Login






BMW Garage  BMW Meets  Register  Search  Today's Posts  Mark Forums Read 

BMW 3Series (E90 E92) Forum
>
When to Shift DiscussionThe right RPM


09212010, 07:12 AM  #23 
Brigadier General
54
Rep 3,464
Posts 
1st gear is so short that it doesnt even matter that much. How are you even able to judge when to shift out of first in a fully bolted car? You actually have traction?

Appreciate
0

09212010, 06:56 PM  #24 
Modder Raider
291
Rep 8,632
Posts
Drives: M3
Join Date: Apr 2007
Location: Surf City, HB

Just to let you guys know, I'm going to a flat stretch of road today and I'm going to try the same test is previously with the Vbox to measure the Gs.
I'll try to do 1st gear pulls, 2nd gears pulls, and 3rd gear pulls...2 of each. I think that the most interesting gears are the higher ones but it's hard to hit 100+ MPH on streets around here.
__________________
e36 M3 Coupe, e36 325i Sedan
e90 335iSOLD Best 601309.15 SecondsWWW.MR5RACING.COM 
Appreciate
0

09222010, 09:56 AM  #26 
Modder Raider
291
Rep 8,632
Posts
Drives: M3
Join Date: Apr 2007
Location: Surf City, HB

Alright guys, here is what I got from my logs:
I did about 3 runs in each gear on the same stretch of road and looked at the logs. At redline in 1st gear I was pulling the follwing Gs at redline: .59 .59 .54 At the same speed of at redline, I went WOT in second gear and pulled the following: .60 .60 .57 The Gs before redline in 1st gear is higher than the Gs at redline, so if I were to shift before redline, I would be loosing acceleration. Let's look at the results from the redline area of 2nd. At redline in 2nd gear I a was pulling the follwing Gs at redline: .39 .39 .37 At the same speed of redline (2nd gear), I went WOT in third gear and pulled the following: .46 .42 .44 Notice that the acceleration in 3rd gear is greater than redline at 2nd, so I went down the curve and found the speed of where the acceleration on the end of 2nd gear matched the acceleration of the speed in the next gear. The speed which I should shift is approximately 67 MPH. 67 mph with my setup is approximately 6750 ish RPM.
__________________
e36 M3 Coupe, e36 325i Sedan
e90 335iSOLD Best 601309.15 SecondsWWW.MR5RACING.COM 
Appreciate
0

09222010, 10:23 AM  #28  
Modder Raider
291
Rep 8,632
Posts
Drives: M3
Join Date: Apr 2007
Location: Surf City, HB

Quote:
Insead of making statments of how wrong it is, prove otherwise and then I will look at your data. Unless YOU have data to prove otherwise, I'll just say that YOU are wrong.
__________________
e36 M3 Coupe, e36 325i Sedan
e90 335iSOLD Best 601309.15 SecondsWWW.MR5RACING.COM 

Appreciate
0

09222010, 10:42 AM  #29  
Brigadier General
88
Rep 4,729
Posts 
Quote:
Just step off, the data is good and empirical.
__________________


Appreciate
0

09222010, 10:44 AM  #30 
Brigadier General
54
Rep 3,464
Posts 
1. Shifting does not maintain the same gs at xxxx rpm as simply pulling through that range.
2. Same goes for boost. 3. You like your data.....that's nice. However making people believe its true is hurting the community. 
Appreciate
0

09222010, 11:11 AM  #31  
Brigadier General
88
Rep 4,729
Posts 
Quote:
God whats the point of being a mod if you can't ban asshats?
__________________


Appreciate
0

09222010, 11:14 AM  #32  
Modder Raider
291
Rep 8,632
Posts
Drives: M3
Join Date: Apr 2007
Location: Surf City, HB

