Daily Archives: October 7, 2018

Saying is one thing

Doing is another. Apparently telling myself to not think about building the T-Bucket is about as effective as telling my senators to not vote for a serial sex abuser for the Supreme Court. And that is about as much as I’m going to say on that subject. Anyway, even after I decided to stop I still thought about building the Sprint-T. As in thinking about how much power the JDM EJ20X Subaru engine made stock, 260 on 93 octane at 12 pounds of boost, and the factory compression ratio is a very 87 octane friendly 9.5:1 for driving around at zero boost. So the plan to tell the engine to leave the waste gate open and dump boost with 87 octane and pump up the jams with tons of boost on E85 is sound from an engineering perspective assuming the ECU I buy is compatible with that 2 map scenario. I know the Microsquirt has a second fuel/air table that can be mapped to boost as in a separate table that starts at 100 kPa (sea level atmospheric) and goes to whatever the MAP sensor I install stops reading, which with the GM 3 bar MAP is 300 kPa (100 kPa is the same as 1 bar) and the Microsquirt comes from the factory calibrated to the GM 3 bar sensor. This would result in off-boost using the 87 octane fuel map, which would be leaner than what would be best for full power with E85, but there’s no way around that except swapping $314 controllers for racing or buying a controller that costs more than buying two $314 controllers. Incidentally one of my overboost control schemes is pushing the injector pulse width to 100% to possibly stop the engine from firing because of too much fuel, or to at least make it run really bad and keep it from blowing up. This is a “Last Stop” scenario, as in last stop before the engine destroys itself. A good engineer tries to prevent disasters before they happen by doing what I do best, thinking about things, in this case things that could go wrong and what could be done to either prevent it or undo it.

I was also thinking about the gas tank/fuel cell some more, specifically how much room I had to the left of the centersection of the quick change rear axle. This is important because I need to have clear access to the centersection to change the spur gears to adjust the final drive ratio and tune for the course. I made the executive decision that rear overhang was not an issue as long as it was stuff that wasn’t heavy for racing, regardless of how much it weighed for normal street or in-transit driving. Also thinking about range between refueling and that possible transit across Wyoming for whatever reason, I made the SWAG that the Subaru engine in the Sprint-T would get 27 MPG highway. I did that from 2 data points, my old Hyundai with a 4 speed transaxle without overdrive got 33 MPG driving to and from Nashville from Dallas back in the early ’90s, and even the Hemi engine in a Ram pickup is rated at 22 highway. With the QC rear axle I could pretty much select my cruise RPM no matter what transmission I eventually got so the big problem would be the drag of the exo-frame around the bucket body. And I bundled all that and extrapolated 27 MPG. My sitting limit is about 5 hours depending on how supportive the seat is and how hydrated I am, so I really want to have about 5-7 hours of range, just in case, and tossing all those numbers in a blender set on Puree gives a range of tank size of 12 to 20 gallons, with the cheap and available 16 gallon cell falling right in the middle with 430 miles from full to tank dry. And with the product I intend to use for the fuel pickup tank dry is really tank dry.

I really, really want this car built, and I want to be the project manager for the build. And I want to race it at Goodguys and SCCA regional and national Solo races after driving it there without putting it on a trailer. Trailers are for cars that are not really street cars.

And this is the twelve pack of microfiber cloths I bought at Harbor Freight.
pack of microfiber cloths for washing things