m4 f82, is my lpfp running low?

[sparkymarky]

Datalogged a couple of runs. Couple of questions if you don't mind guys? Thankyou :)

1. LPFP seems to always be around 73/75psi? Even at wot and 10% pedal and throttle
position.

Stock s55's I've seen online seem to run lpfp at 83psi consistently?
tuned seem to run up to 90psi.



interestingly in less demanding conditions -eg 6 degrees throttle angle I sometimes get LPFP 80 psi although at other times I get same 75psi at that throttle angle and low revs. (note: the HPFP seems ok and holds whats
targeted by DME - seems to target and meet 2700psi but does go to 2900 sometimes and holds it - even when dme is only targeting 2700psi it says)

I am running BM3 cs+ by the way.


2. Also ,would the lpfp cause the occasional single knock event occaionally at around 2.3 to 3k? I run 93 octane btw. (super unleaded here in UK (AFR's are around 13 to late 14's occasionally at midrange and at 5k to 6k rpm they taper down to 12.5psi
so that seems ok)

[TopJimmy]

With proper Premium fuel and only a CS+ tune the LPFP and HPFPs shouldn't be under any stress, and you shouldn't be knocking at all. Even using a custom E85 tune with stock turbos I don't crash any pumps.

Post a link to your log and pic of where you think you see issues.

Did you open a case with BM3 support?

[sparkymarky]

Hi buddy, the graph is here, take a look from approx 29 seconds (3rd gear pull) to 38 seconds as this is where I was mostly WOT/100% throttle angle.
-Note the red knock in the bottom red line too @ 21 and 30 seconds (deselect some of the channels to clear up the graph)
- You can see in the figures the LPFP is around 520Kpa, online converter to psi says that's only 75psi..... ? hmmm.

https://www.bootmod3.net/log?id=5fb6...90c67870b6e349

[horsepower_and_hounds]

As TopJimmy said.... you should be good unless they are defective. If your mixing E85 you should be good up to between 5-6 gal before you trim error

[sparkymarky]

Hi horsepower_and_hounds, nope not using any E85. Just straight pump fuel at 93 octane

[terahertz]

Your STFT looks good so your fueling is doing fine. The knocking is because your octane is poor. You can tell this by looking at the ignition timing for all 6 cylinders and you can see it's all over the place. Octane is poor all across the US right now, maybe related to covid and poor demand. Can try adding 2-3 gallons e85 or dropping down to CS.

[sparkymarky]

terahert, thankyou for taking the time to look at the graph buddy

I did just check a log i did a week back on different batch of 93 fuel from a different gas station and that log had no knocks in it and the timing was much more uniform on that batch.

eg it woiuld go something like this is this normal? :

2nd gear all timing normnal from say 2k rpm to 3k and increasing in advance.
then from say 3k to 4k, cyl 4 would be two degrees behind the rest (eg cyls 1,2,3,5 &6 at 9 degrees but cyl 4 would 7 degrees
then from 4k to 5k that 2 degree differnce would reduce until all timing even at 5k upwards

Gear 3. Similar story, one cyl behind - it could be cyl 2 now but follows the same pattern, starts off say 2-3 degrees retarded from rest form say 3k bu then advances gradually in 0.5 degree increments until all cyls are in line again (as revs increase).

Gear 4. now two cyls retard by same 2-3 degrees, then advance to be all equal as revs rise.

Is this normal pattern? one cyl - not always the same lags the tohers? There were no knocks in that log as i say.

[sparkymarky]

terahert, thankyou for taking the time to look at the graph buddy

Fuel quality - i tend to think you're right pal as I did just check a log i did a week back on different batch of 93 fuel from a different gas station and that log had no knocks in it and the timing was much more uniform across all cylinders on that batch.

The timing on that batch of fuel would go something like this pattern............ is this normal? :

2nd gear: all cyl. timing same and advancing equally up to say 3k,
then from say 3k one cyl (usually cyl 4) lags 2-3 degrees behind the other cyls (which are all the same still). Eg cyls 1,2,3,5,6 at +9 degrees but cyl 4 would be + 6.7 to7 degrees
then from 4k rpm to 5.5k rpm that 2 degree difference would gradually reduce until all timing even at 5.5k upwards

Gear 3. Similar story, one cyl. 2 to 3 degrees behind the other 5 (and again, the other 5 are all perfectly equally timed- but it would be a different be cylinder now, such as cyl 2 this time. But then that cyl follows the same pattern as cylinder 4 did in the previous gear acceleration; as you increase revs it gradually increase to catch up with the other 5 again.

Gear 4, same pattern but now two cylinders would lag behind the other 4 then advance into line gradually again as revs increase

Is this normal pattern? one cyl - lags the others but then advances into line? Initially i thought i had an issue with cylinder 4 coil or something but i noticed it happens on different cylinders, but they all follow this pattern as you go up through the gears.
Or is the DME pulling timing on random cylinders? There were no knocks in that log as i say, but i guess no knock logged doesnt mean timing isnt being pulled when 1/2 cyl shows timing lagging behind others

[terahertz]

a couple cylinders is fine if it recovers. sounds normal from what you are describing, but if it keeps dropping back to the same level, like you see in 4th gear in the log you posted, you're octane/knock limited.

try to log in 3rd or 4th. 2nd usually has traction issues so you're not getting full load

[sparkymarky]

Awesome, thanks for that buddy. I didn't even spot that the timing target was being reduced in 4th gear - just noticed it at 36 seconds now you've said it.

