I'm trying to decide on which blower/turbo pistons to go with. And I was wondering if there's any difference between this two. I mean aren't they made by same manufactuer or not? The reason I ask is because the machine shop that's doing my block only stock SRP's. And if I don't want those they will have to special order. Thanks.....

 

They are made by the same manufacturer. According to JE: JE designs are specifically engineered for more extreme applications up to, and including, professional competition. In this environment, the higher compression ratios, higher boost or heavy nitrous usage necessitates the higher tensile strength 2618 aluminum alloy. SRP Pistons are designed for street/strip applications with compression ratios compatible with pump gas as well as moderate boost and nitrous oxide. SRP pistons are forged from 4032 low-expansion aluminum alloy for smooth and quiet operation.

So, the JE line is made from a stronger material. They also have additional CNC machining compared to the SRP line. The basic designs are the same, though the SRP line is not as extensive. Should be ~$100-150 difference in price per set. The JE line is available as a "custom" if you need an unusual compression height, etc. For most NA/low boost/small N2O, I'd say go with SRP if you are tight on $$$. JE is a better choice for high boost/big nitrous applications.

Rich

 

Thank you.. After few months of trying to find out what the difference is. Now I know...

 

Rich -

Got a question for you regarding the expansion characteristics of the two alloys you mentioned.

The "2618" alloy expands more than the "4032". OK...

If I have an engine with the 2618 pistons and another with the 4032 pistons, and I start them both at the same time, the 2618 engine should be louder (piston clatter) and have more blowby, with the "problem" going away after both engines are fully up to operating temp.
(I quotated "problem" because it's more of a natural characteristic tthan a real problem.)

My question is this:
In terms of the inevitable cooling down that you have in the staging lanes, does a driver with 2618 pistons need to worry about his pistons cooling down too much before a run, thereby contracting to it's "cold" size & shape and not maximizing the potential cylinder pressures?
Or to put it differently; if I use 2618 pistons, do I need to have "X" amount of warmup time before a run to insure that my pistons are fully expanded?

 

Good question. It is clear that you won't have as good a ring seal with a larger clearance when the piston/ring pack is <operating temp. However, the absolute magnitude of this effect is going to be small. So, in heads up racing it shouldn't be an issue unless you are after the last 0.0x second. If you race on an index, the important thing is consistency and that is largely dependent on doing the run the same way every time. A friend who is serious about index racing uses a block and an oil heater to keep his temps constant and feels this is important when extreme consistency is necessary.

Rich

 

now what about diff between JE and DIAMOND'S????
those are the two i'm debating for my future 7-800hp turbo app.

which is the better of the two?

mike

 

Rich,

Wouldn't the ring end gap specified by the manufacturer dictate the amount of blow bye, and if the same rings were used on two different sets of pistons.. wouldn't the actual amount of time either engine reached its peak sealing temperature be dictated by the thermal conductivity of the piston material to heat the rings to their operating temperature? as the rings are the primary source for pistons to dissipate heat to the cylinder walls and through the block and into the cooling system to be stabalized. just a quick engineering question.. I guess basically, rings have end gap to allow for expansion, do ring manufacturers take into consideration the different alloy pistons the rings will be used on?

thanks,
Chris

 

The degree to which the piston/ring package provides a seal will depend on the ring gap and the bore clearance at a given point in time. As the rings heat up, the gap closes and the seal improves. As the piston expands radially, the bore clearance is decreased and ring seal improves.

Hypereutectic pistons have beome popular with OEM's for a number of reasons. Among them, they expand less and can be run tighter (when cold). The advantage is less noise during warmup and lower emissions. The lower emissions are a function of better sealing until operating temperature is reached. While I don't think it's a design consideration, if you did a max power run on a dead cold motor, I would guess that you would see a slight loss of hp with the setup using pistons having a greater cold bore clearance. The magnitude would be small and it would be even smaller if the comparison were between partially vs. a fully warmed motor. That's why I tried to indicate that while there might be a difference (between the two different alloys) in the drag racing example, it would be trivial. Interesting mental exercise, but not of any practical importance.

As far as Diamond and JE, they both make a good piston. I happen to be a JE fan, but they are premium priced and Diamonds are a bit less.

Rich