con rod research
Well since I started looking at different pistons I decided to do some research to find a con rod with near same sizes as ours or the pistons I may use and stock big end \ length
I've found the A20\B20 honda rods use same size big and small diameter and is longer by 5mm CA18DET rods have same big and little end and length as stock con rods. I will update this as I find more info. |
The real question is,... why?
There is no reason to get a longer rod. Are you going to make 5mm shorter custom pistons? You're trying to solve a problem that does not exist. How can CA18DET PISTONS be the same length as CON RODS? |
heh didn't notice that. fixed. Not looking for a longer rod.
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Originally Posted by falcon
(Post 694887)
The real question is,... why?
There is no reason to get a longer rod. |
Originally Posted by Savington
(Post 695244)
Plenty of reasons to lengthen the rods with a stock crank. Less piston speed, more RPM capabilities, and better rod reliability to name a few. Longer rods let you shift the wrist pin up in the piston and improve the rod ratio of the motor. 5mm is a bit excessive since you'll interfere significantly with the oil control ring, but 3-4mm is doable and has been done.
OP, sometimes the rod width can be narrowed a hair at the bigend but not always. Custom pistons will be needed, not a big deal. |
b16a rods are 1-2mm longer from the specs I've seen with the same big end size
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There is a rather long thread on this topic where some dude used honda rods in his BP block. I will not search for it as I am lazy
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BMW M20B27 stock con rods
BE dia 48mm PE dia 22mm CTC 130mm |
anyone aware of a con rod with a 140mm ctc and a 48mm big end?
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Originally Posted by JKav
(Post 695257)
+1. Longer rods have nice cascade effect. Who has done it on a BP?
OP, sometimes the rod width can be narrowed a hair at the bigend but not always. Custom pistons will be needed, not a big deal. The only complication is that the wrist pin gets elevated into the oil control ring, which requires a bit of trickery to make work, but it's doable. |
I think I may found some, I Got to check the M42\44 motors from bmw
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I know MarkP talked about using Honda rods and pistons back in the day.
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Originally Posted by Savington
(Post 695244)
Plenty of reasons to lengthen the rods with a stock crank. Less piston speed, more RPM capabilities, and better rod reliability to name a few. Longer rods let you shift the wrist pin up in the piston and improve the rod ratio of the motor. 5mm is a bit excessive since you'll interfere significantly with the oil control ring, but 3-4mm is doable and has been done.
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m42\44 140mm ctc
big end 48mm pin end 22mm |
BMW con rod, miata crank
http://img9.imageshack.us/img9/2940/dscn2433q.jpg By techsalvager at 2011-04-18 http://img705.imageshack.us/img705/783/dscn2434x.jpg By techsalvager at 2011-04-18 |
You can't elevate the wrist pin 7mm in the piston (8mm once you account for the additional wrist pin diameter). What's your plan for that?
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I dunno but if those rods are from an i6, it's "buy two sets, get one free" for the miata.
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Originally Posted by Savington
(Post 715996)
You can't elevate the wrist pin 7mm in the piston (8mm once you account for the additional wrist pin diameter). What's your plan for that?
They are 130mm CTC, which is shorter than stock rods If you get the rods out of a 325i e30 they are 135mm CTC I don't plan to do anything with them, just documenting that they do indeed fit on the crank with no issues |
Originally Posted by Techsalvager
(Post 716083)
Those bmw rods in the picture are out of a 325e e30
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stock piston, bmw rod
http://img833.imageshack.us/img833/4060/dscn2403g.jpg Uploaded with ImageShack.us note bmw rod uses bigger wrist pin |
It's common to bush rods for a performance build, easily done and you can get it to the size required. The rod "looks" heavy, did you weigh it? How is the side clearance when you had it on the crank?
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following..
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you could have the rod bushed differently.... but you mentioned that it is shorter than stock BP
edit: aaaaaaaand i didnt see page 2. |
BTW, a little quick math says that 400hp on 6 cyl isn't that impressive...
i.e. 400 / 6 = 66.66 hp/rod 66.66 * 4 = 266 So that's the ball park of power per rod that kills miata rods, having 2 more cylinders helps spread the load a bit :) Your buddy needs to turn the boost up some more, imo :) |
Originally Posted by shlammed
(Post 716150)
you could have the rod bushed differently.... but you mentioned that it is shorter than stock BP
edit: aaaaaaaand i didnt see page 2. Of course a 1.8l person can research for their own setup as well for pistons |
Originally Posted by ianferrell
(Post 716154)
BTW, a little quick math says that 400hp on 6 cyl isn't that impressive...
i.e. 400 / 6 = 66.66 hp/rod 66.66 * 4 = 266 So that's the ball park of power per rod that kills miata rods, having 2 more cylinders helps spread the load a bit :) Your buddy needs to turn the boost up some more, imo :) Now, he is using a Borg Warner S376 and is aiming for a low 6 in the 1/8th. Should be on 30-40psi. AAAAAAAAAAAAAAAAAND he will still be using the same bottom end with the same stock E-car rods. |
Originally Posted by viperormiata
(Post 716094)
A friend of mine uses a E-car bottom end with a I-car head. 400hp/480tq @ 25psi on the stock E-car bottom end. Those rods are super tough. Good find, the M20 is a seriously underrated motor.
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Just got all 6 rods for free from 325e m20(thank you e30 buddies)
I'll hold on to them and see what happens with this thread. I'm all about experimenting :giggle: |
Originally Posted by Alta_Racer
(Post 716123)
It's common to bush rods for a performance build, easily done and you can get it to the size required. The rod "looks" heavy, did you weigh it? How is the side clearance when you had it on the crank?
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Originally Posted by viperormiata
(Post 717531)
Just got all 6 rods for free from 325e m20(thank you e30 buddies)
I'll hold on to them and see what happens with this thread. I'm all about experimenting :giggle: |
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