Spark EV - An affordable electric racecar (my build thread)

[DarrenDonovan]

I would love to see and expect to see future EVs with gearboxes...that is to say at least perhaps 2 gears? These cars could really do with taller gearing at high speeds.

The Spark EV pulls like a freight train up until about 60. And it still does well after that given how quickly the torque curve drops off after that.

Imagine a flatter torque curve after 60 in this thing.

I've embarrassed some seriously quick cars on the roll and held my own up to top speed. But clearly their gearing and extra power dominates at freeway speeds.

I've wondered why that is. Please explain for me.

Thanks,

 

[Nashco]

That's great if you guys want to talk about multi speed EV gearboxes, but please start another thread for that somewhere else rather than in my build thread. One of the great things about the Spark EV in autocross is that I don't have limitations related to gear selection. Most autocrossers pick tire sizes to avoid shifting, as extra shifts per run means longer runs...I just plain don't have to worry about shifting with the single speed setup, which is a big perk.

Bryce

 

[nozferatu]

That's great if you guys want to talk about multi speed EV gearboxes, but please start another thread for that somewhere else rather than in my build thread. One of the great things about the Spark EV in autocross is that I don't have limitations related to gear selection. Most autocrossers pick tire sizes to avoid shifting, as extra shifts per run means longer runs...I just plain don't have to worry about shifting with the single speed setup, which is a big perk.

Bryce

Agreed. For you it's paramount you stay in the flat torque curve band at all times. The real killer of performance for this car is the traction control and completely crap tires.

 

[Chaconzies]

I created a new thread here http://www.mychevysparkev.com/forum/viewtopic.php?f=6&t=4084 to continue this discussion and cleaned up a few posts here that way we can Nashco's build thread on topic. Thanks!

 

[Nashco]

I'm long overdue for an update. My personal and professional life has been keeping me really busy and in my "free time" I've been more focused on working on my cars and actually competing than documentation. I decided to take some downtime over the holidays to finally catch up on documentation.

I competed in just about every event I could last year getting the car and driver dialed in. Most of my events were autocrossing with the Porsche club, and it sure does get people talking when you're mid-pack with an electric econobox!

The car mods haven't been static, but the biggest focus has been the loose nut behind the wheel. I've slowly figured out how to get my head on straight in the first few runs and figured out how to drive around the damn stability control. Yes, the stability control is driving me nuts! In the wet it's a huge help. In the dry, it's a nuisance...and I can't figure out how to disable it.

But...I digress. The mods. I'll split the modifications up into a few posts to keep things manageable.

- Suspension
- Tires and wheels
- Weight reduction
- Seats and belts (still in progress)

The driver schools/autocross classes I've been to have been really helpful, not just with seat time for my novice self but also dialing in the suspension. I eventually softened up the front suspension damping to deal with the very bumpy PIR parking lot, but the rear has been basically hopeless. The beam rear axle combined with an extremely conservative stability control system means that the very regular occurrence of a rear wheel lifting during braking results in delayed power delivery until well after the car is settled again. Until I can figure out how to fully disable the stability control, I think I've got it dialed in about as good as it is going to get.

Bryce

 

[Nashco]

Suspension

The very first modification I started on with the Spark EV when I got it was getting different suspension on it. From the factory, the Spark EV is a wallowing turd bucket with horrible feedback considering its size. This is partly due to the construction of the extremely efficient and quiet tires that suck otherwise, partly due to skinny tires for a car this size, and partly due to the spring and swaybar combos the car is equipped with. It's very clear that GM didn't intend for this car to be a hot hatch competitor, the powertrain just happens to enable it to be possible. So, the car needed lowered, stiffened up, and fitted with better rubber. I decided to lower first and fit tires second to take the safe path forward.

There are almost no aftermarket options for the Spark suspension in general, despite being produced in huge volumes for a global market. To make matters more difficult, the Spark EV has a slightly unique rear suspension compared to the gas car because of the additional battery weight in back. To make things even more difficult, the strut body in front doesn't have a large enough inner diameter to allow for something simple like a Koni insert. Rather than reinventing the wheel, I started with a coilover kit from Megan Racing that was intended for the gas Spark. It wasn't as easy as I had hoped, but I made it work out. I'll detail the work required in case any others are crazy enough to want to duplicate my efforts.

