Month: March 2019

Yesterday afternoon I had such a “duh” moment. I realized that I can use a Megasquirt system on the Saab engine I was originally planning on using. So now the plan is to get myself a 2004-2011 Saab 9-3 2.0T with the B207R engine. 2003 and 2008-11 all wheel drive models had secondary air injection which is stupid. I can remove it, but it’s just easier to not have it in the first place. Hopefully, I’ll be able to use the car’s original computer to run things, but if that’s not possible I can always go with Megasquirt. This engine would be easier to run with Megasquirt than the LE5 anyways because the B207 doesn’t have variable valve timing.

I took a look at the LTG engine dimensions on the GM crate engine site earlier today. At about 27.3 inches tall according to GM, the LTG is probably too tall to use in a Locost, at least easily. The Locost forums say that the Miata 1.8 liter engine, a popular choice, is fairly tall at around 23 inches and requires the oil pan to sit below the frame rails. Clearly then, the LTG is too tall. Turns out it’s tricky to find dimensions (overall length, width, height) on most engines, unless they’re offered as a crate engine or are very popular in standalone applications, so I’m not totally if an LHU or LNF would fit either. I’m not totally sure if any Ecotec engine would fit, but I think I’ve found a decent option.

Obviously, buying a whole car to extract the engine, accessories and wiring from would be ideal, but I’m not sure it’s going to be possible for a low enough amount of money. The cars containing the LNF and LHU engines are still fairly new, and in the case of the LNF, rare. It’s pretty unlikely I’m going to find a rusted out 2013 Buick Regal Turbo. So a more common and older engine would be easier to work with.

I think I’ll be setting my sights on an LE5, a 2.4 liter naturally aspirated four cylinder found in a bunch of shitty, uninspiring GM cars from 2006 to 2012. In the form I’m most likely to find, it puts out 169 horsepower and 162 ft-lbs of torque. That should be totally fine for a 1500 or 1600 pound car, even though it’s not the 260 horsepower of the turbo engines. I think I’d probably run the engine with a Megasquirt 3 system, which should be able to deal with the engine’s variable valve timing and avoid the headache of using the GM ECU without the rest of the car. The Megasquirt is also infinitely tuneable, so with some effort I might be able to eke out a little more power. And if I want a lot more power, the turbo from the Saab 9-3 bolts on with some effort. I’m looking into grafting on the individual throttle bodies from a motorcycle for this engine. I might even be able to

So that’s where the project stands for now. Today and tomorrow are going to be pretty warm, and hopefully it stays that way. I need to get the garage in ship shape before I start building anything.

The Suspension

Last week we got a Saturn Sky in at my work. Since they came out, I’ve always thought they were a great looking car, maybe even a work of art. The interior, it turns out, leaves a lot to be desired. It’s everything terrible about GM from 10-15 years ago, but I suppose it was a pretty inexpensive car when it was new.

By Reedred – Own work, CC BY-SA 3.0, Link

The Sky/Solstice was built on the GM Kappa platform, a brand new design for a two seat convertible similar to a Miata. Knowing this, I was interested to inspect the suspension design on this car. The Miata, at least the NA and NB generations I’ve looked into, have simple front and rear spindles that are easy to adapt the the Locost design. It turns out the Sky might be even better.

The front and rear spindles appear very similar (I suspect they may even be identical). They’re made of aluminum, which is appealing due to its lighter weight than the Miata’s iron spindles. Both front and rear take ball joints top and bottom, with a tie rod in the middle. This is the same as the Miata in the front, but different in the back. The Miata does not use ball joints in the back, just a simple clevis. The ball joints and tie rod on the Sky allow the toe to be adjustable in addition to camber. The only thing I don’t really care for is that the wheel speed sensor is integrated in the wheel hub/bearing assembly. They’re a lot more expensive than a press in bearing and I’m not sure yet if I can make use of the sensor.

They didn’t make a ton of Solstices and Skies, so finding a reasonably priced parts car a reasonable distance from me would be tricky. Luckily the parts I need are available for an okay price on eBay. On a whim, I cruised around and ended up with a set of four brake calipers with bolts and hoses, and both rear spindles. The calipers were $120, and the spindles $112. I think those are pretty tough prices to beat. If I decide not to build the car, I can always clean up the parts and sell them for a bit more than I paid.

The Drivetrain

My original plan was to use the B207R/Lk9 out of a Saab 9-3 2.0T. They’re very easy to find for cheap in my area. I’m also a Saab mechanic, so I can get any parts I need to refresh the engine and I have easy access to parts and electrical diagrams. I’ve decided not to use this engine though. While it’s a GM engine, there are a few proprietary Saab parts, the ECU among them. At work, we replace ECUs on 9-3s very frequently. The “new” ones aren’t new anymore, they’re rebuilt and have a high failure rate. The parts company has introduced another ECU part number, but using it requires modification to the wiring harness, and I suspect it won’t be any more reliable than what we already have.

With that in mind, I decided to look for new engine options. If money was no object, I’d probably go for an aluminum block GM V8. But money is an object, so I’ll have to go for something less expensive. I think a four cylinder of 2 liters or less is more in the spirit of the Lotus 7 anyways. I took a look at GM’s current crate engine offerings. Their four cylinder option, the LTG, looks like just the ticket. Of course a new engine would be way too expensive, but the LTG is available in several production cars in both front and rear wheel drive configurations (I’m not sure what the difference is and whether it’s important to me though). It puts out up to 272 horsepower and 295 ft-lbs of torque, depending on the car. The LTG can be found without too much trouble in the Cadillac ATS, Buick Regal and Chevrolet Malibu. It seems to be fairly inexpensive to get a wrecked Regal, so I’ll probably try to take that route. The LHU, as installed in the Regal GS or Buick Verano Turbo, would be a fine alternative to the LTG. The LNF, in the Solstice GXP and Sky Red Line would also get the job done, but would probably be tougher to track down.

Any of those engine options should mate easily with the AR5 transmission I’ve been planning on using. I’m not totally sure about options for a flywheel and clutch, but it shouldn’t be terribly difficult to figure out. I hope.

With all this GM stuff, it makes sense to use a GM differential. My ideal choice would be the 3.73 limited slip unit out of a Sky Red Line or Solstice GXP. Those seem a tad expensive for me, so another option could be the 3.42 limited slip differential from a Cadillac CTS. I’ve read they’re the same basic thing, but I’m unsure if the Solstice/Sky axles would fit right into the CTS differential. I’m also concerned about having to have the axles shortened or lengthened because I suspect (but don’t know) that it might be expensive.

So that’s where the concept for this project is at the moment. I’m still not totally sure if it’s going to happen, mostly because my garage needs to get into decent shape before I build anything. The majority of the work shouldn’t be very expensive, but getting someone to add a few electrical circuits to the house might be. I’ll have to call some places and get estimates. After that’s done, the holes in the siding need to be fixed, new overhead doors need to be installed and lighting and electrical outlets need to be added, all of which I can probably handle myself. We’ll have to see how it goes.