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Roy,Nice work! I have a question. In your experience would it be accurate, for the purposes of comparing two units, to measure pressure differential between the incoming and outgoing flow of air being drawn through the throttle body? As long as the conditions were similar and done back to back the absolute number wouldn't matter, would it?Ok, that was two questions. Thanks, Hunter
Kind of like using an orifice plate with a U tube manometer to measure. I think you could make that work. how would you draw the air through perhaps a small computer fan or a vacuum cleaner.the problem with orifice plates is you have to be so careful with the tapping points as its easy to create a pressure difference due to turbulence around an obstruction.The reason I favour water is everyone has it available, its easy to measure and the conditions are easy to reproduce, the same differential pressure should give the same flow. Water too is fairly stable unlike air that changes in density with temperature.
What exactly does the "sacred screw" control? the throttle blade stop? the relationship between the throttle body blades? is it on both TB's? does the Centiuro and V11 have them?Ciao
Roy,I see your point about the water.I was thinking about maybe a 2 foot straight tube roughly the size of the TB on either side and using a pressure differential gauge to compare the inlet and outlet with, as you mentioned, a fan or a vacuum to move the air. I already have a differential gauge that I use to balance carbs etc. If a ever get my hands on an extra TB assy I think I'll try it.You have inspired me!Hunter
Roy: what a fascinating post. Thanks for sharing. What is the purpose of the two clear hoses that come down from the top of the black tube?
Phil, I think its only the CARC bikes that have the Sacred Screw, yes its the throttle stop on the Left Hand body, unlike the VII it must not be touched the right hand body is set by a bell crank to balance. The idle speed is set by a stepper motor valve that feeds air in downstream of the butterfly's. I think the practice has been to replace both bodies if they have been messed with.Apparently the screw is set on a flow bench at the factory. Pete Roper gave us the goods on them a couple of years back.If someone messes with the screw the stepper motor counters and you end up getting the mixture all messed up and get a burst from Pete that will make you shrivel in your boots.CheersRoy
... Conclusion: I think I can say with confidence that if I were to get another throttle body I could set it to better than 5% Another person could reproduce my rig and get similar results, there is really only 1 critical dimension and even thats not so important.
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Sounds too complicated for me Huzo, go for it lol
Sounds too complicated for me Huzo, go for it lolOnce you have the numbers from my water test you don't need to have 2 sets, all you have to do is reset your tampered sacred screw to reproduce my results. All you need is a water column 500 mm tall and a measuring beaker of some sort.A lab technician has offered to review the data and tell us how to achieve better results.
In a nutshell, thats it.Start by giving them both a good scrub.Establish the unmolested throttle bodies flow time (Time for a fixed volume to pass) if worn do several sets of flow readings, I have done this part for the Griso 1100Substitute the molested throttle body and re-produce the same time per volume.Note: Both Unmolested and Molested must have the Air Bleed fully closed, only the flow past the butterfly is to be read.Although it would be best to measure both throttle bodies on the same rig provided the rig is similar it should be possible to reproduce the time to flow at a different location, it would be interesting to know what Moto thinks of the error possibilities. I chose 500mm WC as the pressure (500mm between throttle shaft and overflow)I don't believe the cross sectional area of the water column has any effect but 1-1/2 ABS pipe is probably universal.It would be interesting to know the air flow specs for the different models, I'm sure there is a way of relating one to another.
Empiricaaly, that really is it isn’t it Roy ?
Sorry, your words are too big for my old brain to process lol