Poorly Z4M, Idle bounce and poor throttle response/misfire

[daz05]

From what I have read on the US forums, the Z4M ECU is a far more advanced unit capable of more complex and quicker calcs, how that affects things I have no idea.

Again from reading, Evolve are the tuner to talk to.

My personal view is that the engine is the last thing that requires modification. Quickest way to improved acceleration is a shortened diff.

 

[exdos]

From what I have read on the US forums, the Z4M ECU is a far more advanced unit capable of more complex and quicker calcs, how that affects things I have no idea.

Again from reading, Evolve are the tuner to talk to.

My personal view is that the engine is the last thing that requires modification. Quickest way to improved acceleration is a shortened diff.

The Z3MC's ECU does calculations at every 6 degrees of crank turn: that's (60 x 7600) = 456,000 calcs per minute at the redline. I don't know the same details of the Z4MC.

I've known Imran before he started Evolve and I'm presently talking with him.

I agree that the engine is the last thing that needs modification. I've been able to provably improve the Volumetric Efficiency of the S54 engine of my Z3MC with some relatively simple mods which I've achieved for free (but a LOT of thought goes behind them 8) ) I've done this for the intellectual challenge in researching and understanding air-intake systems and for the pleasure of doing it and fabricating stuff. I was expecting and hoping that the same S54 engine in the Z4MC would also see an improved VE in a similar way, but unfortunately this is not the case.

Here's a link to some good detailed information about the ECU for the S54 engine except in the M3 CSL and E85/86: http://www.unofficialbmw.com/images/m3engineelectronic1.pdf It says: "The throttle opening depends on engine rpm and load (1000 kg/h maximum air flow)." I've been able to get the flow up to 34lbs/min (34 x 60 = 2040lbs/hr) = 927kg/h, so there shouldn't be any flow restriction at 92.7%.

 

[Beedub]

the z4m ecu is much more advanced than the similar s54 engined cars, its more closely related to the new m3 and v10 m5, its a very powerful unit.... unfortunatley its a very difficult to tune correctly and and too many "tunes" brick it completely and turn it into a paper weight.....

 

[exdos]

unfortunatley its a very difficult to tune correctly and and too many "tunes" brick it completely and turn it into a paper weight.....

I certainly wouldn't want to do that.

How have Simpsons managed to tune yours with a supercharger and fool the ECU into taking in more air, or have you got a different ECU fitted? Do you know if your throttles open to 90degrees at WOT and does your ECU say that the Absolute Throttle position is at 76% or is it 100%? If the limit of flow through the OEM throttle bodies is at 1000 kg/h maximum air flow, have you got larger throttle bodies to cope with the increased flow from the Supercharger?

Here's the details of setting up the throttles for the S54: http://tis.spaghetticoder.org/e46/M3_(S54)_COUPE/Fuel_system/throttle_and_operation/ I'm wondering if the throttle does only open to 76% (i.e. 68.4 degrees) if it is a simple adjustment of the pull rod required to ensure WOT is at 100% = 90degrees? It would seem doubtful though.

 

[Beedub]

unfortunatley its a very difficult to tune correctly and and too many "tunes" brick it completely and turn it into a paper weight.....

I certainly wouldn't want to do that.

How have Simpsons managed to tune yours with a supercharger and fool the ECU into taking in more air, or have you got a different ECU fitted? Do you know if your throttles open to 90degrees at WOT and does your ECU say that the Absolute Throttle position is at 76% or is it 100%? If the limit of flow through the OEM throttle bodies is at 1000 kg/h maximum air flow, have you got larger throttle bodies to cope with the increased flow from the Supercharger?

Here's the details of setting up the throttles for the S54: http://tis.spaghetticoder.org/e46/M3_(S54)_COUPE/Fuel_system/throttle_and_operation/ I'm wondering if the throttle does only open to 76% (i.e. 68.4 degrees) if it is a simple adjustment of the pull rod required to ensure WOT is at 100% = 90degrees? It would seem doubtful though.

i run alpha n management...... TBs open fully 90 degrees and TP is 100% according to data.... simpson dont tune the car, the car was tuned by AJ at ess tuning, the tune is art..... perfect AFRs, Perfect fuel management and injector cycles, the car runs better than it ever did stock..... I have a program which allows me to map switch or data-log remotely so AJ can tune my car while i drive Very cool.....little things like a valet map, so the car wont rev past 2000... lol!! The tune is very safe and all stock fail safes are in place

 

[SweetRide]

I can attest to AJ's tune @ ESS. My custom tune has perfect AFR's at 12.7 across the board. Evolve is still behind the game on our cars, but it's nice to have more choices than not.
And 'getting into the motor' will not only bring out the best out of any mods, it will ensure the parameters are set correctly to get the most from our S54. Not to mention, it will probably get rid of the OP's original issue (barring something being broken and causing it).

