Anyone seen rods lightened this way? Dont know if this is ok or not. I know someone (not me) went to a lot of work.
Anyone seen rods lightened this way? Dont know if this is ok or not. I know someone (not me) went to a lot of work.
GCR: C (vee) 5.C.6: Connecticut rods with bolts and small end bushing minimum weight = 425.0 grams ...
GCR: C (vee) 5.D.5: Where minumum weights are specified, any lightening is permissible provided the original part complied with thedemensional restrictions set forth.
It's legal if it's at least 425 grams.
1993 Citation FV
NEFV - 2022 Champion
NERRC - 2022 Champion
All of the 'meat' of the structure on the big end is GONE. I've never seen it done quite that thoroughly and I would NOT recommend using them. I doubt seriously that there is enough structure left to keep them from elongating (and blowing your your engine) at anything higher than, maybe 5500 RPM if that.
YMMV,
Steve
Steve, FV80
Racing since '73 - FV since '77
Thanks for the input. I'll throw them on the ever growing scrap pile.
I use the local metal recycling center .. they actually PAY ME for scrap metal .. not much, but better than having to PAY SOMEONE ELSE to get rid of it
Steve
Steve, FV80
Racing since '73 - FV since '77
The ribs on the bottom end are gone. Cheapest way to remove weight and probably thinking it is the best place to reduce rotating mass.
Both idea's are faulty. I wouldn't use them.
Just thinking outloud here, aren't all the major forces on the opposite side of this area? Intake stroke would have a little, but that's about it.
1993 Citation FV
NEFV - 2022 Champion
NERRC - 2022 Champion
delete. Duplicate
That heavy turd piston decelerating as it approaches TDC at high rpm is putting a tremendous load on the con-rod cap and rod bolts.
That said, if those rods are of legal weight I'd use 'em just to see what kind of gains can be had (if any). If they fail the damage isn't exactly prohibitively expensive.
1) Why did VW provide ribs on the rod cap that was only going to see 4000 rpm? Did they know something that some Vee engine builders have failed to recognize.
2) Investing in a set of Crower rods is one of the best things you can do to improve engine reliability.
Brian
maybe i should READ the rules
- Connecting rods with bolts and small end bushing minimum weight = 425.0 grams. Crower part#SP93280B is allowed as a direct replacement connecting rod but must meet the same minimumweight requirement as the OEM part.
"Because they wanted those engines to last 100x longer than..."
4000rpm occasionally Vs 6500 all the time. Very significant difference from one to the other.
Sure, it's up to the individual to determine the risk. IMO, it's not worth it. Those rods were most likely done by someone that had little knowledge of what they were doing.
The pictured rods look like what we used to use in our 948 HP Sprite engines. Worked great to over 9000 rpm as long as you were willing to replace rod bearings every two race weekends (ya gotta love oil dripping on your face!).
Marty
There is quite a bit of information available on lightening rods. Perhaps someone wished to start from scratch and prove what is known to be false.
More likely they did not know what they were doing. Show me some pictures of a rod built by any of the V engine builders that looks like that and I'll rethink my evaluation.
Anything is possible. Some things are more likely than others.
Vee engine builders used trial an error to get where they are on rod lightening. Even with that said there is really no way to know what caused a rod to fail. How do you tell a lubrication failure from a rod that actually broke all on its own? Maybe a lubrication failure develops while the rod is physically deforming but not breaking (ovaled big end).
If you want to know what a FV rod should look like, then check out the Crower rod. It was developed using FEA, structural element analysis. It tells you exactly where to allocate your material and in what shape. They are also surface treated to reduce stress, which is something the FV engine builders do not do.
Brian
Sometimes people too close to the trees can't see the forest. Professional engine builders aren't concerned with getting you that last .05% HP if their engine is going to go kablooey in what the market determines is too short of time period.
FV engines make 16-17HP per cylinder. A maximum piston velocity of around 24m/s. Mean piston speed under 15m/s. A piston weight under 12 ounces. Doesn't require near as much rod as we think until we demand they last tens or fifty-ish hours.
"if their engine is going to go kablooey"
You're making my point.
Google Crower SP93280B and go to the Crower page.
Brian
Substantial being in the eye of the beholder...
With Brian's help I found the picture of the Crower VW rod. It has a single rib that I would classify as substantial when measured against the pictured rods from the original poster. Those rods appear to have all the ribs removed. They look perfectly flat and smooth.
With that I'll let sleeping dogs...
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