Whatever happened to the twin cam in block (pushrod) engine they were showing a couple of years ago?

 

Nothing, that is what happened to it. Its a shame too, it was a nice engine. Probably costs too much to build to justify it.

 

Why do you say that it was a shame? It did have some neat features, but it seemed too complicated -- wasn't it something like seven spinning shafts or something (maybe I'm thinking of a different engine).

I don't know, unless it had some important advantage over the VVT DOD Gen IV, I don't see the need for it.

Remember the W8 from Volkswagen? It was a nice engine too. But complicated and low on power . . . . Their new VR6 has more power, less fuel consumption, and is likely cheaper to build.

 

The XV8 was a 75° V8 and would easily have been made modular for a powerful V6. The 4.3L V8 equaled the 5.7 in hp and torque despite its smaller displacement and physical size. Also the XV8 had 3 valve cylinders, DI, and true VVT because it had separate intake and exhaust camshafts. XV8 may just have been what GM has up its sleeves should the current lineup of OHV V8s have a hard time keeping up with the OHC V8s in the future.

 

Do you want VVT to feel like a bad transmission?

I can't really feel the VVT on my Colorado either. I've driven CTS, TrailBlazers, BMW M3's with VVT and non of them "kicked". Although the M3's 333HP inline 6 did pick up a lot of steam on the high RPMs and was gutless below 3K

 

VVT doesn't 'kick in or our', it's always operating, changing the timing of the cams and valves.

To get compression ignition from regular gas, doesn't the compression ratio have to be in the 20's to 1, or somewhere insanely high?

 

Yeah, Honda's VTEC system "kicks in", because it not only varies the timing, but has a completely different cam lobe for high rpm. A standard VVT system just plays with timing through the rev range.

It would depend more on dynamic compression ratio, not static. You can get compression ignition (detonation) in a gasoline motor at a lower static compression ratio than that.

 

cool. Now I can put VTEC stickers on my new Camaro.

 

You are completely right from a business standpoint. It was a nice piece of engineering though, and I am not aware of any other engines that feature two cams in the block (there could be though). Having two camshafts in the block, one for intake and one for exhaust, would allow for full variable valve timing, as opposed to the system GM will be using that just advances or retards the timing based on rpm.