Carl Fausett

Every time we repair a Cayenne with cylinder galling, we make up a new set of forged pistons for it.

New equipment plus new operators have improved our pistons steadily. This last set of Cayenne S with direct injection pistons turned out so good we took these pictures before they were sent out for their coatings.

Here is the webpage about our Cayenne kit:
https://928motorsports.com/services/...ock_repair.php

J'sWorld

Ross? Much different than a 955 4.5. The 4.5 and 4.8 really are very different engines.

TexasRider

Intersting.

And I'm glad you are doing them - but I hope I never see one from Mrs TRs Cayenne.

TomF

Ooooh! Engine assembly ****... LOL Very nice indeed, Carl.

Cheers,
TomF

bekks

Thanks for post Carl. Are you able to shed some light on lifetimes of ticking engines? Or further explain the ticking? I have read a lot of posts on here, but generally they all look like this:
My engine is ticking. Porsche said I need a new engine cause it is gouged. I paid about as much as my Cayenne is worth for a new engine and now the ticking is gone.
I have seen the additional detail for Turbos in particular that they consume a lot of oil. I have an "S" that has a moderate tick and doesn't consume any appreciable amount of oil.

Carl Fausett

Here is a real good thread on the topic:

https://rennlist.com/forums/porsche-...placement.html

J'sWorld

I remember when I called you and you gave me a nice little speech about Cutting Edge vs. Bleeding edge, a primer if you will. Since you didn't care to answer the question I guess we'll just have to assume their Ross Pistons which is what you stated before in another post. To be honest, they look like Pistons. CP Pistons look much nicer. Maybe you could add some more coordinates in your CAD model or possibly slow down the feed rate. Nice sales skills, way to seize the moment and carry the conversation.

nodoors

Those are pretty, and I asseverate the previously posted sentiment that I hope I don't have to see a set in person for some time! Have you guys done any experiments with shorter stroke and bore combinations for reduced rod angles and thus sidewall loading? Combined with some big turbos that could produce some major hp if the valvetrain could handle the extra revs it would be capable of spinning.

Any further findings regarding the causes of the cylinder wall scoring? This is actually the first that I have heard that the piston skirts were involved and it was not a ring issue.

J'sWorld

The 4.5 is actually quite oversquare already is which is kinda weird considering it is setup not to rev that high. The 4.8 has the same stroke with a larger bore and a longer rod than the 4.5 which makes it even more oversquare. Go figure.

nodoors

Yikes, makes you wonder how much bigger a problem the scoring would be otherwise, especially without the oil squirters. I guess the seemingly more common Cayenne S scoring is a data point despite their lower power levels since they lack them. It will be interesting to see over time as the 4.8L's get more miles if they have similar scoring rates to the 4.5 or if the decreased wall load helps their longevity.

Did you get the heads flow tested when you had them off for your rebuild? I think I remember you stuck with the stock cam. Did you go with stock or stiffer valve springs?

It sure would be fun to spin one of these an extra 1,000rpm and get some big boost in there, even with the long intake runners and conservative lift/duration cam. It would probably make me too nervous to try if/when I do get around to a rebuild myself and I am sure the programming for the transmission would be a major pain in the you know what to get it right.

Carl Fausett

We do not use Ross pistons. I prefer Arias pistons. That's who makes our pistons for us.

I thought I explained that before, but apparently not.

Please understand these pics are taken mid-manufacturing, and before they went out for crown and skirt coatings. Don't compare these pics of a piston-in-process to someone else's finished pistons, please.

nodoors

Carl, can you speak to any further recent findings with these failures?
What specifically about your kit addresses or resolves the problem?

CAVU

Thank you for sharing the images. I am hopeful that you will share images post coating and help expand my awareness. Neat stuff.

Carl Fausett

Yes, I will. Ran out of time today, but I'd like to provide what I believe to be the best explanation yet.

J'sWorld

All that aside, FWIW, I have said it before and I'l say it again. For a build situation that doesn't require the maximum strength attainable I think that your service and procedure is the most cost effective and realistic approach to the Cayenne engine while being much more than adequete.