Just finished 12.25:1 d16y8 build.

Comp tested doing everything right with a $40 pep boys actron gauge doing 7 cranks and got 180-185psi across the board. I went back and did them 2 more times and got the same...all consistent.

Next night i tried it again and did 10 cranks, now they are all at 210psi across the board. Better but still not where it should be.

I did notice while doing the test that with each crank the gauge would go up to a number, fall then up higher, then fall, then up higher, then fall untill it stopped at 210.

Talked to a buddy with same setup (builthatch) and his are 250psi across the board so i know this is where i should be (he used leslie gauge?).

This actron gauge had the quick disconnect fitting on gauge to hose section and i'm wondering if different gauges would yeild lower numbers of up to 40psi???

Motor has 4000miles on it and like i said above all numbers are within 5psi across the board however not nearly as high as a comparable setups.

Any insite on how this could be? Wouldn't comp results be staggered if cylinders were washed out?

Thanks,
Vince

 

the compression numbers would be staggered if a ring was bad, yes. It can be affected by valve lash and operating temp just to name a few. Especially for forged pistons as they are known to expand quite a bit.

do the test, then watch the gauge to see if it slowly loses compression. if it does, its leaking out from somewhere (valve seals, rings, ETC.)

BTW, all gauges read a little different and the dynamic CR would be affected if you have a bigger than stock cam. With my LS, I had 180PSI with my 9.2:1 pistons, then with my 404's it dropped to 150PSI. Same pistons, obviously.

 

make sure you are doing this at wide open throttle, and remember consistent #'s are more important than high #'s for a compression test.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Cyphear &raquo;</TD></TR><TR><TD CLASS="quote">make sure you are doing this at wide open throttle, and remember consistent #'s are more important than high #'s for a compression test.</TD></TR></TABLE>

Yeah i did it at wot...the engine was rebuilt 4k miles ago so i'm hoping it's just that this tester reads that much different (40psi) than the one my buddy used.

We'll see, thanks guys!

Vince

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AgentJam &raquo;</TD></TR><TR><TD CLASS="quote">Yeah i did it at wot...the engine was rebuilt 4k miles ago so i'm hoping it's just that this tester reads that much different (40psi) than the one my buddy used.</TD></TR></TABLE>EASY! Just use your gauge on your buddy's car, & his gauge on your car.

Excess internal volume in the gauge, ESPECIALLY upstream of the gauge's check valve, cause a lower reading. Yours has some kinda coupling in the hose?? Sounds like that might be it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">EASY! Just use your gauge on your buddy's car, & his gauge on your car.

Excess internal volume in the gauge, ESPECIALLY upstream of the gauge's check valve, cause a lower reading. Yours has some kinda coupling in the hose?? Sounds like that might be it.
</TD></TR></TABLE>

rite, im thinking the tester is the culprit, cuz im his buddy with the 250 psi readings, and my build is identical, part for part to agentjams...

anyone else agree that the tester could be the issue?

 

now that you mention this...

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">Excess internal volume in the gauge, ESPECIALLY upstream of the gauge's check valve, cause a lower reading. Yours has some kinda coupling in the hose?? Sounds like that might be it.
</TD></TR></TABLE>

My check valve is as the bottom of the 12" long hose right where it plugs into spark plug threads. Hey Built is yours at the top near the gauge?

My actron holds pressure on the gauge so i know at least the check valve/gauge is not leaking but maybe it's just the design with check valve way down.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">EASY! Just use your gauge on your buddy's car, & his gauge on your car.</TD></TR></TABLE>

Hehe...i wanna do that asap cause i'm paranoid!
Vince

 

K hopefully you guys are still tuned in...i did another compression test tonight. First dry then with 5ml of oil...(goole says 1tbsp =15ml which is A LOT i thought)?

Dry run gave me ~210 across the board again when i cranked car like 12-15 times

With a decent shot of oil and maybe 10 cranks i got 240-250 across the board.

Amount of cranks was based around when needle stopped moving. 7 cranks was not enough to get it all the way to where it would level out. Is this just a characteristic of a weird gauge?

Anyway what i really want to know is...the 30-40psi increase when oil was added. Is this how much it would increase compression in an engine with perfectly sealed rings? Maybe this means that with my gauge 210 is great and with builthatch's gauge when he oils cylinders he gets 290-300?

What do you guys think...

Thanks,
Vince


Modified by AgentJam at 7:15 PM 11/15/2004


Modified by AgentJam at 7:17 PM 11/15/2004

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AgentJam &raquo;</TD></TR><TR><TD CLASS="quote"> Hey Built is yours at the top near the gauge?
</TD></TR></TABLE>yeah...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AgentJam &raquo;</TD></TR><TR><TD CLASS="quote">Amount of cranks was based around when needle stopped moving. 7 cranks was not enough to get it all the way to where it would level out. Is this just a characteristic of a weird gauge?</TD></TR></TABLE>Not 'weird', but that's definitely a characteristic of a gauge having a large volume (HOSE?) above the check valve.

