Poorly Z4M, Idle bounce and poor throttle response/misfire

[pilchardthecat]

Since my car is my daily commutor i doubt i'll be able to pull my ECM (required for some of the testing i expect.... just had a quick scan of that doc, might get a chance to read it later)

"The ECM monitors a feedback potentiometer located on the actuator shaft (arrow) for actuator position/plausibility (closed 4.5v - full open 0.5v)."

If you can relate taht voltage to the data logger.

My expectation would be that "full open" voltage you would see either
- the actuator shaft/lever position at it's physical limit which is <100% WOT
- the actuator shaft short of it's physical limit implying that there is a decoupling of the physical range with the voltage range

there might be another pot on each individual throttle for which the same applies

 

[Alastair]

This is great, but Mods - should I start a new thread to discuss the original issues? As far as I can tell we are now discussing something quite different, though very interesting!

Being somewhat selfish here as I don't like my M being sluggish to rev from idle, and would love to get to the bottom if it!

 

[pilchardthecat]

This is great, but Mods - should I start a new thread to discuss the original issues? As far as I can tell we are now discussing something quite different, though very interesting!

Being somewhat selfish here as I don't like my M being sluggish to rev from idle, and would love to get to the bottom if it!

have they checked the idle (air) actuator? it's the thing that stops the engine stalling when the throttle closes (ie when you go from throttle open to coasting, and the fuel shuts off)

it should "un-actuate" when you get back on the juice.... it might not be

 

[Alastair]

Thanks Pilchard - no, they haven't - maybe that's worth a clean, appreciate the suggestion.

 

[SweetRide]

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: link removed 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.

You were given a hard time because you ASSUMED that our air intakes were the same as your Z3MC, which they're not. You're incorrect assumptions/data & lack of research are the reason you were given a hard time. Despite you thinking your 'DashDyno' has given you unequivocal proof of things, the bottom line is this: Air/Exhaust mods on our cars work if your TUNED for them. Meaning, real companies with real dyno's and proper equipment have put in thousands of man-hours researching the best method to take advantage of these mods. If you think the car manufacturer puts EVERYTHING on the table when it comes off the lot... you are sadly mistaken. Fyi: threats to leave and blackmail are a ridiculous way to redeem yourself, if that's what you're after.

 

[exdos]

You were given a hard time because you ASSUMED that our air intakes were the same as your Z3MC, which they're not.

I said: "when I first joined", and this relates to something completely different.

the bottom line is this: Air/Exhaust mods on our cars work if your TUNED for them.

The OEM ECU is capable of adapting to improvements in airflow and air volume entering the OEM intake, which is what I am attempting to achieve. I have no wish to go along the remap route. I prefer to spend my money on the suspension.

Meaning, real companies with real dyno's and proper equipment have put in thousands of man-hours researching the best method to take advantage of these mods.

I don't claim to be anything other than an enthusiast with an interest in understanding how my cars work. I'm not trying to sell anything to anyone. In comparison, there's an an awful lot of companies out there selling "snake oil" who make unprovable claims. If you don't like the information that I've given from datalogging with a humble DashDyno, then so be it; that's your choice.

If you think the car manufacturer puts EVERYTHING on the table when it comes off the lot... you are sadly mistaken.

I haven't made such a claim! It's obvious that manufacturers don't put everything on the table, that's why there are gains to be had by examining the OEM parts and then doing certain "tweaks" that the manufacturers probably already know about but have not done. Deliberate restrictions in the intake/exhaust systems are there for silencing reasons for their cars to get approval for importation, etc. etc. Likewise fitting properly tested aftermarket parts can achieve further gains too.

Fyi: threats to leave and blackmail are a ridiculous way to redeem yourself, if that's what you're after.

I have no need to seek redemption from anyone. Do you know what REAL blackmail is? You need a sense of humour transplant!

 

[Lower]

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.

The biggest restriction in those backboxes will be the two 180 degree bends that you've removed. What you've effectively done is create a plenum which will pressurise before the exhaust gases can exit the backboxes and will create a restriction of sorts, but may well be less of a restriction than the two 180 degree bends.

The optimum solution would have been to replace the whole back box section with a straight section of tube.

 

[pilchardthecat]

Oh god, don't upset him, some of us are really interested in his research! (Which really should be peer-reviewed..... by me )

 

[pilchardthecat]

On the exhaust "hack" front - i would like to know what the thing sounds like?

