Does anyone have a writeup on how to perform an engine compression check? I bought a kit where you plug the guage into the sparkplug connector but the instructions were very vague. Thanks in advance.

 

I assume this is no different than any other car. You need to disconnect ignition to all the cylinders, and one at a time remove the plug and connect the pressure gauge. Crank the car for a couple of seconds---if you can see the gauge while cranking, then stop when it stops increasing pressure, like 3-5 seconds a cylinder. Repeat on each cylinder. Write down the pressures for each cylinder on paper as you go. If one cylinder deviates far from the others you might have an issue (compare the low ones to the average psi.)

 

Thanks!

 

why would you want to do a compression check on a 5th gen, nearly new car?

 

http://forums.maxima.org/showthread.php?threadid=217579

 

so what, dont you have the specs written in the manual? unless you want to see how worn out your engine is. Or you hope to wear it out to boost-friendly? lol

 

in that thread there is a link to the write-up on doing compression test.

it is good to perform compression test frequently on boosted cars. esp when you decided to drop in a smaller pulley.

 

I found out recently that my nitrous kit was hooked up wrong, all this time I've been running Nitrous it was lean. I'm worried that my engine has alot of damage already so I wanted to do a compression test to find out. Thanks for the reply guys!

Here's what I did to perform the comprssion test.

1. Remove Fuel Pump fuse and then started the car a few times to make sure all the excess fuel has been used (fuse located below the steering wheel to the left, you have to remove the panal to see the fuses)

2. Remove Fuel injector fuse, (located in the same panal as the other fuse, diagram of which fuse is what is on the otherside of the panal)

3. Remove all the spark plugs (check out the "installation / how to" thread for spark plug removal instructions), I don't really think it matters if you remove all of them or take them out one by one.

4. Screw in the compression guage to where your spark plug would normally sit in and crank the engine 5 times. (NOTE: make sure you crank the engine the EXACT same number of times as the other cylinders otherwise your reading will be off! Each extra crank you do, the pressure will go up higher) According to the manual your pressure should be at 185, 145 minimum with an exceptable difference of 14 between each cylinder.

Additional Notes: You can buy this kit at any regular auto store, i.e. Pep Boys, Kragen (I bought mines at Kragen), it was about $40 for the kit. The Kit comes with instructions but are kinda confusing and geared torward older cars. What I listed above are the exact steps I did to perform this test on my 5th gen Maxima.

 

you guys seem knowledgable about the topic, can anyone tell me how running lean can cause the compression to drop? Does running lean cause more friction on the piston rings?

 

running lean makes your engine really hot....something is going to melt.

ideally you EGT should stay in the 700 celcius range after boost....when I fuel pump wasnt working....it went up to 870 celcius.

 

What numbers did you get?

 

Lets expand on that. What exactly is going to melt? If you are talking like the real melt, then the engine would lock right up. If the engine has working cooling system (thermostat, radiator, fan, coolant) would the engine still get overheated?

 

he's worried because he was running nitrous w/o the proper fuel added. This makes the engine run lean. Lean means the potential to run the car WAY to hot. Hot means some bad things like detonation, melted pistons, damaging rings and warping heads. So he wants to run a compression test to confirm he hasn't done any damage. I also strongly suggest a leakdown test and an oil analysis.

 

I had 165 on all the cylinders but I don't think I cranked it 5 times. On top of that my car has over 60k on it. I'll retry it tonight and see what it says. I don't think there's any damage based on the readings I got. Luckily the Nitrous kit I got was from ZEX, if I'm running lean it doesn't give you the full shot so the damage was minimal.

 

dont you know that not all of your engine is cooled by radiator and coolant? I dont have a water temp gauge. But when my fuel pump was not working and the car was running lean, the stock water temp meter was pointed right at the middle. Now the fuel pump is working and the reading is lower than before.

 

Hi! I just ordered the zex kit and I would hate to install it wrong and have it mess up my max. How was your hooked up wrong? Is this commonly installed wrong? Is your car much faster now that its hooked up right? Was it much slower before? Sorry for the 20 questions I am just super curious (and worried), as my kit is on the way :-)

also is your car an auto or stick?

 

Hi, don't worry about the questions. I always get ****ed off when I ask a question and no one responds with the right answers so I make sure that it doesn't happen to anyone else.

It's very common for the kit to be hooked up wrong, people think we have 2 fuel regulators when in fact we only have one. Make sure you TAP into ONLY the fuel regulator. (the damper and the regulator look exactly the same). Once it was hooked up right my car was definitely faster. The good thing about the ZEX kit is that if it doesn't have enough fuel it will not give u a big shot, so I wasn't running a full shot all that time. I have the ZEX dry kit by the way. I'm not sure if you ordered the wet or dry kit.

 

when you're cranking the engine that u have the throttle FULLY OPEN...all the instructions here aon how to do a compression test are good except this one is missing!

 

Thanks! Hmm.. I never heard anyone mentioned about the throttle having to be fully opened. I didn't do that when I ran the test, what's the reason behind that? Thanks in advance!

 

That shouldn't make a difference if you are comparing averages amongst the cylinders--just make sure it's the same when you test each cylinder. With the TB closed you are metering pretty close to what the engine is seeing while running at idle. TB open would be testing it at WOT, and I don't really think it would make much difference in the total anyway (assuming you are cranking it over a few times on each reading.)

 

Yeah that's what I did, cranked it 5 times all 6 cylinders and it came out to be exactly the same for each.

 

 

Just Curious:
Any track numbers to prove this? or just butt-o-meter? or any street races? Was it night and day difference?

I ordered the dry kit. I got it last Monday, hopefully this weekend I will install it.

 

Yes, I raced my friend's twin turbo Datson, he beat me by 2 cars before, we are tied now. RPM shot up faster, also the car feels faster.