 

Alright well i'm guessing my rings didn't seal properly after build because the oil made a good 40psi jump in compression #'s. I'll confirm this in a few days when i test on builthatch's gauge (nice enough to ship it to me ).

Anyway...motor was bored and honed .5mm over 4000 miles ago. If i swap out rings for new ones do i have to worry about honing again? Or the cylinder walls being glazed? (or do the rings just glaze?). Is there a special break in with this type of situation?

Thanks again guys,
Vince

 

Found this https://honda-tech.com/zerothread?id=376799 if anyone cares.

Kicker is at top of 2nd page.

 

hmm i cant get that link to work...

 

odd it works for me https://honda-tech.com/zerothread?id=376799

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AgentJam &raquo;</TD></TR><TR><TD CLASS="quote">odd it works for me https://honda-tech.com/zerothread?id=376799</TD></TR></TABLE>
if i put a www in front of it, it works...at any rate, the Lisle will tell the tale, it will be arriving at your house tomorrow or Thurs.

 

once again...THANKS!

 

well guys I used Builthatches gauge and got 240-235 across all 4 cylinders.

I'm relieved!!!

Insane how actron can sell a guage with 50psi difference...i was a few days from tearing the engine in half and re-ringing.

Thanks again guys!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AgentJam &raquo;</TD></TR><TR><TD CLASS="quote">well guys I used Builthatches gauge and got 240-235 across all 4 cylinders.

I'm relieved!!!

Insane how actron can sell a guage with 50psi difference...i was a few days from tearing the engine in half and re-ringing.

Thanks again guys!</TD></TR></TABLE>

YEAH BITCH! haha....i seriously was kinda excited to tear your piece down, but i guess i can live with the fact that your motor is perfectly fine ; )

 

I ask everyone with new motors and compression numbers this:

How did you break your motor in, 'take it easy' or 'get on it'?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AgentJam &raquo;</TD></TR><TR><TD CLASS="quote">well guys I used Builthatches gauge and got 240-235 across all 4 cylinders.

I'm relieved!!!

Insane how actron can sell a guage with 50psi difference...i was a few days from tearing the engine in half and re-ringing.

Thanks again guys!</TD></TR></TABLE>
like its been said before, variation of numbers not the actual PSI of the gauge is more important.

leakdown test &gt; compression test.

 

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

YEAH BITCH! haha....i seriously was kinda excited to tear your piece down, but i guess i can live with the fact that your motor is perfectly fine ; )</TD></TR></TABLE>

HAHA dude i was thinking the same thing actually...i mean if my compression did suck, that would just mean more power after a re-ring! hehehe.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drdisco69 &raquo;</TD></TR><TR><TD CLASS="quote">I ask everyone with new motors and compression numbers this:

How did you break your motor in, 'take it easy' or 'get on it'?</TD></TR></TABLE>

Actually funny you say that...i broke mine in "taking it INSANELY easy" ...the reason i did this is because i was running 12.25:1 compression with stock cam at first, then stage 3 crower cam with only p28 ecu and FPR...once i got my Power FC and fuel pump then i started taking it up to 7k, but that wasn't untill 4k miles.

I should have gotten on it harder earlier, but i guess i was just being a wuss! (Builthatch was making fun of my for driving it like a woman )

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Kamin &raquo;</TD></TR><TR><TD CLASS="quote">
like its been said before, variation of numbers not the actual PSI of the gauge is more important.

leakdown test &gt; compression test. </TD></TR></TABLE>

Yeah i was afraid though, my first engine build and i had no idea what could have been wrong.

Thanks again guys,

Vince

 

ALWAYS remember to disable your fuel system when you do a compression test. If you don't the cylinders get gas washed down and don't seal as well which drops the psi readings making people panic about their results. Then they add oil to the cylinder and of course the comp reading comes up because it compensates for washing all the regular oil off the cylinder walls and helps the rings seal properly.

Doing a test correctly is half the battle...if it's not done right, people start making the wrong conclusions about the readings.

 

The test was done right...

 

Btw....A compression test shouldn't take more than 5 cranks "If your compression is good". If it's taking you 6+ to get even descent readings I'd suggest getting a leakdown test done. Like peeps said above, car needs to be at operating temperature, fuel cut off, and throttle all the way open to get accurate readings. If your getting low numbers in two adjacent cylinders, then the problem is most likely bad head gasket between those cylingers. If you add oil and the difference in compression is more than 27 psi. Suspect bad rings, bent valves, or seals. Also a descent compression gauge always helps.