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Old 08-06-2008, 04:50 PM   #1
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Default Bad News Bears Compression

Just had a compression test done today.

Came out

175/175/175/125

I'm flipping out on that last cylinder. I was planning on getting an install next week. Now I am going to seafoam the car, then get a leak down + another compression and see what the deal is.

**** sucks.
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Old 08-06-2008, 05:14 PM   #2
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ouch...that's low. Still think you don't need a re-route and a dual feed fuel rail?
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Old 08-06-2008, 05:17 PM   #3
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Quote:
Originally Posted by Zabac View Post
ouch...that's low. Still think you don't need a re-route and a dual feed fuel rail?
His car is stock and produced those numbers. Somethings gotta be wrong.

How many miles on the engine?
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Old 08-06-2008, 05:31 PM   #4
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Quote:
Originally Posted by Saml01 View Post
His car is stock and produced those numbers. Somethings gotta be wrong.

How many miles on the engine?
102k.

I've been thinking about it, and the car has been relatively well maintained and there is no reason the compression should be this low.

Thats why I am going to seafoam it and get "another" opinion.

My car doesnt feel low on power, and seems to get MPG in the 27-28mpg range.

I'm wondering if maybe they got word I was turbo'ing the car and tried to get me to buy the full deal rebuild or something. If so, I'm going to be pissed.

edit: also the number are pretty fishy too. All 175 and exactly 50psi lower on the last cylinder.
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Old 08-06-2008, 05:32 PM   #5
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My compression went out on #3 #4 on stock power too. At 130K, religious oil changes etc. Never revved when cold...still went out.
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Old 08-06-2008, 05:36 PM   #6
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Boost it and blow it up, then swap in a new motor.
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Old 08-06-2008, 05:43 PM   #7
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If you think it's fishy, repeat the test yourself. The cost of the tester is likely less than the cost of having someone else test it once!

Here's hoping it's just a stuck valve or something though..
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Old 08-06-2008, 05:43 PM   #8
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Sorry to hijack, but is there anyway to know if you have lost some compression on a cylinder without a tool. Meaning driving every day, can you feel the difference between 125 and 175? I can imagine enough loss and it will just run like ****.

And can someone walk me through this tool for me.
http://www.amazon.com/Actron-CP7828-.../dp/B00020BM28

The spark plug adapter is bolted into the engine and then the line is fished into the spark plug hole to mate to it?
Quote:
Originally Posted by kotomile View Post
If you think it's fishy, repeat the test yourself. The cost of the tester is likely less than the cost of having someone else test it once!

Here's hoping it's just a stuck valve or something though..
http://www.amazon.com/Actron-CP7826-...Q4Q1821E07MH2N
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Old 08-06-2008, 06:03 PM   #9
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Quote:
Originally Posted by Saml01 View Post
The spark plug adapter is bolted into the engine and then the line is fished into the spark plug hole to mate to it?
Pretty much. If you can change plugs, you can perform a compression test (with the tool).
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Old 08-06-2008, 06:07 PM   #10
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Quote:
Originally Posted by Saml01 View Post
Sorry to hijack, but is there anyway to know if you have lost some compression on a cylinder without a tool. Meaning driving every day, can you feel the difference between 125 and 175? I can imagine enough loss and it will just run like ****.

And can someone walk me through this tool for me.
http://www.amazon.com/Actron-CP7828-.../dp/B00020BM28

The spark plug adapter is bolted into the engine and then the line is fished into the spark plug hole to mate to it?

It will have some slight hesitation, but not everyone can feel a 10% power loss on a 100hp car.


The tool is pretty self explanatory once you have in in your hands. Just put the adapter on the end, pull the spark plugs, and stick the tube where the spark plug was.
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Old 08-06-2008, 06:18 PM   #11
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http://custompistols.com/cars/articles/compression.htm
http://www.imperialclub.com/Repair/Engine/tests.htm

or

Remove all spark plugs so the engine can rotate easily.

Block open the throttle plate (I usually just hold the pedal to the floor while cranking... This prevents restricted air flow into the engine.

Disable the ignition system to prevent sparks from arcing out of the disconnected spark plug wires or burning up coils.
Unplug coils

Disable fuel injection, it should also be disabled to prevent fuel from spraying into the engine.
Pull fuse

Check the manufacturer’s manual for specific directions on the tester.

Screw the compression gauge into one of the spark plug holes.

