Life expectancy of J&E's in a street engine

[Shuie]

I've read that Mahle P&C's are preferred over J&E's for a street engine. I have no first hand experience with either. What is a reasonable life expectancy for a set of J&E's in say a 9.5:1 mostly street 3.0?

TIA

[kstylianos]

Good question. I'll be watching this thread.........

Edit: I have 9.7:1 JE's in a single plugged 3.0. I know they'll go at least 1500 miles

[1fastredsc]

Yeah, i'm also curious, my dad's running 8.5:1 comp je's in his 951. It's soother than it was before without balance shafts (they were deleted), and it's quieter running.

[jgparker]

Mine have made it to 400 miles without wearing out yet. I'll let you know.

[dd74]

I've heard the same thing.

Does anyone know the difference between JEs and Mahles?

[dwightp]

I'm interested also but cautious. I would expect that different machining between J&E pistons would account for longevity. Maybe someone can offer an argument as to wether or not that's the case too? Hate to draw a conclusion from one cut of piston.

[magic930]

Wayne's book recommends them as a viable alternative. JE has been making pistons for a long time for many applications including NASCAR which is an extreme stress application, they also make motorcyle pistons which are again a high RPM application. When it comes right down to it it is really the interaction of the rings to the cylinder wall which counts. Both Mahle and JE are forged pistons which are machined to a finished product and basically just need to hold the rings and rod and dissapate heat. I will be ordering a set soon for my rebuild.

[ChrisBennet]

magix930,
Are you sure the Mahle are forged?
-Chris

[magic930]

I have only a little understanding of metallurgy but I would think that they would have to be. "Forged" essentially means they are made from one piece of metal which is poured and pressed into a mold, and then cured in a controlled environment to ensure maximum strength for the application, the curing is actually very important since cooling at different rates aligns the molecules in different directions.

[Steve@Rennsport]

Chris:

All of the non-OEM Mahle (special) P/C's use forged pistons and most of the larger OEM ones are too.

There are major differences in the alloys that Mahle and JE use. The Mahles are much denser (heavier) than the lighter JE's. Mahle forged pistons can run at .00015; something that will seize any JE. Those need .003 or more. Mahle ring lands last longer, too.

Frankly, very few if any JE's have the long-term track record that the Mahle ones do. These are typically used in racing applications where they are thrown away every 120 hours or less in amateur racing and most pro's toss them after each race.

I use Mahles in street engines where longevity and durability are more important than just flat-out power. I like JE's in many race engines for their light weight and CR flexibility. Apples & Oranges for me, anyway.

[Wayne 962]

While I don't disagree with Steve, there are other opinions on this issue. While Mahle indeed has been around for quite awhile (can we say 917), Porsche owners seem to revere them and use them whenever possible (which is not a bad thing). JE pistons are often used in custom applications, like custom turbo setups. Hence, the JEs tend to be subject to non-ideal circumstances and generally abused quite a bit more than Mahles. It is important to keep this in mind when comparing them to Mahles.

I do not have actual comparative test results of Mahles versus JEs, but all the people I know who run them in stock applications have had no problems with them. The bottomline is that if you use the JEs, you will not be putting your engine rebuild at risk - they are more than adequate replacements.

-Wayne

[Shuie]

Thanks guys! I really appreciate the help. Im still in the early research stages of possible future engine configurations.

Basically, if the J&E's will last the service life of the engine I would probably go with them. I just would not want to spring for the Mahles if I dont need the longevity.

I would think that any piston used in these cars would have to be forged. magic930, what you are decribing sounds more like a casting. Are there actually people out there casting pistons?

[J P Stein]

I disassembled a 2.4L T motor and got a real good look at the pistons (Mahle). They are cast with steel.....er...gussets cast in place below/around the pin bores. Heavy, but with unknown mileage, in nearly perfect shape.

I have held 90mm Shasta & Mahle RS spec (forged) in each hand.
WAG....the Shastas (KE forgings) were 2/3 the weight of the Mahles. A quick pass with a micrometer showed that there is quite a difference between the 2.

I been running the Shastas for about 2.5 years...mostly autocross...prolly less than 5k miles total. I would like to tear the motor down to see how "things" are holding up, but for now, I can't justify the expense.....the motor is still pretty stout. It does lead a hard life, tho. Smoke on start-up is becomming a bit alarming....sometimes...mostly after it sits for a long time. No smoke when it's up to temp....yet (insert crossed finger smiley here).

[1fastredsc]

Steve, i'm not sure if i understand your post about tolerance, i thought air cooled motors where high tolerance motors anyhow, so .00015 and .003 shouldn't matter unless i missed something.

[Randy Webb]

I asked Jerry Woods about this -- Mahles have a better track record, the JE's fail sometimes... then he paused for a while and said: the Mahles fail too. JW is conservative in the snese that once he finds something that works really well, he stops exploring.

So, as Steve W. said above, it seems to be a track record thing. Mahle has been around for ages and their quality is well-known. You should be fine with either. Or you could ask questions of other race builders -- you have two from the W Coast so maybe try the E coast for other opinions.

But I think you won't find a 'real' answer -- nobody (except the manf.s who aren't going to give out trade secrets) does a statistical failure analysis. That's what you need to really be sure. We are just starting to get that sort of data for tires as a result of the Firestone debacle. We'll never get it for pistons.

[wm711]

Ive had JE pistons with 10.5 CR in two engines ive built. two separate engines. the first one did tons of DE, plus quite a lot of street driving, probably 5000 HARD miles. Webber 46, elgin 306/288 cams, headers... ran great for two years, then sold the car-kept in touch with new owner-still no problems. They have been in the car for 6 years now. The second I built exactly the same way, sold to a friend before ever running. He has reported no problems-that engine is 3+ years old-

[cnavarro]

We've been including custom JE pistons with most, if not all of our Nickies cylinders, and have not had any complaints whatsoever. I'm getting to the point that I have started sourcing off the shelf pistons for some applications, like SRP pistons for the 103mm type 4 nickies, but have not decided on whose pistons to sell with the 911 cylinders, even at all. Does Mahle motorsports sell forged pistons for the various bore sizes, sans cylinders? Does anyone else have any suggestions on a preferred piston choice to include with my cylinders. What do you think Wayne?

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

[Wayne 962]

It is my opinion that JE's get a bad rep, primarily because they are used in custom applications wher ethe designer of the engine may not have made all of the 'correct' choices for longevity.

-Wayne

[Bobboloo]

Charles, Those are some beautiful cylinders you're making. I'm building a 2.8 RS motor in the near future and will look you up when I'm ready to buy.

[cnavarro]

Thanks Bobby!

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