Understanding Compression Test Results

[SilviablhS14]

Today I decided to do a compression test on my motor to see if its a good candidate for a Turbo. Here are my results starting with cylinder 1. 120-100-100-100. I thought this was odd with the #1 cylinder being higher than the others so I tested #1 again and got 85. I ran the test the exact same way all the times that I did the test.
The motor is a ka24de.

[badbob2121]

they are extremely low... are you sure you did the test correctly? did you do the test when the motor was warm or cold?

[SilviablhS14]

It was warm when I did it. I had just gotten back from picking the tool up from auto zone. I removed all of the plugs and the wires and then started the test. Did I do this right.

I just did another test after driving it around the block a couple of times and got these numbers.
120-120-120-120
They still seem low when compared to other numbers I've seen around the board but I know its good that the are all the same on all 4 cylinders. Is this right?

[Hoffman5982]

You should also unplug fuel injectors and hold it at wot while doing it. If they are still low, put some oil into the cylinder and test again. This is a wet test and will give you a good idea if it is your piston rings or not

[alms24sebring]

The wet test gives more accurate results.

It does sound alittle low but not dangerous

[Mercury_Hg]

It was warm when I did it. I had just gotten back from picking the tool up from auto zone. I removed all of the plugs and the wires and then started the test. Did I do this right.

I just did another test after driving it around the block a couple of times and got these numbers.
120-120-120-120
They still seem low when compared to other numbers I've seen around the board but I know its good that the are all the same on all 4 cylinders. Is this right?

How much was it to rent? Assuming you rented it.

[SilviablhS14]

How much was it to rent? Assuming you rented it.

Yeah I rented it for $40 but when you take it back you get your money back but I think you can get them for around the same price.

[alms24sebring]

A good name brand set is probably closer to $80-100+, but thats just a guess. Tools are expensive.

[xX RB Xx]

Minimal compression on a KA is 150+- 10 per adjacent cylinder. IIRC. so your not doing something right if your getting 85.

[placham]

I bet he didnt hold the throttle body butterfly open when he did the test, arent they like 165/180psi on a healthy KA, and it shouldnt vary more than 10psi per cyl general rule.

I usually use starter button with my one hand and hold the gauge also, and hold the TB open with my other hand, makes it a one person job, unless u have an assistant available. My Toyota 3SGTE cough up 210psi compression last week for ex.

[SilviablhS14]

I bet he didnt hold the throttle body butterfly open when he did the test, arent they like 165/180psi on a healthy KA, and it shouldnt vary more than 10psi per cyl general rule.

I didn't hold it open. I didn't know I was supposed to. So what are my results saying. Does my motor need a rebuild before I turbo it or is it something small like just replacing the head gasket?

[S13_RB25]

Well, since you missed a step in the compression test, do the compression test again! Warm up the car to normal operating temps, take out the the spark plugs, disconnect the CAS and the coil wire. Then hook up the compression tester and hold the gas pedal to the floor, to have throttle body wide open, crank the the motor until the needle on the compression tester stops moving!

[LoserCard]

And make sure your battery is fully charged!!! Or hook up to one of those high amp battery chargers. =)

[SilviablhS14]

Ok so I redid the test the two different ways ya'll suggested and these are the numbers I ended up with.
Without Oil
160-155-155-155
With Oil
175-190-175-185
These numbers are above the 150 mark that is said to be normal for the ka and are within the +/- 10 except for when I added in the oil and between cylinders 1 and 2.
Should I be worried about this or is it fine?

[Hoffman5982]

Those numbers seem pretty healthy, although it's weird that cylinder 2 jumped so high. I'd wait for feedback with better experience than me to tell you if you should be worried about that or not, but I've seen people with lower numbers turbo theirs before. Just make sure you get a good tune and you should be golden

[RustspecS13]

Just get a spare KA or two. They are cheap. Boost it, if it blows, put in another and start building or do an OEM rebuild with good parts.

AND FIGURE OUT WHAT WENT WRONG if something does blow up.

~Alex

[Hoffman5982]

I kinda agree with RustspecS13 but instead of waiting for it to blow, have a spare and build that up so that if it blows you have a stronger one ready to go back in, or if it doesn't blow you still have a stronger to swap in and then see the stock ka to recoup some of the money. But he's right, ka's are dirt cheap. I sold mine for 300 bucks and it was still running really strong when I pulled it

[asoomal]

Just get a spare KA or two. They are cheap. Boost it, if it blows, put in another and start building or do an OEM rebuild with good parts.

AND FIGURE OUT WHAT WENT WRONG if something does blow up.

~Alex

....WTF?

You know that Nissan has stopped producing them right?

[placham]

I say your good for a turbo, With Oil 175-190-175-185, numbers seem fine, ur probably 100K+ miles. You could do the test again if you want but its not unsual to see numbers like that, me personally I never use oil, ether do it on cold engine(if it don't run) or on warm engine. There could be several things like condition of valves etc and piston rings/cylinders, but I wouldnt worry about it with numbers like yours.
Just get good reputable parts, spend money once dont buy junk twice.

Think it should handle 10psi as it is all OEM, with good tune, and by good tune I mean an actual tune from someone that knows what their doing or dyno tuned is preferred and recommended, it will last. See lots of people half @ss $hit together and then complain about it blowing up.

As far as building up and parts for KA I dont know, never got into them, was going to use AMS exhaust manifold for KA way back when they had group buy for like 950USD IIRC or so. But then I also wanted a 6banger.

Read up info on here and also check out ka-t.org if your serious about it. KAs are as reliable as any other engine out there, it just depends on what you want out of it and how much you want to spend, as I was told long time ago performance coast $$$$$$$$$.

[badbob2121]

to me it sounds like you have a crappy tester, but its all good. since your planning to boost the oem build you really wont make any crazy power... so if it does blow, build the motor so it can actually handle over 300whp..

and in doing all this you might actually learn a few things that will help you with little problems like this in the future

[alms24sebring]

It sounds good to me. You should be good on a few pounds as long as you get it tuned! Most important step. And if it blows, get another one and rebuild if if you have the time and money for a longer engine life.

Yeah they stopped building the motors but they are so common that you can get one for $100-$200

[SilviablhS14]

This is good to hear. I originally rented a tester from Auto Zone but I just decided to buy one so that might be why the numbers sound so different.

Yeah the motors are very common. There is someone selling one near me for $70 for the bare block, cams, and pistons but the picture looks like it is rusted like crazy.