custom Mahle pistons are useless.. major vendor fail

[NOPDK]

After ordering custom Mahle 3-3.2 conversion pistons 10-1 compression for my engine from a respected vendor which was specifically spec'ed to be used with an aggressive camshaft with high lift valves the final result is useless. At the initiation of the process my engine builder (30+year experience with this) spoke with the vendor to explain the engine being built and answer any detail questions to be sure they made the correct part. I had my engine builder do this directly so that nothing was missed in the process. This has been a 3 month process with error after error. After 5 weeks the first set of pistons shows up and it has the incorrect wrist pin diameter. They gave me the turbo writs pin size on a 3.2 conversion piston. So this shop takes the Mahle piston back and puts a rush with Mahle to reproduce a replacement with the correct wrist pin. I explained I had a rally to get to the end of September and this was now pushing my timeframe. We also rediscussed that my engine was using aftermarket aggressive camshafts with high lift valves. Additionally a "fire ring" on the cylinder head was specified. After waiting another 3 weeks the pistons show up from Mahle but with no fire ring. The vendor machines in the fire ring which adds an additional week. The pistons plus cylinders plus rings show up at my engine builder. He does his initial layout and quickly realizes the the valve pockets are of stock high and will not work with my specified from the beginning high lift cams/valves. At this point we are gravely behind schedule and the vendor tells us to at our expense machine the pistons to add the valve relief pockets needed as there is not time to ship back and forth to him for them to do it. My engine builder lays this out with his machine guy, does one piston, that clears the valves so the other 5 are done. That added an additional 4 days we didn't have. In the mail I receive a bill from this vendor charging me the shipping to get the replacement secondset of pistons to me as well as charging for the fire ring machine work. I was flabbergasted they would try to charge me with this. After a few emails back and forth they retracted that bill which I cannot believe they sent in the first place My engine builder then starts to mock up the engine and and while the valves clear fine the layout of the piston (I'm leaving the zone where I have the technical understanding to explain this fully)and how it mates to the cylinder makes for only 9.6:1 compression. The pistons will not hold the compression they were made to. My builder has built hundreds of these engines and gave me a string of technical problems with the pistons. So after explaining to this vendor twice what was needed they failed on multiple accounts completely screwing up my build time frame and costing MANY hours of my engine builders very expensive time. The pistons they made would work in a stock 3.2 motor running stock cams. not the 3-3.2 conversion motor running hot cams that we spec'ed these for. I have now overnight ordered a set of 10.5:1 JE pistons with the necessary valve relief already inplace to be used with the new Mahle cylinders. By having custom Mahle pistons produced for my engine I thought I was including the best of the best parts. The Mahle pistons are useless to me and might as well be paperweights. I have a call out to the vendor who wasn't there Friday. If they do the right thing and refund my money for the piston portion of the charges then I'll move on as lesson learned. If not I will be happy to share the name of the vendor with any in the porsche community who will listen. That is not the shop to use to get the details right on a custom build If they take the pistons back and refund my money then at least they have a moral compass. The lack of attention to detail is shameful. As well I will fight the charge through Amex that has a good track record of protecting the consumer in these situations. I'm not looking for a fight, I just want my money back on the useless pistons so I can pay for the JE ones I had to rush order. Will I make my rally now? We'll see. At best car will make it on transport and my first drive of her will be on the rally. This has been a more stressful process than it needed to be. The details of my build are in this thread: http://www.early911sregistry.org/for...844#post756844

[uai]

AFAIK Mahle doesn't sell custom pistons.
For Custom stuff they sell forgings that will be machined by others, and you do not order directly from Mahle
In the Stuttgart area for a custom Mahle piston I'd go to Wahl.
Cheers

Uli

[NOPDK]

AFAIK Mahle doesn't sell custom pistons.
For Custom stuff they sell forgings that will be machined by others, and you do not order directly from Mahle
In the Stuttgart area for a custom Mahle piston I'd go to Wahl.
Cheers

Uli

In the USA Mahle Motorsports does produce custom pistons. Their accuracy relies on the specs provided to them by the vendor placing the order.

http://www.us.mahle.com/mahle_north_...ports/contact/

[edmayo]

It has always been my experience that once you go beyond dead stock components it is up to the engine builder to custom fit the pistons to that particular engine, saying you'll be using a high lift cam so make the pockets to fit that is like saying I got big feet, so send me shoes that will fit. Mahle would have to know the exact lift, duration, and timing of the cam in use, and even then I don't know if they would be able to make a computational model that would let them exactly cut the pockets for your application. I have always assumed that when I use non-stock pistons that some valve pocket cutting and or other machine work MIGHT be necessary. Of course I have no way of knowing what was said between vendor and manufacturer. Compression ratio is just as hard in that they may not have known your actual combustion chamber volume, I don't know where they draw their chamber displacement number from to be honest.

[Flunder]

Welcome to the world of custom engine building...Why doesn't the builder just fly cut the valve pockets on the crowns of the Mahle pistons to provide sufficient clearance for the valves?

[Olivier]

My little experience on this topic.

Yes, Mahle will make customs pistons in EU. But, they'll have to fit in existings forgings blanks AND there will be a min order ( not small, aand if yr project require new forgings, it is Very costy!)

I did once design some custom high comp ratio pistons. All that Ed said is true. I was on the engine builder side, and we had to proruce drawings of the pistons.

I did it with a motorist. I think it took us about 2 weeks of work. We had available the cad model of the chamber. We played both with the cad software and some exel spreadsheet.
Exel was used to calculate the movmt of both the piston and the valves, and then translated into cad...
Many parameters as you know such as cam profile, rocker ratio, con rod lenght, stroke, engine block deck height and head gasket thickness.

We wanted to achieve about 15:1 ratio for a fun ethanol engine.
It took me quite some time as mentioned to put material on piston s head while clearing head and valves.

We were.successfull, and the engine ran very well upto 8k if my memory is ok. I remember that in some places, there was less than 1,5 mm of clearance between the piston and the head!

But, as Ed say, without knowing what exaclty was said betwen yr engine builder and the seller, it is pretty hard to make a point on it... Responsability might be hard to tell.

Good luck with yr engine!

Olivier

[Richardnew]

Anytime you go to high performance aftermarket parts you can expect problems. It's just the nature of the game. Stuff never works the way the company that sold you the stuff said it would. When you buy an aftermaket part you simply have a starting point. Getting the part to actually work is your responsibility.

Richard Newton
Car Tech Stuff

[gled49]

There was a time when Mahle asked some engine builders around the country about building custom piston and cylinder sets, and asked for input. The responses included special rings, moving the pin bosses for compression height for long rods, dome heights and valve pocket deep enough for high lift cams with dome thickness so they won't break thru. In the end they didn't do anything. Beware of machining valve pockets and leaving enough dome thickness. In Mahle's defense, I removed custom JE's and long rods, installed stock 98mm RSR P&C's, lowered the compression 1/2 point and picked up 20 HP. I wish there tolerances were like they were 20 years ago. I still like Mahle. Gled