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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > MHD Tune is making my car slower…



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      07-02-2022, 02:26 AM   #1
e90_monster
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Hey first post on here, and it's probably going to be a dumb one. I recently got MHD for my 2011 335i and I've loved the tuning options but when I was timing pulls with my draggy I noticed it being slower than stock tune. So I looked into the logs a bit and I noticed that running any tune on MHD other than "Stage 0" (stock), I'm wildly missing boost targets. I'm going to include screenshots of the draggy times and data zap links to stock and tuned pulls. As for my setup I'm running stock FMIC, Coils, Plugs, with a 3.5 catless downpipe from VRSF. If anyone could help me understand what's going on I'd appreciate it.

Stock Pull: https://datazap.me/u/e90monster/stoc...&data=3-11

Tuned Pull (Stage 2): https://datazap.me/u/e90monster/boos...&data=3-11

Note: The draggy screenshots and the datazap files do not coincide, but one is stock and one is tuned.
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      07-03-2022, 04:08 AM   #2
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Well lets start off first with, for speed you should be shifting around 5500rpm. The turbo runs out of steam above 5k ish so shifting around 5500 is good for staying in the power band. i suspect an O2 sensor might be malfunctioning or something, any codes? Shows the AFR being 15 the whole log which would be super lean.
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      07-03-2022, 08:45 AM   #3
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I agree with the comment about codes, and afr being too lean. Something is wrong with your car, both stft and ltft are at exactly 0 (they shouldn't be). I think this may be a result of your car is detecting a problem and putting you into some kind of safety mode.

And your boost is way lower than it should be on the MHD log. Do you have the stock charge pipe still? If so, I'd check the connection at the throttle body, it may have cracked there and is leaking. Leak could be getting worse as the crack grows - could explain the worse performance on the mhd tune if the leak is growing. Stock charge pipe is a common failure point on n55.

And corrections look bad, but that could be due to your high afr, or potentially poor fuel.

Can you scan your car for codes and report back what you find?
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      07-03-2022, 08:50 AM   #4
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Not sure about the safety mode thing and your trims though, as your car is trying to make boost vs. reducing targets for safety. Your wastegate duty cycle is too high, and your throttle plate is wide open, so the car is definately trying to make boost, but failing. I do suspect a boost leak, at minimum.

Not totally sure what to make of your stft and ltft being exactly zero. Can you collect a log, and include fuel mode in the log? That should shed some light on the issue with your trims and afr.
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      07-03-2022, 09:00 AM   #5
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What kind of fuel are using?
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      07-03-2022, 09:41 AM   #6
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Thanks for all the reply's. I'm using 94oct fuel. I do still have the stock charge pipe, I was going to check for cracks when I had the chance because my mind instantly went to boost leak. I think the cause of this could be that I don't have any 02 sensors in my downpipe. I believe that could possibly be effecting my afr. I've attached the list of codes my ecu is giving me. Also if the car is running lean it probably isn't safe to be driving it right now right? I don't want to risk any knocking.
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      07-03-2022, 10:00 AM   #7
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Quote:
Originally Posted by wheela View Post
Can you collect a log, and include fuel mode in the log? That should shed some light on the issue with your trims and afr.
Not too sure how to enable fuel mode in MHD logging. It could be 0 because of the missing lamda regulating sensor.
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      07-03-2022, 04:25 PM   #8
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Why don't you have O2 sensors? You need those, I'd recommend putting them back asap, and don't push the car hard at all until you do.
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      07-03-2022, 04:33 PM   #9
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Quote:
Originally Posted by wheela View Post
Why don't you have O2 sensors?
I was told by my local muffler place that I didn't need them, apparently they said they only "regulate emotions". Also my MHD was meant to "code them out". After some more research of my own I think they just BS'd me to get my sale because they didn't have them in stock at the time. Do those sensors have anything to do with afr? And I certainly won't push my car hard at all, the engine seems to be in some sort of limp home mode without them.
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      07-03-2022, 05:20 PM   #10
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Quote:
Originally Posted by e90_monster View Post
I was told by my local muffler place that I didn't need them, apparently they said they only "regulate emotions". Also my MHD was meant to "code them out". After some more research of my own I think they just BS'd me to get my sale because they didn't have them in stock at the time. Do those sensors have anything to do with afr? And I certainly won't push my car hard at all, the engine seems to be in some sort of limp home mode without them.
They totally bs'd you. You absolutely need them, they are what reads your afr. Even with a catless dp and the mhd fix, you still need both of them. The dme has routines that use the downstream sensor to check the upstream one that reads your afr. And mhd doesn't code them out - it stops your dme from throwing a check-engine light if you're running a catless downpipe. I'd stay away from that shop, they have no idea what they're doing. Did they keep your O2 sensors? If so, they owe you two sensors. But given they don't know what they're doing, you may want to consider cutting your losses and getting new ones somewhere else. Sorry you're dealing with this, it's hard to imagine a shop could be that incompetent.
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      07-03-2022, 08:04 PM   #11
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Quote:
Originally Posted by wheela View Post
Did they keep your O2 sensors? If so, they owe you two sensors.
They cut through the downstream sensor and damaged the lambda regulating probes wiring. They also cut through the welded anchors on the OEM downpipe making it unsellable. I'll probably just cut my losses and supply my local dealership with the parts to do it for me. It sucks but it is what it is, we're BMW owners we're used to stupid bs. Do you think that is the root of my issue though? I probably still have a boost leak but in terms of healthy running? Also is there anyway for me to adjust the AFR, so it runs more rich instead of lean in the meantime?
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      07-03-2022, 09:56 PM   #12
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Quote:
Originally Posted by e90_monster View Post
They cut through the downstream sensor and damaged the lambda regulating probes wiring. They also cut through the welded anchors on the OEM downpipe making it unsellable. I'll probably just cut my losses and supply my local dealership with the parts to do it for me. It sucks but it is what it is, we're BMW owners we're used to stupid bs. Do you think that is the root of my issue though? I probably still have a boost leak but in terms of healthy running? Also is there anyway for me to adjust the AFR, so it runs more rich instead of lean in the meantime?
Sorry man, if I was you I'd just bring it to the dealership too. It does look like a boost leak is there, but first priority is those O2 sensors, your car won't run right without them. The afr value in your logs isn't real, the dme has no idea what the real afr is with no O2 sensors. I'm sure it's running on some kind of defaupt open loop setting since it can see there is no O2 feedback, but any leaks in the system, or other variation will throw the open loop values off. It's no use trying to make any adjustments without that O2 sensor feedback to tell you what adjustments to make. If you have a boost leak, you may actually be running rich vs. lean as showed by your logs, as your car would target a fueling value based on your maf sensor, but a lot of that measured air would be escaping and not entering the engine if you have a boost leak.
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      07-03-2022, 10:18 PM   #13
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Boost is way low. I have MHD stage 1+ and routinely hit 17.9 or 18.0 PSI.
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      07-03-2022, 11:47 PM   #14
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Quote:
Originally Posted by wheela View Post
If you have a boost leak, you may actually be running rich vs. lean as showed by your logs, as your car would target a fueling value based on your maf sensor, but a lot of that measured air would be escaping and not entering the engine if you have a boost leak.
Yeah that's very likely. I'm going to get the sensors put in asap, I appreciate the help. I'll probably post a log here when it's all done to see if the afr and charge pipe were the only issues👍
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      07-04-2022, 08:44 AM   #15
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Let us know how it goes!
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      07-07-2022, 05:19 PM   #16
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Quote:
Originally Posted by wheela View Post
Let us know how it goes!
So I just had the sensors put in along with a new aluminum charge pipe by my local BMW garage. Something is really wrong, I'm making wayyyy less boost than I should be. My AFR is updating properly now though. Running stage 2 MHD for the record.

