2 Questions

[Anonymous]

Hey,
A recent post prompted this question. How mush psi can a head take?
If a head runs 10 to 1 compression and compression is measures in atmosphers and 1 atm is like 14.7 psi then it should be around 147 psi. If I wanted to hold the volves in with compressed air I shouldnt really even have to consider how much psi I use cause I dont have a compressor anywhere close.

My second question is, since liquid is not compressable, would the compression change any on an engine tested without fuel added versus one with?
Thanks
Paul

 

[80broncoman]

The highest compression ratio I ever heard of is the IDI diesels like
the 5.7 olds and 6.9 and 7.3 IH. I belive the figure i heard was 22.5 to 1.
Hope this is a help,
Jim

 

[80broncoman]

I missed your 2nd question and since i cant edit here i am once more.
since at operating temp the ratio of fuel to air is around 14.7 parts air to 1 part fuel i dont think it would effect very much at all.
Jim

 

[Anonymous]

I am sure the head can take quite a bit of pressure, but I do not have any specifics. The pressure of 147 psia you quoted would only be from static compression ratio. Now consider that there is heat and combustion occuring in the cylinder and the peak pressure is much higher.
Doug

 

[J.R.]

VW 1.5L n.a. diesel = 23.5:1. 1.6L units were a little lower.

J.R.