Help me figure out why my cylinder pressure is now so low...blown motor
10-08-2005, 08:23 AM
#1
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Thread Starter
Help me figure out why my cylinder pressure is now so low...blown motor
ok,
about 3 weeks ago i was out driving my car. t3 60 trim, uberdata, b16a, 450cc etc. anyways when i got home i noticed smoke coming from under the hood. so i popped it and there was smoke coming out of the valve cover filter. and it was blowing rank blue smoke out the exhaust. so i did a compression test and before this happened i was at 200psi in all cylinders. now
1.180psi
2.160psi
3.40psi
4.100psi
so im just wonderig what happened. this is what i think happened. i checked the timing when i first had the turbo and i had it set to 13btc which was the same as in uberdata at idle. now after my motor blew up it was at like 20btc(4*advanced) at idle. but still 13*in uberdata. so it wasnt calibrated right or something. my dizzy was tight so it never slipped. im trying to figure out what happened. doesnt look like the timing belt jumped a tooth either because i checked that also. so boosting for i dont know how long at a 20*advance (idle) im guessing had somehting to do with my compression numbers.
what would have broken or needs replacment? i think its just the rings got really worn or something. but i need some more info before i start ripping it apart. i mean its already out of my car so i can fix it this winter but what if i get new rings and it still blows blue smoke. what else could it be? never overheated so the head shouldnt be warped. i took off the headgasket and it looked hooped but that wold cause the car to blow white smoke wouldnt it?
thanks
about 3 weeks ago i was out driving my car. t3 60 trim, uberdata, b16a, 450cc etc. anyways when i got home i noticed smoke coming from under the hood. so i popped it and there was smoke coming out of the valve cover filter. and it was blowing rank blue smoke out the exhaust. so i did a compression test and before this happened i was at 200psi in all cylinders. now
1.180psi
2.160psi
3.40psi
4.100psi
so im just wonderig what happened. this is what i think happened. i checked the timing when i first had the turbo and i had it set to 13btc which was the same as in uberdata at idle. now after my motor blew up it was at like 20btc(4*advanced) at idle. but still 13*in uberdata. so it wasnt calibrated right or something. my dizzy was tight so it never slipped. im trying to figure out what happened. doesnt look like the timing belt jumped a tooth either because i checked that also. so boosting for i dont know how long at a 20*advance (idle) im guessing had somehting to do with my compression numbers.
what would have broken or needs replacment? i think its just the rings got really worn or something. but i need some more info before i start ripping it apart. i mean its already out of my car so i can fix it this winter but what if i get new rings and it still blows blue smoke. what else could it be? never overheated so the head shouldnt be warped. i took off the headgasket and it looked hooped but that wold cause the car to blow white smoke wouldnt it?
thanks
10-08-2005, 08:25 AM
#2
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Thread Starter
Re: Help me figure out why my cylinder pressure is now so low...blown motor (the.hamburglar)
oh yeah could it be a headgasket even if it blew blue smoke and my 3rd cylinder is low? i thought only either end would be low not in the middle
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10-08-2005, 04:42 PM
#10
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Re: (the.hamburglar)
GET THAT ANTIFREEZE OUT OF THE BORE! and wipe it down with some oil.
Look to see if you have significant cylinder wall scuffing. This is a tell-tale sign of broken-ring lands.
Ring lands are the "seats" for your rings. You have three rings...(from top of piston to bottom) Compression, seal(not sure if thats what it is called), and Oil control rings. Pictured below is a forged piston. The 3 machined "grooves" on the top half of the piston are the ring lands.(actually the bottom part of that is where the ring "sits" or "lands") These will break off and float there) they'll float there because if you think about it...they're pretty much trapped between the rings and the piston wall. You most likely broke the seal and oil ring lands.
for more information on rings terminology
http://www.hastingsmfg.com/Ser...n.htm
Look to see if you have significant cylinder wall scuffing. This is a tell-tale sign of broken-ring lands.
Ring lands are the "seats" for your rings. You have three rings...(from top of piston to bottom) Compression, seal(not sure if thats what it is called), and Oil control rings. Pictured below is a forged piston. The 3 machined "grooves" on the top half of the piston are the ring lands.(actually the bottom part of that is where the ring "sits" or "lands") These will break off and float there) they'll float there because if you think about it...they're pretty much trapped between the rings and the piston wall. You most likely broke the seal and oil ring lands.
for more information on rings terminology
http://www.hastingsmfg.com/Ser...n.htm
10-08-2005, 04:53 PM
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10-08-2005, 09:43 PM
#18
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Re: (the.hamburglar)
Old stock pistons + too much power = Blown ringland. Basicly there was sufficient cylinder pressure to push on the ring enough to crack the ringlands. 10.2:1 CR with stock cast pistons make it rather easy to do (moreso with 10.6:1). The other cause could be dtonation - high IAT's (from a smaller turbo) or too much timing (skipped a tooth maybe?) can put enough stress on the ringlands to break them too.
Stock B16s/B18c's are limited more by their pistons, unlike the LS (rods mainly).
Stock B16s/B18c's are limited more by their pistons, unlike the LS (rods mainly).
10-09-2005, 05:26 PM
#20
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Re: (the.hamburglar)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by the.hamburglar »</TD></TR><TR><TD CLASS="quote">cylinder walls are not scuffed. how could i have broken a ring land. can someone explain what happened briefly?</TD></TR></TABLE>
I shattered the **** out of my ringlands on my 99 Si and it didn't harm the cylinder wall in anyway. Sounds to me like you got in over your head with the teard down and don't even really know what you are searching for. Go pull the #3 cylinder out and take a picture for us. You will clearly see what the problem is.
I shattered the **** out of my ringlands on my 99 Si and it didn't harm the cylinder wall in anyway. Sounds to me like you got in over your head with the teard down and don't even really know what you are searching for. Go pull the #3 cylinder out and take a picture for us. You will clearly see what the problem is.
10-09-2005, 05:30 PM
#21
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Re: (the.hamburglar)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by the.hamburglar »</TD></TR><TR><TD CLASS="quote">so will i need a new piston? the sleeves look perfect still</TD></TR></TABLE>
I was just wondering...you are gonna be dissassembling the motor and taking the pistons out to swap the rings right? if you are already planning on doing that, then instead of guessing the condition of your pistons, why not just take a look at them yourself?
If I was in your place and I was gonna tear it down myself I would do that first before buying any rebuild parts. I would rather see what is wrong for my own eyes, instead of guessing before hand what could be wrong even though I'll end up finding out anyways after I've done my tear down.
I was just wondering...you are gonna be dissassembling the motor and taking the pistons out to swap the rings right? if you are already planning on doing that, then instead of guessing the condition of your pistons, why not just take a look at them yourself?
If I was in your place and I was gonna tear it down myself I would do that first before buying any rebuild parts. I would rather see what is wrong for my own eyes, instead of guessing before hand what could be wrong even though I'll end up finding out anyways after I've done my tear down.
10-09-2005, 08:00 PM
#23
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Re: (the.hamburglar)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by the.hamburglar »</TD></TR><TR><TD CLASS="quote">yeah but what causes a ringland to break?
</TD></TR></TABLE>
Detonation, or Pre-ignition.
Everything can look great...until you pull the piston.
Lesson learned...Get your car tuned by someone who knows what they are doing.
Modified by Bryson at 12:24 AM 10/10/2005
</TD></TR></TABLE>
Detonation, or Pre-ignition.
Everything can look great...until you pull the piston.
Lesson learned...Get your car tuned by someone who knows what they are doing.
Modified by Bryson at 12:24 AM 10/10/2005
