This is my first post, so by way of introduction, I am thinking of building an RV, a 7 or 8. I have previous experience building a composite Rotax machine, but that is of only limited help with an RV. I am midlands based and will need to get two other people involved to spread the cost.
 
I am trying to put together a specification and cost. Most of this is going well but I am struggling with the engine side. My current spec is for a 180 hp injected engine. My preference would be to build one. I have contacted Norvic and asked for a quotation on a kit and am expecting some numbers in the next few days. What other options should I be considering?  
 
Is it possible to get Mogas approval?  
 
I am assuming an average fuel burn of 33lph, is this about right? (I would rather be on the pessimistic side but do not want to be too far out).
 
Initial spec;
 
(Want to do touring with a bit of aerobatics)
 
Quick build 7 or 8
180 hp
Fixed pitch metal prop
MGL Glass with 2 axis autopilot
FW TRT 800H OLED mode s transponder  
FW ATR 833 radio with 8.33 spacing and remote control from MGL
 
Any help would be greatly appreciated.
 
Rod

Rod,
 
This might seem a bit daft, but the fuel consumption will depend on how far you open the throttle, and can vary from 22 lit/h (or less) at around 120kt up to 40+ lit/h if you charge around the countryside at 160kt. Many people chose 135kt as a good compromise between economy and speed, and get about 27 lit/h. The labour cost of building an engine is relatively low, compared to the cost of a new engine - say around 5%. But you can cost yourself hugely. My view is that one of the specialist homebuilt assemblers in the US/Canada is the best place to buy an engine - I favour Aerosport Power, but there are others. If you want to assemble it yourself then talk to LAA Eng about a supervising inspector before you commit any money - also investigate the stability of any company before you give them an engine's worth of cash.  
 
You also will need to decide whether to get a vertical induction or horizontal induction engine - the difference is in the type of sump and inlet tubes. The horizontal induction is more efficient but is more expensive, it also permits the use of a flat bottomed cowl (without the ugly inlet scoop). LAA Eng have been reluctant to approve injected engines to use Mogas, but I believe they are now relenting - would be worth contacting them directly. A metal prop is about twice the weight of a wooden prop, and makes the aeroplane vibrate more. Have you considered an MT (or similar) fixed pitch?
 
As for your avionics, I would stronly suggest that you fly behind any EFIS before buying it, and that you fly in an aircraft of the same type you are building that has the same autopilot fitted before buying. Just because an autopilot is available doesn't mean it works well. Most autopilots that are integrated into an EFIS - as opposed to in a stand alone box - don't work that well (but I don't know much about the MGL autopilot, hence the suggestion to fly with one in an RV and check for yourself).
 
The avionics scene is changing so quickly at the moment that it is worth leaving any choices to the last possible moment.
 
Pete

Sorry for all the questions!
 
Thats what the forum is here for!! And welcome to it, by the way!  

Quote from Rod1 on 10.09.2010 at 12:10:01:

Although it might seem counter intuitive, a 180hp engine will burn less fuel at a given speed than a 150/160. My cruise fuel burn at 150kt is always less than 33 lit/hr (160hp, carb, sensenich fixed pitch, 6A), so it would be almost certain that you would do better. It you go with injection, and run lean of peak, then your fuel burn could well be less than 30 lit/hr. I cruise anywhere between 120kt and 160kt, depending on how quickly I want to get somewhere and how much fuel I want to burn. It usually ends up at around 135kt at about 2200rpm (but my prop is limited to 2600rpm, a 180 won't be), and fuel burn around 27 or 28 lit/hr (but I don't count that often). The LAA will approve just about any fixed pitch prop for aerobatics, and most c/s props as well. I don't think there is that much of a performance degradation using a good wooden prop - such as an MT, GT, Hoffmann, Aymar-Demuth, etc (if any)  I believe all of these props use a metal leading edge to prevent damage from rain. I wouldn't use any of the UK prop makers as they don't seem to understand how to make a prop work over the speed range of an RV.  There are several advantages with using a wooden prop, such as light weight and smoothness. If your primary goal is low fuel consumption while cruising then have you considered an electronic ignition?  
 
I would think long and hard about building an engine yourself. The labour charges for building an engine are not that high (less than 10% of the price of an engine), but what will you miss out on? Certainly no warranty, the professional engine builders will do stuff that makes the engine run more smoothly (flow and volumetic balance of cylinders, for example), they will run the engine on a test stand for a couple of hours and (just) break in the piston rings. I have had 2 engines from Aerosport Power in Canada. Warranty support has been excellent and oil usage is 1 lit every 20 hours. They are very knowledgeable about what works well in homebuilts, friendly and approved by the LAA. I don't think the savings from building your own come close to the potential down sides. At the moment I don't believe it is possible to get Mogas approval, but I would ring LAA Eng and get the latest situation. Most 180hp engines are quite capable of running on Mogas, its just the LAA are not keen to approve it.  
 
If I were specifying a new engine it would be built from Lycoming parts by one of the US builders such as AeroSport, Mattituck or Barrett. It would be a 'normal' compression (8.5:1) parallel vale engine (ie nominally 180 hp) with fuel injection (doesn't matter if Precision of Airflow) and one electronic ignition (I would prefer a P-mag) and an impulse magneto (FD won't permit 2 electronic ignitions with a metal prop). I would use a horizontal induction sump (as it is more efficient) - so an -M1B type engine. I would also fit an oil filter in the 11 o'clock position on a 2" spacer (to clear the engine mount), a PlanePower alternator (Van's 'deluxe' alternator) and a Sky-Tec NL 'in-line' starter. I would also specify for the engine to be set up for a constant speed prop - you can always insert a bung in the front use the prop line, with a suitable governor cover plate, to return the oil to the sump - then if you do want a c/s prop it isn't major surgery. Use a Vetterman exhaust and the Van's snorkel inlet filter, and order a flat bottom cowl.
 
Its not that complex after a while. Its also probably not worth worrying about the engine unduly to start with, it will take a couple of hundred hours, or more, to finish the back end, and 100 hours for the wings, then the fuselage will take a while before it is ready for an engine, and most of the companys above can have one on your door step in around 8 weeks.
 
The emp kit comes by Fed-Ex, so get that, buy your tools from Gloster Air Parts and get cracking. Then sort the rest out once your underway.
Hope this helps,
 
Pete