The Desnorkal myth.......

[Jonttt]

I’ve bought some carbon air scoops for my 987 but before fitting I thought I would do some research on the infamous “desnorkal” of their passenger side air intake as it would be easier to do pre fitting of the scoops if I’m going to do it......

.........early research rang some alarm bells, then when I got my head around the 987 air intake system what I was reading on the internet in general was just plain wrong and misleading......there are posts out there which are based on fact / physics / logic / and testing but the majority seem to purely be based on “its a free mod you can do easily to your 987” with no consideration to the actual effects on the car.....

.....the facts which are often misstated / not understood in many internet comments / write ups are (based on a UK RHD car):

- both side intakes are actually....erm....intakes

- the drivers side is purely engine cooling ie cooling of the engine block by circulating air around it (not to be confused with water coolant cooling which is performed by the radiators at the front of the car) and it supplemented by an inline fan when the car is stationary / reaches a certain temperature to SUCK air around the engine block (not blow it out as many guides wrongly state)

- the passenger side is the engine intake ie for combustion with fuel to make the car go

- As such the passenger combustion intake is more complex than the simple engine block intake on the drivers side and it requires no fan to assist intake when the car is stationary / engine is off as the air intake is purely for combustion and NOT for cooling in any way

- the passenger combustion intake takes the following path into the engine......it passes a baffle, then enters a “snorkel”, then passes the MAF (Mass Air flow meter), then passes through the air filter and finally enters the combustion chamber

- one of the most crucial parts of this process is the air passing the MAF which measures air mass “ “The air mass information is necessary for the engine control unit (ECU) to balance and deliver the correct fuel mass to the engine. Air changes its density with temperature and pressure. In automotive applications, air density varies with the ambient temperature, altitude and the use of forced induction, which means that mass flow sensors are more appropriate than volumetric flow sensors for determining the quantity of intake air in each cylinder.”

- crucial for the MAF to work properly is a constant stream of steady air past its sensor

- Porsche designed an air intake prior to the MAF to ensure that a steady, stable stream of air passes the MAF.......this was in the form of a BAFFLE and SNORKLE 

- if the BAFFLE and SNORKEL are removed then the air flow past the MAF is not stable and the MAF will more likely produce false readings

- if these readings are beyond tolerance (or the MAF is faulty) then the EVU will default to “default” MAF readings......these however are less efficient as they are designed to protect the engine from overheating in the combustion chamber ie if the MAF reads outside of engine tolerance then there is a likely to be under or over fuelling ie lean / rich fuel mixtures for the mass of air its actually being mixed with which can result in engine damage from overheating in the combustion chamber........

- ,most likely if the BAFFLE and SNORKEL are removed the MAF will either run rich or lean or on default settings ....

- default setting usually = worse MPG and a reduction in BHP 

So bottom line it appears to me at least that the science says do not DESNORKLE as this effectively means removing both the BAFFLE and Snorkel ........logic says Porsche designed and put these int here for a reason............I think part of the problem is that the BAFFLE appears to actually block air flow completely when it does not.......it is designed to “shape” the airflow into the Snorkel to ensure an even constant flow of air past the crucial MAF so that it can take reliable Mass readings for the combustion process....

its been interesting research, not least by the amount of rubbish posted on the internet about this mod......brought back a lot of memories of my BMW days when I spent a lot of time trying to replicate the CSL induction intake into the S54 engine block of none CSL cars......impossible to replicate without an “alpha N” remap as the CSL has no MAF due to the none baffled intake process required to create one of the best induction noises ever made............

.....it will be interesting to see the results of fitting the GT4 style (they are smaller custom made units for the 987 I will be fitting) intakes......at first I got worried that in effect causing more forced air induction would have the same net effect on the MAF readings as  removing the baffle but logic says that the GT4 works with basically the same setup and so it must be possible to increase induction but in a controlled stream of air via the BAFFLE and be fine...

Every day is a school day and all part of the process of understanding the mechanics of the 987 😉

 

[usman10316]

Very interesting read - there was a post on the internet where someone dyno'd their car and actually got 5BHP from removing the snorkel. 

I think most people will remove it just to get better sound, the drop in MPG or even BHP would appear to be very minimal if it hasn't been noticed - in fact most would attribute a drop in MPG to having a heavier right foot!

[edc]

Isn't the MAF after the air filter ? 

The MAF can't run rich or lean, it doesn't use any fuel but it is crucial for the fueling strategy as the demand for fuel is based on the air coming in.

It is easy to monitor whether the car is lean or rich, you can stick it on a Dyno and use a lambda probe. Running lean or rich is always a consideration for any tuning which is another benefit of a Dyno run as you can monitor the effect on the AFR through the rev range. 

The ECU has some preventative measures to prevent damage if there is a too rich or too lean condition. Knock sensors will retard the timing and you can also see a drop off in power. 

