I've been posting my stroker build up on the ausjeepoffroad.com forums and have gained a bit of interest. Especially from those that have done it before. They biggest thing that keeps popping up is the fueling question, notably 'overfueling' especially with my chosen 27lb/hr bosch 3 injectors. The link to the thread is here if you are up for a bit of a read: http://www.ausjeepoffroad.com/forum/sho ... ost1107205
One of the chaps chimed in with this post, he went right into detail.
My answer to this is the map adjuster listed on Dino's site, a unichip installation and tune done locally here or even one of these Jaycar Digital Fuel Adjusters http://www.jaycar.com.au/productView.asp?ID=KC5385. It looks quite interesting and cost effective as a simple means to regulate fuel flow. I'll consider all three options if I do run into any problems but honestly i'm quite confident my chosen set-up will run just fine.I did a very similar build (see "Stroker CJ" thread in this section). Same cam, same RR's, similar block profile etc. Main difference is that you're going 0.060" where I left it at 0.030". So I think you'll end up with a 4.7L while mine is 4.6L.
I too followed the formulas exactly and ended up at Bosch 27lb injectors - this is what I started with.
The stroker runs superbly in open-loop. That's when cold, when accelerating and at WOT. Never missed a beat.
In closed-loop it had - and still has - problems getting the adaptive fuel trims (both short and long term, correct. This is because the system tries to nail the 14.7:1 stoichiometric point by "hunting" around the oxygen sensor's lambda value of 0.65V.
The system alternately adds and subtracts a default time interval from the pre-calculated injector pulse width, creating a continuous sequence of long-short-long-short-long-short...etc injector pulse widths. In return, the computer expects to see a string of O2 sensor voltage readings showing hi-lo-hi-lo-hi-lo volts. If it gets a sequence of hi-hi-hi-hi-hi etc O2 sensor readings it determines that the mix is too rich, adjusts the short term adaptive fuel trim and recalculates overall pulse width until it gets it right.
Initially, with my 27lb injectors (and even with a replacement set of 25lb injectors) that "default interval" I described above is too big and results in the delivery of too much fuel. In other words, with bigger injectors and more fuel pressure at the rail, it continually over-controls and the computer can't establish the correct trim settings.
A dealer near where I work put it on an genuine Jeep scanner and the consistent reading was LOW OXYGEN. The effect when driving it in closed loop is that it tends to stumble until you either back off, or nail it to get it accelerating in open loop mode again.
I'm going back to stock injectors, with a slightly elevated fuel pressure setting, in the hope that it is the right compromise.
To make sure I don't lean-out in open loop (cold/accel/WOT) I have build a MAP adjuster so that the PCM believes the incoming air charge is denser.
My setup is OBD1, so I have vacuum-modulated fuel pressure ranging from 34 to 44 psi at the rail, depending on manifold pressure. As you are using OBD2, you will have a constant 49 psi at the rail. The 27lb injectors are going to deliver a metric a*seload of fuel!
Not saying it won't work, but this is where you might end up and I hope my experiences help.
What have been your experiences with this issue and what are your comments and opinions of the above?
Regards,
Mopud