Performance Boost!?

[Nashco]

EV power is almost always claimed as "BATTERY POWER". That is the power the battery is delivering. You will lose at least 10% of that in even the most efficient vehicles before it comes out at the contact patch of the tire. The spark motor is probably in the low 90% efficiency range, the controller is probably mid 90%, you probably lost a couple percent in hi-power interconnects (even in the battery itself), and another 5% in mechanical drive-train losses. I would be shocked (pun intended :mrgreen: ) if the Spark EV was getting over 85% Total System Efficiency.

Zero Motorcycles, for whom I used to run R&D, have a very clean drive-train, single stage belt direct from motor to wheel and approach 90% total system efficiency.

Actually, that power curve shown above IS motor output power (labeled mechanical power, not electrical power). The battery output is what is on the instrument cluster, which I've never seen higher than 120 kW but regularly above 105 kW. I posted a link in another thread with lots more information from an SAE presentation that GM participated in.

http://mychevysparkev.com/forum/viewtopic.php?f=2&t=3640&start=10

This presentation shows that the traction system (motor, inverter, drive unit) are 93% efficient at best, and at maximum power obviously less. Giving credit where it's due, GM has made this system incredibly efficient, which is a large part of why the Spark EV has the best MPGe of any vehicle ever classified by the EPA!

Bryce

PS. I'm a big fan of many parts of the Zero bikes (ditto for Brammo). I don't dare test ride one for fear of coming home with it until after I sell my current bike.

 

[emotodude]

Actually, that power curve shown above IS motor output power (labeled mechanical power, not electrical power). The battery output is what is on the instrument cluster, which I've never seen higher than 120 kW but regularly above 105 kW. I posted a link in another thread with lots more information from an SAE presentation that GM participated in.

http://mychevysparkev.com/forum/viewtopic.php?f=2&t=3640&start=10

This presentation shows that the traction system (motor, inverter, drive unit) are 93% efficient at best, and at maximum power obviously less. Giving credit where it's due, GM has made this system incredibly efficient, which is a large part of why the Spark EV has the best MPGe of any vehicle ever classified by the EPA!

Bryce

PS. I'm a big fan of many parts of the Zero bikes (ditto for Brammo). I don't dare test ride one for fear of coming home with it until after I sell my current bike.

That's what I was saying. They are claiming 105kw "mechanical power" though they fail to state if that is at the motor shaft or what. So yeah, if they are getting 105kW at the motor shaft, or even better at the wheels, with 120kW input power that is 87.5% Total System Efficiency. Not too shabby. North of 90% is "the holy grail" for EV engineers. I have heard KERS systems in f1 cars are into the mid 90%'s now!

 

[Skullbearer]

On the topic of improving performance, tires are the biggest improvement on a traction limited vehicle such as the Spark EV... but after ~30mph you are already producing maximum power. Power is power, you can only reduce weight or increase power to improve acceleration above 30mph. If you could reflash the battery controller to allow more power you could probably get it, but the motor likely can't safely put out much more. For that matter, the battery probably only has a 15-20% margin before real damage would occur.

So bottom line, tires and weight a faster Spark make.

 

[nozferatu]

On the topic of improving performance, tires are the biggest improvement on a traction limited vehicle such as the Spark EV... but after ~30mph you are already producing maximum power. Power is power, you can only reduce weight or increase power to improve acceleration above 30mph. If you could reflash the battery controller to allow more power you could probably get it, but the motor likely can't safely put out much more. For that matter, the battery probably only has a 15-20% margin before real damage would occur.

So bottom line, tires and weight a faster Spark make.

Yea true. If this car was about 2500lbs, it'd be a rocket.

Also I was thinking, there really isn't a really good reason this car couldn't have been made RWD. If anything flattening out the battery pack and moving the motor to the rear would have been ideal. And where the motor is now, all that space under the hood could be for luggage, etc.

 

[Nashco]

If you could reflash the battery controller to allow more power you could probably get it, but the motor likely can't safely put out much more. For that matter, the battery probably only has a 15-20% margin before real damage would occur.

Sounds like a lot of "probably" and not a lot of actual data...every product with a warranty has a safety margin, nobody knows what those margins are or how to exceed them, at this point. Once they are exceeded, the next step is to figure out how to make those parts more robust and start over again! Hot rodding 101. Obviously, weight reduction and improved traction will make the vehicle quicker, but so will adding more power...just like any other car on the road.

