yea but real question is what about in the passenger car market.

 

damn this thread blew up on me, Doesn't the vg (sohc) have hydrolic lifters which don't require rockers? I always thought the vg was tuned for low to mid range torque. If nissan wanted a high end monster they would have stuck a hotter cam with tighter valve springs (the maxima is a everyday car that needs everyday torque so it would make sense that it has the low to mid punch). It seems like major advantage of dohc is the ability to have different timing on the exhaust or intake and increased flow (which translates into more high end but less low end) due to more valve area. sohc are more reliable and produce better low end due to their restrition on air flow. Also i don't see any reason why sohc can't rev high with the correct head and pistons. Correct me if im wrong, please.

 

They have some seriously kick-butt diesel cars in the European market. Good performance, and awesome fuel mileage. The only thing stopping them from coming to the US is the lack of low-sulfur diesel fuel here.

 

Tell that to Honda

You can have a SOHC 4-valve engine. All of the current Honda/Acura V6 VTEC engines (except NSX) are SOHC 4-valvers. SOHC engines can only vary timing with different lobes, though. Or it could also be done with a system like Porsche's VarioCam, which uses one lobe with different amounts of lift and duration from one end of the lobe to the other. The cam is then shifted longitudinally in the engine. This is one of the most advanced variable timing systems out there. But you're right, with the conventional phase shift valve timing, you need separate cams for both intake and exhaust valves.

Limited to only 3rd Gen's, yes, the SOHC VG is more reliable than the DOHC VE, but it has nothing to do with the fact that the VG is DOHC. The VQ engine is very tough and reliable and it's DOHC.

I think that's more of a tuning issue, and not directly related to cam arrangement. Cam PROFILES have a lot to do with that, but being SOHC or DOHC is more just a side point, I think.


If the SOHC engine design has lighter hydrualic lifters instead of rockers, then it could rev just as high as a DOHC, since rev ceiling is mostly limited to overall valvetrain mass and where valves start to float. I'm not familiar with how the VG engine is designed, though, so I can't really comment specifically.