Planing a FI system

[JBarnes262 at aol.com]

Hello All
 
 I’m planing to build a Siera / Merkur based kit car with a 4.6 l V8 Rover
 engine. For this I want to build an EFI system which I can tune to suit any
 modifications ( Read WILD cam..... :-) )
 
 I hope the engine will have a maximum power of at least 350 Hp @ 5500, but as
 it’s to be used in a road car a lot of the time it will be at part throttle.
 With petrol / gasoline over here ( England ) costing almost four dollars per
 gallon, fuel economy in normal use is going to be important :-( 
 
 Using a target weight of 2600 lb., and a frontal area of 20 ft^2  I have
 calculated the horsepower needed to cruse at constant speed, and the extra
 power to " pick up " 10 miles an hour in 5 seconds ( moderate acceleration to
 keep up with traffic ).
 
 Mph     Hp cruse   Hp accelerate
 30          5          19
 50         16         32
 70         37         44
 100       99         63
 130       209       82
 155       350
 
 From this table it seems that I need very good control of fuel up to 60 Hp. 
 
 If fuel consumption is about 300g / kWh = 0.13 oz / Hp min then for an eight
 cylinder engine making 60 Hp, each cylinder will need an injector flowing
 about one once a minuet, but at 350 Hp the flow needed is about six ounces.
 
 If top speed is 155 Mph at 5500 RPM in top gear, engine RPM at 60 in top gear
 will be about 2000, this at 100 % pumping capacity would pull 5.6 Kg = 200 oz
 per minuet of air through the engine, or 25 oz per cylinder. If only 14 oz is
 needed for the fuel ( at 60 Hp output ) only 60 % pumping efficiency is
 needed, so the engine will be operating at less than three quarter throttle.
 
 
 To achieve accurate control at low power and revs I think I am going to need a
 sequential system with two injectors per cylinder.
 I need a small injector at 1.2 oz / min and a large injector at 9 oz / min for
 sequential operation. 
 As I’m not great with control units I plan to buy a "brain" which is easy to
 program from a PC. As the cheaper units only give a single output, I want to
 use the signal from the brain to control an elec
it which I can put together myself.
 I plan the cross over to run the small injector only up to 80 %, and then to
 change to running both injectors at about 10 % abruptly.
 
 Now here is where I need help.
 Can anyone spot any obvious mistakes in my calculations ?
 Are my units for injector flow right ?
 Can you recommend suitable injectors and brain ?
 Will my idea for a crossover work ?
 What have I missed :-) ?
 
 Thanks for your attention.
 
 Jonathan.