Daily Archives: April 29, 2021

Still trying to get stuff done and not succeeding

Weather and sleep schedules are interfering with actually doing things in a timely manner. I staggered around until about 1130 before collapsing and eventually shutting down completely about 1230 or 1300. I woke up enough to check the time about 1900 and finally got out of bed in time to catch Biden’s speech about 2100. Pollens are still interfering with my sleep, making getting shut down to sleep hard, and then making it hard to get fully awake with working eyeballs.

Still trying to figure out the engine situation for the Sprint-T. I mean what I want is maximum torque for getting out of the single-pylon turn, which implies a mild cam, long intake runners, and hopefully a lot of displacement. Or maybe (also) small turbos that light up more quickly than big turbos and a small displacement engine. I’m looking for either a large displacement engine or a good turbo manifold. Also VVT. Changing timing can drastically change the points of opening and closing of the intake valve and move the torque band from lower to higher RPM. That will be fun, but not earth shattering. Basically VVT extends the powerband a tiny bit and makes the long runner intake work over a wider RPM range. Dangit, I know what I’m trying to say, but I’m having a terrible time trying to get my ducks in a row to say what I mean.

Basically VVT widens the powerband a scosh compared to fixed valve timing, but it doesn’t work miracles. There are some Engine Masters videos on the subject but if you aren’t a subscriber you can’t view them. I did link some YouTube videos earlier that explain the benefits of moving the cam timing, well VVT lets you do that while the engine is running, about 40 degrees for the late model Gen IV or about 50 degrees for the early versions. Naturally you have to check piston to valve interference at the extremes of adjustment to make sure you don’t get the pistons hitting the valves because the VVT changes the valve lift at the point the valves get closest to the pistons, and for some cams the valves will actually contact the pistons unless the swing on timing is reduced. Or move the swing away from the interference, which is a thing also. Like I wrote earlier it’s something that needs to be explored more thoroughly, probably by someone with more resources than me. The best that I can do is get the biggest VVT cam I can find and pair it with the longest intake runners I can find and then swing the timing to see what performance benefits I can find. I’m hypothesizing that running VVT advance at part-throttle cruise could generate better mileage, and if I see evidence of that in the VVT map I’ll have verification of that hypothesis. But on the other hand if I don’t it doesn’t mean it’s not true, just that it isn’t programmed into the ECU, probably because there wasn’t enough benefit to justify programming it into the system.

OK the sun is up now, time to “make the doughnuts” and if you get that reference you are either old or you like really old commercials.