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Old 02-07-2012, 06:47 PM   #1
Pickler
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Default 4EAT more power in second gear?

noticed that there is better acceleration in second gear than first, why is this? And why does power almost die in third gear? i thought overdrive was fourth gear?

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Old 02-07-2012, 11:13 PM   #2
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Your I phone is not a calibrated power measuring tool
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Old 02-07-2012, 11:15 PM   #3
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Quote:
Originally Posted by RaceFaceXC View Post
Your I phone is not a calibrated power measuring tool
that was not my question.
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Old 02-08-2012, 12:36 AM   #4
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Quote:
Originally Posted by Pickler View Post
that was not my question.
Yet that is your answer.

Your iPhone is not the proper tool.

Rerun with a droid and come back.
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Old 02-08-2012, 12:41 AM   #5
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Yet that is your answer.

Your iPhone is not the proper tool.

Rerun with a droid and come back.
bahaha..hes right. look at a real dyno for real answers than ask real questions.

DROID
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Old 02-08-2012, 12:44 PM   #6
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There are two reasons. First and most important is that your iphone is not a calibrated torque measuring device. Out only senses accelerations... All of them. Secondly, you have a torque converter.

Your iphone may be useful to sense changes in performance if you can verify that it is consistent from run to run on the same stretch of road, on the same day with the same environmental conditions.
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Old 02-08-2012, 02:37 PM   #7
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I'd bet that you have more front to back lean in 1st and that's making it appear that you have better acceleration in 2nd.
another way of saying this:
read the first response.
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Old 02-09-2012, 10:12 PM   #8
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Your phone is only using a Gyro to show that graph. Its not really viable data.

However,

I have noticed on my MY09 Impreza OBS, 2nd gear seems to have the best acceleration from roll. IMHO, the 170hp engine doesnt have the guts to really power out the 3rd gear efficeintly to accelerate. Not to mention, AWD's tend to soak up more hp, so you really have 140~ish hp to the wheels, instead of the 170hp that subaru has posted.
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Old 02-10-2012, 12:05 AM   #9
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Well if it's only using the Gyro, that would certainly explain the useless data.

On my 98, first has best acceleration from a roll.

The engine's not going to have power to accelerate quickly if it's not in the good part of its power band. You may think second feels the best from a roll, but try from 20-25 in first, and around 75-80 in third.

Unless Subaru lowered friction in their drivetrain, 140 whp is still a tad high.
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Old 02-10-2012, 12:16 AM   #10
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Originally Posted by renyo View Post
Well if it's only using the Gyro, that would certainly explain the useless data.

The engine's not going to have power to accelerate quickly if it's not in the good part of its power band. You may think second feels the best from a roll, but try from 20-25 in first, and around 75-80 in third.

Unless Subaru lowered friction in their drivetrain, 140 whp is still a tad high.
I suspect so, because most iphone/android applications that do this type of measurement use the internal gyros to calculate whatever the application promises.

Actually, 2nd feels stronger from most XXmph from roll. however, I cannot argue the fact that 1st will feel stronger at the lower MPH, and 3rd will feel faster at higher speeds.

Oh, well i read 140whp somewhere was the output... correct me if im wrong though
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Old 02-10-2012, 09:35 AM   #11
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Quote:
Originally Posted by Pickler View Post
noticed that there is better acceleration in second gear than first, why is this? And why does power almost die in third gear? i thought overdrive was fourth gear?

Its a 4EAT in a 2.5i do we really need a thread about...........*sigh
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Old 02-10-2012, 09:45 AM   #12
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My 4EAT probably upshifts better than most humans do. It is also very predictable and responsive to throttle modulation. Don't be such a critical wonk.
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Old 02-10-2012, 10:40 AM   #13
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Quote:
Originally Posted by renyo View Post
Well if it's only using the Gyro, that would certainly explain the useless data.

On my 98, first has best acceleration from a roll.

The engine's not going to have power to accelerate quickly if it's not in the good part of its power band. You may think second feels the best from a roll, but try from 20-25 in first, and around 75-80 in third.

Unless Subaru lowered friction in their drivetrain, 140 whp is still a tad high.

The accuracy of The iphOne is pretty ok it's very similar in results to gtech which is use by car magazines.
http://www.youtube.com/watch?nomobile=1&v=0-DFbJQbeSY

Here is one from dynolicoous app, I did not launch just Wot after a roll, plz note second gear shows more power and 3rd gear power just dies:


122hp to the wheels seems accurate (without launch dynolicious reports 148 at crank). I do have a real dyno from a 2.5rs manual showing 125 to the wheels just have to find it and I'll post. In that dyno he achieved highest numbers in 3rd gear I believe not sure. A 4eat impreza on YouTube achieved best power in second gear as well in sportshift mode.

Oh here is the 4eat 2nd gear (please remember different dynos report different numbers):


I will post the rs dyno when I get home. Someone here mentioned the torque converter, but manual cars don't have TQ so why do they produce best numbers in higher gears than 1st?

Last edited by Pickler; 02-10-2012 at 10:57 AM.
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Old 02-10-2012, 11:59 AM   #14
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Quote:
Originally Posted by Pickler

I will post the rs dyno when I get home. Someone here mentioned the torque converter, but manual cars don't have TQ so why do they produce best numbers in higher gears than 1st?
They don't. The dyno just measures best in a taller gear.
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Old 02-10-2012, 01:45 PM   #15
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Quote:
Originally Posted by theoutbackdream View Post
Your phone is only using a Gyro to show that graph. Its not really viable data.

