Premium fuel?

So maybe I don't understand but...

How does forced induction work if it doesn't change/increase compression? Are they not related?

I mean if I'm driving my wife's Acura and the boost gauge is at zero wouldn't it have a lower compression then when the turbo boost is maxed?

 

A turbo is forcing air into the engine. Once that air is inside the cylinder of an engine it will always be compressed at a fixed ratio. The turbo just increases how much air and fuel are in the cylinder.

An engine is basically a fuel driven air pump. The more air you can get in and out of a motor the more power it will create. By force feeding air into the motor you push more out the motor which turns a turbine which forces more air into the motor. This is why turbos used to be laggy vs a mechanical driven air charger like a supercharger

 

I see.

So compression doesn't increase as the turbo forces more air into the cylinder?

Maybe pressure and compression aren't the same?

 

Cylinder pressure would increase with boost, theres more air and fuel in the cylinder but the difference between the piston being at bottom dead center and top dead center will always be the same whether turbo or not. This is what determines a compression ratio

 

Gotcha. Thanks

 

The VVT-iW effectively lowers the compression ratio. At its extreme (105* ABDC), about half of the intake air is pushed back out of the cylinder through the still open intake valve... this effectively gives about half the compression ratio.

 

Better to say it drops the cylinder pressure, than drops the compression ratio. The compression ratio is still fixed.

 

I don't know... seems like a gray area that is not helpful to split hairs about... which is why I was careful to say "effective" compression ratio.

Whatever helps people to better understand.

 

Except that it is not splitting hairs. Compression ratio for most engines is an absolutely fixed thing, the ratio between volume at bottom dead center and volume at top dead center. Or ratio of maximum to minimum volume.

A wide cam timing changes the cylinder pressure while the compression ratio stays the same.

"...this effectively gives about half the cylinder pressure" is more accurate and helps people understand better also.

 

I'm at 4800' and so regular is 85. Never had an issue. The only time I put in higher octane fuel is when I'm driving down to 2000' on the same tank of gas while pulling a trailer and I'm probably wasting money doing that. It's a little insurance against pinging when going up over mountain passes. The education of many here on what octane does and why we don't need it in our Tacomas is surprising. The cost of premium over regular negates any perceived mileage improvement.

 

Static...

 

@Dannyblues

Thanks,

Levees weren't the problem. I'm not sure they would directly effect me if they did fail. Our flooding was due to rain water not being able to drain fast enough after 30 inches of rain were dropped over a weekend. That kind of weather can get most anyone. The radar looked like a giant slow turning hurricane..... it just picked up moisture over the gulf and dropped it here..... Something like 60K+ homes were affected. I was lucky to only have 6 inches in the house.

 

Costco advertises that it is toptier. Been buying it since prices were high.... Been paying ~$1.80 for months now. I paid $1.75 back in 2000!

I live in Louisiana. It gets pretty humid here. I still don't have problems. Might be because my lawn equipment lives in a little shed and it gets pretty warm in there. Likely cooks the moisture out.

Automotive systems are sealed much better and is likely why they don't have problems.

 

They may not be exactly the same engine. Same architecture, but likely different details besides the tune. Different CR, Injectors, Cam Profiles.... dunno. All 350 cu in small block Chevrolets aren't the same.

 

There have been quite a few improvements that allow higher compression with lower octane fuels. A big one has been the switch to aluminum cylinder heads and blocks which remove heat quicker reducing the likelihood for detonation. Combustion chamber designs, fuel injection.... additionally, changes in cam designs can allow for some pressure bleed off that while maintaining a high CR, the actual cylinder pressure is less. Variable Valve Timing, Variable Injection Timing, Infinitely Variable Ignition Timing...... Engine design got better since 1955.

 

Yes Dynamic Compression Ratio could be used if that makes it easier for people to understand.

 

That's incredible! I think I and most people forget we live on a planet in space. Things happen to planets and much worse than the earth.

30 inches over the weekend!!! Here 2 inches in 24 inches is a lot!!! We have a brook along our property line. It drains under the road into a marsh and woods across the street. We've had rains where it floods the front yard half way across then spills over the steet into the marsh. But never anything like 30 inches. I can't imagine what that looks like or must sound like plus with tornado possibility with that huge thunderstor. I think it was 12 years ago, as I was told we even had an inland tornado in Danbury Connecticut about 20 miles or less from here. It's pretty forested and hilly here and we are pretty far inland from the icy Atlantic. Not the formula for tornadoes but we do get big storms in October. I wish you the best of luck. Your area is so cool. But has become unpredictable since global wierding. That's what I call it. Weather everywhere on earth has gone crazy. Dannyblues

 

I think you are probably right. Even a cam can change everything. I was just hoping a flash I think they call it of the ECU or a different tune or change of the ECU would change everything and I'd get the maximum power. ( but I don't want to be shifting my manual at 6,000 rpm around town!). Dannyblues

 

Agree here. Especially if you are an NE US citizen. Mileage goes down with E85 or more

 

Yes they have. This ain't 1955 anymore. Ed Sullivan is dead. The Beatles still living are old men. Yes I've heard of the engine variables that don't produce a static compression ratio. But all this high tech stuff has left me behind. Glad I still have my 88 Harley superglide and 87 Chevy Nova with 1.6 Toyota engine and drivetrain. Otherwise I'd have to sell all the tools in my big roll away.
Anybody need an open end wrench that came with the 1919 Ford model t or a brake spring tool for drum brakes or an entire brand new set of flare nut wrenches??? Dannyblues