compression test results

[1fstavant]

cyl 1 174
cyl 2 181
cyl 3 175
cyl 4 174

these good results for 2000k on a motor

[Siena]

20,000 miles? Or did you mean 200,000?

I only ask, because 20,000 miles is just loosened up.

My car's covered 214,000 miles, and still going strong.

[1fstavant]

i meant 2000 miles...rebuilt motor lol sorry

[1fstavant]

by the way this is done without wot throttle

[Jibberific]

probably can't get too much better than that

[1fstavant]

back to having a lean issue...not as bad but i did start to hear an exhaust leak could this be my culprit

[Don Supreme]

great results...

[1fstavant]

on thursday at the shop they were 180 across the board(shops guage)...maybe my lean condition is affecting me but taht was on a colder motor...i guess i should recheck using wot

[bassed]

on thursday at the shop they were 180 across the board(shops guage)...maybe my lean condition is affecting me but taht was on a colder motor...i guess i should recheck using wot

They compressor tester they use is of a much higher quality than 99% of us have or use. Don't sweat it if you can't get the exact same numbers they were able to get. Take theirs as bible and yours as slightly off

[1fstavant]

re did it using wot...
cyl 1 173-175 couldnt tell somewhere inbetween
cyl 2 180
cyl 3 181
cyl 4 180

cyl 1 could be the culprit to my slight mis in that cylinder idk tho maybe misshifting the one time slightly bent a valve?

[Don Supreme]

Didn't they check all the valves when they rebuilt the head?

I think the compression would be much lower than that if the valve was indeed bent.

[1fstavant]

they did...but im always skeptical you know...and can not afford to rebuild it again with in the next 3 months...so looks like ill be doing a compression test ever other week just to make sure everythings in check

but i mean a 7psi diff isnt even that bad i mean supposedly we have to be worried when its around 20+

[Don Supreme]

The test results are spot on.

[1fstavant]

thanks don hows the car coming along-any new vids

[Don Supreme]

Check my project thread..

[Kronic Budz]

how hard is it to do a compression test on your own and what tools do you need? how much would a shop charge?

[Seerlah]

Compression test is very simple. You can borrow one from Autozone for free or buy one for ~$25.

Steps:
1) Take out fuse for the fuel pump
2) Remove coil and spark plug from cylinder 1
3) Attach compression tester to spark plug socket (make sure the gauge has no built up pressure in it before use)
4) At WOT and warm engine, crank the ignition at most 8-10 times (clicks on same crank) as not to overheat/wear out the starter
5) Read the gauge on the compression tester which will tell you how much compression you have for that cylinder and write it down
6) Release pressure from the gauge
7) Remove compression tester, replace plug and coil, and repeat on other cylinders
8) Write down the compression numbers

As for what are healthy numbers, it is more of the gap between the numbers that is more of a substantial variable. ie I have 165, 165, 170, 165 or something like that, which is good for the age of my vehicle and miles on engine. But too low of compression is not good (like 145 psi)

[dougyfresh]

they did...but im always skeptical you know...and can not afford to rebuild it again with in the next 3 months...so looks like ill be doing a compression test ever other week just to make sure everythings in check

but i mean a 7psi diff isnt even that bad i mean supposedly we have to be worried when its around 20+

Any reason why you want to do a test every week?

I tested my new motor at 30miles, 150miles, 500miles, 2000miles and 5000miles and the results were the same for all those points.

[djwimbo]

but i mean a 7psi diff isnt even that bad i mean supposedly we have to be worried when its around 20+

7psi variance is <5% difference between cylinders. Not an issue at all. I wouldn't worry about it unless it's ~10+%.

and FWIW 175-180psi are "perfect" numbers.

A bent/burnt valve will generally only yield 50-80psi in that cylinder(some times 0psi). If you want to find where the leakage is going, do a leak down test. Basically you regulate shop air pressure to 100psi and feed it into the cylinder @ TDC on the compression stroke. That way the valves are closed. You pull off the oil cap and if need be the radiator cap, and see where the pressure is going. This should be done on a warm/hot engine.
Usually I use a plastic bag to show where the leakage is going, if the exhaust valve is burnt or bent the bag over the tailpipe will expand. Same thing if you place the bag over the oil fill hole or the throttle body.

... Honestly though, with your compression readings, I wouldn't waste my time on doing that test.