Bryce

 

[Skullbearer]

If you could reflash the battery controller to allow more power you could probably get it, but the motor likely can't safely put out much more. For that matter, the battery probably only has a 15-20% margin before real damage would occur.

Sounds like a lot of "probably" and not a lot of actual data...every product with a warranty has a safety margin, nobody knows what those margins are or how to exceed them, at this point. Once they are exceeded, the next step is to figure out how to make those parts more robust and start over again! Hot rodding 101. Obviously, weight reduction and improved traction will make the vehicle quicker, but so will adding more power...just like any other car on the road.

Bryce

The core difference here is that high voltage, and EV equipment in general, is much more difficult to modify in a DIY sense, meaning GM doesn't have to account for people upping power. GM almost certainly runs everything at the most efficient point possible while maintaining driveability. The problem is that the battery pack is an off-the-shelf form factor pack from A123 (thus not being flattened etc), and A123 determines the maximum electric power from the pack that still maintains their warranty. The motor that GM made is almost certainly NOT running any significant safety factor, since motor control is much more precise than engine control, and still very efficient at max torque and power. To get more power from that you'll need to know more about their motor and motor control in general than the team of engineers that made it. Same thing with the battery.

The reason there is a lot of probably involved is because the battery BMS and motor controller are about as 'black box' as anything you'll ever find in a vehicle. Hacking and replacing them is not like an engine controller... engine control doesn't vary much, but fine tuned motor controls is very specific to the motor hardware. You can do about 98% as well with a self-tuning motor controller like a Sevcon or Rinehart, but it simply won't be as good as the GM controller unless GM just sucks at motor tuning, which I really doubt.

Believe me, me and my co-workers work with EV and PHEV powertrains every day. If we wanted to improve the powertrain performance of the Spark EV, we all agree we'd just replace the motor and battery entirely, UNLESS we find that the battery has more power available than the motor is using. I may or may not have a CAN spec for the battery at work to hook a reader up and verify, but I won't share it (covered by NDA). I could only share if the motor is the limiting factor and how much power the battery can put out, which means a motor swap may be an option. I could recommend a motor swap that would work, but you would need to get a transmission (at least a one speed Borg Warner or something) that can take the torque and power, and install a differential. The integration with the GM motor is too tight to put in any of the more powerful motors I know of, and there is no guarantee that more torque could even be run through the reduction and diff. Keep in mind that the motor is a very well known torque that has almost no pulses whatsoever, so the diff may be 'undersized' for the equivalent combustion engine torque (which may see significant pulses above average torque). It's just a whole different ball game with pure EV.

The best place to start on an EV is not to put in an AEM intake and a turbo, its to decrease vehicle weight and improve traction. Weight loss options you might not have thought of:

- AC-DC Charging Module (3.3kW OBC)
- DC-DC 350VDC to 12VDC unit
- Emergency Brake system

Would need to provide a stand in CAN unit to keep the vehicle happy, and it may still throw some faults if the DC-DC isn't there, but you can charge your 12V battery after track runs and wire up so the OBC can become an Off-Board Charger. Need to be dedicated to weight loss though!


On the rear wheel vs. front wheel question, front wheels can apply more regen torque (just like front brakes can apply more braking torque), so I'll bet GM chose it to get more range and MPGe on the EPA drivecycle. Rear wheel would have been better for performance, no doubt (plus EV torque is perfect for drifting!).

 

[Nashco]

Skullbearer...I'm very familiar with how high voltage power electronics and controls work in a modern OEM application. The point of my comment was to say these things are all technically possible, even if you think they might be difficult, and that you don't know the limitations of the system so you're hypothesizing based on assumptions but not real data. If you've got actual experience with this particular system, I'd love to discuss it and compare notes, whether it's on the phone, in person, or via the web.

There are many ways to trick the system into doing something different than what it was originally intended to do. I'm not going to argue the variety of cat skinning methods as it's irrelevant until I'm actually trying them and reporting out what works and what does not work.

I'd love to see people documenting what they have tried and if they had success or not in this thread to provide data rather than theory.

