My '03 Frontier SC is supposed to use premium gas. What is the compression ratio on this engine? What happens if I burn regular? The recommendation says something about best performance but what does that mean?
I just put some regular in it today. I know if I put anything other than premium in my 440 Charger I get predetonation and eventual piston damage.
Glenn
It seemed you have already understanded the consequence in your last sentence. You know engine knocking is very bad for a car. Even the ECM automaticly retard the ignition timing in order to prevent knocking, but your vehicle perfomance would suffer, such as fuel economy, acceleration ability, etc. So, you'd better use what user's manual say.
Alan
Any idea what the compression ratio is?
Glenn
10.5 to 1. It has a knock sensor so damage won't be done, but you'll lose power and efficiency. You'll likely lose enough MPG to negate the cheaper price of the gas.
It will also cause your supercharger to stop functioning which totally wrecks your performance.
Ok. Thanks to all.
Glenn
FYI - if your motor is supercharged, your effective compression ratio is much higher than the spec.
I assumed that the spec given was the combined.
Glenn
Just found the CR at
Displacement: 3.3 liters Number of Cylinders: 6 Fuel Type: Supercharged Camshaft Type: SOHC Compression Ratio: 8.9:1 Horsepower: 210 @4800rpm Torque (ft-lbs.):
4.36 axle ratio MPG (City/Highway): 15/18
I assumed otherwise - that it's the mechanical spec. Interesting question. Ballpark wise I'd think that the supercharged spec would have to be much higher than that. Lemme check my facts and return since we're ass-u-me-ing.
I just figured that pump premium is only good to about 10.5. More assumming.
Glenn
Yeah... and my research tells me that the compression ratio is always the straight mechanical ratio. Although the density of the charge will be increased by a super/turbo charger, it's not typically measured in that manner. You can value it either as a increase in effective volume and/or an increase in effective compression but it's not a linear relationship and it's not part of any released specification.
That said, a super or turbo charged engine is always more susceptible to knock that a N-A - or so the philosophy goes.
For a given bhp output the mass air flow required is about the same for all engines. But as power = plan [1] the cylinder pressure is much higher to obtain the same power from a smaller engine. It's the increased cylinder pressure that requires the higher octane rating. Also having gone though a compressor on a super or turbo charger the intake air is hotter - again requiring a higher octane rating.
[1] plan = mean effective cylinder pressure x piston area x stroke x cycles per sec-- Peter Hill Spamtrap reply domain as per NNTP-Posting-Host in header Can of worms - what every fisherman wants. Can of worms - what every PC owner gets!
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