1998 Jeep Cherokee with 4.7L stroker - First read seems to be missing a lot?

[PRS]

My wife's '98 Jeep Cherokee has a 4.7L stroker, inline 6. Had it tuned many years ago to account for the displacement and cam change, but it was tuned for high octane fuel back then and now I want to dial that back to run on uncle Tom's cabin 5'er jugs. Saw HPT has supported the Jeep ECM for a bit, so I spent the $50 on 1 credit today and downloaded the tune that was in there.

I was expecting a lot less functionality in this Jeep ECM, having 99% of my experience with Gen 3 LS tunes, but holy cow - it seems like it's missing everything important. Can't seem to be able to verify or edit any hard parameters, like different size injectors. Can't dial in or adjust VE/fueling from what I can tell under the Airflow tab (no factory MAF on these rigs so I'm assuming it runs on speed density?). There's no controlling of the transmission shift points from what I can tell. There's no updating/correcting the tire or gear ratio, which you'd think is an important aspect for the Jeep community (but I admit most of us just swap out the gear in the transfer case tail housing).

Am I missing something in my HPT version or something? Or is the Jeep just really limited in HPT?

MODS any input?Jeep First Read 8.14.2022.hpt

[PRS]

Bumping this for assistance.

[sarg]

Following. I wonder if it is just an ECU they have not mapped yet?

[PRS]

I'm hoping they have considering it's on their supported vehicles list and they charge credits for it.

[sarg]

Often times if you send them the scan they can help.

[PRS]

I've been in contact with Eric from Support. Haven't reached any conclusions yet, but while we wait - here are some Jeep stroker questions for the general population:

Mind you - I have 99% of my experience with tuning LS-swapped cars and trucks and buggies, so my mind knows HPT for the LS side of the house, which is why I'm probably asking noob questions here as this Jeep PCM is totally different than what I'm used to.

1. How do you properly tune for different injectors than stock on this PCM? Under Engine>Fuel>General there seems to only be a handful of Injector related parameters to change.
2. How do you properly tune for increased displacement in the way of bigger bore and stroke? There's no VE table here, nor MAF, or anything really related to telling the PCM how much airflow it should be seeing.
3. I wasn't aware the '98 Cherokees had any EGR, but there are spark tables based on Main Spark (EGR off) and (EGR on). Assuming I'm correct and there's no EGR, does it just always use the Main Spark (EGR Off?)
4. Has anyone successfully found a way to tune the Jeep AW4 transmission shift points?

[sarg]

Quite honestly, I am not sure if this is as advanced an ECU or if they just do not have the parameters mapped out yet due to lack of interest.

For the injectors it does not seem to have any kind of scaling, just the offsets. Is it not yet mapped or is it just not there as the factory did not allow for any other sized injector? I do wonder if you could play with the voltage tables to make it do what you needed to. Seems a crude way of approaching it, but thus far in my ecu I am not really seeing any other options other than input the correct voltages and then tune to base fuel table to pull out whatever fuel you needed with a global reduction for larger injectors. I come from the LS world as well as some import stuff, so this is just thoughts. In one import I did we just did a global reduction on the base fuel table as there was not ability to scale for injector size. It worked out well though.

From what I have seen so far looking through it, the VE table that I have seen is that EGR off base fuel pulsewidth. It is MAP vs RPM which is in effect the VE table. Adjusting the targets will be the power enrichment. So if you forced open loop operation and logged the fuel or used closed loop monitoring fuel trims you should be able to get a good base map by adjusting the Base fuel table. If you have no EGR then I would tend to make them both match. Although, I wonder if one could use this to flip a switch somewhere for alternative fuels? Mine does show shift points for full throttle but the shift schedule seems very basic. I honestly have no clue how these transmissions determine when they shift at part throttle. This is not a MAF based vehicle. Think of it as if you were tuning Speed Density on a LS platform if you have ever done that. It is just RPM Vs MAP value to find the proper position to add or reduce fuel.

