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Old 01-09-2021, 03:06 PM   #1
Chi_San
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Default Baja hitting boost cut

Stock engine, stock exhaust, stock injectors. Boost is turned up in the low end, running less than stock boost above 3,000 RPM.

At 3500 RPM, in third or fourth gear, never gone that fast in fifth, I will hit boost cut. It's obviously running a little high on the boost. So, I'm trying to fix this, before boost cut breaks my transmission. Honestly, I would rather just disable boost cut, but that doesn't seem to be an option in any way.

I'm going to try backing the wastegate adjuster off a full turn, but if this doesn't work, is there anything else I could do with the tune to keep boost in control better here? Pull timing, maybe drop a few degrees in AVCS? I'm assuming an aftermarket downpipe that would allow the actual wastegate to move air is the real solution, but that's not really in the cards right now.
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Old 01-09-2021, 04:31 PM   #2
jesseisbeast
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Have you tried lowering target boost in the tune? If you're hitting high boost in the low rpm range and trying to back off on the high end, you might need to go external waste gate. It sounds like the waste gate isn't able to relieve enough exhaust because you're already at peak spool at such low rpm. Maybe you should flash the stock tune back on and see if you're still having the issue.
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Old 01-09-2021, 08:19 PM   #3
Chi_San
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Quote:
Originally Posted by jesseisbeast View Post
Have you tried lowering target boost in the tune? If you're hitting high boost in the low rpm range and trying to back off on the high end, you might need to go external waste gate. It sounds like the waste gate isn't able to relieve enough exhaust because you're already at peak spool at such low rpm. Maybe you should flash the stock tune back on and see if you're still having the issue.
The target is for 17PSI at 2,500 RPM, which it hits just fine. At 3,000 RPM, it starts tapering, with an ultimate target of 4 PSI at 6,500 RPM.

The places where I'm hitting boost cut, I'm getting gradual boost creep, and it ONLY happens on steep up hill sections of road. If I'm going downhill, it's no issue.

The point where I'm hitting boost cut, target boost is 6 PSI, but it's creeping up to 8 or so. The stock tune was calling for around 7 PSI, but the peak boost on the stock map was 9 PSI.

If I was asking for 17 PSI of boost where boost cut happens, I would understand. But I'm literally asking for less boost than the stock map, and it's having problems.
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Old 01-09-2021, 09:07 PM   #4
kopele
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Are you talking about fuel cut due to hitting the boost limit? That's the absolute max, so if you're fine at 17psi then your limit is higher than that and wouldn't hit at 8psi. You should also get a CEL if that happens. Can you post a log?
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Old 01-10-2021, 12:59 AM   #5
Chi_San
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Quote:
Originally Posted by kopele View Post
Are you talking about fuel cut due to hitting the boost limit? That's the absolute max, so if you're fine at 17psi then your limit is higher than that and wouldn't hit at 8psi. You should also get a CEL if that happens. Can you post a log?
If the boost target is set to 5 PSI, and you hit 7 PSI, it cuts the fuel by setting injectors to 0%, and it sets a CEL. I tried disabling the CEL, but it still cuts fuel.

So, I did adjust the wastegate arm, and it still overboosts and hits fuel cut, but it takes a lot longer, and only at higher RPM.

I'm going to grab my laptop and charge it tonight, and hopefully tomorrow I can get a log of this. My laptop has been sitting in the closet for the last 3 months, so I'm sure the battery is dead. >_>
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Old 01-10-2021, 12:16 PM   #6
kopele
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Quote:
Originally Posted by Chi_San View Post
If the boost target is set to 5 PSI, and you hit 7 PSI, it cuts the fuel by setting injectors to 0%, and it sets a CEL. I tried disabling the CEL, but it still cuts fuel.

So, I did adjust the wastegate arm, and it still overboosts and hits fuel cut, but it takes a lot longer, and only at higher RPM.

