Contour Enthusiasts Group Archives Forums Modifications General Mods Fuel Injector Compatibility

This is a general kind of inquiry into what to look for when switching in a bigger fuel injector(possibly from a different application). What kind of things have to match up and what parameters don't matter? I am aware that the MAF will have to be recalibrated, but I just want to know what really matters when it comes to the switch.

Please, Please, one at a time... :rolleyes:

Why wouldn't work? Ford injectors all basically look the same but no doubt that there would have to be some recalibration. Some guys in Focaljet have upgraded their injectors. Try looking on there www.focaljet.com

My main concern is the difference between injectors used in returnless/reteun systems. Also sizing issues(ie diameter of the top/bottom of the injectors where they connect to the fuel rail/manifold).

All Fords use Bosch type injectors. The injectors are the same for both the newer non-return fuel systems and the older return-style. The following Ford injector sizes will work in your 4cyl Zetec Contour: 19lb, 24lb, 30lb, and 36lb. The use of 42lb or larger injectors requires a low impedence injector driver in your EEC. However, your MAF meter MUST be recalibrated for the appropriate injector size. It is important for you to know that bigger injectors do not make more power.

The only time you really need to increase your injector size is if you are maxing out the flow of your current injectors. Normally this only happens when you've made SUBSTANTIAL airflow improvements. The two ways an injector performs are pulse width and duty cycle. These are terms for the time an injector stays open and the amount of fuel it delivers. Typically, an injector should not exceed 90% duty cycle. If so, you may need to step up injector size. On the '98 and older return-style fuel systems, the easier (cheaper) route is to increase fuel pressure a bit. In Ford cars, the designers usually over-engineer some systems for relaibility purposes. The chances are, even after bolting on a few simple mods like a hi-flow intake pipe and better exhaust, your stock injectors will be able to supply the extra fuel needed just fine. You can find out your current injector duty cycle by hooking up an OBD-II scan tool. Some shops that do dyno-tuning have equipment that can record and play back EEC readings in real time. The more expensive scan tools display both pulse width and duty cycle.

An example of proper injector sizing is my '95 Mustang 5.0. It came with 19lb injectors. My first mods were: cold air pipe, throttle body, full exhaust (headers, H-pipe, muffers). The stock injectors worked fine with the extra air flow. My next set of mods were more drastic: larger port aluminum heads and better intake manifold. With these mods, my stock injectors were just over 95% duty cycle. I then switched to 24lb injectors. The bigger 24lb injector size gave me more "headroom" and less chance of a damaging lean condition than the maxed out stock 19lb. When I installed my Vortech, I could have gone with the next-up 30lb size, but I was advised that they would be at their limit with the blower and desired boost level. The current 36lb injectors leave me some room to play with if I want to step up the boost. The down-side of going with an injector that's too big for your combination, is poor drivability and fuel loading up the cylinders at idle. Unless you're adding a blower or dry nitrous kit, your stock injectors should be fine.

8AZ28, you're mostly right. However, the injectors from different years of vehicles may differ in the electrical connector used on the injector and corresponding harness as well as fuel rail feed location. Some Contours, Mustangs, F-150s, etc, use a rectangle shaped clip with a retainer along one of the long sides. The newer Contours, some '98 Taurus's, late 99+ Cougars have a smaller oval connector with two "tangs" on one side. Granted the ohm rating on the two injector styles are comparable, there would be considerable work involved to splice over an injector harness if you didn't buy the correct injectors in the first place.

The 3rd Contour type of injector is a side feed injector (V6 from '95-'97) shared only with the Ford Probe and would not fit the Zetec fuel rail. The Probes injectors are of the same rating and would provide no increase in flow for those years of tour.

That being said, I *think* the Zetecs use the rectangle connector style injectors, at least on some years. The easiest way to know is find out which electrical connector and which fuel rail feed you have (top or side feed) and go from there. The Ebayers usually provide pictures of these two locations since many injectors are used across many build platforms, even between brands.

Not all Ford Injectors are Bosch. I have a set of 24lbs, that came off a 2001 Taurus that aren't.

Thanks for all the info guys. OK, now I'm starting to get somewhere. So, brad, how do you differentiate between top/side feed injectors? Is it the orientation of the injector to the manifold, fuel rail, or something else intirely? I was eyeballing 32lb mustang injectors for either a high CR or a turbo build-up. I am still trying to figure out which option offers the best
hp/$ ratio.

The side feed have the fuel rail down on the side with the electrical connector near the top. The top feed style have the electrical connector near the top with the fuel rail directly on the top. There are several different styles of electrical connector, even just for one "style" of injector. Your best bet is to take one of yours out and take a picture of it to compare to what you find on ebay/etc. Then you'll know for sure.

My best guess??? The Mustang ones *should* work fine providing you make all of the calibration changes.

Bigger injectors (by themselves) have a 0 hp/$$$ ratio. Even if you get a calibrated MAF or chip or whatever. Unless you need more fuel than the stock injectors can provide at maximum flow, you don't need them.

Hypothetical example: Two owners have identical engines that run 60% duty cycle on their injectors at worst case. They both want to richen the fuel mixture for more power (and we'll assume richening will be effective).

Owner A buys a S-AFC (for example) and uses it to richen up at WOT. Goes to the dyno and gains 5 hp after extensive tuning. Stock injectors are now running 70% duty cycle.

Owner B buys a S-AFC, and gets larger injectors to go with it. Goes to the dyno and gains 5 hp after extensive tuning. Bigger injectors are running 50% duty cycle.

Who wins? Owner A, because he can now go buy a something else with the money he saved on injectors.