Start with the Megan Racing coilover kit for the (gas) Chevrolet Spark:

http://www.meganracing.com/product.asp?prodid=1565&catid=31
Model Number : MR-CDK-CSP13

The front strut assembly and front sway bar links are a direct bolt in, just follow normal procedures to install them like any other coilover assembly. You'll need a set of stock Spark strut top bearings. In my case, I got a pair of gas Spark strut assemblies to dissect and used those bearings so that I could keep my stock Spark EV strut assemblies intact.

The rear spring and damper setting is where things get more challenging. The root of this is the unique suspension on the Spark EV. There are three reasons the Megan Racing kit for the gas Spark doesn't work for the Spark EV:

1. The Spark EV rear springs are unique. In addition to the increased spring rate to deal with the extra weight of the battery, the upper and lower spring seats are different diameters (Spark EV spring has much smaller inner diameter at the perch).
2. The Spark EV rear upper damper attachment is completely different from the gas Spark. The chassis has a unique attachment that a pretty nice casting attaches to, and the damper goes into that casting. This ultimately means that the damper end in the Megan Racing kit interferes with the chassis without modifications.
3. The Spark EV rear lower damper attachment is just a little bit different. It uses an M14 bolt instead of an M10, which means the kit as provided won't bolt up. Because the damper is carrying some significant loads and the bolt is mounted in single shear, it didn't seem like a good idea to use a thread insert and an M10 bolt, so I ended up finding another part from Megan Racing's parts bin that works (from the Chevy Cobalt).

Here were my solutions to these issues. I won't say these are the absolute ideal solutions, but they worked for me.

1. I bought a pair of 325 lb/in, 8" long, 2.5" ID springs from Eibach. The rates and length were based on stock geometry, the amount of travel required, and the weight You can get springs with the same dimensions from lots of suppliers, I like Eibach. You can get these from lots of places, I like using Summit:

http://www.summitracing.com/parts/eib-08002500325/

The 2.5" spring can be used with the stock spring rubber in the upper spring seat, so you're halfway there. The lower spring seat is a bit more tricky. I just happened to have some adjustable spring perches laying around that worked perfectly with one modification. These came from a buddy's Ground Control kit for his Toyota AE86. This kit also had the exact same springs that are needed (325 lb/in, 8" long, 2.5" ID). I *think* that if you buy this kit, it comes with the same parts I used:

http://www.ground-control-store.com/products/description.php/II=96/CA=18

These threaded adjusters have a stepped ID, which allowed me to bolt them in place, ensuring that the spring and seat can't come out when the suspension is at maximum droop. I used a 1/2" bolt (4" long?) and a large washer that matched the larger inner diameter to bolt the spring seat in. The modification I made was to cut the spring seat down from 4" to 3" long so that the suspension had maximum upward travel. This is what it looks like in the end:

<insert picture of rear spring and adjuster…photo on the way>

2. This is the part you're really not going to like if you've been wanting to do this. The upper damper attachment interferes with the chassis. The first difficulty here is that the threaded portion on the damper isn't long enough for the Spark EV upper damper mount. I used a steel bushing to make up the difference, not too bad. The extra length causes another issue because it interferes with the chassis. Unfortunately, the only solution I could come up with was drilling a hole in the chassis to allow clearance for the damper. I did this by bolting the upper damper mount into the chassis (without the damper) and using a marker to mark the underside of the chassis where the center of the mounting hole is. I removed the interior panels to make sure I wasn't going to drill into a wiring harness or similar. I then drilled a small hole where that center point was marked from the bottom. Finally, I used a step drill to increase the hole size to about 3/4" and deburred the hole. Lastly, I drilled a small hole in the interior panel so that I can reach the adjusters with an allen key (rather than the provided adjuster) without removing any parts from the car. Some photos should help here:

3. The rear lower damper attachment that comes with the gas Spark kit from Megan Racing won't work for the Spark EV. I made it work for a short while with a band-aid solution while waiting on better parts, but it was pretty sketchy and in a couple of months of use was looking pretty rough. Fortunately, there is a bolt-on part that works perfectly from Megan Racing. Unfortunately, it took a little while to get the parts and I never did get a part number to easily order more. What is needed is the rear lower damper attachments from this kit:

http://www.meganracing.com/new/product.asp?prodid=50&catid=31
Model Number : MR-CDK-CC06

This works out because the Cobalt used a similar style suspension with an M14 bolt, as used in the Spark EV, and the Megan Racing damper for the Cobalt kit is the same thread as the Spark kit, so it's a one-for-one swap. I paid $50 for the parts, which was very reasonable. This is the stock damper, Cobalt mount from Megan Racing, and modified Spark mount from Megan Racing (unmodified gas Spark bushing shown).

