5-series Straight-line Performance Discussion
02-28-2006, 02:33 PM
#31
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Hi All:
Shifting at optimal points obviously is a big deal when trying for maximum straight-line accereration. There
is a method of deciding on optimal shift points. Basically, using this method, one determines the shift points
that yield the smallest drops, or largest increases, in road torque. The attached calculations show a partial application of this method. The calculations imply that shifting at redline is optimal for a 545i Step (i.e., redline shifting is not always optimal for all cars or for even a single car across its gears). A complete analysis would imply the same thing since, as the shift point decreases in a 545i Step, larger and larger road torque decreases are experienced.
The analysis leaves me sort of puzzled. It shows that when:
Shifting from 1st to 2nd I should end up at 3,648 RPM (6,500 X 2.34 / 4.17 = 3,648);
Shifting from 2nd to 3rd I should end up at 4,222 RPM (6,500 X 1.52 / 2.34 = 4,222); and
Shifting from 3rd to 4th I should end up at 4,875 RPM (6,500 X 1.14 / 1.52 = 4,875).
Unfortuately, while my car appears to shift at redline or above, my Pro RR shows the RPM drops to be:
Shifting from 1st to 2nd--to about 4,481;
Shifting from 2nd to 3rd--to about; 4,651 and
Shifting from 3rd to 4th--to about 5,060.
These RPM values do not make sense unless my Step is actually shifting at an RPM greater than redline.
And, actually, my tach seems to imply that if often shifts at about 6,700 RPM--which might be good or bad.
In this regard, I have confirmed that my "analog" tach and hidden iDrive digital tach are in close agreement
(although not confirmed above 4k RPM or under acceleration). Regardless, if it does shift at 6,700, then the
following RPM drops are implied:
a) Shifting from 1st to 2nd I should end up at 3,760 RPM (6,700 X 2.34 / 4.17 = 3,760);
b) Shifting from 2nd to 3rd I should end up at 4,352 RPM (6,700 X 1.52 / 2.34 = 4,352); and
c) Shifting from 3rd to 4th I should end up at 5,025 RPM (6,700 X 1.14 / 1.52 = 5,025).
b) and c) are heartening because they come close to reconciling all the data--whether or shifting at 6,700
is or is not optimal. Howver, a) still is out of line.
I like to know what's gong on with my car. In this case, I am not sure. Does anyone have any thoughts?
Shifting at optimal points obviously is a big deal when trying for maximum straight-line accereration. There
is a method of deciding on optimal shift points. Basically, using this method, one determines the shift points
that yield the smallest drops, or largest increases, in road torque. The attached calculations show a partial application of this method. The calculations imply that shifting at redline is optimal for a 545i Step (i.e., redline shifting is not always optimal for all cars or for even a single car across its gears). A complete analysis would imply the same thing since, as the shift point decreases in a 545i Step, larger and larger road torque decreases are experienced.
The analysis leaves me sort of puzzled. It shows that when:
Shifting from 1st to 2nd I should end up at 3,648 RPM (6,500 X 2.34 / 4.17 = 3,648);
Shifting from 2nd to 3rd I should end up at 4,222 RPM (6,500 X 1.52 / 2.34 = 4,222); and
Shifting from 3rd to 4th I should end up at 4,875 RPM (6,500 X 1.14 / 1.52 = 4,875).
Unfortuately, while my car appears to shift at redline or above, my Pro RR shows the RPM drops to be:
Shifting from 1st to 2nd--to about 4,481;
Shifting from 2nd to 3rd--to about; 4,651 and
Shifting from 3rd to 4th--to about 5,060.
These RPM values do not make sense unless my Step is actually shifting at an RPM greater than redline.
And, actually, my tach seems to imply that if often shifts at about 6,700 RPM--which might be good or bad.
