Thread: Aftermarket Pistons.
08-10-2008, 11:38 AM #1
So, looking at some recent posts, and some discussion of pistons have come up. I'd like to get some type of discussion going on the differences in pistons. Who has installed them, what type, does it require race fuel, has GIO been reduced? ETC....
I know R&D sells pistons, but they require race fuel. I guess their would be no reason to change pistons if they do not yield any additional performance, but buying race fuel could get expensive. Does anyone sell pistons that are better than OEM, and not require race fuel?
08-10-2008, 12:10 PM #2
If the pistons require race fuel it is due to increased compression, which will net some noticeable power. However, for endurance racing like you do, I'd suggest keeping the compression lower,especially with the roots charger that the ultra has. If you are not already, I would be using the pulley kit and whatever intercooler mods you can do.
08-10-2008, 12:48 PM #3
I see you were paying attention! Very good.
The key to proper piston performance is all predicated upon what exactly you're trying to get the engine to do that it wasn't previously.
Now, it's totally understandable to want to keep the stock pistons in a "power adder" combination (turbo, nitrous, supercharger), as the added compression caused by an aftermarket piston would exacerbate the wear and tear on the engine's reciprocating assembly. (That is why many supercharged automobiles run a miserly 8.5:1 or 8.25:1 compression ratio.)
The features that I was looking forward to in an aftermarket piston were not to wholly "up" the compression ratio (as I was only looking for say a quarter or half of a point, that to keep the otherwise stock internals), but to A) design a piston to incorporate an additional "scraper" ring (to halt the excessive blow-back) and for exceptional weight savings.
As you well know, in any performance engine application, the lighter weight the reciprocating assembly is, the less tax there is on the engine itself, thus allowing for freer rpms. In this case, I was also exploring the idea of shot peened H-beam connecting rods for even more weight savings. While it wouldn't "stroke" the engine (as cubic inches) or up the compression much, it would "free up" some horsepower and loosen the torque curve.
As per the other posts, I'd love to know the exact data on R&D's aftermarket pistons as well as those of Skips. They could be the difference of mechanical life and death.
08-10-2008, 12:56 PM #4
Are the JE pistons standard bore?
Can these 1.5's be overbored?
08-10-2008, 02:08 PM #5
Kevin, I'm assuming the boat has been ridden since you installed the new pistons. How does it feel now with the new pistons? Much of a difference? Are you willing to share the exact pistons you installed, for those of us to do some research on them? So, your using pump gas still?
STANG...I have "thought" of getting the pulley kit, but am still undecided on it. I'm not sure how many people are running it WOT for periods of an hour. I need reliability, and top speed.
08-10-2008, 04:30 PM #6
Now, Skip posted a picture of a pair of custom JE pistons that he ordered which piqued my interests. It's Skip that you should ask how his craft runs with them in it, not me.
08-10-2008, 08:42 PM #7
Only because you asked Kevin,
JE made a special order set that I purchased, in line with what Macc Racing was doing.
Then I ordered the new production line ones that are designed to be used on the JT1500 motor. Notice how the new ones have an actual part number.
Ive been sitting on these for some time now.
Here are some simple specs.
They fit right into the 1500 cylinder. No bore required, now you can punch out to a 1.6 but will require head work and will not be good for anything other then CC racing as the over heat from thin jug walls.
Also these 9.5 piston work well in endurance racing as that is exactly what Craig Warner was running in the LB/Cat race.
What is being done in this package is trying to get the compression up without over turning the SC. On this motor the SC will have issues with extended use at anything over 8K. So running the stock pulley actually turns the SC at a lower RPM then the motor. I still stand behind my peak effiency of the SC is in the range of 7600RPM to 7800RPMS. After that I have always seen dropping in boost. Weather its the engine sucking the charger dry or the charger can push more over it. Thus the reason we dont see huge speed gains with pulley kits.
Sooo as I understand it, running higher compression is a better and more reliable way to run higher boost inside the jug. So run the stock charger at stock RPM's and get the boost through the pistons.
You will also see that the JE have addressed the GIO issue carefully by choosing and testing better rings and has a compression groove to vapor lock blow by. I could be all wrong here so dont jump my shit over it. Just tell me facts that make my findings wrong and Ill listen...
08-10-2008, 08:51 PM #8
dont want to go off topic......
has anyone used the JE 9.5's on a n/a 1.5L with nitrous ??
08-10-2008, 08:55 PM #9
Why would you do that. Stock 15F piston are already higher compresion then the 250 are.
Though I do have a idea. Why not put LX pistons and Cams in a 250.....
08-10-2008, 09:10 PM #10
i always thought of that skip i heard macc was doing a set up like that
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