[PikeRider]

Hello Everyone,

I have an interesting idea for my 2008 HHR SS. I've been browsing the forums for a few months now off and on, so I thought starting my own thread might be a good idea.

Overall I am very happy with my cars performance as far as handling and acceleration goes, but a little extra something couldn't hurt. Additionally, on the highway I average around 30mpg, but the little bit of city driving I do is starting to kill my mileage numbers. Currently, it has a 2.0L turbocharged 4 cylinder with 260hp and 260lb-ft of torque powering the front wheels. Quarter mile time is roughly 14.2 @ 102mph, with a crappy 60' time around 2.2 seconds. So like I said not too bad for a stock station wagon.

I started to think about what I could do to improve my acceleration while helping with my city mpg's. So, I looked at the back two wheels on my car and decided that they are just being plain lazy. All they do is hold up the back end while the front wheels do all the work!

What I would like to do is place a small bank of batteries in the back of the car and power the rear wheels with an electric motor. For the drag strip I would have the benefit of the all wheel drive launch and the power from the electric motor until I build enough boost in the gas engine. Additionally, when I get into town I can idle or even shut off the gas engine and drive around on electric power.

I have a few ideas on how to pull this idea off, but before I say anything I would like to see what you guys think so far. Thanks for your help in advance! This is a great and informative forum.

Andy,
From Southeast, MI

[PikeRider]

Hey everyone. So I've been thinking more about how to execute this idea.

Currently, the car has a beam axle suspension in the rear. I was thinking that replacing the rear suspension with a straight axle RWD setup. I would then mount the motor to the rigid body of the car and have a small drive shaft that powered the rear axle. I don't think I need a lot of batteries. I would like to travel 10-20 miles on battery power in the city.

Let me know what you think.

Andy,

[Bowser330]

First off, most of this group/forum doesn't really get too involved in hybrid setups they are more the pure EV type...

Secondly, its been discussed before and is possible. A similar setup is the EMIS that Netgain sells, of course EMIS is for a rwd car, but the concept is the same and it has been shown to work.

A few things to keep in mind...

The axle will be a fixed gear ratio, so you have to pick a ratio that will accommodate the maximum rpm the electric motor can take...for example, if you choose the AC50, it has a max safe rpm of say 6000rpm, you want to make sure that your max speed on the HHR doesn't exceed 6000rpm on the electric motor. What you will find is that the torque you expect wont be as much as you would like when you have to gear the motor for speed. Now, you can get away from this problem by (a) creating sometype of clutch that would release the motor from the shaft, it would be better if it was an automatically actuated clutch so less human error, or (b) attach the motor to transverse transmission and electrically control it to shift at a certain rpm/speed, the shift method would actually provide you more power through the speed range where as the clutch method could give you the rowdy AWD launch but would just be dead weight once disengaged.

Weight is key, you don't want to add more weight that the power you are gaining, every 100lbs needs an additional 10hp... you should look into the lithium polymer batteries that are commonly used in RC cars but that are also used in one of the fastest EVs around, John Metric's Fiero, his cells are 45C continuous 90C peak, so they can pack a punch in a small volume.

consider an unconventional method of AWD/Hybrid...check out the EVpropulsion.com's motorcycle wheel motors...http://www.ev-propulsion.com/motorcycle-hub-motors.html
30kw (40hp) peak. If you were to put one on each wheel that's +80hp, if you were to go with the dual motor/wheel, then that's +160hp
It would take some custom machining to a lightweight racing rim and would require you to bolt the torque bar to your car, but it would be one of the only removable hybrid setups on the road...unbolt the torque arm, unplug the wiring, and replace the rim...done. Note: I am not sure of the weight of the wheel motor, however if it is to be used on the drag strip or generally smooth roads, the additional unsprung weight will matter less.

[PikeRider]

Thanks for the reply Bowser330,

You've highlighted a lot of good points. I've thought about a few of them, but haven't quite come up with a solution to each one. I was originally thinking about using one wheel motor in each wheel, but I'm afraid the un-sprung weight is to big of an issue. I would like the car to still handle fairly well, so that means trying to centralized the mass of the electronic components.

