2618 vs. 4032 pistons alloys for a real street car

[QuadCam]

I would like to hear others thoughts on these 2 alloys.

Most aftermarket pistons use the 2618 alloy (low silicone alloy <1%). this alloy has a higher overall strength and can untimately take a bit more abuse, but you have to run higher piston-to-wall clearances...usually .003" to .004" and will likely have more cylinder wall wear.

the 4032 allow has a higher silcone content which allows for less piston expansion...hence you can run tighter wall clearances. more like .002 - .0025." My understanding is that this alloy also has greater "durability" than the 2618 alloy.

So, for a true "street" forced induction car (driven 15,000 miles year) producing 100-125 HP (flywheel) per cylinder and runnign pump gas, which allow would you choose? and why? This is assuming a good piston design, of course.

[ReV2Red]

Also remember that you get with larger cylinder wall clearances you get more noise. Although once warmed up this would be negligible. I would personally run the 4032 alloy. If your going for about 600 hp i think that's all you would need.

Who uses the 4032 alloy?

[QuadCam]

Originally Posted by ReV2Red

Also remember that you get with larger cylinder wall clearances you get more noise. Although once warmed up this would be negligible. I would personally run the 4032 alloy. If your going for about 600 hp i think that's all you would need.

Who uses the 4032 alloy?

most companies offer either alloy. as far as shelf-stock forgings for the VQ, Mahle has 4032s. I'm not sure if JE does? JE' SRP line is all 4032 (i think), but I don't know if they have a VQ piston.

[Sharif@Forged]

Originally Posted by QuadCam

most companies offer either alloy. as far as shelf-stock forgings for the VQ, Mahle has 4032s. I'm not sure if JE does? JE' SRP line is all 4032 (i think), but I don't know if they have a VQ piston.

A well constructed and designed 4032 alloy piston should be OK on a street car. Having put about 25K miles on my old engine with 2618 pistons, I dont see much of a long term compromise in using the stronger alloy. Pistons, rings, and cylinder walls all looked terrific. It's personal choice, mainly, IMHO. FWIW, we only use 2618 alloys in our engines. Just a little extra insurance against some nasty abuse or surprises.

[Zivman]

Originally Posted by QuadCam

I would like to hear others thoughts on these 2 alloys.

Most aftermarket pistons use the 2618 alloy (low silicone alloy <1%). this alloy has a higher overall strength and can untimately take a bit more abuse, but you have to run higher piston-to-wall clearances...usually .003" to .004" and will likely have more cylinder wall wear.

Generally, with a 2618 alloy, you will be running a minimum of 4thousanth clearance. 4 thou is what comes with the spec sheet on the GTM spec ED arias pistons. On my current build, I ran 4.5 thou and could have gone as high as 5.5 though (some even say upwords of 6 is acceptable if you are running high boost). I can tell you that my motor is very quiet at the piston to wall clearance I am running. Also the ED pistons have a much longer skirt which equates to less rock than say the standar arias pistons (which I previously had)

the 4032 allow has a higher silcone content which allows for less piston expansion...hence you can run tighter wall clearances. more like .002 - .0025." My understanding is that this alloy also has greater "durability" than the 2618 alloy.

Even with the 4032, your clearances will be more than .002 - .0025. The standard forged arias pistons come with a recommendation of .003 and generally I would add at least a half a thou to a full thousandth on top of that; again, you could go upwords of 5.5-6. I was running .004 on my previous motor with the standard forged arias (4032) and there was noticable slap with those pistons, but I chalk that up to the very short skirts on the arias

So, for a true "street" forced induction car (driven 15,000 miles year) producing 100-125 HP (flywheel) per cylinder and runnign pump gas, which allow would you choose? and why? This is assuming a good piston design, of course.

Based on the experience I have had, I would go with the ED pistons (the 2618 alloy) and run somewhere from .0045-.0055 depending on the boost levels. I broke my 4032 alloy arias piston ring from overboosting. Other than that, the motor looked very good. The cylinder walls had visable cross hatches from the hone. this was after about 10K miles on the motor.

If you are planning 100 hp per cylinder or more, go with the ED pistons due to their vastly superior ringlands. They will handle the boost much better. Just make sure you run at the very least .004 clearance, if not more

[QuadCam]

I am not doubting the strength of the "ED" pistons. I am aware that Forged, GTM, Performance Factory, and Z1Performance all have "extreme" pistons on the market. No doubt that all of those models have design features that can survive over a 1000hp in one of the these motors.

I am thinking more along the lines of the garden variety forged pistons from CP, Wiseco, JE, Mahle, etc. none of them have the oil ring moved down into the pin area; I like keeping the oil ring above the pin on a street motor. I also like the idea of using thinner rings, like these pistons have. (less friction, better cylinder conformity, etc).

Basically, do the advantages of the 4032 alloy outweigh the gain in strength of the 2618 in a purely street (ie.......putting around town, hitting the freeways for 200 mile roadtrips, boosting when possible) application? Does anyone have experience with 4032 vs. 2816 pistons in other engines? import or domestic.

