Aftermarket piston quality / Torque plate measurements

[S54B32]

I don’t know how to name this topic correctly, but tried to put everything in the title as I didn’t want to open separate topics.


Aftermarket piston quality


Long story, currently building my engine because previous owner made huge mistakes during engine assembly and after seen evidence of this, I decided to rebuild it completely (which was the right decision). Found during disassembling 2 cracked oil separation rings, that made deep scars in the cylinder walls and a very very worn and stucked oil regulation piston. That by very high chance was the reason the engine had a spun bearing by previous owner (reason he „rebuilded“ it with new rings, rods, crank etc).
Because „while I’m there“ I also decided to make bottom end forged. (Charged with a v3si).

In the past I only worked with oem pistons and not aftermarket. So after ready and speaking to some people I bought Wiseco pistons (87.25) because they were relative fast available and heard nothing bad about these. They where here rough in the same price range like Mahle Motorsport and JE-Pistons.

But the quality of what arrived is not what I expected! Is this normal for aftermarket pistons to have have oil holes clogged with metal chips and not deburred inside with metal flakes hanging around? This is not what you want to find inside your engine or elsewhere! (Next oilpump would be gone, oem pierburg is around 420€!)

I contacted Wiseco about this „quality issue“ but not received any kind of answer. What a shame. If I had the time to wait for another piston set from (definitely) a different manufacturer, they would gone directly back to the supplier! I can highly suggest to triple check your aftermarket pistons.


Anyone here that made similar experience with aftermarket pistons?
Maybe also Wiseco or other brand?

just a few pictures, they all looked the same.


Torque plate measurements


Also i made the decision to machining the block with a torque plate. Here in Germany this is not very common for iron blocks and most machine shops said it‘s not necessary, but did it anyway. Had a individual plate made in a CNC in full cylinder head thickness. After receive the block back from machining, I measures unroundness and found it quite much. Even the machine shop was very surprised that a iron block deforms that much during torquing!

Later I will use ARP head studs (they where installed during hone) but I also measured with oem head studs and found not much difference (within measuring tolerance).

I measured on 4 positions and 3 different depths, 0°,45°,90°,135° (90° is in line with crankshaft). After around 60mm the unroundness without untorqued head disappears.


I had biggest unroundness on 45° and 135° measurements. These represent the direct line between the headstuds. The minimum was 1.5 and maximum was 4. (in 1/100mm)

After torque the torque plate, I had the roundness of all cylinders perfect within the measuring tolerance of the gauge (5/1000mm)

As the head, block, measuring instruments all where cold the and the same temperature, I would assume the unroundness would even get more when the head expands more than the block and the studs will pull with even more force. So I think I would have definitely over 5/100(0.05mm) with hot head.

After gapping the first 3 rings I came to the idea to torque the plate again to see how the ring gap will look (most people told me, the torque plate will not significant change the gap). But it does! Had to reorder all of the 3 first rings, because I set the gap without torque plate to 0.50 on spot and after torquing the plate I can even fit a 0.65 feeler gauge quite easy in.




Anyone here who had also measured the block with and without torque plate? I would be happy if someone could share their experience!

[enjoy_m3]

I can't give much input on the torque plate. But I also rebuilt my s54 myself. The machine shop checked both roundness and piston to wall clearance and confirmed that a clean and hone was only necessary.

About the pistons. A good friend mine who used to own a shop and retired had built many performance engines advised against wiseco pistons. He mentioned issues you mentioned. And he also had to re do customers engines that were built by someone else using wiseco pistons. The issue being loud piston slap during cold start up on a turbo engine. He said wiseco pistons used to be great but also mentioned the decline of quality through the years, unfortunately.

With his experience I ended up using JE pistons and can confirm the quality of all the pistons were much better compared to you're pictures. I decided to go with JE at the time because I was able to get a slight discount. The mahle pistons were a bit more at the time. It probably isn't a huge issue on a relatively mild engine build but JE and Mahle 'off the shelf' pistons are made from different material. Typical JE pistons are 2618 and mahle Powerpack are 4032. Both companies can make the piston at either material at your request. I'm not sure if they charge more. It is preferred to have the 4032 aluminum for tighter piston to wall clearance, typical for a natural aspirated engine. 2618 is recommended for turbo or supercharged engines.


I did run into an excessive oil consumption issue which I assume and hope is an assembly issue. I pulled the engine out and will be taking it apart to inspect when I have time. You make an interesting observation with the ring gap with the torque plate. I gapped my rings without one and wonder if it lead to the issue.

Hope this helps

[Obioban]

That's pretty unacceptable.

[Altaran]

I also upgraded to forged pistons and rods for my rebuild, my choice was CP for both. I inspected the parts upon arrival and they we're flawless.

Since my motor ist now extensively modified, I had a well known engine builder Here in Germany so the mechanical work and reassembly. They confimed that the parts are flawless.

I went for CP as most builders I talked to confirmed them to be the preferred manufacturer and also because their parts are lighter than others.

They are I little bit more expensive that the cheapest alternatives, but I don't want to have to reopen the motor sooner just because I saved a few bucks on parts...


But yeah, what you received from Wiseco is unacceptable.

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[digger]

Yes torque plate is valuable on big bore close bore spacings especially the way bmw incorporate the boss. It’s also a reason not for Uber high preload ARP studs if not absolutely necessary including if retorquing is not practical. If you look at any small six block you can see the uneven wear around the circumference.

Those numbers seem much larger than what I’ve heard but not seen s54 specific data. one tip with you measurements pick a set of units and write decimal e.g 0.02mm or 0.001” or whatever none of this fraction stuff it’s much easier to read. I’m a bit skeptical of your measurements accuracy as roundness should be better than 0.0005” but without very high end tools easy for that to be in the noise.

Also did the diameter close up or get larger ?

that piston quality is poor they didn’t even deburr

[zzyzx85]

Wow, that wiseco piston is hard to look at. That's just shoddy.

I went with a CP pistons on my STI. They were beautiful out of the box. I felt bad for coating them up and putting them into my short block lol.

[robgill]

+1 for JE Pistons, have used them in two motors with no issues. I also used a torque plate for both builds.

[JakeM346]

My recommendation for pistons is mahle motorsport. You can get them in the alloy that is used for the oem bmw pistons and also mahle is the producer of those too. But unluckily due to some clause with bmw they are unable to sell you the oem pistons but the Motorsport pistons are the perfect alternative as they are cheaper but actually more expensive in the production than the oem bmw pistons (due to the bmw markup). The quality control with the mahle Motorsport is superb. Also you can get them in the stock compression ratio.