Supercharged Jeep 4.0 spark map tuning jtec

[Drivinsidewayz86]

hello everyone so I've been messing around with my spark map making small changes here and there to the timing on the top end. I am running 4.0 that has been bored out .030 , Mopar purple 229 cam (.440/.440), 1.7 rockers , shop 505 stage 2 pro-rock head (Ported, polished,2.00/1.60 stainless valves, .580 max lift),Sprintex supercharger kit with 54mm pulley (10psi),1 step colder plugs, ported intake manifold, banks exhaust manifold , 36lb injectors , snow stage 2.5 methanol injection with a 2.5 nozzle on straight m1 ( I have been experimenting with boost juice , speed sauce and m1 mixtures. So, my question is has any modified their spark tables on hp tuner if so do you wish to share some pointers? from what I've gathered the max I've seen people show they have for timing is around 38 degrees. my stock map spikes to 41 than comes back down gradually and it kind of looks like my dyno chart so i was wondering if anyone could show me what i should be doing or provide me with some examples so i can learn for a jeep 4.0 thank you.


ign map stock.jpg
igniton map modified 10 psi.jpg
ign map3.jpg

[LilSick]

your file has not been scaled for boost

car needs to be tuned by someone that knows what they are doing

a dyno would provide a good starting point but final tuning needs to be done at the track

it will also need to be adjusted for weather conditions

why arent you running M5???

[Drivinsidewayz86]

can you explain scaling for boost?, it has already been on the dyno and i have nobody locally that's going to tune this. i have a dyno i can rent to test different maps. Im running m5 because I'm still experimenting with what works best for my setup. I would like to learn to properly tune this myself as i was able to get the fuel map pretty decent. I've already tried paying someone and the first person could tune a jtec because they only knew ls stuff, the second person wants $1800 for a tune. This is a $1000 jeep project im using as a learning experience into tuning so any knowledges or tips you can offer will be greatly appreciated. i ordered a tuner nerd and it showed up faulty so im planning on buying the link knock block.

[LilSick]

can you explain scaling for boost?

look at your Y axis. it is scaled for a naturally aspirated engine. your engine is supercharged. the values should be changed to cover the pressures the engine is capable of producing. you cannot create the timing map that it wants until after that axis has been changed. you cannot create that map without tools either tho. dyno. weather station. track. data.

good luck with your project

[HaasExp]

can you explain scaling for boost?

The load axis on your ignition timing tables is based on the manifold absolute pressure (MAP).
For an n/a engine at sealevel at WOT (assuming no intake restrictions) the MAP should be approximately equal to the barometric pressure of air which will be around 101kPa.
Your MAP axis scaling only goes to 105kPa which is only approximately 0.5psi of boost. This is why it's not scaled correctly for boost.
Yes, it still "works" as the PCM will just ride the ignition timing values from the 105kPa row for any boost pressures above 0.5psi but it's a far from ideal approach.
If you were running upto 10psi boost, then the table should be rescaled so at least the final row is around 170kPa.

If this is how the tuners have setup the ignition timing tables then it also makes you wonder how the rest of the tune has been setup....

[Drivinsidewayz86]

Thank you for the information. As far as the map scaling goes it has a gm 2 bar map sensor. None of the map sensor characteristics or settings have been changed around for the new map sensor. The only available information I've been able to find is that you need to half the map scalar multiple (244) into somewhere around 122, I've found several conflicting answers saying 122 is too low and to set it around 170-190. The testing method was key on engine off and see what the map sensor reads , mine sits at 52.00kpa with key on engine off. If you have any information on properly scaling the map gm 2bar map sensor i would greatly appreciate it as I have my laptop infront of me. And yes I agree with you that this is not a professional tune so you'll have to forgive me this is my first time and I'm still learning, finding reliable information on tuning this ecu has been a long road thank you again for the help

[Drivinsidewayz86]

Here are the current map sensor settings , any help to get this thing dialed in would be greatly appreciated thank you again.

