I finally got some sleep today after staring at the wall until ~0700. I went to bed about 0300 and tossed and turned trying to find a comfortable position to lie down. Then I had to get the brain to shut down and let me sleep. But good news Mrs. the Poet went out to do some things and got me my new scrip for anti-depressants filled. Now I just have to wait until I build up enough in my tissues to hop the blood/brain barrier and start anti-depressing me.
I never got too depressed to stop thinking about my engine in the TGS2. Like I posted a few days ago I did some research and reverse-engineering to determine I had 55cc combustion chambers on the head side. That means I probably won’t have to angle-mill the heads to get the combustion chamber in the head down to 44cc, but I probably will just to keep as much material on the deck surface as I can for stability. As much as I would like to believe it to be otherwise, aluminum heads are not rigid structures and flex under the loads of combustion, causing them to loosen over time and eventually blowing head gaskets. Leaving the deck surface as thick as possible helps reduce this flex, which is why I’m going to angle-mill instead of straight milling the head surface. Ideally I would fill in the combustion chamber to make it smaller and stiffer, but this requires access to materials and machining processes that I don’t have access to. The reason why I would do this over milling the heads is adding to the combustion chamber makes it stiffer, and I can move things around to improve intake and exhaust flow while reducing the chamber volume. But as I said I can’t get to the machines I would need to do this so I will angle-mill instead.
Something else I have been thinking about is moving the injectors to get more fuel cooling of the intake charge. E85 fuel has a very high latent heat of evaporation that can drastically reduce the temperature of the intake charge, but it has to have time to work for that to happen. What I was thinking about doing was moving the injectors from right next to the head surface of the manifold to the top of the intake plenum aimed straight down into the ports with the manifold changed to a more vertical plenum on top rather than the bent over runners and plenum on the side on the stock manifold. This would still keep the same mixture distribution as the stock injector position next to the head in the middle of the port, but gives the entire length of the port for the fuel to evaporate and cool the charge before it enters the cylinder. This would improve both power and economy as a cooler charge can work with either more compression or more spark lead, either of which makes more power at WOT and better economy at low throttle openings. The fact that working on combustion chamber design and mixture distribution improves WOT power at the same time it helps part-throttle economy is a big reason why we have 300 HP cars that deliver 40 MPG highway these days. It’s a combination of aero and engine efficiency reducing the amount of power required and getting more power out of the fuel used.
I’m from the days when knowing how to change jets and power valves was required to tune a modified engine, now you need to know how to alter a fuel table in a computer to do the same thing. I can understand why some of us fogeys are upset at the change negating hard-won knowledge, but TBH changing fuel tables in a computer is just better. For one it’s a lot cleaner than changing jets and power valves, besides being more precise. But there is still one old skill I’m going to need when I start working on the TGS2 engine after the conversion to E85: I can read spark plugs for heat range. And E85 at 14:1 compression requires a lower heat range than 87 Octane at 9.8:1, but nobody knows exactly how much lower. I’m going to start with stock and give them a read to see how much lower I need to go to save buying an extra set of plugs. Or I could buy 6 individual plugs at 6 different heat ranges and give them all a pull at the same time and go buy the full set of the one that reads closest to perfect. In fact I think that is the solution. A fast cheap solution to finding the best heat range for the E85 conversion.
And My Goodness I have been wordy today, 800 words to be semi-precise. Feeling better makes me write better and writing better makes me feel better. Yay!
Witch on a Bicycle 