Flow Rate Injector Offset.JPG
What unit is this parameter in? and what does it reference?
TIA
Flow Rate Injector Offset.JPG
What unit is this parameter in? and what does it reference?
TIA
i would also like to know
Is it in CC's perhaps?
Dodge Dakota R/T 383 Turbo T56 Magnum
It should be a unit of time.
If in doubt, multiply everything by 1.1.
I always though it was milliseconds.
what vehicle is this?
I have a good question because I'm new to the tuning world.
What is injector offset?
not sure why is at zero, but my jeep 4.0 tune and most of the 4.0 with jtec up to 1999 ive notice is at zero, maybe someone can help on explain what is about
These old PCMs are tuned by entering injector pulsewidth directly instead of them using VE or NN and making calculations based on FAR like the newer stuff does.
It is possible that the offset is simply included in the table instead of being applied as an adder.
Also here for answers, as I'm going to be learning how to tune using the few jtec vehicles I have, first. All are 99-04 WJ w/4.7 V8, but 4.0 info is somewhat helpful anyways.
Ok guys I figured it out! Under flow rate it says injector control- flow rate- injector offset- 492.0, that value is the fuel pressure with the decimal in the wrong place as my 97 2.5l tj has a fuel pressure spec of 49.2psi. BAM! there's the answer!!!!
I also learned how to adjust injector scaling quite simply. The
first step is to set up a hysterogram that matches the egr off main fuel table, map in kpa vs rpm with the 3rd value being lambda. first disable closed loop next start scanning and filling your hysterogram you have created at idle and then cruse and WOT. Next you are going to want to get your cruse and WOT averages and calculate the differences between actual and desired afr and add that to the injector offset value of 492.0 If the value is higher richer than desired or subtract that value if it is lower leaner by a percentage. Eg... if you measure .80 lambda but you are shooting for .90 lambda you would multiply 492.0 x 1.10 which would give you a new injector flow of 541.2. that should bring down your afr averages at cruse and WOT.
The next step is modifying the voltage offsets. they will affect idle the most so you are going to basically do the same thing using the hysterogram you made in the first step but this time you are going to select the whole voltage offset chart and add or subtract the difference between desired lambda at idle and actual lambda from the voltage table.
After reflashing the ecu drive it and re check your hysterogram it should now be closer to what the factory injectors were. this may need to be done a couple times as flow and voltage offsets affect each other. this will work if you are just looking to re map for different injectors and the rest of the power train is close to stock and in good working order.
With jeep tj's a common modification is to change from the factory 1 hole injectors to 4 hole injectors using bosch 703's or 715's. the 703's flow a few cc's less and the 715's flow a few cc's more so using the method i described should get you very close to what the ecu calculates for the stock injectors.
If this helps anyone let me know.
Last edited by beserkr; 04-02-2021 at 09:38 AM.
Thank you for the info. However there a few things I am unsure about ( admittedly probably because im a novice tuner)
1) Where are you seeing the 492. value you speak of? my injector offset has a range of 0 to 262.140 ??
2) are you referring to the fuel- general- offset- "Bat Volt Correction" table?
3) its been a long time since ive made a histogram table but I realize this is more of a generic HP Tuners type questions so I will try to figure out this on my own.
Thanks you any input you can provide. Ive only ever tuned a GM LS engine and as everyone knows theres a ton of info making it easy. Theres just sooooo little info for these old JTEC PCM's
current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..
LS6 swapped Porsche 944
No body has any answers?
So basically how are you setting up Lambda in HP tuners when you have a Jeep JTEC PCM that your Scanner is linked to? I dont see any Lambda or AFR error channels to add..? The only option I can figure is to do a narrow band LTFT part throttle tune. Yes I do have a WB O2 but I can only log the AFR. What am I missing here? I see lots of vid on You Tube explaining how to set up a AFR error Histogram but again, its not coming up when I search the channels list in my VCM scanner..?
current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..
LS6 swapped Porsche 944
Yea Im very confused, all the experienced (albeit GM tuners because everyone is very tight lipped in the Dodge world) explain how to tune but nothing they are saying or posting in there how to video's match what I am seeing as possible in my VCM scanner..?
Check out this new thread I just posted regarding this.
https://forum.hptuners.com/showthrea...411#post649411
current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..
LS6 swapped Porsche 944
I may be misunderstanding but I think I can help you log lambda with your Wide band afr. Under math parameters go to math user and select a user math 1, select new EQ ratio (sensor) which gives you lambda. I know I am not explaining very well and it may not be what you are asking for. Goat rope garage does a great job of explaining. Just goggle "using serial port to log Wide band goat rope garage". showing a screen shot below of how I set up, my formula is calculating % error and plotting histogram so I can use it to multiple to the fuel tables. Let me know if this is what you are looking for and I will explain with more detail.
Capture.PNG
I am with you on being confused most of the time, very little help on JTEC. I could be wrong but the histogram described above is similar to what I use to dial in the fuel tables but not injectors? But again new to the dodge tuning.