rbahr

Hi All,

Thanks for the information. Everything will be checked and reused if the inspection does not turn up flaws. The rods will be reused with new bolts. I will likely use the motorsport bearings. The piston & cylinders are a question for me, I realize that the 3.8l gets a lot of benefit from better flowing heads, cams, and perhaps software, but a bump from the 3.6l to the 3.8l might be nice. Been looking at the parts books and it looks like the 3.8l piston and cylinders will simply drop in with no change to the crank, rods, and cylinder housing - is that true?. That said this doc 2012 Cup car shows a 996 crank with 997 parts everywhere else.

32krazy!

my 996turbo is also a mezger engine. besides being forced induction no issues with steel rods. and 12mm studs DONT lift. search for the life span of titanium rods. the car is maybe 16 yrs old? original rods that have run for how many hrs? titanium has a much shorter lifespan than conventional rods

Rickard 993 Turbo

haulinkraut

The whole idea of the titanium on the NA engine is lightening for higher rev. As for steel rods, great idea if the car is getting boosted like the 996TT. But you loose the rev speed on a NA race engine. The 996cup also sees way less torque shock than a turbo. As far the titanium rod lifespan, they are suggested to be replaced based on the worse of the worse conditions within a very safe margin. But people have been racing these engines without issues beyond that quite often. And beyond the 40hr rebuild interval advise.

32krazy!

so how many hrs do you think is safe on a 15 yr old rod that has seen 8000 rpm how many million times in that timespan? based on 5000 miles a yr thats maybe 80,000 miles? whats the weight of the titanium rod? the srm rod weighs 451 grams. i understand theres no were near the power levels of a turbo car vs gt3 but this car was designed to be maintained like a race car hence the timeline specs. on many turbo cars pushing 1000 plus hp they are revving past 8000 rpm as well now and run steel rod

i understand the history of the titanium rods and the sound they help to make but their are viable options that also work and dont cost 3000$

Glen

Pauter, the manufacturer of the stock titanium rod in the gt3 and cup states 300hrs on these...

32krazy!

so at just 20 hrs a yr ( 20 hrs divided by 52 weeks by 16 yrs would be approx 38 minutes a week) the rods are overdue with 16 yrs use on them if the car is an 02. (im not sure the exact yr of the o/p car)

Performance Developments

Thought I could add some reason here, on how we decide when and what to change in an engine.

In Pro racing where there are huge expenses involved, corporate images at stake etc, you life and change parts based on engineered results, after hours of testing. Its all about risk management. The cost of changing parts is minor when the overall costs of putting that car on the track are figured in.

In this case, the owner is rebuilding his engine himself and from what I can see, he is doing it as cheaply as possible. It appears from his posts that the rods will be reused. In amateur racing and street hot rods, cost is a huge factor and risk management is never considered. We still rebuild many vintage Porsche engines with Titanium Rods that have untold hours of use. These engines still produce over 675 ft/lbs of torque and 750BHP at just over 2.1B manifold pressure. These rods have been serviced and rebuilt multiple times and still show no signs of failing. If these were used in Pro racing, they would have been changed out years ago.

But to do that for club racing and hot rod street engines is a cost exercise only. The idea that Titanium rods fail is more myth and reality. In my years building race engines I have seen more steel rods fail than Titanium, but more rods are made from steel. In all cases the rod never failed but failed due to other issues. If the rod is designed properly for the application, there should be no issue. I have been building race engines since the 70’s and I have never seen a Titanium Rod fail from fatigue. We rebuild many GT3 and Cup engines and I have only ever seen Pankl rods installed. I have never seen a Pauter Rod in any Porsche engine from the factory. Even the latest 991 based GT3 and cup engines use Pankl. I cannot imagine any manufacturer using a Pauter rod in one of its race engines. They are not our choice of Rod either, but for many they are.

The aftermarket goes to suppliers like Carrillo and Pauter for an off the shelf replacement typically based on that supplier’s forgings. Most all look the same regardless of what engine they are for. Comparing rod weights is like apples and oranges. The length of the rod, beam widths etc all make a difference to weight. Rods in race engines are typically designed for that engine and that application. Turbo engines can have either Titanium or Steel rods. The engine budget and its use, its expected race life, etc., all factor into what material is used for the rods. In some past engines before they were ruled out, rods were made from a composite material. Super strong and extremely lightweight.

Fear of the unknown typically is the main reason why so many change out their rods for steel versions. To put a steel Rod into a GT3 engine , street or Cup is going backwards and should be done with care, as the rotating assembly is designed and balanced with counterweight, all based on the mass weights involved.

Glen

my bad, Pankl is the stock rod...brain fade...thanks for the correction

rbahr

Hi All,

I really do appreciate all the information. For the record - I am NOT going the 'cheapest' route possible. I will replace anything the has measurable wear that is critical. I am trying to be somewhat intelligent about it as well. True I don't have the budget that some do, and certainly NOT like a professional team would, which is why I am willing to trade sweat equity for better parts c- (I also like to learn). My background as an engineer has taught me how to learn, evaluate, apply tradeoffs, and make a 'good enough' decision, and I do this on a daily basis for the last bazillion years...

I understand why parts time out and why race teams approach the problems like they do. I will never put the kinds of stress on my car / motor that these folks will.

Having said all this - I am in the situation where I am rebuilding a transmission and a motor due to an early failure of a OEM part whose faults turns out to have been known - had I know this I would have proactively replaced it.

Now if these rods, or any other part, measure out in way any as sub-par, I will replace them with an OEM part. Others make usable parts, but I will trust Porsche engineering that they made a good cost effective decision.

I have resolved the 3.8 L parts upgrade and discovered that the piston pin is 1mm bigger for the 997 than the 996, so rods, pins, pistons and cylinders would all need to get replaced. I feel that a low mileage part that has been timed out from a race motor is a fine choice - give what I will be doing.

Thanks

Ray

claykos

You can get Mahle motorsports 3.8 pistons/cylinders that are made to work with the 996 rods. The later 997 3.8s use a different setup for the rods, but most 996 3.8s are built withe the Mahle kit. I think it is around $4500 for the pistons and cylinders.

rbahr

Thanks Claykos,

I have a set of used OEM 3.8l rods, pistons, wrist pins, and cylinders coming. These will be relatively low hours and will be checked by someone who I view as an expert in this, and a machine shop. The OEM crank and cylinder housing will work fine - just need to verify that the existing cams will work. - wish I could improve on the breathing to take more advantage of that bump in displacement, but improving on heads and cams will be a lot easier in the future once this is done.

One question is: do I replace the rings with new ones, assuming the original motor had good leakdown or replace with new. I worry about problems seating the new rings and old cylinders.

Ray

32krazy!

Pistons rings and liners are built as a matched set due to the thickness of the nickasil. Rings aren't changed individually