Bryce

 

[Oberon]

As long as we are speculating, in other applications A123 cells are known for their high power density, that is one of their good points. The others being safety and long life. The downside is lower energy density.

The Spark pack is made of 336 20Ah 3.3V A123 flat pouch cells arranged as 112s3p. That is, 60Ah at 369V. The A123 spec sheet for 20Ah flat pouches claims a 20C discharge rate which for the Spark pack would be 1200A. At 369V = 443kW. Even allowing for sag etc the pack should be capable of 400kW. I don't think the battery will be a limitation. Indeed, a

The motor is rated for 105kW. PM motors like this don't really have strict power limits, the only way to really damage one is to get is so hot that the insulating varnish burns, or the magnets lose their strength. The rating is basically a measure of the cooling capacity of the motor, ie how much power can you feed in without it continuing to get hotter. For short bursts I'd be surprised if you could not at least quadruple the rated power input.

Power output is a different thing. If you get the extra power by increasing the current (given a fixed pack voltage that is the option) you get increased I^2 losses, ie the motor is less efficient. For drag racing or autocrossing this can be ignored. As can the heating. There is also magnetic field saturation where increasing the current past a point does not increase torque, just heating. This is probably the real limit on the Spark motor. Since it is very efficient, it can't be operating too close to saturation, so there is some headroom.

The above may be part of the reason that the motor current is limited below 30ish mph in the spark in the sense that it is mainly to keep the motor efficiency high for heavy footed drivers by limiting I^2 losses at low speeds. There will also be a limit on the current capacity of the controller power drivers.

Speculating based on the above I expect the motor could handle 50% more current and still be reasonably efficient and with no risk of damage if it was done only for limited duration. IF the voltage could be increased then the only real limit is rpm and cooling.

It may also be possible to exceed the current ratings on the controller too if you can figure out how the limiting is done. On the cheap electric bike controllers its as simple as soldering the shunt used to sense current. The Spark may be more sophisticated ;-). Again, heat is the main limitation, and given that a transistor junction has less thermal inertia than a big copper winding, it's probably easier to damage the controller. Still, the Spark is designed to last years and hopefully not have a lot of them hanging around the dealer shop having the inverter replaced, so there is probably some head room here too.

Finally, according to "reputable internet sources" (I'll see if I can find the link) the differential in the Spark EV is the same as the one in the Sonic, a somewhat larger car. I'm tempted to believe this since the Spark is clearly a parts bin car as much as possible.

Tl;dr, I'd be surprised if 150 kW was not possible fairly safely if you can get at the programming. Depending on your definition of "safely".

 

[Skullbearer]

We have to be careful with speculation on the A123 cells, they don't publish all their options and have both 'energy' and 'power' cells. The cells that are commonly in this form factor pack are 'energy' cells and have a spec 10s peak discharge rate of only 10C, and a 30s of 5C.

Saturation will definitely be a hard limit on the motor, this is a cored PMAC, though having a true sinusoidal back emf means that it will be able to push a little closer to saturation without as extreme of losses (saturation will only occur for a brief period, in a trapezoidal back emf it occurs for roughly 25% of full load). Increasing voltage means exponentially increasing insulation breakdown, unless GM paid extra for higher rated insulation, but certainly possible to run higher voltage for a while. Could couple a Rinehart 480-750VDC inverter or a Sevcon Gen4 Size10 (beta stage Inverter) with a buck boost bi-directional DC-DC unit. Higher losses due to the DC-DC, but could nearly double the motor top speed, and have full torque out to twice the corner speed... seems like corner speed is around 15 mph in the Spark, so full accel up to ~30mph then. Running more current isn't just an issue with saturation though, copper loss increases with the square of current. Very efficient motors will still run pretty close to their shutdown temperature under maximum continuous load.

For example:
Motor A (based on real vehicle traction motor)
Rotor temp at max continuous load: 96C
Stator temp (liquid cooled): 74C
Shutdown temp for Rotor: 110C
Delamination temp for Rotor: 140C
Shutdown temp for Stator: 90C
Delamination temp for Stator: 140C
Efficiency: >96% (Motor and controller)

I've seen a BLDC motor with only a 20% increase over 'maximum peak current' go from its continuous heat plateau to delamination in under 30s. Safety margin is generally about 5-10% for 10s bursts, but we have no specs on the GM motor, so who knows. Someone can put a data logging clamp on one of the 3 phase cables and record the Amps rms under full throttle pulses at various speeds, we can see where it's hitting currently. My clamp meter doesn't have any sort of logging output or a remote display so I haven't done it.

