Sunday, January 29, 2012

Everything is out

Everything I need/want to remove from the car is finally out.  The last parts to go were the fuel lines and some pieces that I later determined were fuel pressure accumulators.  I can now say with complete confidence that I'm 98% sure I cannot spill any more gasoline on the floor of the garage. 

It's time to pick the next part of the project to work on.  Since most things are best done after the motor adapters to be made and I'm at the mercy and schedule of my gracious friends who are helping to make those, I will probably start doing some interior work at this point.  I have my eye on a few seats and some carpeting, and I'm going to try and reglue the rear seats since they're peeling up.  Once this is done, the wife will be a lot happier!

On a side note, this fuel system in this car is an engineering marvel.  Modern cars have a bunch of sensors to monitor data all over the car and a computer calculates the perfect amount of fuel to inject into each cylinder.  Back in the mid-seventies, they didn't have computers but they managed to figure out how to do this mechanically.  A look at the Haynes manual showed me the schematic and description of how they used a mass airflow sensor, warm up valve, idle bypass, and "wine glass" shaped throats to create a non-linear fuel/airflow ratio that compensates for when you accelerate, engine temperature, and any number of other factors.  It's amazing they figured out how to do this.  It also makes me appreciate the fact that I won't ever have to figure out how to get this car through emissions.

Wednesday, January 25, 2012

Removing the fuel tank and transaxle

The last major piece of the car that is taking up space and weight is the fuel tank.  Some of the batteries will eventually reside here so it's gotta go.  I pull out my Haynes manual for help on how to take it out.  Step 1: remove the transaxle...crap!  Unfortunately, the fuel tank is situated right above the transaxle and just below the floor of the trunk.  I considered cutting it out, but it's full of fuel vapors so that's not going to work either.  After contemplating this for 3-4 weeks I bite the bullet and go to work.

Being a rear mounted manual transmission, there is some linkage going from the shifter to the back of the car.  This all has to be disconnected and removed.  I was mostly worried about that, but it turned out to be the simplest part of the project.

The shaft of the transmission is connected to a midshaft that links the transmission and engine with a slip fit spline and a clamp.  The instructions tell you to loosen the clamp and it will slide off.  Unfortunately, the bolt on the clamp is keyed to the shaft so you actually have to completely remove the bolt.  Not realizing this, I parted the transmission from the rear bellhousing and the midshaft slipped through its bearings and moved with the transmission.  There is only about 1 inch of space to back up the transmission, and with this slippage there is no longer enough clearance to get the shafts disconnected from each other.  Long story short, after about 3 hours of just messing with the shaft connection, the transmission is out.

The fuel tank was a bit stubborn as well, but no where near as bad as the transmission was.  There are two straps that hold it in and are easy to take off.  You also have to disconnect the fuel sending unit wires that are accessible through a panel in the trunk floor.  I got all that disconnected, and the next step in the instructions is to just remove it, but it's a little stubborn.  It's kinds of wedged between this crossbar that the transaxle hangs off of and the trunk floor.  There's foam that kind of locks it into place and it wasn't clear how to slip it out.  Eventually I just pulled really hard on the back side and it just popped out.  Not that it matters to me, but it doesn't seem like anything was damaged in the process, so I assume that's how it's supposed to come out.  Now I can see how oddly shaped it really is.

Reconnecting the transmission was no simple task either.  I thought that I now had the mechanics all figured out it would go relatively smoothly, but it took just as long to hook up as it did to take off.  12 hours in 5 days of working on it plus a bonus bandaged hand and the fuel tank is out and transmission back and hooked up.  Hopefully it works correctly when the car is moving again.  An additional bonus to this job is the CV joins were likely contaminated with grime in the process, so I plan to disassemble the axle assemblies to clean and regrease them some other day.

Sunday, January 15, 2012

Work Completed to Date

Since I didn't start this blog until a month after I started working on it, here's a little catch-up on what I've been doing since I picked up the car.

Nov 29th: Bought the car and brought it home.  She's in pretty good shape for a 35 year old vehicle.  The exterior is in good condition with only a few dings.  The paint is decent except for a few chips.  The interior is where most of the problems are.  A set of new seats, new tires, and a little TLC and this will be a nice car.
 As you can see, it needs new seats.

Dec 10th: Find out a brake bleeder screw is broken.  I'll have to take the wheel cylinder out and disassemble it so I can do some careful cutting and heating to get it out.  More on that later.

Dec 17th: The car has moved under gas power for the last time. Started taking the engine out today.My 7 year old  helped me bleed the brakes and check the compression!
Dec 19th: Fixing Brakes Step 1 part 1: To remove axle nut, use special tool A-147. If you don't have that, make your own tool to keep the brake drum from spinning. If your homemade tool is not stiff enough, clamp anti-buclking board to it. Attach 4 foot breaker bar to the 36mm socket and remove. It is possible that the anti-buckling board may snap in two. If so, go to part 2...

