4.0L Head and EFI swap

[eaglefreek]

Your project has me interested... I wanted to get some numbers down on mine so bad, and I was just a week or two away from doing it. MAKE SURE you get teh right size injectors the first time, should be no less than 24lbs/hr. I think I may have toasted the ring in the one I sold from a super lean condition at some point in time. Take it to a mechanic with a OBDI capable scan tool and have them check your fuel trim once it's running.  I'm very interested in the numbers...

Just curious how you came up with the 24lb. injectors number? Just like the original poster, I have the 4.0 head swap with a Comp Cams camshaft. A friend of mine who is well versed in EFI told me the stock Jeep injectors should be fine based on his calculations. Also you were running E85 do you think that may have something to do with your lean condition?

Carguy I figured out how I'm going to trigger my MS. The Motorcraft distributor uses a VR sensor and I will use that to trigger through my MSD ignition. It won't be as accurate a trigger with a 36-1 wheel on the crank using EDIS, but since these engines don't rev to high it shouldn't be a problem.

[carguy87]

Wow, work is still crazy, 6 days a week and on Sundays all the house work.  I calculated at least 27lb/hr injectors for my buildup.  If you used a stock block, that could be the reason, but I had to bore my 4.2L block .030" over to get good fit between the pistons and the cylinders, I also put an open filter style intake on which will deliver much more air paired with the 92' 4.0L camshaft.  I am going with a set of EV6 injectors with the old EV1 style electrical hookup, they provide a much more efficient spray pattern and are more of a variable rate injector, meaning I can play with my fuel pressure to lean out or beef up the mixture and not run into stumbling or driveability issues.  I like your idea of the motorcraft distributor for the trigger, but as I have mentioned, I am going to do away with that inaccurate power robbing dinosaur as soon as I can.  If you would like, I can put a link here that will explaine to you how to calculate what size injectors you need, it is worded much better than anything I can do, lol.  Curious, what did you do for your kickdown?  Did you remember to change to a cooler sparkplug over stockers?

[eaglefreek]

I'd like to see the link for injector sizing.

[tougeagle]

http://www.jeep4.0performance.4mg.com/tech_specs.html

Navigate and read all specs on this page for all parts, EXTREMELY helpful information.

[tougeagle]

Your project has me interested... I wanted to get some numbers down on mine so bad, and I was just a week or two away from doing it. MAKE SURE you get teh right size injectors the first time, should be no less than 24lbs/hr. I think I may have toasted the ring in the one I sold from a super lean condition at some point in time. Take it to a mechanic with a OBDI capable scan tool and have them check your fuel trim once it's running.  I'm very interested in the numbers...

Just curious how you came up with the 24lb. injectors number? Just like the original poster, I have the 4.0 head swap with a Comp Cams camshaft. A friend of mine who is well versed in EFI told me the stock Jeep injectors should be fine based on his calculations. Also you were running E85 do you think that may have something to do with your lean condition?

Carguy I figured out how I'm going to trigger my MS. The Motorcraft distributor uses a VR sensor and I will use that to trigger through my MSD ignition. It won't be as accurate a trigger with a 36-1 wheel on the crank using EDIS, but since these engines don't rev to high it shouldn't be a problem.

My engine was bored to .030 over, and a stock 4.2 is larger than a 4.0 to begin with. Stock jeep injectors (at least, the most common ones) are around 19-21 lbs/hr for 4.0s. In addition. E85 requires an AFR of around 10:1 vs 14.7:1 for gas. 24s are the smallest you can use, without dangerously increasing the injector duty cycle which can cause premature failure. There are a few very well known efi swap builds in which the authors stress that stock injectors will not work. A 24lb injector can push up to 30 lbs with increased fuel pressure. Mine are rated at 24lb/hr at 39.5 psi, and they are the plastic bodied design III with EVI connectors.

