Please help me to understand fuel injector size and how it effects the F/A. In other words if I replaced the stock ones with 60s would the mix not be too rich? This is one of the questions I do not know correct way to ask. Thanks

 

Fuel injectors size refers to the maximum amount that each injector can provide. For example 24lb injectors can pump a maximum of 24lbs of fuel per hour. The fuel air mixture is calibrated by the engine computer using inputs coming off of the MAF sensor and throttle body. You can't just throw on bigger injectors without making the proper calibration changes. In general the 24lb injectors on the new mustangs are able to support up to 400hp. If you plan to exceed that then you are looking at moving up to the 39 pounders which will cover you past 600hp. Once you go past that you will need a new engine before you will need even bigger injectors. I have the SALEEN blower on mine and am running about 435hp with the stock 24lb injectors. Unless you are going bigger than that spend your money on something else since new injectors, MAF and calibration will run you about 800 bucks.

 

You're not shopping in the right places! You can get a Lightning MAF and sensor and a set of 41lb injectors from buyfordracing for $370.

 

Thats a good price but remember he would need a tuner too. The tuner would be a couple hundred more bucks. To many people buy more injector than they need and it is a big waste of money. I am at 435 horsepower right now and I have maxed out my 24lb injectors but buying 39lb injectors won't do anything for me. They will squirt 24lbs per hour when I mash the gas just like the 24 pounders do now. I will buy bigger injectors if I go for higher HP. Mongoose what is your horsepower goal? That is where you should start with your question on injectors.

 

http://auto.howstuffworks.com/fuel-injection.htm

 

24 lb/hr is good for about 330 hp naturally aspirated street V8 engine using 85% duty cycle and doesn't account for higher fuel pressure demanded by FMU's. The stock MAF is good for about 380 hp N/A and the same disclaimers apply.

I was surprised to see how low the stock MAF is rated in terms of air flow at 5V, but seems typical of OEM MAFs. Almost any aftermarket MAF (or a factory Ford MAF like the 80mm Marauder) plus a low restriction airbox would add 10-20 hp. A conical "CAI" kit isn't necessary but people want them and that is what vendors sell. I would prefer an OEM-style airbox and panel filter but with a better MAF and inlet tube.

 

Don't confuse him. You are talking about old technology. The new mustangs are fine with the 24lb injectors up to 435hp. Saleen has thousands of them out there under warranty with that set up. JDM engineering doesnt go to the 39 lb injectors until they go over 400 rear wheel hp and that is about 450 at the fly wheel.

 

Mongoose what is your horsepower goal? That is where you should start with your question on injectors.
My plans are to leave it up to the engine builder. I was just asking because I do not know dip about them and this is the way I learn.

 

Thanks. There are loads if information here. Happy that you pointed me in that direction.

 

If you change your injector size, then your ECU will need to be reflashed with a tune that uses the new injector size. The injector size is one of the values you can change using the SCT tuner.

There was a good article recently in MM&FF
http://www.musclemustangfastfords.co...l_control.html

 

Let me try to put this into layman's terms. The PCM is originally calibrated for a specific size injector. For argument's sake, let's say 24#ers. Now, you replace these injectors with 42#ers. Your PCM has no idea you've done this. It still "thinks" you have 24#ers. So what happens? The injector pulse width commanded by the PCM, which is good for 24# injectors will allow a LOT more fuel with larger 42# injectors, causing an overly rich condition. So anytime a significantly different size injector is used, the PCM must be reflashed with the correct parameter called Injector Size Constant that's appropriate to the size actually being used. Unfortunately for the hand-held tuners, you only get a limited number of constants. So unless you're into modifying the definition file yourself with software (i.e. SCT's Pro Racer), you should choose an injector size that correlates with one of the choices in the canned definition file ("tune" as you guys like to call it).