Weight is a big factor. I was planning on cutting weight in other areas to offset the weight of the batteries and electronics. I don't plan on breaking even, but I'd like to only add about 50lbs if I can help it. I have enough carbon fiber and fiberglass in my garage to make a 16' speed boat! I plan on tackle the weight by shaving a few pounds here and there off of the rest of the car.

Maybe an identical trans-axle from another HHR mounted in the rear could do it. That might require some extensive cutting and some nifty linkage work to connect it to one shifter. But that would solve the axle ratio issue and I would also have IRS! So I might even improve the handling of the car.

I have to be honest. Watching the 24 Hours of Le Mans this weekend has inspired me to pursue this even more.

Overall I would like to end up with roughly 100hp at the rear wheels.

Andy,

[Bowser330]

Well maybe it would be a good idea to start somewhere, a lot of times you learn while doing and the project can always evolve and improve later on...

If you were to pick up a manual transaxle for an HHR with brace/mounts to retrofit to the rear-end you could attach the motor and get it running, you can remove the clutch so you only have the shifter to worry about. You can use just a few gears for the time being during your testing to keep it simple, if you find that you want to use more gears then you can invest in some custom work to mate the shift linkages together.

I am not sure what your budget is but keep in mind that it has been mentioned that you don't want to spin a DC motor too long without power running through it (say your batteries run out and you are driving around town with the DC motor spinning on your rear axle), on the other hand and AC or BLDC wont have any issue.

[PikeRider]

I'm liking the idea of the additional transmission, but i believe that would take some cutting of the floor. Sense this is my daily driver that might have to wait until I have it really planned out. I really like the idea of being able to place the rear transmission in neutral while driving down the highway so I don't have to spin the motor.

How many volts do you think are necessary to obtain the 100hp I'm looking for?

[PikeRider]

Originally Posted by PikeRider

I'm liking the idea of the additional transmission, but i believe that would take some cutting of the floor. Sense this is my daily driver that might have to wait until I have it really planned out. I really like the idea of being able to place the rear transmission in neutral while driving down the highway so I don't have to spin the motor.

How many volts do you think are necessary to obtain the 100hp I'm looking for?

Actually 100hp isn't what I should be concerned about. I should be more interested in the torque!

[Bowser330]

Check out the HPEVS they sell the AC-50, but there are new motors coming out, 144V versions the AC-51 and AC-75... I would contact them for release dates. The currently available AC-50 with controller retails for ~4500$ and produces ~110ftlbs of torque and ~73hp. Using a transmission, the AC-50 powers cars on its own. Additionally since its AC you can use it to regenerate energy to reduce brake wear.

The DC suggestion would be high revving 9" motor, impulse9 or kostov9 and a controller that can deliver 1000A. 1000A in a 9" motor would produce 200+ftlbs of torque instantly (0rpm) up to a certain rpm that is determined by the voltage you intend to run...example: the impulse9 will keep 1000A up to 5500rpm if you can supply it with 160V.

Impulse9 = 1700$
Zilla1KHV = 2700$ (300V limit)
Total = 4,400$

However the motor was not designed to withstand 1000A for too long so you want to keep the 1000A bursts to a few seconds, which is enough to, depending on gear, launch you off the line or pull like a train while moving, sort of like an electric nitrous setup...

If you were so inclined you could also put your gas motor into neutral or turn it off and while in neutral have the 9" drive the car, as long as you have a transmission to help with torque multiplication.

[PikeRider]

Originally Posted by Bowser330

If you were so inclined you could also put your gas motor into neutral or turn it off and while in neutral have the 9" drive the car, as long as you have a transmission to help with torque multiplication.

That's what I was thinking about when driving in the city. My highway mileage is just fine 30-34mpg when I'm cruising around 70mph on a nice smooth highway. This project will take a little bit of time. I've got a few more projects going and my first son arriving this September! So it will be a little bit to get this off the ground.

Thanks for your help,
Andy,