Opinions on R&R connecting rods?

[stownsen914]

Curious to see what people think of these. I believe LN Engineering used to sell them, but I don't see them on their web site anymore. Are they comparable in quality and durability to Pauter or Carillo?

Thanks for your opinions.

Scott

[Steve@Rennsport]

Scott,

The best way to answer this by taking some time and see what professional race engine builders use in their engines that will see over 7K RPM. For these people, their very reputations are at stake since engine reliability is FAR more important than power.

[stownsen914]

Thank you, Steve. I hear a lot more about Pauter and Carillo than R&R. I guess that says something.

On a related point, I've heard that since Carillo was purchased, that there may have been some decrease in quality. I'd be curious to hear any opinions on that too.

Scott

[Henry Schmidt]

The R&R connecting rod is a highly developed correctly engineered bit of kit.
In other words, our experience with them has been exemplary.

We've used them in both high powered turbo and high RPM normally aspirated engines.
They were our choice for the "spare no expense", 9000 RPM na engine we built a few years back. Since then, they are our second choice for compatibility with our SuperCrank, second only to Pankl titanium GT3 rods.

[Henry Schmidt]

Originally Posted by stownsen914

On a related point, I've heard that since Carillo was purchased, that there may have been some decrease in quality. I'd be curious to hear any opinions on that too.

Scott

It is my understanding that Carillo forgings are no longer being made in the United States. (rumor)
R&R rods are engineered, forged and machined in the US. Material certs & reliable machine processes mean everything to us when selecting parts compatible to requirements.

[chris_seven]

I thought that CP Carillo was a subsidiary of Pankl Racing Systems and it is surprising that quality has deteriorated in their ownership.

Pankl generally has a reputation for excellence.

Having said that I have always been impressed by the design features of the R & R Con Rods

[stownsen914]

Thank you gentlemen for your opinions - much appreciated.

My recollection about Carillo may have just been off base. Pankl is certainly no slouch of a brand!

One thing I noticed about the R&R rods is that they are somewhat heavier than Pauter's offering for my application (66mm stroke) - about 50 grams. Though still lighter than stock by about 100 grams.

Scott

[chris_seven]

The X Beam used by Pauter is about as light as they get without using Titanium and although I have never used them have a good following in the UK.

H Beams, which are fashionable tend to be heavier by nature of their design with an I Beam being some where between.

We have 3-D modelled all of the 911 Rods and looked at weights, sections and bending stiffness's..


In simple terms the 'strength' of a rod is merely a function of its cross-sectional area.

In bending I beams do well as they have a good second moment of area relative to their cross-section so they are light relative to their stiffness.

Relatively long rods used on long stroke normally aspirated engines benefit most from this design.

H-Beams are probably easier and hence less costly to make than I Beams and this is probably why they have been strongly promoted.

The do have a benefit on heavily turbocharged engines where there is a significant twisting force acting on the piston.

I beams in this configuration can buckle as they twist whilst also bending. H Beams are much more resistant to these forces.

At 66mm stroke I am not sure you have too much to worry about as the stresses are well within any sensible designs capability even at engine speeds of 8500rpm.

We eventually manufactured the H Beam - again reasons of cost. We used a VAR Steel and have them running in 3 rally engines but we only use the 'in-house' as we are not set up to support them in the general marketplace.

[Tippy]

What is the cost of R&R con rods for a 3.2? Not buying any now, but curious.

[Henry Schmidt]

Chris I notice that you don't mention X beam in your analysis. Why?
Not being an engineer, I am left with information I glean from the experts and my understanding is that the X beam offers the least suitable design for high performance engines.
That is not to suggest that Pauter rods are low quality, much to the contrary, I believe Brain has produces an exceptional rod by using top quality materials and exceptions quality control.
Are we looking at a situation that says "not the best engineering but good enough for the application?"

BTW: my comment about Carrillo forgings being made outside the US was not to suggest that the "quality has deteriorated" (your words) but just to state that the process may have changed, rendering previous experiences moot.

[Flieger]

I would have thought that the H beam would be the most difficult to manufacture- the I beam and X beam can be mostly milled or forged from 2 sides but the H beam needs to come in from 4 sides.

I beam looks the best to me without doing an analysis- I don't see why you would need a web in the middle like the Pauters, although I guess the load path for the compression/tension is a little better than in the I beam webs.

Chris, can you expand on the twisting force on the piston? I am not seeing how this could happen, turbocharged or not.

