24lb injectors vs 19lb on stock 5.0.. Going back to stock..

billison · Mar 19, 2013

Ok, this is not the topical I want to upgrade injectors post.

My car came with 24# injectors and a maf to match.. It has exhaust but seems to be otherwise stock .

From what I read online, the stock Injectors are fine till 400 hp..

Would it be worth my time to swap back to stock? Or are they hurting me at all?

Car runs fine as it is and I'm leaning towards leaving well enough alone

srtthis · Mar 19, 2013

not sure if it will change much if anything for you but if you want to go back to stock i can send you a stock MAF and injectors if you want to swap them out

billison · Mar 19, 2013

My main worry is it running rich. Plus it's totally unneeded without mods.

RangerJoe · Mar 19, 2013

Stock injectors are not going to get you to 400HP. Barely 300HP. In my opinion, leave them. They will give you room to grow in the future. The 1993 Cobras came with them stock, and I think they were rated somewhere aroung 240HP. With Small bolt ons, 240HP is easily achievable.

Joe

f8tlfiveo · Mar 19, 2013

billison said:
From what I read online, the stock Injectors are fine till 400 hp..

Not everything on the Internet is true.. I wouldn't even trust 19lbers at 300hp. Just leave well enough alone

billison · Mar 19, 2013

Thanks! That's what I needed!

madspeed · Mar 19, 2013

as long as your maf is matched to them you're fine.

TOOLOW91 · Mar 19, 2013

after I blew my built motor up I went back to stock and my car runs better with the 24s in just leave them it leaves room to grow

jrichker · Mar 20, 2013

Fuel injector sizing & injector photos

Revised 11-Dec-2011 to add larger injector sizes to injector table

Injector HP ratings: divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines at the flywheel.

Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

19/.5 = 38, 38 x 8 = 304 HP x .85 = 258 HP
24/.5 = 48, 48 x 8 = 384 HP x .85 = 326 HP
30/.5 = 60, 60 x 8 = 480 HP x .85 = 408 HP
36/.5 = 72, 72 x 8 = 576 HP x .85 = 490 HP
42/.5 = 84, 84 x 8 = 672 HP x .85 = 571 HP

Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.

See http://users.erols.com/srweiss/#jcalc to get the calculators used in these examples.

Here's the duty cycle explanation. Duty cycle is how much of the time the intake is open the injectors are turned on. The 85% figure means that for 85% of the time the intake valve is open, the injectors are spraying. The idea is that you want some percentage of the duty cycle left over so that you have some room to grow the process.

If you are at 100% and you need more fuel, all you can do is turn up the fuel pressure. That means the whole fuel curve from idle to WOT is affected. Maybe you are already too rich at idle, and turning up the fuel pressure makes it worse. If you had some injector duty cycle left to play with, a custom tune could use that where it is needed. That would not over richen the whole range from idle to WOT.

If you did turn up the fuel pressure, you might be able to change the injector duty cycle to get the air/fuel mixture ratio you want since the injectors will have extra fuel delivery capability.

With larger than stock injectors or higher that stock fuel pressure, you will need an aftermarket MAF that matches the injector size. The MAF “lies” to the computer to get a fuel delivery schedule that meets the engine’s needs and isn’t too rich or too lean. The best strategy is an aftermarket MAF and a custom tune to insure the best air/fuel ratio over all the RPM range.

Don't forget to increase the fuel pump size when you increase injector size or significantly increase the fuel pressure

Diagram courtesy of Tmoss & Stang&2birds

Foxslider · Jan 6, 2020

I have some unknown injectors on the car. Guy i bought it from said 24#. But it is most certainly a stock MAF. I was going to get them cleaned and whatnot when i do my topend. Is it possible to flow test them and find out what they are? They are light purple. Can take a pic. also if that'll help.

I'll have to see what MAF this is. It looks like Ford never made a MAF that was for 24#. I think im giong to buy some rebuilt one's off ebay i see, $80. Id spend $60 at least getting these cleaned. And they're probably making it run rich.

General karthief · Jan 6, 2020

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Foxslider · Jan 6, 2020

Found em in this thread. https://www.stangnet.com/mustang-forums/threads/what-injectors-are-these.877240/
Same one's. I pulled the part#. 9L3E-FA. Skinny purple inejctors w/ adapter plugs. Still working on identifying them.

Foxslider · Jan 6, 2020

Found it... https://seattle.craigslist.org/see/bfs/d/seattle-eight-ford-motor-co-fomoco/7043142039.html
I cant see the FOMOCO part on mine. But that's them. And i'm on stock MAF. So going back to 19er's. Now unless i have a Cobra ECU, this means it was running rich.

Blown88GT · Jan 6, 2020

You can change the MAF housing & use the stock sensor in it. There are plenty of used C&L's out there. The C&L uses calibration tubes to match the injector. C&L retired & sold to MAC products, the webname was purchased by American Muscle. All you need is a C&L housing with the Blue calibration tube.
Need to see pics of your current intake since he C&L is sensitive to configuration as is the factory MAF & if plumbing is anything that deviates from stock.

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Foxslider · Jan 6, 2020

I thought about doing a MAF swap also. Only reason i would need 24's is if i add nitrous later. Not sure ima do that though. I kinda want to get these fresh rebuilt/cleaned 19's and sell these 24's for an even swap ish. Vs. Cleaning the 24's and gettn a MAF cost me $200 more.

Blown88GT · Jan 6, 2020

If you need a set of 19's, let me know. They were removed 15-20 years ago. Probably need no rebuilding/cleaning.

Foxslider · Jan 6, 2020

Shoot ya, i'll take em. I'll throw ya $20 to cover shipping.

Blown88GT · Jan 7, 2020

I've decided to keep them.

Foxslider · Jan 7, 2020

Alright, right on.

slow84lx · Jan 12, 2020

Foxslider said:
I'll have to see what MAF this is. It looks like Ford never made a MAF that was for 24#. I think im giong to buy some rebuilt one's off ebay i see, $80. Id spend $60 at least getting these cleaned. And they're probably making it run rich.

Ford made several 24# applications. `93-'98 Lincoln Mark VIII, '93 Cobra, '96-'99 Cobra`s, Lincoln Continentals thru 1999, Lincoln Aviators & Navigators. I'm sure there are others.

24lb injectors vs 19lb on stock 5.0.. Going back to stock..

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