Compression Test Results & Turbo Query

[Titan]

Today I finally got around to performing a compression test on my 89. She has 167,000 km (~105,000 miles) and runs quite well. Question is, is she good for low boost?

Cylinder 1 - 160 psi
Cylinder 2 - 155 psi
Cylinder 3 - 152 psi
Cylinder 4 - 155 psi

I checked the FSM, and the standard is 192 psi, while the minimum is 142 psi. So it seems my motor isn't in as good shape as I thought

I doubt she would be able to run 4-6 psi of boost reliably for very long, what does everyone else think?

Lastly, when I reinstalled the plugs, wires, coil wire, and fuel fuse, and started her; she ran right away, but was clicking. I couldn't find where the hell the clicking was comming from, and it seems it's most noticable at low rpms (idle). Any ideas?

Thanks for any suggestions.

[Jeff240sx]

Well, the clicking will either be a valve tapping or just the noisy injectors.
For the turbo.. I've always heard that the compression was 180 stock, but that might be for the KA24DE or even the s14.
Your compression is way off, and I wouldn't turbo it. I'd find out what is wrong with your car before the turbo goes on.
Bieng 40psi off is something terrible. Does your car blow smoke during startup, idle, or acceleration? If you did boost on it, whatever is broken in there will let boost pass through, and possibly do more damage.
-Jeff

[Titan]

Originally posted by Jeff240sx
Well, the clicking will either be a valve tapping or just the noisy injectors.
For the turbo.. I've always heard that the compression was 180 stock, but that might be for the KA24DE or even the s14.
Your compression is way off, and I wouldn't turbo it. I'd find out what is wrong with your car before the turbo goes on.
Bieng 40psi off is something terrible. Does your car blow smoke during startup, idle, or acceleration? If you did boost on it, whatever is broken in there will let boost pass through, and possibly do more damage.
-Jeff

Thing is, the tapping wasn't there before.

My car never blows smoke under any conditions. She has been sitting for about 2 months now due to being winterized. But I run her for about 10 minutes every week. I doubt this would contribute? Also, after I warmed the engine, it was about 30 mins or so before I could actually test the compression due to getting all the crap disconnected.

The guage I got is fairly cheap ($15 US), perhaps it's inaccurate? How much would a garage charge to test the compression?

Thanks.

[Jeff240sx]

Well.. if you really want to turbo it, then go to a shop and have them compression AND leakdown test the engine.
They shouldn't charge more than $100 for it, and their compression testers are more accurate, and their leakdown tester will tell you exactly where the compression is bieng lost, and then you will have real answers to whether or not you can turbo the engine.
-Jeff

[Titan]

But shouldn't I notice more problems if the compression is that low?

I mean, she doesn't smoke, I notice no power loss, and she passed emissions with flying colors. I realize the last one may not have a whole lot to do with it, but still.

[lbcklik1486]

What color is your exhaust? If its really white, your probably burning oil due to blow-by. You'd havta replace the piston rings then.

Jay

[projectsilvia1]

as long as you don't go below the 100 mark you should be fine as far as leaving it the way it is but if you turbo it do like the others said and have it compression and leak down tested...
Mike

[kandyflip445]

Oh c'mon. That compression isn't that bad at all. Well...for a turbo it isn't good....but look at it. All cylinders are about at the same level of compression. Also look at the miles. The compression being low like that would be due to normal wear. Like piston rings, cylinder walls...Also...about the leakdown tester...all a mechanic uses is a air compressor and a air gun...
Also it isn't exactly true that a shops compression tester will be more accurate. It just depends on which one the person owns. You can get a very accurate tester for yourself.

When you did your compression test did you make sure to pull ALL the plugs when before testing any of the cylinders? Also, did you make sure to have the throttle wide open when you cranked it? Doing those things will help you get the most accurate results.

EDIT: Oh, and just in case I didn't make my opinion clear I say don't turbo it unless you can restore your compression(new rings, hone cyl...)

[drift freaq]

compression drop due to wear and tear is normal. Though compression drop should be even across all cylinders if it is not you may have a problem i.e. valve seats are pounded , valve seals are leaking , rings are wearing out. I f you have a drop of 10 points of variance across your cylinders your engine is not in good shape and needs work.
Your compression test shows a 8 point drop which is getting real risky. considering your using a $15 dollar compression tester i.e. a piece of crap hahaha . I would follow Jeff240sx recommendation and get a good one or have a shop do a compression and leak down test on your engine.

[Jeff240sx]

I didn't mean that the mechanic has the bad-ass tester.. but it'll surely be more accurate than a $10 tester. You can also buy a compression tester with an air attachment to make a leakdown tester.
Why would all plugs need to be pulled? A cylinder is a self contained system. Finally.. I don't see how keeping the throttle open would change numbers either... minus the flooding of fuel.
-Jeff

[kandyflip445]

Oh, you could always perform a wet test too. Just put some oil(a squirt or two, but not too much) in the cyl. you are going to test and see if the compression raises. If it does then it is most likely rings and cyl. wear. If it doesn't then it didn't really help any All you know is that it could be a combination of rings and valves or both...but I would suggest trying this on the lowest one. The rule of thumb I have always heard is that there shouldn't be more than a 20% difference in the highest and lowest cyl. compression results.

[kandyflip445]

Originally posted by Jeff240sx
I didn't mean that the mechanic has the bad-ass tester.. but it'll surely be more accurate than a $10 tester. You can also buy a compression tester with an air attachment to make a leakdown tester.
Why would all plugs need to be pulled? A cylinder is a self contained system. Finally.. I don't see how keeping the throttle open would change numbers either... minus the flooding of fuel.
-Jeff

Keeping the throttle open helps fill the cyl. with air, helping to get a more accurate reading. If you are doing the test right both the fuel and the ignition should be off/disconnected. As for removing all the plugs.....not really sure about that one. I was just told that by my instructors. I'll be sure to ask them.

Oh, yeah. I didn't know he had a $10 tester. A mechanic would most likely have a better tester.

[mrmephistopheles]

I'm kinda curious as to the true compression of my '89s motor. My '91 has decent compression. I did a lukewarm test of the 89 (without having the throttle plate open) and got:
1.) 141
2.) 159
3.) 160
4.) 157

Which isn't bad for not being totally warmed up and not having the throttle plate open, but it's still obvious the #1 cyl is a bit fux0red.

Kevin

[kandyflip445]

Try a wet test on cyl. 1. Putting "Restore" in your engine might help. On some cars it will help a lot. On some....it isn't worth it. I would try that too run with it for awhile and then re-test your compression.

[s14slide]

Originally posted by Jeff240sx
Why would all plugs need to be pulled? A cylinder is a self contained system. Finally.. I don't see how keeping the throttle open would change numbers either... minus the flooding of fuel.
-Jeff

The plugs are pulled to see if compression is being lost between the cylinders through the head gasket, and pulling them allows whatever leak that 'may' be there show itself easily.