 

[Oberon]

We have to be careful with speculation on the A123 cells, they don't publish all their options and have both 'energy' and 'power' cells. The cells that are commonly in this form factor pack are 'energy' cells and have a spec 10s peak discharge rate of only 10C, and a 30s of 5C.

Given that the 105kW / 369 volts is 285 A, with a 60 Ah pack that would be 4.75 C. I doubt that the 105kW is intended to be only a 30s rating, so it seems likely these are not the 5C cells.

 

[Skullbearer]

We have to be careful with speculation on the A123 cells, they don't publish all their options and have both 'energy' and 'power' cells. The cells that are commonly in this form factor pack are 'energy' cells and have a spec 10s peak discharge rate of only 10C, and a 30s of 5C.

Given that the 105kW / 369 volts is 285 A, with a 60 Ah pack that would be 4.75 C. I doubt that the 105kW is intended to be only a 30s rating, so it seems likely these are not the 5C cells.

I've seen my display show spikes of just over 130kW when I have full HVAC with defrost going, full throttle. It definitely ramps down the peak power allowed on a short countdown, but since I can't drive straight up a wall for a mile, I don't know if its a 10s ramp or longer, I hit top speed at around that time.

To my knowledge there is no A123 pouch cell that is more of an 'energy' cell than the 5C/10C units. HOWEVER when I was trying to use them for Formula Hybrid in college, the 5C/10C rating was what they provided on internal documents to distributors... their official 'recommended' usage was only 3C/6C, which more closely matches what we actually see on our Sparks.

130kW / 350V is ~372A, or 6.2C

The cells should definitely be fine for up to 10C in <10s bursts, but repeated bursts at that WILL heat the battery up quite a bit. My speculation is that GM didn't want to do that... even with hard regen stops and hard accelerations repeated, I can't get my battery hot enough in 70F ambient to get anything on the 'Battery Conditioning' usage in my Energy tab. Most definitely not being pushed, the battery is acting as a sealed unit for me (unless my Spark is not reporting correctly).


We could convert the rear wheels to be driven. I haven't put my Spark up on the lift yet, anyone have pictures of the available space in the rear, by the battery? Hub motors are always an option.

 

[buickanddeere]

Fastest and most efficient way to improve the 1/4 mile times . Is to reduce the 0-30Mph time. As the Spark EV will smoke the factory front tires. Improving traction with a sticky set of tires is the 1st order of business.
As for chassis reaction, FWD is AZZ backwards . The better the front wheels grip the more the chassis lifts weight off the front wheels and onto the back wheels.
I suppose a set of airbags to hoist the rear up before launching may reduce weight transfer.
The rear wheel motors is a interesting concept. Don't know where a set of those could be located.

 

[nozferatu]

It'd actually be nice to build a mass inventory of this car.

Clearly it would take someone who has and is willing to take the car apart in terms of modifications, alterations, etc. I'm not sure where the weight loss could be as I'm sure it's already pretty lean. But that would definitely improve mid-range acceleration but traction would still be the limiting factor out of the hole.

A better/firmer suspension would improve traction too. Better rebound is needed on our cars badly IMO.

 

[Anonymous]

Just reached the end of this thread... sadly.

No updates from anyone?

I was actually getting a little excited... because there was some real technical knowledge being displayed in the last couple of pages
(speaking from my own EE perspective)

Starting my preliminary shopping for my Spark EV... but being in the middle of the USA, it's most likely going to mean buying sight-unseen, and having it shipped.

Still trying to decide if I want the first year with 400 lb-ft torque with 3.17:1 final drive ratio, or the later model with 327 lb-ft and 3.87:1 final drive. The later model seems to give the advantage of possibly restoring the 400 lb-ft of motor torque, resulting in increased low-speed performance... but it also uses the LG Chem batteries... which aren't capable of the peak power that the A123 cells are. At least with the first year, I could (maybe/probably) buy the 3.87:1 gear set and swap that out... best of both worlds... if the controller code doesn't puke. (seems odd to talk about swapping differential gears in this EV like I used to talk about in my 1966 muscle car)

I was excited to see Chevy's 2013 SEMA Tech Performance version with 450 lb-ft of torque... so clearly there's enough headroom to do that... and still more.
https://www.autoblog.com/2013/11/06/chevy-spark-ev-tech-performance-sema-2013/

It'd sure be nice if those wheels were available for purchase... but apparently they were custom billet built.
It'd also be nice to talk to the engineers responsible for such mayhem! ;-)

BTW... was the HVDC "combo" charger connector a common option? Did it ever become standard in the last years?

