Yep. The race support shops say the same thing. *NM*

My 2000 Boxster 5-speed has a sport exhaust whose mounting system has failed twice recently. Years ago, when I bought the car, I had to have the mounts to the bracket repaired. The exhaust has a couple of welded "caps" that each contain a bolt coming up through it, These bolts attach to a pair of mounts that are on a bracket. The exhaust is kinda suspended from this bracket. Recently, the bolts that attach to the mounts failed. I took it to be repaired, and after one weekend at the track, these bolts have failed again. Sheared apart.

Does anyone know what type of bolt I should be using to make this repair? Apparently, the bolts that were used in the most recent repair couldn't stand up to the stress.

.. look at the alignment of the mounts, the exhaust, and the motor. I suspect sometihg is out of alignment and placing undue strain on it.

I have never paid any attention, despite high miles (225k) and >60, 75? track days on my MY2000.

Ditto my 2004 (well > 100 track days)

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Ok, so here is an update. Back in August, the stock trans mounts failed (they were the original mounts from 2000 - no surprise there). So, I replaced them and the mechanic recommended semi-solid Wevo's for added stiffness and response on the track. Nothing else was changed. I said sure, not believing this would be an issue. Well, after the exhaust mount failed 3X since then, and every time at the same place - those bolts installed into carriers that are welded onto the top of the exhaust in the upper bracket, I talked to a better Porsche mechanic who is also a champion spec boxster racer. He recommended going back to the stock trans mounts, making the point that the Wevo's were effectively a solid mount, and that without any other changes to the overall system, there could be issues. He pointed out that the engine, trans and exhaust are an integrated system. And in all likelihood, without making other accommodations (e.g., lighter exhaust system), this is likely the problem. So, I have returned to stock trans mounts, and using a different shop, repaired the broken exhaust mounts, correctly this time. The new mechanic said that the failed bolts were welded into the carriers on top of the exhaust (incorrectly) vs. just being suspended in the retaining caps on top of the exhaust. He speculated that this was really causing issues, as it would make the entire system too stiff. So, my lesson learned here is that some of these mods cannot be done alone, and that the entire system needs to be factored in.

I have the car back, and we will see how the new mounts hold up...next track day may be September.

People often forget to share back their learnings once their problem is resolved. Thanks!

.. but will leave well enough alone.

Grant

gee-lenahan-at-gee-mail-dot-com

This isn't the first time that I was tempted by a mod. Once, I gave thought to a spin-on oil filter mount. Decided to ask what my fellow, more senior enthusiasts had to say about that. Someone pointed out that Porsche engineers design things a certain way, and very deliberately, and that it's designed the way it is designed for a reason. Long story short, I am using stock filters. When I change the oil, i tear that filter apart, spread that accordion out, and inspect it...something i could not do with a more traditional filter housing. That is worth it, totally. Its way to easy and tempting to make a small mod to a car, without realizing that in these "integrated" systems, there may be unintended consequences. So, I am very careful about that now.

… solid and semi-solid engine and transmission mounts in these cars is very tricky.
The way the car's ECU deals with pre-ignition (knocking) is by monitoring engine vibration and then adjusting timing.
Many of these solid and semi-solid mounts do not dampen the normal harmonics thus the vibration sensors believe the engine is knocking and adjusts timing therefore reducing power.
We've tested a few Boxster Spec Racecars where we install semi-solid mounts and record their best time around Sebring.
Then we change the mounts to OEM and the car looses several seconds per lap.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Quote
Pedro (Weston, FL)
… solid and semi-solid engine and transmission mounts in these cars is very tricky.
The way the car's ECU deals with pre-ignition (knocking) is by monitoring engine vibration and then adjusting timing.
Many of these solid and semi-solid mounts do not dampen the normal harmonics thus the vibration sensors believe the engine is knocking and adjusts timing therefore reducing power.
We've tested a few Boxster Spec Racecars where we install semi-solid mounts and record their best time around Sebring.
Then we change the mounts to OEM and the car looses several seconds per lap.
Happy Boxstering,
Pedro

Interesting. If the solid and semi-solid mounts cause the sensors to adjust timing to reduce power, how does it make the cars faster around Sebring? Do the stiffer mounts improve handling enough to compensate for the reduced power?

… you eliminate the knock sensors, so all the vibration doesn't make the ECU retard timing.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Quote
Pedro (Weston, FL)
… you eliminate the knock sensors, so all the vibration doesn't make the ECU retard timing.
Happy Boxstering,
Pedro

Thanks Pedro. Now it makes sense.

Grant

gee-lenahan-at-gee-mail-dot-com