After reading about 4 different forums and a lot of arguing and insults I still can't seem to find a definite answer or proof. Everyone seems to agree they were made by Mahle, but even the vendors seemed to argue on weather or not they were forged or cast.

I want to go with forged internals on my rebuild for sustained RPM but I'm also in no hurry to redo rings at 100,000 due to alloy expansion on the aftermarket pistons. The stocks, if forged seem to be the best medium due to the tolerances and the fact that they are also coated, does that sound about right and make sense? I'm no expert engine builder but from what I have read over the last month forged, coated and tight tolerances seems to be the best solution for my needs.

I'm hoping not to cause any grief here.....just want to know and not sure of who to call.

 

What makes you think the rings will wear out faster with aftermarket forged pistons vs. the stock forged pistons? If anything, I would think that the newer aftermarket alloys would be much better that the stuff MINI was using back in the early/mid 2000's......

Is this for a race car? Daily driver?

 

This is only from a lot of reading on a lot of Mini forums. I have read the aftermarket piston alloy materials tend to contract and expand much more than the stock pistons between cold engine startup to warm. This is not a problem for race engines as they are built with the knowledge that they will need to be rebuilt more frequently.

The stock piston is built with a much tighter tolerance within the cylinder walls and avoids any piston slap against the cylinder walls during cold startup reducing wear on the rings. The stock pistons are also already coated, where as aftermarket pistons must be coated at an additional charge of around $200.00.

I'm just trying to gather some knowledge before I purchase my pistons, If I'm wrong or mis-informed I apologize. Also feel free to correct me if I have mis-understood what I have read.

This will be for my daily driver, but I have been know to do 4-6 track days a year in the past. So not quite a race engine, but needs to be a little stronger than stock as far as the RPM's are concerned.

 

From what your saying about your use, it really won't matter which of the Pistons you use, what will matter is how you drive the car, if your going to hop in and pull away without any warm up time, go back to the OEM versions of the Mahle's, if your willing to give the car a little extra warm up time to give the Pistons a chance to expand before hard driving, then aftermarket are just fine. Either will do what your planning on.

Honestly, unless your planning on making big power, just stick with the OEM spec Mahle's and OEM spec clearances, "All" the clearances are what really brings down the longevity, not just Piston and Ring clearances, remember a loosely clearance motor is for power more than anything, if your not striving for every last once of power, then don't get too caught up in the idea of building a "loose" motor.

I'd concentrate more on rods and balancing more than anything else, a good I-Beam rod (Mini' s weak point when it comes to big hp) and well balanced Crank will be more than enough of the "extra's" when it comes to a rebuild for your purposes, and cover you if you do decide to try and make more power as well. (Unless you're the type that will end up going nutz after you get started)

 

Thank you for providing another view for me to consider. If it's just warmup time I might actually go with CP pistons, the $650 price tag is not too bad.

I have no plans to go after big HP, maybe in a couple of years I'll get up to around 200-210. So the balancing and a tight tolerances sound like the way to go. I already have the rods, I went with K1 billet H-beams that I couldn't pass up for the price. The block, crank and pistons are at the machine shop now. As soon as they finish measuring everything I can decide on CP's or stick with the stock pistons.

Thanks for the insight!