 

[Anonymous]

Just reached the end of this thread... sadly.

No updates from anyone?

I was actually getting a little excited... because there was some real technical knowledge being displayed in the last couple of pages
(speaking from my own EE perspective)

Starting my preliminary shopping for my Spark EV... but being in the middle of the USA, it's most likely going to mean buying sight-unseen, and having it shipped.

Still trying to decide if I want the first year with 400 lb-ft torque with 3.17:1 final drive ratio, or the later model with 327 lb-ft and 3.87:1 final drive. The later model seems to give the advantage of possibly restoring the 400 lb-ft of motor torque, resulting in increased low-speed performance... but it also uses the LG Chem batteries... which aren't capable of the peak power that the A123 cells are. At least with the first year, I could (maybe/probably) buy the 3.87:1 gear set and swap that out... best of both worlds... if the controller code doesn't puke. (seems odd to talk about swapping differential gears in this EV like I used to talk about in my 1966 muscle car)

I was excited to see Chevy's 2013 SEMA Tech Performance version with 450 lb-ft of torque... so clearly there's enough headroom to do that... and still more.
https://www.autoblog.com/2013/11/06/chevy-spark-ev-tech-performance-sema-2013/

It'd sure be nice if those wheels were available for purchase... but apparently they were custom billet built.
It'd also be nice to talk to the engineers responsible for such mayhem! ;-)

BTW... was the HVDC "combo" charger connector a common option? Did it ever become standard in the last years?

I'm sure it's possible...though I don't think anyone on here has any experience with car tuning software. I don't either. There are open source variants of car tuning software (free) but I have never used them. Also the car was only sold in CA and OR so that kind of limits the availability to tuners out there as well.

 

[SVTWRC]

Hello everyone , I’m a 17 year automotive forum user and have a Youtube channel SVTWRC. Took delivery from Carvana for a 2016 LT1 Spark without fast charge. Video is on my page with some info on how Carvana works. I will be exploring all the options for upgrading the tires , suspension, exterior, interior and try to give some insight on performance versus range and efficiency in the most scientific way possible without having a wind tunnel and telemetry. There is a post on here about a performance stage 1 boost without any info how or where anyone else can duplicate it. The whole reason these forums exist is to help and share knowledge . I will be emailing and talking to Chevy about the possible tuning upgrades ,as it may be similar for the Volt and Bolt to utilize a performance package like the Tech Performance package. The upgrades would be a great addition to and boost the image of the EV car as one you can modify . With the Spark EV being made available to purchase on Carvana , there should be a revival of these threads as people take delivery and they are almost ALL SOLD OUT of Spark EV . At the start of January 2019 there are 42 Spark EV on Carvana and only 3 of them are not sold.

 

[NORTON]

SVTWRC ,
Welcome to this little forum!
And congrats on your purchase of a Spark EV! Very good call !!

Too bad you went with a Non-DCFC version. This limits the car to local duty.
You could theoretically take longer trips, (with patience, if need be), and only then where the DCFC network is present. But the CCS network is growing daily !!

That is awesome that your 1st car is an EV ! Enter the future, young man!

And as a young man your first thing is "More Power".
Only, as you know, it's not like upping the boost and adding a bigger intercooler to a turbo engine.
You have a permanent magnet 3 phase motor and its matching controller. Do you overdrive these devices 110% or 150% from what they are designed to handle?
Can you overdrive them at 200% for maybe 10 sec before you let the smoke out, or overheating the magnets?
If you can, and you get monster sticky tires up front and get this power to the road, are the little gears and bearings within the drive unit up to this?
Sorry to rain on this parade....

Did you see the thread where someone is trying to use a 10kW Tesla charging module to charge the Spark battery pack?
Only it sounds like they're putting the current into the pack without any regard for the existing Thermal Management System and Battery Management System. Study BMS and TMS. Some EV's on the market have a lame excuse for TMS.

