Ok, I wanted to know, how can I calculate effective CR a.k.a. dynamic CR, so I could get straight with my build, cause as I understand I need to select cam for CR, and Iam using zealautowerks calculator and there is a window Elevation - if I enter something there, then only changes effective CR, so, the question is, what I need to enter there, or, is there some other way to calculate effective CR? I am building D16Z6 N/A, and I need some help with these calculations, so please, help Thanks.

P.S. window - Elevation "Enter operating elevation of engine to determine effective compression ratio."

 

14.7 psi, 101 kPa, 29.92"Hg or 760mm Hg is sea level. It takes approx 2000' to raise that to 15.7psi. If your are under 2000' of elevation I would say put 14.7 psi in there and you should be good.

If it requires your elevation in feet. Than you would require a topographical map to see what elevation, in feet, that you will be operating your car. Elevation is a measure from sea level. What you need to know is how many feet above sea level the city/town, you will be driving in is.

For example I can tell you that I live 387 m (1270 ft) above sea level. So my elevation would be 1270ft.

The reason that the elevation changes your CR is because of air density. Depending on your elevation the density of air will change therefore changing the compression ratio. Heat and moisture also effect the airs density as well. A Barometer can help you out with that.

 

Ok, thanks for this info but what is that way to calculate dynamic CR with camshaft specs, like there was something about valve lift on intake or something if someone can, then I will be greatful for that info too

 

Effective compression ratio is the compression ratio measured at the point the intake valve closes. Dynamic compression ratio is not the same. It is basically effective compression ratio times volumetric efficiency (of which altitude would have an effect). It's not something you can easily measure, but it is not super important that you do. Determining BMEP (brake mean effective pressure) after you have it dyno'd will tell you if the engine is breathing efficiently.

To calculate effective compression ratio you need to measure the exact static compression ratio with a burette (an online compression ratio calculator is not accurate enough). You need to know exact stroke, rod length, and piston pin offset (if any). After that it's pretty basic trigonometry. I have a sheet at home with the formula's and will try to scan and post it tonight if I can. Most 4-valve Honda's can tolerate an effective compression ratio of about 8.5:1 without detonation (this is actually true whether it's a Honda, Ferrari, Toyota, etc.). 2-valve engines or engines with iron blocks and heads will be a little lower because they do not transfer heat as well, therefore you will run into detonation problems at that effective compression ratio.

 

It would be very nice if you could post that sheet up i would be thanful cause, Iam in progress buildin budged d16z6 N/A and I realy want to do it right So, all informative help is apreciated

 

http://www.zealautowerks.com/


http://www.dmperf.com/compression.htm

 

I know I'll have to explain this later but for now I am too tired. But here is a scan of a worksheet I did a few years back.