In this regard, I have confirmed that my "analog" tach and hidden iDrive digital tach are in close agreement
(although not confirmed above 4k RPM or under acceleration). Regardless, if it does shift at 6,700, then the
following RPM drops are implied:
a) Shifting from 1st to 2nd I should end up at 3,760 RPM (6,700 X 2.34 / 4.17 = 3,760);
b) Shifting from 2nd to 3rd I should end up at 4,352 RPM (6,700 X 1.52 / 2.34 = 4,352); and
c) Shifting from 3rd to 4th I should end up at 5,025 RPM (6,700 X 1.14 / 1.52 = 5,025).
b) and c) are heartening because they come close to reconciling all the data--whether or shifting at 6,700
is or is not optimal. Howver, a) still is out of line.
I like to know what's gong on with my car. In this case, I am not sure. Does anyone have any thoughts?
02-28-2006, 06:23 PM
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Man, I am gone for 3 days and a whole new thread and already 3 pages! I love it....
It looks like we are going to have good weather, although it might be alittle hot (85F), so I'll try some testing later this week....
I need some other manuals to get testing.....I can't do this alone
Cheers,
It looks like we are going to have good weather, although it might be alittle hot (85F), so I'll try some testing later this week....
I need some other manuals to get testing.....I can't do this alone
Cheers,
03-01-2006, 05:21 AM
#33
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Originally Posted by EBMCS03' post='247071' date='Feb 27 2006, 11:56 PM
Didnt you mention that you got better times w/out AA? If so what mode were you in?
03-01-2006, 08:52 AM
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Originally Posted by realtyman' post='246990' date='Feb 27 2006, 08:47 PM
Hey Znod.
I'll need a few more months before the weather cooperates.
Temps are still cold and it is impossible to hook up with the cold asphalt and all of the sand & salt on the roads (not to mention the skinnier and far less sticky snow tires).
The cool intake charge is nice but at the expense of a ton of wheel spin (why can't the V-8's get a limited slip
)
Altitude: around 350 ft.
Temp: So freakin' long ago I can't remember (although probably low to mid 70 degree).
Rollout: I'll have to find the G-timer, plug it in and see what I had.
I remember making some adjustment to something when I went from my chipped A6 2.7T to the 545i for roll resistance or something but I know that's not what you are talking about. Most likely it is the standard rollout that it comes programed with.
I'll need a few more months before the weather cooperates.
Temps are still cold and it is impossible to hook up with the cold asphalt and all of the sand & salt on the roads (not to mention the skinnier and far less sticky snow tires).
The cool intake charge is nice but at the expense of a ton of wheel spin (why can't the V-8's get a limited slip
)Altitude: around 350 ft.
Temp: So freakin' long ago I can't remember (although probably low to mid 70 degree).
Rollout: I'll have to find the G-timer, plug it in and see what I had.
I remember making some adjustment to something when I went from my chipped A6 2.7T to the 545i for roll resistance or something but I know that's not what you are talking about. Most likely it is the standard rollout that it comes programed with.
03-01-2006, 08:56 AM
#35
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Originally Posted by grogan545' post='247874' date='Mar 1 2006, 12:52 PM
I believe when the weather is more suitable I will get best times with controls off and using manual shifting.
03-01-2006, 09:07 AM
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Originally Posted by Znod' post='247509' date='Feb 28 2006, 06:33 PM
Hi All:
Shifting at optimal points obviously is a big deal when trying for maximum straight-line accereration. There
is a method of deciding on optimal shift points. Basically, using this method, one determines the shift points
that yield the smallest drops in road torque. The attached calculations show a partial application of this
method. The calculations imply that shifting at redline is optimal for a 545i Step (i.e., redline shifting is not
always optimal for all cars or for even a single car across its gears). A complete analyis would imply the
same thing since, as the shift point decreases in a 545i Step, larger and larger road torque decreases are
experienced.
