JB4 difference between Boost and ECU_PSI on data logs. 3.3T

[zombiedude]

Just hooked up my JB4 to my 3.3T and was running some data logs and had some confusion between what ECU_PSI and Boost measured. My map2 log shows a peak of 23.8psi on the “boost” line, but 18.6psi on “ECU_PSI” line.

From what I read, stock, this car gets 16-18psi, is that correct? Would that mean my car is barely over stock psi? It physically feels much faster. Or is that 16-18 relative to the “boost” in which I’m making significantly more.. very confused. All things considered, I’m not trying to get more power, it feels plenty fast, I just want to know what numbers I’m looking at.. When someone here says they made 20psi which are we referring to, and what is “high” for the stock turbos?

 

[Thomby]

You should see 3 columns:
- ECU_PSI is what the car is calling for / what it thinks you're making
- Target is the amount the JB4 adds above it (by reducing the signal sent to the ECU so it holds your wastegates shut longer), and
- Boost is the actual pressure, generally ECU_PSI + Target (but may not add up perfectly during spool)

The ECU targets a load value that depends on ambient conditions, rather than a specific boost limit, but it should be something in the 12-14 psi range. Map 2 should add something like 4psi to that, with total boost around 16-18 psi.

20psi is what you'd see on Map 4-5, running an E30 mix or other high octane fuel. And you should really never be up near 24 psi...I think the default value for the JB4 to kick into safety mode is 22-23 psi.

 

[zombiedude]

You should see 3 columns:
- ECU_PSI is what the car is calling for / what it thinks you're making
- Target is the amount the JB4 adds above it (by reducing the signal sent to the ECU so it holds your wastegates shut longer), and
- Boost is the actual pressure, generally ECU_PSI + Target (but may not add up perfectly during spool)

The ECU targets a load value that depends on ambient conditions, rather than a specific boost limit, but it should be something in the 12-14 psi range. Map 2 should add something like 4psi to that, with total boost around 16-18 psi.

20psi is what you'd see on Map 4-5, running an E30 mix or other high octane fuel. And you should really never be up near 24 psi...I think the default value for the JB4 to kick into safety mode is 22-23 psi.

I talked with Terry and he said to pay attention to the ECU PSI value which in my case (18.6psi) was right in the map 2 range of 18 (+/- 1psi), just wanted to make sure the 24psi I was seeing wasn’t my turbos about to grenade themselves lol.

 

[Thomby]

I talked with Terry and he said to pay attention to the ECU PSI value which in my case (18.6psi) was right in the map 2 range of 18 (+/- 1psi)

Oh I see now, you're not running the JB4 as a piggyback, you have a Back End Flash which means the ECU itself is calling for the total boost (which would otherwise be ECU + Target). And the 24 psi as momentary at throttle close is much less worrisome than under load.

So I assume during your open throttle pulls, your "Target" column is all zeroes and your "Boost" column basically matches ECU_PSI? That is, you aren't inadvertently having a JB4 piggyback map stack on top of the BEF?

 

[oddball]

Depending on WHICH BEF you're running, it may be a problem.
There's a BEF that is specifically for running with a JB4, so you run the JB4 maps on top of the BEF.
OR, you may have a BEF that's designed to run on its own without a JB4, in which case, yes, you're shooting for the moon.

 

[zombiedude]

Oh I see now, you're not running the JB4 as a piggyback, you have a Back End Flash which means the ECU itself is calling for the total boost (which would otherwise be ECU + Target). And the 24 psi as momentary at throttle close is much less worrisome than under load.

So I assume during your open throttle pulls, your "Target" column is all zeroes and your "Boost" column basically matches ECU_PSI? That is, you aren't inadvertently having a JB4 piggyback map stack on top of the BEF?

No, this is just JB4 map2 no BEF. I was going to do the EK1 but no current support for 2025 models yet. Now I’m definitely confused..

For reference, the car feels good. But not like a missile. Doesn’t feel like a 50%+ increase in boost and reading numbers off others posts, 18-20psi seems to be right in the range for map2 but of course that’s assuming we’re going off the ECU_PSI. I’ll just drop my data log in here to review since you probably know what to look at.

See timestamp 1822 for the peak “boost” reading @ 23.8psi. 18.6 ECU_PSI and 5.0 Target. Why would Terry not find concern with this? I specifically asked what about the 23.8psi if that was a concern and he said the response I attached above.

