RPI Air Scoop Intake

[Mr Whippy]

Awww, it's only for the M or facelift models

Never mind.

Had a read up on it, the testing methods I've seen where it got 6bhp are err, questionable. I agree I wouldn't do much better, but I'd try remove the question marks over adaptation a little bit more! (more and more power the more runs it had, despite oil temp and coolant temp etc changing over that time as well (enough to cause more optimal operating/fuelling conditions anyway!?))

Hmmmm

 

[sammyz]

The RPI results look impressive but i'm always sceptical about large power gains claimed for simple design alterations. you would assume the manufacturer would have explored this sort of adaptation if it was that simple?

 

[pvr]

I don't know - a replacement airfilter gives a good result as well which is not done by the manufacturer?

 

[Aliv6]

I've seen RR results fiddled so many times...run in diff gears, more air in the tyres etc...I'm very dubious.

 

[Mr Whippy]

I've seen RR results fiddled so many times...run in diff gears, more air in the tyres etc...I'm very dubious.

Exactly. For the CSL, BMW added a huge carbon plenum, re-tuned the ECU and modified the exhaust, for only maybe 30bhp more.

Lets remember that BMW are using engine dynos too, not in-car @ wheel dynos where things like engine oil/water/intake temp vary constantly, gearbox oil temps, diff temps, tyre temps/pressures.

I'm not saying there are not improvements to be had, but I do think many tuners don't do a very good job of proving them without leaving huge gaps in their methods to draw doubt from!


Basically, I'd want to prove everything myself independently using several methods, before I believe it. Because the tuner simply won't (I wonder why half the time!)

 

[Beedub]

im a bit of a fan of rpi, so no bias here just my opinion, i decided to take my grills out and have a look, and imo bmw spend millions developing parts for a reason, exhausts for exampe that arn't to loud yet a compromise betweem looks, sound ,performance and longevity, ect ect now i looked at the stock scoop which is a wierd shape, but i had to think why would bmw make this in that wierd shape, imo i looks as though the standard scoop is made how it is to shield water being ingested via the scoop, im not saying even in extreme rain this would be the case but im sure their is an instance where the stock scoop would allow air in but keep water out. maybe im barking up the wrong tree just how it seems to me.

 

[Mr Whippy]

Water ingress is always a concern. The manual says you can drive in 12" of water with the Z4, which is quite a lot!

There are some intake systems that have low-slung ram-air systems. The E60 M5 for example has a standard looking top-intake like the Z4, but also a ram air intake from the lower bumper side intakes. I'm unsure how these work as a pair, but it's likely that if the lower one is submerged then of course the open top one draws the air alone... however, I'm not sure if this then means at high speed the lower ones pressure is lost out of the top one...
Maybe some kind of system is incorporated that is controlled!?

Either way, bending a flap around to point fowards maybe not always be effective. You are improving the cross-section of the intake to the incident air, but you may well have now moved the nozzle opening from a location of higher air pressure within the frontal air-dam of the vehicle, to a lower pressure one.
A manometer in the intake opening, and then one at the dirty side of the air filter, before/after, at varying road speeds, would be a good way to determine if there is actually any more pressure there reducing intake pumping losses.


I'm a fan of tuning cars, but so many 'tuners' just sell snake oil that looks like it should work, for a small fortune, often tested dodgily, and in almost all cases, will NOT offer better test results or independent ones, to back up their claims!

Dave

 

[wooter]

The RPI scoop replaces a plastic "scoop" that actually seems to block water and air from the grille, so air is only taken up in the engine bay, behind the left side lights. When you remove that OEM scoop, the intake has a free flow between the area behind the grille and the radiator. The RPI scoop is pretty much a bit of painted and folded sheet metal which deflects a bit of incoming air from the grille to the air inlet, instead of letting it flow through the radiator.

Sure I haven't measured it, but I don't think there is a higher pressure air bubble behind my left xenons which feeds my car more compressed and cooler air than the air in front of my car...

Come to think of it... I'll have to look for it later, but if the air does not come from behind the left xenons, it can only come from... the top of the OEM scoop which gives not much clearance to the rest of the car... Seeing the filter housing and tubing I would then expect the engine to be suffocated

 

[Mr Whippy]

I'm not sure how it looks on the M model, but in any case, I doubt in these days of emissions legislation and efficiency chasing, that what BMW did was in any way foolish.

