Injector Swap Writeup for the 4.0L

[Talyn]

703 and 784 injectors have exactly the same flow rates - the only difference is the connector type.

They may have the same flow rate, but when put on a rail with different fuel pressure than the 43.5 psi they flow more. Put either on a 49 psi rail and they flow around 24#. Enough for a stroker.

 

[Happytrails]

Just swapped out the Chry/Siemens single hole injectors for the yellow Ford four hole 700 (same as 703) injectors. Fantastic results! Better performance in all range and mode. Fuel economy went from 14.5 to 17-18 mpg. Smoother idle. Better throttle response.
96 XJ Sport 4.0l 4x4. 198000 miles.

BTW, these replacements had no retainer clip slots. No worries. No leak. The clips are there just for engine assy line reasons. They serve no purpose after installation, so long as the fuel rail has full integrity and is properly attached and new proper O rings are installed.

 

[Tony_SS]

Ok, I think this will be my next mod... hard to believe injectors can help gas mileage that much?

 

[dukie564]

the MPG benefit comes from them being clean and with new filters, not from the spray pattern. If your stock ones are clean you won't see a MPG improvement

 

[Happytrails]

the MPG benefit comes from them being clean and with new filters, not from the spray pattern. If your stock ones are clean you won't see a MPG improvement

This is right. Injectors can degrade with time in a number of ways. Clogging, degraded coils, mechanical obstruction, etc. Better spray pattern certainly helps, but is not the magic bullet. I chose these refurbed ones because I had no way of testing or internally cleaning the OEM ones. Worth the $150 to me rather than risk not knowing if the old ones when cleaned were going to work to spec. If someone wants to try saving some bucks, then a good cleaning of the old ones may yield a good result. Road test is a good test!

 

[bugout]

I'm gonna sneak in here and ask a quick question. Is it possible for an novice to clean his injectors? 96XJ w/over 200k on the clock.

 

[Alexia]

I'm gonna sneak in here and ask a quick question. Is it possible for an novice to clean his injectors? 96XJ w/over 200k on the clock.

This guy's video shows how to do it.

 

[dukie564]

^^ This is the exact same setup i use, but with a 9v battery instead of a 12v (plenty to active the solenoid). It takes some practice to balance the spray and the switch but works well.

I soak mine in seafoam for a few days before cleaning them to loosen up gunk inside

Always test the resistance afterwards - for the neon injectors it should be ~12.6 ohms. All injectors should be within 0.2 ohms of each other regardless though.

 

[Alexia]

They may have the same flow rate, but when put on a rail with different fuel pressure than the 43.5 psi they flow more. Put either on a 49 psi rail and they flow around 24#. Enough for a stroker.

The "Enough for a stroker" part is incorrect. Stock injectors flow 233 CC/MIN at 43.5 PSI. Bosch 0-280-155-703 flows 238 CC/MIN at 43.5 PSI. That means they flow 247.8 and 253.11 respectively on a 49.2 PSI fuel system. A stroker putting out around 250 HP needs a minimum of 258 CC/MIN at 43.5 PSI which will flow 274.38 CC/MIN at 49.2 PSI.

 

[Talyn]

Wrong. At 49 psi both the 703s and 784s will flow ~24 lb/hr. Its common knowledge that most strokers are very happy with 24 lb injectors. BTW, those calcs you are using are inaccurate.

 

[bugout]

This guy's video shows how to do it.

Thanks a lot! I appreciate it!

 

[Alexia]

Wrong. At 49 psi both the 703s and 784s will flow ~24 lb/hr. Its common knowledge that most strokers are very happy with 24 lb injectors. BTW, those calcs you are using are inaccurate.

Bosch 0-280-155-715 does not even flow enough with 256 CC/MIN at 43.5 PSI in my stroker. Constant fuel trims of 10% to 12% showing when data logging. I calculated that I need 284 CC/MIN to reach my target. 256 x 1.10 = 281.6 CC/MIN which verifies that both the 703 and the larger 715 injectors are too small.

Please tell me why the calculations are inaccurate? I welcome any corrections to what I have calculated below. The stock injectors have roughly an 11% of extra capacity of what is required. As for a stroker the Bosch 703 flows 238 CC/MIN at 43.5 PSI or less than the calculated 258 CC/MIN at 43.5 PSI(On a 49.3 PSI fuel rail) required for a 250 horsepower application. That means the Bosch 703 injectors would be running at an 87% duty cycle to produce maximum horsepower.

