Quote:
Originally Posted by arpad_m
The differences are minuscule. The LT6 makes more horsepower mostly because it revs so high, its torque is practically the same as that of the LT1. Fuel economy on the C8 Z06 is the same (base) or worse (Z07) than with the supercharged(!) Camaro ZL1, despite the car weighing 4-500 pounds less. I could not find precise emissions information, so I will not comment on the "runs cleaner" part.
I don't think that is anything to write home about this DOHC in terms of power or fuel economy. It is definitely better and more innovative in some ways, but not by much.
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You’re using an extreme case of a DOHC engine. An NA fpc DOHC engine is always going to burn more gas than a higher displacement ovh engine or a lower revving DOHC engine. Always has, always will. Ferraris are much lighter than Camaros and mustangs but their mpgs are atrocious when comparing the two (unless you bring the gt350 into play). That being said the issue at hand is emissions, not necessarily mpg. Getting a high displacement ovh engine (remember displacement has to be high in order for a pushrod engine to make any type of power) to pass cold start emissions is a tough task. While I can’t prove this, there was a rumor that the reason the supercharged LT4 even exists is because Chevy wanted the c7 z06 to be NA but they couldn’t pass cold start emissions while making the power they were targeting via a traditional high displacement ovh engine. I feel like this rumor is true and that’s why the LT6 exists in its current configuration.
The other reason why GM might make DOHC engines is because of displacement taxes on cars in Europe. While I believe these taxes to be BS because of the mpg being the same as smaller displacement DOHC engines (as you sort of brought up) I’m sure these taxes can deter purchases of GM commercial vehicles there.
By the way, I’m not a DOHC fan. If I was, I’d have bought a mustang, not a camaro. Just stating what I believe to be fact about cold start emissions and why GM might make a switch (even though I think it’s silly to invest in an architecture change for literally only 12 years).