There are several threads on this topic. Many EVO's have one cyl that reads low yet still make very good power. The boost tapering thing is normal. The gauge you use to read boost may not be accurate.

 

I agree. I've found many threads about this now that I've been doing more research.

I've also contacted a few well known shops in my area and they all agree that it's not really nothing to worry about. One shop even said that as long as they are within 20% of each other then I should be fine.

The boost tapering was discovered by using a MAP sensor so it wasn't only noticed by using my boost gauge.

My next step is going to be installing a Forge WGA to see if this helps the taper. It just may very well be because of my changed VE that the stock turbo can't keep up with the engine.

 

Sorry to bring this back up, but I too did a compression check and had similar results to Kapolani.

cyl 1---185
cyl 2---180
cyl 3---165
cyl 4---185

The reason I did a check is becuase I have a coolant leak that I cannot find. I pressurized the coolant system and their is no leak. But when I drive the car and rev it to redline, then the coolant leaks. I put screw clamps on all the hoses that enter into the thermostat housing and the water assembly pipe, but there is still a leak. The coolant residue is located below the thermostat housing and on top of the temperature sensor.

I am wondering if the coolant leak is related to the low compression on number 3?

 

#3 reads low and varies on mine but I'm not losing fluids either.

 

If cylinder pressure is leaking into the coolant system, yes. If you suspect this to be the case, it may not be a bad idea to pull the head and have the deck surfaced checked. If there is a leak, you'll likely see evidence of it on the gasket.

 

05's have a recall on the hoses from the turbo leaking. Mine had this problem as well. When I would drive the car hard I would smell coolant and the thermo housing always had tell-tell signs of leakage. I replaced the hoses and the problem was solved. You should try this before anything.

 

I never recieved a recall notice on mine. I even called the dealership where I got my car from and they ran my VIN and told me that my car is OK. Did you get a recall notice in the mail?

 

I didn't get a notice because it was way early when I got my car - Oct 04. I'm sure they didn't know about it then. I tracked it down a week after owning my car and replaced the hoses myself. There is a TSB posted on this forum about it.

 

Not all 05s are affected by this. If they ran your VIN and it checked out fine then you shouldn't any worries on that issue.

 

Finding out the trouble is due to a defective hose would be welcomed news. Even if the VIN check revealed nothing, I'd still consider replacing it. I don't see how that would explain the slightly different pressure in #3, but if it fixes the coolant leak, it's worth something.

 

So do you replace it with hoses from an 03/04? I would like to know more about this hose replacment.

 

When I did a compression test mine was 145 all the way across the board.. Seemed fine, and I have/had the coolant problem from the leaking hose's too, just got some good clamps, and wala, it was fixed.

 

+1, the hoses are cheap from mitsu, or free if you get the recall done... and the way you're describing the problem is EXACTLY what happaned to mine... replaced the hoses now it's fine.

 

umhh. Coolant hose leakage and drop pressure are two different thing. you're talking about the Coolant return hose. We're talking about coolant leak into the head.

 

Read the whole thread and you will understand what/who I'm addressing. Low cylinder pressure in one whole is common. Guy I was adressing was not original poster. He was complaining of losing coolant when pushing the car hard and stated were leak appeared to be. I've experienced this as well as others in this thread and it stems from bad turbo coolant hoses. Your right it has nothing to do with low cylinder pressure