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how are my compression numbers?

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Old 03-05-2017, 12:17 PM   #1
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Default how are my compression numbers?

After 2 years of being turbocharged with hard driving i thought it would be a good idea to do a compression test. Here are my numbers. 205, 240, 220 and 210. Personally i dont think they are too bad as they are all within 10 to 15 percent of each other. I have not had any major oil burning issues and the plugs look great. What do you guys think? And i am probably going to push the motor a bit further this season.
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Old 03-05-2017, 12:23 PM   #2
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And this was on a cold engine....
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Old 03-05-2017, 12:42 PM   #3
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Generally speaking more boost = more fun, but less miles of that fun. Those comp numbers aren't bad, but they show mileage/wear so just keep in mind you are shortening the life of the motor even further by exuding more power from it. Its just physics on metal moving parts. If you are good with that and can afford the fun, then go for it!
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Old 03-05-2017, 12:45 PM   #4
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I pulled my kit yesterday in preparation for my FBM V2 and I found a ton of hydrocarbon, black soot, deposits in the exhaust ports. In the future I'm gonna up the rate of CRC valve cleaner, and sea foam Maintenance.
more to the point tho. I bet deposits with timing retarded ups the "dirty" rate so valves can't get a good clean seat. Worth a shot as a cheap way to keep those #'s high, and or troubleshoot varied cr's also verifying valve lash but that's less of a concern if you know the last time u checked them.
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Old 03-05-2017, 02:11 PM   #5
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A valve adjustment is on the list but im not sure how much it will effect the numbers. I have had the car for 3 years and i have no idea when it was done. While i am at it i will install ap2 intake retainers. Im pretty sure it will be over 220 across the board with a warm engine. I did the test with the motor at room temperature.
​​​​​​​sea foam is a great idea. I heard bg44 and techron products are much better though.
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Old 03-05-2017, 02:34 PM   #6
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Every FI motor ive seen, especial turbo set ups seem to accumulate much more carbon build up as Stewie mentioned. The only way a valve adjustment will effect comp numbers is if they are too tight to seat fully, or in Stewies meaning, because there is a crap ton of carbon build up and the valves are sticking/cant seat fully from that, hence the sea foam clean.

That said, this is only under the premise that comp irregularity are not from compression ring wear. Only way to determining that is to do a leakdown test. That will tell you right then if you have any valve seating issues.

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Old 03-05-2017, 05:30 PM   #7
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Cool, ill check those brands out to.

I let mine go for about nine months after I bought my Ap2 with just under 70k. When I finally checked them I was so mad I waited that long to just check/inspect them.
after the first full two piston inspections of under .006 on IN and EX I just stopped and began doing the adjustments on all 4. I didnt even have anything small enough to find a clearance, ie. "lash" Lol
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Old 03-07-2017, 11:46 AM   #8
 
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When doing a compression check another nice thing to note is what the fit hit says. That will tell you some things as well.

The overall numbers I don't get to hung up on. Too many variables to really try and compare that with others.

However, I do get concerned when they vary over 20%+ best to worst cylinder. Leak down test will tell you a lot more.
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Old 03-07-2017, 05:46 PM   #9
 
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I would do a leak down test. I had 235-245psi on 2-4 and 210psi on #1 did a leak down test # 1 had 60% leakage by the rings from a broken top ring. The engine ran good also.
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Old 03-07-2017, 07:10 PM   #10
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I plan to do a leakdown test when i get my hands on one. Keep in mind the motor was cold when i ran the compression test.
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