I would be surprised if BMW decided to locate the intake trumpet in a low-pressure area. Remember, incidence angle/aspect of the trumpet is not at all proportional or relative to the pressure at the trumpet if it is located simply in a static air volume under pressure. Most cars have their intakes located feeding out of the air-dam area, since the pressure in that area is high all over. Air enters the front of the car and gets trapped, and pressure builds. The zone is of a fairly homogeneous high pressure. You could point the trumpet backwards and it would still 'see' the same pressure it did pointing forwards.
At low speed there is no incident air so it is irrelevant when stationary, and as speed builds, the overall building air pressure is what generates reduced pumping losses from the intake system, not the incident air on a relatively small aspect feed pipe with a small inlet to trunk ratio. OK if the scoop was about 20cmx20cm and fed down to the stock intake, but it's not. The frontal air intake however, of the car, IS a large area, and then it all hits a radiator assembly from which it cannot easily escape. A volume of high pressure, and inside that, any trumpet in any orientation will take in air at that same high pressure!


Perception is no replacement for measurement... I would be hugely surprised if even 5bhp can be found by turning a bit of plastic around... BMW engineers need firing if they lost 5bhp for essentially no reason!

Dave

 

[wooter]

The whole story and dyno's: http://www.zpost.com/forums/showthread.php?t=108101

Dyno: http://www.zpost.com/forums/showpost.php?p=2092595&postcount=104

Check out the original scoop and airflow ducting:
http://www.zpost.com/forums/showpost.php?p=2278384&postcount=288

I have the scoop installed and... It sounds nice, together with the BMC air filter... But I do feel I paid more for research time than for actual cost of cutting and folding a piece of aluminium I only happened to get the scoop and air filter because I wanted the skidpads, which I in hindsight could also have had made at a local metal shop...

 

[pvr]

Still not very expensive, which is why I bought it. Responses from others seemed positive as well, and the dollar was 2:1 ...

 

[Mr Whippy]

The whole story and dyno's: http://www.zpost.com/forums/showthread.php?t=108101

Dyno: http://www.zpost.com/forums/showpost.php?p=2092595&postcount=104

Check out the original scoop and airflow ducting:
http://www.zpost.com/forums/showpost.php?p=2278384&postcount=288

I have the scoop installed and... It sounds nice, together with the BMC air filter... But I do feel I paid more for research time than for actual cost of cutting and folding a piece of aluminium I only happened to get the scoop and air filter because I wanted the skidpads, which I in hindsight could also have had made at a local metal shop...

Hrmmmm, I just find it all hard to take in as a proof of concept.

A scoop pointing up in that location will see high pressure, as much as it would do pointing forwards, or down, or even backwards. Imagine just increasing the global atmospheric pressure by say 5% (on a high pressure day), and you add some power to a car for good reason. BUT, that pressure inside that volume of the car is high all inside that volume. That is the point of that volume being fairly well sealed, it gives a head of pressure for the cooling radiator and air-con radiator cores, and is also a great take-off for the air intake!

The fans on the dyno are unknown. Are they blowing significantly or not to generate a decent head of pressure for the OEM system? There is a good chance that forward pointing scoop is just effective at collecting a little extra air-flow directed at it by fans at zero road speed.


My problem is, they have one plot of before/after, on one car. Why not have a few test cars, and do five runs on each one before/after and do a correlation check? Is there just random noise here, or an actual pattern?
Any oil temp and water temp readings for each run so we can see if they were the same? Oil viscosity alone might alter the output by 4-5bhp, and water coolant temp might alter timing trim to alter power too.

They claim pressurisation improvements, but failed to meter the pressure in the air-dam around the trumpet and pre-filter (in the housing) before/after on a few different cars.

There really isn't much scientific method going on there, and little other data to cross-support the claims. This is from a company who specialises in tuning. OK, they might have made something that really does work, but surely they have this data to PROVE it to themselves? Cripes, I'd want to prove my own product to myself if I was to sell it honestly!

I'm still far from won over on this whole 'learning' ecu thing too. If they do do it, it should be fast. The pressure changes this flap makes are small fry relative to the boost given by getting up to 70mph, or turning into a strong headwind, or driving up the Stelvio pass doing the reverse...
Then we have issues such as engine oil temp/water temp etc causing alterations to ECU timings/fuellings which may well change the output.


Not saying it's not good, but I'm yet to see some conclusive proof of anything. Some data that suggests it might be good, but no proof.


How about doing 5 1/4m runs and taking time/speed before/after?

Some manometer readings?


All just balls. Dyno shops should know better to do such shoddy correlation work, and so should tuners offering products at this price imho!

Dave

 

[wooter]

Well, for the price, I don't expect 10 dyno runs on 10 different cars. Air pressure in front of the radiator is indeed high when driving, but a radiator is made to let air through, not to be a dam to have air flow upwards and to the right and down again into the air inlet.

