Dave, your mention of David Vizard gave me a vivid flash back to my younger self. I messed about, as many did in the '60's, with minis and other A series propelled devices. David Vizard was to the A series as Kieth Black was to the Hemi in my book! Try googling or YouTubeing "Harold Bull's Strip Duster" for an extreme A series. (Although I don't know if "King Harold" used any of Mr Vizard's tips and designs)
Freevalve looks very technically interesting and obviously has many advantages in terms of performance, economy and environmental conservation. However I would want to see it in production for quite a few years before I committed to buying a vehicle which used it. A separate, complex looking, electro pneumatic hydraulic actuator for each valve and yet another ECU. Ok perhaps if you buy it new and sell it while it's still young, but an older one? I can see the pound notes migrating from my wallet even as I think about it!
Before I bought my present daily driver (SEAT IBIZA Ecomotive.) I nearly went for a Honda Jazz with the i-vtec engine. Honda's vtecs have been around for a long time now and their innovative variable valve control is well known and reliable. Mostly it is used to vary valve timing at higher revs to produce more power, and it does. The Jazz's i-vtec (the i standing for intelligent) is a little different though (think it's the same on the 1.8 Civic). The variable geometry is not employed at high revs. Medium to high revs cam profile doesn't alter. But at low revs, when the engine is under light load, the variable geometry is used to keep the inlet valve open way past Bottom Dead Centre. This allows inlet charge to be pumped back into the inlet manifold which greatly reduces the energy lost compressing a full charge. There is some clever stuff going on with the electronics in terms of throttle body control too I believe?
There are similarities here with engines which run according to the Atkinson Cycle which makes interesting reading. Miller cycle anyone? Once you start looking at this you won't believe how many weird and wonderful internal combustion engines people have thought up! - Makes a Wankel look positively mainstream!
Somewhere, in the Becky threads I think, we were talking about "dialing in" camshafts. If you Google 'Burton Power' and search "adjustable duplex cam sprocket set" you'll see examples of specially made sprockets which allow for variation between the position of the camshaft in relation to the sprocket teeth. A lot easier than hand filing up offset Woodruff keys as we used to!
Freevalve looks very technically interesting and obviously has many advantages in terms of performance, economy and environmental conservation. However I would want to see it in production for quite a few years before I committed to buying a vehicle which used it. A separate, complex looking, electro pneumatic hydraulic actuator for each valve and yet another ECU. Ok perhaps if you buy it new and sell it while it's still young, but an older one? I can see the pound notes migrating from my wallet even as I think about it!
Before I bought my present daily driver (SEAT IBIZA Ecomotive.) I nearly went for a Honda Jazz with the i-vtec engine. Honda's vtecs have been around for a long time now and their innovative variable valve control is well known and reliable. Mostly it is used to vary valve timing at higher revs to produce more power, and it does. The Jazz's i-vtec (the i standing for intelligent) is a little different though (think it's the same on the 1.8 Civic). The variable geometry is not employed at high revs. Medium to high revs cam profile doesn't alter. But at low revs, when the engine is under light load, the variable geometry is used to keep the inlet valve open way past Bottom Dead Centre. This allows inlet charge to be pumped back into the inlet manifold which greatly reduces the energy lost compressing a full charge. There is some clever stuff going on with the electronics in terms of throttle body control too I believe?
There are similarities here with engines which run according to the Atkinson Cycle which makes interesting reading. Miller cycle anyone? Once you start looking at this you won't believe how many weird and wonderful internal combustion engines people have thought up! - Makes a Wankel look positively mainstream!
Somewhere, in the Becky threads I think, we were talking about "dialing in" camshafts. If you Google 'Burton Power' and search "adjustable duplex cam sprocket set" you'll see examples of specially made sprockets which allow for variation between the position of the camshaft in relation to the sprocket teeth. A lot easier than hand filing up offset Woodruff keys as we used to!
