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Got A Compression Test Done Today

Fujiwara

By Fujiwara,
in Engines & Forced Induction

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Blitz Grand Master

Blitz

Posted
Posted

Did you have the car compression and leak down tested before you purchased it?

ALWAYS have your car comprehensively checked before buying it, by a workshop that knows Skylines back to front and will go over the car with a fine tooth comb to make sure you know exactly what you are getting yourself on to.

wrxhoon Grand Master

wrxhoon

Posted
Posted

If the compression is only 75 on number 5 , leakdown would be like 75% on that cyl. What was the leakdown results on all cylinders? It could be any of several causes for the low comp or even a combo . If i was a betting man I would say broken ringlands on 5 but it could be a leaking H/gasket , valve..... A leakdown test will pinpoint it if its bottom end or in the cyl head .

As it is not a 10 year old car yet you are covered by consumer law for 3 months in NSW as long as the car has less than 100 k ks on the clock. Unless they can prove that you abused the car of played around with it , they will have to repair it as it is not normal wear and tear ...

One cylinder down to 75psi in a turbo car will not make a huge difference in power because when under boost that cyl is firing . Its like having a 1/12th power drop as that cyl only gives you half the power than it would normaly would . You should be able to pick it up when iddling because its not firing properly until it starts boosting .

mad082 Grand Master

mad082

Posted
Posted
If the compression is only 75 on number 5 , leakdown would be like 75% on that cyl. What was the leakdown results on all cylinders? It could be any of several causes for the low comp or even a combo . If i was a betting man I would say broken ringlands on 5 but it could be a leaking H/gasket , valve..... A leakdown test will pinpoint it if its bottom end or in the cyl head .

As it is not a 10 year old car yet you are covered by consumer law for 3 months in NSW as long as the car has less than 100 k ks on the clock. Unless they can prove that you abused the car of played around with it , they will have to repair it as it is not normal wear and tear ...

One cylinder down to 75psi in a turbo car will not make a huge difference in power because when under boost that cyl is firing . Its like having a 1/12th power drop as that cyl only gives you half the power than it would normaly would . You should be able to pick it up when iddling because its not firing properly until it starts boosting .

compression of 75 is about 50% of what it should be, not 75%.

Devils_Advocate21 Mentor

Devils_Advocate21

Posted
Posted

not to be picky but looking at the dyno, 1 its in shoot_6 not shoot_6F and god damn good intercooler for Intake temps of 14 degrees, i think best is just get them both done again at a reputable place, isn't there 2 types of compression tests??? wet and dry??

wrxhoon Grand Master

wrxhoon

Posted
Posted
compression of 75 is about 50% of what it should be, not 75%.

Here we go again .. Who said anything about compression being 75% dude ... I said LEAKDOWN on number 5 would be 75% . There is a difference just in case you didn't know ...Leakdown is measured in % of pressure lost and I said having 75 psi in number 5 would resalt in a leakdown of 75% .

mad082 Grand Master

mad082

Posted
Posted
Here we go again .. Who said anything about compression being 75% dude ... I said LEAKDOWN on number 5 would be 75% . There is a difference just in case you didn't know ...Leakdown is measured in % of pressure lost and I said having 75 psi in number 5 would resalt in a leakdown of 75% .

well sorry captain keyboard mechanic.

wrxhoon Grand Master

wrxhoon

Posted
Posted
well sorry captain keyboard mechanic.

Yea , maybe better to stick to the wastleland !!!! I guess if you just sit back and read .... you may learn from others that have some idea at what they are posting.

mad082 Grand Master

mad082

Posted
Posted
Yea , maybe better to stick to the wastleland !!!! I guess if you just sit back and read .... you may learn from others that have some idea at what they are posting.

and that some people are so far up themselves they are inside out.

wrxhoon Grand Master

wrxhoon

Posted
Posted
and that some people are so far up themselves they are inside out.

I wouldn't expect anything else from you dude .... This is the reason why you have no idea what you are talking about ...

I'll say it again leave the technical stuff to others .... stick to the WASTELAND, it suits you......

Fujiwara Proficient

Fujiwara

Posted
  • Author
Posted (edited)
If you had a leak down test done pre purchase and it was good then you may want to read up on what it is you tested before jumping the gun based on a compression test result.

You will not make 200rwkw on 12psi if one cylinder is bleeding off pressure.

I suggest 3 possibilities, 1) it's a dud compression test, 2) Your initial leak down test was dodgy, 3) you've broken the car between your initial leak down test and the later compression test.

If you take the car back to E&M to be checked and it shows all good, you will be charged for it. If it shows up bad, then make sure you are familiar with your warranty conditions because you had it independently tested, and it was good when it left the lot. You've played with it in the mean time. I think you will lose if it goes before a judge.

