Sunday, April 26, 2009

Gas Gone and Top's Off

The final gas related components (well OK - not quite - the ECU is still left - but that's electrical) that needs to come out are the the 2 fuel lines and a vapor line that connected the gas tank to the engine compartment. The 3 lines are held in place by 7 clips or so that also hold in places the brake line going to the rear brakes. I had to remove all the clips, press the 3 lines out of them and then re-attach the brake line to the clips after I was done as there was no enough room to simply remove the fuel lines on their own. The hand-brake cable on the passenger side also had to be unbolted to make it easier to remove the fuel lines (as you can see in this picture, is crosses the fuel lines in the background).

After a bit of twisting and pulling all 3 lines were out.

In addition to converting the car, I'm also planning on a bit of renovation - the exact scope is still to be determined. But the number one priority on the list is to replace the 17-year old roof. It's been years since I was able to zip up the plastic rear window and there are numerous holes in the vinyl fabric. It got to the point where I would check the radar at work and if there was a storm coming, I'd have to take the baby car home before it hit and return in another, more weather resistant car.

I also need to take the roof off to access the back parcel shelf, which covers the space previously occupied by the gas tank. I'd like to use the space back there for some of the batteries, but that is going to require removing some of the sheet metal and having the roof removed is pretty much a necessity to accomplish that (for an example of some MAJOR surgery to make room for batteries, see the link to Andrew Schwarz's conversion.

So off it comes. Now, much as I'm enjoying documenting the details of what I'm doing, I don't see the sense in re-inventing the wheel and there is a terrific post at that gives all the details you could ever want on how to remove and install a roof on an Miata. So if you are tackling a roof replacement see that article or any of the other roof replacement articles in the 'garage' section there.

But to keep Brian happy here are some pictures I took and some notes of differences in procedure that I used. To give credit where is it due, the roof article is obviously where where I learned the trick of connecting 2 wrenches to get more leverage - here's me loosening the very tight bolts holding the driver seat.

Note the leaves above ... there are even more sitting under the seats when they come out (the perils of leaving the car sans roof most of the time).

The rear window hasn't zipped for years and getting the push fasteners holding the carpet covering the parcel shelf off was a lot easier with the window gone so I took a utility knife to it. Note the wonderful shade of brown that years of exposure to the sun have left it (no cracks though!).

Here is the rear shelf exposed now the roof has gone ... later we'll see what surgery I'm willing to perform on it (or not). Also note the 2 zip lock bags below, one in each seat position - I made sure store the various pieces removed from each side in the appropriate bag so I know which side to eventually reinstall them in.

The roof covering is not too difficult to remove from the frame (which obviously will get reused) but since I'll be getting a new covering I took some short 'cuts' with the good old utility knife again.

Tuesday, April 21, 2009

Decisions, decisions, decisions

I've not really talked much about anything EV specific so far, mainly because I've been concentrating on figuring out how to tear the car apart - I figured that if that didn't go well there was no point in making any decisions about EV components. But with nearly all the ICE components out, the car not looking any worse then you'd expect for one with half it's parts missing and all my body parts still attached it's about time to make some decisions about what direction I'm going in - if I don't I'm sure my better half is eventually going to get a little bored of a hunk of useless metal taking up a garage bay.

Since starting my investigation I've been kicking around 2 possible configurations. The first is a high-voltage AC (alternating current) system consisting of:

- a 320V battery
- an Azure Dynamics AC24LS AC Motor
- the matching Azure Dynamics DMOC455 Controller

or, a DC (direct current) system consisting of

- a 144V battery
- a Netgain WarP9 DC Motor
- a Curtis 1231C-8601 Controller

I liked the high voltage AC option a lot as higher voltage means lower current for the same amount of power, and lower current means better efficiency and hence more range. It also includes 'regenerative braking' (using the motor as a generator to assist when braking, so putting some of the car's kinetic energy back into the battery instead of wasting it as heat from the brakes). But the Azure Dynamics system seems a little anemic when it comes to acceleration from feedback I've found in build logs on the internet.

DC motors are less efficient, and you need to go through a lot of hoops and have a special motor controller to get regenerative braking, but they are far more popular for DIY conversions. Popular opinion is that a DC system is simpler than AC (though as far as I can see, AC systems have more components built in so appear simpler to me!) and there are certainly a lot more examples out there to draw on when I get in trouble/need help so I'm leaning that way.

