Poorly Z4M, Idle bounce and poor throttle response/misfire

[exdos]

So what's the necessary mod, the intake, exhaust or both?

I've given you 99% of the information you need. If you all vote here: http://www.z4-forum.com/forum/viewtopic.php?f=6&t=37000 for my for my photo so that I win this month's forum competition, I'll reveal the missing piece of the jigsaw and I'll also post more photos of my PY Z4MC. Otherwise, that's all you're getting on this. It's blackmail I know :evil:

I was given a hard time on this forum when I first joined. I did consider never posting again...

Great read by the way.

Thank you. It could be my last.

 

[daz05]

You have us all by the dogs danglies now Exdos. The mods will ban us if we vote like that it has to be fair, take a picture of the car with the missing jigsaw piece and you will win!

 

[exdos]

You have us all by the dogs danglies now Exdos. The mods will ban us if we vote like that it has to be fair

I know.

You only have to vote for my photo if you like it. :wink:

I will not change my sentiments.

take a picture of the car with the missing jigsaw piece and you will win!

The last photo I posted satisfies this requirement, although the missing piece is not in that photo 8)

 

[Gargybloke]

Loving the info and mods exdos.

Do you think the exhaust work you did had any effect and what was the noise like after?

I'm sad that anyone has given you a hard time on here. People brave enough to post new ideas and theories should be encouraged.

I'll have a think about the voting but I'm not sure two wrongs make a right :|

 

[exdos]

Do you think the exhaust work you did had any effect and what was the noise like after?

As a bit of background: I've spent a long time modifying the air-intake and exhaust system on my Z3MC and I've discovered a lot about air-intakes which is relevant to the S54 engine from the process. Most people "think" that the "ram-effect" has little or no effect whatsoever on cars operating at speeds below 150mph or so, but I KNOW that it does, because I've spent a lot of time monitoring and datalogging how playing around with zones of high pressure can significantly affect engine performance. I've seen what works and what doesn't.

In the case of my Z4MC, I made exhaust and intake mods in line with what I've learned, but they've been making absolutely no difference whatsoever to performance (good or bad) until I had my Eureka moment and realised why they weren't working. The problem isn't something that I've done wrong, instead, it's something OEM that was unexpected that I've had to modify to get my mods to work. Now that I've got this to work there are still other things I can do to enhance the ram effect some more.

When I took the Z4MC for the dyno run yesterday, now the mods are working, there is generally more volume to the driving experience and everything seems to resonate a bit better giving an overall better soundtrack to match the speed. Still some way to go though to match the "theatre" of my Z3MC.

I'll have a think about the voting but I'm not sure two wrongs make a right :|

I'm not trying to be Prime Minster in a dodgy ballot :wink:

 

[BMWZ4MC]

I'll have a think about the voting but I'm not sure two wrongs make a right :|

I'm not trying to be Prime Minster in a dodgy ballot :wink:

Cough, cough...(muttering) "George Bush!"...Cough, cough

I fitted the RPI ram air scoop some time ago and the OEM scoop is pretty small by comparison. That the OEM scoop points vertically upwards shouldn't be a problem since the area in front of the radiator is a high pressure zone, and this pressure will have an effect in all directions so forcing air into the scoop. However, the RPI scoop has a consideraably larger cross sectional area than the stock scoop, and it projects forwards into the mouth of the kidney grill (much as you home made scoops seem to do) so should gain the same ram effect but over a much larger area.

However, I did wonder at the time if there might be a further rate limiting step for air flow elsewhere.

This photograph of yours



reveals that the window behind the scoop into the induction system isn't terribly big. Is this of relevance to restrciting flow into the airbox?

As an aside, how relevant do you think is the closed (?air tight) nature of the OEM airbox when compared with the open trumpet of the GruppeM or the open airbox and cone filter of the aFe systems? Does the GruppeM lose the ram effect through it's open nature? The head of pressure that is directed through the window shown in the photograph above will dissipate into the engine bay with an open filter rather than being channelled through a sealed system to the filter with the OEM system. I'm sure the GruppeM / aFe have less restrictive filters and may even 'see' a larger surface area of air, but if that air has lost the ram effect, perhaps an open system such as these would lose power at high speed when compared with the stock system... I'd be interested in your opinion.

Oh, and what's the magic ingredient then?

 

[sammyz]

When you butchered sorry modded :lol: the back boxes you created a big space for gases to accumulate before exiting via the two rear pipes. Wouldn't this cause a real drop in exhaust pressure? :?

