The Fuel Injection about Carburetor (4)

Aug 25
08:34

2013

Olivia Tong

Olivia Tong

  • Share this article on Facebook
  • Share this article on Twitter
  • Share this article on Linkedin

It’s surprising how often this is overlooked, but it is utterly crucial to make sure that you choose the correct wiring harness and computer designed to work for a specific vehicle application. If you don’t, you’ll be forever chasing electrical gremlins and suffering with a car that just won’t run properly.

mediaimage

Crucial Tips

It’s surprising how often this is overlooked,The Fuel Injection about Carburetor (4)    Articles but it is utterly crucial to make sure that you choose the correct wiring harness and computer designed to work for a specific vehicle application. If you don’t, you’ll be forever chasing electrical gremlins and suffering with a car that just won’t run properly.

 

Another aspect when choosing fuel injection is to select the right camshaft. Cams designed for fuel injection applications feature higher lift profiles and wider lobe separation. Because huge amounts of air aren’t required to be drawn down from the top of the manifold, the heads and intakes on EFI engines are designed to promote greater airflow inside the intake runners and ports, and the low lift and wide separation on the camshaft allows greater promotion of power and torque. Unless you’re lifting the entire engine and EFI system from the donor vehicle and are not too concerned about individual performance, you’ll want a custom ground camshaft designed to work specifically with your engine and fuel injection system to achieve a balance of good drivability, as well as ample power and torque delivery across the rpm spectrum.

 

Calculating Injector Sizes

When it comes to fuel injection, figuring out the right size injectors to use is critical, but it is also one of the most misunderstood aspects of EFI.

 

In order to determine the size (lb/hr or flow rate) required, you need to find out what your engine’s Brake Specific Fuel Consumption (BFSC) actually is. This term refers to its efficiency, i.e. how much power it makes in relation to the amount of fuel it uses. For most mild-street engines a BFSC of .50 is the accepted rule of thumb. More aggressively modified, but normally-aspirated, engines are rated around .55, while those using power adders, superchargers, turbochargers or nitrous are rated at .65.

 

When calculating injector size, there are some general terms that are widely accepted, one being that optimal injector efficiency is around 80 percent. More than that, and the injectors tend to be overworked, causing heat to build up and efficiency to rapidly tail off.

 

Taking that into account, we can use the following formula to work out our required injector size based on rear wheel horsepower (H), BSFC, C (the number of cylinders) and D (injector efficiency):

H x BSFC / C x D So, if our normally aspirated, mild street V-8 engine is rated at 300 horsepower, this will give us:

300 (hp) x .50 / 8 x .80  = 20.9

Based on that calculation, we would need an injector that’s closest to this flow rate for optimal performance. In this case, it would be 24 lb/hr units, as found on many OE performance applications and through aftermarket suppliers.

 

One of the most important elements when planning your next hot rod project is the engine, and choosing the right fuel system for that engine.

 

Bigger, heavier cars, like this custom 1950 Mercury, often require torquier, larger-displacement engines to move them. Multiple carb setups or, if you’re not too concerned about tradition, tuned port fuel injection, can really add benefits.

 

When it comes to engines and fuel systems, donor cars are a good place to start. This well-used Lincoln Continental Mk IV was found at a swap meet. Its big 460 V-8 and four-barrel carb are the perfect foundation for a custom sled.

 

Find out more aboutToyota 3T carburetor by visit miparts.com.