Subject	Interesting that built 8.5:1 engines < stock comp #'s
Posted by	ZXoltan on September 23, 2016 at 10:20 AM
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In Reply To	Those numbers look OK for a TT. The NA compression >> posted by ZUL8TR on September 23, 2016 at 04:44 AM
Message	Seems that forged pistons have lower compression numbers than stock cast ones. Not sure if this is a difference in the ring materials, ring to cylinder wall seal, ring gaps, etc, but it seems to be the norm. It is almost counter-intuitive because heads and blocks are generally decked to restore the sealing surfaces, which would logically increase compression ratio. A drop would be expected with thicker HG, but even with oem gasket, the numbers always seem to be about 10 points below stock. Anyone...?
Follow Ups	what do you think of numbers? - nissan300zxwork 20:05:53 09/21/16 Those are the number I got from my new IPP block - Stanky 20:14:48 09/21/16 You'll be fine. - white22sky 20:44:19 09/21/16 those are fine (n/m) - aliaZ 22:17:51 09/21/16 ygm (n/m) - LJZTT 17:30:46 09/23/16 I'm assuming those 900 miles were stop and go. (n/m) - ForceFedTT (SoCal) 03:28:37 09/22/16 yes. (n/m) - nissan300zxwork 05:49:46 09/22/16 Re: what do you think of numbers? - cgrover300 05:43:32 09/22/16 Similar to mine, see profile for build info. (n/m) - J-Mart 14:30:34 09/22/16 Numbers look good - ZXRider 15:33:43 09/22/16 so couldnt boost over 14psi - nissan300zxwork 23:50:29 09/22/16 Those numbers look OK for a TT. The NA compression >> - ZUL8TR 04:44:58 09/23/16 Interesting that built 8.5:1 engines < stock comp #'s - ZXoltan 10:20:47 09/23/16 Forged pistons require more clearance. That would likely - MixManMash 08:15:35 09/24/16 The piston rings contain the pressure, not the piston - ZXoltan 08:48:17 09/24/16 cranking compression typically suffers a bit with big cams - LitlElvis 14:54:40 09/23/16 This. (n/m) - MixManMash 19:08:33 09/23/16 Agreed, Brett, but what about forged motors w stock cams? (n/m) - ZXoltan 08:45:45 09/24/16 Re: cranking compression typically suffers a bit with big cams - BLACKBEAST 01:14:30 09/25/16
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