You obviously know your stuff but when I replaced the OEM boxes i went for single exit straight through boxes to try and keep pressure and at the same time remove the restrictive nature of the OEM design.

I also fitted the RPI scoop to improve airflow. Love this thread

 

[ga41]

Have the RPI scoop as well but damned if i noticed any difference...

 

[exdos]

I fitted the RPI ram air scoop some time ago and the OEM scoop is pretty small by comparison. That the OEM scoop points vertically upwards shouldn't be a problem since the area in front of the radiator is a high pressure zone, and this pressure will have an effect in all directions so forcing air into the scoop. However, the RPI scoop has a consideraably larger cross sectional area than the stock scoop, and it projects forwards into the mouth of the kidney grill (much as you home made scoops seem to do) so should gain the same ram effect but over a much larger area.

It's significant that RPI don't seem to produce any facts or figures to show that their scoops actually work for (m)any of the cars they make them for. Unless they've also had the "Eureka moment" then I expect that their scoops would do nothing for performance in the same way that I found with all my mods. I've trawled the internet to see if anyone else has had a similar Eureka moment, but then again, I haven't seen that anyone else has previously identified the problem of difficulty of improving performance of the Z4MC or the solution that I've come up with. There's not even a DashDyno users' forum either

As for the prices RPI charge for a bit of folded aluminium.! Mine cost £0

However, I did wonder at the time if there might be a further rate limiting step for air flow elsewhere.

This photograph of yours reveals that the window behind the scoop into the induction system isn't terribly big. Is this of relevance to restrciting flow into the airbox?

It was always my intention to discover the effect of each individual mod that I fitted with the datalogging. However, because I saw no significant change along the way, the gain I got yesterday is from the overall combination of all the mods I've shown and described, plus my "Eureka mod". I expect removing this trumpet under the bonnet would help in derestricting the flow, but it isn't the key part.

As an aside, how relevant do you think is the closed (?air tight) nature of the OEM airbox when compared with the open trumpet of the GruppeM or the open airbox and cone filter of the aFe systems? Does the GruppeM lose the ram effect through it's open nature? The head of pressure that is directed through the window shown in the photograph above will dissipate into the engine bay with an open filter rather than being channelled through a sealed system to the filter with the OEM system. I'm sure the GruppeM / aFe have less restrictive filters and may even 'see' a larger surface area of air, but if that air has lost the ram effect, perhaps an open system such as these would lose power at high speed when compared with the stock system... I'd be interested in your opinion.

I must be the world's No1 fan of the BMW ram effect air intake systems; they are works of genius, and I just can't believe the number of people who want to replace them with so-called "Cold Air Intakes" (CAIs). The OEM intakes which tap into external zones of high pressure ALSO tap into air at ambient temperature (the coldest air you can get without intercoolers!). Having an enclosure in front of the MAF is essential to harnessing air at slightly higher than ambient pressure (i.e. ram effect) and the more air at higher than ambient pressure that you can put in front of the MAF, the more that you can increase the Volumetric Efficiency of the engine, so something like a GruppeM will probably out perform an OEM air-intake on a static dyno but in real world conditions there will be a difference in favour of OEM, especially at higher speeds.

Oh, and what's the magic ingredient then?

I've stated my terms above.

 

[exdos]

When you butchered sorry modded :lol: the back boxes you created a big space for gases to accumulate before exiting via the two rear pipes. Wouldn't this cause a real drop in exhaust pressure? :?

Gas flowing through a narrow pipe flows faster and at LOWER pressure than gas flowing slower through a larger diameter which will be at HIGHER pressure. So the gas within the middle chamber of my butchered/slaughtered silencers will be at higher pressure than in the pipework inside the silencers. Whether this of any significance to flow, I don't know, but as I see it, I've shortened the length of exhaust through which the gases need to flow and eliminated the need for them to go through another 180degrees before they exit. Therefore, the engine, as an air pump, should have less work to do. Plus, the silencers are a few Kgs lighter.

I did similar mods to OEM parts of my Z3MC and followed the same principles and achieved very significant gains, which have been confirmed on the dynos at Evolve and Powerstation, as well as on my DashDyno.

When I replaced the OEM boxes i went for single exit straight through boxes to try and keep pressure and at the same time remove the restrictive nature of the OEM design.

I've found that the internal diameter of the tail pipes is a major factor in determining the loudness of the silencers, therefore a single tail pipe with the same area as the two tail pipes on the OEM silencers will be much louder. I don't want particularly loud silencers.

