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How and Why Your Engine Does What it Does

Discussion in 'Multimedia' started by PatB, Dec 1, 2013.

  1. #1 PatB, Dec 1, 2013
    Last edited by a moderator: Jul 13, 2015
    While looking for something else, I just came across this video of a talk by UK engine guru David Vizard. OK, so it's car, and more specifically Mini, oriented but the principles he discusses are sufficiently fundamental that they are entirely applicable to bikes.

    His explanation on why 4-valve designs generally work better than 2-valvers (at about 27 mins I think) I found particularly interesting and pertinent to many discussions on NR over the years.
  2. Maybe some harley dinosaurs at head office should watch it
  3. Right, better wait until I have some more spare time then!

    Did he say anything about 5 vale heads?
  4. I'm not an engine designer, so have no influence over what is installed in my ride. While interesting, the riding experience helps determine my choice of bike.
  5. Not as such, 5-valvers being rare (possibly non-existent) in the car world. However, the points he makes about 4-valvers will also apply to 5-valvers but more so. The crux of his argument is that multi-valve setups flow better at partial valve lifts, where the valves spend most of their time during the engine's cycle. This assists the engine to make good power over a wider rev range than a 2-valver. It certainly bears out what the seat of my pants tells me about broadly similar engines with different head architecture (mainly Suzuki GS/GSX variants).

    Fair enough, but it's not just engine designers who influence what's inside or around your engine. You may not do it, but many people on here have played with exhausts, air filters and carbs at least, and cam swaps are not uncommon so a little easy to follow general information on why some of this stuff works (and why some doesn't) from someone who really knows their shit after decades of both experimentation and theoretical study isn't out of place.
  6. Holy shitballs, 2 hours???? Ain't nobody got time for that!

    Is there a tl;dr version? :D
  7. This could be interesting. Nice find!

    Aren't there some Farraris with 5-valves per cylinder?
  8. Some of the Audi Quattros has a 5 valve head.