[Nolan2221]

Hey guys. I have a 2011 BMW 335i E93 (N55). It's stage 1 on MHD with a BMS cold air intake and upgraded charge pipe. Every time I do a 0-60 pull I keep getting high 6's even with traction control off and revving to 2.5k RPM before letting off the breaks. WHY?! it does have 135k miles on it. Could it be a carbon build up? Bad coils and plugs? Waste gate issue? I just can't figure it out. Below is a data log showing one of my better pulls. Thanks in advance you guys are the best!

https://datazap.me/u/nolan2221/slow-...data=1-4-11-14

[Aceway]

Do you have long cranks when first starting the car? Could be bad hpfp. 2011 cars have the same hpfp as n54 cars.

[Nolan2221]

Originally Posted by Aceway

Do you have long cranks when first starting the car? Could be bad hpfp. 2011 cars have the same hpfp as n54 cars.

I do, but I just had my HPFP replaced about a month ago.

[wheela]

Your rail pressure is fine so I don't think it has anything to do with your new HPFP. I noticed that your wastegate duty cycle% is way too high for this level of boost and your STFT goes very negative - I'd say you have a boost leak somewhere. I don't have any explanation for that high pressure fuel code, as your fuel pressure is fine, and your STFT is pulling fuel out.

[Nolan2221]

Originally Posted by wheela

Your rail pressure is fine so I don't think it has anything to do with your new HPFP. I noticed that your wastegate duty cycle% is way too high for this level of boost and your STFT goes very negative - I'd say you have a boost leak somewhere. I don't have any explanation for that high pressure fuel code, as your fuel pressure is fine, and your STFT is pulling fuel out.

I was thinking that too, but it doesn't feel like I have a boost leak. I'll get it pressure tested anyways just to double check. I'm thinking maybe coils and plugs because recently I'll get an occasional misfire and surge at WOT high rpm.

[Nolan2221]

Originally Posted by wheela

Your rail pressure is fine so I don't think it has anything to do with your new HPFP. I noticed that your wastegate duty cycle% is way too high for this level of boost and your STFT goes very negative - I'd say you have a boost leak somewhere. I don't have any explanation for that high pressure fuel code, as your fuel pressure is fine, and your STFT is pulling fuel out.

Could it be my Waste Gate?

[wheela]

Originally Posted by Nolan2221

Could it be my Waste Gate?

It could be, but your STFT is pretty negative on the pull. That means your AFR is richer than the DME is expecting, so it's pulling fuel out to keep AFR in check. This would only happen if your getting too much fuel injected, or if air measured by your MAF sensor is leaking out instead of going into your cylinders, as with a boost leak. Since boost leaks are pretty common, and your power is clearly down, I'd start by ruling out boost leak before going any further. If it was your wastegate, I don't think that would throw your trims negative. I could be wrong on this last point though, I know some people have incorrect AFR readings with exhaust leaks upstream of the O2 sensors, so if something is going on with your wastegate creating any kind of exhaust leak, I'm not sure how that may affect your trims.

[Nolan2221]

Originally Posted by wheela

It could be, but your STFT is pretty negative on the pull. That means your AFR is richer than the DME is expecting, so it's pulling fuel out to keep AFR in check. This would only happen if your getting too much fuel injected, or if air measured by your MAF sensor is leaking out instead of going into your cylinders, as with a boost leak. Since boost leaks are pretty common, and your power is clearly down, I'd start by ruling out boost leak before going any further. If it was your wastegate, I don't think that would throw your trims negative. I could be wrong on this last point though, I know some people have incorrect AFR readings with exhaust leaks upstream of the O2 sensors, so if something is going on with your wastegate creating any kind of exhaust leak, I'm not sure how that may affect your trims.

I work at a BMW dealership and I had a service advisor take a look at it and he told me that my charge pipe or cold air intake may be letting in unaccounted for air aka a leak. But you are saying that my ATF ratio is rich. And that's the opposite of that they're telling me. They're saying too much air is probably getting in either through a bad seal on my charge pipe or BMS intake. They didn't look at my logs or even plug it up. That was just their best guess. Any thoughts? They told me if my turbo was blown I would be blowing a lot of smoke out of the exhaust. Thanks again for all your help I SERIOUSLY appreciate you!

[wheela]

I'd say they're incorrect based on your logs. There isn't anything in your logs to suggest you're sucking in a significant amount of un-metered air - the negative STFT shows the opposite.

You mentioned a cold air intake, do you have an after market intake? Those can change how your MAF reads, and could explain the issue with your trims. The MAF sensor takes a sample of air from your air duct, and the tune correlates the reading to the cross section of your air duct to calculate how much air the engine is consuming. So if that duct where the MAF is located changes, it will throw off your DME's air measurement unless you account for it in the tune. If you have an after market intake, I'd try putting the stock one back on and take another log.

[wheela]

A lot of people have problems with the BMS intake if they don't adjust their tune for it. Honestly, you should be fine with the stock intake.

[NRigs]

If you replaced your HPFP a month ago and are still seeing those codes you should look into the fuel pressure regulator. The one that is in the gas tank opposite of the LPFP. That should fix those codes.

[Nolan2221]

Originally Posted by NRigs

If you replaced your HPFP a month ago and are still seeing those codes you should look into the fuel pressure regulator. The one that is in the gas tank opposite of the LPFP. That should fix those codes.

Okay thank you. I'll get that checked out. Main concern is why my car is still at a loss of power. You think the codes are related?

[wheela]

Originally Posted by NRigs

If you replaced your HPFP a month ago and are still seeing those codes you should look into the fuel pressure regulator. The one that is in the gas tank opposite of the LPFP. That should fix those codes.

One thing I don't understand, since his high pressure fuel pressure looks healthy in the log, and the n55 doesn't have a fuel pressure sensor for the LPFP, how would it know to throw a code if there was something going on with that fuel pressure regulator? I suppose maybe it could detect high pressure issues on start up from the low pressure side not priming properly?

[NRigs]

Originally Posted by wheela

One thing I don't understand, since his high pressure fuel pressure looks healthy in the log, and the n55 doesn't have a fuel pressure sensor for the LPFP, how would it know to throw a code if there was something going on with that fuel pressure regulator? I suppose maybe it could detect high pressure issues on start up from the low pressure side not priming properly?

I am honestly not sure. But I have read a few posts and there is a video on youtube I watched that said they were getting those codes. They said they changed the HPFP and the codes were still there along with long cranks. They replaced the fuel pressure regulator and codes and long cranks went away. It is a fairly inexpensive and easy DIY from the looks of it so it may be worth a shot.

[Info@mad-us.com]

Have you checked your plugs? May have a leaky injector causing pressure loss in the system when starting up the car.