 

[zombiedude]

Depending on WHICH BEF you're running, it may be a problem.
There's a BEF that is specifically for running with a JB4, so you run the JB4 maps on top of the BEF.
OR, you may have a BEF that's designed to run on its own without a JB4, in which case, yes, you're shooting for the moon.

Not looking to be an astronaut with this car just yet. I prefer my cylinders and turbos on sea level and not low orbit haha. I’m just confused why Terry is giving me the OK. From what I heard, he’s THE MAN who knows what to look for on these cars. To reiterate what I replied to Thomby, no BEF is on the car, just JB4 on Map2. I see 4 boost lines; Boost (highest number), Target (lowest number presumably added amount of requested boost), ECU_PSI, and Boost2 which is very close to ECU_PSI in most cases.

 

[Thomby]

No, this is just JB4 map2 no BEF

I saw the BEF reference in your email, and combined it with the 18psi ECU you mentioned.

See timestamp 1822 for the peak “boost” reading @ 23.8psi. 18.6 ECU_PSI and 5.0 Target. Why would Terry not find concern with this?

That log is a manual one of you cruising around at minimal throttle. The single line you're referencing is when you blipped the throttle for a couple hundred RPM and then got off it, so it really doesn't tell us anything.

It looks like the ECU is seeing 12-14psi with the JB4 targeting another 4-5, which is normal, but again you don't have an actual pull in there. Just floor it from say 20-30mph to 70-80mph (ie WOT through the rev range of a couple gears to let us see boost build and timing advance) and let the automatic logging do its thing. Off-throttle rows are just filler.

 

[zombiedude]

I saw the BEF reference in your email, and combined it with the 18psi ECU you mentioned.


That log is a manual one of you cruising around at minimal throttle. The single line you're referencing is when you blipped the throttle for a couple hundred RPM and then got off it, so it really doesn't tell us anything.

It looks like the ECU is seeing 12-14psi with the JB4 targeting another 4-5, which is normal, but again you don't have an actual pull in there. Just floor it from say 20-30mph to 70-80mph (ie WOT through the rev range of a couple gears to let us see boost build and timing advance) and let the automatic logging do its thing. Off-throttle rows are just filler.

Oh Yeah! I didn't even make that connection on the email, my bad. I was inquiring about using the JB4 BEF on an EK1 and he let me know before buying it, to reach out to the EK team. They let me know 2025 wasn't supported, so that didn't really go anywhere.

As for the data line, that makes sense. I was actually just reviewing the logs at work on my Excel spreadsheets (much easier to read then on a phone) and saw I had actually let off just before then and was pretty much cruising at that point checking the speed and RPM. Looking at my other real pulls I was hitting the right PSI as you mentioned. phhhewww I really was starting to panic there.

How does the automatic logging work? Do I just leave the app connected and open and any large boost build up it'll start tracking?

On that note, I definitely do see much more consistency at 16-18psi when under load which is good. Looping back to my original question, what do these cars normally see stock? I was under the impression it was 16psi, but given thats close to what im pulling now, and it feels much faster, I assume is closer to 12-14psi similar/same to the pre-target number? is it genuinely just the pre-target number, as if I was MAP 0 then it just wouldn't target any additional boost? maybe im overthinking it.

As always, your help is greatly appreciated Thomby and Oddball, you both have helped me a couple times now! I was the guy with the wacky Silicone Turbo Inlet situation too. Need to post an update on that at some point..

 

[zombiedude]

I saw the BEF reference in your email, and combined it with the 18psi ECU you mentioned.


That log is a manual one of you cruising around at minimal throttle. The single line you're referencing is when you blipped the throttle for a couple hundred RPM and then got off it, so it really doesn't tell us anything.

It looks like the ECU is seeing 12-14psi with the JB4 targeting another 4-5, which is normal, but again you don't have an actual pull in there. Just floor it from say 20-30mph to 70-80mph (ie WOT through the rev range of a couple gears to let us see boost build and timing advance) and let the automatic logging do its thing. Off-throttle rows are just filler.

And on an unrelated note, do you know what I should do with this response from EK1. I haven't gotten any info from him, but I guess they can make it work with a "Full Dump Memory Data" of my car. They don't seem to be the most responsive bunch, and the website can be a bit hard to navigate or find a contact to reach out to.

 

[Thomby]

How does the automatic logging work? Do I just leave the app connected and open

It's a pedal/throttle threshold, plus a couple seconds. Connect app, go WOT through a couple gears, let off, and it'll write a log. I think default is 80% and you can change it in the settings, but it shouldn't matter if you're flooring it.

Looping back to my original question, what do these cars normally see stock?

