Dynamic Compression Ratio

[bratcop]

Everyone here probably knows this already, but I am finding alot of information stating that Dynamic Compression Ratio (DCR) is more important in driveability (with respect to knocking) than Static Compression Ratio. Of the articles I have read, it sounds like 8.25:1 DCR is what to shoot for. With quench between .035 and .045, it seems that the experts believe it would run on pump gas (89 octane-ish). Here are a few articles. It is almost like, to a certain degree, static compression is disregarded (except for cylinder psi). What do the experts here think?

Some of the articles...

http://www.empirenet.com/pkelley2/DynamicCR.html

already posted in another thread, but still on point...
http://fourwheeler.automotive.com/20026 ... atios.html


I hope I am not belaboring a point, more knowledge is always a good thing, I think.

Joel

[Mgardiner1]

You are on the right track. I'm running a DCR of 8.20 and a quench of .057. I haven't tried anything other then premium (93) as i only have 75 miles on my stroker. I plan to to switch to 89 and then to 87 to see if it will run on the lower grade. So far i have no pinging problems

[Flash]

Everyone here probably knows this already, but I am finding alot of information stating that Dynamic Compression Ratio (DCR) is more important in driveability (with respect to knocking) than Static Compression Ratio. Of the articles I have read, it sounds like 8.25:1 DCR is what to shoot for. With quench between .035 and .045, it seems that the experts believe it would run on pump gas (89 octane-ish). Here are a few articles. It is almost like, to a certain degree, static compression is disregarded (except for cylinder psi). What do the experts here think?

Some of the articles...

http://www.empirenet.com/pkelley2/DynamicCR.html

already posted in another thread, but still on point...
http://fourwheeler.automotive.com/20026 ... atios.html


I hope I am not belaboring a point, more knowledge is always a good thing, I think.

Joel

Yup,
http://www.empirenet.com/pkelley2/DynamicCR.html
Is were i down loaded my Favorite DCR calculator

Flash

[oletshot]

SCR is a nice number to put in your signature.

It does give a reference point to work with when planning your build. You know you need more work in the combustion area if your at 10:1 and plan on running 87 octane, no cam that will help you there. How do you use it to calculate cylinder pressure if the valve is open?

[bratcop]

Regarding the CR calculator on this site...I am using it to determine my numbers...liking what I see, but I am curious as to how a dual pattern cam will affect my DCR. The calculator says it is for just a single pattern cam...Will using the stock Dual Pattern Cam from an 01 HO 4.0 change my DCR and if so, which way will the DCR go, up or down? I have been researching this, but can't seem to find a clear, understandable answer...

Also, saw something about polishing and coating intake valves with a heat reflective coating to reduce heat transfer to intake charge (intake air) thereby reducing temps in the combustion chamber and reduce detonation. Anyone know what this coating would be? Is it similiar to a ceramic coating? Something I would like to consider to stave off detonation...


here is the article...very informative regarding higher compression engines...

http://www.popularhotrodding.com/tech/0 ... index.html
Bratcop

[Mgardiner1]

I think with both single and dual pattern cams, the crucial number is the degree of rotation after bottom dead center that the intake valve closes. Compression starts when the intake valve closes, so the exhaust valve (other pattern) should have no effect on it. IVC is spec that will help you determine your DCR