This is a guide I have been working on.

Stock Fuel Injectors
Stock MOPAR 53030778(EV1, 1997-1998 XJ/TJ) flows 233 CC/MIN at 43.5 PSI - http://www.witchhunter.com/flowdatapix/s53030778.jpg (Factory rating, 243 CC/MIN, Examples below will utilize Witch Hunter's data from this injector.)

Other stock injectors for reference.
Stock MOPAR 04854181(EV6, 1999-2001 XJ, 1999-2004 TJ) flows 225 CC/MIN at 43.5 PSI - http://www.witchhunter.com/flowdatapix/s04854181.jpg
Stock MOPAR 53030343(EV1, 1994-1995 XJ) flows 248 CC/MIN at 43.5 PSI - http://www.witchhunter.com/flowdatapix/s53030343.jpg

Required CC/MIN and Safety Margins
The calculated required injector CC/MIN for the 4.0L 190 HP 6 cylinder engine with a Brake Specific Fuel Consumption(BSFC) of 0.5 and a maximum duty cycle of 80% is 209 CC/MIN at 43.5 PSI(196 CC/MIN needed to be put on a 49.2 PSI fuel system). I have found other unverified sources that say the 4.0L has a BSFC of 0.51 which makes a very minor difference in the calculations. For these examples I will be using the standard BSFC of 0.5 for naturally aspirated engines.

Why are over sized 233 CC/MIN at 43.5 PSI(247.8 CC/MIN at 49.2 PSI) injectors used? Chrysler fuel pumps never really put out the ideal 49.2 PSI and usually always come under due to pressure loss. There is a +/- 5 PSI working room built into the fuel system.

With the pump flowing at the lowest specification of 44.2 PSI the stock injectors will push 234.87 CC/MIN. This means the injectors hit about a 70% duty cycle at peak horsepower which is good for stock single hole injectors. This also means the fuel system can suffer a temporary drop in PSI to around 35 PSI without falling below 209 CC/MIN needed to achieve peak horsepower.(The PCM will be unlikely to correct for this and not necessarily run the engine well.)

Duty Cycle
Fuel injectors need head room for efficiency. Going past 80% duty cycle typically means that the injector will begin to have trouble giving accurate fuel delivery. It also increases wear and heat in the injector.

Single Hole versus Four Hole
A single hole injector is like a garden hose. All the liquid comes out of one hole mixed with itself. With a four hole injector the liquid comes out in smaller streams and mixes easier with the surrounding air resulting in better atomization.

What about fuel injectors that are slightly too big?
The PCM will simply throttle the fuel injector pulse width down to achieve the required flow rate.

43.5 PSI
The industry standard is to rate fuel injectors at 3 bar or 43.5 PSI. The calculators on this page can be used to convert PSI ratings and calculate the required flow rate.

EV1 versus EV6 Connectors
1997 to 1998 uses EV1 and 1999+ uses EV6. They can be interchanged by using connector adapters.

Based on the above data and the calculations from observation running these various injectors in stock and stroker engines these are my recommendations.
Upgrades, Stock and Stroker
Stock Engine, 4.0L at 190 HP
EV1 Connector, Lots of head room with these injectors.
Bosch 0-280-155-703 - 238 CC/MIN at 43.5 PSI - http://www.witchhunter.com/flowdatapix/b0280155703.jpg

Small Stroker, 4.5L or around 250 HP
EV1 Connector, Ideal fuel pressure at 49.2 PSI
Bosch 0-280-155-715 - 256 CC/MIN at 43.5 PSI - http://www.witchhunter.com/flowdatapix/b0280155715.jpg

Large Stroker, 4.6L/4.7L or around 275 HP
EV6 Connector, Ideal fuel pressure at 49.2 PSI
Bosch 0-280-156-048 - 285 CC/MIN at 43.5 PSI (Sorry, no image source on this one. FiveoMotorsport and others confirm these numbers.)

 

[Talyn]

Please tell me why the calculations are inaccurate? I welcome any corrections to what I have calculated below. The stock injectors have roughly an 11% of extra capacity of what is required. As for a stroker the Bosch 703 flows 238 CC/MIN at 43.5 PSI or less than the calculated 258 CC/MIN at 43.5 PSI(On a 49.3 PSI fuel rail) required for a 250 horsepower application. That means the Bosch 703 injectors would be running at an 87% duty cycle to produce maximum horsepower.

