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landshark92 landshark92 is offline
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Default Optimum Shift Points for the 6MT - 08-24-2019, 08:15 PM

I kind of love and hate the way my car drives. I love how it has such a hard midrange punch but I hate how it drops off so hard in the top end. I guess that is just the way the stock motor is and I've learned to live with it.

But with such a large drop off, that got me thinking that maybe I shouldn't run it out to redline like I enjoy doing, like I have done with all the other NA cars I have had in the past. So I got a few logs and converted them into dyno runs using Virtual Dyno. The graph in red is my car in kill mode, 19 psi peak tapering to 15 psi at redline. The graph in blue is a 14 psi flat boost curve all the way to redline. Here are the gear ratios for our N54 6MT:

335i E92 Coupe manual
1st 4.06
2nd 2.40
3rd 1.58
4th 1.19
5th 1.00
6th 0.87

For the shift rpm in 1st gear, I just took an educated guess of what rpm to shift at and multiplied that by 2.40/4.06 to get the rpm I would get in 2nd gear. I then compared the horsepower in 1st compared to the horsepower in 2nd. Then through trial and error, I found the shift rpm where the horsepower in 2nd gear would be equal to the horsepower in 1st or very close to it. This keeps me as close to peak horsepower as much as possible.

Then I repeated that for every gear until I found my final 5th gear shift rpm.

Disclaimer: This is all assuming that I have perfect traction. We all know that is not likely in first gear at least. So boost limiters by gear in 1st and 2nd gear and available traction play a very big part in when I would shift in the lower gears for the best acceleration.

The results:
In kill mode (red graph), with a big boost taper at redline, I should never redline the car and should short shift lower and lower in every subsequent gear.
Shift rpm: kill mode stock flash E35 map 5 19 psi peak 15 psi at redline 411whp on virtual dyno
1st 6,700 rpm
2nd 6,570
3rd 6,400
4th 6,100
5th 6,000


The flat boost curve (blue graph) is interesting. The car rewards me for holding onto gears a little bit longer. I actually should redline the car in 1st, 2nd and 3rd gear. You can see the slope of the torque curve dropping off at the higher rpms is not as severe in this run.
Shift rpm: E85 flash E35 14 psi flat boost curve 370whp on virtual dyno
1st 7,000 rpm
2nd 7,000
3rd 7,000
4th 6,450
5th 6,400


Well, it was bugging me that it felt like I was losing time redlining the car but I didn't know how much and what to do about it. Many people here know from experience and their timeslips that these cars don't like to be revved all the way out with stock hardware, even if it is fun to do so.

It is pretty clear that it's best to shift sooner and ride that fat torque curve for the best times. Let me know what you guys think. If anybody wants to do the same for their setup, post a log and lets take a look.
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2013 335is N54 / 6MT / JB4 G5 ISO "E85" BEF map 5 / Fuel: E40 / Phoenix Racing charge pipe / Diff lockdown / 70K miles

I'm addicted to meth but E85 gets me by...

Last edited by landshark92; 08-24-2019 at 11:54 PM..
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THE BEAST THE BEAST is offline
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Default 08-25-2019, 09:25 AM

Quote:
Originally Posted by landshark92
I kind of love and hate the way my car drives. I love how it has such a hard midrange punch but I hate how it drops off so hard in the top end. I guess that is just the way the stock motor is and I've learned to live with it.

But with such a large drop off, that got me thinking that maybe I shouldn't run it out to redline like I enjoy doing, like I have done with all the other NA cars I have had in the past. So I got a few logs and converted them into dyno runs using Virtual Dyno. The graph in red is my car in kill mode, 19 psi peak tapering to 15 psi at redline. The graph in blue is a 14 psi flat boost curve all the way to redline. Here are the gear ratios for our N54 6MT:

335i E92 Coupe manual
1st 4.06
2nd 2.40
3rd 1.58
4th 1.19
5th 1.00
6th 0.87

For the shift rpm in 1st gear, I just took an educated guess of what rpm to shift at and multiplied that by 2.40/4.06 to get the rpm I would get in 2nd gear. I then compared the horsepower in 1st compared to the horsepower in 2nd. Then through trial and error, I found the shift rpm where the horsepower in 2nd gear would be equal to the horsepower in 1st or very close to it. This keeps me as close to peak horsepower as much as possible.

