Just curious to see if any of you have checked your compression. I checked mine several times during my turbo install/dyno and it was around 220-225 on all four.

 

I have no idea what you mean.

<brutally honest and not afraid to admit ignorance>

Wesmaster

 

how do you check it?

 

They sell a tool to check it with. With checking the compression you are able to see if the piston and rings are doing there job 100%. If it's a lower number then you have a problem and you will be losing performance. When I had my Civic Si with the turbo on it, I had 4 cracked pistons and my compression was just about 70 in each. Normal was around 205.

Justin

 

I've done this on several cars, but not yet on the S2000.

Basically it measures the pressure (psi) of the top end as the cylinder compresses and rises. Its a good way to tell how healthy an engine is (ring wear), since lost compression means loss of HP.

Usually done by removing all 4 spark plugs and disconnecting the fuse for the PGM fuel injection. A compression meter is inserted which looks like a dummy spark plug on one end. Turn the engine about 6 times and examine how quickly the engine builds pressure.

You can get these meters at any auto hardware store.

 

checked mine last week at a Honda dealer. NO *ZERO* compression in my #4 cylinder, weak 140ish in #3 cylinder.

 

I've been wondering about how to do this procedure correctly. In my previous cars, it was important to ground the coil and disable the fuel injection. Iceman - thanks for suggesting the method to disable FI, but with 4 coils, how do we ground the electrical system?

 

Disabling the electrical system is not important from what I've seen- at least in the past, I haven't seen it alter numbers. The only reason you would disable the coil is to kill all the plug wires, to do that for ours just disconnect the connectors on each of the coils.

I haven't checked the procedure on the S2, but on every car I've done you need to keep the throttle wide open.

YoungS2k, what's the deal with your #3 and 4?! That's horrible!!!

 

The main reason for disabling/grounding the electrical system is safety. The last thing you want is a high-voltage arc to ground in the engine compartment where gasoline fumes are present .

I think that removing the coil connectors and making sure that they are insulated and away from any potential ground would work as long as that would not damage the ignition system. I'm totally ignorant on this one because the last ignition system that I understood well was the one on my 1968 beetle . And to refer to another thread - it had points .

Good point about keeping the throttle body open.

 

Basically you need to do two things when checking compression. First (as mentioned) keep your foot to the floor and crank the engine (without the plugs) for 3 - 4 rotations. You need to allow the intake charge (less fuel) to enter the chamber. If you keep the throttle closed, air will only enter through the AICV and your readings will be off. Second, disable the fuel pump (pull the fuse) - you dont want fuel in the cylinder as it will throw off the comp readings.

I dont have the FSM in front of me - so I dont know what our compression should be - but on a 8.5 comp motor you'll see around 145psi, 9.5 around 180psi. All pistons should be within 3% of each other. If one piston is down - add a few teaspoons of oil into the cylinder and recheck the compression. If the compression jumps up, your rings are not seating. If the compression remains low (same as the 1st test) - then your head is to fault (bent valve, etc).