JB4 boost readings still seem low

[Terry@BMS]

Exhaust is always hot. Higher EGT usually increases boost potential because hotter exhaust is denser and provides more force to spin the turbine. It's why traditional wastegate vehicles have "boost creep" during longer runs without measures to reduce WGDC as EGT increases. Modeled EGT is one of the factors we use in our wastegate control on BMW applications.

 

[GRN D3MÖN 22]

The discussion in this thread is intended for modified max power guys so won't apply to someone just running map1 or map2.

So the new boost adjustments will be slighty more power for maps 5-8, But the wastegate control will help stop the oscillation, should help maintain consistent boost on all maps, and possibly add boost to LC right? Any other new features you may wanna tease for v13

 

[Terry@BMS]

EWG control is just another tuning tool in JB4's tool box and we're exploring ways to best implement it. Right now it's going to be most useful for highly modified cars or unique situations like cars that over boost or under boost with downpipes.

Not aware of any oscillation issues on v12 but if you have one email me an example so we can sort that for you. Shouldn't need EWG for that.

 

[Tonkabob]

In my experience it's usually what we call exhaust back pressure. Basically the ratio of pressure in the turbine housing relative to the boost pressure. If it's more than 2:1 then you stop making more power as you continue to raise boost. The "fix" is usually a larger or higher flowing turbine. The correct diagnostic test is to attach a pressure sensor to the turbine and feed that in to the JB4 to log along side boost. I'll see what I can do, requires to drill/tap the exhaust side of the housing which isn't always practical due to turbo placement.

The Burger shop Stinger has full stock exhaust, correct?

 

[Terry@BMS]

Yes

 

[xot1]

Yesterday as I was driving on the highway, I accelerated maybe to half throttle for few seconds and the boost went really high (past 22psi because my boost gauge beeped) and then I had close to zero boost (1.5psi max) regardless of the throttle input or RPM until I restarted the engine. I don't know if this can be called limp mode because the car didn't throw a CEL.

Since it was not full throttle, I have no log of the issue right when it happened but I do have a log of after it happened showing that boost does not come up despite the load.

Any ideas or comments?

 

[Terry@BMS]

Sounds like an over boost fault. Those usually clear when you reset it. You're running a flash in addition to the JB4 if I recall? Maybe part throttle boost is cranked a little high.

 

[xot1]

Sounds like an over boost fault. Those usually clear when you reset it. You're running a flash in addition to the JB4 if I recall? Maybe part throttle boost is cranked a little high.

Only 3 changes have been made to my ECU:
- Downpipe CEL removed
- Speed limit removed
- Torque limit removed (increased)
Nothing regarding throttle, boost, timings, fuel etc.

 

[Terry@BMS]

OK try to capture it on a log. Maybe a good candidate for our ewg control..

 

[xot1]

OK try to capture it on a log. Maybe a good candidate for our ewg control..

I will try to find a way to reproduce the problem.
To be continued.

 

[Tonkabob]

Just push the start logging button.

 

[xot1]

I got one big overboost logged. File is attached.
Just doing a mild acceleration on the highway and boost went up to 26psi. Then almost no boost until I restarted the engine. No error code at all.
Remark: I know timings are very bad. I refilled at a gas station I never went before and I think their octane rating is not good.


EDIT: I'll send an email.

 

[Tonkabob]

I got one big overboost logged. File is attached.
Just doing a mild acceleration on the highway and boost went up to 26psi. Then almost no boost until I restarted the engine. No error code at all.
Remark: I know timings are very bad. I refilled at a gas station I never went before and I think their octane rating is not good.


EDIT: I'll send an email.

Do you have iat spoof turned on? That makes it easier overboost.

 

[xot1]

Do you have iat spoof turned on? That makes it easier overboost.

No. Just Map8 with 70 additive.

 

[Tonkabob]

6th gear 3K rpm is a tough pull. Lots of time to build boost.

When ECU PSI gets over 16 timing is dropping to deal with it but boost still climbing.
JB sees the overboost and drops the target from 6.8 to 0 which causes immediate ecu over boost and limp boost mode.

Why the boost kept climbing, not sure.
Looked like a pretty cold day given the IAT.

 

[Terry@BMS]

Timing is mapped on boost so that checks out.

ECU PSI converged on actual boost as JB4 disabled itself due to the over boost. But generally speaking this is a classic sign of too much WGDC. When more EWG connectors show up we'll get a harness out for you to test. Until then I suggested testing the options.7 on to try to reduce boost requested at 70% throttle input.

 

[xot1]

Ok I will do!

 

[xot1]

I am looking more at the logs. Is it normal that bank1 and bank2 AFRs differ at peak boost? (12.9 vs 11.1) It seems that bank2 is pouring much more fuel. Or does it happens for a too short amount of time to be relevant?

 

[xot1]

Quick update for whoever is following:

Bit7 didn't fix much with the currently available v13 firmware.
The boost increase is indeed a bit smoother but it still peaked super high, past the boost safety value, and because of the low throttle value, it didn't trigger limp mode.
So after few tries Terry got the safety mode logic dialed in for my particular case, so that it does not exceeds the boost safety setting.
Overboost can't be fixed yet without control over the EWG but at least it won't cause any damage until this becomes available.

To be continued...

 

[Brian B]

I do get over-boost issues as well mostly on cold days. 40 F or below. Its as simple as restarting the car and it goes away but it can be annoying especially if it happens on a morning when i do a hard pull onto the highway and then the rest of the highway trip no boost