changing the AFM make ANY difference? now with AFR data lm-1

[liam012]

Ok been having some problems with pinking on the 2.7
not sure if its due to high comp / lean mix or both.
so today in my warped logic thought that if i reduce the ammount of air going in i might help things, so i installed the old 320i AFm that i used to use for the 320i. the car is no different AT ALL? surely thi cant be right?
full throttle at 1500rpm in 3rd 4th or fifth gives pinking.. the very same as before.
i know to those who kno how all this stuff works my experiment may seem amusing but in my logic less air would of been a good thing.

i am just really suprised that a 2 litre AFM instead of the 325i AFM didnt affect the cars running in any way what so ever??

[gcorky]

Ok been having some problems with pinking on the 2.7
not sure if its due to high comp / lean mix or both.
so today in my warped logic thought that if i reduce the ammount of air going in i might help things, so i installed the old 320i AFm that i used to use for the 320i. the car is no different AT ALL? surely thi cant be right?
full throttle at 1500rpm in 3rd 4th or fifth gives pinking.. the very same as before.
i know to those who kno how all this stuff works my experiment may seem amusing but in my logic less air would of been a good thing.

i am just really suprised that a 2 litre AFM instead of the 325i AFM didnt affect the cars running in any way what so ever??

wouldnt a given airflow be the same on either meter,cant work out your logic in reducing airflow because ecu is mapped?

what chip are you running?comp ratio etc?

[liam012]

i was working on a logic that m30 afm causes a lean mix , hoping a smaller AFM would cause richer mix.

525e bottom end, 320i head, 268.268 cam, bbtb, 6 branch, 2.5 injection and air system, ants 2.7 ecu.

my mainissue here is that the 320i afm makes no differenced to the running of the car at all, if not then why bother having different, bigger and smaller ones for 320 and 325?

[m-dtech]

question............... does the chip take into consideration the cam profile ? ? ?

if AFM isnt making a difference, it must be (IMO) ECU related.


i cant remember if the m20 runs without an AFM connected ?

[Turbo-Brown]

Think I'd argue that, without at least a Wideband O2 sensor, you can't definatively state that the 2.0 AFM hasn't made any difference.

If you think it's running lean, why not try adjusting the spring in the AFM or something having first made a note of where it started. Again though, it's pissing in the wind if you don't have data on what changes have been made to the fueling.

Of course, it could just be that the ignition's too far advanced.

[chu346]

What cam you got?

I got a simular setup with no problems with pinking, but i do have a 272 cam.

320 head/325i valves
dbilas 272 cam
eta stock rebuilt bottom end
zone chip
BBTB

So i should be having approx 10.2 c/r

From what i've read the higher duration cam reduces the effective c/r slightly.

[Demlotcrew]

Come on guys the ECU doesnt take a signal from the AFM in WOT

[liam012]

andrew - thats excellent news
that explains it
thanks

[chu346]

Come on guys the ECU doesnt take a signal from the AFM in WOT

True.

Does this ever happen only at full throttle Liam?

[liam012]

well yes if i put it to the floor or anything more than half pf pedal travel in low revs 3 4 or 5 it will pink audibly until 3500rpm after which it dies of though the car is louder i suppose it could still be pinking but not as much.
if i barely accelerate it will pull clean to 6500.

[daimlerman]

What grade/type of fuel are you using?When I fitted my 2.7 I decided to use only super,my arse dyno tells me that the car runs better on BP Ultimate/Shell top grade rather than standard.Are your spark plugs a nice brown colour?Or a orrible black?

[Demlotcrew]

If his car is pinking i would expect the plugs to be white/silver in colour.

I would try to add extra fuel in not restricting the air. (which i guess will do the same thing)

Its just that you can measure how much more fuel is getting in better than how much air you have restricted.

Andrew

[chu346]

could this be a dodgy tps?

[liam012]

50 pounds from dealer last week is the tps
set up right too
i was sure the pinking is because of a slightly too high comp
ant has suggested i get round to fitting the megasquirt which i got last year.... havent had time
the poinyt of this thread was my suprise at AFM not effecting pinking or engine running.

however i would of thought that pinking would have got worse up from 4000-6500rpm if the timing was too advanced? not down in the low under load

i am reading up as much as i can on all this pinking and detonation and pretty much how the basics of how engines combust fuel and i am not getting my head around it all 100% as i i presumed just removing air or adding fuel to the mix would improve my pinking problem but now it must be the spark as well but only at certtain revs, this is making the whole thing three dimensional as you have to plot the timing of the air and the fuel

more studying for me i think

[Andyboy]

however i would of thought that pinking would have got worse up from 4000-6500rpm if the timing was too advanced? not down in the low under load

Not at all - low speed ignition advance is critical depending on the compression ratio and cam profile. Back in the old days when cars had distributors you had a vacuum advance unit which took manifold vacuum to a capsule on the distributor which advanced the timing under light and part load to improve throttle response. The more you opened the throttle, the less the manifold vacuum became and the vacuum advance unit would stop working as the centrifugal advance unit took over. A lot of performance orientated engines didn't have one at all, everything was done on the static and centrifugal advance - basically the faster an engine runs, the more ignition advance it needs. Don't forget the spark happens just before TDC. It sounds like you may have too much low-medium advance and the ECU needs remapping on a dyno - but maybe there's just not enough fuel, who knows?

