i.c engine valves retiming

I have an EGR,(exhaust gas recirculation), valve, even on my 1986 truck. I can't tell any significant help that it provides. It still burns a lot of gas.

More reading.

I suspect the EGR is just for reducing measurable emissions, like the old smog pumps. If I thought my computer would not get upset, I would block it off.

The catylitic converter is supposed to take care of unburnt fuel, so what does the EGR do? Maybe it's supposed to recycle unburnt fuel during wide-open-throttle moments.

http://en.wikipedia.org/wiki/Exhaust_gas_recirculation

I don't even know if mine works. It's a 1986 GMC with a 454 engine. If gas goes much higher, maybe I can donate it to the Smithsonian and take a tax write off.

Didn't some diesel engines have a 'scavenger' device, maybe a roots blower? You need to expect more power increase to compensate for the energy used to create the vacuum. I always wondered if airplane motors had ever used eductor devices on the exhaust pipe to scavenge the exhaust.

I'm hung up on "emitted to vacuum".

If you decrease the duration of the exhaust valve, you'll need a lot of vacuum to "result easier and faster combustion gases evacuation". Where that power comes from, I don't know.

Maybe it's just semantics.

Tuning the length of the exhaust pipe is one way to "emit . . to vacuum" (partial). Using this as an example, you can see that the whole setup of the combustion, the mixture, the intake pressure, spark timing, mixture gradient, peakiness of the power curve, and so forth, can be affected. There needs to be a good reason for the "vacuum" since it certainly will cost power as you suggest, though it can add power also.

The design elements need to be dealt with as synergistic partners.