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Rod length and compression 

 

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 Post subject: Rod length and compression
Posted: Wed Jun 04, 2008 1:51 pm 
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I was wondering in my wondering time this morning, if you could fit AU pistons onto E series con rods? since the e series rods are .2 or so of an inch shorter than AU rods, this would be a pretty easy way of de-compressing a 4 ltr for turbo's or superchargers wouldnt it? it would also rev slightly better due to being squarer, and the FI would make up for the slightly lower torque down low.

how much compression would one loose if the stroke is reduced by that much? would it get it under the 8.5:1 mark?

If it fell too low you could shave off the head a bit to bring it back up...

wonder what the literage would be with the combo. Bet its been done if it can be done. anyone heard anything of it?

 

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Posted: Wed Jun 04, 2008 5:45 pm 
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dude just save you self the probs
and get a decompresson plate/gasket

 

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 Post subject: Re: Rod length and compression
Posted: Wed Jun 04, 2008 5:47 pm 
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More Grunt wrote:
I was wondering in my wondering time this morning, if you could fit AU pistons onto E series con rods? since the e series rods are .2 or so of an inch shorter than AU rods, this would be a pretty easy way of de-compressing a 4 ltr for turbo's or superchargers wouldnt it? it would also rev slightly better due to being squarer, and the FI would make up for the slightly lower torque down low.

how much compression would one loose if the stroke is reduced by that much? would it get it under the 8.5:1 mark?

If it fell too low you could shave off the head a bit to bring it back up...

wonder what the literage would be with the combo. Bet its been done if it can be done. anyone heard anything of it?


this would be the better way to go to make full turbo only motor.

 

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 Post subject: Re: Rod length and compression
Posted: Wed Jun 04, 2008 8:41 pm 
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More Grunt wrote:
I was wondering in my wondering time this morning, if you could fit AU pistons onto E series con rods? since the e series rods are .2 or so of an inch shorter than AU rods, this would be a pretty easy way of de-compressing a 4 ltr for turbo's or superchargers wouldnt it? it would also rev slightly better due to being squarer, and the FI would make up for the slightly lower torque down low.

how much compression would one loose if the stroke is reduced by that much? would it get it under the 8.5:1 mark?

If it fell too low you could shave off the head a bit to bring it back up...

wonder what the literage would be with the combo. Bet its been done if it can be done. anyone heard anything of it?


you'd lower the comp to far and create more problem then it solves.

the engine will not be any 'squarer'. that is determind by the stroke and bore. not by the installed lenght of the rod and piston
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 Post subject: Re: Rod length and compression
Posted: Thu Jun 05, 2008 12:10 am 
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tickford_6 wrote:
More Grunt wrote:
I was wondering in my wondering time this morning, if you could fit AU pistons onto E series con rods? since the e series rods are .2 or so of an inch shorter than AU rods, this would be a pretty easy way of de-compressing a 4 ltr for turbo's or superchargers wouldnt it? it would also rev slightly better due to being squarer, and the FI would make up for the slightly lower torque down low.

how much compression would one loose if the stroke is reduced by that much? would it get it under the 8.5:1 mark?

If it fell too low you could shave off the head a bit to bring it back up...

wonder what the literage would be with the combo. Bet its been done if it can be done. anyone heard anything of it?


you'd lower the comp to far and create more problem then it solves.

the engine will not be any 'squarer'. that is determind by the stroke and bore. not by the installed lenght of the rod and piston


ahh but wouldn't an aduquatly shaven head raise some compression to compensate for the lower compression?? or using a polished 3.9 head to also compenstate

 

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Posted: Thu Jun 05, 2008 12:25 am 
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lol the actual burning question that i was really wanting answered was can you put AU pistons on EL rods... i mean in the way they connect together.

coz without that answered its just conjecture.

Also is there a way to calculate a .2 inch drop (half a centimeter) in piston height vs how much compression lost?

and if so, how much head shave needed to bring it back to around the 8.5:1 level.

who can do the engineering physics maths thingy bit?

cos dropping to around 8:1 for FI would be ideal to get bigger boost, better than decomp plates and gaskets that can fail readily enough.

if it hasnt been done there must be a reason, i just want to hear a real reason why it hasnt.

not just probablies.

 

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 Post subject: Re: Rod length and compression
Posted: Thu Jun 05, 2008 12:35 am 
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Google "quench", and thats your reason why it's never been done.

 

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 Post subject: Re: Rod length and compression
Posted: Thu Jun 05, 2008 12:36 am 
Getting Side Ways
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tickford_6 wrote:

the engine will not be any 'squarer'. that is determind by the stroke and bore. not by the installed lenght of the rod and piston


good point this, didnt think of it both ways lol, sure enough the piston wont travel as far up but it would travel further down, creating the same swept capacity, thanks for highlighting that.

would have to make sure there is still cylinder bore half a centimeter lower than usual...

 

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 Post subject: Re: Rod length and compression
Posted: Thu Jun 05, 2008 12:41 am 
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Steady ED wrote:
Google "quench", and thats your reason why it's never been done.


I almost knew that it would be you who would know the reason why it wouldnt work, thanks man. clears that little wonder up.

should have just pm'd you and saved the forum space lol.

 

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Posted: Thu Jun 05, 2008 1:20 am 
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I don't know that much, only from reading books!

 

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