Contour Enthusiasts Group Archives Forums Modifications Zetec Performance Injector Sizes

I've seen the question of "How big do my injectors need to be for XXX horsepower?" With more and more Contique Zetecers going FI, here's some good info.

(injectors size*number of injectors)/0.55=Crank Horsepower

19# Injectors=(19*4)/0.55=138HP
24# Injectors=(24*4)/0.55=175HP
30# Injectors=(30*4)/0.55=218HP
42# Injectors=(42*4)/0.55=305HP
50# Injectors=(50*4)/0.55=363HP
60# Injectors=(60*4)/0.55=436HP
61# Injectors=(61*4)/0.55=444HP
71# Injectors=(71*4)/0.55=516HP

Please keep in mind that these numbers are all for crank horsepower and that you never want to run an injector wide open. With a 90% duty cycle you would get the following...

19# Injectors=((19*4)/0.55)0.90=124HP
24# Injectors=((24*4)/0.55)0.90=157HP
30# Injectors=((30*4)/0.55)0.90=196HP
42# Injectors=((42*4)/0.55)0.90=275HP
50# Injectors=((50*4)/0.55)0.90=327HP
60# Injectors=((60*4)/0.55)0.90=393HP
61# Injectors=((61*4)/0.55)0.90=399HP
71# Injectors=((71*4)/0.55)0.90=465HP

Again, these numbers are all for crank horsepower. You would loose an additional 10-15% of your horsepower with a manual and 15-20% with an ATX.

You also want high impedance injectors that have Bosch (EV1) style connectors.

CFM carries them in sets of four and have very good prices. McNews Automotive also carries the Ford Racing injectos in sets of four.

I hope this helps.

Later,
Ben

But don't our cars have 130hp and 17lb injectors?

I always thought that they were 19's. According to the data they would have to be 19's.

I could see the SPI Focus using 17's due to the lower output. Maybe some of the Mondeo's running 1.8L Zetecs.

Contour Zetecs do have 19 lb injectors.

The "(injectors size*number of injectors)/0.55=Crank Horsepower" is a very conservative formula that is usually used for forced induction applications. 0.55 BSFC is rather high for a naturally aspirated 16 valve motor. For a naturally aspirated Zetec motor, You shold be using (Horsepower*BSFC)/(Number of Injectors*Max Duty Cycle) = lb/hr needed.

Ford BSFC you can use a number in the range of 0.40 to 0/45.

So, if you have 170 HP at the flywheel and use a 0.45 BSFC, have 4 injectors and want 85% max duty cycle, the result would be:
(170*0.45)/(4*0.85) = 22.5 lb/hr.

If you can't get them in the size you need, you can round up. There are some injector manufacturers that sell 23 lb/hr and 24 lb/hr injectors.

I beleive that pre98's have 16lb injectors & post98's have 17lb injectors.
Duty cycle and fuel pressure both play into the equation as well.