I don't understand!!
06-01-2003, 02:32 PM
#1
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I don't understand!!
Hi all!
This may be a stupid question but I'm kind of new to cars.
Turned 21 may 30
My 1982 280ZX is originally a non turbo, but in -84 it was turboconverted by Bob Sharp Racing in the USA. It included forged pistons, turbo, intercooler, head-work +++. Now, what I don't understand is that in the service manual it say that the cylinder compression pressure for a non turbo normally is 12kg/cm (171psi) And on a turbo it is norally 10kg/cm (142psi).
When I tested the cylinder copression pressure it turned out to be 12.3kg/cm (175psi). I wonderd if this is good for a turbo engine? And what is the difference between the cylinder compression pressure and the Compression ratio.
Sorry about the bad english! I'm from Norway
Petter
This may be a stupid question but I'm kind of new to cars.
Turned 21 may 30
My 1982 280ZX is originally a non turbo, but in -84 it was turboconverted by Bob Sharp Racing in the USA. It included forged pistons, turbo, intercooler, head-work +++. Now, what I don't understand is that in the service manual it say that the cylinder compression pressure for a non turbo normally is 12kg/cm (171psi) And on a turbo it is norally 10kg/cm (142psi).
When I tested the cylinder copression pressure it turned out to be 12.3kg/cm (175psi). I wonderd if this is good for a turbo engine? And what is the difference between the cylinder compression pressure and the Compression ratio.
Sorry about the bad english! I'm from Norway
Petter
06-01-2003, 02:45 PM
#2
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Posts: n/a
I think its the same thing. Since your car is slightly higher than that of a NA 280zx, and the NA 280zx is low to begin with you should be ok, your engine may not last quite as long (150,000 miles) but alot of turbo cars today run turbos with higher compression ratios than that. If I were to turbo my car I wouldnt lower the compression ratio to that of the turbo specs, id leave it at the NA compression ratio.
06-03-2003, 05:32 PM
#3
Externally Wastegated
Join Date: Oct 2001
Location: San Diego
Posts: 1,220
Don't feel bad, I'm 22 and still learning!
If your car has had head work and a beefed up motor, I'm pretty sure they used higher compression pistons in your motor. I'm guessing either 8.5:1 or 9:1. Bob Sharp was well known in the racing world so I'm sure he had a reason for upping the compression on your turbo car. Most likely to reduce turbo lag and off boost driveability. The redesigned combustion chamber could also affect compression ratio too and increase efficiency. If the pistons and rods, etc are all forged, your motor will last forever and a day as long as you don't lean out and hit detonation.
Compression Ratio: Ratio of combustion chamber to cylinder volume + combustion chamber. (got that from Ray Hall Turbocharging) Compression in the cylinder shows relative health of the motor when stacked up to the factory specs. You could do a cylinder leakdown test to see how much blowby you're getting.
John 82ZXT
If your car has had head work and a beefed up motor, I'm pretty sure they used higher compression pistons in your motor. I'm guessing either 8.5:1 or 9:1. Bob Sharp was well known in the racing world so I'm sure he had a reason for upping the compression on your turbo car. Most likely to reduce turbo lag and off boost driveability. The redesigned combustion chamber could also affect compression ratio too and increase efficiency. If the pistons and rods, etc are all forged, your motor will last forever and a day as long as you don't lean out and hit detonation.
Compression Ratio: Ratio of combustion chamber to cylinder volume + combustion chamber. (got that from Ray Hall Turbocharging) Compression in the cylinder shows relative health of the motor when stacked up to the factory specs. You could do a cylinder leakdown test to see how much blowby you're getting.
John 82ZXT
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