That is a line of study that will have a pay off , if it can be made to work properly. I know I'd consider a buying kit!
However, you can't put 10kW into a J1772 designed for 3.3kW. All the connecting AC wires to and the DC wires from the On Board Charger are rated for 3.3kW.
I would think it would be easier to get this going from the CCS port,, which yours doesn't have,,,,

Enjoy driving the future NOW! :!:

I get a constant stream of jokes about my EV. I like to tell them how much I spend on energy (ZERO, 9 months a year) and how much time I spend on oil changes and other maintenance during my +60k miles (ZERO). I tell them how much I hate popping the hood to fill the windshield washer... :lol:
And then my zinger is, "Do you think your little kids are going be driving Gassers in the future?"

 

[JPL]

Subscribed!

Where did you got the body stickers?

I highly recommend to return that spark and get a 2014 instead. Or perhaps get the motor from a wreaked one?

If my numbers are right you could get:

1556 ft-lb with
the 2014 Spark EV stock
402 ft-lb motor
+
2015 or 2016 Spark EV stock
3.87 final gear reduction

2014 Spark EV stock
402 ft-lb motor
(545.0388Nm)
3.17 gear reduction
1274.34 ft-lb @wheels
(1719.177Nm)

It's 5500-rpm !
5500 rpm/3.18 = 1729 rpm at wheel

2015 & 2016 Spark EV stock
327 ft-lb motor
(443.3525Nm)
3.87 gear reduction
1266 ft-lb @wheels
(1716.466Nm)
185/55R15 = 23.7x7.3R15

2014 Spark EV mod
402 ft-lb motor
3.87 gear reduction
1555.74 ft-lb @wheels
(2098.806Nm)
5500 rpm / 3.87 = 1421 rpm at wheel

Now hypothetically:

Spark EV mod
400 ft-lb motor from 2014 Spark EV
3.87 gear reduction from a 2015 or 2016 Spark EV
1555.74 ft-lb @wheels
(2098.806Nm)
5500 rpm / 3.87 = 1421 rpm at wheel

 

[SVTWRC]

Thanks Norton and JPL , some confusion about my post I want to clear up. I’m 42 years old and have 17+years on automotive forums. Been racing auto cross , RallyX , and time trials . My current ICE cars are 04 Subaru STi modified for insane street use and light track use, 03 WRX wagon and my wife’s 2018 Wrangler JL . Generally maintain all my vehicles except engine swaps , no hoist for motors. The Spark is my super fun , no worries get in and go as my Subaru are treated like aircraft and usually pre and post drive looked after. Thing I LOVE about this Spark are the single speed drive unit and rediculous throttle response. Going to research all the data I can and put some Youtube videos out answering to the best of my ability things like charging and range. Also a full review of the Spark EV . JPL I got those side decals here https://goo.gl/images/n328bs . My hope of aftermarket tuning may become reality as the Chevy Bolt has some of the Sparks tech. If someone tunes a Bolt the Spark should not be hard to tweak. I’m thinking of making the sport button a more aggressive map, yes it will draw more from the high voltage but you can put it in normal mode when not needed. For the next few years the Spark I will not be looking into swapping the motors from a 2014 but that info seems legit about the 400ftlbs with the 2016 final drive at 3.8.

 

[NORTON]

..... My hope of aftermarket tuning may become reality as the Chevy Bolt has some of the Sparks tech. If someone tunes a Bolt the Spark should not be hard to tweak.
I’m thinking of making the sport button a more aggressive map, yes it will draw more from the high voltage but you can put it in normal mode when not needed. ...

Again, how much do you think the Drive Unit and the Power controller can be overdriven, and for how long?
It's just electronics, after all. I don't know if 'Tuning' applies to an EV....
And then, Traction Control is going to limit power, just as it does stock. Tire smoke is what you get if you can defeat TC.

Sport Mode does not 'draw more' power. Your foot is still in control of the power. That mode just changes the Go Pedal mapping curve.
Full Go Pedal = Max Power,,, regardless of what position that silly gimmicky switch is in.
Plus it goes back to normal mapping at a certain speed. Or is that just Stability Control that goes back to normal? I forget....