CP vs. JE pistons

[sempaipaul]

Good morning,

I am currently having my engine built by a fellow Pelican member and we're installing new pistons. The plan was to go with 964 reground cams and JE 9.5:1 pistons. I have since, however been told about CP pistons. Apparently rumor has it they are better, more quality equipment.

Can anyone speak to the benefits of using one brand pistons over the either? The price difference of $100-200 is not too big of a factor in the grand scheme of things.

Thanks
Paul

[Henry Schmidt]

We're finding the CP pistons are higher quality and the forgings offer more versatility.
Although we still offer the JE option, my first choice is CP.

[prschmn]

+1 with Henry-Wossner isn't a bad choice either-and if you're made of money--Omega

[Spenny_b]

Originally Posted by prschmn

+1 with Henry-Wossner isn't a bad choice either-and if you're made of money--Omega

I was fortunate enough to meet Fred, aka Mr Omega a few years ago - he supplies my mate with their pistons for Duratec, Hyabusa, Vauxhall "Red Top", etc.

He was telling me that every comtemporary Ducati WSB and MotoGP bike has run with their pistons, and have never suffered a failure. Unfortunately he couldnt give me a factory tour, as at the time they were doing some secret work for a particular manufacturer of the (then new) turbocharged race motors...1.5l...v6....

[al lkosmal]

I'm only seeing listings for 3.0 and larger engines. Does CP make pistons for early 911s....90mm and smaller?

regards,
al

[Henry Schmidt]

Originally Posted by al lkosmal

I'm only seeing listings for 3.0 and larger engines. Does CP make pistons for early 911s....90mm and smaller?

regards,
al

Yes
Any size you want.
I stock 9.5:1 and 10:1 90mm on the shelf.

The dome designs are basically the same. The difference is in the forging.
I am also impressed with the ring land configuration of the CP.
Weight seems to be 60 grams ( 15%) lighter on the CP even before lightening.

[al lkosmal]

Henry.......I just ordered some je's yesterday can you pm me with pricing for 90mm, 9.5:1 and 10:1....for future reference.

regards,
al

[chris_seven]

Originally Posted by prschmn

+1 with Henry-Wossner isn't a bad choice either-and if you're made of money--Omega

Omega are not so bad at around $1350 a set but lead times are quite high and minimum order quantities are a problem if you only want one set.

We use Omega in all of our 2.0 litre engines and have done for a while.

CPS in Italy are good and similar money to Omega - they make a piston in 4032-T6 rather than 2618 so expansion is slightly lower and ring grooves are likely to be more wear resistant. We have used them in several small capacity Coventry Climax engines, one 911 engine and in a Group B Lancia 037 motor.

CPS Special Pistons - Home

Woessner pistons are quite good for the price and I believe they are also 4032-T6.

The coating quality is not as good as Omega or CPS but they are a lower price.

For the smaller engines I prefer the design of the Omega and CPS pistons but the 3.0 litre Woessner pistons are very good value.

[David Borden]

Are these the CP pistons you guys are referring to ? http://www.cp-carrillo.com/pt-3507-pistons.html

Do they have options for 3.2 SS and carb / after market injection?

David

[Edelweiss]

We have tried them all:

Omega - outstanding good, using two different materials one with more silicium one with more copper and most important they do a special heat treatment which makes the biggest difference from my point of view - since T 6 is not ideal for a piston.

CP - very good with the touch of finesse

JE - good, no issues at all

Wōssner - no comment ...

Best reg.

Dirk

[robcf]

Originally Posted by Edelweiss

We have tried them all:


Wōssner - no comment ...


Dirk

Is this because you havent used Wossner?

[chris_seven]

Dirk,

I would be interested to understand why you think a T6 Temper is not ideal for a piston? I believe it depends on the basic material selection.

I would agree that 2618 is commonly used in a T61 temper which is likely to result in an 'under-aged' condition following the precipitation treatment.

I think that this type of treatment will produce more stable properties in terms of creep and creep rupture as this alloy can be prone to overaging with time at temperature causing a reduction in ductility.

Early developments of alloys like 2618 were made by Rolls Royce as a material specified as RR58 which was used in a T6 condition.

4032 will behave in a slightly different manner due to its significantly lower copper content and if it is not quenched fully and consistently will not age correctly following solution treatment.

The slight increase in residual stress caused by the more aggressive quench should be outweighed by the slightly higher tempering temperatures used for 4032 Alloys and as such should not cause too many issues.

I must say I tend to favour the use of 4032 Alloys for pistons used in normally aspirated engines as they are generally slightly stronger at the combustion temperatures involved, they have lower expansion and higher scuff resistance.

I would agree that 2618 would be a better choice for Turbo charged engines due to its better long term creep resistance.

I also believe that cast pistons are normally used in a T5 temper.

In general the metallurgy and selection of piston materials is very interesting and I am very surprised that Metal Matrix Composites (MMC) have not made more impact in this area unless cost is prohibitive.