https://datazap.me/u/e90monster/log-...&data=3-16

Edit: I've noticed that my boost deactivation RAM is the difference between my boost targets and actual boost numbers. But I'm not getting any boost deactivation codes or boost pressure sensor codes. My post cat sensor still appears to be a static value but it shouldn't affect boost and my AFR appears healthy other than spiking to 150+ on decel.
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      07-07-2022, 09:43 PM   #17
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Quote:
Originally Posted by e90_monster View Post
So I just had the sensors put in along with a new aluminum charge pipe by my local BMW garage. Something is really wrong, I'm making wayyyy less boost than I should be. My AFR is updating properly now though. Running stage 2 MHD for the record.

https://datazap.me/u/e90monster/log-...og=0&data=3-16

Edit: I've noticed that my boost deactivation RAM is the difference between my boost targets and actual boost numbers. But I'm not getting any boost deactivation codes or boost pressure sensor codes. My post cat sensor still appears to be a static value but it shouldn't affect boost and my AFR appears healthy other than spiking to 150+ on decel.
Ahh, fuel trims are back! Afr seems fine, and your corrections are now gone with running proper afr (not that you'd expect any with that horrible boost). By the way, afr should spike up to 235 on decel after a few seconds.

Your boost... the negative stft at WOT could indicate a boost leak, but I suspect a leak is only 1 part of the problem. If a boost leak was the only problem, then I think your load actual would be much higher, because the turbo would still be sucking all that air passed the MAF sensor in your intake, so your car would think it was moving a lot of air. But your load actual is very low. This means the turbo isn't consuming a lot of air, despite running a pretty high wastegate duty cycle. So I think the problem is you aren't making boost vs. having a boost leak.

Are you familiar with the vacuum system that closes the turbo wastegate to make boost? There's a vacuum pump that's attached to a vacuum tank built into the valve cover. From there, 1 vac line goes to your boost solenoid, and another vac line goes to your exhaust flap. Your boost solenoid is connected to your wastegate, which is normally open. The more duty cycle the dme sends to the boost solenoid, the more the wastegate is pulled closed to make boost. It's fairly common for the boost solenoid (bmw calls it the pressure converter) to go bad. Or one of the vac lines in this system to go bad. If your not getting enough vacuum (leak in this system, or bad vac pump), then the boost solenoid can't pull the wastegate shut to make boost. If the boost solenoid is bad, you can't get vacuum to the wastegate actuator to pull it closed and make boost. If it was my car, I'd start trouble-shooting this vacuum system.

