Hey you,

You are exactly right! From that video it had shown injectors rated at a certain lb/hr but they did not flow correctly.

An Easy way to figure the injector thing out, is to call the guy at fuelinjectorconnection.com and tell him the specs you want (lbhr @ XXpsi). They will build you ones that flow match that for about 169 (If they don't have them already).

Best way:
Look for an injector that is a direct replacement for your current injector but has 4 holes. Basically search your year make model and see if a 4 hole stage 1 upgrade comes up.

Let me search for Ugly:

 

Ugly,

According to this guy from the fuel injector connection, he said that 19 lb/hr injectors come stock from 1990-95 (OBD1) and you can use the 24# if you can tune your ECU.
http://fuelinjectorconnection.com/sh...d&productId=52
If not, he said to get the 19lb/hr injectors.
http://fuelinjectorconnection.com/sh...d&productId=81

Ugly, I know that they said your year was 24.6 @ 39 PSI. But do this:
1. Check your fuel pressure to see if it is really 39 PSI
2. CHeck the part number of your injector and search it to see the specs

Then you will be sure. If you are running 49 PSI in your truck, the 19s would be perfect. Give the FIC guy a call and he should hook you up. He warrranty's them for 3 years, so if they don't run right, you can return them for a refund.

NOTE WHEN DOING INJECTORS:
there is a very thin wire on the black plastic connector. If they fly off when replacing the injectors, and you do not replace them, they will cause a misfire because the connection will not be tight. Seems weird, but it happened to me.

 

I know this info is in the FAQ's but I have a 94 318 and 360 and both have the same injectors. The part number on them is identical. I don't know if the info is wrong or something is off with my motors.

 

I may be speaking out of school here- Capt or Hey You, please correct me if I'm wrong..

injectors can be controlled by the PCM up to a point.. but it's actually just a little influence it has, and is built into it more for adjusting like old carbs were for altitude and such.. not much in other words..

19lbs injectors are more than enough to run these engines HP wise, unless you have had major performance enhancing work done.. if you were to use 19#r's, the duty cycle would be higher, because the engines conversation with the o2 sensor is going to reconcile you are running lean.. If you use 24#r's, the same conversation is going to make the engine attempt to lean you out because you're too rich..

bottom line- if in doubt, go with injectors rated at or below 22lbs.. make sure and get a good injector, and watch your a/f wideband gauging.. If you don't have a wide-band o2, then it's dangerous to even try- get stock injectors, or approved stock replacements.

Gerehead: is there a difference in psi on the rail for those years on those engines? If the PCM runs them at differing duty cycles I can understand.. That is likely where the answer to your situation lies imHo..

 

You can trim injectors DOWN (cut the duty cycle) but you really can't trim them UP. Basically there is a ceilling with 19LBers, and with 24, you can be good from stock, to mild, to 6 lbs of boost.

One of my college friends ran his 5.0 mustang at 70PSI through a fuel pressure regulator. Instead of getting new injectors, he just bumped up the PSI of the fuel system. Everyone on Muscle mustangs and fast fords forum thought he was nuts. but he had a cobra intake, AFR heads, scorpion roller rockers and a custom Ed Norton ground camshaft. So he had the motor work and airflow to need more fuel. He got 318 RWHP from that motor and ran 11s at the track. 4.09s and nittos too.

 

Biggest problem with running different size injectors without a custom tune is, Open Loop operation. In Open Loop, the ECM/PCM uses lookup tables to decide how long to pulse the injector. Too large of an injector, and you would run rich, too small, and you would run lean. Once the system goes into closed loop, computer would then use O2 sensor to alter pulse width, according to what it was seeing from the exhaust.

This was more of an issue on vehicles that did NOT use a heated O2, those that do, (which is most of the OBDII engines) start paying attention MUCH sooner to the O2 sensor, than their older brethren.

So, where you run into problems is: 1. Injectors that are too large, and even minimum pulse width runs the engine rich at idle (and possibly higher...). Or 2. Too small of an injector, and the injector is at 100% duty cycle (always on) before the engine gets to redline. Anything beyond that point, and the engine just continues to lean out.... which is bad.... (and potentially expensive.)

On the old OBDI GM systems, it was just one little setting to let the computer know what size injectors you had in there. (and chip burning for the OBDI GMs has a LOT of community support. Something I haven't seen for the dodge community.)

I have been exploring around, looking at the various 'tuning tools' available for OBDII systems..... there is a fair bit of monitoring software, but, seems you need some specialized equipment to actually have the ability to re-flash your PCM. Haven't seen much in the way of editors for the programming either...... Anyone else looked into this?

 

I wanna be able to do it myself. Having a good baseline to start from is always good though.

 

Hemifever trimmed my closed loop. Although the air fuel is richer during warmup, it still does not dip below 10.9. Whereas before the custom tune it would be pinned at 10.

 

HeyYou, I assume you meant OBD1??? I happen to make understanding various electronics, ie PROM burning, control systems, etc., my business, but am an ameteur at best when it comes to experience tuning computer controlled gas burner engine management setups. Reading your posts you obviously have a lot of the tuner experience but seem a little leery of the electronics side of things. Being OBD1 guy myself I'm interested in tweaking options too. Maybe we could work together on it. PM me if interested. I'd certainly have a look at your research and help out if I could.

 

I'd love to see some OBDI tuning. Chevy has got it all covered, Dodge has nothing. Only option now is the MOPAR Performance Computer, but that isn't really tuning