Had it out to play lately Bill?
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| Author: | terrylittlejohn [ Mon Apr 15, 2013 4:25 am ] |
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I was just wondering if you tried just surpreme gas to see if your idle and cruise ratio change. with low comp when not under boost av gas will have a slow burn time and might be giving you a rich reading. I ran av gas in my high comp engine and mixed it 1to1 . |
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| Author: | billdedman [ Mon Apr 15, 2013 10:28 am ] |
| Post subject: | av gas + pump gas |
Quote: I was just wondering if you tried just surpreme gas to see if your idle and cruise ratio change. with low comp when not under boost av gas will have a slow burn time and might be giving you a rich reading. I ran av gas in my high comp engine and mixed it 1to1 .
I have mixed them before, but have not looked at the A/F ratio while using the mixture. I'll try that. Thanks !Bill, in central Arkansas |
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| Author: | slantzilla [ Fri Jul 12, 2013 7:49 pm ] |
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Had it out to play lately Bill?
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| Author: | billdedman [ Fri Jul 12, 2013 10:06 pm ] |
| Post subject: | Sad story... |
'Zilla, The strangest thing happened: The performance fell off and the engine just started running crappy... not an ignition miss, but just acting lazy, like retarded timing. It was getting hard to start, a puzzling malfunction on that engine because it always started on the first hint of activity by the starter. It was puffing black smoke like the carb was set way too rich. This engine has never seen more than ten pounds of boost, has always had 100+octane fuel, and the spark advance has never been allowed to go beyond 18 degrees (locked plate; no vacuum canister,) and we have always kept the mixture on the rich side (more about tha, later...) so, I think detonation can be ruled out. Never been over 5,500 rpm. We ran a compression check. Always before, the compresssion has been 160-165 pounds on all cylinders. We had 50 pounds on #1 and 55 pounds on #2. We assumed a blown head gasket so, after running the valves (they were all at the specified clearance) and visually inspecting the valve events for evidence of a flat lobe (none showing less lift than the original specs) we examined the lifter faces and they all looked like new... no wear patterns on any of them. This engine only has about 75 miles on it since it was built with all new parts. So, we pulled the head off. NO evidence of a blown head gasket after a close inspection of the block, head, and gasket sealing surfaces.... They were all intact and looking exactly like they should look, with the gasket's concentric circle marks continuing unbroken in the narrow area between the #1 and # 2 cylinders. We then tool the valves out of the heads to examine the sealing surfaces, and check for a bent or sticking valve. Nothing... nada. The sealing surfaces (valves and seats) were all shiny. The 340 valve springs (and, some weak inner springs) all looked and felt fine. We (originally) put this engine together carefully, using the recommended toque tightening sequence after 45 pounds was reached, increasing the torque in 5-pound increments.. ARP 220,000 psi head studs were used, torqued to 90 pounds-feet. #$@^&#*!!!!! All we could figure out was that the super-rich mixture that the engine was getting prior to this "failure" (due to some over-zealous "jetting" by yours truly,) had washed all the lubricant off the cylinder walls. and the rings were running "dry," with no oil-film to provide a seal with the cylinder wall, there wwas no effective "seal.". So, we did the only thing we could do; we decided to go ahead and O-Ring the block wile we had it apart (like we should have done initially.) We are doing that right now. I'll let you know how it works out, after we get it back together. Thanks for asking... Bill, in Conway, Arkansas |
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| Author: | slantzilla [ Sun Jul 14, 2013 3:32 am ] |
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Did you check the pistons? I have had 2 fairly stock motors lose compression in #1 for no apparent reason. Had broken rings in both. |
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| Author: | olafla [ Sun Jul 14, 2013 6:19 am ] |
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Bill. I don't know how your Holley is set up, so feel free to call me stupid, but your description of the happening reminds me of a power valve gone bad... Olaf |
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| Author: | terrylittlejohn [ Sun Jul 14, 2013 1:55 pm ] |
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have you done your tear down yet to o-ring the block? if so how was the tension in the compression rings? |
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| Author: | billdedman [ Sun Jul 14, 2013 3:24 pm ] |
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Quote: have you done your tear down yet to o-ring the block? if so how was the tension in the compression rings?