It doesn't work that way in the real world. You can do all the calculations you want and they might work for your stroker. Using the common calculators a stroker putting out 270hp would need a 28 lb/hr injector... no. But the majority of us, the 24lb injector is a good fit. Just because yours might need 26lb injectors, the majority do not. Many 97+ strokers with the 49psi rail the 703 and 784. I have gone through 7 sets of injectors and between 7 different strokers the 703, 784, and 53032704AB all played the best.

Why are over sized 233 CC/MIN at 43.5 PSI(247.8 CC/MIN at 49.2 PSI) injectors used? Chrysler fuel pumps never really put out the ideal 49.2 PSI and usually always come under due to pressure loss. There is a +/- 5 PSI working room built into the fuel system.

Yah, no. They didn't use "oversized" injectors because the fuel pressure may drop low. Most Chrysler fuel pumps I have tested in vehicles come are +/- 2 psi, pretty decent. Unless they are on the way out. Why use what you are calling an oversized injector? Because that is either what the bean counters could get that day or what the engineers programmed the PCM to work with them. Their specs are based off what the fuel pump would be ideally putting out, 49psi.

Single Hole versus Four Hole
A single hole injector is like a garden hose. All the liquid comes out of one hole mixed with itself. With a four hole injector the liquid comes out in smaller streams and mixes easier with the surrounding air resulting in better atomization.

The fuel stream is hitting the back of a hot intake valve. How will that not atomize the fuel? The atomization theory via smaller holes is blown out or proportion. The only time there will be an advantage is during a cold start. If there was so much advantage to the 4 holes as everyone claims there is then why did Jeep never switch to them even in the last years of the 4.0L?

Based on the above data and the calculations from observation running these various injectors in stock and stroker engines these are my recommendations.
Upgrades, Stock and Stroker
Stock Engine, 4.0L at 190 HP
EV1 Connector, Lots of head room with these injectors.
Bosch 0-280-155-703 - 238 CC/MIN at 43.5 PSI - http://www.witchhunter.com/flowdatapix/b0280155703.jpg

Small Stroker, 4.5L or around 250 HP
EV1 Connector, Ideal fuel pressure at 49.2 PSI
Bosch 0-280-155-715 - 256 CC/MIN at 43.5 PSI - http://www.witchhunter.com/flowdatapix/b0280155715.jpg

Large Stroker, 4.6L/4.7L or around 275 HP
EV6 Connector, Ideal fuel pressure at 49.2 PSI
Bosch 0-280-156-048 - 285 CC/MIN at 43.5 PSI (Sorry, no image source on this one. FiveoMotorsport and others confirm these numbers.)

Fiveo hasn't confirmed shit. They are just selling a product they think might work.

I have already beat this horse to death why the 703 and 784 are poor choices for a 49 psi rail stock engine. The 703 is a good choice for earlier years with the 39psi rail though. And that 280156048 is not a good choice for a stroker any how. I and several other have ran that or an injector that puts out similar flow and its too large. Might work best when in the 5.0L range. Your write up also give no thought to different pressures nor that 99+ uses smaller injectors that 96-98. None of what I have found or said is based on some goofy internet calculator but rather experimentation and testing with several different jeeps and strokers. [/quote]

 

[Alexia]

Yah, no. They didn't use "oversized" injectors because the fuel pressure may drop low. Most Chrysler fuel pumps I have tested in vehicles come are +/- 2 psi, pretty decent. Unless they are on the way out. Why use what you are calling an oversized injector? Because that is either what the bean counters could get that day or what the engineers programmed the PCM to work with them. Their specs are based off what the fuel pump would be ideally putting out, 49psi.

They are also used the same MOPAR 53030778 on the 5.2L and 5.9L Magnum engines which mate up decently well for injector sizing.

The fuel stream is hitting the back of a hot intake valve. How will that not atomize the fuel? The atomization theory via smaller holes is blown out or proportion. The only time there will be an advantage is during a cold start. If there was so much advantage to the 4 holes as everyone claims there is then why did Jeep never switch to them even in the last years of the 4.0L?

Some visual on the atomization patterns. The atomization ideal is to have to mixed up with the air as it enters the valve and not as it splashes off the sides of the intake runner.
http://www.youtube.com/watch?v=bHf-6ohkgbA

Why would they not switch? It costs more for the better designed injectors and they already had a bunch laying around. Even if they did not have a bunch laying around there probably would have been the supply chain in place to get those existing injectors quickly.

