dresden_k

I searched and searched and searched some more and I'm out of energy. Didn't find satisfactory answers to these remaining questions..

1.) What exactly are the numbers in a compression ratio representing? I know that lower, like around 9:1 is good for turbos, but I don't know why. Is there a difference in fuel mileage the higher one's compression ratio goes? Is it directly related to horsepower?

2.) What is offset all about on a wheel? What do Hondas usually set their offset too and what are the effects of changing the offset with a different set of wheels?

3.) Why are most aftermarket pistons aluminum? To reduce reciprocating mass?

4.) I know that turbos use exhaust gasses and superchargers use engine driven belts, but what are the other differences? Is it true that superchargers have a narrower operable RPM range?

5.) What would be involved putting a Prelude steering rack w/ speed sensitve steering in a 4th gen Accord?

6.) Why do race calipers have more pistons?

7.) If I put a stiffer rear sway bar in my car, I understand that I will reduce understeer. Am I doing this by increasing the tendancy of my car to oversteer?

8.) Is it possible to build up a H22 to take a decent turbo and still have the engine last for 5+ years?

Please, no flames. I realize I'm lookin' noob here. Trying to be less so.

Thanks for your help and patience.


:thumbup:

Gasoline Fumes

I'll answer a few.

1.) Compression ratio is how much the air/fuel mixture is compressed by the piston. So an engine with a 9:1 ratio would compress the mixture 9 times what is was before entering the cylinder.

2.) Offset is the distance between the centerline of the wheel and the mounting surface.

3.) Stock pistons are aluminum too. But aftermarket pistons that are forged will be stronger.

6.) I think it's to get the squeezing pressure more even acroos the pads.

7.) Yes, it will slightly reduce the grip of the rear tires when turning.

qtiger

The ratio by which air is compressed in the engine. With a 10:1 compression ratio, your engine would compress (random, easy numbers) 10 cubic feet of air into 1 cubic foot of air.

Lower is good for turbos because you're forcing hot, precompressed (by the turbo) air into the cylinder. A low CR gives more leeway in tuning than high. You can easily crank up the boost to increase cylinder pressures. Decreasing is another matter.

Offset determines how far the centerline of the wheel is from back side of the hub. Stolen illustration:



The page it came from has a more thorough description as well.
http://www.tirerack.com/wheels/tech/offset.htm

Typical numbers for Hondas vary depending on wheel and tire size (smaller has more leeway). Civic platform cars are usually around +38mm to +45mm.

I think primarily because aluminum alloys are so versatile.

This is rather hard to define simply because there are many forms of supercharger, each with its own qualities. For example, a centrifugal supercharger like Vortech's operates almost exactly the same as a turbocharger. (Except crappier)

In addition, there are so many sizes and types of turbochargers available that you can achieve almost any result with the right setup.

Not entirely sure, but I have a feeling it would be a huge PITA.

Allows use of a larger pad, which distributes pressure over a larger area of rotor.

Yes.

Easily. It just costs a bit more money. In my experience, most turbo related problems on cars which were not OEM turboed are caused because the car's owner cheaped out on fuel management and/or tuning.

dresden_k

Wow... descriptive. Thanks qtiger and Gasoline Fumes...

So if I had, let's say a +100mm offset on my theoretical Civic, what would be the result? -100mm?

qtiger

The result would be 50mm of wheel not fitting on the car.


100 mm = ~ 4inches. Given that stock wheels are less than 7 inches wide, the hub would actually stick out past the entire wheel.

dresden_k

lol

Thanks.