05 Jeep Wrangler Supercharged NGC3

[BlueScapegoat]

I installed a supercharger on my Jeep 4.0 straight 6 a couple months ago, and have been reading continuously and fiddling with the various tuning options and settings since then.

I'm fairly mechanically inclined, and don't always do stuff the easy way if there's something new I can learn about. This is the first time I've done anything with tuning whatsoever.

It's set up with a piggyback Split Second controller that adds fuel through a 7th injector and retard timing in boost. This has always worked fine and is fully programmable.

However, I was fighting with the PCM not going into open loop at the right time and lean part throttle boost operation. Then after learning about and resetting LTFT the jeep started pulling fuel in the low load low rev range when the piggyback wasn't even doing anything and the supercharger wasn't making boost. And still correcting against the added fuel from the piggyback and staying in closed loop. The Split Second is also supposed to have an enrichment in closed loop provision in the software, but I couldn't get it to do anything.

As a short term solution I raised the Closed Loop ECT temp to max and have been driving in open loop. It's great. Runs a bit too rich in spots but overall really good. Now I'm learning more about speed density tuning and this seems like the way I should progress forward, given it's a MAP. It by far seems to be the simplest and cleanest option.

As of right now I have the rear o2 sensors disabled, along with associated DTCs. The cats are gutted, and I'm reading afr with a wideband x-series AEM gauge.

So my questions:

Do I have all this wrong? Are there downsides to running the Jeep like this full time? I'm not concerned about fuel consumption, just want it to run well and not to break something.

Am I wrong that the upstream o2 sensors aren't doing anything in open loop? I can just disable those as well and simply monitor the wideband o2?

It appears I can do most all of the tuning I want to in the VE tables for fueling, and base and WOT spark tables for timing. Correct?

Are there any external variables that might cause me issues? I live in MN so the yearly temp can range from -30f to 90f. It's my understanding the IAT is still fully functioning in open loop, and the pcm adjusts for barometric pressure on startup?

5YRHmhx.jpg

[spoolboy]

It's generally better to run in closed loop when you can for many reasons.

If you have changed the cam drastically, you may find the o2 sensors don't read correctly at low loads due to valve overlap. Running in open loop may be your only alternative if this is the case.

If your engine is basically stock other than a supercharger, you should try to run in closed loop.

I wouldn't mix the split second and pcm tuning myself. I'd remove the additional injector and split second, install and scale 6 larger injectors and tune the pcm.

You have 2 systems that may fight each other right now.

[spoolboy]

You may find lowering the WOT threshold helps with part throttle fuel trims by getting into open loop sooner. Check out some of the boosted tunes in the repositoryto see what I mean.

[BlueScapegoat]

I tried adjusting the WOT TPS value all the way down to under 1 volt and removed all delays and it made no difference to going open loop, it was still way too late and inconsistent. This is an issue I've heard brought up multiple times with the 05 and 06 TJs. Larger injectors have always been an option, but the extra injector setup helps keeps intake temps down, so that's something I've considered as well.

I didn't even know there was a repository, but doing a search for NGC 4.0 wranglers brings up nothing useful. I do have a copy of a turbo tune from a large manufacturer that utilizes larger injectors, however.

Can you elaborate on the many reasons I'd be better in closed loop?

[spoolboy]

Many reasons:

Engine longevity
Fuel consumption
Emissions compliance (if only for your own peace if mind)
Sensor wear
Self diagnosis (codes)

On the first two, some could argue that a good open loop tune is just as good or even better, and I would argue that is correct only in a narrow set of conditions.

We don't pour engine oil down the gutter.

The ecm uses fuel trims to monitor sensors and hardware for malfunctions and to correct for wear.

[BlueScapegoat]

Ok. Just trying to weigh all the pros and cons here. In open loop it runs about 14.2 in cruise as it is, so a bit rich. On the flip side when I run closed loop it trims out to a 15.4, even under moderate acceleration it stays in the low 15s. Seems too lean to me, but I'm new to this. I'd almost think in terms of longevity you'd be better rich than lean although maybe that spread is negligible?

If I were to stay open loop there wouldn't be any sensors to worry about, the narrowband o2s would be providing no value, at least to my understanding.

Do you think heat would be a concern if I were to go to larger injectors instead? No intercooler, and no knock sensor. Somewhere around 8.8:1 compression, running 91 octane. This Jeep is lifted 5" total and turning 37" tires on beadlocks, it's a brick. Under normal acceleration it sees about 3psi in every gear. With a slight headwind at 60 mph it will also hold 3psi. Full throttle maxes about 7.5psi.

I appreciate the advice.

[spoolboy]

Ok. Just trying to weigh all the pros and cons here. In open loop it runs about 14.2 in cruise as it is, so a bit rich. On the flip side when I run closed loop it trims out to a 15.4, even under moderate acceleration it stays in the low 15s. Seems too lean to me, but I'm new to this. I'd almost think in terms of longevity you'd be better rich than lean although maybe that spread is negligible?

If I were to stay open loop there wouldn't be any sensors to worry about, the narrowband o2s would be providing no value, at least to my understanding.

