What benefit do injectors offer?

[CTScott]

Originally Posted by BEEF

I was actually going to ask if you changed your injectors in your supercharger install thread.

I have heard that the supercharger runs on the fuzzy edge of needing the larger injectors. I have also heard that if you have done other upgrades (i.e. intake, exhaust, header) that you really need larger injectors with the blitz.

there again, just second hand info from a person that is not boosted so I really don't know.

I didn't change mine. I bought a set of 1ZZ's and intended to, but decided to do some experimentation first to determine if they are really necessary. What I found is that in theory the stock fuel system can provide the fuel necessary for up to approximately 12 psi of boost. The problem though is that the Yaris fuel pressure regulator is not adjustable to increase the pressure, proportional to the boost, to account for the increased pressure in the plenum. I modified a stock Yaris fuel pressure regulator to increase its limit by 6 psi to account for the boost pressure of the blitz. The videos below are ones that I created while doing some of the testing.

The flow rate of the stock injectors / fuel pump are sufficient, but the OEM fuel maps are not, so one has to run some form of piggyback fuel management to override the OEM maps. With the supercharger the included blitz fuel controller does this, but with the US market Yaris fuel maps, we seem to run a bit leaner than the Japan market maps do.

To account for that some S/C users have upgraded their injectors (but typically run very rich when not in boost {which will significantly shorten the lift of the cat}). Replacing the blitz fuel controller with a piggyback, like an AEM F/IC gives more control.

The other issue with the Blitz controller is that it does not have a mechanism for fooling the ECM, when the system is in boost, so the ECM will eventually "learn" about the extra fuel that the Blitz controller dumps in under boost and will "trim" it off. Resetting the ECM on a regular basis (pulling the negative battery cable for a minute) resets the fuel trims.


http://www.youtube.com/watch?v=852N-COD2Ns

http://www.youtube.com/watch?v=pH3mev88hoo