New Piston Material

[GPI Racing]

Here is some info for those that are interested.

There are some pistons out there being made from a new aluminum-silicon casting alloy, MSFC-398, which is derived from NASA materials research. Its properties at room temperature are undistinguished, but when at piston operating temperatures this material is 2-3 times stronger than traditional piston alloys. This material contains "small polygonal primary silicon particles evenly distributed in an aluminum matrix". The numerous very hard silicon particles act as pins to prevent the softer aluminum from yielding, which normally takes place as layers of metal atoms slipping past each other. It was originally developed to make it possible to move automotive piston rings higher on the piston, without the risk that the thin land of aluminum above the ring would lose strength at high temperature and break. During combustion, pressure pushes unburned mixture into the piston ring crevice volume, where it remains unburned until the low pressure of the exhaust process allows it to emerge - in the form of unburned hydrocarbon emissions (HC). The higher the piston ring is located on the piston, the smaller the crevice volume and the lower the HC emissions. In two stroke racing engines, high ring position has been adopted to prevent up to 2% of the total fuel-air charge volume from "hiding out" in the crevice volume until it's too late for it to contribute to peak pressure. In this case, smaller crevice volume equals higher performance. Two stroke pistons can greatly benefit from a piston with extra high temperature strength.

And guess who is currently starting to use this piston material???

None other than Bombardier/OMC. With the increased stress on the new E-tec motors this alloy has afforded reliability not possible before.

The results from tests of several manufacturers I've seen has prompted me to arrange having 120 pistons made for the 2.5 projects I have. Combined with the DLC (diamond like carbon) piston coating we're currently testing, I expect some interesting results. It's said that somewhere in the area of half of an engines frictional loss of 15% is piston and ring drag. I'm hoping this alloy (which has unbelievable expantion/contraction rates) with the DLC coating will give us some "free" horsepower.

Thought you guys might like the read....

Randy

[sosmerc]

Interesting. I wonder how Bombardier is "pinning" their rings??

[nelsoncat]

Any guess what the cost is going to be with this new alloy??????

[Trikki1010]

Nice post Randy,

Do you have an idea of availability and cost also

Appreciate it, thanks

Trikki

[ChrisXS2003]

I did some research and found a specification sheet. It's a pdf and too large to attach...

Interesting that MSFC-398 is "similar" to alloy "Mahle 126"...

All properties are listed as **cast**. The improved thermal expansion coefficients could allow smaller piston to cylinder wall clearances and reduce cold start piston slap. These pistons look like they'll have "forged" piston strength with cast piston thermal properties.

The silicon content isn't as high as some other piston alloys (16 w/%). The +20 weight per cent alloys are very difficult to cast...driving up costs.

Looks cool!! Might just be the shiznik!

Chris

[GPI Racing]

sosmerc,

In answer to your question, the pins are in the traditional side location. If the piston is made from the proper material and the expansion/contraction issue is correct, locating pins don't have problems. The two stroke industry has run side pin pistons for the last 50 years, only Wiseco and companies that use such low silicon ratios (wiseco has 7% or less silicon content) have problems. Its safe to say that if the piston grows and shrinks excessively, the pin hole will "grow and the pin will "grow" at a different rate. It is unfortunate that Mercury chose to run a Wiseco piston and not test the durability issue. Personally, I have NEVER had a pin failure on a piston made from the proper material. I am talking about a hundred or so engines by now. (I don't use used pistons in my rebuilds and certainly not wisecos from mercury). Example: in the snowmobile world up here, polaris, arctic cat, ski doo, and yamaha all run side pin pistons. They are all either Japanese or European pistons with 17-20% silicon.
When the after market guys started doing the "big bore" kits they used wisecos and low and behold the pins came out on some of the pistons. I think its kind of funny that the same senario has occured in two parallel industries. We could go on and on but my point is there are different solutions to the problem of pins.

Randy

[sosmerc]

I appreciate that info, and your thoughts. I have been working on outboards for many years and have only seen a few failures that clearly were caused by failed locating pins. (the failures were ALL in rebuilt powerheads and the pistons were ALL Wiseco). I quit using Wiseco after that in V-6 Mercs. (even though I'm told they addressed the problem with a later design).
Top-pinned pistons do seem to be the "rage" with the hi-performance high rpm crowd. And I guess if it eleminates the problem, then, why not?!! I'm for anything that reduces failures and the cost of our sport.
But proper control of temperature and clearances should yield a better running, more powerful engine to start with...and obviously Bombardier is focusing on this approach. I wish them success as a little competition in the industry is a good thing for all.

[msm]

Thanks for sharing those technical insights, Randy.

[GPI Racing]

Glad most of you liked the tread.

Even though I basicly bleed Mercury, I'm kind of excited about the ramblings I've heard from Bombardier/OMC. They are seriously looking at the hi-perf market and with Mercury totally giving up on the HP two stroke, they may be the next horizon for us. Their E-Tec motors really run so all is not lost yet. I just can't see myself running around with a 4 stroke. The guys at Mercury are working on a High Perf 4 stroke (4 cylinder, blown high revving verado, but you didn't hear that from me!) but in my conversations with them I told them, who is going to by a 28,000 dollar outboard for their 20ft boat. I think they would price themselves right out of the game. Hell, my current STV/2.5 cost more than I paid for my first home. I think if we (us, the boaters) give the factories some feedback we may get omc to play ball and hopefully Mercury to not build a motor that we can't afford.

Randy

[38 chevman]

Great thread Randy its always good to have a second opinion.Top pinning pistons is a way to fix a flaw with particular pistons.Although getting the right pistons ,with the right marerials the first time is the more logical choice I think,Interesting thread Randy.

[Firestarter]

Randy, great thread.
I was under the impression that the 4 cylinder motor got the heave hoe..... or as at least on the back burner.

RT

BTW, I too have never lost a pin. I have always been of the opinion that if the pin is loose toss it out, as the piston has out lived it's service life. That being said the service life is way to short on them.

[RSM]

RANDY, You seem to be up on your metelurgy (SPELLING?) Have you ever researched the benefits of a CRYO treated piston? There have been alot of posts about this but no hard core technical comparisons on what effect it has on the pistons during operating temps, expansion rates, etc. All we keep hearing is it makes them a little harder or more dense by changing the moleculer make-up? ANY THOUGHT'S!

Just found an old post from REV-RONNIE that explained alot about expansion rates vs. untreated. I had mine treated by 300 below and with the SWAIN COATING my clearences are right on with RONNIES findings. THANK'S

[Balzy]

J, time for you to toot your Kitchen Cryo techno.

[2fast4mom]

Very interesting thread and good detailed information, thanks!

It is interesting that the same model and year promax motors from Mercury are so variable with the pins coming loose. One friend of mine has over 700 hours on a promax and drives it to death, with never a problem. Two other friends had the same model and year promax and both were eaten up with side pins coming loose early on in their running hours. Seems like a roll of the dice, yet there must be a physical cause for this effect (pins coming loose) to occur.

[GPI Racing]

physical cause: crappy material. They use the vendor that comes in at the cheapest price. (kind of sounds like the government ) Remember the ART (Arias Racing Tecnologies, Japan) pistons that were in the 2.4s of yester-year. They never had problems and Chris Bush said they were worth 2 horse per hole compared to the "replacement" merc went to. Better expansion/contraction so they fit the bore better when at operating temp. What was the secret? Proper silicon content for one. With the current piston merc chose to use in the 2.5s, the piston expands and the pin is now loose, the pin bore is bigger than the pin. It cools down and it's now tight, do this repeatedly and you get the picture. What ticks me off is merc probably pays less than $40 for the piston they sell us for $250, and its crap. You can get a real nice piece done for a very good price if you go through the process. I ran some one off stuff all last summer, never had a piston problem. In the next few days I'll post some pictures and graphs (if I can figure out how to transfer images to this) on the DLC coating I mentioned. To wet your appetite, how's a coefficient of friction 1/4 the number of the current coating on the 2.5 pistons we all run. I have some before and after runs from some GP motorcycles and some F1 car engines that will shock you. For those of you who follow it, how do you think they can get a 950hp 3 litre F1 car engine to last for the whole GP weekend. Up 'till 2002 they changed engines every 90 minutes of run time. DLC (diamond like carbon) is one reason they now do 800km. The rule change to one engine per weekend meant 1) less power and be slow, or 2) find a way to make the engine last through better parts and less friction.

I didn't know if you guys would be interested in this stuff but I'll share the info if the feedback is like it's been so far. I looked into this DLC and piston stuff about a year ago. I ran some things myself (very secretly) last year. I would not subject a customer to "experiments". I used to try that once in a while and ...let's just say it wasn't a real good idea. I'm at a point where I can afford to try different things. The DLC company (Balinit DLC) had not heard of anybody doing it in an outboard, I was the first to ask. But since the GP bike guys were having such good result they agreed to work with me. We are going to run them in a few select motors this year and if the results are as good as they have been, most likely offer the service.

God these things get long when I start writing .

More Later

Randy