One of the most drastic changes ever was between model years 1971 and 1972, had a brand new EPA, leaded gas time was coming to an end with this new unleaded gas. Major problem with it, its combustion chamber temperature increased from 2,100 *F to over 2,600, so an EGR valve had to be added that actually pumped in exhaust gas into the combustion chamber to add more cooling to the combustion chamber.
If you would bypass it, would quickly burn up your exhaust valves and get holes in your pistons, can't take that heat. Other factor was adding a catalytic converter, more exhaust gas restriction. As only low octane unleaded gas was available, the compression ratio had to be decreased from 10.5:1 down to 8.5.
The decrease in performance was not too noticeable, Nixon by an executive order decreased the speed limits from 70 mph down to 55.
If the price of unleaded gas jumping from about to 30 cents per gallon up to 75 cents per gallon, could still buy unleaded, but that increased to $1.55 per gallon.
At that time, had my beloved 1970 Buick Riviera, required high octane leaded gas, 87 would cause severe detonation in that 455 CID engine. With EGR as high as 30%, that made that 455 engine more like a 318, but what the hail, still could do 55 mph.
Car became worthless, so I could keep and drive it, had to buy Canadian head gaskets, that did drop the CR down to 9:1, Canada never had high octane fuel, they were rather fat head gaskets. So I could burn unleaded, was lucky, went to my wrecking yard when I could walk back in there with my own tools, can't do this anymore. Found a 72 Buick with the EGR, removed the entire intake manifold with the carb and the EGR valve and got it for ten bucks. Won't let you do this today anymore, have to buy the entire engine.
While this car had factory dual exhaust, was not required by law to add the cats, back then would have been at least another 500 bucks. So was able to get my use out of that car poking along at 55 mph. Fuel economy did suffer, in good tune at 70 mph, averaged 20 mpg, at 55, and these required mods, below the peak torque value of that engine, best I could do was 16-17 mpg.
Screw you Nixon, hate your guts. But this was not the only problem besides paying $1.55 for high octane leaded. Practically overnight, all the full service gas stations disappeared and replaced with convenience stores! You could no longer stop to get a flat tire repaired or even air, but you sure could buy a case of beer. Bet not too many on this board even know what a full service gas station was like.
Getting back to the Cruze, the better way for EGR is to close the exhaust gas valves early to leave that mess from the previous cycle and does have variable valve timing.
What they could do is to change the firmware to keep those exhaust valves opened longer to get rid of that burnt up fuel, but just to get a short burst of power for a very short duration as not to put holes in your pistons nor burn up you exhaust valves. EPA's concern is excess NOx production by doing this, but they are not the least concerned if you toast your engine, so they never talk about this fact of life, just excess NOx production. We recently learned VW was doing this, in deep trouble now.
But there are other ways to pick up around 5 extra HP, turn off most of your electrical and in particular you AC if its on, this decreases the load on that little 1.4 L engine from both the AC compressor and the alternator.
But why did you buy a Cruze for anyway? Our key reason, fairly comfortable car, fun to drive, but most important, fuel economy. Since we purchased ours, had to pay as much as $4.55 per gallon due to some minor pipeline leak in Janesville, WI.
Without a vehicle, for earning a living, taking our kids to school, getting groceries, even a vacation, we are helpless. They got us where they want us.
