I have recently been testing out a prototype of the soon to be released Webra 91 AAR engine, I have actually had the engine for a few weeks but had not had time to fit it in to a model and get the model in to a  flyable condition.  I used my oldest Millennium which was fitted with a boom off the Futura 1.8m, long 80cm blades and the OS 91 SXH so I had to make up a new shorter boom, re-gear it to 8 to 1 (15 tooth pinion gear) and sort out a few other little minor things with the model.

The engine dropped straight in with no real work to fit it, I used a Hatori #700 pipe as I had a feeling that the length would have to be a bit more than the #650 so I would have needed to have used a very long silicon joiner to lengthen the #650 enough.

So far I only have eight flights on the model but already the engine is looking very promising, it seems quite smooth with no rich mid range noticeable, there doesn't seem to be any real fuel foaming although the tank on this particular model is a little opaque so this it hard to see things that clearly, certainly if there is any foaming it is minor and not the big head of foam which might indicate things are not happy.

Currently the head speed is 1650 rpm which gives 13200 rpm on the engine, I would like to increase the head speed slightly and if anything drop the engine revs so I will try a 16 tooth pinion when we get them back in stock shortly.  Although the engine is far from run in yet I have given it a little testing and I can't actually load it up at all, I don't know the exact pitch range I am running but it is more than the 75 will cope with, I am maxed out on the radio and would have to fit a bigger servo arm to get more, I think the pitch is about + & - 9 degrees, this is with 71cm Razor's.

Fully pitch climbing metronomes just see the model disappearing upwards with out a change in engine note!  So far I am really impressed with the engine and if it pans out as good as it seems then all my Models are going to have to have this engine when it is available or when I can talk some more out of Webra.

Webra claim the engine has 3.5 HP and I believe them, it must already have 30% more power and torque than the 75 and the 75 has more torque than most other engines, I do actually wonder if some models with less durable drive trains will be able to cope with the power of this engine!

I will see how the tail is when I raise the head speed to 1700 rpm but I suspect I will have to speed the tail up a little as with so much torque I am now having tail stalling problems, this should not be a problem as Robbe do make a couple of faster tail gear sets.  More info will follow in a week or so when I get a 16 tooth pinion to try.

I finally got around to putting my Webra 91 back in a model, the first model it was in meet with a unfortunate end after the flybar snapped in flight, this ripped all the links off the head and caused a big in flight boom strike which effectively destroyed the model.  I don't think this had anything to do with the 91 engine but was just down to long term fatigue as the model was old and had a lot of hours since having any work done on it.

Anyway with the Autumn Charmouth Fly-In just around the corner I thought I had better find the time to actually slap it in a model, as always things got in the way and I just got it finished in time with just time for one quick flight in the late evening before driving down to Charmouth.

I finished setting it up at Charmouth on the Saturday (mixture, pipe length and throttle curve) and I must admit I have been getting a real kick out of flying it, I was probably a bit of a menace all weekend as I put over a gallon through it over the two days and this model can now eat up a lot of sky so apologies to any one who was a little intimidated by a very high speed Millennium wizzing past!

Webra 91's will be going in my other two Mill's shortly but my next step before this will be to give a OS91 SXH a fair try, I have a few exhaust options I need to test out on the OS, the new Curtis Y Muscle Pipe 2, the new Hatori #970 tuned pipe and one of the Hatori 90 sized mufflers, I hope to try these in the next few weeks if the weather holds.

I have already flown the OS 91 in a couple of other guys models and to be honest I will be very surprised if it can match up to the power of the Webra but there is only one way to find out for sure, watch this space-----.