Thread: Compression pressure reading on series 2 TD5

Originally Posted by Marnie

Does any one know what the cylinder compression pressure reading should be on a TD5.

Marnie.

According to the handbook it should be 19.5:1

To calculate the actual pressure you need all the dimensions from the cylinder.

CR calculator is here: http://www.csgnetwork.com/compcalc.html

Lots of different info can be found here as well. Keep you amused for hours
http://www.martindalecenter.com/Calc...s1_3_Auto.html

IIRC, Rave will list the acceptable cylinder pressure range in the service docs. Guesstimatically..... (similar to equivalate )around the 270-290 psi would be about right for 19.5:1.

Andrew


I am not a moderator, I am a human being!!!

From memory.

same compression ratio as a tdi so about 400psi as absolute realistic max at cranking speed. anything over 300 is workable 300-320 is ok, 320-350 is good 350+ is great.

remember to disconnect the injector harness and test by manually activating the start with the box in neutral AND the ignition off.


19.5 x14.7 (compression x atmospheric pressure) = 280(near enough)

280*1.4 (pressure x the adabatic pressure increase value of a gas under pressure for normal air) = 400psi (near enough)

heres the logic...

your basic pressure increase is the compression ratio x atmospheric pressure. because when you compress a gas it gets hot if you increase the temperature of a gas in a fixed volume its pressure also increases.

(theres a fixed rate that that happens at and uber smart labcoat wearers worked it out for us and for normal air at atmospheric pressure a factor of 1.4 is about right till you get to the kinds of pressures that cause the individual gasses to condense to liquid.)

given the high pressures you're dealing with be carefull with the gauge and rememeber to crank over the same number of times for each cylinder.

the only real test I have for the #5 pot is a rough comparitive test put the glow plug back in pot 1 and crank the engine over by hand using a spring scale on the spanner you use. the torque and degrees of rotation required to advance the pots from BDC on compression to the point where it "stalls" the spanner should be the same for both pots.

Originally Posted by Blknight.aus

From memory.


the only real test I have for the #5 pot is a rough comparitive test put the glow plug back in pot 1 and crank the engine over by hand using a spring scale on the spanner you use. the torque and degrees of rotation required to advance the pots from BDC on compression to the point where it "stalls" the spanner should be the same for both pots.

I saw a photo some where of of a gauge the went where the injectors go, it looked to be home made


That would let you test all 5 pots.