 

[Si.]

Hi,

Rather than start a new thread I thought I would post in here as it seems relevant.

I've only had my Z4MC for 3-4 weeks but 3 times now it's cut out on me for no apparent reason, no splutters or unusual noises but each time when either in traffic for when coasting to traffic flights or a stop. First time was the day I collected it so I just put that down to me getting used to it, it did it again about a week later, and again today when in traffic.

Stuck in traffic today and I noticed then when edging forward in a jam sometimes after a small distance when dipping the clutch the revs will drop to bellow normal idle levels. The engine seems to detect this at about 5-600rpm ish and picks it back up gain, is this normal? I'm guessing that the 3 times it's cut out had been when it's not caught the drop in revs and the engine has stalled.

Other than the above it's driving fine, no problems or issues I've noticed, although sometimes I do seem to get a "burst" of power at about 2k revs, again this might be normal and could be me still getting used to the engine.

Any thoughts?

 

[exdos]

Any thoughts?

If the car is just sitting and idling, it should not stall. If you bought the car from a dealer, you should take it back and get them to sort it out.
Or does the car stall because you've not yet got used to the clutch delay valve in 1st gear when moving off?

 

[ga41]

Si., NOT normal. That's exactly what i've experienced.

 

[Si.]

No it idle's fine, steady as a rock, it only seems to happen when crawling in traffic in 1st gear or if coasting.. It's only one it 3 times in 500+ miles of driving, and 2 of those 3 were when in traffic in 1st/2nd gear.

 

[ga41]

Again, that is not normal. Mine did that for the last few months but it never did that in the more than 2 years i've had it before...

 

[Si.]

Ok Thanks.. Will pop into the dealer at the weekend and speak to them about it.

 

[ga41]

Have them check your fuel injectors, i think it was what made the most improvement in mine as i had some out of specification.

 

[exdos]

Si,

Just a thought; have you done the "throttle reset" thing? There's nothing wrong with my Z4MC, but out of curiosity, I thought I'd see what it does the other day, and it certainly sharpened the throttle response.
Switch the ignition to Position 2 and count 10 seconds, then turn off and count another 10 seconds then start the car and drive off and floor it.

 

[Si.]

I've been reading up on that and it's probably worth doing, who knows what the last owner was like

Reading this thread and others, I'm still not 100% convinced i've actually got a problem, I've been running it on standard 95 ron so might be worth stepping up (I just sold my TVR and NEVER used 95 ron in it). I'm also not convinced that cutting out 3 times in 4 weeks is really a problem, I'm sure the 1st one was probably my fault as I literally stepped out of a TVR and into the BMW and it cut out within 5 mins of me driving it, so I defo put that down to me rather than the car. The clutch is very different to the TVR which probably adds to things.

I think I'll give it another few weeks and take more note of things and if it does it again I'll then get it looked it. Other that the 3 times the car id driving sweet, idle is steady as a rock when stopped, revs well when driving no blips or coughs or anything like that.

 

[BMWZ4MC]

Hi Si and welcome.

Mine does this once in a while. I don't remember when it first happened as it happens so infrequently, but it has certainly been this way for much of my ownership (since 2009). It seems to happen when stuck in traffic for long periods, (especially when wet). The other precipitant seems to be driving very gently after a really hard blast, and it is in these circumstances that it might (very rarely) stall. It does not happen when pulling away, but when the throttle is blipped in neutral or when the clutch disengaged after driving at low revs (sub 2k). It is as you say, when the revs die away it over shoots the normal idle position and then catches itself. I did have a lambda sensor changed last year and the frequency of this problem reduced significantly. The sensor didn't show an error code until the warning light came on, so I wonder if progressively it failed over thousands of miles (causing some rough running) until a threshold was reached and the light came on.

The burst of power at 2k rpm may be because the torque curve picks up around there. However, I have found with mine that if I drive at around 30 mph in third for a reasonable distance then floor the throttle there is a slight hesitancy before the engine picks up. Again, this has been as it is for a long time, and much older threads on here suggested that this hesitancy is normal and an artefact of the VANOS. IIRC Andy reassured me that his has done this throughout his ownership from nearly new. This hesitancy is not there when accelerating hard through the rev range from stationary. It is barely noticable in other gears presumably due to the torquier nature of the lower gears and the higher speeds involved at the same engine speed in higher gears.

If yours has stalled three times in 500 miles the problem is much more prominent than any issue with mine. I would suggest as others have that you take it back to the dealer in case something is amiss.

Out of interest, how many miles has you car done, and what fuel do you use. Some people have found theirs to run better with BP Ultimate rather than Shell V Power or Tesco 99, and the speculation above suggests this to be related to ethanol levels. I've always used Shell but I'm considering a tank of BP to see if there are any positive effects.

