Crank pressure test?

[DaveM]

Anyone know what crank pressure tests show?

Mate had an AA check done on a 3.0td Surf and had the following results.

CP Idle 30-40 L/min
CP Idle 50-60 L/min

Just unsure if these are good.


Cheers,
Dave

[wopass]

crank pressure test??

[vvega]

interesting test ....
pressure in normally measured in psi or kpa .. becaue this is a measurement of pressure

l/min is normally a measure of flow

can you clarify :d

[DaveM]

Will ask him again today, but I've never heard of this before

[smurf182]

Sounds to me like a measurement of how much gas is getting past the rings into the crankcase.

[SMOKEY]

This to me sounds like an engine blow by test, when Komat'su and CAT are doing there tests on our Loaders they have a gauge they fit to the crankcase breather that measures blow by, I haven't seen the result sheet to see how it is measured but Lt/Min would sound right. I know that even on new engines the figures are quite high.

FITZY.

[DaveM]

Yeah, can only think of measuring blowby, just not sure what is a "good" result is

[vvega]

How Much Blowby Is Normal for an Engine?
How much blowby is normal? Dividing an engine�s maximum horsepower output by 50 will give you a ballpark number for how much blowby you would normally expect to see. For example, a street performance engine that makes around 500 horsepower will typically have about 10 cfm of blowby with conventional pistons rings and ring end gap tolerances. Higher performance engines that are built to tighter tolerances will usually have less blowby, as might those with gapless piston rings. An 800 to 900 horsepower NASCAR motor, for example, might only have 5 cfm of blowby.

Less blowby means more usable horsepower. Being able to baseline the actual blowby in an engine means you can then go back and try different ring configurations, ring types (conventional or gapless), different ring end gap settings and cylinder wall finishes to see which combination gives the best seal and the least amount of blowby.

Measuring blowby has been one of the best kept secrets with performance engine builders because it allows them to see how well the rings are or are not sealing. It also allows them to detect any ring flutter that may be occurring within a particular rpm range, and to then change the mass or end gaps of the rings to minimize the problem.

[lilpigzuk]

How Much Blowby Is Normal for an Engine?
How much blowby is normal? Dividing an engine�s maximum horsepower output by 50 will give you a ballpark number for how much blowby you would normally expect to see. For example, a street performance engine that makes around 500 horsepower will typically have about 10 cfm of blowby with conventional pistons rings and ring end gap tolerances. Higher performance engines that are built to tighter tolerances will usually have less blowby, as might those with gapless piston rings. An 800 to 900 horsepower NASCAR motor, for example, might only have 5 cfm of blowby.

Less blowby means more usable horsepower. Being able to baseline the actual blowby in an engine means you can then go back and try different ring configurations, ring types (conventional or gapless), different ring end gap settings and cylinder wall finishes to see which combination gives the best seal and the least amount of blowby.

Measuring blowby has been one of the best kept secrets with performance engine builders because it allows them to see how well the rings are or are not sealing. It also allows them to detect any ring flutter that may be occurring within a particular rpm range, and to then change the mass or end gaps of the rings to minimize the problem.

you missed the rest of the article vvega

http://www.aa1car.com/library/engine_blowby.htm

[vvega]

meh took 5 seconds to find on google ... there must be better ones out there more suited to diesal's

personally i dont see the point of the test seams kinda stupid

[darinz]

And from observation, deisel have ALOT more blowby.

[haynzy]

And from observation, deisel have ALOT more blowby.

Higher compression

[DaveM]

I agree with vvega, I can't see the point in having this done, especially on a Pre Purchase Inspection, surely Compression and Leak Down are more relevant?