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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Mon, Mar-23-2015, 01:26:47 PM   #1
Obioban
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Exclamation Potential downside to ARP connecting rod bolts

A while back there was a discussion on rod bearings and bolts.

(http://www.m3forum.net/m3forum/showthread.php?t=461780)

At the time I said I was sticking with stock because it is bulletproof so there's no room to improve/upgrade.

Anyway, here's a further reason (and evidence of it) to stick with stock. The additional torque with the ARP's can distort the assembly, making it slightly ovular instead of circular.

This post from this thread.

Yes, S65, but I've never seen it measured so specifically before and after.

Quote:
Originally Posted by regular guy View Post
Part-1: Rod bolt clamping pressure:

M3post reader, kawasaki00 measured the OEM rod bolt clamping pressure, along with the clamping pressure of two different types of Carrillo rod bolts. As he discovered, the OEM rod bolts offer far more clamping pressure vs. Carrillo rod bolts, and it's believed the clamping pressure (or lack thereof) may cause the rod big end bore distortion and lead to increased bearing clearance at 90-degrees. Increased bearing clearance is a good thing, but bore distortion is not. I'm pretty sure that increased clearance at the cost of bore distortion is not advised. However, I'll let kawasaki00 and the other engine experts comment on that.

Here's the rod bolt clamping force data generated by kawasaki00:



Notes:
Carrillo WMC bolts @ 50 degrees, 0.006 inch stretch
Carrillo SPS bolts @ 54 degrees, 0.0065 inch stretch


Part-2: Rod big-end ovality with different rod bolts:

With the rod bolt clamping data above, the next test will see which rod bolt creates the roundest circle. This will test for the "ovality" of the rod big end bore by checking the measurements at seven different points around the circle. Although the ARP-2000 and ARP-625 rod bolts were not tested above, I believe the two Carrillo rod bolts are of similar quality and specifications. (kawasaki00 can comment on that.)

For the most part, the OEM rod bolts create a near perfectly-round circle. Four of the eight rods I tested were 1/10000th of an inch or less out of round. That's probably what you would expect since these rods were honed (the process of making the circle round) with OEM rod bolts.

The ARP-2000 rod bolts did not create a perfectly round circle. The ARP-2000 rod bolts, with less clamping pressure produced bore distortion at 90-degrees. The bore distorts larger towards 90-degrees, and this would explain Malek's and Van Dyne's measurement of increased clearance when using the aftermarket ARP bolts. But is this enough to matter? Kawasaki00 told me privately, yes, this is a significant amount of ovality, and he would not use these bolts unless he was also able to rehone the connecting rod big ends to make them round again.

The data:

OEM Rod Bolt Measurements:

Torque Specifications: 20 Nm + 130 degrees



Ovality:




ARP-2000 Rod Bolt Measurements:

Torque Specifications: 45 Ft-Lbs



Ovality:



Graph(s):



Next Steps:

Next week, ARP-625 bolts will arrive. I will repeat this measuring process with the ARP-625 bolts and post the results when they are available.

Thanks to Malek for loaning me the ARP-2000 rod bolts. Before returning them, I plan to measure bearing clearance.
So, there you go. Another reason to stick with the cheaper, bullet proof option when doing rod bearings-- stock



Edit: verified to be the same on the s54:

http://www.m3forum.net/m3forum/showp...8&postcount=72

Quote:
Originally Posted by AndrewLang View Post
I torqued the M11 stock bolts in a stock S54 rod with the 30nm > 70 deg angle and got a round bore within .0002". With oil the torque on the wrench read 68 ft/lbs.

I torqued the ARP 2000 M11 bolt in the same S54 rod gradually and measured the roundness of the bore. The bore got just as round as the stock bolt at .0068" of stretch. Spec is .0065" to .0070". This was 68 ft/lbs with the ARP lube. The ARP sheet says torque spec is 70ft/lbs.

I torqued the M10 stock bolts in a stock S54 rod with the 30nm > 105 degree torque and got round bores within .0002". This was between 62 and 66 ft lbs.

I torqued the ARP 2000 M10 bolts in the same rod and couldn't get the bore round until I stretched them .0075". This torque was about 68 ft/lbs. The ARP spec sheet says to torque these to 50 ft/lbs and .0065" to .0070".

