so i went and got myself a new MOTOR wooohoo!!!! from powertrainproducts.net . looked around and this alll i could find that sounded safe and quality. but i wanna go and change my injectors to probably accell or venom . im guessing their 19lb but was told by local off road shop that its fine to go to 24 if im doing it. said should be fine and wont need a chip.
truck is vin L , so i guess my ? is ohms and is this right what they said. anyway merry xmas and thanks for the input s

 

Your shop is total BS.

The best injectors you can run in your setup are OEM of the stock size. Unless you are running an aggressive can or forced induction the stock injectors will deliver more than enough fuel for any conditions you are going to experience. Larger injectors will do nothing but make your truck idle worse, and waste fuel. Sure the computer can adapt to some extent by reducing the injector pulse width, but there are times when the computer cannot monitor live mixture readings, such as at cold startup or Wide Open Throttle.

Looking at your mods list, I'd say you really just want to spend money, as most of those parts are a poor return on investment.

Again, unless you have some pretty major mods to justify running a larger injector, you will see no gains performance wise, and it will most likely cause additional issues. If you run a tuner, you could clean up the idle and WOT enrichment, but whats the point, the stock sized injectors can handle whatever you throw at them.

 

What Khan said is totally true.
Your upsetting an engineered system using larger injectors.
First, the 19 lb injectors flow a certain amount of fuel based on the normal fuel pressure of 38 psi.
If you check certain tables for fuel injection it will show you these injectors will flow enough fuel to make close to 280 hp at their max open pulsewidth .
Your motor will not come even close to that power or needing that much fuel.
Many people think larger injectors makes more power but it does not work that way.
Using 24 lb injectors at the same 38 psi will cause the PCM reduce the pulsewidth trying to maintain the same amount of fuel as the 19 lb units.
Another parameter that gets into the act is the Mass Air Meter. It's calibrated for 19 lb injectors.
Another item that you have is the intake vacuum to the fuel regulator.
As it is, the vacuum reduces the fuel pressure at idle so less fuel is metered by the stock injectors that the motor does not need.
You use bigger injectors and this agravates the situation even more.
This could bring on cold starting and idle issues from to much fuel being metered.
In these injection systems, the min fuel metering pulsewidth must remain above a lower limit of about 5% pulewidth opening or metering becomes unreliable and idle qualty goes to hell.
The PCM will hunt for the idle speed it can't find because it will close the IAC down. When the idle slows it opens it again trying to match the idle speed to the software table value it can't match and the hunting continues.
Bottom line is you cannot just make ***** nilly changes and expect an advantage inside an engineered system.
The system reacts to it and most often negates it and things results that you don't like.
Sorry for the indepth explaination but there is a reason why it should not be done on a stock motor.
Good luck.

 

does the ohm rating matter or are they set one way for year and model or set a search for more specific rating

 

unless your running 300 horsepower the 19's are fine...just buy a rebuilt set that has been matched flow. should be under 200 buck. i would use the revised one with the 4 holes

 

I did run dyno with my headers, exhaust, Cai and where I dynoed it they put on a eco tune to c wut we'd get and it was like 265 torque and 220 hp or something and that was when it was already going down hill and eco not performance so I'm woundrn if 21lb will totally throw truck off . I'll probably just fo with the 19 . Thoughts on maf mines still stock

 

19# will just fine i run 19;s in one of my mustangs with 325 hp

 

So I was running My 24lbinjectors and today I put my 19lb ones back in and it did seem to start better. Bottom end possibly was better but I'm feeling. The top end wasnt As good. I didn't reset the computer. I'm hoping fuel mileage will b like better. But I'm going to order this sct 90mm maf tuned for 24lb then sct.Chip

 

You need to pay attention to why there is 19 lb injectors as stock in place to begin with.
24s tend to over fuel the motor at starting and low speeds.
This effect is what you observed when you changed back to the correct sized injectors.
Here is why you saw this; the larger injectors were operating at pulse widths below their normal 'closed down metering point'. At this point, fuel metering becomes un-reliable and out of fine control from the OX sensors feedback signals.
This is why the 19s are used and the fuel regulator has vacuum applied to 'further reduce' fuel at idle.
Larger injectors defeat these dynamics.
.
The system was designed around these parameter so you can't just decide bigger is better.
You don't need the larger injectors.
.
Further, if you check fuel injector charts on how much power each injector size is capable of you will quickly see that your motor does not make enough power to use the 24 lb units and as you see, they over fuel the stock motor at less then wide open throttle plus much poorer fuel mileage.
Form the table you would see one injector meters X amount of fuel at rated 38 psi that supports Y amount of HP. Times that amount by 8 cylinders and you have the total power 8 injectors will support at rated fuel pressure.
A check of the trim tables will show the over fueling because the tables are shifted to far from normal but still within limits or rich codes would be set..
Do not make the mistake of thinking more fuel equates to more power. It does not. Only in a Diesel engine is that true where the there is likely no throttle body to regulate air like a gas motor. Diesel power is mainly a function of fuel supply control as the throttle.
Good luck.