[OLD_BMW]

Hi all, 335i N54 2006 e92 with 100k miles. Bone stock All N54 “quirks” replaced apart from Turbos and Vanos solenoids.

I found it to be pretty “slow” at low rpm and decided to log some data.

https://datazap.me/u/oldbmw/log-1706...og=0&data=3-21

It seems like 2nd gear WOT turbos only hit boost target at 4,6k rpm.

I’ve seen posts where the same engine hits boost target at around 2-2,5k rpm 2nd gear WOT.

It’s running stock turbos, has a pretty bad wastegate rattle on cold startup so my theory is that it’s leaking boost through the wastegates potentially, taking a longer time to spool up.

Apart from the lag the car has no error codes, tunes etc. All stock and tidy.

What could this be? Or is this normal?

[Sgop335]

Yes very laggy. About 7psi in 1.3s. A good turbo could do 15-20psi in that time...

[OLD_BMW]

Originally Posted by Sgop335

Yes very laggy. About 7psi in 1.3s. A good turbo could do 15-20psi in that time...

Would you say that it’s the turbo itself?

Or a possible wastegate leak, as Ive managed to inspect the compressor wheel quite recently on both turbos and it has no wobble and spins quite nicely as well.

[iqraceworks]

Originally Posted by OLD_BMW

Would you say that it’s the turbo itself?

Or a possible wastegate leak, as Ive managed to inspect the compressor wheel quite recently on both turbos and it has no wobble and spins quite nicely as well.

Could also be boost solenoids causing the issue, or a leaky vacuum hose, or all kinds of other things. Do you have MHD or some other way to record a log? That is a great way to see exactly what's going on with everything.

[OLD_BMW]

Originally Posted by iqraceworks

Could also be boost solenoids causing the issue, or a leaky vacuum hose, or all kinds of other things. Do you have MHD or some other way to record a log? That is a great way to see exactly what's going on with everything.

I have attached a log at the first post in this thread. Maybe I should log something that’s not on there to identify one of these things?

Thanks!

[oVeRdOsE.]

I had this exact same issue, seems to be not that uncommon, I did few post on jb4tech and it was turning around :

- bad turbo and or waste gate
- bad setting in jb4 or mdh
- bad boost solenoid.
- fuel pressure sensor

I had no code, car runs super healthy, but with a massive turbo lag. I was on backendflash at 19psi, and the 19psi was hitting hard around 4k rmp, and before almost nothing.

unfortunately for you, I never found the issue, I swap for a single turbo.

my stock turbo were fine, no shaft play, no rod rattle. However I did not test the actuator membrane, but doupt it was the issue with only 115k km.

[Sgop335]

Originally Posted by OLD_BMW

Would you say that it’s the turbo itself?

Or a possible wastegate leak, as Ive managed to inspect the compressor wheel quite recently on both turbos and it has no wobble and spins quite nicely as well.

glad it was not assumed automatically it is the turbo. The turbo wg operates on vacuum, so any vacuum leak- hose, canister, solenoids etc can cause laggy.
ofcourse wgs not sealing properly can also do it, probably original?
Good time to go w aftermarket turbos

[C4maro]

Is the exhaust valve opened with engine vaccum? I just wonder this because I did feel a low end power increase when I did the golftee mod.(maybe a leak in valve mechanism?) Could be placebo but I have heard others say the same thing.

Anyway though, as others have said, biggest thing that brought my stocker back to life when I got it was replacing all the vaccum lines around the engine. Im planning to do the solenoids next to see if that helps even more.

[studio54]

Originally Posted by OLD_BMW

I have attached a log at the first post in this thread. Maybe I should log something that’s not on there to identify one of these things?

Thanks!

I think you should still do a single pull log in 3rd gear, cruising at 2500 rpm, then go WOT, up to whatever you can (6000 for example).

1st gear and 2nd gear pulls usually take more RPM to reach target than in 3rd cause RPM rise quicker in those lower gears.

According to MHD and to other log ,healthy turbos are supposed to reach 13 psi in 500 rpm in 3rd gear from 2500rpm (with a tune)

Knowing this, you should expect under 500 rpm to reach stock target, try in 3rd, it will be easier to compare with other logs

[lowrydr310]

I have some old boost/wastegate solenoids that are functional if you want to try, I can give them to you if you cover shipping.

I was chasing a jerky throttle response issue and replaced mine which made no difference, ended up being something else.

[OLD_BMW]

FOLLOWING UP ON THE SOLUTION...

Hi all, just for history...

I went and refurbished the wastegates. Had a specialist in the UK Remove the turbos, remove the old wastegate mechanisms and replace it with a new ones.

Now the car feels a lot more lively and much faster in general. The problem was leaky wastegates. You can actually hear the turbos as well, before the car sounded NA, now you can hear the whistle from the turbos. Exhaust seems to be quieter as well, meaning more exhaust gasses go through the turbo properly.

So lesson learned, check wastegates if car feels like it's down on boost with a stock turbo setup. Thanks of all of your replies!

[iqraceworks]

Originally Posted by OLD_BMW

FOLLOWING UP ON THE SOLUTION...

Hi all, just for history...

I went and refurbished the wastegates. Had a specialist in the UK Remove the turbos, remove the old wastegate mechanisms and replace it with a new ones.

Now the car feels a lot more lively and much faster in general. The problem was leaky wastegates. You can actually hear the turbos as well, before the car sounded NA, now you can hear the whistle from the turbos. Exhaust seems to be quieter as well, meaning more exhaust gasses go through the turbo properly.

So lesson learned, check wastegates if car feels like it's down on boost with a stock turbo setup. Thanks of all of your replies!

For all the money and labor that's involved.....why didn't you just go ahead and replace the turbos instead of just the waste gates?

[OLD_BMW]

Financially it made more sense just to fix the wastegates at the time since the turbos were in pretty good shape and I'm not planning to tune the car, keeping it stock. labour was roughly 500pounds with the wastegate repair kit costing 150, when new turbos would have been 500-850minimum just for the turbos alone+500 for labour. I'm aiming to get a few more years out of the oem snails that I have now.