[chris_seven]

Originally Posted by stownsen914

Thank you, Steve. I hear a lot more about Pauter and Carillo than R&R. I guess that says something.

On a related point, I've heard that since Carillo was purchased, that there may have been some decrease in quality. I'd be curious to hear any opinions on that too.

Scott

Henry,

There are several interesting points that you have made. My suggestion that Carillo's quality had deteriorated was a response to the previous statement , not the one you made, and I was just pointing out that the Pankl had a decent reputation as I have no real axe to grind with regard to any aftermarket rods.

You comments about where a forging, or indeed the steel being used is manufactured, is a very interesting argument and I agree in some respect but not completely.

I do have some experience in working with the global steel industry having been involved in the design and manufacture of tensile, fatigue and hardness testing machines for many years and having studied and been involved with Engineering Materials behaviour most of my career so I do feel qualified to comment.

The simple truth is that poor quality materials can be produced anywhere in the world and knowing how to avoid buying junk is very significant.

The ability to manufacture high quality components starts with specifying the correct materials and the correct processing and having a Quality Control System that guarantees the correct result.

If the material or forging has been manufactured to the correct specification it really doesn't matter where it comes from.

The question is does the company making the product have traceability, has testing been carried out and is the certification that backs this up robust enough for guarantees to be made.

Providing Carillo have a robust QA programme then your argument that changing forging supplier or the country of origin shouldn't apply as you should be confident that Carillo have ensured that the quality of their product is still excellent.

The entire ISO 9000 manufacturing system is designed with this objective.

I must say I have no idea about Carrillo's QC/QA system or it's integrity but I would hope it is up to scratch.

Many manufacturers claim to use 4340AQ quality steel for example, a simple claim but...

What do they mean by this? Typically 4340AQ would be ordered to a specific AMS Standard (6451 for round bar, I think).

AMS standards tend not to control mechanical properties but do control chemistry to slightly higher standards than ASTM specs. Bars also tend to have been cold rolled.

It is likely that mechanical properties following hardening and tempering may be a little more consistent than an ASTM specified material but I am not sure this is of any great consequence.

(Interestingly Pauter suggest that they use 4340 with increased Nickel content - which may not be a bad thing- but is does mean that the material shouldn't be described as 4340.)

This would tend to indicate that the fatigue life of components using steels of this type would have less scatter and we should be more confident but in reality it makes less difference every year as steels simply become cleaner due to better process control.

I have always wondered if all the companies using 'aircraft steel' buy material with specific Aircraft Release Certification as the cost premium can be very significant.

With regard to the Pauter Rod, it was a design we didn't consider.

The main reason was that we didn't want to simply copy what is a fairly well recognised product. We have worked quite hard to optimise the designs we have looked in terms of weight and basic stresses and they are so generic in concept no-one would suggest we were simply copying.

Even if the cross beam is not ideal in terms of bending or twist there are enough of them out there to say that they must be strong enough.

I would say that material quality will have little or no effect on the elastic properties of the con rod as the impact of cleanliness on shear modulus would be immeasurable but it could have some impact on fatigue life.

To be practical, however I do think we get carried away about some of these issues as if rods were so critical we would see a great many more failures and I generally feel that Normally Aspirated 911 engines don't generate sufficiently high stresses to worry too much.

[Tippy]

To your very last point Chris, the first time I saw the con rod from my 3.2, I thought there should be NO reason my engine couldn't turn 8000 RPM. I asked here about the rev limit using 7.5:1CR Max Moritz 3.4 (98mm) pistons, stock 3.2 rods, with ARP bolts, and was told by (IIRC) Henry and Steve W to keep it no more 7k, or about 6750.

Now, if you've seen American iron V8's, the rods are far longer and slimmer cross-section wise along with strokes being much longer, but many turn over 7 to 7.5k for years without issue.

Always struck me as odd. But, if Steve and Henry state the rev limit, I'm taking that to the bank!

[Flieger]

I think the issue with the 3.2 is the smaller diameter rod bolts.

[chris_seven]

Carrying out a rod bolt stress calculation is relatively easy if you know piston weight, rod weight rod length and stroke.

Calculating the force is straightforward and then it is easy to determine the stress in the bolt.

[Pat RUFBTR]

Hello to all,
My connecting rods R*R profile H installed on one crankshaft 3.6L.

The weight of each of them, see understood ARP2000, is of 508g/u.

Very beautiful received quality, for the moment I cannot tell it to you more.