[Paul P]

Have done zero research but I am surprised that the MAF is before the filter  

suely the idea is to measure the actual flow rather than the theoretical. 
 

 

[Jonttt]

1 hour ago, edc said:

Isn't the MAF after the air filter ? 

The MAF can't run rich or lean, it doesn't use any fuel but it is crucial for the fueling strategy as the demand for fuel is based on the air coming in.

It is easy to monitor whether the car is lean or rich, you can stick it on a Dyno and use a lambda probe. Running lean or rich is always a consideration for any tuning which is another benefit of a Dyno run as you can monitor the effect on the AFR through the rev range. 

The ECU has some preventative measures to prevent damage if there is a too rich or too lean condition. Knock sensors will retard the timing and you can also see a drop off in power. 

Yes after referring to the parts diagram again the MAF is after the air filter....

I

I should have paid more attention after reading that it was before.......part 2 is the Snorkel so intake side on the above diagram......therefore the order is......

Passenger side intake grill —> Baffle —> snorkel —> Air Filter —> MAF —> Combustion

So that implies that the airflow past the MAF would be controlled more by the air filter (ie type and clean/dirty) than the BAFFLE and SNORKEL..........? Which does full circle to why did Porsche fit the baffle and snorkel ???????

ps I did not imply the MAF needed fuel (or did not intend to imply that), from memory it is in simple terms a wire with a current which is used to measure air mass passing it 

So back to the DeSnorkey myth......do I or don’t I before I fit the scoops ?????

[Christopher2110]

No issues with mine! Albeit on a 986 not 987

 

But you can always put it back on if you happen to change your mind? 

[phazed]

Porsche, research and development, millions of pounds/euros etc, I would leave well alone on a standard engine.

Why change something that has been designed for max power and economy on a standard engine?

[edc]

11 minutes ago, Jonttt said:

Yes after referring to the parts diagram again the MAF is after the air filter....

I

I should have paid more attention after reading that it was before.......part 2 is the Snorkel so intake side on the above diagram......therefore the order is......

Passenger side intake grill —> Baffle —> snorkel —> Air Filter —> MAF —> Combustion

So that implies that the airflow past the MAF would be controlled more by the air filter (ie type and clean/dirty) than the BAFFLE and SNORKEL..........? Which does full circle to why did Porsche fit the baffle and snorkel ???????

ps I did not imply the MAF needed fuel (or did not intend to imply that), from memory it is in simple terms a wire with a current which is used to measure air mass passing it 

So back to the DeSnorkey myth......do I or don’t I before I fit the scoops ?????

I think you've over thought it and gone down a bit of a rabbit hole. The MAF could never be before the snorkel as there are several items after in the inlet then to disrupt the reading and also if you use a cone type filter or induction kit the MAF would just be in free air.

I would go back to the 986 as the set up is the same. Air intake on the nearside and engine fan on the offside. The common cited reasons for the snorkel are NVH or sound, safety ie supposedly to prevent cigarette butts flicked out setting fire to the paper filter. 

[Jonttt]

Interesting that the baffle plate is officially called the “impact absorber plate” as per part 3 on the parts diagram.....

[Jonttt]

5 minutes ago, phazed said:

Porsche, research and development, millions of pounds/euros etc, I would leave well alone on a standard engine.

Why change something that has been designed for max power and economy on a standard engine?

Ah but cars have to be setup in many terms to meet various criteria other than optimal.......that is the beauty of modding.......so I’m not averse to modding......in fact I’ve never had a hobby car that I have not “modded” from standard spec............the sole issue I have is that I like to understand the what the mod will / will not do 

plus the scoop mod I’m doing will be semi permanent ie could be removed but not in the sense of on/off/on/off 

[edc]

I think the R&D line is all well and good but people mod to various extents for a whole load of reasons. You can improve a car and make it more suited to you. It just may not be what the OEM thinks the mass market wants. 

[Jonttt]

Just dumping info here for future reference.....

”The engine intake air is forced to flow around a deflecting distance plate, as a result of which water and particles are largely drawn off via the water drain at the bottom"....thereby protecting the hot film air flow sensor from failures resulting from the intake of ultra fine particles." Page 2.10 Service Information - Porsche.....

the water drain tube is item 12 on the diagram above

so that implies it helps remove air particles that would otherwise pass through the air filter ? And would explain why Porsche did not simply fit a mesh to stop larger objects......

Again I know from experience that a recognised none official service item on higher mileage sports cars is to clean the wire on a MAF as it can get contaminated with dirt even after the air filter 

[bally4563]

Is it not that the 987 air box is a proper air cold induction, hence it was fitted on the 986 LE run out to give more power? And removing the snorkel could increase air temp from localised hot spots?