I was pushed to make a decision this past weekend when I was able to hook up with a group buy for batteries. One think I made my mind up about long ago was what battery technology I wanted to use. Most conversions use good old lead acid batteries - 12-20 or more in series - to create a battery pack of around 144V. But if you've ever changed a battery in your car you'll realize that this is one heck of a lot of weight to add. Even accounting for the 250-300lbs taken out in ICE components, you're talking adding 600-1000lbs to the car - that's going to be a real drag on both acceleration and range.

No - I decided that I would be going with some form of Lithium Ion-based battery. The problem with these batteries is quite simple - cost! There are various battery chemistries and a battery pack can cost between 4 and 10 (or more) times the equivalent nominal capacity in Lead Acid batteries. They also require a sophisticated Battery Management System (BMS) to ensure that the individual cells are not over-charged or over-discharged and remain in proper balance, adding more to the cost.

However they have some huge advantages over Lead Acid batteries. The amount of energy they can store is 2-3 times greater than the equivalent weight in lead, and they are far more efficient in allowing you to extract that energy from them. Also their form factor is much smaller making them (I hope) easier to fit into a small car like the Miata. Lastly, while you can change/discharge the typical lead acid battery 400-600 times before you kill then (depending on how far you discharge them), Lithium Ion (specifically Lithium Iron Phosphate - LiFePO4) cells have up to 2000 or more cycles in them - making them at least as cost effective (though with a higher up front cost) as lead acid as you need to replace then less frequently.

My basic research showed that the typical cost of a 3.2V LiFePO4 cell was about $1.60 retail per Ah (Amp Hour - basically the measure of capacity of a cell - 1Ah means that the cell can discharge at 1Amp for one hour before it runs out). So for a 144V battery made up of 3.2V 160Ah cells I was looking at c. $11,500 before thinking about delivery, duties (these ALL come from China at those prices and a BMS) - ouch! However as luck would have it, I was able to hook up with a group buy of cells that was being put together by someone that reduced to price to a much more palatable $1.10/Ah - or just over $8000 for the battery itself.

That battery should give me a range of about 75 miles or so. That assumes that on average I'll use 250Wh per mile which seems typical. The total capacity of that battery is 144V (45 * 3.2V) * 160Ah, or 23KWh. The battery specs say that they can be discharged 80%, making 18.4KWh available - hence the c. 75 mile range. I might get a little more or a little less, but as my commute is only 4 miles one-way and the longest trip I typically take in the baby car is to RFK Stadium and back for a D.C. United soccer game - about 60 miles round trip, that's plenty enough for me. So I plunked down my 50% deposit with Dave and James from EV Components today for the battery which should arrive in about 12 weeks.

So I've thrown my hat into the DC pot ... now I have to figure out all the other bits and pieces I need to order.

Sunday, April 19, 2009

Subframe and Gas Tank Out

Back from the excitement of my ride in the Tesla Roadster I was raring to get the last vestiges of the baby car's gas legacy out. To continue removing the rear subframe I needed to disconnect the hand-brake cable from both rear brakes - this is a lot easier with the wheels off. The hand-brake cable is the lower of the 2 lines in this picture.

Here you can see the nuts holding it on the driver's side loosened - then it's a case of a little twisting and turning of the cable end to get it released.

Now to disconnect the lower arm of the suspension from the shock absorber. There is a single bolt that the Haynes manual says to "hold with a socket while you loosen the nut" ... well that's rubbish ... you can't access the nut at the other end ... and if your could I doubt you can turn it. Simply loosen the bolt and remove it (I did need to pry up on the bottom of the shock to take some weight to get the bolt out).

Now for the fun bit. First I put my jack back under the differential and jacked it up just enough to start taking it's weight (not enough to raise the car body off the jack stands). The rear subframe is held to the chassis by 2 nuts (fornt and back) and 1 bolt (middle) as you can see in this picture.

