FBM 1000Hp Forged Connecting Rods

[VSGTS14]

Originally Posted by Coheed

I see no reason why the factory rods can't handle 400whp for a good long time.

But these rods look great, and should be on anyone's list looking to make big power.

i agree. unless subaru put the weakest possible ones in there, then they should do what you said.
the OEM rods in the sti are strong. they are in my 510whp sti, because aftermarket are not needed.
but the point here is that if you're building a motor with new pistons, you will obviously buy new rods to go with it...so why buy oem when someone can buy something stronger for the same price?


but like you said. the OEM rods will most likely hold fine.

[serialk11r]

Did you guys do what one of the other companies did (I think it was Crawford?), raised wristpin, shorter piston, longer rod? These engines could use a little longer rods. A small change like that doesn't do much, but if you're making completely new parts it doesn't hurt to make that modification.

[SkullWorks]

scary stuff....less thrust area, less clearance for fillet radii on rod journal, not cracked, and you didn't even baseline the factory rods to determine weight before you set out to make replacements?

you also grooved (it appears from the pics) between the wrist pin oiling holes, thereby decreasing the surface area that supports the highest PSI force in the whole motor...

I'm really trying to reduce my A$$hole posts on the forums...but come on guys there are too many people with real experience to get by with so little forethought. I really hope you guys can clarify my concerns and not simply dismiss me as a hater, Irealize you stated that this motor magically doesn't need any accommodations for the angled split line...but you also acknowledged that angled split lines require extra precautions (i really really really favor cracked rods for angled split lines or at the least a Cummings-esque diamond lock tab

[FullBlown]

Originally Posted by SkullWorks

scary stuff....less thrust area, less clearance for fillet radii on rod journal, not cracked, and you didn't even baseline the factory rods to determine weight before you set out to make replacements?

you also grooved (it appears from the pics) between the wrist pin oiling holes, thereby decreasing the surface area that supports the highest PSI force in the whole motor...

I'm really trying to reduce my A$$hole posts on the forums...but come on guys there are too many people with real experience to get by with so little forethought. I really hope you guys can clarify my concerns and not simply dismiss me as a hater, Irealize you stated that this motor magically doesn't need any accommodations for the angled split line...but you also acknowledged that angled split lines require extra precautions (i really really really favor cracked rods for angled split lines or at the least a Cummings-esque diamond lock tab

We do not claim that we know everything about how to produce a connecting rod. The company that made these rods for us have been doing it for quite some time. I will get those answers for you.

The rods were baselined by the manufacturer and taken into consideration before making the new ones. Like I said we don't do them inhouse.

[SkullWorks]

Originally Posted by FullBlown

We do not claim that we know everything about how to produce a connecting rod. The company that made these rods for us have been doing it for quite some time. I will get those answers for you.

The rods were baselined by the manufacturer and taken into consideration before making the new ones. Like I said we don't do them inhouse.

I appreciate your honesty and forthcoming-ness (new word write it down)



Thank you!

[FullBlown]

Hope this answers your question. If it doesn't, please pm me and I can get you in touch with the engineer behind the rod and you can chat with him about your concerns.

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We have been designing, and making rods for all types of racing engines for over 20 years, and have a very good name, and success rate in the industry. How much thrust area does one need, all it is there for is to prevent side to side movement. The technology, and equipment for cracking caps is only available to OEM's, and is very expensive, and would not be economical in short batch runs to perform this operation, and with this method there is no chance for reconditioning a used rod. We redesigned this rod per the RPM / Horsepower requirements we were given at time of order, and the rod was designed to handle this amount. We only use Ampco 45 bronze which requires a substantial amount of lubrication to prevent galling, and this material has a much higher load rating, so decreasing the surface area will not hurt at all, as this rod is full grooved to get the oil directed to the part of the rod that has the highest load. A Cummins rod is at 45 degree angles parting line, and hollow dowel locators are not a good choice for this angle, as there is a large side load, but this rod only has a 15 degree parting line, and computer modeling tells us that there is no more load on the parting surface than with a straight cap rod.

