Compression test!?

[TerminalTalon]

I recently had a compression test done. My numbers are cyl 1 is 100 and the rest are 110. I dont have a noticible oil out the exhaust. My dipstick reads the same all the time. I was wondering if I have a intake leak, ic piping, tb, intake manifold or head, will this lower my compression. Also if I have pistons that have a lower compression than stock will this lower compression?

 

[PieEyedPiper]

Also if I have pistons that have a lower compression than stock will this lower compression?

We don't need spock to tell us the logic we'd use answer to that one...

Tell us more about your setup. And was the engine at full operating temp when you did the compression test? Did your hold the throttle down to the floor the whole time? Did you add oil in the cylinders to see how much the results increased (used to detect piston ring failures)?

 

[oldman]

When ever you get consistant lower numbers across the board, the first thing is to verified the test results with a second tester then double check your testing procedures. Was the car fully warmed up, battery in full charge and full throttle applied for the compression test? What led to the compression test in the first place?

 

[TerminalTalon]

Yes it was at regular temperature. I had it done at a shop that is pretty good around here. My setup is in my profile. I also know I have a thicker head gasket which would lower my numbers. The only thing about this shop is that its $78 and hour and they should have done all that. I cant say if they did because they wouldnt let me go in the shop. Rediculous. It took 25 minutes and they didnt tell me I have a intake leak that is noticeable at part throttle through the throttle body. I will not go through them again. Thanks for the help.

 

[IWANTSPEED90DSM]

Yes, if you have lower compression pistons, your #'s will be lower. Also if you have aftermarket cams your #'s could be lower due to overlap.

And of course a thicker gasket would lower the #'s as well. Since theres no significant drop between each cylinder, I'd say it's fine.

 

[taloneagle]

i got a 94 \na talon with a 90 tsi motor in it an my compression test was 210 across the board. is that good???

 

[TerminalTalon]

I think it will be fine too. I still pull hard as hell with a throttle body leak and my intake manifold leaking. Thanks for the help godfathers. I will probably need some help with my fuel system in a week or two.

 

[PieEyedPiper]

Yes it was at regular temperature. I had it done at a shop that is pretty good around here. My setup is in my profile. I also know I have a thicker head gasket which would lower my numbers. The only thing about this shop is that its $78 and hour and they should have done all that. I cant say if they did because they wouldnt let me go in the shop. Rediculous. It took 25 minutes and they didnt tell me I have a intake leak that is noticeable at part throttle through the throttle body. I will not go through them again. Thanks for the help.

What exactly did you take the car in for?
I don't know of many shops that will do a boost leak test for you..
The reason you can't go into the shop is for liability reasons. What if you tripped over a stray bolt or worse stumbled into an engine lift and dumped it over? It's for your safety and to cover their ass (insurance).

It takes about 25min to do a compression test, you will get low readings with lower compression pistons + thicker head gasket.

The only thing about this shop is that its $78 and hour and they should have done all that.

What exactly should they have done? all what?

Yes it was at regular temperature.

Regular? I just want to make it clear - the engine should be tested at fulloperating temp, aka flesh-burning-hot.

Let us know!

 

[TerminalTalon]

It was at full operating temp I drove 30min there on the highway here in Jax. The boost leak thing. I told them I wanted a inspection also. They said they would look everything over for me to make my presumptions true or false. They proceeded to not tell me much except the cams would make my car idle a little weird. And by weird I mean a 1000-1500 "lope" in rpm at idle. You cant say that 78 an hour isnt up there, and they couldnt tell me I have a boost leak.

 

[TerminalTalon]

The leak is coming from the throttle body. I is a distinctive whistle. I have been to other shops and they let me go to the back and watch and answer questions they would have for me.

 

[TerminalTalon]

I am sorry about the other questions about the gasket and pistons. I was just wondering if they would lower it significantly like that.

 

[PieEyedPiper]

no need for appologies!
All labor rates around me at $84+ but yeah I know its not cheap.

Shops don't do boost leak test though, I don't think they'd even have an idea what to do unless it was slowboy or the like.

But you're absolutely right! for the money we should be getting a heck of a lot more, eh?

 

[TerminalTalon]

THats what I think. I am going to take the intake of this weekend and find the leak. Do a test and change the oil. Hopefully that will fix the minor things that are wrong. Thanx for the help.