Again it's load based so things like temp and altitude will change it, but generally 12-14psi. I think I've seen 12psi during winter and 14 in the summer. So the 16-18 you mention would make sense for (total) Boost if the JB4 is adding 3-4psi Target to the 12-14 ECU_PSI, but the ECU itself isn't likely to ask for that much.

You can run logs for Map 0, 1, 2 to give yourself a baseline and see how the car behaves as the JB4 ramps up. It's also a good learning process to see how the variables change. Here's a writeup I did with examples:

T

Post in thread 'Wondering if anyone could let me know if I am running at a safe level I have no idea. What my air fuel ratio should be. Please help someone.'

Mar 21, 2023

I’ve had my JB4 for a while now just installing it what a difference it makes I’m only a little concerned that I am not really able to read the logs do you know if I am running in a safe range love how fast it is but I really don’t want to hurt my car

I'm still an amateur at this, but here's BMS's guide, and how I'm learning to look at these:

JB4 Logging Parameters - JB4tech.com - International Turbo Tuning Discussion

Hey guys, We’ll use this thread for details and discussions on Kia specific JB4 logging parameters. Fuel trims and wideband o2 sensor control explained here...

www.jb4tech.com

I start by looking at Pedal, Gear, and MPH (light orange) to get my bearings...

• Thomby

• 

 

[oddball]

Wait, what car do you have?

The Stinger, at least the first few years, usually targeted around 14psi. But there isn't a 2025 Stinger, so........ Kia may have some new base maps. You may be discovering that newer cars are a bit more aggressive, so maybe map 2 becomes too much. You want to watch the timing corrections - corrections of 3 and higher are a bad sign. The turbos will make a chittering sound when they're overloaded.

Too much boost will result in misfires (shows up as timing corrections and/or rough running), pre-ignition (timing corrections) and turbulence in the turbos (chittering noises). Misfire/pre-ignition can destroy parts pretty quickly. the turbo won't blast apart immediately, but repeated abuse can result in physical damage to the blades.

In the app, you can set automatic log options. Yes, the app has to be running and connected. Usually it's throttle greater than X% (use something high, like 90%). JB4 logging is mostly useful when under heavy load like 100% pedal for more than 5 seconds. It is extremely hard to get good log data in a safe and traffic legal manner. One-line blips can usually be ignored.

 

[zombiedude]

It's a pedal/throttle threshold, plus a couple seconds. Connect app, go WOT through a couple gears, let off, and it'll write a log. I think default is 80% and you can change it in the settings, but it shouldn't matter if you're flooring it.

Perfect.

Again it's load based so things like temp and altitude will change it, but generally 12-14psi. I think I've seen 12psi during winter and 14 in the summer. So the 16-18 you mention would make sense for (total) Boost if the JB4 is adding 3-4psi Target to the 12-14 ECU_PSI, but the ECU itself isn't likely to ask for that much.

Oh ok, so that's what you were saying before. Got it! Thank you.

You can run logs for Map 0, 1, 2 to give yourself a baseline and see how the car behaves as the JB4 ramps up. It's also a good learning process to see how the variables change. Here's a writeup I did with examples:

I will definitely give that a thorough read. Always looking to learn more!

 

[zombiedude]

Wait, what car do you have?

The Stinger, at least the first few years, usually targeted around 14psi. But there isn't a 2025 Stinger, so........ Kia may have some new base maps. You may be discovering that newer cars are a bit more aggressive, so maybe map 2 becomes too much. You want to watch the timing corrections - corrections of 3 and higher are a bad sign. The turbos will make a chittering sound when they're overloaded.

Too much boost will result in misfires (shows up as timing corrections and/or rough running), pre-ignition (timing corrections) and turbulence in the turbos (chittering noises). Misfire/pre-ignition can destroy parts pretty quickly. the turbo won't blast apart immediately, but repeated abuse can result in physical damage to the blades.

In the app, you can set automatic log options. Yes, the app has to be running and connected. Usually it's throttle greater than X% (use something high, like 90%). JB4 logging is mostly useful when under heavy load like 100% pedal for more than 5 seconds. It is extremely hard to get good log data in a safe and traffic legal manner. One-line blips can usually be ignored.

2025 Genesis G70 3.3t, I'm posting here, because frankly, more knowledgeable folks here such as yourself and Thomby. I posted a couple times in Genesis Forums and never received a response. The Kia Stinger also tends to have more people driving it, more folks to discuss with. I know 4-5 local stingers in my area, but not a single Genesis unfortunately.