Will put it down to fuel like you suggest.

Not sure what bad trims would look like? I take it you mean stft? I dont want to take up your time but it would be good to know what bad trims would present like


and i wonder why my LPFP is only around 75psi when others i see are 83 to 90 psi?? any clues? Would you mind checking any logs you have for your LPFP figure?

[terahertz]

STFT close to 1 is normal. Means it isn't adding or subtracting much fuel to compensate for anything. You're at .96 which means it's subtracting 4% fuel as compared to what is programmed in the map to hit the programmed AFR/lambda.

[sparkymarky]

Ah ok got it. So the dme is leaning off the mix by 4%, that's interesting to know as i did think my AFRS were a bit too high as they are around 14.5 quite a lot and the most they ever come down to WOT is 12.5 but i guess the dme knows better than the map how much it can get away with leaning it off. fingers crossed lol.

I think D.I engines can run leaner having quietly read up careythelabelguys posts so i've dismissed the AFR's appearing high.

I'm new to logging and this is my first post on it so your help is awesome

[TopJimmy]

Originally Posted by sparkymarky

Awesome, thanks for that buddy. I didn't even spot that the timing target was being reduced in 4th gear - just noticed it at 36 seconds now you've said it.

Will put it down to fuel like you suggest.

Not sure what bad trims would look like? I take it you mean stft? I dont want to take up your time but it would be good to know what bad trims would present like


and i wonder why my LPFP is only around 75psi when others i see are 83 to 90 psi?? any clues? Would you mind checking any logs you have for your LPFP figure?

Here's the manual I found for interpreting logs. Great resource!
https://f30.bimmerpost.com/forums/sh....php?t=1732327
In his LPFP section the log shows a steady 85PSI.

[sparkymarky]

Originally Posted by TopJimmy

Here's the manual I found for interpreting logs. Great resource!
https://f30.bimmerpost.com/forums/sh....php?t=1732327
In his LPFP section the log shows a steady 85PSI.

Exactly - why the hell is mine only running 72/75psi mainly?



Thanks for the link!

[sparkymarky]

Just did a scan with ISTA D, no fault codes logged. Was hoping for a low pressure sensor code but nothing flagged.

Weird

[horsepower_and_hounds]

You can always add some MTBE if no E85 available. All our E85 pumps around here are out due to using ethanol for hand sanitizer

[TopJimmy]

I'm getting started with a Paul Johnson E85 tune and the first revision, so this is only 22PSI boost for timing checks, but my LPFP pressure seems similar to your description. Here's a pic of a log isolated to just the gas pedal%, LPFP and HPFP PSIs. The run is a single 4th gear pull from ~40mph (2200RPM) up to ~130mph (7K).

My LPFPs start at 76PSI, run mainly between 72-75PSI for the run, and then hang in the low 80s as the fuel surge subsides. There is the quick dip in the beginning as the hi-pumps kick in, and then the spike after as the hi-pumps drop down, but I think it looks pretty consistent.
[It seems this nice picture below only shows on the web, not on the phone app, in case you wonder...]

[sparkymarky]

very interesting topjimmy, thanks for posting that.

I've just plotted a graph of rpm v lpfp at rpm and lpfp, it looks good actually

[sparkymarky]

Looked in ISTA/d notes earlier, and it says in the screenshot 2 that the Low Pressure side should be 'approx' 5 bar (72psi) and then in screenshot 1 it says between 5.2 and 5.9 bar (75 to 85psi) so unsure why some people operate higher than others they aren't operating higher and its more their sensors reporting different pressure values as they wear (also read in ISTA that the sensor is a strain relief type with wheatstone bridge - so accuracy will likely vary over time as resistor values wander in the bridge etc). Might throw a L.P sensor in there if it bugs me to see if that makes any difference as they are like £40 some places online


[IMG] [/IMG]

[Chris@VargasTurboTech]

Normal and safe. No worries.

[sparkymarky]

Awesome thanks chris for weighing in too.

[jibarra]

Originally Posted by TopJimmy

I'm getting started with a Paul Johnson E85 tune and the first revision, so this is only 22PSI boost for timing checks, but my LPFP pressure seems similar to your description. Here's a pic of a log isolated to just the gas pedal%, LPFP and HPFP PSIs. The run is a single 4th gear pull from ~40mph (2200RPM) up to ~130mph (7K).

My LPFPs start at 76PSI, run mainly between 72-75PSI for the run, and then hang in the low 80s as the fuel surge subsides. There is the quick dip in the beginning as the hi-pumps kick in, and then the spike after as the hi-pumps drop down, but I think it looks pretty consistent.
[It seems this nice picture below only shows on the web, not on the phone app, in case you wonder...]

are there any concerns about that when the hi-pumps kick in? I'm having a similar issue and I'm going to be replacing the ekp to see if it fixes it.