bpas328xi

I have a 4wd AW4 sitting in the back yard, a WJ 242 sitting in the garage, and a D30 in Project: Keepin it Clean that will be coming out of it soon. So, I have everything to convert racejeep lol.

SilverHaze

Why not do a 4.7 stroker since you are already boring it 60 over?

CobraMarty

BecauseRaceJeep...
And because everyone builds a stroker and no one builds a 4.0.

We want to run the stock injectors and ecu tune. The head flow is poor for the 4.0 and even worse for a 4.6L stroker.

A stroker requires bigger injectors and a ecu tune which is about $1000. We feel that the stock tune is best as programmed from the factory.

bpas328xi

Because..... I can just run more boost to get the same gains as a 4.7 stroker. Lol

SilverHaze

When you just add boost you dont have to modify the tune or need larger than stock injectors? How much boost is the racejeep running? I want to build a 4.7 and boost it in the future.

CobraMarty

We leave the stock 6 injectors and stock ECU tune to run the Jeep when not in boost, cold start, cruising, etc. We then use an additional '7th' injector and it's own controller to add fuel and retard timing only when in boost.

Many will argue against this additional injector strategy to fuel under boost, but on these old, low tech jeeps, it works quite well. No need to re-tune the non-boost running when using larger injectors. And it is all smog and OBD2 legal as it doesn't change the stock injectors or ecu tune.

RaceJeep 6 pounds with the M62.
'Thor' 10-11 pounds with Sprintex SC.

With the new forged 4.1L fully built engine going into RaceJeep, and adding a M90 SC, we expect 12-18 pounds boost.

SilverHaze

Does the 7th injector shoot in gas or methanol?

Is it using the split second tune?

CobraMarty

The 7th injector acts like it's own stand alone fuel system.

It 'T's into the fuel line, injects gas into the supercharger, is controlled by the Split Second controller. This controller is fully programmable and controls the 7th injector to come on only during boost and it also controls timing retard under boost. The Split Second FTC1 is an additional injector controller and is tunable. It is not a tune for the stock ECU.

We also use another system by coolingmist.com to inject methanol also while under boost. We actually inject 'blue' window washer fluid which contains 5% methanol.

XJTony22

Awesome Build, quick question for ya ive read through the thread but i'm not sure if i missed it somewhere but what rear end are you running? is it still the stock open diff with 3.07 gears? Or did you swap in a locker or limited slip of some sort. I have a 98 2 door se 5 speed Im going to build into something very similar to this build. This build actually inspired me to buy a 2 door 2wd xj lol
Thanks in advance,
Tony

bpas328xi

I have an AW4 automatic, so I should have 3.55 gears. Trutrac LSD was added and I kept the stock gears that were in the axle. It's a Chrysler 8.25 axle. With the smaller tires, it effectively acts like a XJ on stock size tires would if it had around 4.10 gears. Jumps out of the hole in a hurry lol

And nice!! The 2wd on racejeep might not last a whole lot longer... AWD is so much faster and more controllable, so an AWD swap is most likely in the near future. Have all the parts to do the swap lol

XJTony22

Sweet, another thing thats in the works is some type of forced induction, how do you like the split second controller? How much adjusting from the base tune did you have to do to get to where you are now? I was looking at that and then the AEM piggy back as a cheaper option. I guess ill have to check out a junk yard for a Cherokee that came with a LSD, from what Ive read its the models that had the towing package and no ABS, shouldn't be to hard right? lol
Thanks again

Photojared

I assume you guys tuned this 7th injector with a wideband O2? Cause relying on 1 injector with fuel to reach all 6 cylinders doesn't seem very reliable. Not worried about detonation on one or two cylinders?

Same reason a direct port nitrous system is better than a single wet jet.

bpas328xi

I haven't touched the base tune in racejeep at all. It's a very safe tune that ships with the kits. Toyed with the idea of copying the tune off of Project: Keepin it Clean and putting it into Racejeep, but never got around to it. The tune I made for Thor is just less conservative on the timing. I built Thor's boost tune from the ground up using a wideband.

AEM may be cheaper, but the method of tuning is annoying. You tune the 7th injector with a percentage that varies based on the pulsing of the stock injectors.... Really screwy way of doing it. The Split Second is tuned by adjusting what injector pulse width you want at what boost level. The SS is extremely easy to tune.

And most XJs I've seen equipped with a LSD had the d35. Idk much past that because I never did the research. The Detroit TruTrac is a much better LSD because it uses helical gears instead of clutches and doesn't wear out. The TruTrac also locks up to 100% while still being very mild on the street. No chirping on the tires, no clunking of the diff, and no quirky handling characteristics.

Yup. I did all my homework and did everything correctly and used a wideband. However, the m62 kit comes tuned and ready to run out of the box.

The 7th injector sits on the inlet side of the supercharger. NOT the boost side. The SS box pulses it 6 times per engine cycle (2 revolutions). The supercharger homogenizes the fuel with the air. I have no concerns about the fuel distribution.

My other XJ (lifted, supercharged, and running about double the boost of the m62 kit) still has the 7th injector setup (albeit a larger 80# injector). It has been my ultra reliable daily driver for about 35-40,000 boosted miles. The engine and supercharger have been the most reliable things on that Jeep. Already on my second suspension system, second set of shocks, second set of tires, new rear axle shaft seals, and 3rd set of brake pads (2nd set were pepboys brand... Never again). If that doesn't say that a supercharged 4.0 with the 7th injector setup is reliable, idk what does.... Lol


And a single fogger of nitrous works all the time. A lot of carbureted engines use a fogger plate which is pretty darn similar to a single fogger too. A direct port fogger system also works well. There are so many ways to skin a cat and they're usually all correct. A lot of the time, it boils down to ease of installation and cost. A direct port nitrous kit will always cost more than a single fogger kit and will be harder to install. I don't really think that either method is "better"... Just different. Both methods get the same result, MORE POWER. Lol.

XJTony22

Okay that's worth it for me the ease of tuning, I'll probably buy it before I go F/I so I can get a feel for how to tune it. The hunt begins finding a limited slip lol

bpas328xi

Got a purdy new driveshaft for Racejeep. Carbon fiber awesomeness. 6.8lbs. Rated for like 1700hp max.