I'm going to grab my laptop and charge it tonight, and hopefully tomorrow I can get a log of this. My laptop has been sitting in the closet for the last 3 months, so I'm sure the battery is dead. >_>

I'm not familiar with the fuel cut you're describing, and I don't see anything in RomRaider that would cut fuel when you overboost. What CEL are you getting? Also, when you disable a CEL it doesn't prevent the underlying error condition. Sounds like you have access to edit the ROM, so you can reduce the wastegate duty cycle for the RPM you're overboosing.
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Old 01-10-2021, 02:08 PM   #7
Chi_San
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Quote:
Originally Posted by kopele View Post
I'm not familiar with the fuel cut you're describing, and I don't see anything in RomRaider that would cut fuel when you overboost. What CEL are you getting? Also, when you disable a CEL it doesn't prevent the underlying error condition. Sounds like you have access to edit the ROM, so you can reduce the wastegate duty cycle for the RPM you're overboosing.
P0244

Yeah, I'll be tinkering with it this coming week. What I think is happening is the wastegate is going to full open, but there's a restriction either in the stock design of the downpipe, or in the exhaust itself, and it's causing overboost at higher RPM. If I could find a bolt on 3" exhaust for this thing, the problem would have been solved a year ago, but nobody has ever made a full bolt on exhaust for a Baja ever. >_>

I got super distracted last night by someone posting up a graphics card that I'm trying to buy, so I forgot to plug my laptop in last night... I'll charge it up now and set it up for logging.
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Old 01-11-2021, 04:24 PM   #8
kopele
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I found a couple of posts talking about a similar situation:
https://www.romraider.com/forum/view...hp?f=15&t=9769
https://www.romraider.com/forum/view...hp?f=15&t=7611

I guess the CEL logic can delay the actual occurrence of fuel cut.
Raise you boost limit and send it
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Old 01-12-2021, 12:05 AM   #9
Chi_San
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Quote:
Originally Posted by kopele View Post
I found a couple of posts talking about a similar situation:
https://www.romraider.com/forum/view...hp?f=15&t=9769
https://www.romraider.com/forum/view...hp?f=15&t=7611

I guess the CEL logic can delay the actual occurrence of fuel cut.
Raise you boost limit and send it
Well, stock boost limit is 30 PSI... lol...

I did look at the table with the Wastegate Duty Cycle. It looks like I made an error copying it over from another map, everything was moved down...

I fixed it, but I haven't had a chance to flash it yet. If this doesn't fix it, I have a second map ready with more reductions on the %'s for the WGDC.

I save all my maps, so I can see when everything got out of whack. I thought I copied the WGDC over from an old 2002 WRX map, but it's completely different, so I'm not sure.

If this works, though, I'll be quite happy... The top end still sucks really bad in the Baja, but it's a TD04 on a 2.5, so the bottom end is super punchy. My 3,950lb Baja goes up hills in 5th gear better than my old 2.0 WRX with the stock TD04 did in 4th. o.x
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Old 01-12-2021, 11:02 AM   #10
kopele
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Quote:
Originally Posted by Chi_San View Post
Well, stock boost limit is 30 PSI... lol...

I did look at the table with the Wastegate Duty Cycle. It looks like I made an error copying it over from another map, everything was moved down...

I fixed it, but I haven't had a chance to flash it yet. If this doesn't fix it, I have a second map ready with more reductions on the %'s for the WGDC.

I save all my maps, so I can see when everything got out of whack. I thought I copied the WGDC over from an old 2002 WRX map, but it's completely different, so I'm not sure.

If this works, though, I'll be quite happy... The top end still sucks really bad in the Baja, but it's a TD04 on a 2.5, so the bottom end is super punchy. My 3,950lb Baja goes up hills in 5th gear better than my old 2.0 WRX with the stock TD04 did in 4th. o.x

The boost limit table is in psi absolute, which includes atmospheric pressure. When you subtract ~14psi atmospheric pressure that's only ~16psig. Bump it up and you're good to go.
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Old 01-12-2021, 01:24 PM   #11
Chi_San
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Quote:
Originally Posted by kopele View Post
The boost limit table is in psi absolute, which includes atmospheric pressure. When you subtract ~14psi atmospheric pressure that's only ~16psig. Bump it up and you're good to go.
Are you sure? The boost limit on my WRX was 12PSI, so...