The analysis leaves me sort of puzzled. It shows that when:
Shifting from 1st to 2nd I should end up at 3,648 RPM (6,500 X 2.34 / 4.17 = 3,648);
Shifting from 2nd to 3rd I should end up at 4,222 RPM (6,500 X 1.52 / 2.34 = 4,222); and
Shifting from 3rd to 4th I should end up at 4,875 RPM (6,500 X 1.14 / 1.52 = 4,875).
Unfortuately, while my car appears to shift at redline or above, my Pro RR shows the RPM drops to be:
Shifting from 1st to 2nd--to about 4,481;
Shifting from 2nd to 3rd--to about; 4,651 and
Shifting from 3rd to 4th--to about 5,060.
These RPM values do not make sense unless my Step is actually shifting at an RPM greater than redline.
And, actually, my tach seems to imply that if often shifts at about 6,700 RPM--which might be good or bad.
In this regard, I have confirmed that my "analog" tach and hidden iDrive digital tach are in close agreement
(although not confirmed above 4k RPM or under acceleration). Regardless, if it does shift at 6,700, then the
following RPM drops are implied:
a) Shifting from 1st to 2nd I should end up at 3,760 RPM (6,700 X 2.34 / 4.17 = 3,760);
b) Shifting from 2nd to 3rd I should end up at 4,352 RPM (6,700 X 1.52 / 2.34 = 4,352); and
c) Shifting from 3rd to 4th I should end up at 5,025 RPM (6,700 X 1.14 / 1.52 = 5,025).
b) and c) are heartening because they come close to reconciling all the data--whether or shifting at 6,700
is or is not optimal. Howver, a) still is out of line.
I like to know what's gong on with my car. In this case, I am not sure. Does anyone have any thoughts?
Shifting at optimal points obviously is a big deal when trying for maximum straight-line accereration. There
is a method of deciding on optimal shift points. Basically, using this method, one determines the shift points
that yield the smallest drops in road torque. The attached calculations show a partial application of this
method. The calculations imply that shifting at redline is optimal for a 545i Step (i.e., redline shifting is not
always optimal for all cars or for even a single car across its gears). A complete analyis would imply the
same thing since, as the shift point decreases in a 545i Step, larger and larger road torque decreases are
experienced.
The analysis leaves me sort of puzzled. It shows that when:
Shifting from 1st to 2nd I should end up at 3,648 RPM (6,500 X 2.34 / 4.17 = 3,648);
Shifting from 2nd to 3rd I should end up at 4,222 RPM (6,500 X 1.52 / 2.34 = 4,222); and
Shifting from 3rd to 4th I should end up at 4,875 RPM (6,500 X 1.14 / 1.52 = 4,875).
Unfortuately, while my car appears to shift at redline or above, my Pro RR shows the RPM drops to be:
Shifting from 1st to 2nd--to about 4,481;
Shifting from 2nd to 3rd--to about; 4,651 and
Shifting from 3rd to 4th--to about 5,060.
These RPM values do not make sense unless my Step is actually shifting at an RPM greater than redline.
And, actually, my tach seems to imply that if often shifts at about 6,700 RPM--which might be good or bad.
In this regard, I have confirmed that my "analog" tach and hidden iDrive digital tach are in close agreement
(although not confirmed above 4k RPM or under acceleration). Regardless, if it does shift at 6,700, then the
following RPM drops are implied:
a) Shifting from 1st to 2nd I should end up at 3,760 RPM (6,700 X 2.34 / 4.17 = 3,760);
b) Shifting from 2nd to 3rd I should end up at 4,352 RPM (6,700 X 1.52 / 2.34 = 4,352); and
c) Shifting from 3rd to 4th I should end up at 5,025 RPM (6,700 X 1.14 / 1.52 = 5,025).
b) and c) are heartening because they come close to reconciling all the data--whether or shifting at 6,700
is or is not optimal. Howver, a) still is out of line.
I like to know what's gong on with my car. In this case, I am not sure. Does anyone have any thoughts?
