My pistons finally arrived this week after a long time of waiting and changing minds a few times.

Mahle started up a consumer line a few years ago to offer some of their race bred design at an affordable price.

To quote the Mahle press release

Every Silvia engine has the potential to become a powerful, turbocharged road hog with a few modifications. MAHLE’s new piston assembly kit for the Nissan Silvia SR20DET engine provides 8.5:1 compression, in an all forged 4032 aluminum alloy piston kit that gets the job done with less hassle. Designed as a power generating, race ready kit, the PowerPak comes complete with 1.2mm, 1.2mm, 2.8mm steel nitrated rings, 22mm (103g) high quality steel wrist pins and round wire locks.

This high strength, low expansion 4032 aluminum alloy pistons allow for reduced piston to wall clearance giving more stability. The pistons are hand-deburred and phosphate coated reducing micro-welding and pin galling, and features a proprietary anti-friction coating GRAFAL applied to the skirts, forced pin oiling and radiused valve pockets for added performance. Currently available for an 85.5mm bore, 86mm stroke, 136mm rod with 22mm pin diameter. The SR20DET pistons weigh in at a trim 325 grams.

The Specs

Nissan Silvia SR20DET Bore: 86.5, Stroke: 86, Length: 136, Pin: 22, Comp: 31.8/1.253, Dome: -11.5cc, Weight: 325, C/R: 8.5 to 1 MAHL NIS253405I12 (SIL)

I hadn't seen anyone use these pistons yet, but I couldn't turn down the deal I got on these. For just a little extra than a set of CP pistons, I landed this set. And before you ask, I cannot get you the same deal. Sorry.

The first thing I noticed was how light the pistons were. I've held Wiseco and CP pistons before, and these are noticably lighter. The side skirts are reduced in length and you can clearly see the Grafal coating.



From what I understand, the coating is a teflon like coating, reducing friction. The coating will wear out with time. About 50,000 miles seems to be the concensus I hear on most coatings.



The crown has valve reliefs cut in it, although the piston shouldn't come that high. It should be nice insurance in the advent of a timing chain mishap reducing the chance (but not eliminating) of bending valves.



Every bit of the piston seems to be molded perfectly with no visible stress risers. Also notice the expansion groove cut between the compression rings. The stock piston lacks this:



But Wiseco used the same technique:



The phosphate coating wasn't complete, but the areas it missed were little nooks and crannies in the underside. The phosphate coating is another friction reducer.

Phosphate coating is a crystalline conversion coating that is formed on a ferrous metal substrate. The phosphating process relies on the basic pickling reaction that occurs on the metal substrate when the process solution comes in contact with the metal. This coating is employed for the purpose of pretreatment prior to painting, increasing corrosion protection, and improving friction properties of sliding components. In other instances, phophate coating is applied to threaded parts and top coated with oil to add anti-galling and rust inhibiting characteristics.

A side by side comparison with the Mahle, stock, and Wiseco pistons


The undersides


The only worry I have right now is that there is no cutout for the oil squirter. However, the cutout on both the wiseco and the stock piston both are cut way above the squirter. The piston should clear the squirter with no problems.

Unforunately, I won't be able to do installation for a while. These pistons arrived a day after I broke my arm prett badly. Until my arm heals, the rebuild project is on hold. As soon as I can, I'll have these installed and give an update on how they perform with the stock turbo and fuel management.

I've heard of some 4 cylinders gaining as much as 15 horsepower from these pistons, but that's on fully built motors. I don't have a dyno anywhere nearby to do a comparison chart, though. So it may be a mystery as to how much of a boost these pistons will be.

UPDATE:

I finally got around to downloading the pictures of my fix for the squirter clearance issue.

At first, I had suspected that the issue lied in the side skirt. It turns out that I was wrong. The Mahle pistons have the inside support going to the wrist pin shaped in a V. It shortens the wrist pin and seems to be a bit of a stronger design than the stock design, which is straight across. The angle of the support is the issue. The support barely comes into contact with the nozzle of each squirter.





The red dot is the point of contact that was breaking the squirters.

Jay and I had originally thought of grinding the pistons to gain the clearance we need. I had talked it over with the guy in charge at the Mahle piston pack division, and he confirmed I could grind out a fair amount (about .020" IIRC) without throwing the balance off. Jay ground quite a bit and we still couldn't find any clearance.

Our solution was quite simple and would have save a lot of headache and metal shavings. We cut the locator pin on each squirter in half. The missing half would allow us to swivel the squirter closer to the center where it couldn't hit anything.




I very carefully used a cutting wheel to take off the material. I practiced with the old broken squirters first before I tackled the real deal. Be very careful not to contact the squirter neck. Thankfully, since the wheel is circular, you should be able to avoid the necks.



With each squirter modified, they all swiveled to the center and clear now.

Nice Looks really good too, sorry about your arm and I can't wait to see what you have to say about these.

This is great info, I was trying to decide between the CP's and the Mahle's. I like the looks of them and you can see why they are noticeably lighter(wristpin hole has significantly less material) around that area on the outside of the piston. Just a though, perhaps the pistons were designed so short so no relief would have to be cut for the oil squiter... Thanks again for the info...