Olaf, the power valve is boost referenced and was brand new (I bought a new one, turned the spring around and installed it; it was okay.)No, my over-zealous richening up the mixture to prevent detonation, plus a lead-poisoned O-2 sensor resulted in some off-scale rich conditions that probably washed down the cylinder walls. That's my best guess. Terry, we didn't pull the pan, so no, we don't know if it could be rings (broken) but why would new rings on freshly-machined bores break? No detonation, no hydraulic lock and forged pistons (Wiseco.) That will be a last resort... (pulling the pistons.) |
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| Author: | terrylittlejohn [ Sun Jul 14, 2013 6:12 pm ] |
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I`m just trying to sort something out to. I am running a rich setup and I am cooking the top compression rings, I am thinking that the extra fuel is burning around the ring lands over heating the rings. the hard starting problem I had was a blown gasket from lifting the head. the copper gasket had signs of egg shaping and soot between cylinders with sealant gone from copper gasket surface. |
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| Author: | billdedman [ Sun Jul 14, 2013 10:13 pm ] |
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Terry, I never heard of that. Generally speaking, I think a rich mixture burns cooler than a stoichiometric one, but I could be wrong. How much boost has this engine seen? Do you use the 220,000-psi ARP head studs? Bill |
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| Author: | slantzilla [ Sun Jul 14, 2013 11:43 pm ] |
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One issue I had spraying was fuel collecting in the top ring land and igniting when you snapped the throttle shut at the stripe. Fuel rich is not always safe. |
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| Author: | terrylittlejohn [ Mon Jul 15, 2013 1:44 am ] |
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with the run that I think I lifted the head I was trying a 1 to 1 pulley but I lifted at 15psi because the engine didn`t feel right. I went back to the 3% under drive pulley with 12psi boost but the et`s slowed and car got harder to start. I am using the 190,000psi strength head studs. stantzilla I am thinking something like that is happening to me because the top ring has all it`s tension gone when I tear the engine down at season end. my fuel ratio gauge reads 10 all the way down the track and 12 at idle. just after burning so many pistons I`m a little gun shy. |
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| Author: | olafla [ Tue Jul 16, 2013 8:01 pm ] |
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Quote: ...I think a rich mixture burns cooler than a stoichiometric one...
It does, but not much! But it produces a hell of a lot less power!I'll try to explain what I mean. We had another post here a while ago where I claimed that a rich mixture in a stock engine produces a tell-tale black oval on the ground behind the exhaust pipe, with an increased amount of water droplets. The reasons require a lenghty explanation, but basically it is because the part of the process when H2O molecules produced in the earliest part of the burn process cannot assist in producing CO2, because of lack of oxygen. Hence, CO and H2O is not converted, and therefore ends up as sooty water particles, but neither is the power produced, that should normally result from that part of the combustion process. It doesn't happen constantly, so an indication is for example an idle speed that is very difficult to set, it will wander up and down all the time; the richer the mixture is, the worse it is to adjust for. The combustion process is very complex, and very difficult to set up exactly over the whole rpm range. The downside of a perfect combustion process in a turbo/super-charged engine, is knocking, pre-ignition! The effects of an imperfect combustion process in parts of the rpm range, is extremely difficult to calibrate for, when the process is perfect in other parts of the rpm range. That is also the reason why I said that an ignition setup more like a street car may be a good idea, it can help to compensate for imperfect combustion. But in your case, the time span where power is produced is very short (9.8 seconds or so  ), so you need real-time electronic assistance. (There was also an interesting link here recently, to Toyota's 14:1 compression, super-lean, hi-po turbo engines, but it has taken them 50 years and billions in development money to get there!) My english is too clumsy for a good explanation, a very good summary of the overly rich - and therefore incomplete - burn process in a turbo engine is found here, it is definitely worth reading: http://www.innovatemotorsports.com/resources/rich.php Olaf |
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| Author: | terrylittlejohn [ Wed Jul 17, 2013 3:49 am ] |
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thanks olafla, if I understand it right a lean mix with less timing will increase torque by delaying the point at which the highest pressure is reached in relation to crank TDC position. |
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| Author: | olafla [ Wed Jul 17, 2013 4:18 pm ] |
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Yes, but it is a bit like playing with the devil; you may easily get burned! Careful, careful is the word of the day! It is a bit unusual approach, as the common practice is to advance the timing whenever the air/fuel mix is off the stoichiometric either way. As you suggest, you force the combustion to act in your favour by altering the timing while running a leaner mixture. Olaf |
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