I decided to check the compression on my cylinders because my car has seemed underpowered lately plus i was just curious to find out what kind of condition my engine was in. For the record My car has 86,XXX miles on it and a good deal of NA mods. I have never opened up the engine or anything of that matter, Just bolt on mods.

Now for the test results. I let my car warm up to operating temperature then starting at cylinder one i connected the compression tester, opened up the throttle all the way and cranked the engine for about 10 secs. I did this twice on each cylinder just to verify results. Here are the numbers i got starting with cylinder one and working my over to cylinder 4.

1- 175 PSI
2- 190 PSI
3- 185 PSI
4- 175 PSI

I checked Webtech to get correct values and it sayed base should be 213 but not be lower than 199. Now i am a little concerned because i am well below the suggested values. My car is reasonable low miles but i also drive it pretty hard. What do you guys think? is it just that all my rings are getting worn, my cylinders are out of round, combination of the both?? Any help is aprecciated.

 

what gauge were you using?
i had a few customer having bad readings with cheap gauge
then checked their engine with my snap on gauge and numbers were okay

 

^^ good idea, did you try the oil in the cylinder trick to see if it's the rings or a valve?

 

It's not a trick, it's a diagnostic procedure. When all four of my cylinders read 180 (+5) PSI, we put a squirt of oil down the spark plug hole and got 200+ PSI. BAM, she needs a ring-job. Why not 50/50 odds of rings or a re-honing of the cylinders? Because Hyundai got the alloy spot-on when they cast our engine blocks. I've seen photos of a naturally-aspirated Beta engine with 90+k, and been inside one personally that had 165k miles. Neither had worn through the factory cross-hatching. Mad John had an engine being driven hard with forced induction for 2 years and it took that sort of hammering to wear the bores out of round.

With low compression from worn rings, it will run smoother and weaker until it won't start anymore. That is something to save up your pennies to fix. With low compression from leaky valves, you are out the cost of a gasket set and some valve lapping compound, and your compression is right back where it should be. You might also be able to use a can of sea-foam to clear the carbon off the back of your valves that is causing low compression, and not even have to open the engine.

Your next step is finding out where the pressure is leaking: top or bottom.

$0.02

 

Denisst:

I have used two gauges actually. The first one was a snap-on. I originally tested with it months ago and got the same readings as the one that i used tonight. The one i used tonight was just one that i picked up from a checker for 30 bucks.

Supercow:

I havent tried the oil in the cylinders yet. I ran out of time today so i will try and get that done tomorrow and report back my findings. Im thinking is rings though because all cylinders are low. If it was a valve only the cylinder with the damaged valve would be low.

Stocker:

Thanks for the info. I figure it is just the rings and not that the cylinders are out of round. I ride my car hard but not hard enough to mess the walls up that bad. If i do the oil thing and still have bad compression i will start looking into the head. I have seafoamed my engine some what recently so it should be decently clean still as far as deposits are concerned.

EDIT:

When i took my plugs out I noticed they were rather black(looks like my engine is running super rich). This may have been from me not running my car in months and then turning it on tonight with the old gas in it so i could warm up the engine to preform the test. Now these plugs are pretty new. Have less than 500 miles on them so i dont think they should already be as dirty as they are. Just want to get a few opinions on this aswell.

 

I opine that you should get rid of the old gas and use fresh gas. Run it a few miles and check the plugs again.