[edc]

2 minutes ago, bally4563 said:

Is it not that the 987 air box is a proper air cold induction, hence it was fitted on the 986 LE run out to give more power? And removing the snorkel could increase air temp from localised hot spots?

No I don't think so. If you remove the snorkel it is still sealed to the wing and their still comes in the same way. The 986 is exactly the same, just the airbox itself is smaller with a smaller filter area. Both route air directly from wing into the filter box. 

[Mattman42]

The baffle was supposedly added to stop the ingestion of cigarette ends into the air filter for the US LHD market where they love a litigation. So many stories either way on the internet though, who knows how true that is either 

I’ve did the desnorkel approx 18mths ago and it definitely gives more noise around 4000rpm, no myth to that.

i ignored any claims of BHP gain as there was no evidence either way, and even if you did get 5hp, you’re never going to notice it.

any reduction in MPG is so minimal I’ve not noticed it wither

I have noticed more noise, which makes me grin more, so the extra gain of more smiles per mile makes it worthwhile to me and as others have said, you don’t actually alter, break anything, so it can be put back to normal in 10mins if needed.

so as someone that has actually done it, there is no myth for me

[Jonttt]

I’m reading that removing the Snorkel means that hot air will get drawn into the combustion (presumably from engine side) rather than the preferable colder air from outside the car........which part on the above diagrams is the Snorkel ie if its item 2 on the first diagram is that not engine side off the engine firewall ?

[Lonewolfgjp]

I just removed the baffle plate and left the snorkel tube in place. I put a bit of mesh over the opening and job done.

Defo sounds better without the baffle plate and the bmc air filter, complements the pse nicely in the sound department 😂

I haven’t noticed any increase in fuel consumption or any strange running issues.

 I haven’t noticed any performance gains either👍

[Jonttt]

Yes I think I’m currently thinking definately not removing the actual snorkel but 50:50 on the baffle plate.......sensible head says remove the baffle and run the car for a bit before deciding and then fit the scoops but impatient head tells me I want to do it today lol........I’ll try and be sensible and try running the car without the baffle and order some mesh in case I decide to leave it that way .......

I assume you just gorilla glue the mesh ie let it expand around the edge of the mesh to fix in place ? Ie you can make it a pretty permanent fix as even if you refit the baffle the mesh won’t do any harm still being there ?

[Nick C]

Hi,  if you look on YouTube for CADPORSCHE the guy 3D prints a part that fits perfect to the car and looks factory fitted, I've done mine and very happy with it, posted from U.S I paid about £24 and it came in about 1-2 weeks, I would order one rather than glue the mesh to the car. 

See what you think.

I've posted the link if it works. 

[witko999]

With respect, most of what you've written in the op is nonsense.

The baffle will have no effect on the accuracy of the MAF readings.  As you have deduced, it is most likely to discourage water from being sucked into the intake and to cause it to pool and drain instead.

I seriously doubt the other 'intake' is to blow air over the engine block.  This is a water cooled engine.  A small electric fan blowing at the engine block would make approximately zero difference to running temperatures.  Most likely this is to remove hot air from the engine bay for the longetivity of other components.

Fitting scoops to the side of the car will not generate any forced induction.  You would have to be travelling at something like 160mph to generate any positive air pressure in this way.  Even then, it would most likely be lost on its way through the air filter.

I wouldn't bother with any mesh.  It won't filter anything and will only reduce the size of the opening and the amount of air that can get through.  I personally would leave the baffle in place but I doubt it will be particularly detrimental if you want to remove it and fit your scoops.

[Jonttt]

6 minutes ago, witko999 said:

With respect, most of what you've written in the op is nonsense.

The baffle will have no effect on the accuracy of the MAF readings.  As you have deduced, it is most likely to discourage water from being sucked into the intake and to cause it to pool and drain instead.

I seriously doubt the other 'intake' is to blow air over the engine block.  This is a water cooled engine.  A small electric fan blowing at the engine block would make approximately zero difference to running temperatures.  Most likely this is to remove hot air from the engine bay for the longetivity of other components.

Fitting scoops to the side of the car will not generate any forced induction.  You would have to be travelling at something like 160mph to generate any positive air pressure in this way.  Even then, it would most likely be lost on its way through the air filter.

I wouldn't bother with any mesh.  It won't filter anything and will only reduce the size of the opening and the amount of air that can get through.  I personally would leave the baffle in place but I doubt it will be particularly detrimental if you want to remove it and fit your scoops.

