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  • Aluminum Rods

    Anyone here have experience with some of the newer alloy'd aluminum rods gaining popularity with the evo guys? I'm seeing reports of 10-15k miles on these without issues. And almost all of the places machining them will build you a custom set for roughly the set of what Carrillo rods run.
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  • #2
    Aluminum as a rod material is pretty nice given that the low modulus softens the impact of combustion events to the big end rod. The fatigue life is the only gotcha, and in that case, it doesn't really matter too much what alloy you go with. Any of the structural alloys will fall down to the 9-12 ksi range at 1e6 to 1e7 cycle range on the S-n curve (look it up good info there on fatigue life/endurance limit - which Al technically does not have at infinite cycles).

    I'm betting the fancy alloys are just a way to tout that they hold a ton of power when new, then upcharge a high premium. They'd be just fine being made out of 2024 or something like that that's not too outrageously priced.
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    • #3
      I'm wondering if I can get 1-2 season of use out of them since people are getting 10-15k of mixed street and track use on evos. If so, I might be able to justify the maintenance of replacing them before failure due to the weight savings. I'm in the process of building my 2.2 bottom end and thinking of giving it a go.
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      • #4
        How high are you planning to rev? Over 9k RPM it might be worth it, otherwise I'd just run aftermarket steel rods. Lots of SR20-Forum guys rev their NA cars out to over 9k with a VE head, some even do it turbo as well.
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        DefSport Koni Sleeve and Spring Perch Buy!!!
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        • #5
          Well, that is going to depend on what turbo I end up going with I guess, but basically I'm planning a VE head similar to what mazworx is doing 11,000 rpm on (big valve, deshrouding valve, aftermarket springs with higher spring rates, etc). I'm building a long rod bottom end though using modified h22 rods (narrow the big end a bit ala Mike Kojima). Using them with a custom piston brings the rod stroke ratio up to 1.66:1 from 1.58:1 and hopefully helping with some of the loads at high rpm. That's why I'm thinking that the AL rods may be perfect to try with this setup.
          Last edited by PerilousActs; 03-23-2014, 04:56 PM.
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          • #6
            Yea, they could be very useful over 9k RPM. Just stick to a reasonable replacement schedule and don't deviate just because things seem fine right then.
            '18 Chevrolet Volt - Electric fun hatch for DD duty!


            DefSport Koni Sleeve and Spring Perch Buy!!!
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            • #7
              Not that this is entirely applicable to your question, but on the TF dragster, we run our aluminum rods until they they get pounded to short to run, or have fatigue cracks on the serated caps. We have a jig made up to monitor/log all of the connecting rod lengths that we have in service.

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              • #8
                I went ahead and ordered a set. Cost me $689 with my specs. So still cheaper than I would pay for Carrillo's. Ordered them from http://rrconnectingrods.com/.
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                • #9
                  Originally posted by PerilousActs View Post
                  I went ahead and ordered a set. Cost me $689 with my specs. So still cheaper than I would pay for Carrillo's. Ordered them from http://rrconnectingrods.com/.
                  Doesn't Carillo make titanium rods?

                  or is that Cunningham? Or both?
                  What's the price difference between steel, aluminum, and titanium, if anyone knows? Just a little curious...

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                  • #10
                    I believe Ti rods are in the $2kish range for a 4 cylinder from when I was looking the other day. Most places that do AL do titanium from what I've seen. There's a lot of info on both on evolutionm actually. I was pretty surprised, but there's a lot of big budget evo builds so I guess it makes perfect sense.
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                    • #11
                      Originally posted by PerilousActs View Post
                      I believe Ti rods are in the $2kish range for a 4 cylinder from when I was looking the other day. Most places that do AL do titanium from what I've seen. There's a lot of info on both on evolutionm actually. I was pretty surprised, but there's a lot of big budget evo builds so I guess it makes perfect sense.
                      Ya, I saw a build from, I think Greece a few yrs ago; these dudes had their own billet block they machined, beryllium-laced pistons, and their own billet head that didn't require a gasket (I think?), running like 55+ lbs of boost, IIRC. Anyway, back to Ti rods, damn, that's more expensive than I thought they were... guess Al rods are good enough diploma for me.

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                      • #12
                        Yea, pure beryllium pistons and MMC rods that were beyond baller. That engine probably had $20k in just materials alone. Pretty impressive stuff. But I can think of a better engine to spend it on than a 4G63 at that point! I think I would just drop a Judd V8 into something for that sort of coin like this:

                        https://www.youtube.com/watch?v=ZsGTBWmN41s
                        '18 Chevrolet Volt - Electric fun hatch for DD duty!


                        DefSport Koni Sleeve and Spring Perch Buy!!!
                        http://www.nissanroadracing.com/showthread.php?t=5902

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                        • #13
                          Originally posted by Def View Post
                          Yea, pure beryllium pistons and MMC rods that were beyond baller. That engine probably had $20k in just materials alone. Pretty impressive stuff.
                          I believe these are some of the pics... IDK where I saw the entire engine build though, sadly.

                          http://www.airsociety.net/forums/sho...y-is-no-object


                          /threadjack

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                          • #14
                            We use the R&R aluminum rods in all of our high powered EVO engines. They do help the bearings survive high rpm and high power use. We have found that the service life of the rods can be increased by keeping oil and coolant temperatures on the low end of the spectrum. We typically run 160 thermostats.

                            Also make sure whatever machine shop you are using is familiar with aluminum rods as there are some inherent quirks when using/machining the block for them. The big end will need to be torqued to spec multiple times before the measurements become repeatable.

                            You will likely have to notch the block for them to fit, and clearance between the top of the rod and piston are a often overlooked measurement. We shoot for between .040 and .060.

                            zack

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                            • #15
                              When I worked at the local shop, we'd use BME forged aluminum rods in our drag engines. Not a ton of miles got racked up, but lots and lots of practice and competition drag runs. Never had any problems except when an oil pump failed. Bearing contacted crank, and instead of spinning (bearings are pinned in place), it just seized and the rod snapped.
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