Which line would I be looking at for the timing changes on the data logs? I don't really see any numbers in the lower range unless its "Clock" which fluctuated from 3-9. I don't here any turbo chittering, doesn't feel like its misfiring which is good, but I'd like to know what to keep an eye out for on the logs without bugging the forums every time.

 

[oddball]

ign_1 shows the base timing - the degrees before top dead center that the ECU *wants* to fire the spark. ign_2 through ign_6 show the correction, in degrees of delay, applied for that particular cylinder. (ign_1 might show the corrected time instead of the base time, I'm not sure) e.g. if the ECU is detecting misfires or preignition on cylinder 2 with 20 degrees of timing then it might correct it by "removing" 3 degrees, which means the next cycle will fire at 17 degrees before top dead center - 3 degrees later.
You've got a bunch of goose eggs in 2 through 6 so that's all good. If you run map 2 on 87 octane then you'll start to see 3's and 4's in there. That's the sign to back off.
The JB4 forums are pretty good for info about the JB4 and its logs.

re: ek1 and base data, hopefully that's a function on the ek1 device to dump some chunk of the ECU memory to a file that you can email to ek1. They use that to make certain the memory layout is still the same and set up the modifications.
But if you're seeing the ECU call for 18psi, then unless you're at really high altitude, in which case that's pretty normal. Are you in Denver or something? Air's thin up there, so pressures are higher to get the same mass of air. *Mass* is what matters, not pressure. Pressure is just a way to shove more mass into the cylinder.

 

[zombiedude]

ign_1 shows the base timing - the degrees before top dead center that the ECU *wants* to fire the spark. ign_2 through ign_6 show the correction, in degrees of delay, applied for that particular cylinder. (ign_1 might show the corrected time instead of the base time, I'm not sure) e.g. if the ECU is detecting misfires or preignition on cylinder 2 with 20 degrees of timing then it might correct it by "removing" 3 degrees, which means the next cycle will fire at 17 degrees before top dead center - 3 degrees later.
You've got a bunch of goose eggs in 2 through 6 so that's all good. If you run map 2 on 87 octane then you'll start to see 3's and 4's in there. That's the sign to back off.
The JB4 forums are pretty good for info about the JB4 and its logs.

re: ek1 and base data, hopefully that's a function on the ek1 device to dump some chunk of the ECU memory to a file that you can email to ek1. They use that to make certain the memory layout is still the same and set up the modifications.
But if you're seeing the ECU call for 18psi, then unless you're at really high altitude, in which case that's pretty normal. Are you in Denver or something? Air's thin up there, so pressures are higher to get the same mass of air. *Mass* is what matters, not pressure. Pressure is just a way to shove more mass into the cylinder.

Is there a specific number I should look for in ign_1? I see ign_2-6 are all 0-0.8 with exceptions to the spikes during shifts, so that's good.

ign_1 shows a very high variance, most full "pedal" pulls in the log show between 8.5-15.5, with 17.5-20 while partially on it. I run 92 octane so the timing should be good, just want to understand what "bad timing" would be relative to in terms of my current numbers.

Also the BMS EK1 "Race" tune/flash mentioned targeting ignition advance to around 17 degrees peak, would that mean I should see 17 peak in the ign_1 column during full throttle pulls? This is to be compared to my current 8.5-15.5 numbers, correct?

Thanks on the EK part, hopefully thats the case, would love to get the TCU tune at the very least. As for location, I'm in Oregon at Sea Level. The ECU is only targeting 12-14psi with the JB4 adding 4-5psi in Map 2 for the 18 total, not 18 from the ECU, so no concerns there from what I can tell.

 

[Thomby]

Is there a specific number I should look for in ign_1? I see ign_2-6 are all 0-0.8 with exceptions to the spikes during shifts, so that's good.
ign_1 shows a very high variance, most full "pedal" pulls in the log show between 8.5-15.5, with 17.5-20 while partially on it.

In a modern car timing will be all over the place at light/no throttle, to maximize efficiency. At WOT, advance should increase through the rev range (ignore the plunge during shifts). Sudden drops of 3+ degrees mean knock / octane limit. It's easier to see the trend in Ign1 in graph form, whereas the ign2-6 corrections to base timing are more obvious in the raw table.