FB_IMG_1732012101995.jpg
FB_IMG_1732012106898.jpg
FB_IMG_1732012111190.jpg

[HaasExp]

The testing method was key on engine off and see what the map sensor reads , mine sits at 52.00kpa with key on engine off.

That is a somewhat valid testing method to at least know if the MAP sensor is reading the barometric (atmospheric) pressure correctly.
Unfortunately, it seems to be wayyy off. If you are at sealevel, it should be reading approx 100kPa.
I don't know the characteristic for that particular AMP sensor nor the specific parameters for the JTEC sorry.

[Drivinsidewayz86]

So from what I was told the jtec ecu requires you to half the tables in order for it to read properly in boost. I have messed around and found someone willing to share their spark map and it's different than mine. I have been told my spark table isn't scaled for a supercharger but as far as what I have to actually do to fix that I still haven't figured out.Screenshot_20241120_192948_PicCollage.jpg

[Stoopalini]

See the left hand column, which goes from 14.8 to 105 over the span of 9 rows? What they are saying is 105 isn't a large enough number to cover positive pressure/boost. So when your boost level goes above say 1/2 psi of pressure, the ECU is stuck using the timing values across the last row.

Lets say you are at 3008 RPM, and at 7 psi of boost. The MAP would be somewhere between 140 - 150 kPa. But since your table only goes up to 105, that 17.5 degrees of spark timing will be used anytime the RPM is 3008 and MAP is 105 or higher.

To fix it, you change the far left column of values (ie: the MAP axis labels) and rescale it for the maximum amount of boost you plan to have. You have to fit the scale within the 9 rows though, as you can't add more rows (or breakpoints) to the table.

Doing this will allow you to adjust the timing for boost, and not have it staying flat for anything above 105.

You change the axis by right clicking, highlight "Row Axis", then click "Edit". In that screen, you can adjust the MAP axis values.

[Drivinsidewayz86]

So what i should be doing is scaling the map axis from 14.8-200 kpa ?so the axis should be labeled 14.8,23.9,31.3,52.7,105,125,150,170,200kpa? So by doing that I would have to rescale the map sensor so it reads over 105kpa as well Or will it read the 200 kpa without messing with the map scale multiple. I know that it currently is set so with the key on engine off the map is reading 53.00kpa would it need to be at 105kpa with the key on engine off ?

[Stoopalini]

Yes, and No.

To determine the top value for scaling the tables which reference Manifold Absolute Pressure (MAP), you need to know the max amount of boost you plan to make.

Atmospheric barometric pressure is typically around 100kPa (ie: 14.5 PSI). So if you plan to run 7 psi of boost, that's an additional 50 or so kPa on top of atmospheric .... which means a maximum MAP reading of 150 kPa with 7 PSI of boost.

Scaling the table to 200 kPa as you are suggesting, would mean you plan to make 14.5 PSI of boost. Is that right?

Scaling it higher than needed won't cause an issue per-se, but you only have 9 rows to work with here. So the higher you go with your scale, the less resolution you will have to dial in the timing. Keeping the scale limited to the max amount of boost you plan to make will give you the most resolution in tweaking the timing at different points.


Now for the MAP sensor itself ... I am not familiar with the JTEC PCM ... does it support multi-bar operation?

For the GPEC2 PCM, which does support multi-bar functionality .... you don't scale the MAP sensor based on boost or any other detail about the build. The MAP sensor characteristic fields are for telling the PCM what sensor you are using, so you enter the proper values based on the specifications of the sensor being used.

A MAP sensor outputs a voltage, which directly relates to the pressure it is measuring. When you enter MAP characterization data into the PCM, you are telling the PCM how to interpret the voltage and convert it to a pressure reading. The MAP characteristic data is not subjective, and doesn't need to be tweaked/tuned .. but should be set based on the specs of the sensor you have.

