Page 1 of 1

p6 compression ???

Posted: Wed Dec 02, 2015 6:06 pm
by scoobyjim
Is 250psi correct?

Re: p6 compression ???

Posted: Sun Dec 06, 2015 12:32 pm
by Emiel
Hi,

Although I'm not familiar with the p6 engine I suppose 250 psi is far to less. Is approx 17 bar. A sound diesel should be round 25.

Try to find out where your compression goes away. Leaking valves is not a too difficult job and cures a lot sometimes.

Rgds Emiel

Re: p6 compression ???

Posted: Thu Dec 10, 2015 5:56 am
by BarryM
Compression:- 380 to 450 lbs. sq. in. Variation not more than 15 lbs. sq. in. Compression of 350 is satisfactory providing variation is within range.

Re: p6 compression ???

Posted: Fri Dec 11, 2015 10:29 pm
by scoobyjim
What happened to compression ratio x atmospheric pressure= compression. Which works out at 238 psi .

Re: p6 compression ???

Posted: Sat Dec 12, 2015 1:20 am
by oehrick
I'd not thought of it that way before scoobyjim, but having riffled up the compression ratio for the E1a engine at 16:1, have second checked it as correct, (if you disregard the fact that the starting pressure will inevitably be somewhat lower than 1 atmosphere). According to the P6 handbook linked below the P6 is 16.5:1 so around 245 psi

To counterbalance that, the inertia in most mechanical pressure gauges may cause them to over read peak pressure, unless oil damped, in which case it may underread :scratchhead:


http://www.fordsonmajor.se/pdf/perkp.pdf may not help much but if you google I'll bet there is a manual for the P6 somewhere.

Happy hunting

Re: p6 compression ???

Posted: Sat Dec 12, 2015 9:57 pm
by scoobyjim
Got the manual but there is no mention of compression.

Re: p6 compression ???

Posted: Sat Dec 12, 2015 11:41 pm
by oehrick
Page 39, settings & data, 6th line down - I assumed those items common to P3, 4, 6 are the lines with a single entry ??

Re: p6 compression ???

Posted: Sun Dec 13, 2015 1:05 pm
by scoobyjim
Yes so using the 16.5:1 all we can do is the formula mentioned above which =250

Re: p6 compression ???

Posted: Sun Dec 13, 2015 2:25 pm
by oehrick
We're missing something important like pressure rise due to the compression increasing temperature (Boyles Law / Charles Law ? :scratchhead:) assuming test gauge is in the injector port there's no pump / injector influence responsible.

With the reduction in volume there is a temperature rise which just using the compression ratio doesn't factor in, as that assumes constant temperature

C'mon Emiel & Barry, put us out of our misery please, are we looking in the right direction, is there a constant or fudge factor which can be applied to the Comp Ratio to calculate the sort of peak pressures that will give an ignition temperature* or are you using figures based on practical experience of this sort of engine ?

*Can't find a pressure value but ignition temp seems to be about 480-500K or 207-227C