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#1 (permalink) |
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Cunning Linguist
Join Date: Mar 2002
Location: Plano, TX 75074
Posts: 4,441
Real Name: Otto
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4-cyl. displacement = πD²S (pi x D-squared x S), where D is bore diameter and S is stroke length.
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1960: ♥ '61 Rekord PII 1.7 3S 3.9 ♥ '69 Kadett LS 'sprint' 1.9 3A 3.18 1970: ♥ '70 GT 1.9 4S 3.44 ♥ '72 GT 2.2SSD 5S 3.44 ♥ '72 GT 2.4FI 5S 3.44P 1980: ♥ '85 Bitter SC 3.9FI 5S 3.44P 2000: ♥ '09 Solstice GXP Coupe 2.0 SIDI VVT Turbo 5S 3.73P Last edited by tekenaar; 04-26-2007 at 04:05 PM. Reason: change piston to bore |
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#3 (permalink) | |
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Cunning Linguist
Join Date: Mar 2002
Location: Plano, TX 75074
Posts: 4,441
Real Name: Otto
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__________________
1960: ♥ '61 Rekord PII 1.7 3S 3.9 ♥ '69 Kadett LS 'sprint' 1.9 3A 3.18 1970: ♥ '70 GT 1.9 4S 3.44 ♥ '72 GT 2.2SSD 5S 3.44 ♥ '72 GT 2.4FI 5S 3.44P 1980: ♥ '85 Bitter SC 3.9FI 5S 3.44P 2000: ♥ '09 Solstice GXP Coupe 2.0 SIDI VVT Turbo 5S 3.73P |
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#4 (permalink) |
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Old Opeler
Join Date: Jun 2003
Location: New Zealand
Posts: 5,686
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Nice one, Otto!
D squared is FOUR times bigger than R squared .... so your formula quickly gives the displacement of a FOUR cylinder motor!
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GTJim Opel Owner since last Century! Copyright © 2000-2009 J D Henry All Rights Reserved |
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#7 (permalink) | |
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Old Opeler
Join Date: Jun 2003
Location: New Zealand
Posts: 5,686
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D = Bore Size!
"piston size" is very close to bore size so makes very little difference to the answer BUT means you have to pull a piston to measure it instead of just getting the size of the bore!
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GTJim Opel Owner since last Century! Copyright © 2000-2009 J D Henry All Rights Reserved |
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#8 (permalink) |
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6,000 Post Club
Join Date: Aug 2002
Location: Imperial Beach, CA South of San Diego
Posts: 6,054
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Nobody is correct in his thinking to use the bore size in this equation, but cylinder wear comes in to play also, so multiple measurements need to be taken and averaged out. Measuring the pistons, which is supposed to be done 2.5" below the oil ring groove 90 degrees from the wrist pin, could be a problem if the pistons were cam ground. Which means they are elliptical not completely round. Also, the rings do take up space between the piston and cylinder wall, although supposedly only .0012" it does add to the total displacement if only by a few CCs. Anything to throw garbage into the mix, and keep you guys thinking.
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Ron 72 GT 3.4L V-6/T-5/ZF posi - almost done - Just need AC installed. ![]() 75 Chevy monza 5.7L/TH350/Auburn 3.08 posi - Next |
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#9 (permalink) | |
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Cunning Linguist
Join Date: Mar 2002
Location: Plano, TX 75074
Posts: 4,441
Real Name: Otto
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Was really just trying to point out that you don't have to halve the bore (radius), square it and then multiply it by pi and times four to calculate the four cylinder total bore area. (D/2)² = (D²/4) x 4 (cylinders) = D²! I digress.
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1960: ♥ '61 Rekord PII 1.7 3S 3.9 ♥ '69 Kadett LS 'sprint' 1.9 3A 3.18 1970: ♥ '70 GT 1.9 4S 3.44 ♥ '72 GT 2.2SSD 5S 3.44 ♥ '72 GT 2.4FI 5S 3.44P 1980: ♥ '85 Bitter SC 3.9FI 5S 3.44P 2000: ♥ '09 Solstice GXP Coupe 2.0 SIDI VVT Turbo 5S 3.73P |
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#10 (permalink) |
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No Access
Join Date: Nov 2003
Location: in transit
Posts: 3,873
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I agreed with the equasion and it makes perfect sense. I was just thinking and asked what seemed like a stupid question on my part. It was meant to be a good way to determine total displacement and it is. The D value piston vs. bore is roughly .012 so as motors are classed pretty roughly anyway it doesn't matter when you factor that in. It's only when you start splitting hairs to go from a say a 2.0 to a 1.997, (just random numbers). My last one CCs at 1.992 but I call it the 2.0. Anybody out there with a 1.897 should agree.
Last edited by tekenaar; 04-26-2007 at 04:07 PM. Reason: sence? |
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