Turbo Jeep Cherokee XJ-R Build

What exactly is the F/IC, an injector controller?

gradon said:

I got the F/IC6 o2 offset voltage to work in my 96 XJ with both a 6Kohm and a 10Kohm resistor. The PCM overrode the 1Kohm that the AEM instructions called for.

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Good to know. Which resistor gave the best result?

bjoehandley said:

What exactly is the F/IC, an injector controller?

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Fuel/Ignition Controller.

The F/IC is used to manage the installation of, typically, higher capacity fuel injectors. In operation, the Jeeps PCM no longer fires the injectors, it fires across a set of resistors in the F/IC. The F/IC uses this signal to control the physical injectors by looking in the FUEL table what it is you would like the injector to be doing.

At installation, the AEM F/IC wants to know what injectors were removed and what injectors were installed. By answering this one question, a basic fuel table is developed that brings the level of operation of the new injectors back to stock.

From this starting point, you adjust the fuel flow across the table based upon data from an Air Fuel Ratio gauge.

The "I" portion of F/IC is ignition retard. Primarily for boost applications, you must retard the spark under positive pressure to prevent detonation. Personally, I use hardware from Phormula for knock detection.

A side note here. The AEM F/IC gives you choices on how to program the fuel management, I use the "percent" mode as I find it the easiest to manage. Just read the error, do the math and apply the correction to the table.

I use the F/IC8 as it has additional features (speedometer correction and accelerator pump emulation) that the F/IC6 is lacking. Costs more though...

Hope this helped answer your question.

I think the 10k dropped the stoich target too much. I think the ticket is between a 4.7K and 6.2K.

This intercooler solution works for me. I had no problems mounting to the front...I just hate that it is currently unprotected...like I'm out with no rubber on.





Curious...what size injectors did you go to? I'm running 550cc injectors on the 3.0L and upgraded my fuel pump to a Walbro. You haven't needed any of this?

I like your intercooler setup. I wanted to try something like that but my teammates didn’t want to cut up the front bumper we made and had the same concern about it not being protected. I had another mocked up to go in front of the radiator and behind the grill but we would have had to cut the lower radiator support to run the tubes down next to the steering box. Also the radiator mounts would have had to be pushed back toward the engine. Still they didn’t want to cut things up too much so we went with the DSM one as a quick solution. So far it’s been ok at our power levels and we don’t really run more then 7 psi. If things get hot water injection is still an option.

Injectors are 36 lbs but we do have the fuel pressure regulator crushed to get about 50-55 psi. Still running the stock pump too. Pretty much we are stuck at our current power levels unless we upgrade a bunch of stuff.

Finally got the Jeep out to an autocross this season with the BMWCCA. Dave had the 10th fastest time out of 106 drivers in the Jeep behind a 2007 Porsche GT3 RS, engine swapped and boosted 07 Lotus Exige S, a bunch of fully prep'd M3s, a 1,000lb kit race car, and a 2012 Mustang Boss 302 to name a few. Dave had a few faster runs but they were not clean. He was also 6 seconds faster then my 135i. We had 2 or 3 Go-Pros mounted on the Jeep so as soon as we go though the footage I'll post it up

Results from OneHotLap.com




XJ-R next to Dave's E30 M3

I spent some time digging though a shock book trying to find some shorter ones for the front. Right now we only have 2” of travel before they bottom out. Besides being shorter I was trying to find some from a vehicle that had a similar spring rate as well. It looks like a set from a GM G-Body should work since they use a 346-420 lbs spring. Currently we are running 370 lbs. Below are some of the other Monroe shocks I found that will fit. I mainly used their book so I could find an application and cross reference them to some Bilstein’s.

I'm gonna have to source new front shocks(hopefully Bilstein), when I chop the center section so I can go 2" lower in the front. I'm currently using the BE5-6140-T5s in the front and the BE5-A827-T5s in the rear:

Finally looking into upgrading the intercooler to a front mount and running 2.5” charge pipes. I want it to stay hidden behind the grill to keep the front end clean looking. The only place for the pipes to run is though the lower core support behind the bumper and under the radiator. Other then the steering box it looks like I should have enough space. Pretty sure I’m going to have to move the radiator back ½” - ¾”

Space I have to work with from the top of the radiator to the header panel before moving anything.

And the bottom

Using the edge of the radiator as a reference point you can see how far over the steering box is

First mock up of a 18x11x3 intercooler with cardboard on my Comanche.

Here is a 30x11x3 which it too big since the steering box would be in the way and it would block more of the radiator. The window box that the only one I could find that was close and its 3.5” wide unlike the intercooler I’m trying to mimic.

At least it fits behind the grill

You can see how the radiator would need to be moved back. If I trimmed the header panel I could gain some space back for the fan just to be safe. The XJ-R is running 2 electric fans so that would not be a problem.

After all the measuring I ordered a 24x11x3 intercooler on ebay which looks something like this:

that's an awful lot of radiator to be covering - i'd be worried about engine cooling more than charge air cooling

dukie564 said:

that's an awful lot of radiator to be covering - i'd be worried about engine cooling more than charge air cooling

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the AC condensor covers the entire radiator and gets just as hot, it should be fine.

keep up the good work, get everything you can out of it. Interested to see how far you can go with this.

:thumbup:

I am interested to see what, if any, engine cooling problems develop as well. I have 3 fan electric setup that doesn't keep up too well at highway speeds and my IC isn't in front of the radiator. That would only make my setup worse. I actually want to go to the mechanical clutch fan and then get a thin 2" core that will fit in front of the OEM setup without moving the radiator. 2" thick core will fit fine, yes?

a/c condenser also isn't 3" thick

interested to see how it turns out though

There are turbo diesel XJs in europe that have a smaller intercooler mounted below the radiator... They are located (google for a picture) in a poor spot because of the lack of ventilation behind the bumper, but could be changed around some. I might do this on my diesel cherokee swap eventually.

But, your intercooler looks like a better option.

Intercooler showed up yesterday so I removed the top radiator support and dropped it in. Currently it’s upside down because the inlets didn’t allow me to check depth since they were in the way. Surprisingly it fits a lot better then I expected. The intercooler mounts are actually the same height as the rubber radiator mounts. This should make install a lot easier. There are a few spots where it contacts the header panel but with a little trimming I should be able to minimize how far back the top of the radiator will need to me moved. So far the bottom is in the stock location.

Found some fuel pressure regulators that should interchange with the stock one and increase pressure.

Standard Motor Products Part #'s

PR210 39 psi (stock)
PR211 50 psi
PR209 55 psi
PR321 58 psi

Intercooler is in. We had to relocated the radiator back about a ½” top and bottom but everything fits with room to spare. Still need to go back and enlarge the openings for the charge pipes so nothing rubs. Grill fits with no modifications too.