Jeep Strokers

It seams that there are a few problems with tunning the stroker. I am curious...who has completed running strokers? How many miles? OBDI, or OBDII? Piggyback or stock computer? What fuel injectors?

I have run a stroker and various other 4.0L mods on the OBD II system with out issues. However, I believe that you do need either larger injectors or a MAP adjuster/piggy back of some sort.. I have seen some burnt exhaust valves after a long hill climb with no type of fuel adjustments. The OBD II system is pretty adaptable and I have never had it give me a problem until now, and I still don't know what that is, nor if it is fact the OBD II system. The only problems with the previous strokers is that they were internally flawed, nothing with the OBD II. With my wide band and basic piggy back tuning s pretty easy, and I haven't had a problem with it... aside from me putting a value in the wrong place causing that weird lean condition previous.

I've run the stock fuel injectors with a piggy back and it required more fuel to be added in. I am currently running ford cobra injectors that require fuel to be pulled out. I rather err on the side of rich than lean and I also heard piggy backs work more effectively if they are pulling fuel out instead of adding it.

Silver,
Can we get some details on your Apexi? What exactly does it do and allow? Where'd you get it? How much was it? How do I get one? What is the flow rate of your cobra injectors? Do you have any programming tips? Are all my questions answered in your build thread?

I am having troubles selecting fuel injectors too. I am looking for higher flowing injectors for E85, but I need to know what is "normal" so that I can make my choice. Apparently what I thought was normal is too much.

To the OP: 27lb is too much for a 4.7.

dwg86 wrote:It seams that there are a few problems with tunning the stroker. I am curious...who has completed running strokers? How many miles? OBDI, or OBDII? Piggyback or stock computer? What fuel injectors?

I just dyno'd mine last week with the '01 intake manifold (numbers in sig.).



It's done just over 54k miles (almost 5 years to the day) and it goes like a raped ape. Pulls cleanly from just 750rpm with very strong low/midrange torque and neck-snapping throttle response. Fuel economy's pretty good too.

OBDI stock computer
Ford Racing 24lb injectors
Stock fuel pressure regulator (40psi)
Homebrew MAP adjuster set at 5.20v

Hey Pollo--I wouldn't say 27# is too much for a 4.7, or any stroker for that matter. If you use the fms blue tops (24#@39psi) on an obd2 49psi rail, they're basically 27#(26.9). When I had my psc1 piggyback in the mix I had the injector duty cycle maxed to achieve 12.5:1 afr in 5th wot. My stroker is a 4.6 w/ ported&polished head(so breaths a lil more air), mopar 30ab cam, and the lt1 injectors, which are 25.5#. I would like to give the fms injectors a try someday to compare. Mine is about 13 months old and has 15K. The psc1 is being bench tested by split sec at the moment(blown output). When I get word of the status/options, I'll determine whether to use the psc again or go to a local shop to custom tune a Unichip and get some dyno #s.

PolloLoco wrote:Silver,
Can we get some details on your Apexi? What exactly does it do and allow? Where'd you get it? How much was it? How do I get one? What is the flow rate of your cobra injectors? Do you have any programming tips? Are all my questions answered in your build thread?

http://www.importperformance.com/apexi/ ... tions.html

It is made for imports, but works fine. Basically it is a MAP adjuster with multiple points to adjust. At the time I purchased it the PSC, and SMT (I think that is the other popular one) were both around $500. I got the Apexi for $300. Now that the others have come down in price I would go with the PSC. Programing tips are dependent on the equipment. Here is a good read on tuning with a PSC1 http://www.gadgetonline.com/U-Tune.pdf. The injectors work out to around 26 or so lbs, which is a bit rich, but in open loop (WOT) is when the Apexi comes in to play to reduce the AFR. In closed loop the PCM dials back the injector pulse width to get the AFR where it wants it. As I said if the Apexi had an error and lost its programming I would rather be running rich then lean. Also, when tuning you will want a wideband O2 sensor.. I use one with data logging so I can just floor it and go and then adjust afterward. My method of tuning is a bit illegal. There is a road in front of my apartment that goes to 55mph after a stop light. I use the 55mph road to get a run to map the AFR, although i usually don't go over 70. I then u-turn and might make another run or just cool it down. Then I pull into my parking lot and retrieve the AFR data and make adjustments. I usually only make one loop per day when I am tuning. Its better done on a dyno or a test and tune day at the track.