did my compression test

[mackeywatson]

Ok so I did my compression test. Basically it was 257 psi all across. What is the psi supposed to be? I'm assuming 257 is good, but just wondering where it's supposed to be.

I also found oil on the threads of the spark plug in cylinder 4. Should I be concerned about this?

[george]

YEPP..the seals around the valve cover over the inserting part of the plug is probably deteriorating..as for the comp..i never checked mines yet..

[Boosted2.0]

Normal range you see is like 190 - maybe 230 tops. 250s is awfully high. what were the indvidual cylinder readings and how exactly did you do the test. Oh and who makes your compression gauge?

[mackeywatson]

#1 - 258
#2 - 255
#3 - 258
#4 - 253

I took out all four coils, then all four spark plugs. Then my friend shoved the end of the gauge into the first cylinder while I cranked the engine and floored it. I was doing the cranking so I'm not sure exactly what he was doing to the cylinder. I'm not sure who made the gauge.

[Boosted2.0]

The cylinders are all close to eachother so I'm sure its just a cheap gauge and not an engine problem. Sounds like you have a very healthy engine

[skreemin_trdgts]

For all those anti-nitrous peeps who are worried about your engine, I've got 111,000 miles on my GT-S and went thru 3 bottles at the track last year with this 75 shot set-up. Out of curiosity, I did a compression test a few weeks ago and the readings were:
#1-225 psi
#2-205 psi
#3-225 psi
#4-220 psi
Toyota's specs for a GT-S are 203 psi max at each cylinder with no more than 16 psi difference between cylinders. My mechanic said my compression readings were great and that the reason for the #2 cylinder being lower was because that piston has less carbon build-up(which will raise compression) because the nitrous line going to that cylinder is a little shorter. That means that everytime I use the nitrous, that cylinder is getting just a little more nitrous before the other cylinders, and nitrous keeps the cylinder cleaner by burnig away carbon build-up.
Also for more accurate readings when doing a compression test:
1- always use a quality gauge
2- only crank the engine 4(four) revolutions and make sure each cylinder gets the same number(four) of cranks.

http://www.newcelica.org/photopost/data/500/5660Cnv0001-med.jpg

[Smaay]

that is a beautiful manifold!!!

[mackeywatson]

Looks like I'll have to do it again.

[Boosted2.0]

For all those anti-nitrous peeps who are worried about your engine, I've got 111,000 miles on my GT-S and went thru 3 bottles at the track last year with this 75 shot set-up. Out of curiosity, I did a compression test a few weeks ago and the readings were:
#1-225 psi
#2-205 psi
#3-225 psi
#4-220 psi
Toyota's specs for a GT-S are 203 psi max at each cylinder with no more than 16 psi difference between cylinders. My mechanic said my compression readings were great and that the reason for the #2 cylinder being lower was because that piston has less carbon build-up(which will raise compression) because the nitrous line going to that cylinder is a little shorter. That means that everytime I use the nitrous, that cylinder is getting just a little more nitrous before the other cylinders, and nitrous keeps the cylinder cleaner by burnig away carbon build-up.
Also for more accurate readings when doing a compression test:
1- always use a quality gauge
2- only crank the engine 4(four) revolutions and make sure each cylinder gets the same number(four) of cranks.

http://www.newcelica.org/photopost/data/500/5660Cnv0001-med.jpg

I wouldn't trust your mechanic - add a small measured amount of oil to all 4 cylinders and check the readings again and see if #2 comes up a lot more than the others.

[skreemin_trdgts]

I wouldn't trust your mechanic - add a small measured amount of oil to all 4 cylinders and check the readings again and see if #2 comes up a lot more than the others.

My mechanic is VERY trustworthy, with many years experience, and VERY knowledgeable, especially in hi-performance applications. I've known him for many years as well. Why would you say such a thing? The #2 cylinder, even though it is slightly lower than the other three, still had a psi higher than the Toyota max spec of 203.

[EasyC]

I wouldn't trust your mechanic - add a small measured amount of oil to all 4 cylinders and check the readings again and see if #2 comes up a lot more than the others.

My mechanic is VERY trustworthy, with many years experience, and VERY knowledgeable, especially in hi-performance applications. I've known him for many years as well. Why would you say such a thing? The #2 cylinder, even though it is slightly lower than the other three, still had a psi higher than the Toyota max spec of 203.


Toyota spec is 230 isnt it? My last car had comp of 235 across all 4 consistantly with 4 different testers.

[Boosted2.0]

My mechanic is VERY trustworthy, with many years experience, and VERY knowledgeable, especially in hi-performance applications. I've known him for many years as well. Why would you say such a thing? The #2 cylinder, even though it is slightly lower than the other three, still had a psi higher than the Toyota max spec of 203.

I say such a thing because I know these motors better than almost anyone. I work on LOTS of 1ZZs and 2ZZs and lots of Toyotas in general and a 20 PSI deviation to one cylinder is in no way shape or form normal. Healthy Toyota motors are most always within 0-5 PSI of eachother cylinder to cylinder. 20 is a very big differential and certainly worth rechecking.