The point of my post was to check my logic as I’m still getting to know the 987 car......it is achieving that.......I could not have bothered posting and continued to be wrong in my thinking......the whole point of my OP was to try to “cleanse” so much conflicting information thats on the internet ......one of the problems with the internet is that searches bring up results from many years....often that has been superseded by better /more informed information later........I was simply looking to use the better experiences of members of this forum to help me understand properly....thats the point of a forum right ? Ie already I think someone reading this thread will be better informed than I was when I started researching ;-).....as a wise man once said to me....the best way to learn is to get things wrong......I’m always prepared to do that but prefer to do it on “paper” first before practically.........therefore I contest that its none sense.......it is obvious not correct as later stated in the thread.....but to go back and edit it would I think be detrimental to the thread as a whole ?

re the drivers side fan assisted intake I was referring to the engine bay cooling....I tried to differentiate by referring to it NOT being about water cooling performed by the front radiators ie I just used the term engine block to mean the engine Bay Area but thank you for clarifying......

You have assumed I am fitting scoops for extra induction ....I’m not and I’ve never stated thats why I doing it .......I’m doing it for one shallow reason only ........I like the look of them...always have.....I wanted to do it to my 981 but partly never for the chance and also did not want it to look like a GT4 wannabe........I don’t think the 987 will suffer from that........logic says to me that it won’t detract from induction and if anything should increase it as its designed as per the GT4 to bring more airflow into the induction ........but thats not the reason I’m doing it.......my dilemma is simply that before I fit this cosmetic mod I want to decide whether to remove the baffle plate or not as after I won’t be able to change my mind without removing the scoops which will be semi permanently be fixed in place......

......I’m exploring because I’m always up for more induction noise but not at any detriment to the car.....the main reason I got a 987 over a 718 was because of the noise it makes.....making more of it is only good for me 

.....I think if I remove the baffle I will need some form of mesh ie the design of the scoops can only lead to an increase in objects entering the cavity where the baffle would normally restrict them ....ie its called an “air Scoop” for a reason ;-).....to not fit some form of larger object restriction before the air filter is just asking for trouble with scoops fitted I feel.......there can;t be any harm in doing so if you reverse the question why wouldn’t you ?

I’m enjoying the learning experience......a hobby car is more than just driving it to me....its about getting to know it and making it your own 😉

[edc]

Big debris like acorns, pine cones, twigs, feathers won't likely get past the baffle or mesh. But if it does you have a multi layer air filter. Small dust debris is not going to be stopped by a baffle but worry not because you have the aforementioned air filter. In days gone by when people routed cold air intakes in lower front grilles or fog light apertures you would often find dead birds, acorns and quite sizeable debris at the bottom side of the airbox. 

[Jonttt]

51 minutes ago, Nick C said:

Hi,  if you look on YouTube for CADPORSCHE the guy 3D prints a part that fits perfect to the car and looks factory fitted, I've done mine and very happy with it, posted from U.S I paid about £24 and it came in about 1-2 weeks, I would order one rather than glue the mesh to the car. 

See what you think.

I've posted the link if it works. 

Wow, that looks great.....I’ve emailed the guy at Cadporsche@gmail.com to ask him about ordering a black one ....thanks for the head up, I’d not seen that solution before......

It has got me thinking though ........there is a well known induction mod on the 993’s whereby you could buy / have option a “motor sound” air box.......it was basically the standard filter air box with holes strategically drilled in the side of the plastic moulding.......the well known mod is to simply drill holes in the side of the standard box and you get a better induction noise......so in the same vein as the CAD created mesh is only really holes in what would be the top half of the baffle would it not be an option to simply drill holes in the top half of the baffle ie to let more air straight through but otherwise let the baffle function as it would normally as a simple “impact absorber” for larger objects.........no doubt the holes would not let as much air through as the CAD solution but in effect be a halfway house between removing the baffle and fitting mesh and leaving it in place ?......plus with my solution with the Scoops fitted you will not be able to actually see inside the vents to see the cool looking Cad mesh solution...........great options to consider, thanks 😉

[Jonttt]

14 minutes ago, edc said:

Big debris like acorns, pine cones, twigs, feathers won't likely get past the baffle or mesh. But if it does you have a multi layer air filter. Small dust debris is not going to be stopped by a baffle but worry not because you have the aforementioned air filter. In days gone by when people routed cold air intakes in lower front grilles or fog light apertures you would often find dead birds, acorns and quite sizeable debris at the bottom side of the airbox. 

Yep been here done that.....try routing a cold air intake into a Z3m S54 engine to try and replicate a CSL induction system.....virtually impossible .....the most effective solution was using hoses through the front air scoops but you still had restrictions past the headlights etc...........its very very tight in there lol.............and yes I’ve pulled more than dead bugs to of air filters in the past.........Thats why I feel if your removing the baffle some form of mesh can’t be a bad thing, not to stop anything entering the combustion chamber but to stop it restricting the air filter 

[headless]

I took the baffle plate out ages ago and added mesh to the vent, using gorilla glue like you thought, little sound gain but I'm sure it breathes better cos the air does'nt have to go round the plate......