 

[deedub]

Come on now...This all makes perfect sense to me!! Keep up the good work fella

 

[sammyz]

Yeah, really think this is good stuff I do wonder what it sounds like with that sound deadening and pipework removed. My car sounds very bassy on tickover with a straight through back box set up.

 

[Lower]

Oh god, don't upset him, some of us are really interested in his research! (Which really should be peer-reviewed..... by me )

I didn't intend to be critical, just make constructive comment.

He's done some interesting work.

 

[daz05]

Does anyone else think Exdos could be the Doc from back to the future? I think the Eureka moment was fitting his flux capacitor into the intake.

Be a good laugh if you had a similar pic as your avatar.

 

[tomscott]

haha! Nice!

 

[Beedub]

im going to say this and politely leave lol, john..... i can see why you blackmailing us to vote for your pic...... its not very good

 

[ga41]

FINALLY have my car back! Low rev hesitation/response is now pretty much gone. If some still there then it's too minor to notice... Have yet to drive the car in heavy traffic to see if the idle bounce is still there but i don't think it is.

To reiterate i've changed/repaired the following and it could've been any combination of these, in no particular order:

• Replaced O2 Sensors with new OEM parts as we found that the ones i had on, which i sadly sourced myself thinking they were proper OEM parts, were not real OEM parts but OEM equivalent replacements. They might still have worked fine but we wanted to be sure.
  
  Valve timing was checked and found to be within spec.
  
  Cleared all ECU adaptations and reflashed the ECU in the newest version.
  
  Oil service performed with proper Castrol fluid and new air and oil filters.
  
  Fuel injectors cleaned as 3 of them were not squirting as much as they should.
  
  Spark plugs replaced. Even though they were barely 3 months old...
  
  Replaced #12 part from here because it was found to be broken. There's an internal spring that wasn't there when i first took the car to him. The BMW dealer i took it for a throttle actuator replacement last year must've screwed it up somehow. (No this did not cure the 76 degree throttle opening and no that rod is not adjustable.)
  
  ALL control valves in the engine bay were checked for correct voltages/current.
  
  Engine and exhaust checked for air leaks and airbox removed and reinstalled.
  
  OEM exhausts re-installed (made no difference so swapped back to my RPI's)
  
  MAF Sensor was basically 3 months old but had that replaced with another one just to be sure but no difference again so went back to the one i already had on.

And i'm sure a couple of other things that escape me at the moment. In the end what i'm most confident made the difference are the fuel injectors. Everything else seemed to be working fine otherwise and the car had no Check Engine Light or other fault codes to indicate anything else. One fault code did appear during its stay in the garage and that was a missfire on cylinder 6 but that got fixed when the fuel injectors were cleaned.

I haven't mentioned much about the throttle bodies not opening fully because after checking everything (sensors, control valves, actuators, connecting rods etc) on the engine the mechanic is pretty much positive that there's nothing that could cause that and that it's probably just how the Z4M's S54 works... He was contacted by another client of his with a Z4M Roadster that should be coming in for an oil service soon and he is going to check that car's throttle bodies as well to see if that one does it too.

Hope this has helped you guys and i'm sorry if this isn't clear but honestly it's been so long in the shop that even the mechanic isn't sure what was the single thing that alleviated the issue as he was both trying to cure the hesitation and to check why the throttle bodies don't appear to open fully...

 

[Shooter]

Fuel injectors cleaned as 3 of them were not squirting as much as they should.

How can a fuel injector become "cloged" as there is a fuel filter in the fuel pump ?

 

[ga41]

Fuel injectors cleaned as 3 of them were not squirting as much as they should.

How can a fuel injector become "cloged" as there is a fuel filter in the fuel pump ?

What can i say? Perhaps our gas is dodgier than yours.

 

[Beedub]

if anyone needs some nearly z4m stock injectors, let me know ive got a set

 

[exdos]

Does anyone else think Exdos could be the Doc from back to the future? I think the Eureka moment was fitting his flux capacitor into the intake.

Be a good laugh if you had a similar pic as your avatar.

I've been dubbed Professor Pat Pending from the Wacky Races before for my interest in finding ways to mod air-intakes and silencers

Which is it to be? Doc or Prof. Pat Pending?