Sizing Injectors for the Spitfire   

Actually this is pretty straight forward. Documentation in detail is avail. here on other pages on how to calculate the size injector needed.  If you need to understand this in more detail, go the F.I. links pages, and go to a few of the fuel injector sites.  In short form, here's the injectors I picked and why.    Matching the Injector to the Engine: generic calculation Injector Flow Rate (lb/hr) =     Engine HP x  BSFC                                                     Number of Injectors x 0.8 So for a Spitfire, to calculate the individual injector size for lets say 100 HP 4 cylinder using 4 injectors and assuming a BSFC of 0.5: Injector Flow Rate (lb/hr)  =  100 x 0.5 =  15.65 lb/hr                             4 x 0.8 Or a little more realistically for totally stock engine of around 75 hp. Injector Flow Rate (lb/hr)  =  75 x 0.5 =  11.72 lb/hr                             4 x 0.8       Well, you only want to run injectors at say a max of 80% duty cycle. I could use 14 lb injectors. But 19 lb (200cc) are the next largest 'standard' commonly available size injector. Since this is being set up for 45 mm DCOE throats, I think the 19's match these big bores. So19's! it is   .GREAT!  19 lb injectors are a dime a dozen. Mustangs use them as stock and apparently it's a common practice to swap them out for larger injectors. I bought a set of 8, you guessed it....Dutch Auction on EBay, winning bid.... $1 each per injector!  Bosch P/N F1ZE-84C (9F593) rated at 19lbs.  Identification = Silver metal body with gray plastics If you know an injector flow rate, you can solve the above equation for a rough  estimate of fuel system capacity like this: Engine HP = Injector Flow Rate x Number of Injectors x 0.8                BSFC For example, using the same estimated values from above: Engine HP =   19 x 4 x 0.8 =  121.6 HP      0.5 This is a much more realistic number for a stock spitfire engine. A calculator for this can be found here.

©1987-2010 All material copyright© Teglerizer 1996-2008	last edited  3/15/08	hits since last reset