4krpm loss of IDC under boost

SoCoNoHa · 01-23-2024, 02:23 AM

I've read tons of threads, haven't seen anyone with this issue. As I pass 4krpm in boost, my IDC cuts to nearly zero for a moment then back to normal. If i pass 4k in vacuum, there is no issue, it's only with positive manifold pressure.

It's blowing my mind because the ecu shouldn't have a clue whether I'm in boost or not. I have a greddy emanage ultimate in a 97 LGT, stock ecu. I have tried a couple other ecus I have for the EJ25D, they do the same thing, so I'm thinking it's not the ecu but of course it still could be.

For the record, this isn't the emanage cutting IDC, I'm losing the IDC INPUT to the emanage, FROM the ecu. Naturally, since the piggyback is reducing the injector signal to manage larger injectors, if it sees near zero IDC then that's about what it puts out. This happens for as brief a period as my logs can measure. 20ms to go from normal down to nothing, then another 20ms back to normal.

Oddly, it's more severe at partial throttle, less severe at full throttle, but certainly still there, as long as there's at least some boost. I'll try to get a pic of my log posted.

I'm hoping some ecu guru could suggest why the ecu would do that, or perhaps someone with emanage ultimate experience (no694terry?) has seen this before.... Thanks for any and all help.

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benflynn · 01-23-2024, 10:28 AM

Megasquirt friend

that11guy · 02-12-2024, 02:22 PM

Are you maxing out the maf? Sounds like your hitting the limit of something.

SoCoNoHa · 02-14-2024, 06:01 AM

Technically yes, but the ecu shouldn't know that as I have a variable voltage clamp on it. IDc's have just gone to 100 when I've given the ecu max MAF voltage before. I'll set a reminder to post some logs tonight. I'm convinced it's got to do with the closed loop transition, but I have the o2 connected and get no codes for it. I do have injector low voltage codes though. Expected since I'm cutting half the signal or so.

wtdash · 02-20-2024, 03:48 PM

Hi, I have '98 Foz running NA-T, but stock ECU only - no other EM. I know on mine if I run over 7 PSI I get a MAP sensor code (the one by the pass. strut tower).

I fixed that by putting a one-way valve inline w/the MAP so it doesn't 'see' boost (although I now get an EGR code after a few drive cycles).

01-23-2024, 02:23 AM	#1
SoCoNoHa Scooby Newbie Member#: 478524 Join Date: Nov 2017 Chapter/Region: NESIC Location: Southern NH Vehicle: All Any Every	4krpm loss of IDC under boost I've read tons of threads, haven't seen anyone with this issue. As I pass 4krpm in boost, my IDC cuts to nearly zero for a moment then back to normal. If i pass 4k in vacuum, there is no issue, it's only with positive manifold pressure. It's blowing my mind because the ecu shouldn't have a clue whether I'm in boost or not. I have a greddy emanage ultimate in a 97 LGT, stock ecu. I have tried a couple other ecus I have for the EJ25D, they do the same thing, so I'm thinking it's not the ecu but of course it still could be. For the record, this isn't the emanage cutting IDC, I'm losing the IDC INPUT to the emanage, FROM the ecu. Naturally, since the piggyback is reducing the injector signal to manage larger injectors, if it sees near zero IDC then that's about what it puts out. This happens for as brief a period as my logs can measure. 20ms to go from normal down to nothing, then another 20ms back to normal. Oddly, it's more severe at partial throttle, less severe at full throttle, but certainly still there, as long as there's at least some boost. I'll try to get a pic of my log posted. I'm hoping some ecu guru could suggest why the ecu would do that, or perhaps someone with emanage ultimate experience (no694terry?) has seen this before.... Thanks for any and all help. * Registered users of the site do not see these ads.

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01-23-2024, 10:28 AM	#2
benflynn Scooby Specialist Member#: 515308 Join Date: Jun 2020	Megasquirt friend

02-12-2024, 02:22 PM	#3
that11guy Scooby Newbie Member#: 316149 Join Date: Apr 2012 Vehicle: 1998 Legacy Blue	Are you maxing out the maf? Sounds like your hitting the limit of something.

02-14-2024, 06:01 AM	#4
SoCoNoHa Scooby Newbie Member#: 478524 Join Date: Nov 2017 Chapter/Region: NESIC Location: Southern NH Vehicle: All Any Every	Technically yes, but the ecu shouldn't know that as I have a variable voltage clamp on it. IDc's have just gone to 100 when I've given the ecu max MAF voltage before. I'll set a reminder to post some logs tonight. I'm convinced it's got to do with the closed loop transition, but I have the o2 connected and get no codes for it. I do have injector low voltage codes though. Expected since I'm cutting half the signal or so.

02-20-2024, 03:48 PM	#5
wtdash Scooby Specialist Member#: 59182 Join Date: Apr 2004 Location: N. Idaho Vehicle: 2002 WRX GG>> 2016 Focus RS	Hi, I have '98 Foz running NA-T, but stock ECU only - no other EM. I know on mine if I run over 7 PSI I get a MAP sensor code (the one by the pass. strut tower). I fixed that by putting a one-way valve inline w/the MAP so it doesn't 'see' boost (although I now get an EGR code after a few drive cycles).