That's the somewhat long and slightly twisted tale of the modifications required to get fully adjustable coilovers on the Spark EV. This allows the car to be lowered as much as 3 inches if one was just wanting a slammed Spark. I run mine about 2" lower than stock to allow for adequate suspension travel with the stiffer springs. The stiffer springs make for a much easier to drive car at the limits and of course the lowered ride height brings the center of gravity down and makes for less body roll. Plus it looks cooler.

An important note is that the Megan Racing kit has tons of adjustments, not only the damper settings but the height for the thread strut and shock bodies. It took me quite a bit of test and tune to get my dampers dialed in for the spring rates. The heights of the threaded bodies and spring perches can be used to not only dial in the ride height, but also the damper stroke. If you screw this up, you can cause damage to the suspension components and possibly even cause a catastrophic failure of the components which could make for a really bad situation. I'll take measurements of my setup shortly to help others speed up the process, but the importance of making sure you've done this right can't be overstated. I've corner weighted the car to get it dialed in as well as I could, about 51.5% front, 48.5% rear weight bias and about 52% left and 48% right weight bias with me in the car.

Another note that might of interest for folks racing is how to get some camber in the front and rear. The front is pretty standard "camber bolts" (same between the Spark EV and gas Spark). I used Raybestos parts from Rock Auto which they no longer list, here are some others they currently list that look just like the Raybestos ones I got:

https://www.rockauto.com/catalog/raframecatalog.php?catalog=11&partnum=K9757

The rear is more tricky. There is a pretty simple four bolt interface between the beam axle and the hub. I had hoped that this interface would be common with some other GM stuff so I could use something like this:

http://www.eurosportacc.com/products/euro-sport-1-degree-rear-camber-shims-vw-mk1-mk2-mk3?variant=10571887553

Turns out that we're not so lucky. So, I used some aluminum plate I had laying around and made some myself. This is what I ended up with (right side shown):

This gives me about 2 degrees of rear camber, which allows the BFG Rival 205/50R15 tire on a 15x6.5" ET45 wheel to fit in the rear without any rubbing. It's extremely tight, but *just* fits. Without the camber shim, there is rubbing with that specific tire. Moog recently came out with these rear camber shims, which they claim will work on the Spark, but I haven't tried them to confirm or deny.

http://www.moog-suspension-parts.com/moog-k100105

I leave the front alignment with as much camber as I can get, a touch under 2 degrees, and zero toe. Any more camber than that and my tires would rub on the spring adjusters…fitment is that tight! I only install the rear camber shims when I'm racing; they only take about 15 minutes to remove and it helps reduce rear tire wear to keep it at zero camber during daily driving.

Bryce

 

[Nashco]

Wheels and tires

I knew right away that the stock wheels and tires were going to be a pain to improve on. The factory wheels are different width and offset from front to rear, and the factory tires are different sizes front to rear as well. There are probably a few reasons for this, but one of them is obviously because this narrow car really wasn't designed for tires this big. This car comes with 165/65R14 tires in most markets, so the 185/195 tires on the Spark EV are already pushing the limits. The factory took care of fender lips, so there really isn't any easy clearance to gain. I wanted a square setup so that I could rotate front and rear race tires around freely and have matching wheels all around, that was my base requirement as I started figuring out what could fit.

I measured and tested and measured and tested until I finally committed to some wheels. The class I had in mind (SCCA STF) allows up to 225 tires on a 7.5" wheel, but it became obvious that wasn't even feasible when I tried test fitting those sizes. Eventually, I bought some Desmond Regamaster Evo Bright 15x6.5 ET45 wheels (say that fast 3 times!) from a guy in Hong Kong. That was an adventure on a few fronts, but I'm really pleased with the wheels.

These things are LIGHT at only 8.5 pounds each. That's about 10 pounds of rotating, unsprung weight lost at each corner compared to the factory wheels! I tested the BFG Rival 205/50R15s and surprisingly, they actually fit! It's not all unicorns and rainbows in Spark EV land, unfortunately, as the wheels required some caliper "massaging" and some 5mm spacers up front to clear the wheels spokes. The Spark EV bolt pattern is the extremely common 4x100, but the hub center bore is just a touch larger than the typical Honda (56.5 mm vs. 56.1 mm). I bought some of the common 56.1 spacers and kissed the ID with a dremel to make the wheel spacers fit the hubs. I think that wheels with the same width and offset but with wheel spokes that have more curve to them would be a better fit, avoiding the caliper clearancing but still requiring the spacers.