Not trying to be harsh, but seriously, find out what you tested pre purchase before going any further.

They did a leak down test. I just read it again in the morning.

I'll go home and re-read the details but they "said" that they did.

And what do you mean by played with it? I didn't add any parts to the car or tune the engine.

Just got a power run on the dyno and a comp test performed.

And i aint jumping the gun. Just being cautious.

And doesn't matter if it does sound harsh...i don't want to be treated like a bitch. I want the truth.

Im with Dave. Now that you say you had a leakdown prior to purchase and all was good there's not really much you can do.

Have another comp test done; chances are the test was a bit bogus. How many times was each cylinder tested, should be seperately tested at least twice if there's any funky readings.

If it has lost compression all of a sudden it would indicate detonation and smashed ring lands in that cylinder.

It is making 200rwkw on the stock ecu with 12psi so really it is quite highly strung. That small SMIC would heat soak fairly quickly after a hard run, keep your boot in to it and it will rattle its head off. The knock sensors only protect the motor around peak torque, high rpm the ecu ignores it.

I have a Frontmount IC. And each cylinder was only tested once. Except for cylinder 5. They tried it 3 times.

also if it was that low in compression in 1 cylinder you would be using a touch of oil and it would blow a bit of smoke when you got into it a bit. get someone to follow you and then give it a good bootful through first and second. if there is no sign of smoke it make be a dodgy test. if it does blow white smoke then the test is correct.

I always have a whitish smoke in the rear. But this is when i start up in morns or even in afternoons for the first time. Will definitely get someone to follow me.

If it is blowing smoke, what does this mean? Dodgy pistons/cylinder rings?

Did you have the car compression and leak down tested before you purchased it?

ALWAYS have your car comprehensively checked before buying it, by a workshop that knows Skylines back to front and will go over the car with a fine tooth comb to make sure you know exactly what you are getting yourself on to.

Didn't know i could take it to other workshops...now i know :D

If the compression is only 75 on number 5 , leakdown would be like 75% on that cyl. What was the leakdown results on all cylinders? It could be any of several causes for the low comp or even a combo . If i was a betting man I would say broken ringlands on 5 but it could be a leaking H/gasket , valve..... A leakdown test will pinpoint it if its bottom end or in the cyl head .

As it is not a 10 year old car yet you are covered by consumer law for 3 months in NSW as long as the car has less than 100 k ks on the clock. Unless they can prove that you abused the car of played around with it , they will have to repair it as it is not normal wear and tear ...

One cylinder down to 75psi in a turbo car will not make a huge difference in power because when under boost that cyl is firing . Its like having a 1/12th power drop as that cyl only gives you half the power than it would normaly would . You should be able to pick it up when iddling because its not firing properly until it starts boosting .

Don't think i have the results of the leakdown test. I need to go home and check.

And the car has statutory 3mths warranty + extended 2 yrs.

not to be picky but looking at the dyno, 1 its in shoot_6 not shoot_6F and god damn good intercooler for Intake temps of 14 degrees, i think best is just get them both done again at a reputable place, isn't there 2 types of compression tests??? wet and dry??

What is the difference between shoot_6 and shoot_6F? And the intercooler is a front mount so that is why it has low temps??

And isn't Advan Performance and CRD a reputable workshop?

Edited by Fujiwara
Baconer Grand Master

Baconer

Posted
Posted
I always have a whitish smoke in the rear. But this is when i start up in morns or even in afternoons for the first time. Will definitely get someone to follow me.

If it is blowing smoke, what does this mean? Dodgy pistons/cylinder rings?

That white smoke could just be condensation, hop out of the car and look at the 'smoke' when the car is idling, if it dissipates (think of steam coming out of an iron or pot) then its condensation, if it hangs around and floats up a couple of meters then you've got a problem

Abo Bob Grand Master

Abo Bob

Posted
Posted
compression of 75 is about 50% of what it should be, not 75%.

If you're going to correct someone so strongly you better be right. Wrxhoon quite likely has more years experience with Skylines and cars in general than you have been alive and you're calling him a keyboard mechanic?

We're all here to help and be helped. Spouting incorrect crap does neither so best to either keep it to yourself or preface it with, "I think..." or better, "I'm probably wrong but...".

Fujiwara Proficient

Fujiwara

Posted
  • Author
Posted

Ok...

E&M didn't reply to the 2 emails i have sent.

I received read receipts for these though...

Anyway, i took it to CRD.

All cylinders are fine.

Possible cause is carbon build up and the piston rings weren't sealing properly or something.

Cyl 1 185psi

Cyl 2 175psi

Cyl 3 180psi

Cyl 4 175psi

Cyl 5 175psi

Cyl 6 175psi

So now i can start doing some work.

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