I have noticed the same thing in regard to rpm's after shifts(approx 4400 from 1 to 2).I can think of a couple of reasons for some of this diff but I am not sure it acounts for all of it.
1-The dampening effect in the analog tach needle doesn't allow it to drop to the real value before acceleration begins in the next gear.
2-There is slippage during the shift so as to not cause driveline shock.
I am not sure this would account for such a large discrepancy but they both definitley are factors.
I am sure you read my post to realtyman regarding cold weather performance.I just think I've fooled myself into thinking my new methods are better.
03-01-2006, 09:23 AM
#37
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Originally Posted by grogan545' post='247884' date='Mar 1 2006, 01:07 PM
1-The dampening effect in the analog tach needle doesn't allow it to drop to the real value before acceleration begins in the next gear.
2-There is slippage during the shift so as to not cause driveline shock.
I am not sure this would account for such a large discrepancy but they both definitley are factors.
I am sure you read my post to realtyman regarding cold weather performance.I just think I've fooled myself into thinking my new methods are better.
2-There is slippage during the shift so as to not cause driveline shock.
I am not sure this would account for such a large discrepancy but they both definitley are factors.
I am sure you read my post to realtyman regarding cold weather performance.I just think I've fooled myself into thinking my new methods are better.
As I recall, your car appears to shift at 6.5k and not above this value as mine does. What do you think about my actual Step shifting at about 6.7k idea? I know that's the approximate point the rev limiter kicks in. I need someone to ride with me and to look at the digital speedo at shift points.
03-01-2006, 09:27 AM
#38
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Originally Posted by grogan545' post='247884' date='Mar 1 2006, 01:07 PM
I am sure you read my post to realtyman regarding cold weather performance.I just think I've fooled myself into thinking my new methods are better.
03-01-2006, 09:43 AM
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Originally Posted by Znod' post='247896' date='Mar 1 2006, 01:23 PM
I am glad you are back. I think your possible explanations make some sense. I thought of the second one. Still, I am not quite sure why the explanations would apply primarily to first gear--althought that's where the biggest shocks could occur.
As I recall, your car appears to shift at 6.5k and not above this value as mine does. What do you think about my actual Step shifting at about 6.7k idea? I know that's the approximate point the rev limiter kicks in. I need someone to ride with me and to look at the digital speedo at shift points.
As I recall, your car appears to shift at 6.5k and not above this value as mine does. What do you think about my actual Step shifting at about 6.7k idea? I know that's the approximate point the rev limiter kicks in. I need someone to ride with me and to look at the digital speedo at shift points.
I never tried to observe the digital numbers during acceleration,but I have a feeling they may be hard to read even by a passenger.I don't think they are dampened and they are very small.I have never been a fan of digital readouts in a car.They look good but are difficult to read unlessed dampened to the point that they are not a good indicator during fast acceleration.
I am still of the opinion that 6700 rpm's are not necessary for optimum performance in the 545.But I am open minded and it is worth some test time to either prove or disprove.If you can't show measurable difference I think you are just putting unecessary strain on engine & valveline components.
03-01-2006, 12:33 PM
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Originally Posted by grogan545' post='247915' date='Mar 1 2006, 01:43 PM
I am still of the opinion that 6700 rpm's are not necessary for optimum performance in the 545.But I am open minded and it is worth some test time to either prove or disprove.If you can't show measurable difference I think you are just putting unecessary strain on engine & valveline components.
I acutally think that 6.7k may be suboptimal. But, regardless, one of my points is that I have no choice about shift points since I can't shift when I want manually--i.e., I am at the mercy of the Step when it comes to shifting. Please see the question I raised above about your car's manual-shifting ability.At any rate, I am wondering if my car really is shifting at 6.7K. If so, then this fact would tend to reconcile all my data, except for the RPM drop after the 1-2 shift. If I have time, then I will go back and extend the torque-drop analyis to 6.7k to cover the possibility that my car really is shiting at 6.7k.