Crank the engine and let the engine rotate for about four to six compression strokes (compression gauge needle moves four to six times).
Write down the gauge readings for each cylinder and compare them to the manufacturer’s specifications. While holding pedal to floor

Wet add 1 tbsp of oil to cylinder and repeat... (add the oil to ea cylinder as you test it, otherwise you'll get sprayed on
and if your battery is weak, you may need a charger on it...
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Old 08-06-2008, 07:19 PM   #12
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just boost it. i didn't even do a compresion test before or after the turbo on my car.
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Old 08-06-2008, 07:25 PM   #13
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From a 92 Workshop Manual:
Quote:
INSPECTION, PAGE B-10
STANDARD: 1,324 kPa ( 13.5 kgflcm2, 192 psi 1-300 rpm
MINIMUM: 932 kPa (9.5 kgflcm2, 135 psi)-30~rpm

INSPECTION
1. Check that the battery is fully charged. Recharge it if necessary.
(Refer to Section G.)
2. Warm up the engine to the normal operating temperature.
3. Turn the engine OFF.
4. Remove all spark plugs.
5. Disconnect the ignition coil connector.
6. Connect a compression gauge to the No.1 spark plug hole.
7. Fully depress the accelerator pedal and crank the engine.
8. Record the maximum gauge reading.
9. Check each cylinder.
Compression:
1,324 kPa ( 13.5 kgf/cm2, 192 psi)-300 rpm
Minimum:
932 kPa (9.5 kgf/cm2, 135 psi)-300 rpm
Differential limit between cylinders:
196 kPa (2.0 kgf/cm2, 28 psi)
10. If the compression in one or more cylinders is low, pour a
small amount of engine oil into the cylinder and recheck .
the compression.
(1) If the compression increases, the piston, piston rings,
or cylinder wall may be worn.
(2) If the compression stays low, the valve may be stuck
or seating improperly.
(3) If the compression in adjacent cylinders stays low, the
cylinder head gasket may be defective or the cylinder
head distorted.
11. Connect the ignition coil connector.
Chris
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Old 08-06-2008, 10:24 PM   #14
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Quote:
Originally Posted by bryantaylor View Post
just boost it. i didn't even do a compresion test before or after the turbo on my car.
Same here. Car had over 180,000 when I boosted it. Has just over 194,000 now.
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Old 08-06-2008, 11:21 PM   #15
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Quote:
Originally Posted by bryantaylor View Post
just boost it. i didn't even do a compresion test before or after the turbo on my car.
+1 its what I did. 10k miles so far and its good
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Old 08-06-2008, 11:26 PM   #16
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Quote:
Originally Posted by bryantaylor View Post
just boost it. i didn't even do a compresion test before or after the turbo on my car.
I mean that could be bad logic because perhaps you had good compression. I am gonna give the compression test 1 more go and make my decision accordingly. The shop where I was going to do the install said they'd do it for free and then we can discuss my options for getting me running.
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Old 08-06-2008, 11:58 PM   #17
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Quote:
Originally Posted by naarleven View Post
Thats why I am going to seafoam it and get "another" opinion.
Please don't keep your hopes up.

Quote:
Originally Posted by naarleven View Post
My car doesnt feel low on power, and seems to get MPG in the 27-28mpg range.
THose are respectable numbers indeed, but it's probably been this way for a while, maybe as long as you've owned it or longer. You would easily not notice this low #4.

Quote:
Originally Posted by naarleven View Post
I'm wondering if maybe they got word I was turbo'ing the car and tried to get me to buy the full deal rebuild or something. If so, I'm going to be pissed.
Not impossible but very unlikely

Overall,
1) this is not terribly uncommon. some BPs have been pampered and they suck. others have been used and abused and still blow good numbers.

2) **** these goddam compression tests. they are useless. you need useful data, like those which could be procured from a leakdown test.

3) did you outsource this compression test? if so, then I'd have to ask: "why?"
Based on that answer, I might suggest that turbocharging your car may lead to a lot of challenges.

Last edited by chucker; 08-07-2008 at 12:16 AM.
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Old 08-07-2008, 12:03 AM   #18
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Quote:
Originally Posted by chucker View Post

Overall,
1) this is not terribly uncommon. some BPs have been pampered and they suck. others have been used and abused and still blow good numbers.

2) **** these goddam compression tests. they are useless. you need useful data, like those which could be procured from a leakdown test.

3) did you outsource this compression test? if so, then I'd have to ask: "why?" based on that answer, I might suggest that turbocharging your car may lead to a lot of challenges.
Leakdown test is in the works.

and I outsourced my test, because as is, I have a lack of experience, a shortage of time, and a surplus of money.
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Old 08-07-2008, 02:48 AM   #19
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A shop that does a LOT of engine work may also have a borescope. The combination of a leakdown test and a borescope is pretty good in diagnosing engine problems.
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Old 08-07-2008, 03:09 AM   #20
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my guess is the battery was going a little low when they got to number 4
do the test again but this time start on number 4

I would boost it and worry later
put it this way if it is "down" you can lean all about tuning and so on on an engine that is not perfect - so if it blows up you were already "expecting" and budgeting for it

the next engine will be even more awesome think of the internals you can add for the "surplus" of money or you can just paypal to me
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