21 replies to this topic

[andywilson]

hi all after putting my old z20let pistons on ebay i've had a fair few questions asking if they're mahle pistons... had a quick look and they are what does this mean? are they better than some other ones? probably should have researched a bit harder, but from what i gathered on here all z20let pistons are the same! any thoughts? thanks, andy

[Nev]

Andy, ring me, I'll tell you all about your options/types and pros and cons

[etrusco]

Nev, can we have details about the lovely chocolate z20let Mahle pistons as well, or should we all give you a ring? I'm completing a Regelin stage 3.5 VXT conversion (quoted for approx. 300hp)and would like to know how long my stock chocolate/marzipan internals will last, with about 5 trackdays a year and attack mountain pass driving, with revs below 6500rpms. Cheers

[Nev]

Ok here goes. Z20LET pistons. Apparently (and I dont have proof of this) there are 2 types of these. Type 1: Most are non forged and ok for approx 320 BHP. Type 2: However, I have heard that certain Z20LET pistons are the Mahle semi forged ones. If this is the case then these are good for 600+ BHP. Z20LEH pistons. Made by Mahle, semi forged, good for 600+ BHP. CR = 8.5:1 C20LET pistons. Made by Mahle, semi forged, good for 600+ BHP (these are what I have in my engine). Their pockets are slightly diff (deeper) that the Z20LET ones. Can have their crowns machined down to create a CR of approx 8.3:1. I short there is NO NEED to buy expensive forged pistons. Z20LEH ones are more than sufficient.

Edited by Nev, 07 July 2011 - 07:43 AM.

[etrusco]

Ok here goes.

Z20LET pistons. Apparently (and I dont have proof of this) there are 2 types of these.
Type 1: Most are non forged and ok for approx 320 BHP.
Type 2: However, I have heard that certain Z20LET pistons are the Mahle semi forged ones. If this is the case then these are good for 600+ BHP.

Z20LEH pistons. Made by Mahle, semi forged, good for 600+ BHP. CR = 8.5:1

C20LET pistons. Made by Mahle, semi forged, good for 600+ BHP (these are what I have in my engine). Their pockets are slightly diff (deeper) that the Z20LET ones. Can have their crowns machined down to create a CR of approx 8.3:1.


I short there is NO NEED to buy expensive forged pistons. Z20LEH ones are more than sufficient.

very useful and exhaustive report Nev
Any news of your dragster project?
Cheers

[steveboyslim]

Ok here goes.

Z20LET pistons. Apparently (and I dont have proof of this) there are 2 types of these.
Type 1: Most are non forged and ok for approx 320 BHP.
Type 2: However, I have heard that certain Z20LET pistons are the Mahle semi forged ones. If this is the case then these are good for 600+ BHP.

Z20LEH pistons. Made by Mahle, semi forged, good for 600+ BHP. CR = 8.5:1

C20LET pistons. Made by Mahle, semi forged, good for 600+ BHP (these are what I have in my engine). Their pockets are slightly diff (deeper) that the Z20LET ones. Can have their crowns machined down to create a CR of approx 8.3:1.


I short there is NO NEED to buy expensive forged pistons. Z20LEH ones are more than sufficient.

There is a need to buy forged pistons it just depends on what the car/engine will be used for.
Forged pistons run a bigger piston to bore clearance and some rattle when cold,(some of the well known brands are terrible) but the are stronger even than the LEH/C20LET version (which have a 'P' designation).
The ZLET pistons (no 'P') are cast and they break the ring lands with the increase in cylinder pressure and if poorly mapped deternation.
All Mahle replacement for these turbo engines C20LET/Z20LET and LEH are made from the same forging with the 'P' designation.
Some aftermarket forged pistons are not much more money than Mahles.

Steve

[Grov]

