George Bryce's World

Vacuum pumps can help you run up to a full tenth quicker. They make lots of power increases because they allow the top ring to stay sealed longer in the rev range.

Many racers think it is because of other reasons, but, truth is, all pistons and rings will lose their seal at some rpm. This is when the pressure below the ring is greater than the pressure above the ring. When you rev the engine so high that the piston stops at TDC, the ring tries to keep going, losing contact with the bottom of the top ring groove.  

So, the vac pump can pull negative pressure on the entire area under the rings. On a Suzuki GS 1150-style engine, this is a ton of area. It includes the tranny area and all space under the cylinder.

What we have found over the years is that the oil system loses PSI at the same rate as the vacuum increases. Vacuum is measured in inches of pressure and the oil system is measured in pounds per square inch. So, the vacuum pump will reduce the oil PSI a little.

 But, if you turn on the pump before start up, it can and will stop ALL oil PSI!!! So, we fire engine first, then turn on the pump. If you are racing, it will be up to full vacuum by the time you stage and you will have oil PSI.

The biggest danger when using the vac pump is starting the engine after an oil and filter change, because the entire oil PSI system is empty of oil and full of air. If you  turn on your vacuum pump before the oil PSI is primed back to normal, you will run the engine dry of lube and you will lose the crankshaft.

 If your vacuum pump pumps oil out into your overflow tank (puke tank), you have a bad leak in the system. This could be anything from a minor clutch cover gasket leak to a hole in a piston.

We run new and sealed gaskets and turn seals around backwards to maximize our vacuum advantages. The more vacuum we pull on the crankcase, the higher we can rev the engine before ring seal loss.

Please be mindful of this information and write me for answers to questions.

Have fun and go quick!

This entry was posted on Wednesday, September 7th, 2011 at 5:43 pm and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.