[Silverdub]

Anybody has the weight of the stock rod for comparison? Just wondering, these look great btw

[ssteer]

The FA 20 crankshaft has four fully counterweighted throws. The bobweights have a certain weight and radius from the crank centerline. The math used for the last hundred years or so suggests half the weight of the piston/rod assembly is offset by the crank counterweights, for smoothest performance.

I get kind of worried when someone just makes a stronger rod and piston which usually weigh more, and leave the counterweights alone. Makes me think that little planning or understanding is being applied other than making things strong.

Like those Pauter rods - if bridges were made by X section girders, which are far less strong than I or H beams for the same weight per foot, our landscape would look a lot different. Because for the same safety factor you would have to use more material, meaning more weight. Then the crank counterweights would be way off optimum, and the engine gets the shakes.

Just the musings of an old mechanical engineer. Google engine balancing, don't take my word for it.

[cf6mech]

Originally Posted by ssteer

The FA 20 crankshaft has four fully counterweighted throws. The bobweights have a certain weight and radius from the crank centerline. The math used for the last hundred years or so suggests half the weight of the piston/rod assembly is offset by the crank counterweights, for smoothest performance.

I get kind of worried when someone just makes a stronger rod and piston which usually weigh more, and leave the counterweights alone. Makes me think that little planning or understanding is being applied other than making things strong.

Like those Pauter rods - if bridges were made by X section girders, which are far less strong than I or H beams for the same weight per foot, our landscape would look a lot different. Because for the same safety factor you would have to use more material, meaning more weight. Then the crank counterweights would be way off optimum, and the engine gets the shakes.

Just the musings of an old mechanical engineer. Google engine balancing, don't take my word for it.

Not an engineer here but your omitting a very key point,...... this is a horizantal opposed boxer engine, heavier/lighter,.....doesnt matter!,...it is equally opposed and balanced out by the other set (hopefully the opposing set is weight matched),...this is not a V engine requiring extensive consideration in counterbalance weights,.i.e.dont think its anywhere near as critical unless your plan is to up red line a bunch....as far as I beam, H beam....X beam and the landscape,....when buildings and bridgments reciprocate at 7,000 rpm and subject to heating and cooling that engines have you might have a point,....but for now I will except the engineers that have tested in real world experiances the designs and patents they stand by.

[3MI Racing]

Originally Posted by cf6mech

but for now I will except the engineers that have tested in real world experiences the designs and patents they stand by.

Ok, I'll wave

Yeah, I don't use X-beams. I actually use to order Pauter's years ago for my first prototype builds. I quickly went away from them and onto I-beams for the load and cycle. Pauter did great quality work and you'll never hear me say anything bad about that. Those rods are just very heavy for the equivalent weight. In fact, the only rod failure that any of my customers had was on a Pauter. The rod necked at the base, just above the big end. He was actually on only a 402 gram 4" piston which is lighter than many of my other customers with the same dimensional setup and revs.

One thing that most don't understand is that a lot of the rod companies give a cookie cutter solution on custom rods and don't actually do any FEA or serious refinement. After going through Crower, Oliver, Pauter and few others, I have a shop that will work with me on design, since I do FEA my own work.

As for FBM I'm curious what methods you used to determine '1000 hp' capable rod. From one engineer to another. I use a derivation from BMEP.

[OrbitalEllipses]

Originally Posted by 3MI Racing

Ok, I'll wave

Yeah, I don't use X-beams. I actually use to order Pauter's years ago for my first prototype builds. I quickly went away from them and onto I-beams for the load and cycle. Pauter did great quality work and you'll never hear me say anything bad about that. Those rods are just very heavy for the equivalent weight. In fact, the only rod failure that any of my customers had was on a Pauter. The rod necked at the base, just above the big end. He was actually on only a 402 gram 4" piston which is lighter than many of my other customers with the same dimensional setup and revs.