Do you think heat would be a concern if I were to go to larger injectors instead? No intercooler, and no knock sensor. Somewhere around 8.8:1 compression, running 91 octane. This Jeep is lifted 5" total and turning 37" tires on beadlocks, it's a brick. Under normal acceleration it sees about 3psi in every gear. With a slight headwind at 60 mph it will also hold 3psi. Full throttle maxes about 7.5psi.

I appreciate the advice.

Your questions are hard to answer remotely. Does it feel weaker running at at 15.4 compared to 14.2? Is your wideband accurate?

Log your fuel trims in closed loop and see WHY it's trying to drive the AFR lean. If the narrow bands are enabled, it can really only trim to stoich. Which makes me think either your narrow bands or your widebands are not reading accurately.

As far as the minimal amount of additional cooling provided from an additional injector, I'm not sure. I would doubt it is doing much. You can log IAT and find out.

A previous experience (back before ecu tuning was easy to come by):

We were running an FMU on a Neon with a turbo. At part throttle we would make boost and it would cause the fuel trims to try to take away fuel via pulse width to get back to stoich. Then when we'd go full throttle, it would often try to carry the negative fuel trims into open loop. Conversely, when we tried leaning out the FMU at part throttle, it would add fuel trims and drive open loop DC to max making the car super rich. This was how we left it, but it wasn't right.

[BlueScapegoat]

For the most part it feels the same at either 14.2 or 15.4 afr. But in closed loop it bogs when you roll into the throttle at low load low revs and just in general has a somewhat jerky feel to it, in comparison. I never noticed until I started driving it in open loop, and it just feels smoother. Before the supercharger was installed and everything was 100% stock it would usually bog for a second after a gear change (6 speed) and now that's entirely gone. Also maybe worth noting that in stock tune form, the Jeep came with an unequivocal 8.5 second open loop delay.

I don't know why it goes so lean in closed loop. After a couple days of driving the LTFT would show -10%. I don't know how I'd know for a fact that my wideband is working properly. It's a new LSU4.9 feeding to an AEM X-Series gauge. With it both in resistor trim and free air calibration modes it shows the same afr.

The 03-05 NGC Neons have the exact same problems that everybody has with the 05-06 NGC Jeeps from what I've read. Erratic transition from open to closed loop, and seemingly no correlation between TPS WOT settings and when it actually switches. There seems to be an underlying formula that as far as I know nobody has cracked. My Jeep does carry closed loop fuel trims into open loop, I've verified it. But by resetting the PCM and never letting it get to closed loop it runs off the programmed tables, and in general runs better, than it does in closed loop. And of course without it reading the o2 sensors in open loop it doesn't fight the Split Second either.

[6YhNuJm@]

I have a 2005 Jeep Wrangler with a stock 4.0l and manual transmission and just installed a magnum supercharger. I also purchased the hp mpv12+ With 2 credits. Does anyone know where I can get a basic tune? Any help would be greatly appreciated.

[samgm2]

I have a 2005 Jeep Wrangler with a stock 4.0l and manual transmission and just installed a magnum supercharger. I also purchased the hp mpv12+ With 2 credits. Does anyone know where I can get a basic tune? Any help would be greatly appreciated.

I'm currently tuning my daughter's 2001 Wrangler with a stock 4.0l and automatic transmission. It is turbocharged. I don't think you are going to find a "basic tune." I don't know what that would mean since there is so much that can affect this. For me, I installed a 2 Bar dodge neon sensor and scaled and set the multiplier so that the ECM would see 105KPa at about 8 PSI of boost (which is going to be the maximum for me).

This also means that my ambient starting pressure (engine not running) shows up at about 9PSI. So I had to adjust the minimum barometric pressure appropriately.

From there, I am simply adjusting the base fuel trim in order to get numbers from 0-5 in both long and short-term trim. I would be happy to give you mine once I'm done but you would have to install the dodge 2 Bar sensor. I am also not sure what effect of the turbo impeller obstruction will do vs your supercharger setup. But I suppose it might serve as a starting point.

I have a question for either of you. Is there a command for resetting the fuel trims on a Jeep ECM?

I agree that open-loop control is a bad idea. Running rich is a bad idea. It will cause cylinder wash to take place which will pollute your oil, reduce its lubricity and reduce the life of your engine. Moreover, while running very slightly rich will give you a performance bump, running too rich will reduce performance by slowing the flame front excessively. Allowing the ECM to compensate for the environment is a better and safer alternative.

[jjnnf5]

Hello All,
New to the thread. I have recently purchased HP MVPI3 to use with my 1999 Jeep Wrangler 4.0 turbo charged and intercooler. I have increased injector size to 24lb injectors. Until now have ran stock with Enricher and wideband. I will need help with a base tune if possible. I am willing to add a Dodge 2bar MAP sensor if that will help my situation. (What vehicles can I find Dodhe 2bar MAP sensor on?) Any advice and help is greatly appreciated.

[jjnnf5]

Any chance you could send me your most recent tune? I am new to tuning and would love a head start. I'd be honored