I would have thought being able to use buzz words such as Nano Technology would overcome this problem

[Edelweiss]

Dear Chris,

for a very long time ( approx 20 years ) I was exclusively using Mahle 124 as the material for our street / sport and race engines.

For several reasons ( cost related ) Mahle is not using this wonderful material any more for decades now.

All Porsche 934 / 935 / 956 / 962 works Pistons where made of Mahle 124.

You will know about the specifics of this material and its high degree of silicium inside.

In the more common and now modern alloys silicium was replaced more and more by copper as these materials are defining the wear out on piston to cylinder wear and sliding performance ( pardon me - maybe the wrong terminus ).

However here comes the problem about using the simple and cheap T6 process:

The T6 temper is giving the maximum hardening into any aluminium.

When the piston dome in a running engine is reaching a temperature of approx 300 deg. Celsius the so called diffusion process is starting to influence the metallurgical structure inside the alpha mix cristal and so it is changing the aluminium in two major points:

1. It is getting softer

2. It grows in volume to the same degree

Piston reality is then that the piston is loosing its so called geometrical stability.

Most time you see a piston with a bigger diameter at the ring zone and falling in at the skirt.

So under the line a good / perfect piston is running through a temperature treatment which makes him hard enough to survive but soft enough not to get influenced by temperature when in use.

This temperature treatment is using a pattern that was developed in years and is different at different alloys.

Best reg,

Dirk

[Edelweiss]

Let me bring it over this way:

They are cheap, they are shiny and they come in a nice box ... You better keep 'em there ...

Originally Posted by robcf

Is this because you havent used Wossner?

[Raceboy]

What about Wiseco?

[chris_seven]

Dirk,

Very, very interesting.

I would agree that M124 is very similar in terms of composition to 4032 but as used by Mahle appears to have a strength level lower than a T-6 temper.

I would like to understand the reason for this as 4032 should be less prone to losing its properties after 'time at temperature' than 2618 due to the different nature of the precipitate particles.

I have hardness tested some well used 1969 911S pistons and obtained values I would expect to find for a Eutectic Silicon Alloy with a strength of 200/250 MPa.

One of the issues with 4032 alloys is that the time between quenching and subsequent aging is critical otherwise 'pre-ageing' occurs and the alloy will not respond so well to subsequent age hardening.

I am sure that Mahle had a reason for using a relatively low strength condition but it is not immediately clear as to why.

I would agree that 2618 in a T6 condition will lose strength relatively quickly depending on temperature and using a T61 Temper should help to improve the situation as there will be less Copper in the superstaturated matrix when the part is quenched in boiling water.

Mahle now seems to favour M-SP25 for many of its Motorsport pistons and certainly advise its use for Turbo engines. This alloy is very similar to to 2618 and Mahle quote a strength condition I would expect to find from a T61 temper.

I am surprised that a T61 temper and overaging causes significant distortion as the incoherent particles will only be a 2-300 Nanometres.

I have been trying to find some data but without success and would be keen to learn more.



https://www.fsb.unizg.hr/miv/MSUI/KonMot/KonMot_2014/Pistons%20and%20Engine%20Testing_(Mahle_GmbH)_View eg+Teubner-2012.pdf

[Edelweiss]

And again Chris you are so right with what you say from theory and practical experience !

When forging M 124 / 125 it is essential to keep a certain temperature during the material flowing process.

After the forging you have to keep it there for a specific time.

When the concentrate cooling down is done you need to use a special oil where the forging is dipped in.

Then the forging gets slowly down to room temperature.

Rough machining is processed.

First stress relive temperature treatment.

Two more machining and heat treatment steps before final machining and tempering.

The major temperature pattern process is running 18 hours.

By the way there was a European metal matrix project that was running ifinally ended because of F1 rules changed. You know that MM materials are used by Toyota for their 1800 ccm engines ? They did their blocks from it and you need to use ferrostan coated Pistons like used in Alusil.

Best reg.

Dirk

[Edelweiss]

Hi Peep,

hope you're doing fine !

15 years ago these Pistons where frequently collapsing on the German Autobahn.

I inspected them an found a bad construction.

Totally wrong in taper and ovality.

Three years ago we did a Opel Kadett GSI 2,0 L 16V Gruppe A engine using this Pistons as the customer was buying a package where these Pistons where integrated.

It was 87 mm bore to 86 mm stroke.

Inspected them - was surprised: geometry was all right.

We ended up with a static compression of 12,8 : 1 and making reliable 240 HP.

Engine is still running strong - no issues.

I would use them again.

Best reg.

Dirk

Originally Posted by Raceboy

What about Wiseco?

[Ultrafast993]

For what it is worth, no issues with JE's, got an engine with over 50k miles on them, cheers.

[911WAM]

Henry, Dirk and all the pro's

im a little late to the party but could do with some input on the CP vs JE discussion for my '85 3.2 US Carrera

will it be possible to replace the pistons with 3.2, or upgrade to 3.4, CP's or JE's without re-plating the cylinders with Nikasil?

the pistons under consideration, both JE and CP are made from the 2618 alloy however the JE's have the anti friction skirt coating.