Fixing Brakes Step 1 part 2: If your custom tool broke, weld more metal to it and try again. Note, the breaker bar may still not have enough leverage to take the nut off. Also note, your 1/2 inch drive ratchet may now be broken. Stay tuned for the completion of step 1.

Dec 23rd: A new WarP 9 motor arrived and is now waiting for a vacancy under the hood.
Dec 29th: Today is the day to remove the engine. We were surprised to find that 2 or 3 of the bellhousing bolts were loose! I guess that's why there are 6? Here we are pondering how to get the last bolt out that's invariably not easy to reach and quite tight. The best part about all this is I had a guy lined up to pick up the engine one day later so it didn't have to take up half my garage for a month!

Here's my nephew helping out with the engine removal.

320 lb of motor.  That's about the same weight as my future battery pack.  Amazingly, I had a guy lined up to pick it up the next day!  He'd paid me a deposit a week earlier.  Not having to store this thing in my garage for a month put a big smile on my face.  Thanks to my brother, Cameron, my friend, Nick, and my wife for helping me out here!

Dec 31st: Realized the front wheel bearings are loose so I'll add that to the "to do" list.
Jan 1st: Brake repair Step 1 part 3: Need more leverage? Buy a 25 inch breaker bar! Ok, got that and it was too flexible. Felt like it was going to snap and damage me and the car in the process. A week of penetrating oil, heat, banging, and bouncing on it any the nut is still stuck.
Step 1 part 4: My dad found a 24 inch pipe wrench hiding in the barn. After 17 days of messing with this it finally came off with the help of an 18 inch pipe extension! Now what was I doing that needed that nut off?
Oh yeah, I finally got the rear brakes apart so I can hopefully extract that bleeder screw.
Jan 2nd: Bleeder screw is out and a new one is in there. Hopefully the brakes will be in good order after bleeding them one last time.

Jan 7th: Readjusted and repacked the wheel bearings. Also, now BOTH of my ratchets are broken!

Jan 6th: I think I have the motor coupler all figured out. Now I just have to buy a block of steel and relearn how to use a lathe. The first of many trips to the metal store is on the horizon!

Jan 12th: You would never have imagined this possible, but I found a guy on craigslist who wanted to trade the exhaust for 35 feet of 2/0 power cable and a bag of terminals that he had lying around!  I've sold everything but the radiator and the fuel tank at this point.

Jan 14th: I've started working on the motor coupler.  This piece is interesting enough (to me) that I think I'll make an entire post to talk about it.  It's amazing the amount of thought that has to go into making this piece.  Stay tuned for more on this one.

Jan 15th: I finally started working on removing the fuel tank.  I avoided it until now because it requires removing the transaxle.  For those of you who are like me and didn't know what that is, if the transmission and differential are combined into one housing it's called a transaxle.  I had to stop working on removing the axles because they require a special 12 point torx bit.  Luckily my neighbor is going to bring me one from work tomorrow.

Basic Steps in the Conversion

So what do you have to do to convert a gas powered car to electric?  Here's a moderate summary.  I plan to have a detailed post on each of these sections as I get into them.

First, get rid of the engine and anything related.  On my car it was fairly simple, mostly because of it's age (no computer = less wires) and the fact that it's rear wheel drive (more space under the hood).  In addition to the engine you will remove the exhaust system, fuel tank, fuel lines, radiator, and anything else that's not serving a purpose.  On my car there were lots of heat shields for the exhaust since it runs very close to other parts of the vehicle that don't like to get hot. 

Ok, now your car is stripped down to just the essentials.  Since the motor is the only part that has to go in a specific place, it's the next logical step to mount your new motor.  You'll have to make, or pay someone to make a shaft or flywheel coupler and an adapter plate.  These are precision parts, so if you don't have the right tools or skills you will end up with lots of vibration (at best) or a broken motor and transmission (at worst).  You will have to fabricate some motor mounts as well.

Next step for me will be to make a bracket for the air conditioning compressor.  The compressor on this car is equipped with a V belt pulley, so it's a lot easier to find the right pulley for the motor and the right size belt.  The motor has a shaft on both ends of the motor for just such a purpose.  More on this later.

Now you'll reach the point when you feel like 90% of your time is spent gazing into the open space under the hood.  You need to plan out where every last part is going to go.  With careful planning you'll minimize any rework, though no matter how careful you are you'll reach the finish and think of quite a few ways it could have gone together more efficiently.  By now you should know exactly how many batteries you plan to use, what size and weight everything is, and how you need to distribute the weight.  My plan is to build up weight under the hood equal to what everything was before I took it out.  This will minimize issues with alignment, steering, and braking.  Make some cardboard mockups of everything and see how it all fits.  Once you have a firm plan in place it's time to start the major custom fabrication.  Lots of brackets, mounting plates, enclosures, etc.  Your welder and abrasive blade chop saw are your new friends.

