Tuesday, August 4, 2009

Where is the horsepower? We have it here at Wiseco if you need it.

So, do you really know about horsepower? Luckily, the engineering team at Wiseco is well versed in horsepower. In fact, it's probably up toward the top of their lists of favorite things. We have a FAQ section on Wiseco.com in our customer service section. Here is a question regarding horsepower. It leans toward the automotive side, but has some good general info as well.

What are the other factors to consider when maximum horsepower is the goal?

Compression ratio and Dome/Dish volume determine combustion efficiency and resistance to detonation. Detonation can and will destroy any piston in short order. Lean conditions will melt any piston as any aluminum alloy melts within a few degrees of each other. Most of a piston's heat is dissipated through its contact with the cylinder wall and oil splash. Very short pistons and excessive clearance will melt a piston sooner. Static compression varies more than most people would believe. A piston running .020 down in the cylinder at tdc as opposed to "zero-deck" on a 64cc combustion chamber headed 350 Chevy changes the compression ratio from 10.25:1 TO 9.8:1.

People running compression ratios higher than 14:1 are not making more power if it means an increase in dome rise. More dome rise only hurts combustion efficiency which will loose more power than is gained by increasing compression. The current trend in Pro Stock, Winston cup, and others with big-budgets for engine development is to make the combustion chamber smaller and go to 12, 14, or 18 degree heads to make that happen. They are going for the shortest dome rise that gives them the compression they are looking for. The trend is to also use a bigger bore with a shorter stroke to put an engine at its best power potential for a given cubic-inch limit. One point to remember is a pro engine builder will never trade ring-seal for cubic inches from making a cylinder wall too thin.

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