Belgian1979 wrote: ↑
Sat Jan 13, 2018 2:33 am
There is no use at overfueling at WOT. At WOT, unless too high static CR or incorrect ignition timing to begin with, you have less chance of knock. In fact too much fuel creates less power.
In a turbo engine you would regularly see 11/1 AFR due to the fuel being used as a means to cool the combustion chamber and prevent the onset of knock.
Production engines typically do have compression ratios higher than what would be best for WOT, in order to gain more efficiency at idle and part throttle. Engines spend 99-100% of their lives at idle ad part throttle.
They aren't terribly concerned about losing a few percent power at WOT as much as they are concerned about keeping the catalysts from melting down (100,000-150,000 mile warranty, required). There are some new engines that don't go into PE *at all* because they are able to keep the engine and catalysts sufficiently cool via other means. This is quite a trick because modern practice is to attach the catalysts directly to the head, or turbocharger outlet, in order to maximize the heat they get to minimize the time required for them to light off. Once the cat is lit off, exhaust is typically cleaner than the air going IN to the engine, so the only way to make cars "cleaner" is to light the cat off more quickly.
I see modern gasoline engined cars blowing soot most mornings. My morning commute has me take a curving uphill on-ramp to our friendly local Interstate, and the merge is uphill, and the road after the merge is uphill. You go balls-out, or you block traffic. Most people choose to block traffic, some bolt the throttle to the floor and race to get out of everyones' way. That's when you see a little soot blown out the pipes, if you're paying attention.
My new car has only 8.5:1 compression because Volvo designed it to operate at WOT and 15 pounds of boost basically forever. To this end, it does NOT have a close coupled cat, and cold economy is horrifically bad in their attempts to get it to light off quickly. On the other hand, I can accelerate up that onramp, through the curve, and be traveling at over 80mph by the time I can start to see the traffic I will have to merge into
My previous record is 70mph in a car with much better power/weight, but no all wheel drive or active handling...