[carguy87]

http://www.fordracingparts.com/download/charts/Fuel_Injectors_and_Adaptors.pdf
This is a great link to explain everything properly.  Stock injectors for our 91-95 HO 4.0's actually run 23.6lb/hr at 3bar or 43.5psi.  And my compression is more than high enough as I had my head machined .010" to true and the block had to be machined as well.  Problem with E85 is if you go with cheap components, they don't hold up properly and can be pitted because of the fuel.  Most machine shops will recommend using chromoly ring sets when planning on running E85.

[carguy87]

And I would highly recommend switching to an EV6 style injector or disc style, over the pintle style EV1's that come stock on the Jeep's.  Those pintle style are not as adaptable to changes in fuel pressure and can become erratic in operation and cause premature failure if too much fuel pressure is used, and lower fuel pressure can cause a poor spray wich will cause stumbling and stuttering of the engine.  On top, the EV6's have a much better spray pattern which cause fuel atomization for a better fuel/air mixture, the EV1 style tend to shoot a stream like you'd expect from a squirt gun.

[eaglefreek]

Thanks for the links. I purchased 19lb EV6 injectors already. I think they'll do just fine for my application. I've got an adjustable fuel pressure regulator so I can make some adjustments if necessary.

[tougeagle]

Thanks for the links. I purchased 19lb EV6 injectors already. I think they'll do just fine for my application. I've got an adjustable fuel pressure regulator so I can make some adjustments if necessary.

Pay close attention to your burn tips by keeping track of your spark plug ends. To be completely honest 19lbs is probably gonna be slim. That's what I started off with on mine and it was noticibly laggy...

[eaglefreek]

Thanks for the links. I purchased 19lb EV6 injectors already. I think they'll do just fine for my application. I've got an adjustable fuel pressure regulator so I can make some adjustments if necessary.

Pay close attention to your burn tips by keeping track of your spark plug ends. To be completely honest 19lbs is probably gonna be slim. That's what I started off with on mine and it was noticibly laggy...

Is that with gasoline or E85?

[tougeagle]

Thanks for the links. I purchased 19lb EV6 injectors already. I think they'll do just fine for my application. I've got an adjustable fuel pressure regulator so I can make some adjustments if necessary.

Pay close attention to your burn tips by keeping track of your spark plug ends. To be completely honest 19lbs is probably gonna be slim. That's what I started off with on mine and it was noticibly laggy...

Is that with gasoline or E85?

With gas. I turned the fuel pressure up to 55 PSI with E85, so I was around 29lb/hr on cornohol. Should be 24lb/hr on gas, no less. when I checked fuel trim with engine running, it was still trying to correct 1.6%

[68AMXGOPAC]

Hmmmm so seems I will have to adjust that for the gas - no cornhol here in NY scenerio........ ?or at least none nearby that I know of.We feed our corn to the cows : ) where it belongs.

[carguy87]

Finally got my 30lb./hr. fuel injectors in the mail and installed them Friday, what a difference, I was able to set the timing back properly and lower my fuel pressure and it runs amazingly.  They are a couple pounds higher than what my engine requires, but that will keep from pushing them too hard and leave room for a turbo install at a later date. Now just to get to someone with a pipe bender to finish the last half of the exhaust and this Eagle will be one high flyer again.

[captspillane]

This discussion has been very helpful. I was about to purchase new injectors for mine. I was planning on one size larger than stock, which would be 24 lbs instead of 21 lbs. I'll be getting the 30 lb injectors instead. My engine is a 4.2 short block bored .060 over. Thanks!

[carguy87]

Haha, no problem, I hope you learned and calculated the proper size for your build.  You might want to consider getting a higher voltage coil for yours to help reduce ignition problems. BTW stock for 91-95 HO are roughly 23.8lb./hr. so 24 would hardly help.  My ride is soo much smoother and much easier getting up to speed now.  Now to just do some tweaks to squeeze all the mpg's out of this sucker, lol.