Then I repeated that for every gear until I found my final 5th gear shift rpm.

Disclaimer: This is all assuming that I have perfect traction. We all know that is not likely in first gear at least. So boost limiters by gear in 1st and 2nd gear and available traction play a very big part in when I would shift in the lower gears for the best acceleration.

The results:
In kill mode (red graph), with a big boost taper at redline, I should never redline the car and should short shift lower and lower in every subsequent gear.
Shift rpm: kill mode stock flash E35 map 5 19 psi peak 15 psi at redline 411whp on virtual dyno
1st 6,700 rpm
2nd 6,570
3rd 6,400
4th 6,100
5th 6,000


The flat boost curve (blue graph) is interesting. The car rewards me for holding onto gears a little bit longer. I actually should redline the car in 1st, 2nd and 3rd gear. You can see the slope of the torque curve dropping off at the higher rpms is not as severe in this run.
Shift rpm: E85 flash E35 14 psi flat boost curve 370whp on virtual dyno
1st 7,000 rpm
2nd 7,000
3rd 7,000
4th 6,450
5th 6,400


Well, it was bugging me that it felt like I was losing time redlining the car but I didn't know how much and what to do about it. Many people here know from experience and their timeslips that these cars don't like to be revved all the way out with stock hardware, even if it is fun to do so.

It is pretty clear that it's best to shift sooner and ride that fat torque curve for the best times. Let me know what you guys think. If anybody wants to do the same for their setup, post a log and lets take a look.
I will admit, I skimmed through this , BUT you are saying with more power the earlier you shift ? Less power and rev out to 7k ???Something seems way off here.
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landshark92 landshark92 is offline
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Default 08-25-2019, 07:14 PM

Quote:
Originally Posted by THE BEAST
I will admit, I skimmed through this , BUT you are saying with more power the earlier you shift ? Less power and rev out to 7k ???Something seems way off here.
The actual hp figure, whether large or small, doesn't affect when I should shift. It is all about the SHAPE of the power curve.

The idea is to keep the engine spinning as close to the power peak as possible. Throughout the run, I want to produce the most average horsepower that my engine will give. I want to shift before the power drops off too much but not so soon that I'm out of the powerband in the next gear. I want my engine to spin at the rpm that straddles the power peak and not venture too far away from it.

If you look at the red dyno graph, the power peaks at 5,400 rpm. The blue dyno graph peaks at 5,800 rpm. For the red dyno graph, I want to shift a little sooner to keep it near that power peak. For the blue dyno graph, I want to shift a little later to keep the engine firmly centered around 5,800 rpm. I hope that clears it up.


2013 335is N54 / 6MT / JB4 G5 ISO "E85" BEF map 5 / Fuel: E40 / Phoenix Racing charge pipe / Diff lockdown / 70K miles

I'm addicted to meth but E85 gets me by...
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THE BEAST THE BEAST is offline
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Default 08-25-2019, 09:15 PM

Quote:
Originally Posted by landshark92
The actual hp figure, whether large or small, doesn't affect when I should shift. It is all about the SHAPE of the power curve.

The idea is to keep the engine spinning as close to the power peak as possible. Throughout the run, I want to produce the most average horsepower that my engine will give. I want to shift before the power drops off too much but not so soon that I'm out of the powerband in the next gear. I want my engine to spin at the rpm that straddles the power peak and not venture too far away from it.

