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compression test or leak-down test

Old 27 September 2015, 04:52 PM
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Default compression test or leak-down test

i have been given some bad news on my forged 2.5,its kicking out a bit of smoke under heavy use and its only making 352bhp (mapped at 436bhp)

before i offer it up for sale i need to know whats causing the problem,will a compression test be better or a leak-down test?

the car is with mark @ thwaites at the moment

the engine still starts 1st time,runs fine and other than the power loss mark said it pulled well.

gutted is an understatment
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Old 27 September 2015, 05:01 PM
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Originally Posted by the shreksta View Post
i have been given some bad news on my forged 2.5,its kicking out a bit of smoke under heavy use and its only making 352bhp (mapped at 436bhp)

before i offer it up for sale i need to know whats causing the problem,will a compression test be better or a leak-down test?

the car is with mark @ thwaites at the moment

the engine still starts 1st time,runs fine and other than the power loss mark said it pulled well.

gutted is an understatment
How do you know it's not the turbo or something else.
As it's with a garage get them to take a look.
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Old 27 September 2015, 05:04 PM
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Originally Posted by fat-thomas View Post
How do you know it's not the turbo or something else.
As it's with a garage get them to take a look.
the turbo is holding boost fine @ 1.45 bar

what else could it be?

mark has checked the afr and thats fine
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Old 27 September 2015, 05:08 PM
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Is it burning oil?
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Old 27 September 2015, 05:13 PM
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personally id get someone to take a look at it.

"tired" is a pretty poor diagnosis
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Old 27 September 2015, 05:17 PM
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Originally Posted by bustaMOVEs View Post
Is it burning oil?
At high revs there is a lot of smoke being chucked out like a black/grey colour

On tickover there is no smoke or under normal driving there is no smoke

I have never really had to top the oil up. The engine was built by zen back in 2008/2009 so it's getting on a bit but milage wise it's on around 25k
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Old 27 September 2015, 05:19 PM
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Originally Posted by fat-thomas View Post
personally id get someone to take a look at it.

"tired" is a pretty poor diagnosis
I will have a leakdown test done. The car still feels really rapid and it's just took me all around the east coast covering over 400 miles problem free with no oil usage
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Old 27 September 2015, 05:21 PM
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Originally Posted by the shreksta View Post
I will have a leakdown test done. The car still feels really rapid and it's just took me all around the east coast covering over 400 miles problem free with no oil usage
so if its chucking out smoke but its not burning oil that surely points to the smoke being either fuel or water related.

if the car is chucking oil smoke out it would be burning it and need topping up.
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Old 27 September 2015, 05:32 PM
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Originally Posted by fat-thomas View Post
so if its chucking out smoke but its not burning oil that surely points to the smoke being either fuel or water related.

if the car is chucking oil smoke out it would be burning it and need topping up.
the only oil its using really is from the slight oil leak from the turbo feed pipe.

the car uses not 1 drop of water

i wonder if its connected to this issue i had last saturday

https://www.scoobynet.com/general-te...ick-blast.html
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Old 27 September 2015, 05:42 PM
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Originally Posted by the shreksta View Post
the only oil its using really is from the slight oil leak from the turbo feed pipe.

the car uses not 1 drop of water

i wonder if its connected to this issue i had last saturday

https://www.scoobynet.com/general-te...ick-blast.html

I'd investigate the issue properly as you have not yet had a proper diagnosis "tired" just sounds like a lazy mechanic who can't really be arsed to check it properly.

No oil usage and the oil pressure is ok and no noises points to a different issue to me.

That's assuming the pressures are ok etc
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Old 27 September 2015, 05:45 PM
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Originally Posted by fat-thomas View Post
I'd investigate the issue properly as you have not yet had a proper diagnosis "tired" just sounds like a lazy mechanic who can't really be arsed to check it properly.

No oil usage and I assume the oil pressure is ok and no noises points to a different issue to me.

That's assuming the pressures are ok etc
yeah oil pressure is fine, oil temp is fine,water temp is fine,no noises,no spluttering,no nothing really just about 90bhp down on what it should be
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Old 27 September 2015, 06:37 PM
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Sounds like its running far too rich if its throwing out black smoke.
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Old 27 September 2015, 06:45 PM
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Originally Posted by ScottyPPP View Post
Sounds like its running far too rich if its throwing out black smoke.
The afr is ok though
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Old 27 September 2015, 06:51 PM
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What was the AFR? If you can see black smoke out of the exhaust it's pretty damn rich. Mine will maybe have a puff of it as it comes onto boost.
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Old 27 September 2015, 06:55 PM
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Have you checked for split boost pipes etc.
How come thwaites have not offered a better explanation other than "tired"
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Old 27 September 2015, 07:12 PM
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Originally Posted by ScottyPPP View Post
What was the AFR? If you can see black smoke out of the exhaust it's pretty damn rich. Mine will maybe have a puff of it as it comes onto boost.
I'm sure he said 11 or maybe 13 I think
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Old 27 September 2015, 07:14 PM
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Originally Posted by fat-thomas View Post
Have you checked for split boost pipes etc.
How come thwaites have not offered a better explanation other than "tired"
To be fair chubby Tom he hasn't spent much time on the car yet and we only spoke briefly yesterday morning on the phone as I was at work.

If it had boost leaks would it not hold boost?
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Old 27 September 2015, 07:16 PM
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Originally Posted by the shreksta View Post
To be fair chubby Tom he hasn't spent much time on the car yet and we only spoke briefly yesterday morning on the phone as I was at work.

If it had boost leaks would it not hold boost?
nobody on here will have an answer without seeing the car,sounds like its in the best place already.
id ask him for a proper diagnosis before deciding anything else.
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Old 27 September 2015, 07:18 PM
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Originally Posted by fat-thomas View Post
nobody on here will have an answer without seeing the car,sounds like its in the best place already.
id ask him for a proper diagnosis before deciding anything else.
Yeah I will be speaking with him again 2moro
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Old 27 September 2015, 09:11 PM
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I'd reccomend a leak down test. On mine it was down on power and leak down results shown it was leaking 20-30%
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Old 29 September 2015, 10:08 PM
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A leakdown test will give more insight into the fault than a compression test can.

While the plugs are out it's easy enough to do both...
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Old 30 September 2015, 12:23 PM
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Leakdown test is the way to go as i think you may have AVCS on that engine and so a compression test might be inconclusive.
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Old 02 October 2015, 12:20 PM
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Results in........

Cylinders 1,3,4 down by 8-10%...........cylinder 2 down by 18%

No leaks past heads so piston rings on way out
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Old 02 October 2015, 01:28 PM
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Is that the percent they were leaking?
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Old 02 October 2015, 01:31 PM
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Originally Posted by imprezagaz View Post
Is that the percent they were leaking?
Yeah
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Old 02 October 2015, 01:53 PM
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I assume that was done on a hot engine?
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Old 02 October 2015, 01:56 PM
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Originally Posted by ScottyPPP View Post
I assume that was done on a hot engine?
Yes mate
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Old 02 October 2015, 03:20 PM
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I read Subaru allow up to 8% before needing repair. Having mine looked into at the minute as well. Mine was

1 20%
2 25%
3 20%
4 30%

When mapping they said its down approx 30bhp
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