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Old 17-09-2017, 02:46 PM
franky franky is offline
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rod stroke ratio

84mm bore

Compression distance 1.379”

Dome height 0.035”

0.6cc positive dome

Intake valve pocket 0.120” deep x 12 degrees

Exhaust pocket 0.110” deep x 12 degrees.



I'm using an l24 block, l28 crank, l24 length rods. The pistons were designed as a 'cheat' gives me 2627cc. Big(ger) valve e31 head. 39cc. 10.5:1 cr, 294 deg cam

This gives me a rod/stroke ratio of about 1.68 against a 1.8ish as standard. The way I understand it this is slightly 'better'? Or have I understood wrong?
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Old 17-09-2017, 07:22 PM
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tel240z tel240z is offline
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Yes Franky this is better i use an l28 block and crank with 240z rods
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Old 17-09-2017, 07:27 PM
franky franky is offline
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Yes, it's the pin height in these pistons as they were used to create a naughty 'cheat' engine spec
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Old 17-09-2017, 09:13 PM
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What is this - sex by numbers ?
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Old 17-09-2017, 09:43 PM
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L28 rods with l28 crank have a 1.65ish ratio.
Not much in it.
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Old 18-09-2017, 10:01 AM
SKiddell SKiddell is offline
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We alter the pin height to compensate for using different rod lengths to ensure they sit at the correct height in the block yes but pistons have no influence in rod/stroke ratio.

Could you tell me what a "naughty" cheat engine is ?
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Old 18-09-2017, 10:26 AM
franky franky is offline
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Quote:
Originally Posted by SKiddell View Post
We alter the pin height to compensate for using different rod lengths to ensure they sit at the correct height in the block yes but pistons have no influence in rod/stroke ratio.

Could you tell me what a "naughty" cheat engine is ?
Yes, from my understanding it'll help with the feel of the engine I want also.

The pin height isn't at the same point as a standard piston, so for the same swept volume you'd argue that they do influence the rod/stroke ratio as you change the rod to compensate?
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Old 18-09-2017, 01:07 PM
SKiddell SKiddell is offline
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Quote:
as you change the rod to compensate?
Not the right way of building an engine, the bore, stroke and rod dictate the size and characteristic of the engine, so you select a stroke and bore to get a capacity, then plan a stroke/rod and bore/stroke ratio (IE what the engine is for, race, street, pulling up trees) then design the pin height to set the piston in the correct position in the bore, if your changing the rod to compensate for incorrect pin height then that's counterintuitive
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Old 18-09-2017, 01:13 PM
franky franky is offline
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Quote:
Originally Posted by SKiddell View Post
Not the right way of building an engine, the bore, stroke and rod dictate the size and characteristic of the engine, so you select a stroke and bore to get a capacity, then plan a stroke/rod and bore/stroke ratio (IE what the engine is for, race, street, pulling up trees) then design the pin height to set the piston in the correct position in the bore, if your changing the rod to compensate for incorrect pin height then that's counterintuitive
Agreed, I Just meant it does have an effect on the ratio...
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Old 18-09-2017, 03:07 PM
SKiddell SKiddell is offline
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Rod 138mm
Stroke 83mm
Pin height 35mm
Ratio 1.66

Rod 138mm
Stroke 83mm
Pin height 1,000,000mm
Ratio is still 1.66

The clue is Rod/Stroke ratio, not Rod/Stroke/Pin height ratio
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Old 18-09-2017, 03:47 PM
franky franky is offline
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Quote:
Originally Posted by skiddell View Post
rod 138mm
stroke 83mm
pin height 35mm
ratio 1.66

rod 138mm
stroke 83mm
pin height 1,000,000mm
ratio is still 1.66

the clue is rod/stroke ratio, not rod/stroke/pin height ratio
:d
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