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[DynoMutt]

I thought violating the DMCA required having to thwart some kind of password protection or encryption put in place by the vendor.

If it's open without any kind of protection, why would the DMCA have any bearing?

[steven_first]

if you can access the sevcon settings and change them without a password then 2 things:  1 you are not entering a passwords thus not doing anything that is shadie or wrong. 2 That is Sevcons software not Zero's so they can't claim DMCA on something that is not theirs.

With the MBB that may be a little less cut and dry as you do need to know or defeat passwords.  That being said, this is on something that you own and is no longer owned by the manufacture.  As long as you are not redistributing anything then you are not breaking any DMCA laws.

[BSDThw]

You need to be in pass word level 4 (of 5) to make critical changes in the Sevcon settings.

If you use the Sevcon SW it will automatical use the standart PW. If you use  CAN manually you need to know log in with the PW!

Also the MBB and BMS has PW levels.

[Lipo423]

Over the last few weeks I've been trying to eke out some extra performance improvements from my 2014 Zero SR for use on both the road and the track.

Having recently acquired the Sevcon software and CAN adapter to modify the Sevcon Gen 4 Size 6 motor controller, a multitude of options have opened up to tweak the bike's performance. While many Zero owners have trodden this path before me I thought I would post some of the changes to:
- give everyone some more insight into the out of the box torque settings of a Zero SR;
- highlight opportunities to improve performance; and
- compare notes with those who have made similar tweaks to improve on what is already a high performance naked bike

Torque curves:

The diagram at the end of the post shows the standard Zero SR 2014 torque curves as set on the Sevcon controller.

The key highlights are 100% torque from 0 rpm and a tapering of that torque beyond 2350rpm (default motor max is 6,000rpm). I asked some forum members about what would happen if I increased these settings and was told to watch out for two things - motor cutouts and to stay within the 6,000rpm limit. I was also told that field weakening limits motor performance as rpm increases and so I can't be like a kid playing with his Dad's graphic equaliser and put everything up to the max!

While I don't have a torque curve diagram for the actual Zero SR motor, I think the one for a Remy 250-90 (see bottom of past) is a good example of how a similar motor's torque would reduce as rpm's increase (presumably suffering the same field weakening as my SR). The gradual reduction for the Remy made me think that the Zero could handle a gradual reduction rather than the steep reduction set on the stock motor.

Looking at the two curves together it seemed to me that there was an opportunity to increase the SR's torque at higher rpm without reaching the motor's limits which would result in motor cutouts. After some trial and error on the road and recent testing on the track, I have been able to successfully increase torque by 30Nm @ 4680 rpm and by 45Nm @ 5320 rpm as shown in the updated torque curve at the bottom of this post.

In my trials I also tried to increase the mid-range torque @ 3,590 rpm but when I moved from 155Nm to 165Nm I got cutouts so left it at the 155Nm.

I think I've made some small but important performance improvements and the bike now accelerates much better at high rpm (which was particularly useful when I'd lowered the gearing in the successful search for wheelies and reduced the max speed to 135kph). I think there may be a few more Nm I could eke out in the higher rpm range and I'll try that in the coming weeks and update this thread accordingly.

On the opposite end of the spectrum, I've also learnt a lot about improving the stopping performance of my SR and you read more on that in my "powerful regen" post.

Keen to hear others success in tweaking their Zero's performance and any questions you may have around the changes I have made.

Evtricity. How is the bike going with the new torque settings?

[evtricity]

Very good.

I have been running these settings for many months. The bike accelerates from 0-100kph in 4.0 seconds with 80kg rider on 17/66 gearing that tops out at 184kph at 6,000rpm.

The motor can cut out momentarily under hard acceleration in the first minute or two of the first session of a track day when the battery and motor are cold. This never occurs later on the day so have left the settings as is. I could lower the torque a little to remove this cutout but may trade off some acceleration when the battery/motor is warmer. The cutout occurs just under 3,000 rpm usually and I'm guessing that is when the motor's torque limit starts to fall away from peak.

The increased torque settings and gearing do overheat the motor faster but it's worth it for the few minutes of better performance. I would love to use the new IPM motor and run higher rpm for more top speed or more likely in conjunction with lower gearing for better acceleration and the same top speed. The IPM will likely overheat as well just not as soon.

Sent from my LG-D855 using Tapatalk

[Erasmo]

Just a thought, but how about adapting a tire warmer to pre-heat your batteries and motor?

[evtricity]

Maybe! I just hold it a little less than full throttle when accelerating under 120kph (for the first 3-4 minutes of the first session) to avoid the problem. If I'm racing I do 3-4 90% throttle accelerations on the warm up lap and usually no problem pinning it on the start line and for the rest of the race.

Sent from my LG-D855 using Tapatalk

[mrwilsn]

This is great information, thanks for sharing evtricity! I'm sure just about everybody on this site is as curious and excited as I am to find out how much of this can be applied to the 2016 Zero lineup using the IPM motor.  I think there is going to be a lot of new learning that takes place when those things get into the hands of hot rodders!

In the spirit of spreading knowledge....

The key highlights are 100% torque from 0 rpm and a tapering of that torque beyond 2350rpm (default motor max is 6,000rpm). I asked some forum members about what would happen if I increased these settings and was told to watch out for two things - motor cutouts and to stay within the 6,000rpm limit. I was also told that field weakening limits motor performance as rpm increases and so I can't be like a kid playing with his Dad's graphic equaliser and put everything up to the max!

Back EMF is your enemy, not field weakening.  Field weakening is a technique that can be used to overcome back EMF.  The EMF created by the spinning magnets generates a voltage in the stator coils.  This voltage cancels out the voltage being applied by the controller.  This is referred to as back EMF because when you apply a voltage to the stator coils the current creates a magnetic field that spins the magnets/rotors and the spinning magnets then generate a magnetic field BACK which opposes the magnetic field created by the current in the stator coils.

