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-   -   Strange Surging As The Power/Boost Comes on (https://www.n54tech.com/forums/showthread.php?t=59202)

andrew85 08-15-2019 04:05 AM

Strange Surging As The Power/Boost Comes on
2 Attachment(s)
Hi everyone,

So I am about 3 weeks into ownership of a 2008 335i Auto and working though all its little quirky problems. The car had a JB4, index 12 injectors, miltek catback exhaust, charge pipe and dual cone intakes, aside from that is stock. It does have a case of wastegate rattle if you free rev to 3-4000rpm and let off the throttle.

What i am trying to fix currently is the way it surges as it comes on to power, it's like boost spikes, then dies a bit then pumps the boost in again.

So far, I have fitted new (1 step colder) ngk plugs and gapped correctly. Updated the JB4 to the newest firmware. Installed the latest pump backend flash through MHD (this did improve the surging). The only settings I have really played with on the JB4 are in relation to wastegate rattle. Which I have read can cause this but I'm really having a stab in the dark with adjustments and have tried all ends of the spectrum for menu 10, 11 and 12, with not really a major noticeable change in the rattle, i have put them back close to where they were. The car has had a couple of tanks of BP ultimate through it now and had engine and gearbox oil serviced/filters changed etc.

I will attach a log of a 3rd gear pull in map1. I'd really appreciate any opinions on the log of how people think the engine is healthwise.


Dave @ BMS/Fuel-It! 08-15-2019 11:20 AM

Enable 6cyl timing under user adjustments & relog.

What fuel?

andrew85 08-16-2019 05:58 AM

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Hi Dave, Thanks for the quick reply. I enabled 6cyl timing and have done another log. I am using BP ultimate 98 fuel (I'm in Australia). Back in 2015, BP listed this as having zero ethanol, however, I can't find current specs from BP Australia.

However, this afternoon I also changed the engine mounts. The RHS one was fairly loose and the surging doesn't appear to be there anymore. I am thinking I was feeling the mount flex as the power came on. I have only taken it for a quick drive to warm up and get the log but the surging may have just been this worn engine mount.

On the same note, I'd love some feedback on the log. If anything shows any concerns. I am about to add ******* ********* and cooler and would love any advice on how to exact as much power as possible.

Thanks Again

Dave @ BMS/Fuel-It! 08-16-2019 12:48 PM

For most part this looks OK.

Some timing drops, but I'd attribute that to octane.

Get the rest of your FBO parts thrown on & relog.

One thing to note- may want to look into at least our stage 1 inline LPFP upgrade- your LPFP hits around 60 up top- once you make a bit more power- that will likely drop you own into the 50's psi wise = not good

andrew85 09-05-2019 04:29 AM

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If you could have a look at the updated logs that would be great and really appreciated. I've now spent about 10 days with the front mount, wastegate rattle fix (adjusted rods) and 3" *** less ***** on top of the original mods. The surging is still there. Oh, also replaced bank 1 02 sensor, which has smoothed the AFRs out a little.

I'll post 3 logs, the first one was just after the extra mods (first drive). It's map 2 running BP Ultimate 98 fuel. I think the car feels best on this map. On BP98 map 5 felt sluggish. However, the surging is least noticeable.

The second 2 are a few runs on an e20 mix on map 5, to see what the JB4 can auto tune to. I did quite a few logs on e20 as i am concerned about LPFP. It was pulling timing on cylinder one when under high load. So wot from low rpm, full boost you can clearly see the timing on that cylinder is low. This only showed up after e20. However map 5 is starting to come to life after 5-6 hard pulls. Still not as aggressive as map 2 on 98, but its feeling like a tuned car, not so quite as flat, like it did on 98 in map 5. The second map 5 log, its a slightly more gentle application of throttle to reduce low rpm load and i can't see the cyl 1 timing drop. That last pull is not as long either.

I have got the full bug with this car now (cos who needs a retirement fund anyway). LPFP pump is ordered and should be here soon. As well as a flex sensor to properly monitor e85 content and i'd like to push this current setup as far as stock turbos will go. If i can get a couple of months out of them before upgrading ill be very happy.

I'm starting to think the surging i'm feeling is the map pulling timing under high load conditions. If i ease the throttle on it pulls like a train, so 4th gear 3000rpm 20% throttle it feels like 500hp, but if i try and load the turbos like i would my Evo, say 60-70% throttle the n54 just doesn't feel aggressive it feels slower than 20% throttle acceleration. The Evo is a 4G63 Evo 6 tuned to around 320awhp and feels so much more exciting than the N54 (it does have much shorter gear ratios which play a factor but the Evo responds better to being loaded up). A highway roll the N54 would take the evo but the N54 just feels so flat. The other thing tainting my opinion is my other 2 cars ive spent most of my time in lately is a lightly tuned Megane Rs250 and an e60 M5. The megane, evo and M5 all have so much character to the engines as the rpms build.

The thing that is bugging me is, it wont really spin the wheels rolling the power on at low speeds (20-30kph) and i'm running really ****ty cheap tyres at the moment. I was kind of hoping to get a low end aggressive pull in the tuned n54 like to do in the e60 m5. That naughtly loss of traction in 1st and 2nd just isn't there. I have removed gear 1 and 2 boost limits as well, to see if that brought it to life, but it wont load up and break loose.

If the logs look good i'll get the LPFP upgrade done and play with some higher octane. Would running the Race BEF help with low end power delivery. I would love any advice on how to get more out of the current setup. Inlets were going to be next on the list, but i think i'll wait till i can do the turbo upgrade.

Thanks again and sorry for the story, just trying to paint a picture of what i'm feeling and why. The community around tuning these things is nothing short of amazing.

Dave @ BMS/Fuel-It! 09-05-2019 11:36 PM

Looked at the map 5 logs- look “ok”

Tbh your probably not feeling “much” because you aren’t targeting much boost.

I’d load the bef, get the LPFP installed & bump up to e50/60

The stock Turbos are small, so low end, and mid range is where they shine- you just need to turn things up.

andrew85 09-08-2019 05:05 AM

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Well, I loaded the Race BEF while still running e20 with original LPFP, so didn't do any hard pulls, but OMG it felt so much better in the lower RPM range. I can not believe how much difference that Race BEF made. It really sorted out the low end pull.

Anyway i got the fuel pump upgraded today and have gone to a e50 fuel mix. Did some more logs on map5. The thing feels amazing on e50. It peels through 1st and 2nd gear finally. :burnrubber:

I have attached a log. If there is anything of concern please let me know.

Thanks so much for the input. The car is flying with the ethanol mix and JB4 autotuning.

However, that did lead to the auto trans missing second gear on a 1-2 shift. I haven't done the solenoids yet. It was an aggressive high rpm wot shift (not logged) and for some reason just never got second gear. Trans temps were high thanks to beating on the car for about 20 mins prior. I wont risk any more WOT shift until the solenoids are done.

Dave @ BMS/Fuel-It! 09-08-2019 10:35 AM

Glad it’s moving now!

Overall log looks ok.

As for the trans- May want to look into an upgrade trans cooler

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