Please note, even a leak in the vac line for the exhaust flap can impact your boost. In the graph, the red line is the vac curve for the boost solenoid and exhaust flapper (the auxillery). This shows how much vacuum the system should make when the car is running.
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Last edited by wheela; 07-07-2022 at 09:57 PM..
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      07-08-2022, 12:33 AM   #18
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Quote:
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So I think the problem is you aren't making boost vs. having a boost leak.
Wow thank you so much for the info, you're probably right that I have a vacuum leak somewhere. I did just get a code (2C57) "Charging pressure control, plausibility pressure too low". So I have a boost leak and probably a vacuum leak too. This only happened after BMW installed the 02 sensors and charge pipe, so is it correct to think that this sudden lack of boost due to a leak is down to a mistake they made? Clipping a vacuum line, not properly installing the charge pipe, etc. I was not having close to this much leakage before I took it into them. How would I go about diagnosing my vacuum leak, I do have a vacuum tester. Should I go from line to line and look for a drop in pressure? Or just take it back to BMW.
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      07-08-2022, 12:48 AM   #19
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Hi everyone. Newbie from South africa here. Mine is a2006 320d M47 msport. Dreaded engine fault, reduced power was coming up intermittently but has decided in the last two weeks to make itself a permanemt item. Car revs and has reasonable power up until 2500rpm then all blow and no go. Mech has done a diagnostic and has come up with the attached faults. He believes its the DDE as he says that when he disconnects the fuel rail sensor, the accelerator pedal fault goes away and vice versa. Any help would be greatly appreciated.
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      07-08-2022, 06:17 AM   #20
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Quote:
Originally Posted by e90_monster View Post
Wow thank you so much for the info, you're probably right that I have a vacuum leak somewhere. I did just get a code (2C57) "Charging pressure control, plausibility pressure too low". So I have a boost leak and probably a vacuum leak too. This only happened after BMW installed the 02 sensors and charge pipe, so is it correct to think that this sudden lack of boost due to a leak is down to a mistake they made? Clipping a vacuum line, not properly installing the charge pipe, etc. I was not having close to this much leakage before I took it into them. How would I go about diagnosing my vacuum leak, I do have a vacuum tester. Should I go from line to line and look for a drop in pressure? Or just take it back to BMW.
Hmm, hard to say if they did something, or if whatever was going on before just continued to get worse. However, the vacuum lines for the boost solenoid and exhaust flap come out of the valve cover, right above the turbo and O2 sensors. So putting in your O2's it definately seems plausible that one or both of those vacuum lines could have been disturbed, as they're working in that area. Also, less likely, but the vacuum pump is on the other side of the engine - the charge pipe goes by it. I wouldn't think they'd have any interaction with the vac line coming from the vac pump when working on the charge pipe, but you never know. Actually, the vac line for the exhaust flap is over on the driver side wheel well by the charge pipe, I could see that getting knocked loose doing the charge pipe.

I'd probably bring it back to bmw first if it got way worse after their work. I know my local dealership is pretty good about that kind of thing. But if you have a vac tester and want to try, here's a way I just told a different forum member a couple days ago:

Here's a way you can check, below I just copied what I told somebody else from a different thread (different forum) who was chasing a similar issue:

To measure how much vacuum you have while running, I'd try connecting a Mighty Vac to the line from your valve cover that goes to your boost solenoid, then turn your car on and see how much vacuum it reads. That should be how much vacuum the boost solenoid has available to work with. Not 100% on the requirement, but per the n55 technical document, it looks like there should be at least 0.8 bar of vacuum available.

You could also use the Mighty Vac to check for vacuum leaks. With the car off, connect to the line from your boost solenoid to the wastegate, and pump up the vacuum to make sure your wastegate and the line going to your wastegate will hold vacuum. Then do the same thing with the line from the valve cover that goes to your exhaust flap, as a leak in that line could also reduce the vacuum available when the car is running.

Good luck, and let us know how it goes!
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      07-08-2022, 06:24 AM   #21
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Just a quick note about the exhaust flap vac line routing - it comes out of the valve cover by the boost solenoid, but then it routes back under the cowl and over the engine (cylinder 5 & 6 area), then down with some bundles past the back of the intake by all the DME connections, then over to by the driver side wheel well where it connects to a different line that runs back to the exhaust. They'd have to disturb that vac line to connect your o2 sensors to the dme. And that place at the driverside wheel well where the vac line connects to the other line to the muffler - it's very easy to disconnect there. I'll see if I can find a pic.

Edit:
Here are some pics - one from my car of the flap vac line in the wire bundle coming down from the cowl, back behind the air box (going past the dme connections), and one from the internet (not my car) showing that vac line connection on the driver side wheel well, the one that's easy to disconnect.
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Last edited by wheela; 07-08-2022 at 06:36 AM..
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      07-08-2022, 11:37 AM   #22
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Some good info here.
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