Tested comp about 6 months ago and results were good -

225psi all four on ITR motor.

Had another test at weekend -

195 190 185 185

I know i have piston ring problems but would this cause that much drop?
40psi drop is alot and whats even more dissappointing is that i have a Spoon head gasket so was hoping for an increase.

Also can anyone explain the tech behind how comp and power are related to each other?

 

Same gauge? The measurement depends on how much volume is inside the gauge & it's extension hoses. Also depends (a lot) on the location of the check-valve within the gauge.

Engine warmed up the same both times? Battery, starter... The measurement depends on how fast the starter spins.

Disable fuel injection both times? Fuel sprayed into the cylinder will affect it.

WOT both times? Keep cranking until the gauge quits increasing?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Redsun &raquo;</TD></TR><TR><TD CLASS="quote">Also can anyone explain the tech behind how comp and power are related to each other?</TD></TR></TABLE>If the difference is caused by the stuff I said above, it's nothing. If it's real, then part of your power is leaking out. Thru the valves, past the rings, wherever...

 

i too had similar numbers for my h22 coup. comp was great, but after turbo it wasn't. now its am againg. anyway, your rings will absolutely cause that drastic a drop in comp. why? its because they are not sealing properly, thereby allowing gasses (compression) to escape by. poor rings will also cause a substantial increase in oil consumption. this will only get worse over time. with low comp, your engine's efficiency is greatly reduced and costing significant power loss. i would reccomend a ring replacement soon so as to minimize any long term affects. rings arnt that expensive either. would hate to see your itr motor **** the bed though. hope this helps!

 

So in other word High compression = good power because the more the engine can compress the bigger the bang?

Jim Blake, you seem to know your ****. I very much doubt the engine was warmed the same, and the gauge was not same. I didn't do it myself, i got two separate shops to do it each time.
But i have rebuild planned with EK9 pistons cos i am so convinced that there is a deffo problem -
1. I get a burning smell inside the car when i floor it?!!?

2. Blue smoke ffrom exhaust.

3. Oil is burning - strong smell from exhaust.

4. I run shitty times - 14.1 with streets, spoon cams and spoon hd gsket.

 

The differences in the gauges is why you're not supposed to compare absolute numbers. You only care that they are consistant. But high numbers are always gonna be bragging points. Just be aware of all the stuff that can cause differences.

Your 4 points... That stuff all hints at ring problems. You even said you knew about it.

Leaky rings means gases blow past them during the compression stroke. But the biggest thing is after combustion the expanding gases get past too. All of it is lost energy that could have helped generate more power at the crank.

You'd like the rings & valves to be perfectly airtight. But that's never gonna happen in the real world. You try to make it as good as you can without getting stupid & impractical.

 

My engine builder mentioned my head might also be warped. Cos he doesn't reckon rings will drop 40psi?

 

that is a possibility. if your head is warped, it wont seal and could cause low comp

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Redsun &raquo;</TD></TR><TR><TD CLASS="quote">My engine builder mentioned my head might also be warped. Cos he doesn't reckon rings will drop 40psi?</TD></TR></TABLE>There's lotsa possibilities. Even if the head is warped, maybe the rings are leaking too. Do a leak-down test to see where it's leaking.

 

bump. jims right on<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">There's lotsa possibilities. Even if the head is warped, maybe the rings are leaking too. Do a leak-down test to see where it's leaking.
</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Redsun &raquo;</TD></TR><TR><TD CLASS="quote"> i have a Spoon head gasket so was hoping for an increase.

</TD></TR></TABLE>


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

spoon cams and spoon hd gsket.</TD></TR></TABLE>
Did you install the cams at the same time as the gasket? Cams with more duration can cause lower compresion readings. Sounds like you need to do a leakdown test to see if you really have a problem or not.

 

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

Cams with more duration can cause lower compresion readings. </TD></TR></TABLE>



Not alot of people realize when you do a compression test, youre really measuring your dynamic compression.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LsVtec92Hatch &raquo;</TD></TR><TR><TD CLASS="quote">

Not alot of people realize when you do a compression test, youre really measuring your dynamic compression.</TD></TR></TABLE>

i didn't know that

 

damn. good info up in hurr.

 

Ok can someone please explain the difference in dynamic compression and normal compression.
Also i read in a manual that the B18C1 should read at 270psi!!??