Hope this helps. This is just my take away after looking at it.

[MTcamaroguy]

Following as I am in the exact same situation with no additional information.
Will post if I learn anything.

[grimmechanic]

The JTEC ECU used on Mopars from 1995-2004 is very simple. JTEC controllers do not have auto trans functions. Auto transmissions are controlled by a separate controller that's not accessible/re-programmable. The JTEC programming is similar to early Ford EEC-IV ECU's. They just use O2 sensor feedback for closed loop operation and very basic injector PW tables. No provisions for MAF. Just manifold pressure, throttle position, cam position, crank position, O2, IAT, and coolant sensors. They're very easy to tune if you've had any exposure to late 1980's FI systems. I was happy as hell when HP started supporting these. And pleasantly surprised at how simple they are. There is no EGR on the 4.0 engine. I don't know if the 5.2, 5.9, or V-10 use EGR. Control of the injectors is strictly by pulse width. Adjust based on WB data logging.

The Jeep XJ trans controller sucks and it's a bummer there's no one that makes programmers that can access these.

Early 4.0 stroker tuners didn't even touch the ECU programming on the early Renix FI systems. They just swapped to 24lb injectors and used adjustable fuel pressure regulators. This tuning method carried over to the JTEC controllers for many years because no one offered support for reprogramming these either.

I have a 2006 Wrangler with the 4.0 and it uses the NSG3 ECU/TCU and it is a different animal. A lot like what most people are familiar with now with VE tables. But, still no trans controller access even though it's integrated into the NSG3. Trans control access wasn't enabled until the NSG3 CAN and NSG4 in 2006/2007.

Speedo calibration on the XJ/TJ is done with a gear swap on the extension housing (except for '06 Rubicon). Quadretech has a cheat sheet with axle ratios and tire sizes that tell you what size gear to use. It wasn't until 2007 that Wranglers had the speedo cal in the ECU. Grand Cherokees and some other Mopars in the early 2000's obtained the speedo signal from the ABS controller. Calibration on these JTEC/ABS vehicles is done through the TCM.

[t-man22]

Hey PRS?I was given https://frptuning.com/ info from Russ Pottenger who supplied me with my 4.7 stroker parts and knowledge. He said Ryan at FRP is the man for tuning our strokers. He also mentioned that 91 octane was now a requirement (at least for my build). Anyway, I?ve had emails with Ryan and since you have the correct model tuner device, he can help you out if you need him. I?m almost done putting the peripherals back on mine and getting close using his services.

See ya, t-man22

My wife's '98 Jeep Cherokee has a 4.7L stroker, inline 6. Had it tuned many years ago to account for the displacement and cam change, but it was tuned for high octane fuel back then and now I want to dial that back to run on uncle Tom's cabin 5'er jugs. Saw HPT has supported the Jeep ECM for a bit, so I spent the $50 on 1 credit today and downloaded the tune that was in there.

I was expecting a lot less functionality in this Jeep ECM, having 99% of my experience with Gen 3 LS tunes, but holy cow - it seems like it's missing everything important. Can't seem to be able to verify or edit any hard parameters, like different size injectors. Can't dial in or adjust VE/fueling from what I can tell under the Airflow tab (no factory MAF on these rigs so I'm assuming it runs on speed density?). There's no controlling of the transmission shift points from what I can tell. There's no updating/correcting the tire or gear ratio, which you'd think is an important aspect for the Jeep community (but I admit most of us just swap out the gear in the transfer case tail housing).

Am I missing something in my HPT version or something? Or is the Jeep just really limited in HPT?

MODS any input?Jeep First Read 8.14.2022.hpt

[Coopasnoop]

Early 4.0 stroker tuners didn't even touch the ECU programming on the early Renix FI systems. They just swapped to 24lb injectors and used adjustable fuel pressure regulators. This tuning method carried over to the JTEC controllers for many years because no one offered support for reprogramming these either.

-So your saying that this method would work under a low boost operation turbo as well?