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webra speed 91

Old 12-12-2015, 10:24 PM
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Default webra speed 91

hi got a webra speed 91 with a davis convertion got of ebay , the engine runs well replaced the dynamix carb with an irvine because there was no suction as the dynamix has no venturi, but it lacks alot in the power department idle and pickup are good even starting is inpresseve.

hear are some figures

16x6 7400
15.5x12 5700
18x6 5400, without muffler 5800


any one has any experience with this engine?
Old 12-13-2015, 02:45 PM
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Sorry, no experience with this engine, but consider: - the Webra Speed engines were designed for high RPM power in glow operation..

Props which allow them to run higher RPM may still be useful for your needs, and suit the engine better as well.

I hope others chime in, I'd also like to hear....
Old 12-13-2015, 03:10 PM
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I have this ancient Webra .91 ABN, it turns a Graupner 15x8 at about 8,300.
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Old 12-13-2015, 04:54 PM
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Dieselised Webra Speed .61 with U/C / F/F venturi.

15 x 8 Dynathrust prop fitted.

Experiments will continue with an R/C carb; probably a British Irvine metal body Jetstream 7 mm bore.

https://www.youtube.com/watch?v=MUkdOWF5hFI

https://www.youtube.com/watch?v=0v3aLG2vSCM

Last edited by fiery; 12-13-2015 at 04:58 PM.
Old 12-13-2015, 10:34 PM
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well thats over a thousand over mine and 50% more power i am using an asp 90 muffler
Old 12-14-2015, 04:53 AM
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The muffler shown is an MVVS .91 box muffler.
Old 12-16-2015, 10:27 AM
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im goning to try a 108 mufler
Old 12-17-2015, 05:24 AM
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I elongated the holes in this SuperTigre 75/90 smoke stack, so it is dedicated to the Ringed .91.
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Old 12-17-2015, 05:34 AM
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LD, the DynaMix does have a venturi, anytime you reduce the diameter of a tube where a fluid flows you create a low pressure area. The air , (in this case) accelerates to get through the restriction and creates a low pressure area responding to a law of physics, (where velocity is highest, pressure is lowest.) Think of the DyanaMix carb as having a variable venturi. The DynaMix is a great carb. It has an extra adjustment which is an insurmountable obstacle to some.
Old 12-18-2015, 09:31 PM
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once running i had no problems with the dynamix exept the lack of power and when putting it vertical, but the instructions of the dynamix specify that it needs pressure feed to draw fuel,
More over looking at photos i am seeing that the dynamix i have is much smaller than the ones i am seeing in the photos , the neck of the carb fits a 40 motor and to fit the 91 some one made an adapter, it is very well made it looks like a factory jobbut it is half the size of other 90 carbs i have
Old 12-18-2015, 09:33 PM
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to day at the field ill try a irvine 60 carb and an os90
Old 12-19-2015, 04:48 AM
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LD, I'll get some numbers for you on the ID and neck. I know that Webra says they require a pump, Dar Zeelon used to kick my butt over that but I never used a pump.

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