blackout_ctd

new to the forum and an XJ. im hearing of an injector swap for better throttle response/mileage
what injectors will do this?
how many lbs per hour are the stockers?
any other cheap/free mods i can do to the motor?

baxj89

the 703 neon injector upgrade is the way 2 go the injectors come out of 95-97 neons stratuss and some other models with the 2.4 4cyl the number on the injectors u need is 280155703 find these and u can just swap them out and ur good to go if u have the stock air cleaner box were the top of the box connects to the hose going to the throttle body take the hose loose from the box and there is a restriction in the outlet from the box a screwdriver and some pliers and u can pull it out hook everything back up and ur good 2 go or do away with the box all together and buy a cone filter and just plug the vacccum line that goes into the back of the box and pipe the hose from the fronton the valve cover into the piping from air filter 2 throttle body and u will be good to go u can get a bored outthrottle body from xjfiles on here and that with the injectors will make a big difference hope I didn't confuse u and this helps u some

notop46

I flow tested two stock injectors from my 1990 on a development test bench and they flowed 20.5 lb/hr (based on 30 second flow) with 3.00 bar supply pressure, 100% duty cycle (wide open), with calibrated test fluid (like gasoline, but less flammable). The "spray pattern" was basically a stream. I tested a dozen 703s at the same time with the same conditions. They averaged 24.6 lb/hr. The spray pattern was four smaller streams with better atomization. The two stock injectors had a smaller flow range than the twelve Neon injectors so I know they were running fairly consistent.

The actual flow rating of the injectors is typically 85% of what I measured. If you swap to the Neon injectors you will be able to flow about 20% more fuel than stock. This is a plus if you can pump 20% more air into your engine. If not, or you are more interested in gas mileage, then there is an additional problem with the 703s (and 784s). The dynamic flow rate of the Neon injectors is 50% higher than stock. This means that the amount of fuel that is sprayed for a given injector on pulse is 1.5 times greater. Sure, you can reset your ECU so it “learns” how much fuel to spray for the engine conditions, but it can only do so much. Ever try to get one drop of water out of a faucet? How about a fire hydrant? Good luck. The ECU can only compute the amount of desired on time to so many milliseconds and then it rounds up or down. The injector components can only respond so fast to the signals sent to it. To get fine metering of fuel, you need a low dynamic flow rate.

I found a better set of injectors to use on my Jeep. They use the same connector style as the 784s Neon and stock injectors used in newer model 4.0 liter Cherokees, have the 4 spray holes, and are a generation newer than the 703s/784s. They did require that I change the connectors out, but it was worth it. They flow tested at 21.1 lb/hr (2.7%) higher than stock, with a dynamic flow only 24% higher than stock.

I put them in without resetting the ECU and never looked back. Fuel mileage is as good as stock (I will not quote numbers or improvement % until I have at least 4 tanks of gas on them). The throttle response is definitely improved, and fuel metering is much better. Here is what I consider the best testament to how smoothly these run. Once my Jeep is warmed up and on level ground, I can slip the clutch and slowly shift through all 5 gears without ever touching the gas. 234,000 miles, 4WD, 235/75/15 tires, stock gears, 100 lbs of gear in the back, tank empty or full, 750 RPM idle going 25 MPH without chugging or bucking. Before the swap, it would start chugging in third.

Anyone interested in more details, PM me. Happy weekend!

dukie564

Are you going to share the information or just keep it to yourself ?

notop46

I wanted to let the suspense build a little (actually I forgot). The injrectors are from a 3.7 liter Liberty engine part #0280158021. I have some extra used ones that I would sell. If you want a listing of additional possibilities, send me a PM with an e-mail address and I can fire off the list.

David

freegdr

to much flow can have the oppisite effect more going in gotta have a way to get more out,better flowing exhaust

notop46

Sorry it took so long to follow up on this topic. The last 12 fillups lasted 3400 miles and took 192.4 gallons for 17.67 MPG (best: 19.54 MPG, worst: 16.43 MPG). Prior to the swap, 12 fillups lasted 3424 miles and used 215.1 gallons for 15.92 MPG (best: 16.88 MPG, worst: 14.30 MPG). I'll take a 1.75 MPG improvement anyday. I saved 21 gallons of gas in the timeframe since the swap at $3.15 to $3.75 a gallon. I'm also loving the driveability of the new style injectors.