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Compression ratio from compression test?
Posted: Thu Sep 13, 2007 10:59 pm
by TurboDiverArt
Hi All,
I have what I think is a relatively simple question. Although I know not too accurate, I’m trying to get an idea of the compression in my engine. I just bought the car turnkey and have not really done much with it other than take it to the track a few times. I know the engine was originally built to run on methanol so it’s got some compression in it. I did a compression test on the engine while hot. The numbers across all cylinders were between 220 and 230 PSI. Can anyone give me an idea of what the effective compression ratio is?
Thanks,
Art.
Posted: Tue Sep 18, 2007 8:45 am
by greenracing
Since C/R is based solely on volume calculations, and the compression test numbers you get are based on how well things are sealed up, I don't think that you can reliably convert from one to the other.
Posted: Wed Sep 19, 2007 12:41 am
by SLICK VIC
You would need to know the specs on the motor.
cylinder head cc, piston dome cc, deck ht,
gasket thicknes & diameter, bore, stroke..etc.etc..
So if you ever tear the motor down and find the info
listed above use this link below to figure your C/R
http://www.fuelinjectionenterprises.com/compression.htm
Vic
Posted: Wed Sep 19, 2007 5:52 am
by TurboDiverArt
Since C/R is based solely on volume calculations, and the compression test numbers you get are based on how well things are sealed up, I don't think that you can reliably convert from one to the other.
I definitely agree you there. I just want to try and get a general idea if possible. The engine's running great so there's no real reason to tear it down.
Art.
Posted: Wed Sep 19, 2007 8:10 am
by greenracing
The engine's running great
Then the CR must be 'just right'
Posted: Wed Sep 19, 2007 8:13 am
by pro70z28
can you find out who built the engine? Follow the paper trail backwards.
Posted: Wed Sep 19, 2007 7:46 pm
by stimpy
you could do it the nascar way and pump the motor or fill the cylinder up with a fluid to measure the volume at tdc and bdc , but the hard part is getting all the fluid out it would be a guesstamite .
Posted: Wed Sep 19, 2007 10:17 pm
by Eric David Bru
you could do it the nascar way and pump the motor or fill the cylinder up with a fluid to measure the volume at tdc and bdc , but the hard part is getting all the fluid out it would be a guesstamite .
Are you sure that isn't CID not compression ratio?
EDB
Posted: Wed Sep 19, 2007 11:16 pm
by jim sanders
The engine's running great
Then the CR must be 'just right'
I'M WITH Mr.Green.. run it unti;ll you take it apart.
Posted: Wed Sep 19, 2007 11:18 pm
by stimpy
compare the volume at tdc vs the volume at bdc should give you the ratio and yes its a way of checking cid too but you use total volume .