LA964RS

...looking into the future....How many ponies can the stock rods take?

450hp
500ph
525ph
550hp

Thanks,

hatchy

A lot of people say the stock rods are good for about 500 ft lbs of torque.

Steve Weiner-Rennsport Systems

Its a question of HP output over time.

I would not use the stock rods in an engine making 550 HP or more and I would not use them in an engine making 525 HP for long periods of time (competition usage).

They are safe for 500 HP, even for extended periods (Street & DE usage).

We recently did a 600+ HP TT that received a different crank, better rods, better oil pump & a host of oiling modifications so it can successfully survive 7000+ RPM without a problem.

LA964RS

Steve...what's the most economical replacement rod?...For a sub 600 hp engine doing street and a few track days a year.

Thanks

Sameer

Pauter, Carillo or (Ruf titanium rods which come with a 100,000km waranty).

Kevin

Pauter rods are cheaper than the Carillo's.. I would spend the extra monies and have always installed Carillo rods. Make sure that you get the 3/8 Carbolt option.

Steve Weiner-Rennsport Systems

Everyone has an opinion of course, and we've used a LOT of both Carrillo & Pauter rods over the past 25+ years,...

Both products are very good and can withstand some driver-induced RPM excursions well beyond 10K RPM (provided other mods are done). We use Pauter's now for their sheer durability, some windage advantages, price & availability.

LA964RS

How much do a set of the Carillo's go for?

By the way, are the Ti rods even an option?

Thanks

Sameer

Kevin,
What is a 3/8 Carbolt option?

Sameer

Kevin,
I belief you posted this sometime back in the 996tt forum.

Hear is a picture of a handful of connecting rods... From right to left we have:

1) Factory 930, 964, & 965 conn rod, very durable and provides long life when one balances and installs ARP rod bolts...

2) One of my favorites.. A Carrillo 930 conn rod, very strong, another benifit is that it has holes at the 4 & 8 o'clock position to provide oiling from the oil squirters that are in the case...

3) My new Titanium Pankl conn rod for my engine project... Extremely lightweight, strong and track proven for Porsche

4) 993TT & 996TT conn rod... This rod is the weakling of the bunch, it has some limitations. If you look at the neck of the rod, it is very narrow. Also, the rod bearing are much narrower. The GT3R uses 930 bearings!

5) and for fun, you boys can guess the application...

K24madness

It really comes down to two things. How much torque you want to generate and how many RPM's you want to spin the motor.

Compressive loads are applied from torque output on the connecting rods. These are the forces that will "bend" rods. Anytime you increase "peak" torque you are loading the rods approx 20% more of that increase (as measured at the crank). This is due to the fact that of said increase most of the addtional pressure will occur after "peak" cylinder pressure (closer to 90% crank angle). The abilty of a con rod to recover from repeated "compressive loads" is not at problem.

Tensile loads on the con rod are a result of the piston reaching TDC and the crank trying to pull the piston down. As RPM's increase the inertial load on the con rods, bearing caps and bolts increases dramaticly. It is the highest when the piston is on the exhaust stroke (no opposing forces from compression). From 6,000 RPMs to 7,500 RPMs the increase is approx 144%. Another problem is that a con rod does not recover well from tensile loads. The damage from over reving will cause a rod to fail over time.

How much "torque" or "RPMs" will damage a rod is the subject of great debate. There are many cars (mostly 996's) running setups that you can use as a guideline. I have found two cars that have "bent" rods from making lots of torque. There are also a few (996's) that have destroyed con rods on a stock setup from overreving on a downshift.

Just cause one car's rods last does not mean yours will. It you want to play it safe go for the Carrillos. They are among the best.

My POV is keep the revs in check (under 6,200) and limit peak torque to under 600 (at the wheels). Most cases have shown 650+ WTQ to bend rods.

FWIW the 996tt & 993tt have the same PN for rods.

Kevin

Sameer;

Carrillo will actually install a high grade, high tensile strength rated 3/8" bolt in the rod. It is there own design and highly recommended.

Geoffrey

The nice thing about Carrillo is that they give you a stretch number to torque to 3/8 Carr bolts to.

MichaelM

Well I know the Carrillo's are the 4th from the left, because that's what I have , and I beleive the far right is the 930 rod, and the second from the left is the stock 993tt, but of course i'm not an expert.