Please Help, Compression Woes..

[H311RA151N]

ETCG made a somewhat recent video on this. I find that most people hear of pouring water in the intake of an engine and think it sounds absolutely insane.

[F20A CB7]

Taking from a text sent to a friend.

Last yrs it was 190 190 190 210 dry
When we did it last week when car wasn't starting it was 180 180 110 150
When I did it today I had the gas pedal down and I got 190 190 200 and 200.... with foot not on pedal I got 185 185 185 185

Perhaps since my battery was dyin the other day it didn't get full crank. I did each test today 4 times per cylnder.. 2 holdin gas 2 times not holding gas... and I also did the water thing.. the car was warm enough. Held it at 2500rpm sprayed mist intside throttle. And nothing really happened. I was doin it for 15mins. Then after that I did the dry test. I didn't do wet cuz my #s we good.


I was told by a good honda guy who deals with accords that the motor is healthy.

[johnl]

Perhaps since my battery was dyin the other day it didn't get full crank.

Well, if the cranking speed was slower when you did the last two tests then it's not a big surprise that the compression numbers were less with the last two tests. There are at least two factors related to cranking speed that might affect pressure on the compression test;

The pistons rings leak, even when in good condition (which is why pressures are somewhat higher for a 'wet' compression test, even with a 'good' cylinder). The more slowly the piston rises the more leakage occurs, so the lower the compression psi.

And;

As the gas (air) is quickly compressed it gets a lot hotter, so it expands (or tries to). Of course it's being forcibly compressed, so this manifests as raised pressure rather than as greater volume. This is additional pressure rise added to the pressure increase caused by the cylinder volume decreasing and forcing X gas quantity into a smaller space. The more slowly the piston rises the more slowly the gas is compressed and the less hot it gets (the same heat is generated in the gas for the same degree of compression, but there is more time for it to be cooled by the resulting heat radiating and conducting into the metal), so there is less 'expansion' and less heat related pressure increase.

You may also get more gas expelled back out of still partially open valves (as the piston begins to ascend) when cranking more slowly compared to cranking more quickly.

I also did the water thing.. the car was warm enough. Held it at 2500rpm sprayed mist intside throttle. And nothing really happened. I was doin it for 15mins.

I doubt a mist from a spray bottle is going to introduce enough water to do much at all in a brief period of time. Water injection introduces water as a mist, and is known to be associated with clean combustion chambers and valves, ports etc., but this cleaning occurs over a prolonged period of water mist being injected.

I was told by a good honda guy who deals with accords that the motor is healthy.

I suspect he's correct.

[F20A CB7]

I appreciates everyones help. Thanks u. 4 real!

[accordztech]

ETCG made a somewhat recent video on this. I find that most people hear of pouring water in the intake of an engine and think it sounds absolutely insane.

I have done it, water is a great cleaner. But don't pour it in!!!

[BLUBB2]

I was there to assist in the very first test done a year ago and the last test that was done just today..Still healthy as it was a year ago. Absolutely nothing has changed.

[af_1132]

Well thank goodness this worked out well. 185 in all cylinders is awesome!