In the first event with the tires and wheels in the front, I had some really minor rubbing and raised the front suspension 10mm, afterwards no rubbing. Considering how narrow the car is and how tight the wheel and tire fitment is from the factory, that's all the tire I can get away with. Last year I bought some 195/50R15 Hankook Ventus RS3 (Version 2) since they seemed to be the best 200+ treadwear tire that I could fit (required for STF). Since then there are some better performers in the 200+ category since I got the RS3 V2, I might trade some increased performance for some minor rubbing when I get my next set of tires and go back to a 205.

The improved wheels and tires really transform the car. With good tires and lighter wheels, the 0-60 times are drastically improved and the car is just all around better to drive, as you'd expect.

Bryce

 

[Nashco]

Weight reduction

The most drastic weight reduction I made was the wheels and tires, as mentioned. Cutting about 40 pounds of rotating, unsprung mass makes a huge difference, but there's lots of other pretty easy and less expensive stuff I've done as well.

I've got a super lightweight battery setup I use, it saves me about 30 pounds. It's the smallest lithium battery that Battery Tender makes (about 1 pound), and provided a good balance of cost, reputation for quality, and construction that would allow it to be a very quick bolt-in. It was $65 when I got it, but I guess the price has since gone up a bit since then.

http://www.amazon.com/Battery-Tender-BTL09A120C-Lithium-Phosphate/dp/B00F9LPIAC

I swap the stock battery with this tiny one for racing events only, to be clear. It doesn't have enough storage capacity to do normal jobs (days/weeks without driving), but it does the job. The battery is strapped to a small wood fixture that I made that bolts in with the stock battery hold down. I've used these post adapters so that the stock cables and ends fit the lightweight battery, further simplifying the big and little battery exchange:

http://www.amazon.com/Odyssey-SAE-Terminals/dp/B004QCBM28/

This results in an installation about as robust as the original setup and I can swap the battery at the track in about a minute. The whole assembly weighs a touch under 2 pounds.

A pretty obvious weight reduction that any racer will recognize but should be highlighted is ditching all the junk in the trunk, so to speak. The Spark EV comes with a styrofoam insert in the back which has an electric pump with goop (instead of a spare tire), the level 1 charger, and the tow hook, plus the cosmetic carpet cover and cargo net. I can't recall the exact weight now and can't find my notes, but I seem to recall it was over 20 pounds for all of that stuff in the back which is just dead weight and can be ditched according to the rules. I have it removed almost always, as I have AAA if I get a flat tire and it's the rare occasion when I want my level 1 charger around.

Another silly and small weight reduction I've done is pulling the "engine cover" plastic off under the hood. This is allowed in STF and sheds a little under 4 pounds of weight reduction. The main power electronics cover has some sort of interlock switch built into it, so the switch needs to be popped out of the cover and reinstalled, otherwise I presume the car will have a malfunction (I haven't tested, just seems obvious). Before and after pictures:

Another weight reduction that is extremely easy to do, but not legal for STF, is removing the rear seats. The first time I did it, it took me ages to figure out, but now that I know how it takes about 5 minutes. This is an easy way to shed another 50ish pounds, but more importantly it makes a lot more useable space in the back for those of us who don't need more than two seats and can use the utility of more space, and is how my car is set up for daily driver duty. I've also made an insert that provides a flat load floor, which is convenient for loading up big stuff and especially appreciated by my big dog, who needs all the space he can get and hated the lumpy floor pan. I'll make another post for the rear seat delete changes another time.

One of the few things left that I can do legally, but haven't yet completed, is a lighter seat configuration. SCCA requires the driver's and passenger's seat and seat mounting hardware to weigh at least 25 pounds, while the stock seat and hardware is about 20 pounds heavier than that. This means there's another 40 pounds of weight loss possible that I haven't gone after…but will soon. This is still work in progress, more on that later.

