Quote:
Originally Posted by MetroMPG
Hey Dave -
You're right there, for sure.
I think there's a misinterpretation about what the BSFC map is telling you, in terms declaring an "ideal" cruising RPM.
The engine produces power most efficiently at 1800 RPM, but that's when it's making about 55 hp. In other words, if you need 55 hp, 1800 RPM is the place to be.
Best BSFC RPM doesn't necessarily = lowest fuel consumption at lower engine loads. Since you're probably only going to need roughly 12 hp to go 60 mph on level ground, lower RPM would be better. Tasdrouille figured the sweet spot is more like 1250.
But since, as you say, you've already stuck the tallest possible OEM 5th in there, it's kind of moot (as I admitted in my comment above); any further discussion is just so much fuel economy geekery.
Unless of course you wanted to make a new 5th ratio... like this guy, or this guy. 
Congrats on the project, and the really good writing. Can't wait to see what you guys did in Cali with the aero doctor.
Darin |
What we did in California? Try what we
do in California... This thing is real-time. What you see in the stories is only a couple of days behind reality. It's going up as fast as we can write and process. We start fabbing aero parts tomorrow.
I'm pretty sure we found a BSFC map that showed several different load conditions and made our conclusion from that. We weren't really 100% certain the map was from our engine, though... Unfortunately, I've lost the map. As you can imagine, working on this timeline is a little hectic.
Glad you're enjoying the project, thanks for the support.
-Dave