Hello All, just to add some information for you all on MAHLE pistons. I actually work for MAHLE, but am posting here in an unofficial capacity All MAHLE pistons are either forged or cast, not "semi forged". The raw piston number is marked on the inside of the piston and denotes the manufacturing method of which there are a few, but all you are interested in is if the number is xxx P xxx. The P indicates "gepresst", literal translation "pressed" or forged. Squeeze cast pistons are also produced by MAHLE but these will not use the P in the raw piston number. The info I have on *20 le * pistons are as follows: Z20LET = OE Supplied by MAHLE, cast & available aftermarket Z20LEH = OE Supplied by MAHLE, forged, not currently sold aftermarket C20LET = OE supplied by MAHLE, forged currently available aftermarket. The Z20 & C20 forgings are different, although many people use the C20LET piston in the Z20 - I believe the bowl is modified to suit. Regarding the extra piston to bore clearance, this is not required beacause the piston is forged but depending on the type of piston alloy used and in general terms the amount of silicone in the alloy. Many aftermarket piston manufacturers only produce pistons in 2618 or RR58 alloy which has a higher expansion rate, hence they recommend larger piston to bore clearance. Many of our OEM forged pistons run around .002" bore clearance and are perfectly quiet when cold. 2618 alloy is more resistant to detonation damage because it is not such a brittle material as a high silicone piston (such as M124 alloy used in the C20LET piston), but you have a trade off of reduced piston life and increased wear.... There is a massive amount of information available on the internet on pistons alloys and which is best and what you should use and who makes the best pistons - a lot of it inaccurate and information from a riend of a friend who knew someone that told him ;-) Finally ALL MAHLE replacement pistons are manufactured to the OE specification and with the same toolings - we would not use a different casting / forging to the OEM piston for aftermarket. The only exception to this is for Motorsport pistons where the product is designed for uprated performance. These parts are sold as MAHLE Motorsport and not MAHLE Orignal (which is always OEM design / specification). There are currently no MAHLE Motorsport psitons availabel for these engines...... OK, the can of worms is open, feel free to ask anything I haven't covered Grov.

[Nev]

For completeness here is Mahle's full code designations: In the inside of every MAHLE - Piston you can find a casting number. This number consists out of two numbers, then a letter and again two numbers. From the letter you can find out of what kind the piston is: D... Duotherm piston F... Squeeze-cast piston KB... Ferrotherm piston L... Solid skirt piston P... Forged piston V... Auto-/Hydrothermik piston/ Auto-/Hydrothermatik piston For example: A piston with the casting number 96 P 26 would be a forged piston.

[techieboy]

Great info Grov.

[alanoo]

Finally ALL MAHLE replacement pistons are manufactured to the OE specification and with the same toolings - we would not use a different casting / forging to the OEM piston for aftermarket. The only exception to this is for Motorsport pistons where the product is designed for uprated performance. These parts are sold as MAHLE Motorsport and not MAHLE Orignal (which is always OEM design / specification). There are currently no MAHLE Motorsport psitons availabel for these engines......

OK, the can of worms is open, feel free to ask anything I haven't covered

Grov.

Grov,

I guess you could give an answer I'm looking for since a very long time... Can Mahle motorsport provide custom pistons or not ?
Was never able to find an answer to that...

[Grov]

Hi all, Nev, thanks for the list of raw piston identifiers. The first digits also indicate the bore size excluding decimal places so 86 P is a forged piston from 86.00-> 86.99mm finished diameter at standard size. All raw numbers are now 3 digits, 1 letter, 3 digits with 0's filling in, but on older parts they still show as 2,1,2 as it isn't cost effective to change the tooling. alanoo, the short answer is no, we don't make one off custom pistons. The longer answer is that if we have a part in range then we can modify the design to specific customer requirements for very small batches. Problem is we do not have the C20 / Z20 pistons in the Motorsports range.... yet I work with our motorsport piston & bearing plants on a little side project and these parts are on the radar.... Grov.

[steveboyslim]

Hello All,

just to add some information for you all on MAHLE pistons. I actually work for MAHLE, but am posting here in an unofficial capacity

All MAHLE pistons are either forged or cast, not "semi forged". The raw piston number is marked on the inside of the piston and denotes the manufacturing method of which there are a few, but all you are interested in is if the number is xxx P xxx. The P indicates "gepresst", literal translation "pressed" or forged. Squeeze cast pistons are also produced by MAHLE but these will not use the P in the raw piston number.

The info I have on *20 le * pistons are as follows:

Z20LET = OE Supplied by MAHLE, cast & available aftermarket
Z20LEH = OE Supplied by MAHLE, forged, not currently sold aftermarket
C20LET = OE supplied by MAHLE, forged currently available aftermarket.

The Z20 & C20 forgings are different, although many people use the C20LET piston in the Z20 - I believe the bowl is modified to suit.

