Quote:
Originally Posted by freebeard
Expensive and touchy—detonation, or the rear wheels re-contacting the ground, can re-index the crank on the fly. People TIG weld the parts together and break the welds. In a car with EFI, that keeps the wheels on the ground and isn't drag raced, they should survive.
But as a development platform it would be serviceable and much less expensive than Scuderi's approach. The offset between the compression and ignition cylinder is reported vaguely as somewhere around 15-22°. Once that is locked down, your 3D printed sintered-metal part with integrated roller bearings can be created.
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You're getting a bit obtuse there.
If I understand what is being done with the Scuderi principle, they're separating the compression and expansion cycles. With that done, the compression and expansion ratios can be asymmetric.
It's fairly simple, at least in principle, but not really practical to DIY (at least not without a machine shop).
If we accept that the bottom end, including CR, has to remain the same, what can be done and what is the best approach?
Simply disabling 3 cylinders will help fuel economy due to the reduction in pumping loss. You could do that with minimal changes to the engine management (although you might have to increase the idle speed). The penalty is the maximum power output of the engine is less than will be required at times.
The question then is; How do you regain the extra power when it is required? It might be possible, as per stovie's original idea, to convert the 3 "spare" cylinders into an air powered motor. Unfortunately, the extra power available and most critically, the total energy available, is likely to be quite low. (How many hills do you have to climb?)
You could instead, use the 3 "spare" cylinders as a compressor and feed stored (tank) high pressure air into the inlet manifold - I'm thinking air ejector - and supercharge the 3 working cylinders when the extra power is needed. Accurate control of the extra air may be an issue.
It would require engine management changes. I think the Jeep uses a MAP sensor. There are (2 and 3 Bar) MAP sensors around if the engine management can be rewritten (or swapped) to suit.
There may still be insufficient air available, even with pre-charging of the tank(s). I gather that is one reason why the Swiss engine uses a turbocharger. It may just be that most people aren't prepared (nor able) to charge up tanks of air.
Intercooling could be near perfect with sufficient heat exchange (maybe just long pipes between the engine and storage) from the compressed air to the atmosphere. Even better than 100% with expansion occurring in the inlet manifold.