[djtimodj]

Bump back from the dead! This is a question i am looking in to aswell!

[IslandZavage]

hopefully Terry will chime in.. Im sure he knows exactly what ur looking for.. Every time he posts i get smarter..lol..

[GenPac]

4032 has roughly 10-11% Silicone which makes the piston harder and heat expands less than 2618 which is only about 2% content. This makes the piston more malleable and causes them to deform rather than shatter under extreme pressures.

The 4032 allows for tighter piston to wall clearance (less heat expansion) which results in generally longer life and quieter operation.

If the engine is going to be boosted hard and frequently, I would side more with the 2618.

I realize I don't contribute much to FI forum, but I have come across this question when deciding pistons for my domestic project car. /hides

[ttg35fort]

^^^^

+1000

LOL IslandZavage

As others have said, 2618 aluminum is stronger than 4032 aluminum (about 16-17% greater tensile strength and about 12% greater fatique endurance), while having a greater coefficient of thermal expansion (about 14%). The 2618 aluminum is also about 3% heavier.

When a crack forms in the 4032 material, it will generally lead to catastrophic failure. With the 2618 material, there is less chance of this happening. A crack will usually stop when it gets to an area of low stress.

The 2618 pistons will require greater piston-to-cylinder wall clearance than 4032 pistons, and will be a little noisy and there will be a bit of piston slapping until they heat up. Also, with the 2618 aluminum, there will be more oil consumption and blow-by on cold starts. Finally, the lower expansion of the 4032 aluminum means it should have better wear characteristics.

If you are taking a build to the extreme, the 2618 is probably a better choice. For example, I would use the 2618 pistons in the monster 1200 hp builds. Also, the 2618 makes sense for a builder to use because they never know what kind of abuse the customer will throw at the pistons, especially someone playing around with their own tune. For street cars, the 2618 pistons are fine if you don't mind the downsides, but they likely will wear faster. The 4032 pistons also are fine for street use. They will take longer to wear, they will be quieter, there will be less blowby when the motor is cold, etc. Very few people will ever push their builds to the point of needing something stronger.

EDIT: I know my new pistons are 2618, but I wasn't sure about my old setup. So I called Wiseco, and the Engineer I spoke with told me that they exclusively use the 2618 aluminum for the VQ pistons. So, if you want 4032 pistons, they won't be Wisecos.

[ReV2Red]

When you say they will wear faster, what exactly do you mean? Are you talking about piston rings, or the piston itself? Or do you mean the cylinder wall.
Also, how long are we looking at hear, 40000, 50000 miles?

[ttg35fort]

Originally Posted by ReV2Red

When you say they will wear faster, what exactly do you mean? Are you talking about piston rings, or the piston itself? Or do you mean the cylinder wall.
Also, how long are we looking at hear, 40000, 50000 miles?

It entirely depends on how hard the pistons are pushed. The 2816 aluminum is more malleable than the 4032, meaning the piston itself will lose it's shape faster. But that is totally dependent on how hard the pistons are pushed. I have not searched for data pertaining to what conditions cause the metal to deform faster, but I will share my opinion as to the use of the pistons in general...

Based on feedback in this forum, the 2618 alloy seems to be holding up to 1200+ builds. Back that down 16%, and that is equivalent to pushing 4062 pistons over 1000 hp. Now, I do not know how long the 2618 pistons will hold up to 1200 hp, but the 4032 pistons should hold up just as long as those pistons when the 4032 pistons are pushed to about 1000 hp, assuming no cracks are appearing. As I noted, the 2618 pistons are more tollerent of cracks than the 4032 pistons. I just don't know if the 2618 pistons are even seeing any cracks. Hopefully, some of the high hp guys will chime in on whether they see cracks in their pistons.

I happen to like Wiseco pistons, and they are made with 2618 material, but it may be overkill for someone with a moderate build. Perhaps 4032 pistons are a better choice for people who are not pushing their motors to the extreme and who want a better all around daily driver. If I were to build a motor for daily driving with less than about 650 whp, I would certainly consider 4032 pistons (assuming the manufacturer could hold the same tolerances that Wiseco does).

[GenPac]

Part of the key, you mentioned earlier ttg35fort... was the 2816 being a little more forgiving, deforming under extreme pressure vs. potential crack to shatter with the 4032. Now whether you would push your setup to such extremes (or, what extremes are necessary for the catastrophic failure) is anyone's guess.

[ReV2Red]

Ah right i see. Were talking about the big boys running the serious shizzle. Anyone only looking for 400-450 at the wheels should be better off with the 4032 then, for longevity.

[ttg35fort]

Originally Posted by GenPac

Part of the key, you mentioned earlier ttg35fort... was the 2816 being a little more forgiving, deforming under extreme pressure vs. potential crack to shatter with the 4032. Now whether you would push your setup to such extremes (or, what extremes are necessary for the catastrophic failure) is anyone's guess.

Originally Posted by ReV2Red

Ah right i see. Were talking about the big boys running the serious shizzle. Anyone only looking for 400-450 at the wheels should be better off with the 4032 then, for longevity.