A big part of the fun that I get from the modding that I do, is doing it at no financial cost. I like the intellectual challenge of understanding how all this stuff works and then tweaking it some more with my own lateral thinking.

 

[exdos]

Have the RPI scoop as well but damned if i noticed any difference...

I should think you are right too.

 

[pilchardthecat]

I've just read this entire thread (which really should be split in two!)

Fascinating stuff, i'm desperate to know what the "eureka" moment was!

Great to see some real science happening and exposed in the true British tradition

 

[Alastair]

Very interesting.

I'm confused, though, as to whether this addresses the original topic (poor throttle response from idle) - it seems that some cars have this issue while others do not? So presumably it's a *fault* rather than something fundamentally wrong in the M's design?

Should we consider splitting the threads (as pilchard suggests)?

 

[pilchardthecat]

I think exdos deserve his own forum section to be honest. "Z4 Science". There aren't many people who invest so much time and effort into something (as a private individual rather than for profit). He's a rare breed even among enthusiasts.

A sticky at the very least! (assuming he deos the decent thing and finishes the "story"!)

 

[exdos]

assuming he deos the decent thing and finishes the "story"!

I've stated my terms, and some might not like them, but I'm sticking to them.

 

[Beedub]

exdos can you not try and link some pipework together to move the filter outside the engine bay??



all my intake is outside the engine bay, is this something N/A cars can benefit from, from what ive seen your the man that could make this work....

my filter is next to my headlight, the filter is HUGE... makes things alittle noisey....

also i missed a question from you earlier, yes the throttle bodies have been "bored out", Power n Tq are pretty nice, 11.5 Afr @ redline which for a FI s54 is Perfection with plenty of safetynet.

ignore the AFR on this graph the sniffer backed out of the exhaust...... note this was with methonal "On" this Wheel Hp, so over 550hp crank, or 485 WHEEL hp...

this is what the curves look like for a blown s54 with meth... a better exhaust setup should net 500Wheel Hp...

 

[exdos]

exdos can you not try and link some pipework together to move the filter outside the engine bay??

Bee,

Thanks for your suggestion, photo and all the other information - VERY interesting! I can see some possibilities with that arrangement, and in some ways, its a bit like the Z3MC arrangement,

Now that I've got my Z4MC to accept my mods, I can try some more ideas that I have. At present, I've only done about half the things that I've done to my Z3MC, and from the next mod that I do, I expect to see more gains. The Z3MC has a much smaller engine bay than the Z4MC so I'm hoping to put the increased space to more good use.

 

[pilchardthecat]

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.

What are the input voltages for the actuator? What are the output ranges for the potentiometers?

Is the 76% you mention based on the the physical position of the actuating shaft/lever or the input voltage on the actuator relative to it's maximum?

 

[exdos]

What are the input voltages for the actuator? What are the output ranges for the potentiometers?

I'm not an auto-electrician, I've only been data-logging; an altogether different thing. This link might tell you that information: http://www.unofficialbmw.com/images/m3engineelectronic1.pdf Are you able to help and can you explain all this for us?

Is the 76% you mention based on the the physical position of the actuating shaft/lever or the input voltage on the actuator relative to it's maximum?

The 76% I've mentioned is from information given by the datalogger and is demonstrated in the graph below (yellow line) which I previously posted. I've no idea whether it is related to input voltage or the physical position of the actuator lever or throttle plates. I was hoping that ga41 would be able to shed some light on this since his mechanic has investigated this. I've found that my datalogger will not yield any information from the Z4MC unless the engine is switched on, unlike other cars which seem to give information as long as the ignition is switched on. How can this be tested with the engine turned off because the drive by wire only appears to operate once the engine is running?

Since my Z4MC appears to be running perfectly, I suspect that all Z4M's have the same trait of recording Absolute Throttle Position as being 76% at WOT. I only know of this from datalogging. Would you be able to check your Z4M to see if yours produces the correct ranges of voltage for all the parameters you've mentioned?

Thanks in advance for any help you can give us.

 

[Paza3]

I agree a thread split is needed but only if the information of "how to" is released otherwise it’s to no ,benefit to the forum and its users. I would say Exdos the best result all round would be an increase on forum donation form fellow members would be the best thing all round for a release of information???

You would be bring new info and much needed donations to the group, but of course this would be down to you discretion. I only say as the last donation was the 8th of April Guys