cylinder deactivation

[bigblockfiero]

Nothing new here? Well not really.

Cylinder deactivation has always been found on very low output engines in part to the complexity of the moving parts. When a valve is closed with a hydrolic lifter system the lash is tight but the actuator type mechanism needs to pull out a slide plate to disable the valve. kindof like pulling a table cloth out from under some dishes without moving them from there placement on the table. putting the table cloth back gets a little harder because you need some clearance to pass the cloth back again. The problem is that you need quite a bit of clearence. In any deactivation system there is a pushrod pre loading spring that lifts the pushrod to create the clearance nessesary for the switch.

Imagine this as a pushrod rev kit that is installed upsidedown, pushing the pushrod up, but not enough to open the valve.

So any way, when you are running on all eight cylinders this clearence issue is available but not being used but it robs the engine of valve lift to the effect of about .025 - .030 lash. The cam openning rates have to be much more mild otherwise the opening ramp will smack hard into the lifter.

This is the way it has always been untill gas prices started hurting the hotrod community.So me and david vizard have taken this a step farther by incorporating a stepped base circle cam. How this works is that for a moment wile the valve is closed the base circle steps away then back again and in doing so it lashes the valvetrain tight just before the ramp arrives. This then allows the same aggressive cams as before with no detriment whatsoever. The prototype setup in the fiero has 1.7 roller rockers and some understrength parts to find the design limitations within the system. I have had no flexing whatsoever and no failures so when we go to the full strength parts we will for sure have this threashhold of overdesign.

All has been progressing well so the setup now is nearing its marketing stage for the small block chevy but a few problems have come up. A tendancy to kill on smaller engines with big cams while in four cylinder mode. One solution for now is an earlier intake closing (as on the prototype now) but for those pushing their motors over five grand which is about everybody the solution is a simple combustion chamber modification that also smooths out the rough idle down to even 500rpms and all the wile increasing gas meilage and efficiency even further. Anyone that choses to optout of removing there heads will instead cut their plenum divider just a tad to borrow air to the other plenum side.

Enough about the valves and engine, the other part of your question was fuel management. very simple, open the circuit to two injectors on each side of the batch as not to fully load one side wile the other is doing nothing.

People sometimes ask about the possibility of letting the valves run and just killing some injectors. The answer to that is that the gas meilage would suffer significantly along with a lot of other problems. If air is alowed to move thru the dead cylinder it will cool real quick and also pull down the entire block temp.