I have recently been rambling about injectors in a couple of different threads and I wanted to add some clarity/links to this subject. This may help people understand what injectors do, and their importance to an engine running correctly after making modifications to boost power.
FROM - https://www.injectorsonline.co…-to-choose-fuel-injectors
Nothing will have your engine running rough faster than the wrong choice of fuel injectors. Not only that, you risk ruining your engine altogether if you make the wrong decision. So it’s important to understand the factors you need to consider when deciding which fuel injectors are right for your setup.
Bigger is not always better
It’s easy to fall into the trap of thinking that bigger fuel injectors equal more power, but unless your engine is set up to deal with the extra fuel, you’ll be on a fast track to trouble. The excess fuel will flood the engine and it either won’t run at all, or will be running too rich. This can lead to fouled spark plugs and damage to the engine.
There is a whole range of things you can do to increase your fuel capacity to accommodate bigger fuel injectors but the main ones are:
- increasing the airflow – this can be done by installing a turbocharger or supercharger, or fitting a bigger throttle body
- installing a bigger exhaust
- remapping the computer
- fitting a bigger fuel pump
- adding an adjustable fuel pressure regulator.
Running too lean
At the other end of the scale is where you’ve modified the engine but the injectors aren’t delivering enough fuel to keep up. If you’ve added a turbo, a higher flowing fuel pump, a bigger exhaust and remapped your computer, you’re going to need bigger fuel injectors. Otherwise your car will be running too lean and you’ll have a situation where your it is sluggish and lacking in power at best, or at worst, you’ll burn out the pistons and destroy the motor.
Size does matter
Both of these scenarios highlight why it’s important to have the right-sized fuel injectors. The best place to start to work out the right fuel injector size for your needs is to get an understanding of how much horsepower you expect to achieve with your modifications. We recommend you enlist the aid of a reputable car tuner to determine this.
The other critical factors are:
- whether the car is turbocharged or supercharged, and
- whether you are using E85 or standard pump petrol.
Once these factors have been established, you can use the charts below to help you select the correct injector. The following considerations should be taken into account when using these sizing charts: horsepower is at the engine (you lose roughly 30 percent if calculating from the wheels); injector duty cycle is 80 percent; and fuel pressure is 43.5 psi (3 bar).
Flow Rate Conversation Website
https://www.deatschwerks.com/flow-rate-conversion
Fuelinjectorclinic.com Flow Calculator
https://fuelinjectorclinic.com/flow-calculator
The stock Slingshot injectors are 35 lbs/hr models. The above information and Flow Calculator tool are great resources in understanding what injector should be chosen for your power goals. They are used as a rough guide and final validation comes from dynoing or street driving the machine while closely watching the injector duty cycle (software is available that does this). In almost all cases, tuners don't like to see injector duty cycles over 90% during desired AFR conditions.
Example for most forced induction kits making around 300whp...