Now time to use my newest tool - a Craftsman Impact Wrench. As recommended in the article on doing this I used a 19mm deep impact socket and a 6" extension and the nuts/bolts were gone in no time - if you do this yourself get an impact wrench - it's not an option! I started lowering the jack but found the subframe was hung up somewhere ... ah, ha ... I had released the cable loom from the torque bar before I removed the splash guard in the wheel well so I missed the cable tie connecting it to the subframe here

And this bracket which presses into a hole here - you can get that out by squeezing the little clips on the backside just like the wire loom connections to the torque arm.

My next door neighbor, Paul, helped me lower the subframe to the ground (we had to manually lift it off the jack).

Then I dragged it out, jacked it back up and attached the wheels so I could move it around easily.

On to the gas tank finally. First the 4 screws holding the filler in place come out.

The inside the trunk the cover protecting the filler and vent pipes need to come of by removing 4 bolts.

Then you loosen the pipe clamps closest to the tank.

And work the rubber lines off (they come of quite easily).

Under the car there is a plastic cover described in the Haynes manual as the 'Tank protector'. Well it's named wrongly ... it actually protects what I think is the gas filter.

Now I needed to disconnect the connections on top of the tank. To do that the carpet covering the rear parcel shelf needs to come off. It's held in place by 5 plastic push-in connectors. I used a V-shaped pry tool with a screwdriver handle underneath to increase leverage. For some reason the 2 connectors behind the driver's seat were broken before I got to them :(.

Lifting back the carpet and padding exposes the tank access cover which releases with 6 screws.

And here is the top of the tank. The electrical connector to the fuel pump and the 3 lines (2 fuel and 1 vapor return?) need to be removed (I broke the plastic tube connecting the 3rd one by pulling too hard :( ). See all that material on top of that tank? I though initially that was some insulation ... but the I got to thinking why would anyone put some loose insulation there? When when I pulled it out I realized that it was a rodent's nest! Apparently a mouse had worked its way into the space above the tank and built a nest - glad I found that before I pulled the tank and had the 'contents' fall in my face!

I propped up the tank with the jack and a 'few' supports. Yes that is not very stable! But I was able to slowly lower the tank after removing the 4 bolts holding it in place using a plastic bucket and a staging area before removing the wood.

And the gas tank is out. I drained a gallon of gas out of it, and it feels like there is a gallon left - I'll get that out when I have another container to put it in.

I didn't quite manage to get all the gas components out - I'll get to that later in the week.

EV Inspiration

After I finished work on the car yesterday I took our dog to the local dog park. As I entered the parkway by our house I noticed one of those 'board twirlers' - you know, the guys standing at street corners advertising some furniture sale, or apartment complex or, as in this case, new subdivision trying to sell $1.5M houses in our wonderful economy. Well normally I ignore them, but the light was red and for some reason, while stopped I look over at this one ... and my chin hit my chest ... the new subdivision behind ours was offering test rides in an Tesla Roadster for anyone who visited their model home.

It was too late yesterday (and I had the dog in the car) so this morning I popped over as soon as they opened and YES, they were doing it again today! Sitting out in front of the model house was a red roadster.

I signed up for the hourly raffle for one of 4 test rides and had a look around the house - very nice it was too - but out of my price range thank-you (a bit like the Tesla too I guess). I also chatted to the Tesla sales rep for a while and to the Camberly Homes sales folks and let them know what I was doing with the Miata - that drew a bit of interest. Lucky too, because although my name was not one of the 4 out of the hat, I got a test ride anyway!

And what a blast - even though I was only a passenger, I can now appreciate what an EV Grin feels like. The acceleration of the Tesla is phenomenal - I was literally pressed back into my seat as the driver showed off it's paces.

So a big thank-you to the folks at Camberly Homes' 'Reserve at Stone Hill' development - you definitely made my day today!

Saturday, April 18, 2009

An Exhausting Day

Today was set to be a busy one ... but mostly not because of the car. I started out at 5:20am, getting up and packing the car with soccer equipment to drop off for the first day of the season - I'm the coordinator for the youngest age groups at our local youth club Chantilly Youth Association - about 700 of the c. 2300 players in the soccer program. Then back home and out again at 7:15am to take my oldest daughter to the "Solo & Ensemble Festival" for her flute recital. Next back home to pick up the youngest and take her to breakfast at IHOP for her birthday (she's 11 today) and from there to her volleyball game (also part of Chantilly Youth Association) - her team won their match 3 games to 0 :). That done, back home to cut the grass and kill a few weeds ... whew ... finally time to get something done on the car.

