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B16 lost compression one cylinder -Diagnosis based on photos?
Car was rebuilt by me,
Fully done head by machine stock (oem) with dual b16 valve springs both sides, gsr cams, oem head gasket arp head studs, head gasket looked brand new upon removal.
NPR 10:5:1 pistons, eagle rods, NPR piston rings, 17 thousandths top, 20 thousandths bottom. *i've read to gap rings at 20 thousandths top, 22 thousandths bottom, should I rering entire engine to this?
Car was fine for 6k miles being turbo and tuned. Went for more power, it made 260 before and made 260 this time, tuner blamed it on ebay turbo, during tune, it lost compression on a cylinder.
Compression test: 200, 200, 200, 100
I attribute this to the tuner bouncing off rev limiter once or twice at 8500 rpm on each dyno run, it was holding together fine but the 5th run of this is when it developed blow by. Thoughts? Why do tuners do this ****?
I took the head off, dont see anything apparently besides some black marks from compression escaping, car had bad blow by after it lost compression on that cylinder.
Should I just replace this ring or replace all of them? Some scratches on bore of other cylinders, small up and down, maybe from debris? I did a good job cleaning so I dont know how that got in there.
Thoughts are appreciated, I have yet to take the bad cylinders piston out.
Images attached.
Bad compression cylinder
This cylinder had good compression, but slight up down scratches, I figure from debris? Can't catch a fingernail on debris though.
Scratches on the cylinder wall like that doesn't look good to me at all. Also, tuners will set the rev limit on the dyno and run it until it hits that rev limit.
I have 2 other short blocks in my shed, I just dont feel like taking this engine out. The scratched cylinder had 200 compression, the bad cylinder is the one with all of the black.
I consider this bottom end junk, I am gong to re-ring it in car, thoughts on re-ringing all cylinders or just the one that lost compression?
I have 2 other short blocks in my shed, I just dont feel like taking this engine out. The scratched cylinder had 200 compression, the bad cylinder is the one with all of the black.
I consider this bottom end junk, I am gong to re-ring it in car, thoughts on re-ringing all cylinders or just the one that lost compression?
If you were going to re-ring it, probably re-ring each one especially if you plan to change the ring gap.
Re: B16 lost compression one cylinder -Diagnosis based on photos?
I was just reading the FSM the other night and it said vertical scratches are perfectly acceptable if....
1) they don't catch your finger nail when you run it over them
2) they don't run the full length of the cylinder (ring run length)
This photo (your first photo) causes me to pause, not sure if the wide vertical lining is scratches or gaps allowing oil through as well as compression, I'm not sure if this is your problem cylinder:
Re: B16 lost compression one cylinder -Diagnosis based on photos?
^Yes that cylinder is my problem cylinder with compression of 100. I cannot catch anything on that area, it's just black from I think compression gasses getting by I dont know.
I take the oil pan off tonight and I will see if it broke a ringland or piston ring or something and will update.
I hope to get away with just re-ringing all cylinders with a fresh flexhoning and run this engine for a while till I can send one of my short blocks off to the machine shop for some css treatment bore/decking etc.
Re: B16 lost compression one cylinder -Diagnosis based on photos?
Broke ringland on that bad compression cylinder in 4 places lol. I have a new piston on the way. I guess I made rings too tight or car had a bad misfire at one point. I am re ringing the entire motor with new bearings to a looser ring spec.
Re: B16 lost compression one cylinder -Diagnosis based on photos?
I'm guessing you installed the piston rings without a compressor tool. Even though people may have done this many times without issues, chances of damage can happen...like in this case.
Re: B16 lost compression one cylinder -Diagnosis based on photos?
Originally Posted by Cupajoe
I took out all pistons and inspected them.
One piston also had a cracked ringland but still was holding good compression.
Anyway, I rehoned the block (flexhone), replaced all pistons, rings, bearings, reassembled all is good in the world again.
Thanks again.
glad you got it back up and going , today is the first time I saw this thread but I knew you had a cracked piston the second I saw the walls and had low compression, I did this exact same thing once and it only took a second to do the damage. This is the number one reason that I’ll never use a cast piston on a turbo setup, there just is not any room for error or punishment, good pistons are cheap these days while labor, rings, head gaskets, bearings, seals..ect ect are not cheap
Re: B16 lost compression one cylinder -Diagnosis based on photos?
Originally Posted by turboLScrx
…..This is the number one reason that I’ll never use a cast piston on a turbo setup, there just is not any room for error or punishment, good pistons are cheap these days while labor, rings, head gaskets, bearings, seals..ect ect are not cheap
I will have to disagree. Bad installation and/or worn-down parts is usually the culprit for premature damage.
Re: B16 lost compression one cylinder -Diagnosis based on photos?
Originally Posted by NVturbo
I will have to disagree. Bad installation and/or worn-down parts is usually the culprit for premature damage.
a cast piston will never hold up under detonation, they are just to brittle. 95% of built/performance engines will see detonation at some point, for a few hundred bucks I’d rather not rip my motor back apart
11-26-2018, 07:32 AM
B16 lost compression one cylinder -Diagnosis based on photos?