However,

I have noticed on my MY09 Impreza OBS, 2nd gear seems to have the best acceleration from roll. IMHO, the 170hp engine doesnt have the guts to really power out the 3rd gear efficeintly to accelerate. Not to mention, AWD's tend to soak up more hp, so you really have 140~ish hp to the wheels, instead of the 170hp that subaru has posted.
yes, obviously power to the wheels is lower than at the crank due to drivetrain loss:

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Old 02-10-2012, 10:41 PM   #16
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The point of the gyro comment was that it uses the accelerometers, and aside from possible error correction I can't think of how they would use the gyro for these purposes.

Second, for anyone who thinks it's a big deal that the any of these phones can produce accurate 0-60 / quarter / eighth mile times: It's a ~400 piece of electronics equipment. All it's doing is integrating, and running a stopwatch. I would hope to god it's capable of keeping accurate time...

Quote:
Originally Posted by Pickler View Post
Here is one from dynolicoous app, I did not launch just Wot after a roll, plz note second gear shows more power and 3rd gear power just dies:
The horsepower curve for first gear looks about as high as second. Also, according to that graph your acceleration is higher in first gear.

Technically the power should be the same in all gears. As for third gear, I find it hard to believe the phone is taking into account air resistance.

If you watch the youtube video and put in the numbers to any online 1/4 mile horsepower calculator, you come within 3 hp of what they got on the dyno. Does anyone want to say that those calculators are an accurate way of measuring horsepower?

Quote:
Originally Posted by Pickler View Post
I will post the rs dyno when I get home. Someone here mentioned the torque converter, but manual cars don't have TQ so why do they produce best numbers in higher gears than 1st?
Define best. You can make any gear have higher numbers depending on what you set the calibrations to.
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Old 02-10-2012, 11:59 PM   #17
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The point of the gyro comment was that it uses the accelerometers, and aside from possible error correction I can't think of how they would use the gyro for these purposes.
Well, Yes, I meant to say Accelerometers, but I forgot the word. Gyro just came up in my mind.

Essentially, I guess they use the accelerometer to measure any changes in any direction, due to the actions that happens appon it.. If you think about it, thats essentially how the Iphone is able to turn its screen to the side, and some iphone games use the Accelerometer to determine input.
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Old 02-11-2012, 12:23 AM   #18
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Originally Posted by theoutbackdream View Post
Well, Yes, I meant to say Accelerometers, but I forgot the word. Gyro just came up in my mind.

Essentially, I guess they use the accelerometer to measure any changes in any direction, due to the actions that happens appon it.. If you think about it, thats essentially how the Iphone is able to turn its screen to the side, and some iphone games use the Accelerometer to determine input.
Well, yeah, I mean I know how they work, just didn't see how they'd be useful for road dyno software. They probably do use the gyros for screen rotation now, but they used to (and devices without gyros) just use the accelerometers. Obviously you don't have as much resolution on each axis, but for the major 90 degree rotations they work just as well.
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Old 02-11-2012, 01:29 AM   #19
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Well, yeah, I mean I know how they work, just didn't see how they'd be useful for road dyno software. They probably do use the gyros for screen rotation now, but they used to (and devices without gyros) just use the accelerometers. Obviously you don't have as much resolution on each axis, but for the major 90 degree rotations they work just as well.
I agree with you. I guess the intention of these apps is try to show how great of a phone the iphone can be with a few apps.
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Old 02-11-2012, 09:14 AM   #20
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The answer to the OP's question is two-fold. The phone measures *acceleration*, not HP. It should be obvious to everyone who posts in an automotive forum that *acceleration* falls off in higher gears. There's less torque multiplication!

I would guess that the reason 1st gear shows lower numbers is that Subie is reducing stress on the driveline and/or that the phones accelerometer (not gyro!) is in a non-linear area.
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Old 02-11-2012, 09:26 AM   #21
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Maybe the answer to the OP is: Air resistance eats HP the faster you go. Sitting on a dyno in a shop you don't have 65+ MPH wind trying to slow you down...
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Old 02-11-2012, 10:14 AM   #22
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its not a big secret that a econobox automatic transmissioon has a tq converter designed to be easy to drive and smooth. under hard acceleration and especially in short gears like 1st, its probably never locks up completely. this would explain why power delivery to the wheels in 1st is less than 2nd.

I have to say that it is amusing to read all the "experts" analysis of the electronics and hardware of both the phones and the car. So much diarrhea being spewed.
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Old 02-11-2012, 02:40 PM   #23
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Originally Posted by RaceFaceXC View Post
I have to say that it is amusing to read all the "experts" analysis of the electronics and hardware of both the phones and the car. So much diarrhea being spewed.
Please then, share with the class.
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Old 02-11-2012, 02:50 PM   #24
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Please then, share with the class.
no. i am a ****ty teacher
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Old 02-12-2012, 10:08 AM   #25
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no. i am a ****ty teacher
Don't be so hard on yourself, it's becoming more common these days for teachers to not really understand what they're talking about.
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