Not really the results I was expecting.
Cliffs: on the s54, the arp's are 4x more expensive, provide less clamping force, don't solve any sort of problem with the stock bolts (as they don't have any), and provide a less round result than the stock bolts if installed with the crank in the engine (not part of an engine out build).
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Last edited by Obioban; Sun, Jul-24-2016 at 05:41:57 PM.
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Old Mon, Mar-23-2015, 02:22:02 PM   #2
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Default Re: Potential downside to ARP connecting rod bolts

Any good machinist using ARP hardware will always check the roundness prior to reassembly if they know what they're doing.

Mains and Rod hardware. If machinist doesn't even sound like they know to check, not getting my business at all.
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Old Mon, Mar-23-2015, 02:40:54 PM   #3
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Default Re: Potential downside to ARP connecting rod bolts

I never could justify the ARP bolts over stock, since there's a decent price savings, and there's no poor design or failures with the OE.. Why change out a part that's already well built?


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Old Mon, Mar-23-2015, 02:44:34 PM   #4
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Default Re: Potential downside to ARP connecting rod bolts

Interesting that the outcome is due to less clamping force from the aftermarket bolt.
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Old Mon, Mar-23-2015, 02:59:55 PM   #5
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Default Re: Potential downside to ARP connecting rod bolts

Quote:
Originally Posted by SneauxM3 View Post
Any good machinist using ARP hardware will always check the roundness prior to reassembly if they know what they're doing.

Mains and Rod hardware. If machinist doesn't even sound like they know to check, not getting my business at all.
Mostly people aren't using a machinist with these at all-- remove stock, replacing rod bearings, bolting back in with ARP.
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Old Mon, Mar-23-2015, 04:09:02 PM   #6
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Default Re: Potential downside to ARP connecting rod bolts

This is why I chose not to use the ARPs I have and bought a set of the OE rod bolts. Their instructions specifically mention that the rods must be resized. The other thing I don't like is that they use the same bolts and torque spec on the S54 and S50b32, despite the two engines having very different torque angles for the stock bolts.
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Old Mon, Mar-23-2015, 04:15:55 PM   #7
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Default Re: Potential downside to ARP connecting rod bolts

Quote:
Originally Posted by Obioban View Post
Mostly people aren't using a machinist with these at all-- remove stock, replacing rod bearings, bolting back in with ARP.
Well, that's the complete wrong way to do it. Do it right or do it twice. You should always check for round and in most cases will need to align hone the rods.
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Old Mon, Mar-23-2015, 04:18:42 PM   #8
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Default Re: Potential downside to ARP connecting rod bolts

Are the stock bolts Torque To Yield or in other words one time use? OR when refreshing rod bearings do we replace them "just because" and/or they might be fatigue in a sense?
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Old Mon, Mar-23-2015, 04:24:39 PM   #9
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Default Re: Potential downside to ARP connecting rod bolts

Quote:
Originally Posted by Tifosi Scuderia View Post
Well, that's the complete wrong way to do it. Do it right or do it twice. You should always check for round and in most cases will need to align hone the rods.
Bmw did not require that for the service action, and nearly all of those engines put in excess of 100k miles on those rods and bearings without running into issues. Removing the rods is a lot of extra work and potentially huge increase in cost that's not practical for us. Labor cost would be more than just buying another s54

The first post shows that at least on the S65, the OE rod bolts keep the bore circular.

Quote:
Originally Posted by M3_#67 View Post
Are the stock bolts Torque To Yield or in other words one time use? OR when refreshing rod bearings do we replace them "just because" and/or they might be fatigue in a sense?
The 03+ ones are torque to yield. The earlier ones presumably are not.
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Old Mon, Mar-23-2015, 04:27:11 PM   #10
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Default Re: Potential downside to ARP connecting rod bolts

Quote:
Originally Posted by terraphantm View Post
Bmw did not require that for the service action, and nearly all of those engines put in excess of 100k miles on those rods and bearings without running into issues. Removing the rods is a lot of extra work and potentially huge increase in work that's not practical for us. Labor cost would be more than just buying another s54

The first post shows that at least on the S65, the OE rod bolts keep the bore circular.
I'm not saying it that it is practical or the way I would do it. Personally, I would do OEM every time unless my engine was being completely rebuilt. It makes no sense to take the rods out otherwise. I am just saying, if you want to use ARP hardware, you need to know what all is involved.

OEM for me
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Discussing Potential downside to ARP connecting rod bolts in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)