Are these the Mahle power pack pistons?

http://storesense.megawebserve...l.bok

Yarp, they are. All the online stores I see selling them just use a generic piston picture for the sales page. The SKU matches my part number. I might send them an email to verify what overbore size they are as Mahle doesn't offer a standard bore piston AFAIK. Only 86.5mm and 87mm

Those are 86.5 in the link IIRC. Trying to finalize my piston options and order up.

figure i would chime in here adding a little information i have recently run into, i have been recently begingin to assemble my engine using there 87mm pistons, i was having an issue clearing some oil squirters... i called mahle and spoke with there head engineer in charge of power paks pistons, tony ford.... very nice guy went out of his way to work with me in gettin a solution.... even though this is very uncommon on sr20's, he says my only solution would be machining a notch in the skirt, to clear the squirter, kinda a bummer but gotta do what i got to do. He did state that anywhere between 40-60 thousandths would be a safe amount to remove and still should keep the piston within balance..... gotta wait till tomorrow till i can take them to the machine shop, will try to keep everyone posted on the outcome of my present situation..... Tony did say that on the rb26's)i know this is sr forum) but that on rb26's it is very common for those running mahle pistons to have to make a notch to clear.. soo this is all i got at the moment... hope this may help anyone

That's not very encouraging. I'd like the piston to be finished by the time I get it. What reason on earth is there not to do something like that from the factory?

Mine had no issue clearing the squirters. I rotated the motor over quite a few times before I buttoned it all up to make sure that everything would clear.

Update on my pistons:

I recently had to pull the oil pan to fix a leak I was having and found the remains of 3 oil squirters. Turns out my pistons also made contact with the squirters, but the issue only happened under load. I had clearance during assembly, so this is a pretty unfortunate turn of events.

Overall, though, the pistons have performed great and I really do like them. The motor is noticably freer revving and the car has more pep at stock boost.

Also, during the initial startup, we had ran a compression test before the motor had even ran on its own and it had pulled 125 psi of compression with rings that hadn't been seated. Pretty impressive IMO.

The rings also seemed to seat in fairly quickly and the motor picked up strength within a few days of driving.

they sound like some really nice pistons. might have to pic up a set. thanks for the great info on them. seeing as i need to replace my crank im prolly doing a full rebuild.thanks

i have always like malhe, but i believe they use a high silica alloy in there newer lineup. they expand less, but are less resistant to detonation.

They are a high silica aluminum.

DAM! i hope i dont run into this problem of the piston hitting the oil squirter. i still havent fired up my engine im still waiting for my z32 maf to come in. is there any way to tell if im going to have this problem?what are you doing with your engine hijacker?

How would one remedy that issue? Sounds like they are good pistons so if it's not too difficult, I might still pick up a set.

im thinking you can add a small washer to bring that oil squiter down a little bit but but if its oil pressurized it may leak through the washer and also im not sure if the bolt that holds the squirter to be long ehough to have a good amount of thread and hold everything intact safely. if the squirter goes any lower than it is would it have a problem with it hitting the crank? i cant remember how close it was to the crank.

Bart, your running forged pistons so you really don't need the squirters. Plug em up and boost your oil pressure.

if i have the same problems i may do this. but im not sure how to boost the oil pressure up.

the converted wrote:Bart, your running forged pistons so you really don't need the squirters. Plug em up and boost your oil pressure.

I'd rather run the squirters. Call it insurance, call it prudence. The system was designed for them to be there, and I'd like to make sure that I have the head room.

Slik, the pressure would see a small increase because there's 4 less holes for the oil to flow out of.

The system was also designed with cast pistons using oil squiters to cool them. The alloy that they use doesn't expand as much and conducts heat much better so they become unnecessary. You'll also have the advantage of not having all of that oil slinging around creating extra windage losses.

I'm going to go back to my audio corner now.....

so your gonna run your oil squiters still.. **** thats a bummer now you have to pull the engine out now and start all over pretty much. or what other feasible ways can you solve this problem without having to pull your engine apart?

Even if I wanted to delete the squirters, slik, I'd have to pull the motor out of the car.

This isn't going to be that big of a deal. I'll yank the motor on Friday and pull the pistons out. Replace the squirters and get the pistons notched properly. Downtime should be minimal.

Mark, I see the point you're making and you have valid arguments. I'm also just super paranoid and would prefer to run the squirters for just in case issues. Plus it would be more work for me to delete the squirters than it would be to replace them and make the pistons clear.

i guess it wouldnt be too bad.. but darn the luck. i hope everything works out with it. im curious to see if mine have the same problem. i hope not. if so i'll be pulling my motor too. haha.. no other damage was done while the oil squirters were broken? what do you think about adding a washer to help it clear the piston? to me it doesnt seem like a good idea to do.

If you weren't putting the squirters back in I would tell you how to plug them with the engine in the car

Mahle is a very good company.

Toyota recently awarded Mahle as one of the best quality suppliers. To receive an award and be recognized by one of the "pickiest" OEM is a tremendous achievement.

Just a side note.

is there any aftermarket pistons that you havnt heared anybody have problems with like clearance issues.

CP, JE etc.etc. Pretty much any piston that has a cutout in it's skirt.

mouse6933 or hijacker can you post up pics of the pistons notched up? thanks

I won't be able to get it done till this weekend. I'll see what I can do.

Sorry to hear that happened. Yes, please post pics of the remedy.