You can play around in datazap.me with the axes and variables, but here's a look at absolute timing advance (ign1, purple) and rpm through a couple of gears (light sawtooth line). On this JB4 Map 4 run, timing increases from about 12 to 16 degrees as revs rise -- the big drops are shifts, and the spike is where I let off throttle:

 

[zombiedude]

In a modern car timing will be all over the place at light/no throttle, to maximize efficiency. At WOT, advance should increase through the rev range (ignore the plunge during shifts). Sudden drops of 3+ degrees mean knock / octane limit. It's easier to see the trend in Ign1 in graph form, whereas the ign2-6 corrections to base timing are more obvious in the raw table.

You can play around in datazap.me with the axes and variables, but here's a look at absolute timing advance (ign1, purple) and rpm through a couple of gears (light sawtooth line). On this JB4 Map 4 run, timing increases from about 12 to 16 degrees as revs rise -- the big drops are shifts, and the spike is where I left off throttle:

View attachment 90205

Got it, yet again, you present such a complicated idea in an easily understandable way! So generally I'm looking at ign2-6 on the table for anything greater than 2-3+ degrees drop, ignoring shifts, and looking at the graph for ign_1 for a gradual increase in timing as I accelerate/RPMs increase, until I shift and RMPs drop and repeat.

Would knock show in ign_1 as a drop in timing on the graph while accelerating? and would this show in ign_2-6 simultaneously? Only reason I'm asking is if I'm fine avoiding transferring logs to the graph just to see how ign_1 is doing.

For your example if you were to use the EK1 E85_RACE flash tune, would your 12-16 degrees of timing then increase to 19 peak generating more power? I assume that's how it would work.

 

[oddball]

Timing will be all over the place. Modern cars can play a lot of games with ignition timing to heavily alter the engine's dynamics.
When the tuners talk about changing the timing, they're talking about changing the base timing map in the heavy acceleration area. You can advance timing with higher octane gas, e.g. e30, and get more power out of the power stroke.
It's not worthwhile to stare at ign_1 unless you know what you're looking for. Just look at 2 through 6 for corrections.

The timing pull during shifts is to save the transmission. Timing is the fastest way to change the engine's power output. Crazy, but it's faster/easier to manipulate power output via timing than fuel or air delivery. Reduce the timing real quick and the engine will lower its output pretty significantly. Do that while the transmission is shifting and you'll lessen the amount of forced wear on the clutches and less likely to break hard parts. Bring the timing back up once the shift is done and the power comes right back because the gas and air are already moving. Also makes shifts smoother.

 

[Thomby]

Would knock show in ign_1 as a drop in timing on the graph while accelerating? and would this show in ign_2-6 simultaneously? Only reason I'm asking is if I'm fine avoiding transferring logs to the graph just to see how ign_1 is doing.

Ign1 base timing is pulled from ODBII, while the ign2-6 individual cylinder adjustments are pulled from RAM, so timing is slightly different (you'll see this for some other parameters, like RPM & indicated gear not lining up perfectly around shifts).

I'm not sure how knock in cyl1 translates to an Ign1 adjustment -- I'd expect the car to detect cyl1 knock just like the others, but I don't know if cyl1 timing is locked as base timing (ie can't pull cyl1 timing without pulling everything) or if it can be adjusted independently of 2-6 (maybe a separate cyl1 value in RAM that JB4 just doesn't display). But regardless of logic I'd treat Ign1 timing pulls the same.

Here's BMS' own description:

Ign1-6: Timing advance in the specific cylinder. Generally all cylinders will agree but as you start to approach a limit of Boost for a given fuel quality/octane level then you’ll start to see 3.5 degree timing drops in specific cylinders. The lower the grade fuel the more frequently you’ll see drops. If you see drops in the same cylinder repeating several times in a single gear then it’s usually an indicator that you’d be better off with a lower Target for the given fuel. Note that timing in all cylinders regularly drops negative during shifts and under some other driving conditions so do not confused mapped changes affecting all cylinders with cylinder specific timing drops when evaluating logs. Also note cyl1 is sampled via OBDII while cyl2-6 are sampled via RAM read so there will be some timing differences between the readings due to the different protocols. Cyl 2-6 are not available for all vehicle models. Note with firmware v20+ values 2-6 reflect timing drops rather than raw timing advance per cylinder. Set FUA = 1 to revert back to raw timing if needed. In the new format this shows how many degrees were removed from that specific cylinder. Also note it's normal to see timing drops. If you're trying to tune for zero drops then you'll end up leaving a lot of power on the table.

JB4 Logging Parameters - JB4tech.com - International Turbo Tuning Discussion

Hey guys, We’ll use this thread for details and discussions on Kia specific JB4 logging parameters. Fuel trims and wideband o2 sensor control explained here...

www.jb4tech.com