SteveNotto
Member
aquazi said:
M brake ducts
- Thread starter cragswinter
- Start date
Cheburator
Member
exdos said:That's my whole point: the BMW engineers didn't leave much at all and I'm surprised that people on here say the Z4 MC doesn't use the "brake duct" as a cold feed into the air-intake system. But if that's so, I accept it. The BMW engineers have developed an enclosed air intake system which takes it's feeds from areas of high pressure, which they seem to have persisted with and developed in the E36 Z3 where the MC/MR has an extra intake located in the N/S "brake duct"; in the E46 M3 the intake is more complex where air inlets are located in both brake ducts and along the front bonnet edge. In the E92 M3, the inlets are even more developed where there's an additional one on the bonnet. BMW engineers have obviously realised that they're onto something with these designs.Cheburator said:That's a great idea. I am sure my M5 can do with a few extra ponies - I mean, them idiots at BMW left so much on the table, non?
Since the S54 engine is Normally Aspirated (sucking = negative pressure) how is that alfamale wrote: "" I could get max 0.1 psi at full throttle at 8k rpm no restriction in the OEM design so nothing to do here", when 0.1psi is a pressure greater than ambient at WOT? In that scenario, is the engine actually sucking air into it, or is it receiving air by very "mild" forced induction?
I will be delighted to accept if your offer is genuine and not merely an attempt to take the pissHowever, I don't use a butt dyno, I use a proper commercially available datalogger which reads directly from the car's ECU. It comes with bespoke software which works on a PC and all recorded parameters can be read and interpreted on screen. It also allows data export into other formats so that the information can be used in Excel to allow further interpretation in formulas to produce your own graphical presentation of the information. Provided your car has an OBDII socket it should be able to read whatever your ECU sees. I'm only reporting the information that datalogging produces, if you or others think that BMW, and all other manufacturers, install ECUs which tell lies, then so be it. Is your "tantalising offer" serious?
I have to admit that I did take the pee a little bit. In all seriousness the car will be mapped on a hub dyno. We cannot afford to take any risks with 12:1 compression and an ECU, which while good, is not as quick witted as modern ones. However, I am more than happy to offer rides in it if all works out...
The reason I took the pee is that you stated something as fact, while it was actually inaccurate. To your credit, you did not call names, and took the banter well. So a credit to you!
Btw, I had to fix a mildly frontally damaged E46 M3, which now belongs to my dad. I still think that it takes more than 75% of its air supply from the snorkel behind the bumper and not much from the brake ducts. The dynamic of air-flow tells me there is almost nothing going up the little vents...
Lastly, to feel any "ram-air" effect, you need to be doing silly speeds. And even then, given the shape of the S54 airbox and ITBs it is most certainly lost. Thus I had to make the
comments...
aquazi said:To play devils advocate..... i have just taken a pic of the M ducts lying in my garage:
They have the back half blocked, and have a vent on the top:
Dont understand the whole increase pressure bit though
And I shall play Devil's advocate even more by suggestive that since the brake duct is of reducing radius, as air passes from the open mouth at the bumper to the half-blanked exit in wheel arch that air must accelerate. The consequent pressure drop will actually entrain air through the grills into the brake duct as described so eloquently by Giovanni Battista Venturi :roll:
Cheburator said:
Using an ECU datalogger simultaneously recording, Engine RPM, Airflow at the MAF, Intake Air Temperature and Vehicle Speed, it is possible to calculate the operating Volumetric Efficiency (VE) of the engine at any moment in time, and so it's possible to see what effect blocking the brake ducts and fitting flippers might have on VE. Obviously, the ram effect is far more significant at high speeds but it DOES still affect VE at all speeds in relation to the "square" of the speed.
If you measure the air pressure inside a brake duct which is partially blanked at the back, you will find that it increases above ambient pressure with increase in speed, so where is the air going then? Think inflated windsock with a hole in the side: does air enter into the windsock through the hole in the side, or does it escape from inside the windsock through the hole?BMWZ4MC said:
SweetRide said:
So they work well?? There is lots of evidence of before and after on dynos over here that prove they make little if any difference. In fact in some cases a drop in bhp.
I personally welcome people like Exdos on here, someone who obviously has the skills to properly test the effects of induction etc.
cragswinter
Member
Makes sense to meBMWZ4MC said:aquazi said:To play devils advocate..... i have just taken a pic of the M ducts lying in my garage:
They have the back half blocked, and have a vent on the top:
Dont understand the whole increase pressure bit though
And I shall play Devil's advocate even more by suggestive that since the brake duct is of reducing radius, as air passes from the open mouth at the bumper to the half-blanked exit in wheel arch that air must accelerate. The consequent pressure drop will actually entrain air through the grills into the brake duct as described so eloquently by Giovanni Battista Venturi :roll:
So, still no definite answer as to whether you can remove them with the bumper in situ?
exdos said:
Firstly, you shouldn't confuse pressure with flow! The air needn't be "going" anywhere just because it's under pressure. Try sitting at the bottom of a deep swimming pool for a while if you want to experience pressure without flow.
A windsock is a very different flow problem, and there is much debate as to why a windsock does not collapse on itself. It is not a typical venturi as the walls are flexible, and the upwind mouth usually is held open with a rigid ring. Indeed, some designs without this support do collapse with the right atmospheric circumstances. Furthermore, you have neglected to consider what happens to the air travelling around the outside of this flexible cone. Since the outer surface is tapered, the air which travels passed accelerates tangentially to its predominant vector following the taper of the cone. This acceleration is accompanied by local pressure variations. You could even argue that a windsock behaves more like a constricted pipe than does a venturi, but I doubt you could offer a cogent arguement that would convince me to stop believing in Bernoulli's principle. Perhaps you have a better explanation for how the carburetors of my Westfield work?
By suggesting that a brake duct might act as a venturi, I was merely following the somewhat amusing direction of this thread. I have no doubt that the short, open mouthed duct is susceptible to significant ram effect, not to mention the inestimable consequences of turbulence associated with the various contours of the leading face of the car.
Out of interest, have you measured the pressure inside the brake duct of a Z4M at speed?
Anyway, I'm going to go and put on a pair of windsocks, the light is beginning to fail and my feet are chilly
To generate a ram air effect the duct would have to widen rather than taper. To create a static pressure you would need to slow the air down rather than accelerate it, which is what this duct would do.
An F1 airbox is a prime example of this. Relatively small air intake, opening outwards thereafter.
An F1 airbox is a prime example of this. Relatively small air intake, opening outwards thereafter.
Even by forum standards as nerdy 4 pages of b###ocks as i have read since the 16 pager on 'does a stubby aeriel reduce drag coefficients by more than the gravitational effect of the earth's rotation' debate,- think that was one of CJs
get out there and drive the things
get out there and drive the things
sammyz said:Even by forum standards as nerdy 4 pages of b###ocks as i have read since the 16 pager on 'does a stubby aeriel reduce drag coefficients by more than the gravitational effect of the earth's rotation' debate,- think that was one of CJs
get out there and drive the things
+1
Cheburator
Member
sammyz said:get out there and drive the things
Sold mine
But have the option to buy it back... sammyz said:Even by forum standards as nerdy 4 pages of b###ocks as i have read since the 16 pager on 'does a stubby aeriel reduce drag coefficients by more than the gravitational effect of the earth's rotation' debate,- think that was one of CJs
get out there and drive the things
I had a similar thought last night I must admit.
