Thursday, May 14, 2009

Figuring Compression Ratio

Compression ratio is the volume of the cylinder when the piston is at the bottom of the cylinder compared to where it is when the piston is at TDC. A 100 cubic inch cylinder would have its volume squeezed into 10 cubic inches with a 10:1 ratio. The easiest way to keep track of it is to think of every thing as volumes that are stacked on top of one another. The factors that stack up are the displacement of the cylinder (bore and stroke), the volume of the deck clearance (getting back to the zero-deck issue from before), the volume of the gasket (which is basically a short-round cylinder), and the volume of the combustion chamber. The net combustion chamber volume means you must subtract dome volume add the dish volume. Use the formula (bore x bore x stroke x .7854 x 16.4) to get the volume for a cylinder in cc's. Stack up the cylinder + the deck volume + the gasket volume + the net chamber volume---take this number and call it A…Stack up the deck, the gasket, and the net chamber volume and call it B….. Take the big number A and divide it by the small number B and it will give you the compression ratio.

Thursday, May 7, 2009

If you’ve been keeping up with the issues concerning the Powersports industry, you are most likely familiar with the 2 largest issues- the lead law from the Consumer Products Safety Act and the bill in the U.S. House of Representatives that could potentially make 24 million acres of public lands inaccessible to off-highway vehicles. Companies and organizations across the Powersports industry have been rallying everyone to write their congressmen and respective committees in an attempt to thwart these rulings. The American Motorcycle Association (AMA) and Motorcycle Industry Council (MIC) have been instrumental in giving the industry a voice.

Consumer Products Safety Act Lead Law
On Friday, May 1, the Consumer Products Safety Commission (CPSC) issued a stay of enforcement on youth motorized recreational vehicles until May 1, 2011. The companies who brought the petition to the committee included American Suzuki, Polaris, the Specialty Vehicle Institute of America, and Yamaha USA. The stay applies to only battery terminals with up to 100% lead and components made with metal alloys- steel up to 0.35% lead content, aluminum up to 0.4% lead content, and copper up to 4.0% lean content. By November 1, 2009, the CPSC committee requires each manufacturer to have a plan in place to reduce the lead exposure from the components contained in the stay.

This decision was based on many factors presented to the CPSC. There was a fear that more youth riders would be on adult sized vehicles, increasing the risk of injury or death. Argued by the petitioners, by substituting lead in steel, aluminum, and copper alloys, the function, durability, and corrosion resistance could be compromised. This can cause increased injury due to components breaking prematurely.

Though this was a break-through for the industry, it is still technically not legal to sell youth motorcycles and ATV’s. Due to the Consumer Products Safety Improvement Act (CPSIA), state Attorney Generals can still prosecute violators, despite no fines or penalties from the CPSC. You can check out more about the ruling by going to the AMA website. The AMA has been doing an excellent job keeping everyone up-to-date on the latest developments. You can also voice you opinion from On our home page, we have a link to the MIC to send a message to your congressman to have your voice heard.

Public Land
Another huge issue for the Powersports industry is the bill currently in the U.S. House of Representatives that could potentially make 24 million acres of public land in the western United States inaccessible to off-highway vehicles. The bill was originally proposed by a representative from New York City and currently has no support in the potentially affected states. The AMA Vice President for Government Relations, Ed Moreland has submitted comments on the bill to the House of Representatives. Mr. Moreland argued all public lands are for enjoyment of all Americans. The people who enjoy these lands are not only the nimble and fit, but those with small children, the elderly, and the handicapped. Some of these individuals need the assistance and freedom of an off-highway vehicle or ATV. With no support from the potentially affected areas, should these people not have a say in the matter?

The AMA has also been doing a great job keeping everyone up to date on the developments on the public land issue. Thank you to the AMA for all their hard work!

Friday, May 1, 2009

Tech questions come up in every rebuild whether you are an experienced engine builder or completing your first rebuild. When you purchase a Wiseco product, we provide technical support on our products to assist with the questions that may come up. Our technical team- Ron, Tom, Adam, Dwayne, Vic, Brian, Chris, John, Jeff, Al, Sue, and Sean- are ready to help you out. We’ve asked our team to put together a few questions they answer on the phone frequently.

What kind of piston-to-wall clearance can I run?

The factors that affect piston-to-wall clearance are cylinder wall thickness, whether the block is filled, the overall compression height of the piston, piston material and thickness, and whether a marine engine is to see fresh-water cooling. Most small blocks get .004 piston-to-wall clearance and most big blocks get .005 due to the use of our 2618 high-strength alloy. For heavy blower and nitrous applications, Wiseco recommends adding .001 to the standard clearance. Special note: Clearance numbers are obtained from measuring the largest diameter of the piston, typically at the bottom of the skirt. All measurements should be taken 90 degrees from the pin centerline.

Motorcycle/ ATV/ PWC piston clearances are printed on the label on the front of the piston box.

When I install my Wiseco piston, which way should the arrow on top of the piston face?

On most Wiseco Powersports pistons, the arrow will point toward the exhaust. If you are installing pistons in a v-twin or automotive application, this will differ depending on the application. Checking the installation directions included with your Wiseco product will verify the direction. But, if you still need assistance, our technical sales team will be happy to help.

I have a 4-stroke ring package that I received with my piston. I have the top oil rings, but am unsure of which rings are the Top and 2nd. How can I tell?

Some Wiseco 4-stroke ring packages are interchangeable between Powersports and automotive applications. Therefore, you may have additional rings that are not required for your application. In general, the silver/ gold/ shiny ring is the Top ring, while the black ring is the 2nd. This can be verified in the ring installation instructions included with your ring pack.
Is there a technical question that you would like to see posted on our blog? Leave us a comment! We will try to answer as many questions as possible.
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