Aftermarket exhaust cam?

Phimosis

Based on the complexity and purpose of the VVEL, it seems very unlikely that the intake valve timing is the limiting part of the air flow through the VQ37VHR. The intake valve timing is likely adequate to the 8,000 rpm range where lightly modded vq37's reach. The maximum valve lift may limit the ammount of torque, and therefore power that the engine makes but it looks like that can be adjusted with the clevis pin in the rocker-foot linkage. Although Nissan tells you not to and that the heads have to be replaced if someone fiddles with this.....but after all.... someone fiddle with it to get it assembled correctly at the factory. If this all sounds like Greek, watch the video below.



In any event, VQ37VRH's with bolt-on's make peak power at 7,000 rpm. I can't imaging that the stock, single profile exhast cam is designed to make power any higher than that. So, chances are that the exhaust cam duration is what causes the VQ37VHR's torque curve to start falling off after 6,000 rpm and that it was designed this way to meet emission requirements. The broad turque curve and slow rate of fall off of the torque curve at high rpm suggests the exhaust cam has a large lobe seperation angle (LSA), although technically there is no lobe seperation since there isn't a true intake cam. Regaldless, it implies that the exhaust valve opens late.

An after market exhaust cam with either 1) earlier exhaust valve opening (lower LSA), 2) more valve lift, 3) longer exahaust valve duration or 4) a combination of those factors, would make more peak torque and more peak power as well as peak power at a higher rpm, all at the expense of emissions compliance and low rpm driveability.

I haven't heard any posts on this topic or even any rumors. It seems like there would be a market for such an item for people wanting more performance, especially those comtemplating track use or forced induction since the pressurized intake overcomes many of the intake limitations and makes the exhaust limitations that much more severe.

Any feedback? Ideas? Anyone think my logic is wrong? Just curious what else we can squeeze out of the VQ37VHR without going to a complete engine rebuild.

-Phim