Low Compression In One Cylinder? Need Help

[wsln33]

Hi guys,

Got my car tuned the other day, it is a 26/30 and made over 450rwkw on 18psi pump through an auto. Started breathing heavily upon taking the car off the dyno I am told. It is cylinder two that is 40psi, all others are very close to 120psi. Put some oil in the bore and it went up to 65psi. It has argo rods and cp pistons and rings.

1) what is the problem? Rings gone bye bye?

2) Why did this happen?

3) Is this common or something to expect?

4) how much to fix if engine is taken to engine builder?

Thanks in advance

[luvpsi]

Hi guys,

Got my car tuned the other day, it is a 26/30 and made over 450rwkw on 18psi pump through an auto. Started breathing heavily upon taking the car off the dyno I am told. It is cylinder two that is 40psi, all others are very close to 120psi. Put some oil in the bore and it went up to 65psi. It has argo rods and cp pistons and rings.

1) what is the problem? Rings gone bye bye?

2) Why did this happen?

3) Is this common or something to expect?

4) how much to fix if engine is taken to engine builder?

Thanks in advance

id say it could be a number of thngs. it could simply be the head gasket has cracked around that cylinder or your rings have gone bye bye or many other things. i would say if its rings its a ring change depending on the bore itself. correct me if im wrong guys

[doo doo]

if it's your rings the I've been told the comp would come back up more than that, almost back to normal. Leak down test time for diagnoses.

[tridentt150v]

gudgeon pin slipped out? It would need scour the bore for only 65psi.

I'd say head gasket or bent valve, but we are all guessing until you open it up and see inside.

[MrStabby]

if it's your rings the I've been told the comp would come back up more than that, almost back to normal. Leak down test time for diagnoses.

Yep - to elaborate, the oil makes up the piston to cylinder clearance, like a ring would, so;

- if the compression comes back, your rings are stuffed and top end is good

- if it doesn't come back its top end, ie valve/head gasket/cracked head... OR both top end and rings....

[marksuxass]

Hi guys,

Got my car tuned the other day, it is a 26/30 and made over 450rwkw on 18psi pump through an auto. Started breathing heavily upon taking the car off the dyno I am told. It is cylinder two that is 40psi, all others are very close to 120psi. Put some oil in the bore and it went up to 65psi. It has argo rods and cp pistons and rings.

1) what is the problem? Rings gone bye bye?

2) Why did this happen?

3) Is this common or something to expect?

4) how much to fix if engine is taken to engine builder?

Thanks in advance

Had the same thing happen on my rb26, number 2 had about 25 psi, and the rest around 130 psi. Have stripped the motor down to find that number 2 piston was melted around the ring land area

[R31Nismoid]

^ hope you use another tuner once its rebuilt.

rarely hear of a single piston melting on a proper tune.

[marksuxass]

^ hope you use another tuner once its rebuilt.

rarely hear of a single piston melting on a proper tune.

Hadnt had a tune, stock engine stock turbos stock ecu, but with an injector with alot of crap in it. *sigh*

[Rolls]

Hadnt had a tune, stock engine stock turbos stock ecu, but with an injector with alot of crap in it. *sigh*

there is your problem, one lean injector probably = a hole in your piston if comp is that bad with oil in it. A decent tuner should have picked up the detonation though and needing more fuel than normal to compensate for 1 cylinder barely firing.

I'd be asking them what knock detection equipment they use and if they say none you ask for nothing less than a refund.

Edited November 8, 2010 by Rolls

[STATUS]

sounds like it has a hurt piston.

Broken ring lands, seized rings or melted crown/ lands.

[marksuxass]

there is your problem, one lean injector probably = a hole in your piston if comp is that bad with oil in it. A decent tuner should have picked up the detonation though and needing more fuel than normal to compensate for 1 cylinder barely firing.

I'd be asking them what knock detection equipment they use and if they say none you ask for nothing less than a refund.

haha i know that was my problem, thats why it only leaned out on 1 cylinder. As for the tune as stated before it never had one, so i only have myself to blame for it

[DVS JEZ]

The oil in the cylinder trick will only work if the piston hasnt melted. Ive had this happen in my sr20. Cylinder 2.

Now i tune my own cars

[Rolls]

haha i know that was my problem, thats why it only leaned out on 1 cylinder. As for the tune as stated before it never had one, so i only have myself to blame for it

oh right I got the impression it happened on the dyno, you said it happened after tuning, so it was happening before you took it there, why would you get it tuned if it was pushing loads of oil into the catch can?

[greenie 105]

id be looking towards valve seats burnt out on exhaust side.

[DVS JEZ]

He's not the op rolls

[Rolls]

He's not the op rolls

ohh no wonder I was confused, ty

[GTScotT]

He's not the op rolls

rolls for teh lolls

[marksuxass]

ohh no wonder I was confused, ty