2.0 vs 2.2 rods

[blue72s]

As you may know, BA prefers the 2.0 rod over the 2.2
However I can't see why because the latter look very much like the 2.4 rod and beyond. What's wrong with 2.2 rods?

[BURN-BROS]

Do a search, mucho info is out there.

[jluetjen]

blue72s; I believe that some people have a preference for the 2.0 rods because they are strong enough, and significantly lighter then the 2.2's. I believe that a comparison of the weights was posted here previously. Did you find what you wanted by doing a search of this BBS? I did a quick search and found a couple of pages of threads just in the "911 Engine Rebuilding Forum" alone.

[blue72s]

I did a search and found some info but nothing about rod weight comparisons.. Could you pls post a link?

[jluetjen]

Here's a comparitive picture of (L to R) a 2.0 rod, a 2.2 and a 2.7 rod.



I weighed the 2.0 and the 2.2 rods (both with bolts but no nuts since I was missing nuts for that particular 2.0 rod and I wasn't in the mood to rummage around in the cold garage for another one )

2.0 Rod: 608 grams
2.2 Rod: 702 grams

The biggest difference between a 2.0 and a 2.2 rod (to my eye) is in the robustness of the rod cap. Note the length of area through which the bolt runs on the two rods. The 2.0 also has noticably less material across the cap.

PS: Yes, the 2.7 rod is junk (note the extensive discoloration). It had a spun bearing in it when I tore down my donor motor. The rest of them have already been sold and I kept this as a conversation piece.

[Plavan]

jluetjen,
Is that my old 2.2L rod
We got the 2.5L running. Boy that thing is nice! I was spinning the tires in second gear (Kumho's) I could never do that with my stock 2.7 so easily.

[jluetjen]

Is that my old 2.2L rod

Yup!

[blue72s]

Soo, which is better? Yes, 2.0 rod is lighter but is it at least as strong?

[svandamme]

did you weigh with or without rod bolts?

i weighed my 2.4's , 2 weeks ago , and they were all around 600 gram

[jluetjen]

did you weigh with or without rod bolts?

I weighed it with the bolts, but without the nuts since that was the way that they were at the moment. I didn't have time to do more then that.

Soo, which is better? Yes, 2.0 rod is lighter but is it at least as strong?

"Better" depends. I doubt that the 2.0 rod is "at least as strong" as the 2.2 or else why would Porsche have redesigned it? The critical factor question: Is the 2.0 rod strong enough? If the answer is yes for the application in mind, what's the benefit of the extra weight of the 2.2 rod?

[Plavan]

Both John and I have different ideas on this subject. Which is great because we traded rods with each other (I gave him my 2.2L rods and he gave me the 2.0L rods)
John has some valid points.
My way of thinking is this. We have never seen a 2.0L rod "break" in our racing motors. What does causes a rod to "break" is a prior malfunction inside the motor. Example- oil not getting to the bearings, or oil starvation under braking, excessive bearing wear/heat etc. If any of those things are happening, ANY rod will break regardless who made them (Pauter, Carillo, or a stock Porsche rod, etc). We have seen our share of broken Carillo rods and gave up on those. Way too much $$$$.
So we stick with the 2.0L rods for the lower weight (remember there are six of them ) This helps the motor spin faster with less weight moving around inside the motor. Again, a 2.0L rod will not just "Break" there are compounding problems that will cause ANY rod to break.
Either rod will work in your motor great, so you cant go wrong.

[Plavan]

BTW John, Nice choice of granite.... we have the same granite in our house

[blue72s]

i weighed my 2.4's , 2 weeks ago , and they were all around 600 gram

With or without bolts? and nuts?

We have never seen a 2.0L rod "break" in our racing motors.

Your engines or race team factory engines?

[Plavan]

In "our" race motors. Most guys we race with have 2.0L rods and rev the #$@% out of them. None that I am aware of have had a rod just snap by its self. If we saw 2.0L rods breaking, we would not have them, and friends would not have them in the race motors Now if you have something like 16:1 compression and 400 HP thats a different story

[jluetjen]

Actually Chad; I've hedged my bets since I have at least an engine's worth of 2.0 rods still here. I figure that I'll use the 2.2 rods for version 1.0 of my engine since that will get a bunch of practice time, driver's schools and regionals use. After 2 or 3 seasons when I redo the bottom end (engine spec 2.0) , I'll check out how the 2.2's held up and potentially switch to the 2.0 liter rods for a no-holds-barred national motor.

[neilca]

One good reason to go with the 2.0 rods is that you can buy ARP bolts for them. You cannot get anything but stock for the 2.2. That being said I am using 2.2 rods in my race motor because I believe they are good enough for me.

[jluetjen]

Henry Schmidt pointed out in this thread that the 928 bolts will work as a replacement for the 2.2 bolts. A set of Raceware bolts for the 928 is $400 and you'll have an extra 4 left over as spares.

[neilca]

I reread that post and Henry said he used 928 rod Nuts, not bolts. You might want to revisit that post.

[blue72s]

yes you're right:

The 2.2 factory bolts are up to the task. I do prefer to use 928 rod nuts with these stock bolts as an upgrade.

What about the 2.0 factory bolts? Are they also up to the task?

[Plavan]

I would suggest using ARP rod bolts for the 2.0L rods. You can reuse them and not have to worry.