i dont know if this thread ever posted?
#26
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Originally Posted by J-Rat
Not sure what the basis is for this statetement.
Dyno graphs are the only way to accurately plot your power curve.
That inclinometer I posted a pic of costs considerably less than a single dyno run too (~US$10) and can be used to test handling and braking too.
Last edited by NZConvertible; 06-02-06 at 08:48 PM.
#27
Lives on the Forum
Godamnit, go find the freakin' dyno yourself!
http://www.dynojet.com/dyno_centers/...tive/index.php
-Ted
http://www.dynojet.com/dyno_centers/...tive/index.php
-Ted
#28
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Originally Posted by NZConvertible
A dyno is totally unsuitable for determining shift points. T
This is the statement that I didnt understand. Its completely incorrect.
True, but you pick your optimum shift points to maximise acceleration, so directly measuring acceleration makes far more sense than guesstimating acceleration from power and torque. There's no aerodynamic drag on a dyno, and that has a hugely different effect in each gear.
#29
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Originally Posted by J-Rat
This is the statement that I didnt understand. Its completely incorrect.
So in essence you are saying that wind has a way of SHIFTING your torque peaks?
#30
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Originally Posted by NZConvertible
Instead of just saying I'm wrong, why don't you explain to me how you think a dyno can accurately determine optimum shift points. How can a dyno tell you exactly how fast the car will be accelerating at any speed in any gear?
There is only one torque peak and it's obviously no shifted but aaerodynamics. But we're talking about shift points, and you don't necessarily shift at peak power and you certainly don't shift at peak torque. Aerodynamics obviously has an effect on acceleration. That shouldn't need to be explained.
There is only one torque peak and it's obviously no shifted but aaerodynamics. But we're talking about shift points, and you don't necessarily shift at peak power and you certainly don't shift at peak torque. Aerodynamics obviously has an effect on acceleration. That shouldn't need to be explained.
you DONT shift at the torque peak, you shift at a point that gives you the most time in the fattest area of torque. That means overrunning your torque peak to a point. Its not a hard concept to grasp, even if wind, rain, and the alignment of the stars are NOT in your favor...
#31
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Originally Posted by My5ABaby
Go some place safe and keep doing runs while shifting at 8300, or whatever your optimum shift rpm is. You'll learn what it feels like with your "butt dyno", except now it will be accurate .
#32
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Originally Posted by J-Rat
I love how you try to turn these discussions around.
FACT: Dynos are a PERFECT tool for determining torque curves.
FACT: Torque = G force, which equals acceleration.
FACT: Torque curves determime optimal shift points.
you DONT shift at the torque peak, you shift at a point that gives you the most time in the fattest area of torque. That means overrunning your torque peak to a point. Its not a hard concept to grasp, even if wind, rain, and the alignment of the stars are NOT in your favor...
FACT: If you want maximum acceleration through the gears, a $10 inclinometer will give you a much more accurate determination of the ideal shift point in each gear than a $40 (or whatever) dyno run. Pity it's not as "cool" as a dyno sheet...
BTW, you didn't answer my question. Please explain to me exactly how you would use a dyno to accurately determine optimum shift points in each gear. I'm honestly curious to know how you'd go about it.
#33
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1st off...wind resistance at speed is a constant. When I say that I mean that 90 mph drag is the same regardless if you're in 3rd of 4th. It doesn't matter. The same applies to rolling resistance and mass.
The amount of G's you feel (how hard the car is pulling) is directly related to torque (not HP) and gear multiplication via the trans. You want to maximize the amount of torque applied to the rear diff and therefore how hard the car is pulling. You do this by figuring out which gear will apply maximum torque to the rear diff. You have to know your gear ratios for the two gears you're comparing and the (approximate) flywheel torque...which you can measure indirectly on a chassis dyno or directly on an engine dyno.
Here's a quick example
---------------3rd----4th
---------------1.391-1.000
3500 - 449-625----449
4000 - 478-665----478
4500 - 493-686----493
5000 - 482-670----482
5500 - 466-648----466
6000 - 439-611----439
6500 - 387-538----387
7000 - 343-477----343
7500 - 299-416----299
8000 - 255-355----255
6500 rpm shift from 3>4 would put you at 4680 in 4th. You make 491 crank lb ft there. 538 (see above) vs 491. 3rd gear gets the nod. You should stay in 3rd past 6500.
7000 rpm shift from 3>4 would put you at 5030 in 4th. You make 481 crank lb ft there. 477 vs 481. 4th gear is now superior. You should shift to 4th before 7000.
You can break it down further than 500 rpm increments to get your exact shift points but hopefully you get the picture now. The torque reading off a a dyno chart coupled with knowledge of your gear ratios can allow you to come up with your optimum shift points.
And BTW...that's how the new GTechs with the smart shift lights work. They measure how many current G's you're pulling (torque) and estimate how many G's you'll pull after the shift to decide when to light the shift light.
The amount of G's you feel (how hard the car is pulling) is directly related to torque (not HP) and gear multiplication via the trans. You want to maximize the amount of torque applied to the rear diff and therefore how hard the car is pulling. You do this by figuring out which gear will apply maximum torque to the rear diff. You have to know your gear ratios for the two gears you're comparing and the (approximate) flywheel torque...which you can measure indirectly on a chassis dyno or directly on an engine dyno.
Here's a quick example
---------------3rd----4th
---------------1.391-1.000
3500 - 449-625----449
4000 - 478-665----478
4500 - 493-686----493
5000 - 482-670----482
5500 - 466-648----466
6000 - 439-611----439
6500 - 387-538----387
7000 - 343-477----343
7500 - 299-416----299
8000 - 255-355----255
6500 rpm shift from 3>4 would put you at 4680 in 4th. You make 491 crank lb ft there. 538 (see above) vs 491. 3rd gear gets the nod. You should stay in 3rd past 6500.
7000 rpm shift from 3>4 would put you at 5030 in 4th. You make 481 crank lb ft there. 477 vs 481. 4th gear is now superior. You should shift to 4th before 7000.
You can break it down further than 500 rpm increments to get your exact shift points but hopefully you get the picture now. The torque reading off a a dyno chart coupled with knowledge of your gear ratios can allow you to come up with your optimum shift points.
And BTW...that's how the new GTechs with the smart shift lights work. They measure how many current G's you're pulling (torque) and estimate how many G's you'll pull after the shift to decide when to light the shift light.
Last edited by Trevor; 06-03-06 at 11:46 AM.
#34
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Originally Posted by Trevor
1st off...wind resistance at speed is a constant. When I say that I mean that 90 mph drag is the same regardless if you're in 3rd of 4th.
And BTW...that's how the new GTechs with the smart shift lights work. They measure how many current G's you're pulling (torque) and estimate how many G's you'll pull after the shift to decide when to light the shift light.
#38
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Originally Posted by Trevor
I just spoon fed you the how and why yet you refuse to listen.
Come back when you get a clue man.
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