Regarding the extra piston to bore clearance, this is not required beacause the piston is forged but depending on the type of piston alloy used and in general terms the amount of silicone in the alloy. Many aftermarket piston manufacturers only produce pistons in 2618 or RR58 alloy which has a higher expansion rate, hence they recommend larger piston to bore clearance. Many of our OEM forged pistons run around .002" bore clearance and are perfectly quiet when cold. 2618 alloy is more resistant to detonation damage because it is not such a brittle material as a high silicone piston (such as M124 alloy used in the C20LET piston), but you have a trade off of reduced piston life and increased wear.... There is a massive amount of information available on the internet on pistons alloys and which is best and what you should use and who makes the best pistons - a lot of it inaccurate and information from a riend of a friend who knew someone that told him ;-)

Finally ALL MAHLE replacement pistons are manufactured to the OE specification and with the same toolings - we would not use a different casting / forging to the OEM piston for aftermarket. The only exception to this is for Motorsport pistons where the product is designed for uprated performance. These parts are sold as MAHLE Motorsport and not MAHLE Orignal (which is always OEM design / specification). There are currently no MAHLE Motorsport psitons availabel for these engines......

OK, the can of worms is open, feel free to ask anything I haven't covered

Grov.

When I checked the Mahle pistons available were of the forged type and were listed as suitable for both the ZLET and LEH, that is they supersed all previous types, but do not have the OE skirt coating the LEH does from the factory.
The capacity of the bowls are different as are the valve cut outs, but have the same forging numbers on the underside.
If you work for Mahle you should have access to more information than me.

Steve

PS If you do work for Mahle, can you get a FORD BDT block nikasil for me ?
The original Mahle coating is still the best and the motorsport devision used to do it for aftermarket, but I believe they stopped low volume work some year ago.

Edited by steveboyslim, 07 July 2011 - 06:40 PM.

[Grov]

Hi steveboyslim,

if you check our online catalogue at www.mahle-aftermarket.com (follow the link on the right) you will see we only list aftermarket pistons for the LEH and they are cast, as per the OE piston. We wouldn't supercede a piston from cast to forged unless the OEM did the same, like wise we wouldn't delete the skirt coating unless it was an OEM specification change. I'm not sure who is quoting the supercession, but my bet is that the pistons are C20LET pistons - forged but fully tin plated rather than skirt only grafal.

If you can get me a raw piston number from these Z20 pistons I'll dig out the drawing and post bowl / valve pocket data for you to compare with what you have to check if they are machined C20's.

You're right that we stopped the low volume nikasil business, I'd have to check but from memory we work exclusively with only on German aftermarket company for replating now and that is mainly Porsche liners. I'm amazed how popular the BD engines still are, we've put the bearings back into production as people were not too happy with the other aftermarket offerings.

Grov.

PS dont expect a quick reply on the piston data, I'm on holiday till tuesday. If you doubt where I work (we can be anyone on the internet!) PM me and I will give you my full name and I'm sure a quick google will turn up a couple of hits, all I ask is you keep it confidential as I'm posting here "unofficially"

[steveboyslim]

Hi steveboyslim,

if you check our online catalogue at www.mahle-aftermarket.com (follow the link on the right) you will see we only list aftermarket pistons for the LEH and they are cast, as per the OE piston. We wouldn't supercede a piston from cast to forged unless the OEM did the same, like wise we wouldn't delete the skirt coating unless it was an OEM specification change. I'm not sure who is quoting the supercession, but my bet is that the pistons are C20LET pistons - forged but fully tin plated rather than skirt only grafal.

If you can get me a raw piston number from these Z20 pistons I'll dig out the drawing and post bowl / valve pocket data for you to compare with what you have to check if they are machined C20's.

You're right that we stopped the low volume nikasil business, I'd have to check but from memory we work exclusively with only on German aftermarket company for replating now and that is mainly Porsche liners. I'm amazed how popular the BD engines still are, we've put the bearings back into production as people were not too happy with the other aftermarket offerings.

Grov.

PS dont expect a quick reply on the piston data, I'm on holiday till tuesday. If you doubt where I work (we can be anyone on the internet!) PM me and I will give you my full name and I'm sure a quick google will turn up a couple of hits, all I ask is you keep it confidential as I'm posting here "unofficially"

Some of the data is in the Mahle catalogue(paper) which designates the pistons as forged for C20LET and lists other pistons as suitable for ZLET/LEH also designated as forged.
When I had some OE LEH pistons (I do not have any at this moment)the forging numbers on the underside were the same as the C20let, but as you say they are machined differently.
I am involved with a small company which has re-cast the BDA/G engine and am vey interested in speaking to anyone who can help with nickel ceramic coating.