With all the brackets made, it is time to mount all the hardware.  Controller, DC-DC converter, relays, contactors, pot box, fans, fuses, vacuum pump and reservoir, batteries, and of course, lots of wiring.

These are the basics, but there will probably be many other projects to do that will be vehicle specific.  My vehicle needs quite a few areas of non-conversion related attention like new seats, bleeding the brakes and replacing a broken bleeder screw, loose wheel bearings, broken sunroof hinges and latches, and a few cosmetic things.  I'll also have to redo wiring for the air conditioning and heating system that will no longer function the way they used to.  I also plan to add some custom instrumentation.  If the car had a computer, I'd have to trick it into thinking everything's running the way it used to, like compensating for missing sensors.

Why a Porsche 924?

I spent a lot of time figuring out what vehicle I wanted to use for the conversion.  I had three criterion to begin with: it had to be cool, it had to have a manual transmission, and it had to have 4 seats.  My original thought was to get a mid 90's Mustang convertible since I loved those when I was in high school.  A little research and some calculations led me to realize that the 3500 lb weight of that vehicle would not be very quick to accelerate.  This led to a new desire that it should be lightweight.  Most of the vehicles out there are close to this weight, so most vehicles will be a little sluggish unless you put a lot of money into the power system.

In addition to the hit you take on acceleration, it hurts you in power consumption.  If you do a lot of stop and go driving, this is by far the highest influence on your battery pack size since energy required to get the car moving is proportional to weight and you are constantly wasting this energy every time you hit the brakes.  A 2500 lb car will get approximately 40% more range than a 3500 lb car under identical stop and go driving conditions.  Another energy factor to consider is rolling resistance.  You know how it's harder to ride a bike with flat tires than really pressurized tires?  Increased weight has the same result in drag.

The next train of though revolves around a Datsun 510.  These cars were popular in the 70's a very fuel efficient, and later became popular in drag racing due to the space they held under the hood.  The fastest electric drag racers was made from one of these (look up White Zombie).  I found an ad for the 510's predecessor, the 411.  It's even ligher than the 510 at around 2400 lb, surprisingly easily seats 4 (just watch the old Mission Impossible episodes and nearly every one of them has one of these cars with 5 people packed into them) and has a cool retro look to it.  When I actually saw it in person I didn't fall in love and the search continued.

The next train of thought was a BMW 3 series convertible.  Very cool, 2900 lb, and easily seats 4.  After quite a bit of looking I never found the right one for the right price show up on craigslist.  Everyone wanted $3000 for one of these 20 year old cars.  I never saw an "ideal" non-running convertible in a few months of looking.

After some time I was turned on to the Porsche 924.  It has a very small back seat, which is okay since my girls are still very small, it weighs 2480 lb with an empty fuel tank, and it's definitely cool.  This is one of the lightest production vehicles out there that still has 4 seats.  Another benefit to this vehicle is it has a manual steering gearbox.  Implementing an electric power steering pump is expensive, somewhat complex, and adds another load on the system to drain the batteries.  It also has a surprisingly large amount of space to fit everything I'll need during the conversion.  Right around Thanksgiving of 2011 I found a 1977 Porsche 924 that had bad compression (even though the engine ran) and bad brakes.  The deal was right so I picked it up.

Some other interesting info about this car.  It has a very low CdA (coefficient of drag x frontal area) of 6.96.  This reduces the amount of power required to overcome aerodynamic drag.

Thursday, January 12, 2012


I've recently taken the plunge and decided to convert a car to being fully electric.  I've also decided to try and document the process in blog form so all my friends can follow along and maybe some future converters can learn from my experience.  Stay tuned for updates and pictures.

Some of the basics and technical specs:
1977 Porsche 924
Warp 9 inch Series Wound DC Motor
DIY Controller based on the Open Source ReVolt Design (planned)
Approx 200 volt Battery pack made of 60 CALB 70 Ah Lithium Iron Phosphate Batteries (planned)
Existing Air Conditioning will be retained
Manual Steering
Vacuum Assist Brakes Retained
Estimated final vehicle weight 2600 lb
Estimated Range 48 miles
Estimated 0-60 time 9-10 seconds

Start Date: November 29th (when I bought the car)

Disclosure Notice:
All information on this blog is the property of Micah Abel unless otherwise noted.  All information should be used at the discretion of the reader.  Information should not be regarded as a design guide, and Micah Abel takes no responsibility for any actions taken as a result of reading this blog.