Volts from controller - volts from back EMF = working voltage.

At low RPM the voltage from the controller is high and volts from back EMF is low so you have lots of working voltage.  As RPM increases the working voltage approaches zero.

Zero working voltage = zero torque

Basically, the harder you push the more it pushes back. But field weakening limits the amount it pushes back.

Field weakening basically allows you to keep positive working voltage at high RPM.  Field weakening can be applied to SPM motors but requires LOTS of current and you need to have a better cooling solution because of the amount of heat generated.

IPM motors are perfect candidates for field weakening and it can be done at the power levels required at lower RPM.  As a result IPM motors can hit much higher RPM without additional cooling required

2015 Zero SR Final drive ratio = 30/132 and should hit 101.9 mph at 6100 RPM (Zero claims 102 mph top speed)

2016 Zero SR Final drive ratio = 30/130 and should hit 101.8 mph at 6000 RPM (again a claimed top speed of 102 mph)

2015 SR uses an SPM and 2016 SR uses an IPM.  Based on the ratio of sustained speed to top speed used on previous Zero's, since the 2016 SR can sustain 95 mph it should be able to hit a top speed of 114 mph

2015 SR top speed/sustained speed = 102/85 = 1.2.

1.2 * 95 mph = 114 mph (113.7 mph at 6750 RPM using 30/130 gearing)

Yet the 2016 SR is limited to 102 mph which is only about 6000 RPM (101.8 mph) with the 2016 gearing. hmmm 

When you say "cutouts" what do you mean? Like you get when you hit temp limit?

[evtricity]

Thanks for the electrical motor 101!

The cutouts I mention are a momentary (just under one second) complete loss of motor power. It's the equivalent of chopping the throttle instantly.

[mrwilsn]

Thanks for the electrical motor 101!

The cutouts I mention are a momentary (just under one second) complete loss of motor power. It's the equivalent of chopping the throttle instantly.

Do you know if it is being caused by the controller cutting power to the motor or if the controller is applying voltage to the motor but the motor is providing output power?

Have you done tests on a dyno to see how much more torque is being produced at the wheel by making the torque setting changes?

Heat affects the strength of the magnets.  They get weaker when they are hotter.  They will return to full strength when they cool unless they have exceeded the temp were permanent demagnetization occurs.

Dyno tests might reveal that you are actually better off with the lower settings in the scenarios where you get cutouts at lower temps but not after heating up.  Or it might reveal that there are other areas on the curve where you can bump up the settings and only suffer cutouts while temps are low but gain torque once things heat up.  More data is needed to find out the objective answer.

[Lipo423]

Very good.

I have been running these settings for many months. The bike accelerates from 0-100kph in 4.0 seconds with 80kg rider on 17/66 gearing that tops out at 184kph at 6,000rpm.

The motor can cut out momentarily under hard acceleration in the first minute or two of the first session of a track day when the battery and motor are cold. This never occurs later on the day so have left the settings as is. I could lower the torque a little to remove this cutout but may trade off some acceleration when the battery/motor is warmer. The cutout occurs just under 3,000 rpm usually and I'm guessing that is when the motor's torque limit starts to fall away from peak.

The increased torque settings and gearing do overheat the motor faster but it's worth it for the few minutes of better performance. I would love to use the new IPM motor and run higher rpm for more top speed or more likely in conjunction with lower gearing for better acceleration and the same top speed. The IPM will likely overheat as well just not as soon.

Sent from my LG-D855 using Tapatalk

This is great news evtricity, great job!

I'm a bit confused on the cut-outs comment.
When you made the first modification -posted std. and modified torque graphs- there were no torque changes on the sub 3500 rpm range from my understanding, so there should not be cut-outs…have you made more changes?

[Cortezdtv]

Have you ever looked at the draw side? You might be hitting the cutbacks to protect the battery just a thought

[GambitDash]

The motor can cut out momentarily under hard acceleration in the first minute or two of the first session of a track day when the battery and motor are cold.

Sorry for the thread hijack, but can you tell me more about these cut outs? This sounds suspiciously like something I have experienced a couple of times in my stock 15SR - early in my commute during heavy acceleration the engine "stutters". It's only happened a few times, but it is worrying.


Sent from my SM-G920T using Tapatalk

[Lipo423]

My 2014SR does not cut-out, but it becomes a bit "weak" from 60mph-on specially when the motor is cold (I guess this may have something to do with the internal windings resistance, as when it becomes warmer it is not that bad...but not sure)

[evtricity]

I'm not certain on what is causing the motor cutouts. I actually had cutouts although very rarely with the stock settings before I modified the SR at all.

The cutouts are a brief loss of power. You could call it a stutter I suppose as the power comes back on pretty quickly. Not to be confused with the metallic noise/vibration of the SR under hard acceleration.

When I did change the settings with increased torque,  my testing was done on the road and the motor and battery were warm. Under that scenario I found settings that would not cutout when the bike was warm. It was later on, on the track when I pinned it on the first lap or two at the start of the day when motor / battery were cold that I got the cutouts.

I could get the bike dynoed to confirm different torque settings but I can only effectively do a cold motor / battery test once per day. In essence the cutout problem is difficult to replicate as it only occurs when motor /battery are cold with the current settings.

I have effectively set the torque settings to avoid cutouts when the motor is warm.

One thing that I also had forgotten about is that I now have a higher gear on the bike than stock. I'm not sure that was the case when I first tested the higher torque settings. That would effectively increase the duration of high loads on the motor and increase the likelihood of cutouts.

Thanks for all the questions. It's good to think harder about a problem to understand the cause and overcome it.