I have a Ford 5.0, 340HP crate motor with 30# injectors, 225 lb fuel pump, stock fuel rails from a 93 mustang and would like to know where do most Ford guys run their fuel pressure entering the fuel injectors. how much pressure is too much and how much is to little. I also find that the older computer from the 93 mustang is not very tunable without going and putting the car on a dyno. Any ideas would be appreciated.

 

since nobody answered my question, I since found out that 39.5 lbs is a good start for a ford 5.0.

 

I hadn't seen this post before. Most fuel injectors are given their flow rating at 43 psi. You are correct that 39 psi is a typical Ford factory pressure. That will still give you plenty of fuel at a reasonable duty cycle with 30 pounders.

You are also correct that you will need some tuning when going to 30# injectors. Typical path is getting a MAF calibrated for 30 lb. injectors to "fool" the ECU; best way is having a tuner actually program the injector size into the ECU. If you have a really good tuner that knows how to do it, you can upgrade to the 1995 Ford ECU which is a better, faster, more sophisticated ECU. It does require some pin-out changes.

 

thanks for the update. Is the 95 ECU a plug and play?

 

NO, you have to move some of the pins around at the EEC connector. I have one that I plan to install in my car. If you get one from an automatic transmission equipped car, it will work, but your tuner guy will have to reconfigure it.

 

Another option is to switch to a plug-n-play MegaSquirt 2 or 3. Because the MS eliminates your mass air meter (and any need to upgrade it) and the cost to have the car tuned the price of the MS ecu can come in cheaper than working with the stock Ford computer. If emissions is not an issue in your area and you are willing to do a little reading on the basics of programming a fuel injection system I highly recommend it. I went this route a few years ago and have been very happy.

As an added bonus the MS allows you to use ANY injector you want. I was able to source a set of stock 2011 38.2# Mustang injectors for $50 on ebay. On that one item alone I saved a ton of cash compared to buying even used 36# red top injectors.

-Jason

 

I've always understood the additional flexibility of stand-alone systems but had never considered how the component offset could make it an affordable alternative. That's very interesting.

Before deciding to go this route I think the question for the average car buff is whether they could and would realistically learn to program it effectively, or would they never get it right, damage their motor trying, and/or end up paying someone else a bunch to clean up their mess.

Obviously some people have been quite successful programming their own. I know just enough about the complex relationships between timing, cylinder pressures, fueling, and other dynamics that I'd never have the courage to try this. For me, it's too much financial risk for too little return. I surely admire those who have mastered it, though!

 

If you have a pretty standard 5.0 its pretty much as simple as plugging the new ecu in (5 min) loading the canned tune that DIYAutotune had into it via a laptop or net book (about 10 min) and then driving it around with "autotune" in Tunerstudio clicked on on your laptop for a few drives. It only becomes complex when you want to start fine tuning things like "fuel over run cut off" or acceleration enrichment or change cams out or something.

Keep in mind there are a few "hidden costs". If you really want to do it right you will need a wideband 02 sensor and decoder. These run about $130. Add another $60 if you want a gauge to show what its doing when you are not hooked up to a laptop or your phone. You will also need a laptop to tune it, I picked up a cheap netbook for $200 but in retrospect really should have gone for a used laptop for the same money. While you can datalog onto the laptop the best way to do so is through a smart phone which adds another $60 for a Bluetooth transmitter to the bill. If you really like how that's going and want to have a GPS input that is more accurate than your phone you'll need a remote GPS antenna for you phone which adds another $100...it keeps adding up but is fun.

-Jason

 

Thanks for all the info. Not being to computer savvy: is the "autotune" program something you can download into your computer as a program. Like a CD rom? Because the megasquirt 2 sounds like a good ticket after initial investment to have.

 

It's part of the tunerstudio software package.