800 ENGINE, WHAT SHOULD THE COMPRESSION BE?
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- Minor Friendly
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800 ENGINE, WHAT SHOULD THE COMPRESSION BE?
Hello, me again, yet another question if anyone can help. having trouble with the acceleration on my series 2. Binned the idea of changing the engine, too much stress! Can anyone tell me what a good compression reading is in PSI on each cylinder should be?
many thanks
Nicky
PS. can i also be enlightened as to what a 'goldseal' engine is?
(apart from an engine!)
many thanks
Nicky
PS. can i also be enlightened as to what a 'goldseal' engine is?
(apart from an engine!)
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that gold paint seems to have a hallucynagenic property as ppl who see a gold seal engine suddenly get all light headed and full of awe.
Personally, as the goldseal engine were rejects that had to be repaired, and the paint was a marketing gimick, and that there were so many bad ones - only buy one if you can see it running otherwise you are taking sa risk! (same advice is good for for a normal engine)
Personally, as the goldseal engine were rejects that had to be repaired, and the paint was a marketing gimick, and that there were so many bad ones - only buy one if you can see it running otherwise you are taking sa risk! (same advice is good for for a normal engine)
Ray. MMOC#47368. Forum moderator.
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Jan 06: The Minor SII Africa adventure: http://www.minor-detour.com
Oct 06: back from Dresden with my Trabant 601 Kombi
Jan 07: back from a month thru North Africa (via Timbuktu) in a S3 Landy
June 07 - back from Zwickau Trabi Treffen
Aug 07 & Aug 08 - back from the Lands End to Orkney in 71 pickup
Sept 2010 - finally gave up breaking down in a SII Landy...
where to break down next?
2013... managed to seize my 1275 just by driving it round the block
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lol - Matt go read those notes again...assuming the gas doesn't warm up when compressed
Ray. MMOC#47368. Forum moderator.
Jan 06: The Minor SII Africa adventure: http://www.minor-detour.com
Oct 06: back from Dresden with my Trabant 601 Kombi
Jan 07: back from a month thru North Africa (via Timbuktu) in a S3 Landy
June 07 - back from Zwickau Trabi Treffen
Aug 07 & Aug 08 - back from the Lands End to Orkney in 71 pickup
Sept 2010 - finally gave up breaking down in a SII Landy...
where to break down next?
2013... managed to seize my 1275 just by driving it round the block
Jan 06: The Minor SII Africa adventure: http://www.minor-detour.com
Oct 06: back from Dresden with my Trabant 601 Kombi
Jan 07: back from a month thru North Africa (via Timbuktu) in a S3 Landy
June 07 - back from Zwickau Trabi Treffen
Aug 07 & Aug 08 - back from the Lands End to Orkney in 71 pickup
Sept 2010 - finally gave up breaking down in a SII Landy...
where to break down next?
2013... managed to seize my 1275 just by driving it round the block
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I know thats a poor assumption but at pressure below about 50bar we have been told that gasses can be treated as perfect, ie. there is no interaction between them, i could work it out better, and I did say it was a back of the envelope calculation.......
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Ok, i did it properly, it is slightly rough, I assumed 1 cylinder = 200cc, combustion chamber = 30cc air comping in is at one atm and the engine operates at 100% efficiency, which gave a value of 210PSI. Of course engines don't run at 100% efficiency. If yours is 120PSI it is operating at about 60% efficiency which doesn't sound too bad to me........
(happy now ray?)
(happy now ray?)
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Dont worry Nickyi I dont know how these things work either using these calculations, but the later engines should have 160 - 180 PSI, so yours seems a bit low, I am sure Ray will let us know when he has finished pulling Matts Chain, unless someone else has the info to handyes Matt. thats what we need to know. Can you tell I haven't got a clue?!!
Cheers
Kevin
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Kevin
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Moderator MMOC 44706
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Had a quick look online, but I couldn't find exact figures for such a low compression.
The closest I found was a 7.8:1 engine where the nominal was 168 psi and 'service limit' (definately needs a rebuild) was 114 psi
Guestimating for your compression ratio, I would say 150 to 154 nominal and lower limit 105.
They should all be pretty close to each other - normally within 10%. If one of the cylinders is low, you should check some things out. Check if the gauge was inserted properly first. Try pouring a little bit of engine oil in the low cylinder's spark plug hole (not a lot of oil - that will give a fals result). Check its compression again. If it goes up, you may have a worn or damaged ring, piston or cylinder wall. If the compression does not rise, you probably have a leaky valve / valve seat (or maybe leaky head gasket).
If 2 adjoining cylinders are low, then headgasket becomes a stronger possibility.
If they are all similar but low - let us know and we'll keep looking for the correct pressure value in case my guestimate was wrong.
The closest I found was a 7.8:1 engine where the nominal was 168 psi and 'service limit' (definately needs a rebuild) was 114 psi
Guestimating for your compression ratio, I would say 150 to 154 nominal and lower limit 105.
They should all be pretty close to each other - normally within 10%. If one of the cylinders is low, you should check some things out. Check if the gauge was inserted properly first. Try pouring a little bit of engine oil in the low cylinder's spark plug hole (not a lot of oil - that will give a fals result). Check its compression again. If it goes up, you may have a worn or damaged ring, piston or cylinder wall. If the compression does not rise, you probably have a leaky valve / valve seat (or maybe leaky head gasket).
If 2 adjoining cylinders are low, then headgasket becomes a stronger possibility.
If they are all similar but low - let us know and we'll keep looking for the correct pressure value in case my guestimate was wrong.