If you would read the posts, you can read the dyno is done at 70mph since the fan is rated at giving air flow as on a 70 mph driving car.

 

[toplad]

If the scoop fed air straight in to the engine, it could make a difference, but it' pre air filter too

 

[Mr Whippy]

Well, for the price, I don't expect 10 dyno runs on 10 different cars. Air pressure in front of the radiator is indeed high when driving, but a radiator is made to let air through, not to be a dam to have air flow upwards and to the right and down again into the air inlet.

The radiator doesn't let THAT much air through though, by design, it's designed to let not all of it through so you get a pressure gradient through the radiator and air con rad etc to improve efficiency. If the air was stagnant on the back of the cooling matrix it wouldn't be efficient. You need pressure even as it is leaving the back of the radiators!
You simply wouldn't get a large volume of air through without pressure, since air would prefer to just not go through a dense mesh of aluminum fins... to get it to go through you capture air in an air dam, and let it pressurise!

That high air pressure volume will flow through any 'escape' to lower pressure at an equal rate irrespective of where the escape route is pointing within that volume, THAT is why BMW pointed the nozzle up.
gnore the 'flow' of the air on the front of the car. Once it is compressed up against the air dam, you could be pointing the nozzle back at the radiator and still retain most of the benefit of fitting the nozzle in that high pressure area. Ie, air will want to rush out to any low pressure escape (down in to the air box)


It is done by design. The illogical logic that RPI saw a problem with the upward pointing nozzle just shows how much they TOTALLY miss the point about the OEM design before they can even start changing it.
A simple assessment of the original equipment of anything before altering it seems a prudent move, because without a decent before/after assessment you cannot even know if you have hit your intended target.


All I'm saying is, do your own testing, and do it well. Chances are this is just yet more snake oil, but people seem happy to pay money for something that has the most shoddy proof backing it up... and no real logic within the bounds of what was there before, for it to even offer any improvement in power.

Dave

 

[wooter]

The problem is that for the money RPI is charging, you cannot even have one dyno run to test if there is really a difference. And even if there is a difference on a dyno run with a fan, it would range in the 1-4HP range, which is a speck, because not many fans can fake 70mph or higher of driving speeds. And if you would then point out you can do a realistic test on a closed track, you have the idiot behind the wheel who is not perfect and can perfectly unknowingly influence the result.

There is a problem with your air dam logic: or the inlet is underpressurized, and there cannot be pressure buildup because air is moving, or the inlet is not underpressurized and pressure is caused by speed and the size of the inlet. Since the RPI scoop is wider than the OEM scoop, it would mean that or the OEM scoop is limiting air flow into the engine while pressure builds up in front of the OEM scoop, or there is no pressure in front of the OEM scoop which means the RPI scoop will intake more and colder air than the OEM scoop.

I'd love to measure the air intake, but one of those devices costs multiple RPI scoops .

 

[wooter]

Since I got the air scoop, I was always driving the car quite hard and had no reference in regards to fuel usage...

Today I drove home in the rain with the cruise control, and for the first time my average consumption on the BC claimed I used 9,9l for each 100km. Sure, still no real reference since I cannot remember what my fuel consumption was the last time I drove back on cruise control with mild traffic, but rain and therefore a closed roof. But as far as I remember, it is the first time I see my fuel consumption drop under 10l. I did use the cruise control in similar speeds alot in the past, and always had between 10 and 11 liters of usage.

 

[daz05]

Do you really think BMW would miss an opportunity for increased power and mpg by manufacturing the air intake in the way they did?

 

[pvr]

uh - yes, as there are always costs involved for each improvement. That is why third party companies can make a living as not all components are optimal in the car.

 

[Mr Whippy]

Unfortunately I don't think this is where 'easy' improvements can be found.

The S54 has been phased out due to economy/efficiency rating. If they were throwing away 10bhp because a little bit of plastic pointed up instead of forwards, then they would all be fired.
When we used to have pancake filter housings with 1" inlets on a 2.0 4 pot NA engine running a carb back in 1990, then fine, loads of benefits to be found on intake systems.
But through the 90's mainly, the push for improved efficiency on intake systems, especially on a high specific output engine like this, means there would be little gain.

You only need to look at the CSL engine and the power rating change BMW give it for the mods done. If they could have got away with sports cats and an RPI alike scoop, they would have done, but it clearly (as in real life, not pretend) needed significant work to add power over the rev range!


Third party companies make a living because people like to think they are improving their car... as unfortunate as that is, 99% of what is sold is probably complete junk.

I would be interested to see if the new E90 M3 has an upward pointing duct in the air-cavity as well... I wonder why BMW keep on making this foolish mistake when RPI have shown the way with their +10bhp gains :wink: