JE pistons (good alternative ??)

[Jerry S]

I am in the process of building my 3.3 litre turbo engine and have found that my piston ring grooves are beyond spec which would explain why all 6 of my cylinders had broken compression rings. As a result my cylinder #1 was scored but I do have a spare used cylinder to replace that with. My question is what to do:
1 - use assortment of two complete used sets to try to piece together one good set (all ring gaps are borderline - eg 0.004 in)

2 - purchase a set of JE pistons for the turbo car and reuse with old cylinders which are in reasonable shape

3 - bite the bullet and purchase a new set of RUF 3.4 litre p/s set

Are the JE forged, and are they a good alternative to Mahle. This is my preferred thing to do since the cost is reasonable and should ensure no more broken rings. Are there any drawbacks to these particularly for a 930??

Thanks Jerry S

[cnavarro]

Are your 3.3 cylinders the fully finned variety? If not, go with the new RUF cylinders, bored out 3.2 cylinders, or a set of Nickies.

The JE pistons (which are indeed forged) are a very, very good option if your cylinders measure within factory spec for ovality and there isn't any irregular wear. One thing you'll be battling will be a possibility that the replacement cylinder is a different height group, which just means all the cylinders will have to be surface ground to the same head to deck length.

Secondly, there may be variations in bore sizes that may cause excessive or insufficient p/c clearance. This is best solved by having your cylinders stripped and replated and while you are at it, provide one of your new pistons so that they can verify that the proper clearance is maintained. Otherwise you may end up with a setup that is less than desirable.

Are you planning any other upgrades to your engine while you overhaul it?

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[randywebb]

You need to talk to Steve Wiener. About 2-3 months ago, he began warning people away from JE pistons (Naturally, this was after I already had put them in my motor... always happens).

I can only assume that the Gamroth organization has seen enough of these to see a level of problems that warrants rethinking their use...

[350HP930]

I have built a lot of performance motors with JE pistons in the last year and have yet to have one fail. They appear to be well made and machined and I have never measured one that has been more than 0.0003 out of spec.

I think anyone who criticises JE is barking up the wrong tree.

If I was made of money I would get a set of nickie cylinders with JE pistons.

Being on a budget I would rebore and plate a good set of used cylinders and use a set of JE pistons.

[randywebb]

"in the last year"

Gamroth is an _extremely_ well regarded shop -- and I don't mean just by retail customers or weekend racers.

Your phrase, quoted above, may be the issue -- if you had data from several years ago you might see a pattern that you don't see now.

Frankly, I don't know anything about this. And my JE's were very pretty and lighter than Mahles. But I think some caution and investigation is called for.

[Jerry S]

I was only going to put in some SC cams since I have a good set available. I was only looking for moderate improvements above the freshening of the engine.

Thanks Jerry S

[strokher racing]

JE pistons are far superior than the mahles. From the materials, to their weight reductions, to the custom selections. I have personally ran at least 10-15 different sets of JE's. I have never had an issue...except for once when UPS dropped the package If you have any worries ask Stephen Kaspar how many engines he has built with JE's. I would estimate several hundred sets. I would stay away from the RUF stuff. Besides being over priced you are limited on what you get, and I have heard issues with it. I have a kick ass set of cylinders if you decide to go the 3.4 route. Add a set of JE's and you will be set at a fraction of the price

3.4 cylinders race ready!


Eric Hood

[MotoSook]

I'll second Erics reference to Kaspar's use of JE pistons. When I spoke to Stephen, he said he "got tired of trying to convince people [online] that JE's are superior to the Mahle's." He's never had an engine with JE pistons come back. I'm building an engine now that will use 98mm JE pistons....a 3.4 Turbo!

[Steve@Rennsport]

Hi Eric:

With all due respect, I'd disagree with a few statements you offered,....

JE's do indeed offer flexibilities that cannot be achieved with the limited offerings from Mahle, but to say that they are "far superior" on the basis of that is simply incorrect. I say that based on 30+ years of building 911-based race engines for SCCA, IMSA, TransAM, PCA and some Vintage racing venues.

There is no question that JE's qualities of reasonable cost, availability, custom configurable, and light weight make them well suited for competition engines where control of ring widths, high CR's, and cost are admirable & desirable assets. Things begin to change when one demands long life and long-term durability/longevity from the piston/ring package and thats where Mahles really shine FAR ahead of JE's. I've seen FAR more failures on JE's than I've ever seen with Mahles and thats going back to 1974.

Piston-to-cylinder wall clearances, head land ring clearances are just a few of the issues that separate JE's from Mahles and my only point is that nobody ought to assume that a set of JE's will last as long as equivalent Mahles will since that will not happen. Several parameters must be changed in the JE specifications to get close. Mahles are indeed heavier due to a much denser alloy and run at clearances that not only optimize ring and piston life, it contributes to better long-term ring sealing.

We use JE's in race engines where the powerplant will be disassembled and inspected every year or two (depending on the configuration). Since JE's are quite reasonable in cost, its not a hardship to replace them at intervals commensurate with the engine's operating RPM and parameters.

Bottom line; the best choice of what pistons to use really depends on the application, longevity expectations, and what one's budget is.

I'd concur that the RUF-spec 98mm P/C's are not the most durable things due to their ultra short skirt design that permits excess rocking around TDC and high rates of piston and ring wear. The regular 98mm P/C's are far better.

We are all the result of our experiences and its up to anyone to determine what information is useful in this regard. I do encourage our clients to take the long-term view of things instead of simply voting with their wallets.

[MotoSook]

Steve,

Did you log/track the wear on the JE pistons (and the cylinders used) on the competition engines? I'm curious to know how much wear (and what mode) you saw from year to year (or inspection to inspection). Did you also track the wear for trending against JE's forging changes/improvements?

[Steve@Rennsport]

Souk:

Yessir, I do track wear (at teardown) as well as other parameters such as leakdown at regular intervals. Cylinders ranged from Biral to Mahle Nikasil. We see excessive (compared to Mahle) wear in the head ring land
area as well as around the oil ring and pin bosses due to the pistons rocking in the bores and larger-than-ideal clearances.

We started using JE's when they first began making 911 pistons 15 or so years ago and yes, their newest designs are much better than where they started. Back then, failures were rather common and they required replacement after 25-30 hours of run time (high-compression race engines).

The JE's we now use are a custom configuration made to our spec to aleviate some of these issues.

[MotoSook]

Yes! I knew you would have the goods....thanks Steve. I may be calling you on those JE pistons.

[randywebb]

Steve - have you guys seen anything different in the last year or two? Like a higher (or lower) failure rate? same re wear rate?

[Steve@Rennsport]

Randy:

In the last year, we saw a brand new set of JE's come apart at Fontana after 12 hours of dyno time (for EFI mapping) only. Broke across the wrist pin bosses.

Aside from that, no other issues with other street & race engines using similar products. Wear rates unchanged, however we did not go through very many other engines already in service. I like to think that our stuff holds up very nicely over the long run.

In the past 24 months, most have been either new 3.8 builds using Mahles, some 930's with 98mm Mahles, and a few 2.8 & 3.4 race motors with JE's.

[randywebb]

Thanks.

I hope mine hold up for a few years... of course, not driving the car since it is perpetually undergoing different mods, is one strategy to prolong the life of the moving parts...