What is the acceptable variance between the wet & dry compression test?

For the wet test, I used about 3/4 cap full (small cap - about the size of a 20oz soft drink, not the big caps on Mobil 1). Test was conducted about 5 minutes after about a 30 minute drive on the highway.

My setup:
11.5:1 Compression
BC3+ Cams

On with the results:
Dry:
#1 240
#2 245
#3 235
#4 243

WET:
#1 265
#2 273
#3 251
#4 280

 

interesting. dry looks decent, but wet is a little iffy. I dont know how the two compare though.

 

here were mine, on a jdm itr. Cold with 1 cap of atf in each cyl. Car wont start so i didnt have the option of doing it after the engine had been warmed up.

dry:
1)220
2)160
3)160
4)140

wet
1)240
2)240
3)270
4)210


both suck! but hey just gives you someting to compare to

 

Sometimes during the test, when I'm cranking the motor, I hear a popping noise (happens just once/ cylinder if it happens at all), anyone know what this is?

I had the same popping noise when I conducted my leakdown test...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mr_gs-r &raquo;</TD></TR><TR><TD CLASS="quote">here were mine, ona jdm itr

dry:
1)220
2)160
3)160
4)140

wet
1)240
2)240
3)270
4)210


both suck! but hey just gives you someting to compare to</TD></TR></TABLE>

hmmm...this only confuses things for me.

I get that popping noise occassionally as well.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mr_gs-r &raquo;</TD></TR><TR><TD CLASS="quote">here were mine, ona jdm itr

dry:
1)220
2)160
3)160
4)140

wet
1)240
2)240
3)270
4)210


both suck! but hey just gives you someting to compare to</TD></TR></TABLE>

Is your motor eating oil? I'm sorry to say, your numbers make me feel better... but nonetheless, my motor seems to eat more oil as the gas prices rise. What a greedy, selfish *** motor. It's like an expensive gf. Atleast I get to ride it hard once in a while to keep me happy.

 

dont know if it eats oil or not it was bought form japan star and once i got itm, it never ran, a comp test revealed this and i'm pissed, hope they make you feel better casue they make me feel like ****** throwing up. No popping noise for me during test though.

 

just for the record i spoke with len and he thinks my problem is a valve issue, becasue all my comp numbers went up with the fluid added, but there was still a 60 psi variance between cylinders...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mr_gs-r &raquo;</TD></TR><TR><TD CLASS="quote">dont know if it eats oil or not it was bought form japan star and once i got itm, it never ran, a comp test revealed this and i'm pissed, hope they make you feel better casue they make me feel like ****** throwing up. No popping noise for me during test though.</TD></TR></TABLE>

Damn! I'm sorry to hear that man. I hope Japan Star takes care of you... that's horrible.

 

Yeah well of course he doesnt want to back it and blah blah blah...but the ****** thing wont even crank...never had sranked since we got it...sucks really bad. I'm not sure about how to compare dry and wet...buti od know that if all numbers go up after fluid is added the rings are ok and are doing their job. But your wet numbers are weird...way too much varaince! 30 psi is the max...and with that much it will run like ****...so next step for you would be a leakbown to see where your losing it at, IMO.

 

 

the popping noise is from the tester.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by intekragsr &raquo;</TD></TR><TR><TD CLASS="quote">the popping noise is from the tester. </TD></TR></TABLE>

Good stuff.

 

 

 

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Takumi Fujiwara &raquo;</TD></TR><TR><TD CLASS="quote">What is the acceptable variance between the wet & dry compression test?

For the wet test, I used about 3/4 cap full (small cap - about the size of a 20oz soft drink, not the big caps on Mobil 1). Test was conducted about 5 minutes after about a 30 minute drive on the highway.

My setup:
11.5:1 Compression
BC3+ Cams

On with the results:
Dry:
#1 240
#2 245
#3 235
#4 243

WET:
#1 265
#2 273
#3 251
#4 280</TD></TR></TABLE>

well the good thing about your dry test is that there al somewhat even, How is the overlap with BCIII cams? if there isnt alot over lap your compression numbers should be a bit higher on 11:5:1, like in the 260-280 range.

the wet test is showing some ring wear, not alot but noticeable, especially cylinder 4

 

well did another test taday after i finally got my motor running and my results were

1)240
2)240
3)240
4)235

helathy as a horse...got it running brought it up to operating tems, turned it off pulled the injector fuse, tested it and all seems to be ok, i have a healthy engine. Just goes to show how different the tests can be with the engine not running.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FR-MOB: Chubzilla &raquo;</TD></TR><TR><TD CLASS="quote">well the good thing about your dry test is that there al somewhat even, How is the overlap with BCIII cams? if there isnt alot over lap your compression numbers should be a bit higher on 11:5:1, like in the 260-280 range.

the wet test is showing some ring wear, not alot but noticeable, especially cylinder 4</TD></TR></TABLE>

It was tuned with alot of overlap, but I was having idling issues so it's less overlap now.

My pistons are coming out soon anyway... just have to decide if I want to spend another $500 on forged pistons, or go all OEM and get into DSP and try to be more competitive at autocross.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Takumi Fujiwara &raquo;</TD></TR><TR><TD CLASS="quote">

It was tuned with alot of overlap, but I was having idling issues so it's less overlap now.

My pistons are coming out soon anyway... just have to decide if I want to spend another $500 on forged pistons, or go all OEM and get into DSP and try to be more competitive at autocross.</TD></TR></TABLE>id go with the forged pistons

also were the tests done with the fuel injection/ign fuse removed?


Modified by FR-MOB: Chubzilla at 8:40 AM 5/5/2006

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FR-MOB: Chubzilla &raquo;</TD></TR><TR><TD CLASS="quote">id go with the forged pistons

also were the tests done with the fuel injection/ign fuse removed?


Modified by FR-MOB: Chubzilla at 8:40 AM 5/5/2006</TD></TR></TABLE>

yes and with the pedal to the metal... and to keep the tests as uniform as possible, I let it crank over 5 times per cylinder. I was going to keep cranking until it would max out on the meter, but I was afraid my battery was going to die out... I need to replace it soon, I won't get one more winter out of it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Takumi Fujiwara &raquo;</TD></TR><TR><TD CLASS="quote">

yes and with the pedal to the metal... and to keep the tests as uniform as possible, I let it crank over 5 times per cylinder. I was going to keep cranking until it would max out on the meter, but I was afraid my battery was going to die out... I need to replace it soon, I won't get one more winter out of it.</TD></TR></TABLE>

yeah battery and starter strength play a big part too. Id also let it crank over a few more times, 7-8 is the norm, but some motors still buil dup pressure after 8