Power Cut Under Load

[Tom]

I meant to set the overboost protection as 18 instead of the current 15 in the firmware

If it were me, I'd max out the overboost table to start and see if that eliminates the glitch. If it does, you can back it down to something that still preserves some protection. The XDF is designed to display psi, for human readability, but the DME just reads an 8-bit binary number that it compares to an internal load value. In other words, the car won't consistently trigger protection at 18psi. It will trigger it at a load value that may or may not correlate closely to 18psi. With a more efficient turbo, the actual trigger will be lower in general, and maybe lower still on a cold day or up a hill, etc. 18 is 'probably' high enough to avoid overboost protection with your car set to 15psi, but too close for diagnostic purposes. If you set it to 18 and still get a hiccup, you won't really know if 18 is too low or if the cause is something else. If you max out the table, you'll get better diagnostic info. If it hiccups, it was never the overboost protection. If it doesn't hiccup, it was the overboost. More black and white.

[whalenlg]

Updated the DME chip and runs with no issues - only had time for a few 15 psi pulls in 2nd, 3rd and 4th, but no issue with cutting out so far.

[Tom]

Updated the DME chip and runs with no issues - only had time for a few 15 psi pulls in 2nd, 3rd and 4th, but no issue with cutting out so far.

Nice, did you use 18psi or max out the cells?

[whalenlg]

18psi

[danmartinic]

I understand the KLR has a MAP sensor (albiet only 1-bar); it's fed by the clear line from the manifold.

If so, why does the stock system not read actual boost level? How is the stock MAP sensor used?

[Tom]

I understand the KLR has a MAP sensor (albiet only 1-bar); it's fed by the clear line from the manifold.

If so, why does the stock system not read actual boost level? How is the stock MAP sensor used?

@johnb can school us all in the inner workings of the KLR, but I'll take a higher level swing for now.

The KLR and the DME each have their own independent forms of (so-called) overboost protection.

The KLR uses its map sensor to drive the boost gauge, and as part of its boost regulation and overboost functions. When the KLR sees too much boost, it generates error/blink codes and can go into limp (low boost) mode. The KLR controls boost via the cycling valve, which is why you can effectively eliminate the KLR's overboost feature by using an aftermarket boost controller.

The DME has its own form of overboost protection that functions independently of the KLR. The DME monitors total load (air mass) consumed by the motor and shuts off the injectors if load exceeds its overboost thresholds. It's a blunt instrument compared to the KLR's system (i.e., a brick wall) but the one that is more typically triggered on the 951. The DME's overboost thresholds reside in a single map in the DME chip, so it is relatively simple to increase the overboost limits as Whalenlg did, or effectively eliminate them altogether by maxing out the entries in the map.

[johnb]

I understand the KLR has a MAP sensor (albiet only 1-bar); it's fed by the clear line from the manifold.

If so, why does the stock system not read actual boost level? How is the stock MAP sensor used?

@johnb can school us all in the inner workings of the KLR, but I'll take a higher level swing for now.

The KLR and the DME each have their own independent forms of (so-called) overboost protection.

The KLR uses its map sensor to drive the boost gauge, and as part of its boost regulation and overboost functions. When the KLR sees too much boost, it generates error/blink codes and can go into limp (low boost) mode. The KLR controls boost via the cycling valve, which is why you can effectively eliminate the KLR's overboost feature by using an aftermarket boost controller.

The DME has its own form of overboost protection that functions independently of the KLR. The DME monitors total load (air mass) consumed by the motor and shuts off the injectors if load exceeds its overboost thresholds. It's a blunt instrument compared to the KLR's system (i.e., a brick wall) but the one that is more typically triggered on the 951. The DME's overboost thresholds reside in a single map in the DME chip, so it is relatively simple to increase the overboost limits as Whalenlg did, or effectively eliminate them altogether by maxing out the entries in the map.

Exactly, the stock system does read boost, that's how it does closed loop boost control. The DME's overload protection just kicks in sooner. The KLR actually has both over and underboost error detection. As Tom said once you have aftermarket boost control, the KLR can't do anything to reduce boost when it detects these conditions so unless you are deliberately checking for blink codes you'll never even know it was triggered.

[whalenlg]

Looks like I spoke too soon - I did a long full boost pull in 3rd gear and it happened again. I'll try Tom's suggestion to remove the overboost limit and give it another try. My boost gauge does capture max, and it still said 15 psi.

[944m3]

If you are staying with stock DME then I suggest an electronic boost controller. I have your same setup except Tial 38mm wg instead of Lindsey, but same function.

It’s a a night and day difference. The Raptor pumps way more air than stock turbo. I hated when my overboost would cut in just when I was starting to have fun.

I’m using my standalone ebc in openloop. My max boost I’ve set is 200 kpa. From about 110 kpa I’m running 100% duty cycle to top port (on Lindsey wg that would be bottom port but check me on that). At about 170 kpa I start reducing duty cycle and by 200 kpa I’m at 20% duty cycle. It’s so much more fun not having to lift, you can really feel the turbo working. I’m sure I still need fine tuning on a dyno. But for now those basic settings are working well for me. I haven’t tried closed loop yet.

An EBC is investment for sure but not crazy expensive. It would improve your experience with your current setup immensely.

Edit: Just for clarity, I was experiencing the exact issue. I would hit the boost cut in fifth gear on the highway or 2nd gear in a hard pull. I couldn’t get the manual boost controller dialed in and it was annoying. From what I’ve gathered, a dual port wg is really meant to be used with an EBC to get the full advantage. Being able to set your duty cycle depending on configurable variables like map pressure was a game changer for me. Especially with upgraded turbo like the Raptor, which is awesome.

[whalenlg]

Thanks for the suggestion. I don't really want to go beyond the 15 psi I'm at and yes it was a lot of trial and error to get to where I'm at.
Did you remove all boost limits in the DME EPROM and now rely on the EBC prevent overboost?