If you look at the red dyno graph, the power peaks at 5,400 rpm. The blue dyno graph peaks at 5,800 rpm. For the red dyno graph, I want to shift a little sooner to keep it near that power peak. For the blue dyno graph, I want to shift a little later to keep the engine firmly centered around 5,800 rpm. I hope that clears it up.
I understand that, BUT even if power drops off earlier in the kill map, its still making more power than the other map. So you have more useable power overall and can and should rev the motor out a little more and on the blue map a little less. IMO
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THE BEAST THE BEAST is offline
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Default 08-25-2019, 09:39 PM

Also, I personally do not look at "peak" power, I prefer to look at it globally. Just because it "spikes" (peak), at a specific rpm, it means very little TO ME. As you said, I prefer to look at the actual power curve. Keep in mind there are factors. Transmission is a torque multiplier for one, also logs vary from run to run, and another is torque gets you off the line, after that horsepower comes into play.
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landshark92 landshark92 is offline
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Default 08-25-2019, 10:04 PM

Quote:
Originally Posted by THE BEAST
I understand that, BUT even if power drops off earlier in the kill map, its still making more power than the other map. So you have more useable power overall and can and should rev the motor out a little more and on the blue map a little less. IMO
Which map is better is not really the topic here. It is about maximizing the potential of a particular setup.

The flat boost curve blue map is just something I made for fun to see if I liked the more linear powerband. It is not as fast but the power builds up and does not drop off as quick, kind of like a naturally aspirated car if you like those characteristics. If I was racing, I would only use the red map.

Let me throw out some numbers to show you why I chose these shift rpms for the red map. Lets take 3rd gear for example. If I shift at at 6,400 rpm, the horsepower is at 367. In the next gear, 4th, the rpms will be 4,820 and the engine will produce 370 hp. The average is 369hp.

If I were to rev the engine out to 6800 rpm instead, the hp would be 304. In 4th at 5,100 rpm, the hp is 398. The average is 351hp.

Now I know that math is greatly oversimplified, but it does give some ballpark figures as to why shifting at 6,400 will give more horsepower over the run.

The ideal transmission with infinite ratios would keep the engine pinned at the power peak, right at 5,366 rpm for the entire run. We have to make do with only 6 ratios. Some of the BMW automatics have 8 speeds and Ford and Chevy are using 10 now. Those are some pretty busy transmissions but they definitely keep the engine in its sweet spot.


2013 335is N54 / 6MT / JB4 G5 ISO "E85" BEF map 5 / Fuel: E40 / Phoenix Racing charge pipe / Diff lockdown / 70K miles

I'm addicted to meth but E85 gets me by...
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landshark92 landshark92 is offline
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Default 08-25-2019, 10:09 PM

Quote:
Originally Posted by THE BEAST
Also, I personally do not look at "peak" power, I prefer to look at it globally. Just because it "spikes" (peak), at a specific rpm, it means very little TO ME. As you said, I prefer to look at the actual power curve. Keep in mind there are factors. Transmission is a torque multiplier for one, also logs vary from run to run, and another is torque gets you off the line, after that horsepower comes into play.
I totally agree. There is so much more that goes into getting a good E.T. This is only one thing to keep in mind. I haven't even taken into account turbo lag. I'm sure shifting a little bit later would help the turbos build boost a little faster in the next gear. Just looking at a static dyno chart, that is not the most obvious thing to think about, but might prove useful at a drag strip.


