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Bigsi15
Thursday 21st June 2018, 16:29
Guys is it normal to have the same numbers on a compression test when cold compared to when hot?? I always thought cold should be lower as the rings need heat to expand and seal correctly!

Test was done with throttle wide open all plugs out etc. It’s a 850 t5 with a rebuilt engine and I get 150 across all cylinders

Thanks

960kg
Thursday 21st June 2018, 21:10
Although some state hot when doing compressions it is REALLY all relative.......when cooled off all the clearances will alter correspondingly.

I would say cooler is better for a more accurate reading as when hot the number one cylinder always runs cooler thanks to it being nearer the water pump?

So long as the figures are within 29psi than all is well.

Bigsi15
Thursday 21st June 2018, 22:16
Thanks helpful to know :) it’s a pretty new build so hopefully pretty tight still! Certainly starts and runs ok