HELP WITH INJECTORS

[qualm]

I need to find some injectors for my Stroker.

I have a 1999 4.0 Cherokee.

This is what is going inside:

KB 944 psitons
Stock Rods
68-232-4 CAM
Mopar Performance Valve springs, retainers and locks
SCAT 258 Crank

Everything else will basically be stock '99. No throttle body upgrades or intake upgrades yet.

Since it is a 99 and OBDII will I have to get a piggy back or professional tune?

I was going to use Bosch 0280155865, Ford XR3E-C5B 24 LB Mustang Cobra injectors, but Silverxj said they are too big or Ford/Bosch XR3E A4B but he said these were too small. So now I need some help.

Thanks

[SilverXJ]

I had Jeep 53032704AB injector installed. They are used on the 4.7L engine. Its a 4 hole design and is suppose to flow 25 lbs. They are the best fit yet. A little rich on the top end still, but manageable and no where as bad as the others. I won't say this is gospel, but that was my experience.

A piggy back might help, but I would advise a wideband O2 sensor first. It will tell you where your AFR is and if you need further adjustments.

[qualm]

Thanks for that. I will look into those injectors. Could you point me in the right direction for a wide band O2 censor? I really do not know much about fuel injection at all.

Thanks for your help.

[qualm]

Actually could you explain the wide band o2 sensor some? LOL

[unlimitedrubicon]

A standard 'narrow band' oxygen sensor really only has two outputs -- lean and rich. What a wide-band oxygen sensor does is gives a much more precise readout and by using a guage or scanner you can find out what your exact air/fuel ratio is and make any necessary changes to get the ratio you are looking for depending on load / RPM / etc. To check the 'fit' of your injectors without a wide-band O2 sensor you need to read the PCM's short-term and long-term fuel trims to see if it is constantly adding fuel / removing fuel / or able to compensate correctly as well as 'reading' your spark plugs and then make an educated guess as to how the injectors are doing. Using a wide-band O2 sensor you can map the actual ratio and see if any changes need to be made either by changing injectors (large change necessary), or just some fuel trims / maps (smaller changes) using a piggyback computer / adjustable MAP sensor / adjustable fuel pressure regulator. Each method of making the changes has it's benefits and drawbacks, it all depends on your budget, capabilities, and time.

[qualm]

So I have read some since my last post and came across your "unlimitedrubicon" post about innovate motorsports and the LC-1. I have watched a few videos and am beginning to understand more. So the LC-1 or most wide band O2 sensors offer kits. These kits offer "logging" capabilities correct? It is just a way to see where your fuel mixture is correct? So if I install one of these I would be able to visually see what the mixture is as long as I am recording. How would I go about changing my fuel maps?

[unlimitedrubicon]

That is correct; most will have a kit, for instance I have the LC-1 and OT-2 so I can interface it with my phone or a computer to view / log data from the computer (OBDII) and the wideband O2 sensor. Once you have the data you can compare where the air/fuel ratio is and make the changes and what you use for that will really depend on how far off the ratio is and what your budget / capabilities are. For fine tuning my preference would be a piggy-back computer such as the AEM F/IC6 or a Spit Second PSC or FTC device, again depending on the age of the vehicle, your budget, and your capabilities to get it done in a reasonable time frame. Others on the board here seem to have had good success by adjusting their MAP voltage or fuel pressure. More information on those is available by searching the forum or from the members here that have done it successfully.

[qualm]

A MAP adjuster will not work well with the '01 computer. The reason is that the '00+ computers are locked into a program that provides a stoichiometric 14.7:1 A/F ratio at WOT up to 2300rpm and thereafter goes richer. The only way to dial in an even 13.0:1 A/F ratio across the rpm range at WOT is to install a piggyback computer such as the Unichip and have it mapped on the dyno. An alternative would be the Apexi SAFC 2 but that'll only allow you to alter the fuel curves, whereas the Unichip also allows you to program new timing curves.

I read this a few days ago. So my jeep is a 1999 does this mean that I do not have to worry about my computer being locked into a program that provides stoichiometric 14.7:1 A/F ratio and I can use the Radio Shack MAP Voltage adjuster?

Can anyone verify that it was 2000 when they made the computers do this?

Thanks for all your help.

[Cheromaniac]

Can anyone verify that it was 2000 when they made the computers do this?

They did this on all late 4.0 Jeep models that were fitted with the distributorless ignition system (DIS).