2013 335is N54 / 6MT / JB4 G5 ISO "E85" BEF map 5 / Fuel: E40 / Phoenix Racing charge pipe / Diff lockdown / 70K miles

I'm addicted to meth but E85 gets me by...
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THE BEAST THE BEAST is offline
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Default 08-25-2019, 10:26 PM

Quote:
Originally Posted by landshark92
I totally agree. There is so much more that goes into getting a good E.T. This is only one thing to keep in mind. I haven't even taken into account turbo lag. I'm sure shifting a little bit later would help the turbos build boost a little faster in the next gear. Just looking at a static dyno chart, that is not the most obvious thing to think about, but might prove useful at a drag strip.
I understand what you are saying, but as I said, many variables. Lets just take your flat curve log for now. I dont believe in redlining a stock turbo N54 PERIOD. I dont care what a log or virtual dyno shows. All the cars (n54 stock turbo) I have played with have had better E.T. shifting early (before redline). None have been on flat boost curve though either so that is also a factor. Best thing to do is take the car to a track or get dragy, then compare what works best for each given map. What I would do if I were you for the experiment you are playing around with would be.....get a log in 2nd, 3rd, and 4th all from 2k to redline. Virtual dyno it, gather data of power and torque, etc, then recalculate and see if it changes. Id be willing to bet your shift points will change.
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landshark92 landshark92 is offline
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Default 08-25-2019, 10:50 PM

Quote:
Originally Posted by THE BEAST
I understand what you are saying, but as I said, many variables. Lets just take your flat curve log for now. I dont believe in redlining a stock turbo N54 PERIOD. I dont care what a log or virtual dyno shows. All the cars (n54 stock turbo) I have played with have had better E.T. shifting early (before redline). None have been on flat boost curve though either so that is also a factor. Best thing to do is take the car to a track or get dragy, then compare what works best for each given map. What I would do if I were you for the experiment you are playing around with would be.....get a log in 2nd, 3rd, and 4th all from 2k to redline. Virtual dyno it, gather data of power and torque, etc, then recalculate and see if it changes. Id be willing to bet your shift points will change.
That is a really good point. My logs have all been the standard 3rd gear logs. Having different loads in different gears will surely affect the power curve to some degree.

The flat boost curve is a big kicker tho. Not many people run that setup so there isn't much to go on except maybe what I have put here. From actually driving it, it seems like revving it out within reason feels good.

But notice my kill map setup has me shifting early, way before redline. That map, with a large boost taper at redline, is along the lines of what most people run, myself included. And it aligns with what you have learned from experience. From the seat-of-the-pants, I also found that redlining it was slow. I just wanted some objective proof to see what was happening and see what I wanted to do about it.

What I find interesting is what are the guys with the big single turbos doing in terms of shift points? They have enough fuel and a big enough turbo to run lots of boost in the upper rev ranges.


2013 335is N54 / 6MT / JB4 G5 ISO "E85" BEF map 5 / Fuel: E40 / Phoenix Racing charge pipe / Diff lockdown / 70K miles

I'm addicted to meth but E85 gets me by...

Last edited by landshark92; 08-25-2019 at 11:18 PM..
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landshark92 landshark92 is offline
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Default 08-25-2019, 11:06 PM

Beast, I don't know if you have a JB4, but if you do, try running a flat boost curve map 6 at a lower psi like I did. It will take some time to get over the disappointment of losing the tire shredding midrange torque, but once you do, you may notice that the car pulls nicely toward redline. It is more linear than when my car was even stock, especially since my car had an overboost function that probably fattened the midrange up.

See if you can tell if the car likes to hold onto gears a bit longer and how much longer. I think you might be surprised.


2013 335is N54 / 6MT / JB4 G5 ISO "E85" BEF map 5 / Fuel: E40 / Phoenix Racing charge pipe / Diff lockdown / 70K miles

I'm addicted to meth but E85 gets me by...

Last edited by landshark92; 08-25-2019 at 11:11 PM..
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THE BEAST THE BEAST is offline
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Default 08-25-2019, 11:36 PM

I dont have stock turbos. My ACTUAL dyno shows a VERY smooth power curve, and I run a custom map 6, not flat boost curve. Running a flat boost curve to me is pointless. When I was stock turbos, I ran map 3, and then map 6. Always shifted before redline and at the track, proved to improve E.T. vs redlining as it didnt make enough power up top.
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