This is not an engine. It is a starter test bed. It has no gearbox. It only has modified cranks, a barrel, head, piston and conrod as well as reed valve to provide some representative resistance/torque to make sure the remote external starter can turn over the engine. There won’t be any cooling either.
On the left is our square engine and on the right (yup, it’s bloody huge!) is the external starter ready to crank PZ500 into life. With a compression ratio of 18:1 thanks to the methanol fuel we’ll use, the torque required to turn this engine over is in the region of 80Nm, we need a monster starter to do this job and we need to develop and test it thoroughly to make sure it can deliver the goods before letting it loose on PZ500 later this year!
Dave Cilliers asked: Wouldn’t powered rollers have been easier and cheaper?
Piet van Zyl replied: Only if you know the exact torque that you need to provide. Calculated torque is all theoretical. If we have a close representation of the real engine, then apart from the combustion that won’t be present we should be getting close to testing the real thing.
And Koos replied: On the face of it “maybe”. But you still need a starter motor and gearing and and and…. And on top of that, a MotoGP style external starter on the crank conveys so much more of a professional drool factor image, we’re going all out for it
Doug Williams asked: Is the bottom part under the barrel going to be part of the crank housing or is it just a test jig for the starter?
Koos replied: That’s the “square” motor housings that house a simplified crankshaft and port passages that allow us to get as close to dammit to the real deal when it comes to actual required compression torque, both for primary in the combustion chamber but also for what happens with ingesting and compressing air into the crank area to feed the transfer ports. Note the humungous reed valve which we need to complete the picture. The head is outstanding in this image, Jock is nearly finished designing it and will share updated images in the next days, hang in there.
Piet van Zyl replied: It gets bolted down on a table as part of a test installation.
Hamm posted a picture and said:
Suggestion: decomp valve as used on high compression Harleys
Koos replied: We have one on PZ490, this will be our absolute last resort. There is evidence on the PZ490 piston crown that funny stuff happens due to fuel-air mixture entering and exiting the channel leading to the valve. We will be pushing all credible boundaries with PZ500 and I don’t want unexplained phenomena happening in the combustion chamber.