I can bump it up from 30 to 45. I think if you set it higher than the MAP sensor can read, it triggers at the maximum reading for the MAP sensor...
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Old 01-12-2021, 02:24 PM   #12
kopele
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What is the stock CAL ID for your car? I looked at a few 05 Baja and 02 WRX roms here and they are all psi absolute. The MAP high input CEL is triggered by voltage from the sensor, when you actually reach the max you'll get the CEL.Your other option is to tune it for 15psig instead of 17.
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Old 01-12-2021, 11:23 PM   #13
Chi_San
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Quote:
Originally Posted by kopele View Post
What is the stock CAL ID for your car? I looked at a few 05 Baja and 02 WRX roms here and they are all psi absolute. The MAP high input CEL is triggered by voltage from the sensor, when you actually reach the max you'll get the CEL.Your other option is to tune it for 15psig instead of 17.
The problem is that the tune is only calling for 6-10 PSI when boost cut hits. It's lower down where I hit 17 PSI...

I got tomorrow off, so tomorrow will be 'tinker with the Baja day'.

A2WC500L I think is the CAL ID.
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Old 01-13-2021, 04:45 PM   #14
Chi_San
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Well, I was able to recreate my process that led me to this point:

I bought the Baja with an overboost problem. In 5th and 4th gears, flooring it, it would run away on the boost, hit boost cut, and just really not want to run right. Idled like crap, too.

I replaced the hose clamps on the boost control lines, and replaced a few of the lines themselves, and this helped, but didn't fix it. I messed with the wastegate, but counted turns and reset it in the end. In desperation, I pulled 10% off the wastegate duty cycle in the higher RPM's, or so I thought. I must have been tired, angry, frustrated, or something else, and ended up ADDING 10%. This effected everything after...

I ended up finding that the boost hose with the Pill in it had been either sabotaged, or was... no, it couldn't be anything else. There was a hole poked in the hose, through both sides, as if with a pin, in the middle of the hose, not one end. I replaced this hose, and the pill, and thought I had everything figured out.

I then got distracted with a persistent missfire at idle, and a miss during low throttle and accel. Tracked it down to the #3 cylinder. I replaced (bought a brand new) coil pack, and replaced all of the plugs. The misfire persisted. I pulled the #1 and #3 injectors and swapped them, and the misfire followed the injector. I bought 4 used Injectors off a dude parting out a Baja turbo, and broke one installing it, but managed to replace both driver side injectors. Misfire fixed.

After this, the boost cut came back, and I never looked at the duty cycle table, because I had assumed I had already 'fixed' that. Until this thread.

So, the changes I made: I reset the wastegate duty cycle table from 3000-6500 RPM, bumped the boost limit from 30psi(a) to 45psi(a), and put in a .5psi cycle in the boost target (17psi down to 16.5psi, back up), until it tapers.

I flashed the map this morning and drove it, and the entire power band is now smooth. From 2,000 RPM to redline, there's no sense of boost running away then pulling back, no boost cut, no surging, nothing. It's just smooth.

So, I'm calling it 'fixed'. There's still issues, like an idle that just doesn't want to idle, but for the most part, it's now really enjoyable to drive, for the first time since I've owned it. I'm also not actually hitting target boost, it's 2 PSI under (I'm only hitting 15psi, not 17), but I think this is due to me pulling a turn out of the wastegate arm, which I will be fixing shortly (assuming I have a spare C clip).

So, my 2 years of owning this thing being a constant source of frustration are... Not over, but much, much improved.
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Old 01-13-2021, 04:58 PM   #15
kopele
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Glad you made progress and figured it out, congrats!
If I were you I would reset the wastegate arm to it's default position and adjust the WGDC tables instead.
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Old 01-13-2021, 06:54 PM   #16
Chi_San
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Quote:
Originally Posted by kopele View Post
Glad you made progress and figured it out, congrats!
If I were you I would reset the wastegate arm to it's default position and adjust the WGDC tables instead.
Gonna reset to it's original position, and if that doesn't have the desired effect, I'll go for the WGDC tables. 15psi isn't really that bad, the stock tune is for 4psi. >_> The torque from 2,000 RPM to 3,000 RPM is just bonkers at 15psi, it's actually a lot of fun for daily driving.
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Old 01-14-2021, 04:27 AM   #17
Chi_San
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Yeah, it worked. Hits 17PSI, holds it until it tapers, keeps it within a really close margin to the target boost, no more boost cut, and best of all, it's picked up a boatload of power through the upper rev range. It's not as fun as my WRX was, but my WRX was almost 700 lbs lighter than the Baja...
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