As the car sits currently, it's about 2850 pounds in race trim, but I think I can get it down to about 2800 pounds if I pull all the stops. That's not very impressive by econobox car weights, but it's fantastic by EV standards. The weight loss is very noticeable as well. If you've noticed how much slower the car is when you have a passenger riding along, then you have an idea how much that 100-200 pounds of weight loss makes!

Bryce

 

[mtbhead]

Awesome post - thank you! Looking forward to the back seat pics.

 

[NORTON]

Yeah, thanks for posting all this info!!!

Once my warranty is gone it's game on!

 

[refinerysmells]

On the race car diet thought, any idea where the fake noise maker is and how to disable/remove it to save power and weight? Maybe find & disconnect fuse to see if it throws check light.

 

[nikwax]

Save power and weight? Disable a safety device? Great idea

 

[NORTON]

Yes, "Save power and weight".
That silly noise may sucks it up at about 0.05 Amps @14vdc. (WAG)
That equates to at least 25 feet of range with a full charge.
But you have to drive less than 18 mph to get that effect.
The silly noise maker shuts off at 18 mph, I have read, but I don't know how to test this.....

 

[nikwax]

please calculate the additional range provided by the weight savings...I'll be that 25 feet could easily be extended by an inch or two.

 

[WattEV]

On the race car diet thought, any idea where the fake noise maker is and how to disable/remove it to save power and weight? Maybe find & disconnect fuse to see if it throws check light.

Just disconnect the noise maker control unit. Super easy to get to. It is on the floor behind the center console next to the accelerator pedal. Where the driver side and passenger side carpets meet behind the center console, you can separate the two pieces easily as they are attached with just Velcro. Pull the Velcro apart and you will see the only control unit which is for the noise maker...It's small. Disconnect the connector and that's it.

 

[SparkevBlogspot]

The improved wheels and tires really transform the car. With good tires and lighter wheels, the 0-60 times are drastically improved and the car is just all around better to drive, as you'd expect.

Here's a stupid question, if you're taking questions. Do you think it's possible to fit 14" wheels for 105/70R14 tires, at least for the fronts? Smaller diameter tires should improve acceleration if they're sticky enough to hold traction. Math shows that should get 0-60 in 6.77 sec vs 7.2 sec with stock 2015.

Is it better to have acceleration with smaller tires (assuming they hold traction under acceleration) or cornering traction with wider (larger diameter) tires?

 

[Nashco]

14" wheels should fit, but I don't think it would help. Our car has enough torque to overwhelm the available traction at low speeds, so tire selection should be largely focused on getting the stickiest tires you can fit. In autocross and hillclimb, cornering is so important that wider is almost always better.

Bryce

 

[refinerysmells]

please calculate the additional range provided by the weight savings...I'll be that 25 feet could easily be extended by an inch or two.

Yes you guys convinced me to add an extra noise maker and 5 more airbags now I can just stop in front of moving semi's I am invincible at nerdy proportions and only lose minimal range! On a real note, for hot rodding/racing or just extended range anything that unnecessarily takes power and ads weight is a waste. Check out this 1989 technology http://www.treehugger.com/cars/modified-honda-crx-hf-wins-fuel-economy-competition-with-118-mpg.html This car stock is said to have got 50mpg but look how modifying and even getting rid of a safety feature/mirror OMG helped its performance. Maybe we can talk more about (closed corse) mods and ideas to see more spark ev's race into the future.

 

[NORTON]

>... for hot rodding/racing or just extended range anything that unnecessarily takes power and ads weight is a waste.
>>... Maybe we can talk more about (closed [sic] corse) mods and ideas to see more spark ev's race into the future.

>Yes very minimal 'waste', of what, a few Wh's? 50 ft. of calculated range increase? Can't be measured...
Also, if the car has warranty, ( we have a big one !), you shouldn't be dikin with mods that can effect that warranty.

>> 'We' don't have to talk about it. 'You' can look up SCCA Autocross, or Solo 1, or whatever they call it now. Hope to see you there !! I'll be the one with the car that makes a silly space ship sound!

 

[refinerysmells]

Hey do you know if Rota Slipstreams have any difference in the spoke thickness or curve compared to the Desmond Regamaster Evo Brights you used that would affect fitment on the Spark EV ? And I see the Rotas in 15x6.5 with 40mm backspacing thats about .19 of an inch less, would this work out better for not using spacers in the front and work both front & rear? Im aware of the weight difference between the 2 wheels but would like to keep it simple, id be happy with the 195 tire all around if you think that would help.