Factory Cylinder Compression

[Mr Italy!]

Hey Guys,

I've been searching for the answer to this for a while and i havent been able to find anything.

Does anyone know the original cylinder compression when an R33 RB25DET engine is first built. I want to compare my engines current cylinder compression to what it came with from factory.

I guess it could be in an engine manual or something which i dont have access to.... or possibly locked in SK's brain waiting to be revealed?

Thanks!

Justin

[dezz]

back when i was looking for a 33, merli or merlin (cant remember hehe) was telling me that a fresh rb25det would be 170 on all cylinders..so i was supposed to look for a car that got close to that

[wrxhoon]

Hey Guys,

I've been searching for the answer to this for a while and i havent been able to find anything.

Does anyone know the original cylinder compression when an R33 RB25DET engine is first built. I want to compare my engines current cylinder compression to what it came with from factory.

I guess it could be in an engine manual or something which i dont have access to.... or possibly locked in SK's brain waiting to be revealed?

Thanks!

Justin

Its not a good idea to rely on the compression figure, it can vary depending on the gauge, battery, starter( crank speed) and the way its done ( cold, hot, WOT). To your surprise it could even be highet on a healthy old angine because of carbon built up. The factory pressure is 12.2 kg/cm2 for a turbo RB25.

A leakdown test will be more accurate indication of the condition of the engine .

[danielson]

12.2km/cm2 in psi is????

[LBR33]

173.5248 psi

[Mr Italy!]

Ahh yes i had been told it was around 170.

Thanks for your help folks!!

[MerlinTheHapyPig]

keep in mind, gauges vary.

anything above 140psi is fine, as long as it's more or less the same between cylinders.

[danielson]

i had 115psi on cyl6, up to 165 on cyl 2....lol u rekn theyr rat shit? haha

[fEkuaR]

i had 115psi on cyl6, up to 165 on cyl 2....lol u rekn theyr rat shit? haha

Sounds alrite to me mate just crank up the boost! haha

[danielson]

Sounds alrite to me mate just crank up the boost! haha

hehe yeah it was allready blowing oil outa everywhere!!! on 15psi! i wonder what 25 wud do??? lol

BRING ON THE T66

[The Mafia]

sounds like your motor is rooted. Time for Forgies, rods, and a bigger turbo

Low PSI on cylinder 6 is common for a stuffed RB25.

I tested mine at 90,000km, and tested properly, was 169psi accross all cyclinders, and 2% leakdown.

Hope its still like that lol

[Richmond98]

how do you do a leak down test?

[The Mafia]

lol no idea

[MerlinTheHapyPig]

i had 115psi on cyl6, up to 165 on cyl 2....lol u rekn theyr rat shit? haha

yeah, motor is rooted.

do the test again, record the results

then squirt a couple of squirts of oil through the spark plug hole, if the compression increases, then it's your piston rings, if it doesn't then it's head gasket or valves

make sure the engine is warm, all spark plugs are removed, fuel pump is disabled, and using wide-open-throttle when doing the test.

getting a leakdown test done by a mechanic can pin point exactly where the cylinder is leaking from, not sure how to do them, i think you need special equipment.

Edited May 16, 2006 by MerlinTheHapyPig

[wrxhoon]

how do you do a leak down test?

Very easy , while you have the plugs out to do a compression test, you do a leakdown test as well.

All you need is the leakdown tester and a compressed air supply.

You can usualy hear if you have any amount of leak where its leaking from, valves or bottom end .

[MerlinTheHapyPig]

found these guides on doing compression test and leakdown test if anyone is interested...

http://www.dsmgrrrl.com/FAQs/compression.htm

http://www.dsmgrrrl.com/FAQs/leakdown.htm

[danielson]

yeah, motor is rooted.

do the test again, record the results

then squirt a couple of squirts of oil through the spark plug hole, if the compression increases, then it's your piston rings, if it doesn't then it's head gasket or valves

make sure the engine is warm, all spark plugs are removed, fuel pump is disabled, and using wide-open-throttle when doing the test.

getting a leakdown test done by a mechanic can pin point exactly where the cylinder is leaking from, not sure how to do them, i think you need special equipment.

mate my dads an engineer for holden, so im pretty sure he did the tests correctly..lol but thanx for sharing the info, some people were bound to ask how to do it!!