An ECU remap SHOULD take into account the different piston speeds of a longer stroke engine. On a 2.7 the piston is going to get to the BTDC point a fair bit quicker than a 2.5 so unless the timing is altered, the spark is going to happen at the wrong place.

The TPS has a 'full throttle' switch inside which tells the ECU to inject max.beans.

[Speedtouch]

How about trying an octane booster additive?

[Ant]

The chip supplied is correct for the stroker 2.7, the pinking should not be related to the timing advance curve.

Liam, break out the LM-1 and log the AFR's dude, the tailpipe adapter may look a bit heath-robinson but it sure works well.

MS, MS, MS, MS you could spend weeks with moronic, you've done the break in miles now, time to get the jack outa the box M8, then you can truly tweak to get to the bottom of this.

Still feel the CR is possibly a little high.

[liam012]

Still feel the CR is possibly a little high.

is that too high a in not workable with or just too high for motronic to deal with but will be ok with MS?

will get the lm-1 on it today

[liam012]

ok its lashing down today so no massive speeds but enough to give an idea of the afr's first afr is cruising afr at 1500rpm (very small ammount of throttle) before i put the foot down. the next afr is what it drops to the second i floor it at 1500rpm and the last one is afr at 3500 rpm:

3rd gear: 12.4 11.0 12.1
4thgear: 12.6 10.7 12.0
5th gear: 12.6 10.9 11.5


oh bugger just relsied thats with the 2.0 AFM, will go out now and try the 2.5.

[chu346]

hmmm rather rich

[liam012]

ok here is it with the 325i AFM:
(again cruising @1500rpm afr , then WOT@1500rpm afr, and lastly WOT@3500rpm afr:

3rd gear 14,3 12.4 13.6
4th Gear 14.6 12.6 13.6
5th Gear 14.3 13.8 13.1(@3000rpm)*

*But with 5th gear even though it only drops to 13.8 at WOT at 1500rpm by the time i hit 2000rpm it has dropped further to 12.3 at 2500 its 12.8 at 3000 13.1
and fifth gear was pinking for the entire WOT run (not nice), fourth gear was pinking for first half of the run and 3rd only barely at the beggining.

[chu346]

is your cam timing spot on?

[Demlotcrew]

12.3-13.1 is good

Mines runs 12.9 in WOT all the way to 8500k

And 16.3 while driving part throttle.

Can you get the plugs out and take a pic?

Andrew

[liam012]

[Ant]

Hmm, difficult to say, mix looks OK, maybe a tad hot running going from the electrode ceramic.

last pic looks a bit salt n peppered looking ??
What plugs Liam ?

[liam012]

bosch W7DCR

out of the 6 plugs that is the only one with a black dot on them is that what you mean? or a miniscule sandy residue? as they all have a bit of that
interesting to note that plug number 4 was wet with petrol though car stood up for 2 hours.

enjoyed troubleshooting today (if that makes any sense!) and given me the enthusiasm to install ms next weekend for definate,

will it enable me to work around the high compression?

[Ant]

bosch W7DCR

BPR6ES

[liam012]

maybe so ant but i think its not that crucial in respect to the problem/complaint?
or is it?!!

[Turbo-Brown]

If they're getting too hot, they could easily be the cause of your problems!

[liam012]

you think they could pe turning into glow plugs causing pre-ignition?
mmmm i dont know

i thought bmw reccomned W8's but a plug that extracts heat more causing lower operating temp would actually be W9? I in going for the W7 have actually raised operation temperature?

Sorry to go on about the bosch's but old stock NGk are 3 days away, i am most eager to see if it is the plug! is there such a thing as W9?!!

[liam012]

Use Bosch W7DCR's. The higher the compression, the higher the combustion temperatures so you'll need a cooler plug. These plugs were used in the original high compression 325i (chrome bumper like Simon13 says) and the Alpina C2 2.7. They are physically a similar plug to the later one but the ceramic core differs so that it dissipates more heat. As long as the fuelling and timing is correct, it's the spark plug that regulates the combustion chamber temperature - wrong plugs lose power.

[liam012]

Now I AM confused.

w7dcr cross references as bpr6es

i find it hard to beleive that this spark plug could be the cause of the problem.

[Ant]

TRry some NGK BRR8ES Liam, I ran those with the Turbo, no issues at all, even the gaps stayed within spec between services.

[liam012]

will do - thanks for keeping an eye on this Ant. appreciated.