Carbon Pistons

[buster73]

Just back from a trip to Germany and have something interesting to report. A small German company (www.voelkl.net) is offering pistons machined from solid carbon (or more exact a mix of carbon, carbides and ceramics) for racing applications, but also for classic cars where original pistons are difficult to source.

Weight reduction in comparison to a forged Aluminum piston is 10-15% for a conservative design and reliability comparable to a stock piston and up to 30% for racing applications. The carbon material has superior heat resistance and the mechanical properties even increase with higher temperatures. For many engines, piston cooling is not required anymore. A small coefficient of linear expansion allows to reduce the gap between pistons and cylinders to 0.001-0.002 mm which is roughly half the gap typically recommended for aluminum pistons. Dry running capabilities are very good as the graphite content acts as an internal lubricant. They even run a 2-stroke racing engine with direct fuel injection and plain gasoline and no oil content in the fuel.

Another very interesting application are brake caliper pistons where the low heat conductivity of carbon helps to reduce thermal problems.

The manufacturer can design the pistons specifically to the requirements of each customer (e.g. number and size of piston rings…). Each piston is CAE-designed and optimized. The manufacturer can include dyno runs and reliability runs. The first parts of each batch are inspected by an external testing laboratory using X-rays and holographic testing methods. With production batches from approx. 20 pistons the price is said to be competitive with forged Aluminum pistons.

Sounds very interesting and thought it is worth to share.

[Wil Ferch]

Thanks..interesting developments..... let's see where this leads...

Wil

[William Miller]

For those following the Alusil Thread:
I'll have to go look it up, but aren't the KS Alusil Pistons are coated with something to allow the aluminum to withstand the wear of the silicon impregnated cylinder walls?

Alusil's can't be cut oversized because there are I understand that there are no pistons avalible with the coating and the typical race product, Like JE will not last.

This product might be an oppertunity for those with Alusils to bore oversized and get some higher CR's?


Is

[304065]

So when you de-carbon your engine do you buy new pistons?

Or do the tops of these get coated with Aluminium over time?

Just kidding, of course. Cool thread.

[88911coupe]

On a similar note I've seen reports over the years about cylinders and pistons being made from 100% ceramic which needed little if any oil at all. They ran at very high temps which dramatically cut emissions but I guess the costs were too high or there was some other problem that is keeping them off the market.

[jluetjen]

I remember reading about Ceramic turbines for turbochargers. They worked great thermally and their low mass drastically reduced turbo lag. The big problem was to diagnose any failure modes since whenever one of the ceramic turbines would fail, it would be catostrophic. They would shatter into dust and blow out the exhaust. So the engineers never had any units that they could post-mortim!

[kach22i]

Cool idea, just giving the thread a bump so more people find out.

[Early_S_Man]

What a complete waste of time and money for brake caliper piston applications!!! Chrysler has been using simple-to-make Bakelite caliper pistons since 1973 ... cheap, lightweight, low heat transfer to the fluid, zero potentioal for corrosion, etc. You do have to be careful not to drop them on concrete floors, though!

[svandamme]

price on these carbon pistons vs oem ???

[Wrecked944]

I'm usually the last person to question the benefits of a new gofast technology . But isn't it risky to incorporate a carbon piston into a motor that wasn't specifically designed for it? Motors in general (and ours in particular) are designed as systems - not just collections of bits. For instance, it sounds great if you can do away with piston cooling. But might this not put more thermal stress on the cylinders and heads and valves since the pistons no longer act as a heat sink?

Originally posted by 88911coupe
On a similar note I've seen reports over the years about cylinders and pistons being made from 100% ceramic which needed little if any oil at all. They ran at very high temps which dramatically cut emissions but I guess the costs were too high or there was some other problem that is keeping them off the market.

I vaguely remember they had some problems with cracking. Too brittle to handle the stress of daily driving IIRC. Maybe someone can correct me if I'm wrong.

[kach22i]

Originally posted by JanusCole
I'm usually the last person to question the benefits of a new gofast technology .

Good rule of thumb is to wait 5 to 10 years that way all the lawsuits have been made, and the improvements/changes have been incorporated into the product before you spec/use it.

Although I can assure you, Porsche doesn't seem to do this.

[buster73]

New technology certainly always bears some risk. Technical ceramics (and the above type of carbon compound) are around for more than 20 years and have improved significantly over the years. They have now reached a level where they become usable (and affordable) for applications such as pistons. I think they are especially interesting for racing applications and can offer tremendous benefits. The manufaturer is in discussions with top motorsports governing bodies to open the door for this new technology. They are sure no alternative for stock applications if aluminum pistons are readily available.

[RickM]

This (or at least similar technolgies) was discussed back in Jan. Interesting stuff... Carbon fiber pistons w/ceramic rings?

[buster73]

Originally posted by Early_S_Man
What a complete waste of time and money for brake caliper piston applications!!! Chrysler has been using simple-to-make Bakelite caliper pistons since 1973 ... cheap, lightweight, low heat transfer to the fluid, zero potentioal for corrosion, etc. You do have to be careful not to drop them on concrete floors, though!

You are right, the phenolic brake pistons used by Chrysler, Dodge, Ford and some others work nicely these days (although they had some tolerance issues in the 70's and 80's ). The interesting point is that you can have machined carbon pistons for any caliper and specification. And if your caliper gets unusually hot you will have more reserves build in. However you don't wont to drop them either, or try to get them out of the caliper with a pry bar.

[ChrisBennet]

Originally posted by jluetjen
I remember reading about Ceramic turbines for turbochargers. They worked great thermally and their low mass drastically reduced turbo lag. The big problem was to diagnose any failure modes since whenever one of the ceramic turbines would fail, it would be catostrophic. They would shatter into dust and blow out the exhaust. So the engineers never had any units that they could post-mortim!

I was at a Tech Tactics a few years ago and one of the speakers with some sort of honcho of the engine development group. They experimented with ceramic turbo impellers but in order to make them durable they had to make them thicker which offset the lightness advantage. Metal turbine blade technology advanced to the point where the ceramic blades didn't make sense.
Hmm, I think a friend of mine has a patent on a process for casting ceramic turbine blades.
-Chris

[Wrecked944]

Originally posted by RickM
This (or at least similar technolgies) was discussed back in Jan. Interesting stuff... Carbon fiber pistons w/ceramic rings?

HA!! And I was the goober who started that thread and then totally forgot it. Must remember to buy more ginkgo...

[911pcars]

I thought I read somewhere Honda used carbon pistons in their F1 turbo engines, and that was awhile ago. I'm betting all F1 engines use them today.

Honda even experimented with ringless pistons to help reduce friction and increase engine speed (more speed = more HP). It didn't work. The power loss from blowby offset the power from increased revs.

Sherwood