ESP was the first to offer the “High Rev Piston” to be sold to the market, and now they have been improved. The original High Rev Piston, (which will still be a offered duration increase), was a slight improvement over the stock piston, and works well for a “edge” in performance over the stock piston, as it offered a little bit more intake and exhaust port open duration. The original piston probably worked best for the racers who already have a high revving engine, like in competitive boat racing, if they wanted a edge over their close competition. For high rpm racing with engines that are already ported for max power at high RPM’s, this new piston may add too much duration for your engine, but for the cost, it would be worth a shot.
The improvements of the NEW ESP “High Rev Piston” are as follows;
1) The duration cut on the top of the piston now takes off less crown material to help maintain needed compression. But also take into consideration that the actual compression starts when the ring meets the roof of the exhaust port on the piston’s up-stroke, so equal duration gains made by porting, (raising the port roof) will actually lower the “effective compression ratio”, (measured by the volume of the cylinder above the exhaust port, and not the entire stroke), where the High Rev Piston will not.
2) The duration increases of both the exhaust port and intake port now offer 57% more duration increase than the original ESP High Rev Piston, which should work better for stock engines and most ported engines on the market today.
3) The New High Rev Piston has also been made lighter, reducing mass of the piston which needs less energy to change direction. At 18,000 rpm’s, the piston is changing direction 300 times per second, so the energy saved goes directly to the crank shaft. The cuts on the inside of the piston are smooth, with a nice smooth fillet radius in every corner of the cut, (no “stress risers“), to help insure the piston stays strong enough not to break.
4) Along with the lightened piston cuts in the inside of the piston, the sides of the piston around the wrist pin have been raised to help increase fuel transfer port flow near the bottom of the stroke.
The quality is typical ESP top quality, which is almost impossible to beat as with all ESP engine work, (even by the Zenoah factory). This improved piston should out perform many of the ported engines sold to the public by ESP competition in your stock engine, and greatly improve your ported engines high rpm performance with most ported engines offered. Note, your exhaust pipe is a key factor for higher rpm performance. If your pipe is not tuned for high rpm, (like the QD hot pipe is, and is actually adjustable), you probably won’t see the performance gains this piston is capable of. ESP has not tested every pipe on the market, but a good rule of thumb is, if your pipe lets your stock engine rev past 18,000 rpm, it is probably a pipe that is tuned for higher rpm and should work well with this piston.
For an extra charge, ($25.00 more due to the one piece order, less charge if you order more, even of different duration specs) ESP can also cut you a special piston for just about any duration you want/need, by special order only through DDM. That is great news for the racers, (like many boat racers), who know exactly how much duration they want/need for racing and experimentation. Experimenting for the best porting specs has never been easier and less expensive for the guys and gals who like to fine tune their racing models. No need for a cylinder swap and down time for new porting specs, because a piston can be changed in the field in about 20 minutes.
A phone call is the best way to reach me by far if you have any questions.
Thanks for using/considering my stuff. I appreciate it, and I think you will also.
Doug @ ESP (616) 458-8103 (EST Zone)