As you can see in the picture below, BB's new muffler has a much bigger pipe than the stock one. In fact it is almost 3x the flow area. That's because the new engine makes 2.6x as much horsepower. To make horsepower from gasoline you need to burn it with Oxygen. Thererfore, BB's new engine will push 400 cubic feet per minute though. That's an 8 foot cube of air every minute. That needs a big pipe!
Which brings us to how gasoline cheats against batteries. You may have heard how heavy the batteries in an electric car are. The Tesla Model 3 has a 1200lb battery pack! The equivalent range tank of gas weighs 110 pounds. One's first conclusion is that gas is more energy dense than Lithium. But we have to remember the Oxygen! We are swimming in a sea of Oxygen. The Oxygen is actually the heavier part of the combustion reaction with gas. If you had to carry around a tank of compressed Oxygen with you in addition to your gas tank, You would be around the same weight as the battery.
This would seem to bode favorably for Lithium Air batteries. That's a battery that uses the atmosphere as the Anode. It has an energy density similar to gas. Unfortunately, it is very challenging to implement. As it takes on Oxygen to charge, it expands dramatically and basically tears itself apart. If this challenge is solved, there will be no competition between a gasoline and electric car. Let's see what happens!
Originally, I thought I would get the stock manifold to fit with some machining. That was not to be, geometry being what it is! So I designed a header-like manifold welded from tube sections. I wanted to keep the flow as smooth as possible and present as little obstruction as possible. It took a lot of measuring, sketching, thinking, resketching, etc. to hit on this design. It's far from perfect but shouldn't inhibit performance much. I'm hoping that without catalytic converter and with a Flowmaster performance muffler, I will be a little better than a stock RX-8.
I did the initial machining on the bench and milling machine. I used the stock manifold as a rough fixture but did the final fitting and tack welding bolted to the engine to be sure things fit. That's not easy welding upside down with your welding helmet wedged under the brake rotor!
The rest of the exhaust was much simpler, being square of 45 degree cuts that I could then tack together.
I had to move the pipe to the center of the tunnel as that was the only place I could get through the rear suspension!
I had to enlarge the opening in the rear panel to fit the bigger pipe!
I decided to paint the entire exhaust system black to match the muffler. This I did as yard sculpture:
Several neighbors paused for a glance, but they are by now used to the antics of the local Caractacus!
Here is the header after paint. The leak checking was very interesting.
I blocked the outlet with a grocery bag and a rubber band and blew compressed air into the slot in the duck tape. By the way, I recently learned that I've been wrong for years about Duck tape. I always thought it meant Duct Tape, since it is used for sealing ducts. However, it seems the Army commissioned it for use in wet environments, so it was called Duck Tape! Live and learn!
I also learned that I have poor observation skills. I had forgotten about 2" of seam entirely! My other welds also leaked like sieves! By the time I had it sealed, it looked like old bubble gum under a high school desk. But, it seems like it will hold exhaust gas...finally!
Here is the exhaust manifold/header on the engine before re-insertion!
On the left is the finished view with Oxygen sensor in place! To the right, is the system before inserting the header.
The acid test is the start up, but we are some weeks away from that. It looks better than I imagined though!
Anyone who knows MG's will be shocked at the size of this pipe! Bang, Bang, Chitty-Chitty Bang-Bang! Keep having #funwithcars!
Comments
Post a Comment