The last remnants of 'gasness' remaining are the exhaust system and the fuel system. The catalytic convertor, exhaust pipe and muffler are hung from brackets using rubber hangers that are easily pried off with a screwdriver (or if you're not going to be reusing them like me, cut with a utility knife). That leaves the cat lying on the ground.

But the muffler and exhaust pipe are hung up on a brace that connects the 2 sides of the rear subframe. I guess if I disconnected the cat from the exhaust it would be possible to pull the pipe out over that bar, but no way is that happening with the cat still attached (and you'll remember how impossible getting the bolts off the cat was when I was trying to disconnect the down pipe when taking the motor out).

So that bar is coming out ... note to self ... just because something looks like a nut doesn't mean it turns like nut. If you look at the connection you'll see a bolt that goes from the underside through the bar and is capped by a nut on top. I spent about 20 minutes trying to loosen that nut before I looked closely and found it was welded to the subframe! Loosening the bolt was a lot easier! With that done, the exhaust system was out (note that was after I had completed the tasks below - I had to 'think' a bit about why that nut was not moving).

So now on to the fuel system. The fuel tank in the Miata sits in a cavity between the trunk and the passenger compartment. Very safe I'm sure, but not very convenient to remove. The only way to do it is to drop the entire rear subframe to make room for the tank to drop down and be removed. I've seen a couple of Miata conversions that decided the effort was not worth it and simply drained the tank, capped the lines and left it there. However I want that space for batteries so it's coming out. Luckily I found a good article at that gives a great procedure for removing the tank.

Unlike the factory procedure, this one leaves the torque arm attached to the differential. This means that the wiring conduit clipped along it's length needs to be disconnected - squeezing the plastic clips on the drivers' side with some needle-nose pliers and pushing them through does the trick.

Next the ground wire connected to the torque arm at the rear gets disconnected.

Now the rear brake lines need to be disconnected. There is a single line going into a block on the passenger side just in front of the subframe assembly.

Here's another view from in front of the rear tire - the flare nut looks a lot easier to get to from here.

So off comes the splash guard to give me some room.

Then the brake lines comes off and the brake fluid starts dripping. And dripping and dripping ... essentially you're draining your brake fluid reservoir so it takes a while. So while I was waiting, back to the front of the car to see what I can work on there. Ah, ha, the charcoal canister and electrical connections for the emissions control system are still there.

So off they come.

Back under the car waiting for the incessant dripping to stop, I noticed that there were a couple of heat shields - one between the muffler and the trunk.

And one between the cat and the underside of the driver's seat (what ... no seat warmers!).

So they both come off.

That's it for today - time for a trip to the dog park with the pup, then birthday cake and finally Spike TV is showing the first Star Wars trilogy - so I'm off to watch that (yes, I'm a geek :) )

Tuesday, April 14, 2009

So long, farewell ...

There's no turning back now ... the engine was picked up this afternoon. We had a fun time getting it into the back of the SUV that the guy who picked it up arrived in. Strangely enough I knew him - his daughter played on a travel soccer team that practiced at the same time as mine for a few years. He lives very close by so I guess I now have a knowleable resource close by to lean on if (I mean when :) ) I get in trouble (just kidding Greg!).

We had to man-handle the engine in as the hoist obviously couldn't fit into the back of the SUV. I was 'fortunate' enough to discover the remaining coolant in the engine block when we tilted it and it flooded out one of the open hoses and down my pants :(. Here's the engine tied down in the back of the SUV.

It's going to be rebuilt and then raced by Meathead Racing - here's their website:

Sunday, April 12, 2009

Gas leak

At lunchtime my daughter comes in from the garage to tell me that there is a stong smell of gas so I go out and find a large puddle under the car (needless to say I did not bother to take some flash pictures of the spillage). After removing the engine, I had capped the gas lines with duct tape ... but then I closed the gas cap. Bad idea! As things heated up the next morning the air in the gas tank expanded and pushed the gas in the lines out past the duct tape :(

So now the car is sitting with the gas cap loose to prevent pressure build up in the tank and the gas lines are capped with silicon sealant "just in case". Fortunately it's meant to be cool all week ... but it looks like I'll definitely be pulling the gas tank next weekend.