Has anyone wondered if replacing the plastic piston ring with a metal one would cause the cylinder bore to wear, which would drive an entire compressor replacement down the road?

 

Hi Khello,

No, I can't say I have wondered about that, but it's worth thinking through.

The cylinder head is made of aluminum, coated with some sort of sealing compound, probably applied over anodizing. The piston ring is made of PTFE, a relatively soft family of fluoropolymers that includes Teflon. The piston ring is intended to be the sacrificial part in the design, forming a more and more perfect seal as it wears, until it has worn so much that it can no longer press against the cylinder bore with sufficient force, at which point compressor efficiency begins to decline as the ring continues to wear.

A piston ring of a harder substance might not form as tight a seal against the cylinder bore initially, due to inevitable surface imperfections and unavoidable tolerances that lead to a piston ring being not perfectly round when sprung to the cylinder bore. Furthermore, a ring of a harder material might not wear quickly enough to form a more perfect seal before it had already worn the coating off the cylinder bore and begun to gall the underlying aluminum. At that point, compressor efficiency would certainly already be compromized, and continue to decline at an even fast rate than with a PTFE piston ring. Furthermore, it would result in the need for a new cylinder head, which would be far more expensive than a new piston ring.

The original piston rings seem to be lasting eight years or more for most owners, which is a very long time for a "wear" part. So given that a replacement PTFE ring is affordable and readily available from bagpipingandy.com, and can be replaced in a couple of hours, I personally don't feel that the original design is flawed. The least-expensive component wears out faster than the other components, making the compressor easily rebuildable at minimal cost. Good old German engineering!

Cheers,

Don

 

Don,


My thoughts exactly. The ring doesn't wear because of cutting corners. It's designed to wear/be sacrificial. I haven't thought about the seal tightness, but I agree with your logic. My compressor lasted 94,000 miles/10 years. I'm perfectly happy with the wear rate.


Thanks for the link. I checked the kit I ordered (still in the mail), and the website said the ring was PTFE. At $27 and two hours to rebuild every 10 years, I cannot complain about the compressor design at all.


Thanks for the excellent write up,


Mo

 

I put a bagpipeandy ring on mine...works like a charm. Happy with no issues with the compressor.

 

What's that made of?

 

Bagpipingandy's piston ring is made of PTFE just like the original Wabco rings.

 

Metal on metal would not be a durable option.

 

Same here. Compressor works like new and ring looks much more durable than original.

 

$27? My kit was $47. Still a bargain over a new compressor, but did I miss something?


I take slight exception to the statement about a "planned" wear part "making the compressor easily rebuildable at minimal cost."


If I understand correctly, without Andy there would be no rebuild parts available and Jaguar would continue to sell complete new units for $$$$; I suspect that low rebuilding cost was not part of Jaguar's nor the unit's manufacturer's design plan, but just a happy result of Andy's investment and expertise.

 

Wouldn't that be a bit of a fire hazard, given there's no oil in the system?

 

True, Jaguar would be, and still does. But others have caught onto the rebuild option and have been selling the rebuilt compressors for around half price.

Andy (God bless him) has made the rebuild possible by us common, non-machine-shops owning plebes.

 

Yeah, $27. That's what a searching E-bay turned up. I went back and checked after I had started this thread, the ring is PTFE.

 

Hi guys, thanks for the support, just be careful with those cheaper copies, they are exactly that. See some info at foot of page from an Audi facebook page I am on from other owners.

The copies are the wrong material (nylon) and in most cases are not precisely made, also I have good knowledge of these compressors and I can support any questions or issues,

the compressor kits available are not the same kits, everyone manufactures them differently its not an off the shelf standard part.

I also have new cylinders available which is a new product I have been working on see at foot of page:

any suspension compressor questions please just ask,

best regards

Andy

 

Amazing what you can find on eBay these days. I see one for as low as $21, but I always take these claims with a bit of salt and this one claims the original ring was "made from a soft plastic that wears quickly". It does say theirs is PFTE and made in the UK, though. Let us know how it turns out for you. For now I'll use the kit from Andy and hope for another 10 years of service.

I still wonder who came up with the enigmatic reservoir plausibility error description.

 

Do not confuse Andy's kit with others on E-Bay. Andy's is very well noted i the ad, and the seller is noted as Bagpipingandy.
Andy please correct me if I'm wrong. Just want to support you and your product, and not get some knock off. You get what you pay for.
Thanks again Andy for your contribution to the comunity.

 

hi mark, yes only my kit is only available from user name bagpipingandy, you can of course decide to buy GOOD PARTS or you can buy CHEAP PARTS, but you can't buy GOOD CHEAP PARTS

 

Well said my friend !!!

 

As an engineer, I perfectly understand that. Wish I had started this thread earlier.


I haven't seen anything on replacing the air filter. The hoses air so tight around the filter case, I don't see a way of getting it off without destroying them. I might cut the case, replace the element, and epoxy the case back together or try to back blow the dust out of the filter with an air hose. What have you guys done?