Throttle-less VQ37 discussion

Waxhaw510

I'm an electrical engineer and formerly worked in the auto industry (tier 1, variable cam actuation), have done some tuning in the past, but am currently way out of my comfort zone with this latest idea and need the help of the forum subject matter experts.
This is for consideration of a new engine for my currently SR-powered '69 510.
It's my understanding that the VVEL on the VQ37 controls lift all the way to zero, and is therefore used for the majority of throttling duties during normal operation. I've read that the main throttle is only employed during traction control events or to boost vacuum for brake assist. This is similar to many other engines employing direct or indirect valve control, BMW, FORD, etc. Since my car has neither traction control or vacuum assisted brakes, how would I go about controlling the motor ONLY using the VVEL servos, with NO main throttle(s)? I can't imagine this would be possible using the stock ECU, maybe I'm wrong? If I built a manifold that feeds the six intake ports through a common MAFS I could run it with any stand-alone as long as I can work out the control signal going to the VVEL servos (CAN perhaps?). On the other hand, it would be so cool to just run individual bell mouth stacks directly to the head (how strange would that look?) but with no throttle speed density is out of the question I suppose. Maybe a new approach, mapping fueling 3D using VVEL position (vie position feedback, not the request signal), RPM and well, not sure what the 3rd air reference would be.
I guess the natural question is WHY? Not sure really, there are some slight response and efficiency benefits, but maybe just because it would be pretty novel to see 6 velocity stacks with injectors (maybe in a strange top-down arrangement) and no throttles.
Let me hear your thoughts, is there a way that this could work?

phunk

First figure out a way to get control of your VVEL, and then it should come pretty easy to eliminate the throttles (in theory at least. but there will be obstacles that might make it unfeasible). As of right now, there is no known EMS with direct VVEL support.

I believe that the throttles are active a lot more than you are thinking though. I only recall the vacuum gauge going dead when running at a steady load for a few moments. Any time the load changes, it seems to go back to throttles.

Who knows if the VVEL will be able to manage a stable idle on its own. And if not... then that is that, you are dead in the water with the throttle-less project

Speed density would be a real trick, but I think you could do it with some compensation tables based on VVEL position. I feel like tuning that would be a nightmare.

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gomer_110

While I'm no expert by any stretch, I would say the concept of what you want to do is viable. In reality though I think it's probably more of an undertaking than anyone outside of Nissan engineers are capable of. To date no one in the aftermarket to my knowledge has anyway of fully controlling the vvel system via tuning. Basically you'll have to reverse engineer the entire control system as very little data exists outside of Nissan about the actual electronic control of the system.

If you do go down this road, good luck. I'm sure there are some hardcore track guys on here that wouldn't mind being able to fully control vvel system. Personally, having the ability to essentially have a programmable camshaft has always intrigued me.

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Waxhaw510

Good point about idle. Without an IACV it will be difficult to modulate such a tiny amount of air. Darn, idle is always such a PITA.