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Old 08-10-2008, 06:17 AM   #1
col5555
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Default Rod length dilema

Hi,
I would like to order some Eagle rods for a 2.35 build I have in the works. I will be using a EJ20 sleeved to a 2.2 bore size with a late model EJ25 crank.
Now my dilema is the Eagle rods come in two sizes 5.137 and 5.181 if my memory serves me correct. As I have not decided which pistons to use as yet(either WISECO or CP) what would be the compression outcome if I used the WISECO EJ22 hybrid pistons which are designed around using 2.5 crank and rods with the shorter EJ20 Eagle rods.
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Old 08-10-2008, 10:47 AM   #2
Dom'sGurl
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I think you are going about this all wrong.

If you are going to choose a rod, be sure it is the length the piston is designed for. Otherwise you have 1mm of clearance you are either gaining or losing. That 1 mm makes a huge difference in more than just compression ratio.

My strongest recommendation is to get the longer rods and use the correct pistons.

Longer rods are SO much better in SO many ways. There is no benefit to running the shorter rods.
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Old 08-10-2008, 10:54 AM   #3
MS WRX
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Cobb Ti long rods ftw
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Old 08-11-2008, 12:10 AM   #4
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Quote:
Originally Posted by MS WRX View Post
Cobb Ti long rods ftw


match the pistons and rods together. wiseco tells you which lenght rod the piston is supposed to be used with...
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Old 08-12-2008, 11:17 AM   #5
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Unless you are building something custom and you know what you're doing then go with the standard rod length that matches a standard piston. If you go with a longer rod, and don't relocate your wrist pin, or alter the crank, then your quench will be all wrong or worse the piston will actually hit the head.

There is an optimal amount of quench and you shouldn't mess with it too much. If you don't know what I'm talking about I rest my case

5.137 rod with a standard piston and you are good to go.

Thanks,
Phil
www.elementtuning.com

Last edited by Element Tuning; 08-12-2008 at 01:08 PM.
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Old 08-12-2008, 12:40 PM   #6
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Quote:
Originally Posted by Element Tuning View Post
Unless you are building something custom and you know what you're doing then go with the standard rod length that matches a standard piston. If you go with a longer rod, don't relocate your wrist pin, or alter the crank, then your quench will be all wrong or worse the piston will actually hit the head.
the first part I agree with completely...but if you either add rod or add crank you have to shorten the compression height or else you will hit the head!!
79mm stroke and 130.5mm rod...add 2mm to the rod (the infamous long rod ) and you have to pull 2mm from the compression height of the piston.

of course you can do combinations in-between too
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Old 08-12-2008, 01:04 PM   #7
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i'd like to throw some theoretical questions into the mix.what is the "long" rod length based on. common theory says the stroke to rod length proportion of the 2.0L is "perfect" to eliminate losses from piston to bore thrust and allow quick rev. if you crunch the numbers, dosen't 2.5 79mm stroke require around 5mm to be in proportion? or is the 2mm a compromise. what if you throw an 80mm stroke into the mix, can you get longer than 2mm over. i like the cobb ti pieces, just don't like trey. anyone else doing custom lengths in ti? i agree with homemadewrx, weisco seems pretty on top of the pistons, plus higher silica content for street engines (not as much clackety-clack like the je full race stuff).
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Old 08-12-2008, 01:09 PM   #8
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Quote:
Originally Posted by Homemade WRX View Post
the first part I agree with completely...but if you either add rod or add crank you have to shorten the compression height or else you will hit the head!!
79mm stroke and 130.5mm rod...add 2mm to the rod (the infamous long rod ) and you have to pull 2mm from the compression height of the piston.

of course you can do combinations in-between too
I noticed my wording was unclear so I edited but yes I agree with you. What I meant was that the crank and or the piston needs to be modified with a longer rod.

Thanks,
Phil
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Old 08-12-2008, 02:40 PM   #9
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Quote:
Originally Posted by oldskoolWRX View Post
i'd like to throw some theoretical questions into the mix.what is the "long" rod length based on. common theory says the stroke to rod length proportion of the 2.0L is "perfect" to eliminate losses from piston to bore thrust and allow quick rev. if you crunch the numbers, dosen't 2.5 79mm stroke require around 5mm to be in proportion? or is the 2mm a compromise. what if you throw an 80mm stroke into the mix, can you get longer than 2mm over. i like the cobb ti pieces, just don't like trey. anyone else doing custom lengths in ti? i agree with homemadewrx, weisco seems pretty on top of the pistons, plus higher silica content for street engines (not as much clackety-clack like the je full race stuff).
the limiting issue for our EJ is our short deck height...so working around it is the issue...
long rod it based on the rod to stroke ratio, not the actual rod lenght. So, you are correct.
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Old 08-15-2008, 01:23 PM   #10
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I would like to know what rod lenght to choose from 5.138 or 5.181 ?, thats what Pauter is offering for EJ25.
For a ej257 with only CP piston .WrX head .
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Old 08-15-2008, 01:34 PM   #11
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I just bought K1 Technologies 5.180" rods (H-beam), just to let you know that there are alternate less expensive options.
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Old 08-15-2008, 01:42 PM   #12
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i know the pauter are pretty expensive at 800$ for a 4 set , eagle is at 365$ for 4 set ...
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Old 08-15-2008, 02:34 PM   #13
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for an EJ257 you want the 5.138, that's assuming you bought pistons for an EJ257...the NA subies has a longer rod and a shorter compression height on their pistons. Hence the two rod lengths and different pistons being available.

Quote:
Originally Posted by vulpina View Post
i know the pauter are pretty expensive at 800$ for a 4 set , eagle is at 365$ for 4 set ...
there's a reason for that too...
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Old 08-15-2008, 04:51 PM   #14
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I have been looking at the Manly Turbo Tuff 5.141” Rods but it doesn’t seem like Weisoc makes a piston for that application.
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Old 08-15-2008, 09:28 PM   #15
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Well, that's only 0.003" difference, I'm sure you can use them as if they were 5.138" rods.
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Old 08-15-2008, 10:33 PM   #16
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Thanks for the advice. the manly piston suggested for the 5.141" rod has the same Comp Height. as the wiseco’s

Boy do I have a steep learning curve ahead of me.
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Old 08-16-2008, 11:31 AM   #17
Dom'sGurl
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Quote:
Originally Posted by Kosmic View Post
I just bought K1 Technologies 5.180" rods (H-beam), just to let you know that there are alternate less expensive options.
I have a set of those as well. I modify those rods to have piston oil squirters.
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Old 08-18-2008, 12:59 PM   #18
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Quote:
Originally Posted by Dom'sGurl View Post
I modify those rods to have piston oil squirters.


I order mine that way
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