same boat as you are not driving a boat. :-) if you can get the 2.66 first. That Z with just about any rear gear should not have a 2.97 first.
For the OP option 2 with a .50 6th. You will NEVER get to 6th on a Mexican highway even after the long drive from Ohio.......
Unless you are doing a Texas mile keep the 6th to an over drive. But that usually means 5th will be overdrive as well.
Someone needs to make a normal 5th OD 6th driven pair me thinks.
I know 28's are tall but 1600 at 75 doesn't sounds too bad at all unless you have a cam big enough to where you have zero power down low.
For the OP option 2 with a .50 6th. You will NEVER get to 6th on a Mexican highway even after the long drive from Ohio.......
Unless you are doing a Texas mile keep the 6th to an over drive. But that usually means 5th will be overdrive as well.
Someone needs to make a normal 5th OD 6th driven pair me thinks.
I know 28's are tall but 1600 at 75 doesn't sounds too bad at all unless you have a cam big enough to where you have zero power down low.
Last edited by Exidous; 04-23-2014 at 07:18 AM.
04-23-2014, 09:07 AM
#11
You sir, are not in the same boat as you are not driving a boat. :-) if you can get the 2.66 first. That Z with just about any rear gear should not have a 2.97 first.
For the OP option 2 with a .50 6th. You will NEVER get to 6th on a Mexican highway even after the long drive from Ohio.......
Unless you are doing a Texas mile keep the 6th to an over drive. But that usually means 5th will be overdrive as well.
Someone needs to make a normal 5th OD 6th driven pair me thinks.
I know 28's are tall but 1600 at 75 doesn't sounds too bad at all unless you have a cam big enough to where you have zero power down low.
For the OP option 2 with a .50 6th. You will NEVER get to 6th on a Mexican highway even after the long drive from Ohio.......
Unless you are doing a Texas mile keep the 6th to an over drive. But that usually means 5th will be overdrive as well.
Someone needs to make a normal 5th OD 6th driven pair me thinks.
I know 28's are tall but 1600 at 75 doesn't sounds too bad at all unless you have a cam big enough to where you have zero power down low.
I think .8 and .6 OD's will be perfect. For my setup atleast. I geared the car so that i never have to use 5th while racing. Once the motor is built, ill be turning close 7000rpm and that will put me over 160mph in 4th.
04-23-2014, 09:18 AM
#12
04-23-2014, 11:27 AM
#14
9 Second Club
Download this little calculator and decide for yourself what might work best, shift points, speeds etc.
http://gearboxman.co.uk/inforatios.html
I have the typical 2.66, 1.78, 1.3, 1, 0.74 and 0.5 gear set, and currently use 3.27 ear and around 25.5"-26" tyres
1-4 works great for drag use and will allow 150mph ( close to 7000rpm max )
5th is still reasonable, and will also let me pull 200mph, even the 4-5 shift drops me to a quite good rpm.
And 6th is just a nice overdrive cruising gear with 70mph around 1500rpm. I can still pull 40-50mph with ease in 6th when I want, approx 3750lbs weaight.
So I'd say with your 3.5 and 28" tyres our ratios overall would be comparable.
I have had 3.55 rear along with the same rear tyres etc, and whilst for daily use it probably does drive just a fraction nicer, it just leaves 4th and 5th gear lacking for any drag type use.
5th and 6th is really personal choice depending on what you are using the car for and what speeds you might need to achieve in each gear, and of course the rpm band available.
I just seen any of the shorter 5/6 combos as completely useless for me. No matter what I would do, 6th is still useless for any fast speeds, so it will always be a cruising gear.
5th at 0.74 can still be a top speed gear because I can see 200mph. A shorter 5th would be of no use to me at all because it wouldnt allow 200mph, and neither would 6th as it would drop you far too low rpm after shifting to make it usable.
If you opted for the shorter set, you could still alter it by dropping the rear gear to a lower ratio ( numerically lower ) afterwards if it ended up too short..
http://gearboxman.co.uk/inforatios.html
I have the typical 2.66, 1.78, 1.3, 1, 0.74 and 0.5 gear set, and currently use 3.27 ear and around 25.5"-26" tyres
1-4 works great for drag use and will allow 150mph ( close to 7000rpm max )
5th is still reasonable, and will also let me pull 200mph, even the 4-5 shift drops me to a quite good rpm.
And 6th is just a nice overdrive cruising gear with 70mph around 1500rpm. I can still pull 40-50mph with ease in 6th when I want, approx 3750lbs weaight.
So I'd say with your 3.5 and 28" tyres our ratios overall would be comparable.
I have had 3.55 rear along with the same rear tyres etc, and whilst for daily use it probably does drive just a fraction nicer, it just leaves 4th and 5th gear lacking for any drag type use.
5th and 6th is really personal choice depending on what you are using the car for and what speeds you might need to achieve in each gear, and of course the rpm band available.
I just seen any of the shorter 5/6 combos as completely useless for me. No matter what I would do, 6th is still useless for any fast speeds, so it will always be a cruising gear.
5th at 0.74 can still be a top speed gear because I can see 200mph. A shorter 5th would be of no use to me at all because it wouldnt allow 200mph, and neither would 6th as it would drop you far too low rpm after shifting to make it usable.
If you opted for the shorter set, you could still alter it by dropping the rear gear to a lower ratio ( numerically lower ) afterwards if it ended up too short..