Quote:
1. Once you shift, it takes time for the acceleration to build so the acceleration at the same speed in the next gear will be even less than the previous gear. 2. Again, boost will take time to go up to peak so the gs when shifting into the next gear will be less than pulling through the range. 3. Wrong. It's only hurting you. I don't care what you say, the Gs at the end of first will always be higher than at the same speed in second. I proved it. Again, prove me wrong with your data. You can't go with only comparing 1/4 mile times. Shifting times vary.
__________________
e36 M3 Coupe, e36 325i Sedan
e90 335iSOLD Best 601309.15 SecondsWWW.MR5RACING.COM 

Appreciate
0

09222010, 11:22 AM  #33 
Brigadier General
54
Rep 3,464
Posts 
Prooved you right? On what grounds. Log gs through a full pull while shifting. Post shift there will be a spike if your car doesn't bog due to the tune or clutch ect ect. Winding out the first two gears is common sense cause they are short. Its the later shifts that are more important.
For the other guys making asshat comments. If the point of this thread is not to. Find specefic shift points then what is the point? Read much? He's actually saying not to short shift. Nice effort. 
Appreciate
0

09222010, 11:51 AM  #34 
Modder Raider
291
Rep 8,632
Posts
Drives: M3
Join Date: Apr 2007
Location: Surf City, HB

Spikes will happen at any shift point.
I'd rather have a spike at a point where at a higher g than a lower g. If shifting early, the spike will happen and fall at a lower g than shifting later. EDIT Wait a second, Now you are saying that winding out the 2 gears is common sense? Man, you are all over the place.
__________________
e36 M3 Coupe, e36 325i Sedan
e90 335iSOLD Best 601309.15 SecondsWWW.MR5RACING.COM 
Appreciate
0

09222010, 01:04 PM  #35 
Brigadier General
54
Rep 3,464
Posts 
How am I all over the place. I never stated where to shift. I stated your synopsis theory was inaccurate and your g theory doesn't take all the variables into account.

Appreciate
0

09302010, 09:05 AM  #36 
Brigadier General
54
Rep 3,464
Posts 
Notice the power through the gears on a n54. This is a DJ dyno....same type you used that doesnt even load the car up properly
Your tq curve theory is prooved to be flawed. You other theories of using G's well I guess we cant discuss those untill you actually do a couple shifts going from 1st to 4th at different shift points. You need to actually SHIFT not match up speeds in different gears. Last edited by Clap135; 09302010 at 09:10 AM. 
Appreciate
0

09302010, 10:19 AM  #37 
Modder Raider
291
Rep 8,632
Posts
Drives: M3
Join Date: Apr 2007
Location: Surf City, HB

This doesn't prove I'm wrong.
This doesn't take into account the multiplication of each gear ratio and that dyno is trying to normalize the power. This is why we see the numbers we do instead of seeing 12,000+ ft lbs to the wheels. Sorry, try again.
__________________
e36 M3 Coupe, e36 325i Sedan
e90 335iSOLD Best 601309.15 SecondsWWW.MR5RACING.COM 
Appreciate
0

09302010, 11:35 AM  #38  
Brigadier General
54
Rep 3,464
Posts 
Quote:
Like stated by me and others. There are TWO ways to figure out the optimal shift point for your car. 1. Do a 1/4 on a mustang dyno and apply gear correction factors. You can't simply use a one gear pull as it is not accurate and will not remain constant through an entire run. 2. Do the same on the road while logging with a g meter. Log a couple different shift points and see what gets you the highest overall number. You need to actually log the shift. 

Appreciate
0

08152012, 05:41 AM  #39 
Private
1
Rep 88
Posts 
ok just a quick question, i found this topic and thought maybe somebody here can help answer my question since i really am confused.
i own a 2007 330D SE Coupe (245bhp) and i am wondering what is the most efficient gear changes i can do to save the most fuel consumption? i been sticking to low rpm and high gear changes but i still find my self doing really low MPG, please any advice is wellcome 
Appreciate
0

Bookmarks 
Thread Tools  Search this Thread 