Fiveo hasn't confirmed shit. They are just selling a product they think might work.

http://www.fiveomotorsport.com/27lb-ev6-jeep-stroker-0280156048
http://eectuning.org/forums/viewtopic.php?p=54357
http://www.dragtimes.com/parts/GENU...1,4,6,8-OEM-1W7Z9F593AA-46L_261151334982.html
http://www.924board.org/viewtopic.php?p=334180&sid=efbcd5b99f992e8427b9d0906b493591#334180 (267 CC/MIN at 2.7 bar/39.1 PSI is 281 CC/MIN at 43.5 PSI.)

I have already beat this horse to death why the 703 and 784 are poor choices for a 49 psi rail stock engine. The 703 is a good choice for earlier years with the 39psi rail though. And that 280156048 is not a good choice for a stroker any how. I and several other have ran that or an injector that puts out similar flow and its too large. Might work best when in the 5.0L range. Your write up also give no thought to different pressures nor that 99+ uses smaller injectors that 96-98. None of what I have found or said is based on some goofy internet calculator but rather experimentation and testing with several different jeeps and strokers.

If you have beat it to death, where are your math and calculations? I would like to see your work, please.

Yes, for a stock engine the 703 works fine for old and new fuel rails.

I did my calculations based on the MOPAR 53030778 injector purely for comparison purposes and also stuck with 1997+ also for comparison. However, I kept the figures in 43.5 PSI/3 bar for comparison of the advertised and tested ratings of the injectors. Those figures can be then easily converted and compared against a 39 PSI fuel rail.

I too am testing these out on my stock and modified engines.

 

[Talyn]

They are also used the same MOPAR 53030778 on the 5.2L and 5.9L Magnum engines which mate up decently well for injector sizing.

Their is your answer. It has nothing to do with the fuel pump not meeting the 49 psi spec. Bean counters.

Some visual on the atomization patterns. The atomization ideal is to have to mixed up with the air as it enters the valve and not as it splashes off the sides of the intake runner.

And this mimics what is going on inside a running engine how? If anything the 4 hole has a wider pattern and has more of a chance to splash off the sides of the intake port (not runner) as well the valve guide and stem.

Why would they not switch? It costs more for the better designed injectors and they already had a bunch laying around. Even if they did not have a bunch laying around there probably would have been the supply chain in place to get those existing injectors quickly.

Except in 05-06 they did change the injector as well as the fuel pressure. Still a single hole injector. So, if they changed the injector, why not go to a 4 hole if it is better?

http://www.fiveomotorsport.com/27lb-...ker-0280156048
http://eectuning.org/forums/viewtopic.php?p=54357
http://www.dragtimes.com/parts/GENUI...151334982.html
http://www.924board.org/viewtopic.ph...b493591#334180 (267 CC/MIN at 2.7 bar/39.1 PSI is 281 CC/MIN at 43.5 PSI.)

So? they flow 27 lb, which I already knew. Congrats.

If you have beat it to death, where are your math and calculations? I would like to see your work, please.

As I said those calculators are inaccurate. I rather observe the effects of the injectors in a running engine, which I have. The findings and number have been previously posted, so you can go search for them.

Yes, for a stock engine the 703 works fine for old and new fuel rails.

Again, wrong. Putting a 24 lb injector in where a 22lb injector is just hack.

 

[Alexia]

Talyn, all you are doing is saying, "I'm right, you're wrong, nananana," while putting your fingers in your ears. I was looking for constructive criticism and actual corrections. I have checked my math against real world numbers and testing several times which I will stick with.

 

[Talyn]

That nice. I really don't care about your "math".

 

[GearGrabber]

Great info. and write up. I have a 91. Picked up 8 of the 784's yesterday. Guess I'll head back to the wrecking yard and get the 703's. Sounds easier than switching the plug out.

 

[GearGrabber]

You forgot to mention the step to paint the injector retention clips red!!!

Fresh paint on the fuel rail, and red paint on the clips ? Wow, I feel right at home here. arty:

 

[Truckedup]

And a fresh coat of black paint on the injector rail.....I'm swapping the stock one hole injectors for the 4 hole Bosh units as we speak on my 99.The engine ran perfect,the old injector tips look like new.....Will report if the new 4 hole make any difference...