This is one of the threads I was thinking of, from last summer:

http://www.z4-forum.com/forum/viewtopic.php?f=9&t=29288&hilit=hesitancy

It seems many ///M drivers have experienced this and no dealer has managed to find the cause

 

[Si.]

Thanks for the info, the way you describe it fits exactly what I'm getting, today for example

It does not happen when pulling away, but when the throttle is blipped in neutral or when the clutch disengaged after driving at low revs (sub 2k).

That's exactly what happened today, and to add to it, it was chucking down which also matches your thoughts on it happening in the wet.

Car has only done 32k miles from new and I don't standardise on a specific fuel, but so far it's always been standard 95 ron

I'm not too concerned about the 2k power increase, again, that's just me getting used to the feel of the S54 compared to the 4.0 Speed six of my TVR. The TVR designed Speed Six engine had a very even torque curve over the rev range.

I bought the car from a specialist dealer rather than a AUC from a BMW dealer so not sure how helpful they will be with an obscure issue like this (if it's an issue at all) but I'll pop it in to them at the weekend.

 

[Adam D]

Morning all!

Some very interesting reading about the engine operation and potential limitations on the throttle opening.

My Z4M continues to be better behaved on the BP Ulimate petrol and is driving pretty nice with imrproved response. Double nectar points perhaps offset the price!

To satisfy my OCD I went and bought and fitted a set of Denso IXU 24 spark plugs (eurocarparts sell them for £12 each), I have had nice drivability improvements with iridium plugs on my previous cars and sometimes a small improvement in MPG so it made sense to give it a go incase the OEM plugs were past their best at 34k miles.



The old plugs didn't appear particularly worn but were blacker than I would expect which may be a result of it running rich, possibly from the old AFM although I would have expected them to self clean to a grey/brown colour now thats been replaced.

http://i105.photobucket.com/albums/m216/Adam_D200/Z4%20M%20Roadster/S54plugs1.jpg

http://i105.photobucket.com/albums/m216/Adam_D200/Z4%20M%20Roadster/S54plugs2.jpg

http://i105.photobucket.com/albums/m216/Adam_D200/Z4%20M%20Roadster/S54plugs3.jpg

Since replacing the plugs the car starts easier from cold. Engine response from light throttle depressions is now very good with greater immediacy and pulls very nice to redline with no flat spots; a very worthwhile improvement in my case as the car feels more grunty as a result for the price of a tank of petrol. Its too early to say if the MPG is any better but I would definately recommend them over the stock NGK's as a performance orientated plug. :driving

I did try to measure the resistivity of the coil packs with a digital multimeter but struggled to get stable readings, they were Bosch branded and not the infamous Bremi coilpacks which caused problems on early E46 M3's with the same engine. Pleasingly there was no oily residue in the plug wells.

 

[exdos]

I managed to do some more datalogging of my Z4MC a couple of days ago and this time I did several recordings of various different PIDs (Parameter IDs: i.e. different sensors) in my attempt to understand the Z4MC's ECU operation. Each vehicle (make and model) will only allow access to a specific PIDs and some cars allow access to more PIDs than others, and I've found that the Z4MC allows access to the most of any car I've datalogged.

One of the most useful PIDs that you might be able to access is Air/Fuel Ratio (AFR) and I've never been able to access this PID on any car until I went through the available list on the Z4MC and was delighted to discover that there are 4 AFR PIDs available! Brilliant! So I did a 1-2-3 gear acceleration at full throttle, recording all 4 AFR PIDs and Engine RPM simultaneously. From the data, it appears that the fuelling is controlled by two separate AFR banks, each adjusting fuelling to 3 cylinders. When I graphed them all together, there is too much information all in the same area on the graph to properly see the information, so instead, I used the 2 AFR bank PIDs and calculated the running average (all done by Excel) of the 2 AFRs combined, so that I have just a single plot for the AFR during acceleration, which makes the information more accessible.

The graph of the datalog recording is below. The bit that really stands out to me is the fact that during 1st gear acceleration, the AFR is around 14.3:1, but during 2nd and 3rd gear acceleration the AFR is around 13.2:1. So it appears to me that the ECU has been programmed to restrict fuelling in 1st gear, presumably as a torque limiting method, to prevent wheel spinning, to obtain the optimum traction beyond the skill of the driver. I have noticed that under full throttle in 1st gear, the DSC of the Z4MC doesn't seem to intervene, whereas it will often do in my Z3MC, so I think that this would seem to confirm my observation. At some point, I will see if the DSC (off) or Sport Mode (on) affect 1st gear fuelling.

 

[ga41]

Have you tried running this again with DSC off to see if it the AFR in 1st gear changes?