All of that above is based on my understanding of the GPEC operating system, which does handle 2 (or 3) bar operation. I know some PCMs cannot handle above barometric, and thus folks have to tweak the tune to fit everything into a 1 bar range. If that is the case with a JTEC, then what I typed above for the MAP sensor probably doesn't apply and how to handle it properly is beyond my knowledge.

Someone else will most likely chime in and clarify how the JTEC handles this ...

[Drivinsidewayz86]

The maximum amount of boost im currently seeing is 10-11 psi at redline. The operation systems seems to be the issue here i believe from what I've been told me multiple peolpe that have messed around with the jtec ecu. They don't offer a 2 bar map sensor update and using the 2 bar map sensor and having it read half the map for boost i guess is a way of tricking the ecu to read correctly. So now I'm very confused as what you were saying is making sense but when I data logged my spark advance it shows as it's functioning normally but I could be wrong. I have found on a wrangler forum and I think a forum on here a guy set the map scale so it would see around 50ish kpa key on engine off and idle around 29-35kp , which mine currently does. Il attached a pic of the spark map I logged with the stock map scalar(244) and a 2 bar map sensor when i get home later today

[Stoopalini]

Gotcha ...

A MAP sensor produces a voltage, typically from 0 - 5v, and this voltage relates to a pressure based on the sensor's calibration. So a 1-bar MAP sensor would typically output ~5v with a 14.5psi input (ie: atmospheric baro), while a 2 bar MAP sensor would output ~2.5v with a 14.5psi input and ~5v with a 29psi input (ie: 29psi = 14.5 baro + 14.5 boost).

But if your OS can't handle above 1-bar, then I can understand the approach of installing a 2 bar MAP sensor and then telling the PCM that 5v from the sensor = 14.5psi (because anything above would throw an error) and then setting up the tables which have a reference to MAP with values that account for this shift.

So a 50kPa reading by the PCM equals 100kPa real world pressure, thus your KOEO reading shows something in the 50 range, and your tables would keep the scale to 105, but 105 really equals 210. So when you log and interpret the data coming in, you have to know this shift is built in and translate accordingly.

The approach makes logical sense to me, but I don't have any experience with JTEC and doing this sort of thing, so can't really help

[Drivinsidewayz86]

Thank you for taking the time out to even explain this stuff to me i appreciate it. It's been a struggling trying to figure this ecu out as nobody really messes with them anymore and I really want to learn.

[spoolboy]

You can't change the cells in the manifold pressure axis to anything over 105kpa. It doesn't really matter anyway what number is in the cells. That's only for your brain, not the pcm. You may find yourself having an easier time if you think of those cells simply as map voltage.

[LilSick]

You may find yourself having an easier time if you think of those cells simply as map voltage.

how so?

i gotta know what the map voltage represents to make the timing curve

is it vacuum or boost?

how much?

move (change) the values in between the zero and the 105 to create the breaks you need

then you can start on the table

[Drivinsidewayz86]

tj v12 noz 2.hpli believe what spool boy said is accurate the tables can be modified but doesn't effect the pcm at all. i attached my spark and fuel map with the tune and data log below so you can see what the engine is actually doing, thank you all for the help.

tjv12 spark map.jpgtj v12 fuel map.jpg

[LilSick]

maps or graphs of avg's?

cant have any exhaust leaks whatsoever

i would use lambda cuz who knows what it has for fuel

you need to learn how to use chart vs time and have parameter ID = 4 present

intake manifold absolute pressure

or you can make a graph using maths do to the same thing but its more work and you still end up with averages

[Drivinsidewayz86]

the exhaust has no leaks i actually just checked it over. il hook up the laptop and changed the dlg1 to output lambda does that avg lambda as well? it's a dual bank wideband. i started setting up the chart i attached it below can you confirm that this is how you are asking for me to set it up?

map graph.jpg