One thing that most don't understand is that a lot of the rod companies give a cookie cutter solution on custom rods and don't actually do any FEA or serious refinement. After going through Crower, Oliver, Pauter and few others, I have a shop that will work with me on design, since I do FEA my own work.

As for FBM I'm curious what methods you used to determine '1000 hp' capable rod. From one engineer to another. I use a derivation from BMEP.

Not sure many others are as thorough as you are Micah.

[3MI Racing]

No, I'm just a nerd
I'm really curious as to another engineer's method of deriving a compressive force for the rod.

[ssteer]

@ cf6 mech:

Apparently, I'm no good at quoting replies. Sorry, done on a Mark 1 Android phone while I'm away for Xmas.

Anyway, I'm fully aware what a boxer engine is. However, you do have to realize that a true boxer engine would have cylinders exactly opposite each other, with connecting rods on the same crank throw for the piston/rod assemblies to balance each other out. (Like a World War 2 V12 aircraft engine, where economics came second, performance first)

That isn't economical for mass production, and would require fork and blade connecting rods. Consequently, the cylinders are offset from each other, and each connecting rod has its own throw on the crank. To balance the mass of the piston/rod assembly on each throw, the Subaru crank has counterweights on each crank throw. Normal engine practice, and to Subaru's credit, they use two counterweights on each throw, unlike the newest VW GTI engine, which has only one per throw -- the reason why the souped-up R engine is the old one with a proper crank.

My point has nothing to do with Subaru engineering. I like their general outlook, and am on my third. My concern is with this what I would term half-thought out mods, like the connecting rod which is the subject of this thread, or pistons on several other threads. They look beefier and heavier than stock. So I ask the question -- has any thought been given to rebalancing the counterweights to account for the extra weight? If not it's an amateur effort in my opinion, notwithstanding the possible fact that the rod may be better than stock.

Here's a link to crank balancing done right.

http://www.eaglerod.com/index.php?op...d=27&Itemid=25

As for X cross-section rods, compressive strength is one thing, but there are severe bending stresses a rod has to withstand once full cylinder pressure is developed at 15 degrees or so after TDC. The X section is not an ideal engineering shape for that if minimal mass is a primary requirement. If it were, well, they would be in every engine.

Speaking of mods, I haven't put a lightweight Perrin-type lightweight pulley on my EJ257 turbo either. Since cost saving is at the forefront of engineering endeavor, all other things being equal, I figure Subaru knows what it's doing with that hunky iron one stuck on the front of all their engines. I'm conservative in my outlook.

In any case, everyone can do what they want. I just hope that my remarks help people to think things through a bit.

What does frost me is my local Scion dealer's incompetence. After waiting 8 months to drive an FR-S or BRZ, I got to drive an FR-S back on May 30. Hated the engine, sounded like marbles rattling in a tin can. Put me right off. Fast forward almost six months, and my Subie dealer finally had an unsold BRZ for me to try. Loved it! Especially as they know me and let me go out by myself.

Can you say premium versus regular gas, and crazy pinging? Scion dealer, thumbs down. Unfortunately, purchased a brand new set of both summer and winter tires for the Legacy GT in the six month wait. So, gonna use them up a bit before taking the plunge.

[cf6mech]

Ok SSTEER,......sorry if I came across the wrong way and appreciate you taking the upper road in your response, where as I made assumptions with you and didn't ....yes dealers of all sorts do some pretty stupid things and I got a few stories myself,...I'm hoping your wrong as far as the aftermarket,...I'm dumping some serious cash on a FRS testing your theories, but its with a tuner/engine builder who has years of builds behind him pushing Subarus engines to their limits,and I trust his recomendations on what works and what doesn't from what I can assume extensive trial and error experiance.... BRZ versus FRS ?,...BRZ was my first choice but every local dealer sold out,....didn't want to wait and got a FRS,....Never thought I would ever own a Scion, Subaru yes,..have owned 3 as well,....Scion no way...

As a side note he also doesn't like light weight pulleys specially messing with crank pulley's heavy harmonic dampener.