Some of you folks may remember my three cylinder G10 powered Miata from a few years ago. While that project was an overall success, it had limitations. Moving forward, I took what I learned from the G10 project and built a B3 powered Miata. The B3 engine is a 1300cc 63HP SOHC powerplant from a Ford Festiva. Although similar to the Mazda 323 and Ford Aspire engine, the Festive engine has a few components that allow a better fit in a Miata chassis.
The B3 project has covered 50K miles and returns an average MPG of low to mid 40's. This is real world MPG and no special driving procedures are done. The car is equipped with A/C, power steering and a full interior. The transmission was modified for a slightly taller 5th gear to reduce cruise speed RPMs. Tipping the scales at 2260 lbs the car isn't too heavy but it also not light weight.
The Miata with a Festiva B3 engine. So far the car has covered 50,000 miles.
My original goal was to get an average of 50MPG and after almost two years of struggling it was clear that I would need an engine dyno to develop and test modifications that will work in the real world. .... so I built an engine dyno.
the dyno
This dyno was set up to develop engine tunes for the 2000-4000 rpm range Focusing on the cruise speed sweet spot is my intention. Experimental tests are semi limited to a maximum of 20 minutes of run time because of cooling issues.
The power absorber is a hydraulic pump mounted on trunions and is equipped with a torque arm and load cell. The load is electronically measured and adjusted every few seconds so the temperature and viscosity of the hydraulic fluid is automatically compensated for.
A Megasquirt II is being used for engine management and real-time data gathering. Eventually I'll add more instrumentation as budget allows.
The B3 engine is an eight valve lump that develops more torque than horsepower. it's vastly different than the modern multi-valve engines so not all the experiments will translate to modern engines.
As you can see in the pictures, this dyno was built with an identical drivetrain that is being used in the B3 Miata.
The dyno has taken almost six months of evenings and weekends construct and the build is in its finial stages. I'm currently focusing on software and data gathering hardware at the moment. I expect to have the odds and ends sorted out within the next few weeks.
Because of the dyno, I would like to focus this build thread on engine modifications. The dyno will allow rapid development and testing of ideas and if the ideas prove out they will be incorporated in the B3 Miata. Right now the Miata is more or less off the road for the rest of the winter and we won't see any real world results until spring.
I hope to get some feedback from anyone interested in following this project. I'm looking for ideas to test on the dyno. Anything from conventional mods to down the rabbit hole stuff. The only limitation is this is an extremely low budget project. The good news is I can fabricate almost anything so most of the custom machine work won't add too much to the budget.
Here are some videos of the progress..
Mazda B3 first start engine Dyno - YouTube
Mazda B3 engine dyno first load test. - YouTube
B3 engine dyno control test... making torque! - YouTube
For more info in the Miata build, Google "B3 Miata"
For more info in the dyno build, Google "B3 dyno"
I look forward to hearing your comments and ideas of what we can test. Please keep in mind that this is an engine development thread and although aero mods save fuel, they don't work on a dyno.
Jim