Cold Start Injection


This diagram above shows how you would use a cold start injector setup. It's quite simple and is probably the easiest way to get more fuel as well as the dirt cheap route. All you need is a vacuum/pressure switch that engages around 0.1 of positive pressure. Pressure switches work very simple . They are like a plastic T for vacuum hoses but they also have a switch attached that turns off or on at the pressure its set at. So there are a few sites on the Net that can help you find a pressure switch. You run a ground from the pressure switch AND from the injector, to the chassis/engine. See cold start injectors are simple, they either spray full tilt or none at all. When they see 12v of power they spray 100% capability. So you have the pressure switch set to turn on at your desired boost level (0-1psi) and when the switch hits that boost level the switch gives the injector(s) 12v and they begin spraying. You just have to have a fuel pump and T the extra injector(s) off the main fuel feed hose coming from the fuel tank before the stock injector rails. WA LA!! You just need a wideband in your car or on a dyno so you can make sure your around 12:1 AFR. 

Stand Alone Fuel Management (EMS)

There are a lot of companies that make full stand alone systems for cars. Unfortunately there are very few that do for our KL's. SDS has a fairly pricey setup but works very well and can run both fuel, and ignition for under $1,400. Nice thing about that is you can get rid of the junk OEM distributors which fail OFTEN. SDS also has a built in MAP and crank position sensor. Basically a engine management setup is going to replace 90% of your sensors in the car or rewire the old sensors to work with the new computer or ECU that is running things. My best recommendation for stand alone is Megasquirt. I will be using MegaSquirt v2.2 on my new engine. Utilizing MSD 6 and blaster2 coil with a 93/94 distributor I will control fuel and spark entirely using MegaSquirt. This is where a lot of knowledge and experience come into play. MS is truly a DIY tuning method of course the MS forums can be great help. It is becoming the cheapest and most used system with the mazda crowd because there is so much free support for it online and its less than $200 to build your own setup. So this is my first recommendation for EMS on KL03's.

Extra Injector Controllers


This is an SDS (simple digital systems) extra injector controller. I used this in conjunction with a 3:1 FMU and boosted 10-12psi just fine. So extra injector controllers give more fuel via extra fuel injectors welded into the intake much like the cold start setup. But with these you get real injector control rather than just full 100% duty cycle when they engage. I had the setup above dialed in to begin spraying when it saw 2in/vacuum, or just before the engine reaches positive pressure. That way it was a smoother transition from vacuum into boost. And as RPM's and boost increase the fuel injectors also increased in the amount they sprayed. So when it first begins to boost 1-2psi the injectors are only at 20% duty cycle but when I reached maximum boost it was around 90% duty cycle. Overall throttle body injection works well but its not a 100% full proof plan for every car. For example my intake manifold was so severely ported that even when running naturally aspirated the same amount of air wasn't getting to the cylinders equally. So adding more fuel to that equation was never perfect. Although it did its job well. If someone had a mostly stock intake I would recommend one of these setups because the OEM design of the intake is more accurate then after its ported out and the VRIS plates are gutted. SDS, GReddy's Rebic, and HKS all have extra injector controllers for a decent price on ebay which is where I got my SDS and then sold it again. I would say SDS is the easiest to use however they only allow 2-4 injector setups.