Steve

[Grov]

Hi Steve, back in the office and just checked the drawings for both Z20LEH and C20LET. The forging tool used for both parts is the same (86P47), however the alloy used for the C20LET piston is M124 and the alloy used for the Z20LEH is M142 - you should also see these numbers inside the piston. I can't give the complete compostition of these alloys, but the properties of M142 make it stronger and more resistant to detonation damage than M124. There are also a number of machining differences, the most noticable is that the Z20 piston bowl is around 5cm3 greater volume than the C20. Ring layout is also different (1.2mm, 1.5mm, 2.5mm Z20 & 1.5mm, 1.5mm & 3.00mm C20). I haven't checked the ring specs but assume that the Z20 top ring is steel nitrided due to its reduced height, the C20 from memory is moly. The Z20 piston uses grafal skirt coating, the C20 piston is completely tin plated. The Z20LET piston is a cast, solid skirt piston (086L061) alloy used is M145. The bowl is approximately 0.5cm3 greater volume than the Z20LEH, and a larger diameter. Ring sizes are the same as the Z20LEH, 1.2mm, 1.5mm, 2.5mm C20LET pistons are sold Aftermarket under part number 011 79 * * (last two digits denote size), the Z20LET pistons under part number 012 20 * *. Z20LEH pistons are not currently sold aftermarket. In short, if the bowl gives you the desired CR then the Z20LEH piston is the better option due to the alloy used and the ring pack will be lower friction. Unless people are looking for really big power or looking to use nitrous then Z20LEH pistons should be more than suitable, other pistons may even be heavier than the OEM piston. The factory piston to bore clearance is 0.05mm which will also make them a lot quieter than some aftermarket forged pistons. Grov.

[Nev]

Grov, Thanks a lot for some decent info on Mahle pistons. This is the kind of detailed and precise info that should be on the Mahle website, why isn't it ? I have just spent hours and hours trying to get decent info like this from a variety of manufacturers for my recent project (not just for pistons, but all sort of engine components). Absolutely none of the manufacturers seem to care about providing this sort of info about their own products when clearly that is exactly what a website should be doing. In the end I had to rely on friends and 'street knowledge' to make a guess at what was best to use. I even rang Mahle up in Germany but the man on the end of the phone was next to useless. I strongly suggest you talk to your website guys and start putting this kind of stuff on your website. It will help after market sales, provide prospective purchasers with confidence, add credability to your company and generally be professional. Thanks and regards, Nev.

Edited by Nev, 12 July 2011 - 12:57 PM.

[Grov]

Hello Nev, The problem we have is the website is controlled by our communications department and not by technical people - I guess that ultimately we are a very large organisation (50,000 employees and growing) and to include information about everything is impossible. As I am a bit of a saddo and technical details is my "thing", I tend to try and provide information where I can (even when it's against the rules - like posting on forums is, hence unofficial postings here). Even if I can provide general engine information that is not relevant to products that we produce, I will. Also if I believe another product will best suit someones needs rather than ours, I will tell them. Phoning Germany is never going to get infomation, simply because of the amount of people working there (2,000+ in the head office). Email works better in this regard, 99% of the time they will eventually arrive here in the UK for us to handle. I'm not surprised that many companies cannot provide technical information on products. Many companies do not manufacture the parts they are selling but outsource so often do not have information available. Add into the mix that often the point of contact is a sales person and not technical and you're never going to get the information you are looking for. Using parts in modified engines makes getting information even worse... If you (or anyone else) needs technical info on engine parts drop me PM ( I can't guarantee seeing a thread here) and if i can't help I might be able to point to someone who can. Grov.

[Nev]

Thanks for the reply Grov. Yes, I can imagine all the problems you state, it is sad that companies can not seem to do the obvious and correct things! My company is the same, just a few techincal people running the whole thing, whilst 80% of the staff haven't a fcking clue about anything and just drain the company of a fat salary for no good reason. Anyway, thanks for all your kind info, it is warmly welcomed. And BTW it's not you who is the 'saddo', it is the thick marketing people who cant understand that this important technical stuff (which is what actually makes engineering work!) needs to be available to the paying public. One day maybe we should start our own company Seriously, it's when people like you who 'branch' off, that new really successful companies take off. Eg Aerial, Race Car Component etc etc. Cheers, Nev.

Edited by Nev, 12 July 2011 - 03:51 PM.

[tont2002]

Absolutely great info and an interesting read, I'm actually a little more knowledgeable after reading this..... Cheers guys!!

[Nev]

Just for any future readers, I have been using the C20LET pistons on my Z20LEx block now for 5000+ miles running 500 BHP with no problems at all. I have great compression and there is very little blow by/crank pressure and no oil consuption either.