[1fstavant]

okay so tried replacing the fpr got wrong part...think this may be the actual culprit since i seem to have no pressure in my fuel lines- oh boy any one want to buy my car 12k takes it with 20k + into it

[20vpower]

ahhh dont give up now you're so close!

[1fstavant]

haha either it gets sold or it gets a match in the fuel tank while i run away

[1fstavant]

did a comp test again today
cyl 1 172
cyl 2 180
cyl 3 180
cyl 4 175
when i put oil in the first cyl it jumped to 181 i believe that ring didnt seat right

[dougyfresh]

What are you guys doing to break in your piston rings on the new motor(s)?

Why do I get the feeling that motor break-in has not been executed successfully?

I don't mean to be pointing fingers but it just surprises me to see so many engine builds and then re-builds [lately] because the ring gaps are not set right and the motors are not broken-in right to ensure good piston ring sealing. It hurts, mentally & financially, to have to rebuild the motor knowing those two things were not executed correctly.

[317ssayzarc]

did a comp test again today
cyl 1 172
cyl 2 180
cyl 3 180
cyl 4 175
when i put oil in the first cyl it jumped to 181 i believe that ring didnt seat right

You have to consider you put oil in there, which wont compress... That will raise your compression a few

[1fstavant]

so shits okay i take it...im sorry to bug every one just fn cant afford for this to blow again

[1fstavant]

fpr did nothing...helped but not much at half throttle perfect air fuel...wot once again rises...come to the conclusion it has to be a vacuum leak somewhere...so i am spending the next two days replacing every vacuum line possible...

[1fstavant]

alright replaced every single vac line...no worky half throttle 11.8ish jumps around to 12.0-12.1 full throttle hits 12.4 with occasional jump to 12.8 highest i saw hard to drive and watch a guage going full throttle...plugs are perfectly gray...no sign of lean mixture or detonation- do you guys think i have
A> exhaust leak- i do hear one when i start it when its dead cold
b> need a 3.5 or 4.0 bar fpr
c> maf-has never seen over 80-90 grams/sec
d>need to sell this money pit

[317ssayzarc]

A and B...

Fix that leak and your MAF is reading low... I was told by Tapp that around 100g/s is about 310-320whp, so you are reading low...

[1fstavant]

alright went out and with the help of zerb made a fuel pressure guage and picked up a 4.0 bar fpr lets see what happens,...shall we

[Don Supreme]

MAF is probably the problem -- forget that other mess.

If the maf is reading less air than is actually entering the motor, then the computer won't know how much fuel to inject.

The original fuel pressure should be fine.. Don't go changing that. The computer will just adapt it out anyway.

[1fstavant]

id agree but my maf has always read like that and never threw off my afrs- and part throttle its perfectly fine so after talking to chris he said i should bump up hte fuel pressure

[1fstavant]

ordered a new maf for measures...but the 4 bar fpr fixed my lean issue gotta get an adjustable fpr cuz i need it around 3.5 bar

[Don Supreme]

I would keep an eye on that, because eventually your long term fuel trim is going to pull it out.

[Don Supreme]

id agree but my maf has always read like that and never threw off my afrs- and part throttle its perfectly fine so after talking to chris he said i should bump up hte fuel pressure

@ part throttle the computer uses the o2 sensor to help make adjustments, so cruising usually works well, but @ WOT it ignores your narrow band, but it still uses your MAF....

[1fstavant]

well i got a new one anyway so thats going on tomarrow and if i get really rich ill go back to a 3 bar....found a 3.5 and at wot im 11.5:1 and part throttle 11.0:1

[1fstavant]

just talked to scott at usrt since im still running a tad bit lean for my liking...and basically would not let me buy new injectors till i diagnosed my car....helped me out a lot and i just wantd to let you guys know that they do not push parts on people which is nice in the modding world since even my own shop pushes parts on me with out the correct diagnosis first...so im off to figure out my problem
once again thanks to scott for all his help

[lookaught]

Can you explain why holding the throttle at WOT while cranking the motor for a compression test makes a difference? The car is drive by wire, I dont understand why this WOT business is important. I need to test my car tomorrow and had not heard of this before.

It makes the computer ignore the narrow band O2 readings and thus does what when starting?

Thanks!

[1fstavant]

i have drive by cable....but wot opens the thorttle plate allowing more air into the engine...

[lookaught]

Ok but in a drive by wire car, does it make any difference? For some reason I thought whoever posted the WOT instructions had an 01 car, which would be DBW.