I hate to be that guy, but after weeks straight of what seems like daily phone calls, DMs, emails about this- including 4 today alone- I have to say something about the various Supercharger kits available for this platform, namely the Boosted Tech SC and the inherent (but fixable) problems it has.
I don't go out of my way to throw vendors or their products under the bus- that is not what I am trying to do here...At this point I don't go out of my way to even post at all. I have all but stopped posting in the groups because I got tired of people arguing against fact and first-hand experience. That said, I hope people read what I have to say below. I'm sure someone will get their feelings hurt but I am tired of watching people blow thousands- or more- on bullshit claims or items that are not a "sure thing"
Guys, ladies, it's 2021, STOP buying piggybacks to tune your Jeeps. There is NO reason or incentive to use a device that manipulates PCM inputs and outputs to achieve a desired result. We have had the ability to tune the 96-04 Jeeps (TJ and otherwise) for over a decade now, and 05-06 for almost as long. Why manipulate the PCM into doing something when you can simply....Command it to do something. These Jeeps' computers are not "locked" like many have claimed over the years . Difficult to tune for a novice, yes potentially, but we have done hundreds and hundreds of tunes on the I6 in various applications without issue.
From what I have heard, the issued guidance and documentation that comes with the BT supercharger kit suggests to essentially hang the IAT sensor in the breeze (read, open air). This is dangerous and can lead to engine failure in itself regardless of who or what method of tuning you use.
The IAT is a critical part of the final fueling calculation for all of these Jeeps. Placing it in the cold pipe, or in open air, totally disregards the real-time change in air charge temperature that can only be seen post-supercharger.
In simplest terms, the amount of fuel required changes with changes to intake temperature, in either direction (hotter or colder).If the IAT is not able to see that, the fueling (air fuel ratio) will not be consistent because the aircharge temp model will not be relative to what the motor sees. If that is difficult to understand - understand this, there is a discrepancy between sensed and actual intake temp, and not only will that lead to inconsistent performance, but potentially engine damage.
These engines also do not have knock sensors- they do however use the IAT to pull (or add) timing based on its reading. The IAT could very well be the last line of defense against spark knock- and keeping it in open air totally bypasses that measure.
To add insult to injury- there is no really convenient method to place said IAT. The last one I did, we ended up putting a fitting in the intake manifold which obviously created some additional labor.
If you run a forced induction kit of any kind- ANY BRAND- a wideband O2 is an absolute must. I cannot begin to tell you how many calls I've received about poor drivability/performance , and in asking basic questions, discover the end user has no idea or no awareness of the importance of a air/fuel ratio gauge , let alone what their air/fuel was. Even in using the map sensors, injectors, and using a known good tune etc , my base tunes tend to be about +/-10% from where they need to be as a finished product. There is no such thing as a "one-and-done" tune for these.
Now, some will tout the benefits of using a 7th injector setup as a form of crude chemical intercooling, which will lower intake temps. And it is true that spraying fuel in the blower or intake tract will provide as much. However, using it as a primary means of fueling control is ill-advised. To BT SC owners, I strongly recommend ditching the split second piggyback and using water-meth injection. This will provide the same benefits as the SS+7th injector, only with greater efficiency, and without the drivability quirks inherent to using a piggyback controller. This also requires no harness modification as it can operate totally independent of the PCM/harness in the vehicle.
Some of you will likely say "I only want to run 6 psi, why do I need intercooling of some type?" - the benefits of intercooling are noticeable even at lower boost levels. No modern-day forced induction kit available comes without some form of intercooling, and for good reason.
An M90 supercharger (even when intercooled) is borderline not enough for a 4.0 I6. The MP kit is considerably more efficient, but this is not a "go buy a MP kit" thread. I would absolutely not use a non-intercooled M90 on a stroker or built engine. I'd be hesitant even with intercooling , when turbocharging is arguably cheaper and produces a far better end result.
I know there will be folks that come in here, and tout how good their Jeep drives with a SS/piggyback setup and I'm sure they exist. That said , for every one that does, there are 10 that are unacceptable from a drivability standpoint, let alone performance.
After tuning for 10 years and specializing in these, to me any forced induction build should require the following:
1) proper tuning- either remote tune with a specialist or a very capable tuner with experience with I6
2) colder plugs- I usually use NGK BKR7E .035 gap
3) SRT4 2bar MAP sensor (works up to approx 17-18 psi)
4) Larger injectors- size and injector model will vary depending on year and desired HP level, but about double over stock is a great starting point. We often use Holley 48# on the older I6s that use a jetronic/minitimer connector and Ford Racing 39# or 47# on the newer I6s that use a USCAR injector connector.
4)Wideband O2 with a means of datalogging (datalogging equipment will be dependent on software used). I usually use AEM 30-4110 for remote tuning.
5) Some form of intercooling (air to air, air to water, or chemical)
Again, this post is not intended to bash any vendor, or any product, but rather to bring insight to a topic that is so commonly misunderstood.
Kits like the MP, BT, Banks etc have their place, but really require some planning to utilize them to their best potential.
Regards,
Ryan
Owner/Calibrator/Chef of "the sauce"
FRP
Houston, TX.
