Very scary compression numbers on my turbo car
10-03-2011, 12:49 PM
#41
Just fyi, my car came with an egt gauge and under wot at the track it sits at 1,600 1650* f
For the last four and a half years. You think your egt's are higher than that? How hot do they need to be to burn a valve? Could they be bent? Still don't understand how your car could run so good with any of the proposed scenarios. You don't know anybody with a real compression tester? Snap-on or craftsman at least. Also as someone mentioned, was the engine fully warmed up? My buddy picked the strongest pistons when he built the engine. Unfortunately, that also meant that the alloy expanded more than the other option. So much so that you can hear piston slap when I turn on the car first time in the morning. I always let it warm up a little while before driving, and never boost until it's fully warmed up.
For the last four and a half years. You think your egt's are higher than that? How hot do they need to be to burn a valve? Could they be bent? Still don't understand how your car could run so good with any of the proposed scenarios. You don't know anybody with a real compression tester? Snap-on or craftsman at least. Also as someone mentioned, was the engine fully warmed up? My buddy picked the strongest pistons when he built the engine. Unfortunately, that also meant that the alloy expanded more than the other option. So much so that you can hear piston slap when I turn on the car first time in the morning. I always let it warm up a little while before driving, and never boost until it's fully warmed up.
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10-03-2011, 01:31 PM
#42
there is lots of info on warming up forged pistons/dealing with piston slap when cold. there is obviously two schools of thought on this, but you can find plenty of info by reading about forged vs cast pistons. needless to say, from what I understand the longer you idle during warm-up the worse the wear ends up. I won't go into it as its off-topic, but google is there for you when you need it.
my point was, a cold engine can have vastly different compression readings from operating temp. combine that with a shitty comp. tester can show scary readings. although, the fact that 2 different ones read 60 in the #1 cylinder can be alarming. still doesn't explain the engine running great.
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10-03-2011, 01:38 PM
#44
well, i don't sit there for 20 mins. but i appreciate your concern. and i do understand the concepts at play, with getting heat into the piston quicker to reduce the angles involved and possible wear of the cylinder walls and rings, but this engine was built in 2003, drag raced, driven all across the country before i purchased the car in 2007 where i have daily driven and tracked it approx. 50 times since. so i think it's doing okay at 70-80k since build. (speedometer died over a year ago, lol)
my point was, a cold engine can have vastly different compression readings from operating temp. combine that with a shitty comp. tester can show scary readings. although, the fact that 2 different ones read 60 in the #1 cylinder can be alarming. still doesn't explain the engine running great.
my point was, a cold engine can have vastly different compression readings from operating temp. combine that with a shitty comp. tester can show scary readings. although, the fact that 2 different ones read 60 in the #1 cylinder can be alarming. still doesn't explain the engine running great.
back on topic!
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10-03-2011, 01:58 PM
#46
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Just fyi, my car came with an egt gauge and under wot at the track it sits at 1,600 1650* f
For the last four and a half years. You think your egt's are higher than that? How hot do they need to be to burn a valve? Could they be bent? Still don't understand how your car could run so good with any of the proposed scenarios. You don't know anybody with a real compression tester? Snap-on or craftsman at least. Also as someone mentioned, was the engine fully warmed up? My buddy picked the strongest pistons when he built the engine. Unfortunately, that also meant that the alloy expanded more than the other option. So much so that you can hear piston slap when I turn on the car first time in the morning. I always let it warm up a little while before driving, and never boost until it's fully warmed up.
For the last four and a half years. You think your egt's are higher than that? How hot do they need to be to burn a valve? Could they be bent? Still don't understand how your car could run so good with any of the proposed scenarios. You don't know anybody with a real compression tester? Snap-on or craftsman at least. Also as someone mentioned, was the engine fully warmed up? My buddy picked the strongest pistons when he built the engine. Unfortunately, that also meant that the alloy expanded more than the other option. So much so that you can hear piston slap when I turn on the car first time in the morning. I always let it warm up a little while before driving, and never boost until it's fully warmed up.
Yeah, I don't get it either.
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10-03-2011, 02:32 PM
#47
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Why would it be consistently wrong? I'm thinking 1/8 turn int he tester fitting either way would make some variation in compression.
Also, do you guys think 243whp at 11psi on 8.6:1 compression is low? I sure do. I'm guessing this motor was blown up a long time ago. I'm really worried about getting in there and seeing a ton of detonation and a dead motor. I guess I'm going to plan on not running TT next year, time to buy a kart.
Edit:
The plugs all look exactly the same too.
Also, do you guys think 243whp at 11psi on 8.6:1 compression is low? I sure do. I'm guessing this motor was blown up a long time ago. I'm really worried about getting in there and seeing a ton of detonation and a dead motor. I guess I'm going to plan on not running TT next year, time to buy a kart.
Edit:
The plugs all look exactly the same too.
Dude here is sagacious advice from god's gift to turbo miatas (me). Just say **** it and run it. If it makes power then yay. If you're not detonating then the bottom end will be happy and all is good or at least good enough. Either that or shell out $1000 and fix a problem that isn't seriously hurting performance or incurring risk. Real men run it until it's really broke. /questionableadvice
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10-03-2011, 04:48 PM
#49
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If I really had all this leak, wouldn't there be tons of black smoke from all the fuel circumventing the combustion process, and wouldn't my WBO2 see that unburnt richness? I'm going to go home, pull some spark, and run this car at 12:1 for a few days and see what it does. For some reason I have this vision in my head of furry carbon on everything causing the leak.
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10-04-2011, 04:24 PM
#59
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I'm also thinking I had detonation or something although I never heard it on the dyno. That's basically the only excuse for eroded, leaky valves.
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