i dont know if this thread ever posted?
06-02-06, 10:58 AM
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i dont know if this thread ever posted?
i need a power graph of when the rpms top out 1,2,3,4, and 5 so i know exactually when to shift
my car is an s-4 n/a 88 slight mods, exhaust, intake, high flow resonator, emmisions bs tookin off, ac removal and interior gutted.
sorry if i did not catch in the faq but i searched untill my eyes went numb and my shoulders caluapsed so if you have a nice plotted out graph showing hp in each gear i would much appreshiate it thanx
my car is an s-4 n/a 88 slight mods, exhaust, intake, high flow resonator, emmisions bs tookin off, ac removal and interior gutted.
sorry if i did not catch in the faq but i searched untill my eyes went numb and my shoulders caluapsed so if you have a nice plotted out graph showing hp in each gear i would much appreshiate it thanx
Last edited by stevenx788; 06-02-06 at 11:08 AM. Reason: missed something
06-02-06, 12:37 PM
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man
if i knew where ther was a dyno in my area i would take it but i just want to know ruffly, because i shifted at 8 grand and went to send gear and roasted the tires and my car hit zer0 to 80 in no time i was supprised i think my motor has been mildly ported because it handle high revs with out power loss. just wondering. it would make my day to dyno it but no clue where one is
i also bought the 7 of a kid that had the motor redone by maztech so it has ruffly 45000 miles on it runs strong too i dont know if it is a faster 7 or something because its the fastest n/a in my hood
i also bought the 7 of a kid that had the motor redone by maztech so it has ruffly 45000 miles on it runs strong too i dont know if it is a faster 7 or something because its the fastest n/a in my hood
Last edited by stevenx788; 06-02-06 at 12:40 PM.
06-02-06, 12:40 PM
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Drive up through your rpm range until you feel the power drop off. Shift just before that (depends on your reaction time). Are you talking for street driving, or on the track?
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06-02-06, 12:41 PM
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mostly street,
the only thing close to a track that i been on was the downtown st. petersburg florida grand prix, it was 2 days untill they raced and it was open for traffic so i did a few laps cool as hell let me tell ya!!!
the only thing close to a track that i been on was the downtown st. petersburg florida grand prix, it was 2 days untill they raced and it was open for traffic so i did a few laps cool as hell let me tell ya!!!
Last edited by stevenx788; 06-02-06 at 12:44 PM.
06-02-06, 12:47 PM
#11
Originally Posted by J-Rat
Once you start modding, the redline becomes somewhat superflouous. It is still a good rule of thumb, but take my car for instance, my optimum 1st gear shift is 7800. Well past the redline.
06-02-06, 01:07 PM
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Originally Posted by J-Rat
The butt dyno is pretty subjective, dont you think?
06-02-06, 01:34 PM
#19
Originally Posted by RXgirl7
I don't know about other cars, but in mine, it's pretty easy to tell where the usable power drops off. In my case, it's not so much about numbers, as about usable power.
06-02-06, 03:19 PM
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Originally Posted by My5ABaby
So... you ever think that the "usable power" drops off at a certain number? Just a thought.
06-02-06, 03:55 PM
#21
Originally Posted by RXgirl7
Yeah, it does, I just can't be looking at the tach, thats all. So, knowing that point with my butt is alot more helpful than knowing that it drops off at ~8300rpm. But there's nothing wrong with knowing numbers, or with being a numbers guy.
.
06-02-06, 04:34 PM
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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 .
.
06-02-06, 07:07 PM
#23
Your butt dyno is inaccurate, and I will tell you why.
Once you start feeling a marked decrease in horsepower, you have LONG SINCE past the peak torque range. The BEST and ONLY way to calculate optimum shift points is to go to a DYNO, pay the $50 or so bucks, and then plug that information into a program such as the one my tuner uses.
Effective shifting, is a matter of AVERAGE horsepower over a useable range, not just shifting LONG after power decreases, or as soon as you percieve power to be lost. Its the same concept with turbos. Big turbos give big numbers, but over how much of your useable RPM band?
Anyways, have fun with the butt dyno, but it is wholly inaccurate.
Once you start feeling a marked decrease in horsepower, you have LONG SINCE past the peak torque range. The BEST and ONLY way to calculate optimum shift points is to go to a DYNO, pay the $50 or so bucks, and then plug that information into a program such as the one my tuner uses.
Effective shifting, is a matter of AVERAGE horsepower over a useable range, not just shifting LONG after power decreases, or as soon as you percieve power to be lost. Its the same concept with turbos. Big turbos give big numbers, but over how much of your useable RPM band?
Anyways, have fun with the butt dyno, but it is wholly inaccurate.
06-02-06, 07:54 PM
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Originally Posted by stevenx788
i need a power graph of when the rpms top out 1,2,3,4, and 5 so i know exactually when to shift
A dyno is totally unsuitable for determining shift points. The only way to accurately determine the perfect shift points is to measure and graph the acceleration vs. speed in each gear. The perfect shift point is where the acceleration curve of one gear crosses the curve of the next gear up. But this is assuming that this occurs before redline, which is not always the case.
To measure acceleration cheaply you can use an accelerometer like this one:
http://us1.webpublications.com.au/st...1/2133_8mg.jpg
Or you can use an inclinometer like this one (using simple trig to convert angle to g's):
http://us1.webpublications.com.au/st...1/2133_6mg.jpg
Here's the reslts of acceleration testing on an Australian Mitsubishi Verada (218hp 3.5L V6 FWD):
http://us1.webpublications.com.au/st.../2133_11mg.jpg
You can see that on this car the optimum shift point for all gears is at redline.
If you want to spend more money, the Gtech Pro is a pretty cool performance measurement tool.
http://www.gtechpro.com/
Last edited by NZConvertible; 06-02-06 at 07:58 PM.
06-02-06, 08:07 PM
#25
Originally Posted by NZConvertible
A dyno is totally unsuitable for determining shift points. The only way to accurately determine the perfect shift points is to measure and graph the acceleration vs. speed in each gear. The perfect shift point is where the acceleration curve of one gear crosses the curve of the next gear up. But this is assuming that this occurs before redline, which is not always the case.
You want to set your shift points so that you are maximizing the power output. You need to have a graph of the engine's power curve and the gear ratios. Use the graph of the power curve to set the shift points so you are maximizing the area under the curve. If you want you can make a simple graph of the engine rpm vs. mph and then draw in the linear plots for each gear ratio. The equation is:
mph=[(0.01136)(rpm)(tire circumference in feet)]/[(gear ratio)(ring and pinion ratio)]
Or you can just use a stop watch and test different shift points and see which is fastest, assuming that everything else is held constant.
mph=[(0.01136)(rpm)(tire circumference in feet)]/[(gear ratio)(ring and pinion ratio)]
Or you can just use a stop watch and test different shift points and see which is fastest, assuming that everything else is held constant.
Example dyno graph with the shift points superimposed:
