De-bunking de-snorking

"It's the fate of many propositions, it's been said, to begin as heresies and end as truths ....." ~ some nameless and probably pilloried wise man. That said, here's my experience, and if I can figure out how I'll be glad to post the raw data files to the Cayman site for anyone who wants to download the viewer (available at Dynojet.com - Innovations & Performance Products from Dynojet.com ) to play about with as much as they wish. Pulled the outer body panel "grill" off Monday, the 16th, along with the "inner" intake panel which stands accused of presenting an "obstruction" to the ingestion of air worth, depending on the party opining, 10 - 14 bhp in power loss. I drove the car about without any screen installed Monday & Tuesday, then took it down to MAC Autosport in Parker, Colorado ~ 303/841-1176 if some one in the Colorado area wants to try this for themself or MAC Autosport Ltd. - Welcome to MAC Autosport for information on their dyno etc., this morning. I asked the shop to make four pulls, the first without the snork plate, followed by one with, followed by one without, again with and finally without the screen installed. The "snork/de-snorked" runs (if I can figure out how to post the raw data files to the Cayman site) are numbered #4, #5, #6 and #7. They were done approximately 10 minutes or so apart. Baseline Dyno Runs made @ August of 2006 on car when it had @ 4,000 miles on it and on 19" OEM Michelin PS2 tires ~ rears 265/35x19 ~ SAE adjusted for temperature, barometric pressure (i.e. altitude) and humidity: *** Stock no mods engine w/ OEM 19" tires 4th Gear*** RF-001 Aug06 258.31 bhp 220.54 ft/lb RF-002 " 258.21 bhp 221.92 RF-003 " 258.44 bhp 221.03 ********* 18 Jul 07 Snorked / De-Snorked runs, Stock engine now with @ 20,000 miles on it, Track wheels & tires on car, 18" BBS RS with 285/35x18 Goodyear Eagle F1's at 39psi (hot) ***** Run# snork RF-004 baffle off 256.95 bhp 217.82 ft/lb RF-005 " On 256.17 bhp 218.46 RF-006 " off 255.95 bhp 218.91 RF-007 " On 256.19 bhp 220.00 Summary: I don't see that the removal of the intake protection baffle adds anything to the cars ability to make power. If there's supposed to be a 10-14 bhp gain here, I don't see it. Based on the above dyno results, the presence or absence of the intake shield has no effect on the engine's power producing capabilities. I guess I better go get a flame suit on now :beer: BTW, if you don't think temperature and altitude make much of a difference (the dyno at MAC's is probably located at about 5,300' above sea level, and it's hot here right now), the "raw" uncorrected, actual horsepower / torque the car is actually putting to the ground in the Denver area on a hot summer day is @ 206.08 bhp and 174.69 lb/ft of torque (RF-004 raw, unadjusted to SAE data file.)

Was there any difference in sound?

Supposedly there is a period of time/mileage that the ECU needs to adjust to the newfound airflow, it doesn't look like you accounted for this in your testing?

This is very very likely not true. To test it, try restricting your intake, driving around for a while, then unrestrict it - you will see the improvement immediately.

Amazingly consistent runs on the dyno. When you put the plate back in did you have the outer trim piece installed too? Additionally, was any fan used blowing on the air intake to simulate driving conditions vs. just static air? I don't see 10-14hp gain here either, but then again you don't have the EVO intake to couple the de-snork with either. Not much time for the ECU to adjust either, if in fact it would adjust any amount based on plate in or out, which is speculation of course. So in summation did you like the sound difference?

The only other box stock Cayman that was run on the dyno before and after the de-snork that has been reported here (I think) gained 1 h.p. It was done by the same folks that work on Ken's car. The difference in sound may be the siren song persuading people of more h.p and better throttle response. It is nice to see another data point added even it is way down there at 5300'. Just think if you were in 7000' Santa Fe!

Has anybody noticed the shape of the restrictor/protector plate? Its right side is shaped so that it captures a larger mass of air while the vehicle is in motion and channels it up/forward. I'm sure that the design is not an accident and by removing it there is nothing in place to replace its functionality. Thus, in case you want to keep the original air flow/direction provided by the protector plate and get the de-snork functionality I would suggest drilling a set of well aligned holes on the plate around the area of the air intake.

I don't put a lot of stock in the ECU adjustment requirement, and note I ran the ECU and de-snorked configuration 1st and for 2+ days and over 200+ miles before putting the car on the dyno. If anything I think you might argue the power "difference" should have been exagerated by not allowing an adjustment/mileage time after the air flow was allegedly "cut off" by the reinstallation of the baffle.

Was there a fan blowing at the intake area at an angle to simulate driving condition?

There were fans present blowing from the front of the car to the back. I doubt however the fans in question at this particular facility (in fact at most every chassis dyno facility in the state with one, however it's no longer operating, exception) are even remotely capable of approximating actual road driving air conditions. Fan's capable of performing that feat would add thousands, if not ten's of thousands of dollars to install. IME, few dyno operators are willing to incur that additional expense and will tell you that they "... just need to keep enough air moving through the radiators to keep the car from overheating...." Makes dyno tuning forced induction cars in particular a bit more problematic. It is a potential issue, but not as dire a one IMO on naturally aspirated cars. Last, I may be making an unwarranted assumption, but you aren't indirectly trying to imply some kind of "ram air" effect for the presence or absence thereof of the in take shield?

It is an "Impact Absorbtion Plate". That is what Porsche thinks it is anyways. And removing it on a AS car has little to no effect, as evidenced by this thread. Only Speed Yellow cars derive true benefit. Most of the launch cars were AS. They are special ...

Nice Job! It's refreshing to see an analytical approach to performance mods instead of the usual bulletin board chatter. Thanks for sharing! P.S. Might not be a bad idea to scan the sheets from the dyno pulls and post them here for posterity.

Very nice job.

mlpor, thanks for the demo....I will now forget about doing it.

Some, but not so loud as to be significant to my ear.

You make a very good point F1. In addition to the features you mention, the (as someone else on this thread has referred to it) "impact plate" is also "tilted" from the front edge to the back, along with being surrounded by what amounts, on the "inside" edge to a "C" shaped catch pan, and on the outside edge of the "C" (think of the "C" reversed) what I think one could argue is in fact an aero shape that contributes to an even flow and distribution of intake air into the actual intake channel/throat. The closed "C" part of the impact plate looks to my eye like it performs a function in knocking down, capturing and diverting away from the intake anything in the intake stream, including water, with substantial mass. If it's not obstructing any airflow to begin with, I'm not sure that drilling and adding any additional holes to the flat plate part of the "impact diverter" gains one anything, and given the round design of the surrounding trailing edges of the piece, without study could in fact disrupt the smooth flow of air around the outer edge that feeds into the intake stack. Personally, in the absence of any indication the part in any way inhibits engine power as it now sits, I'm not inclined to mess about with further modification of the existing part.

I've downloaded or "added" a pdf format file showing a print of (1) an "old" original base line bhp file for the car, one of 3 runs done @ August or Sept of 2006 shortly after I bought the car; and two of the recent, one with (Run #6) and one without (Run #7), displaying the bhp curve only, the impact plate on the car. I'd be happy to post the raw "DRF" dyno data files, but the site rules apparently restrict the type of files that can be uploaded to jpegs, pdf etc. The raw DRF files allow one to add the torque curve(s), A/F ratios etc data also captured during the dyno runs, and acutally overlay the data directly on top of other runs for direct run to run and even (if you have DRF files for other cars, a 997 X51 3.8 liter engine for example) other cars. I'll PM Ken and send him the DRF files to make available if he wants to do that. Cheers, Mike

u took the words right out of my mouth, I certainly won't waste the time and possable screwing up getting the side cover vents off even. Hell if I want more sound, I will just take the wife riding with me.

Moot point...! The reason you de-snork your Cayman is for reducing inlet restriction! Thus standing still in a dyno booth will yield no results because you dont have forward flow over the side inlets at speed. Horsepower is directly relatated to air going threw an engine. The more air you get the more horpsepower. Removing this inlet plate will not hinder performance and does allow for a more direct and efficient flow of air into the cylinders. Actual gains (if any) would be very hard to determine, but they reallt can't be quantified on a dyno as easily as an exhaust mod..etc! -Garrett

even if there is a slight benefit, seems not worth it for the 0.5 - 1hp bump it seems..

Who is to say if the benefit is slight or more substantial at speed? While mlpor can show you a dyno sheet of only 1 hp gain, I can show one for 13hp. Is one right and one wrong? both right? both wrong? As I've said all along, it is up to the individual if they want to do this or not, but I originally did it for more sound and if I happen to get a HP benefit as well, hey all the better!

Garrett, please go talk to some one with an engineering back ground, preferably in aero or fluid systems and think a bit more about what you are saying. IMO, if your point is that the fact the car wasn't moving down the road invalidates the dyno test, well then, only IMO of course, you are just flat wrong, in so many ways, it would be pointless to spend more keystrokes arguing it. Cheers

Finally, the "voice of reason"! It's amazing how some seek a way to rationalize (find error) to justify the wizardry of after-market money makers. It's as if Porsche engineers don't know their a--- from intake design.:banana:

Well some members just participated in a PCA sponsored Dyno run on a Dynojet and there were some interesting results: Stock Cayman 2.7 - 209 HP (Tiptoe) Stock Cayman S - 263 HP (newcomer that will join soon. We met her at the event) Stock Boxster S 3.4 263 HP (MarkinHouston) De-Snorked Cayman S 265 HP (TX-KmanS) Granted these are all different cars, but the last 3 have the same 3.4 engine. The un-modified 3.4 L engines pulled the exact same HP. You be the judge...

Speaking of science... The other thing I find interesting in all the talk (many threads and hundreds of posts) about this subject on the Cayman Club and elsewhere, I have yet to see anyone prove the plastic baffle, plate, butt-guard, whatever you want to call it, actually restricts airflow. Almost everyone assumes that since its there, it certainly must restrict the airflow to the motor, yet I've seen no tests to see if the cf/m of air flow through the baffle is less then A) the cf/m of the un-baffled opening or B) the actual intake needs for the motor in cf/m. brad

TX, my "judgement" is that the 3.4's are all with statistical norms that Porsche would be proud of.

I was surprised at the consistency of the 3 dyno runs on my car and the consistency of the three 3.4L. Impressive.

I don't find 2 bhp between three differnet cars as conving as 2 consistent bhp difference found between all three cars each run once with, and once without the debris shield. I'd say 2 bhp could just as easily be explained as within the dyno's % measurement accuracy; tire pressure or wheel selection; engine, gear box or even lube specs (including temperature) tolerances and conditions. 2 bhp on 263/265 is less than a 1% varriance. Why didn't anyone try two dyno pulls, either a snork/no-snork; or I would guess in your case a no-snork/snork comparison on the same car/wheels/engine/transmission etc.?

Brad, While I concur no one has set up that scientific of a test and it would certainly be interesting to see the results the question comes down to is it restricting the engine at some point that by removing it a benefit could be had? The only way to know this would be to do exactly that, put on the meters and run the engine up to redline multiple times with and without the plate to see what changes if any occur. Assuming, for a moment, that from the factory the baffle plate isn't restrictive enough to choke a factory stock setup more than 1 or 2 hp. What happens when you install the EVO intake and free up that later portion of the intake system. Now does the baffle plate cause enough restriction that the effects become more tangible, say 5hp? Let's add to that ECU tuning that is dumping more fuel and more timing into the engine increasing the demand for air, now does the baffle plate become a bottleneck? Last, but not least, what if we free-up the exhaust to get everything moving through faster and more efficiently, now does it become even more of a restriction or would you argue no restriction at all? I would argue that as "some" point the baffle plate becomes an inhibitor, whether that is simply with the EVO intake installed or by the time you get a turbo plopped into the back I don't know, again some scientific testing would resolve that question. If anyone has the means to test this, it would be interesting to see, in fact I'm wondering if we all don't have the means to test this. We have MAF sensors right? Shouldn't the values the MAF sensor is reporting be different for a car with say no baffle plate vs. one with? or one with no baffle plate and mods vs. one with baffle plate and stock? I'll have to ask Scott Slauson if it is possible to get the "live" MAF readings from the OBDII port via his software, then testing could be done with various configuations to see what impact, if any, the baffle plate has on the MAF values. Short of a bunch of scientific test equipment I think this would resolve it wouldn't you? AFAIK to date no one has had removing the baffle plate do them any negative damage or have negative impact to performance and many seem to like the sound so even if the gain for any individual is small or negligible, I don't see the harm in doing it if the owner wants to, especially if they plan to make further mods to their car that may start to emphasize the impact of the baffle plate more. BTW 911 GT1 cars had the intakes repositioned to the top of the roof because they weren't able to get enough air into the engine with intakes on the side, might be interesting to see what difference that sort of intake would make to a Cayman ...

Ken - First, let me be clear: I'm not saying that de-snorking or modifying the cars is bad - if people want to do it, it's fine with me, even if they just like the sound of it... I would probably do some things to my car, but I want to run in the Showroom Stock class in Parade each year, and it would be a hassle to return it to stock just for one event a year... but to automatically say that a bunch of extra HP comes with the sound, I just don't see it. Remember, the one time I've seen a car dyno-ed with a before and after de-snorking (at Imagine Auto @ last year's Croctoberfest) the difference was 1 HP. And, I might add that they had flashed the ECU and put the evo intake on the car first, so that takes a little bit of steam out of your theory above... I guess my biggest point here is that no one really knows how much air goes through the baffle and whether it's "restrictive" or not. Because it goes over the intake opening (and of course some conspiracy theorists also think that PAG is committed to "holding back" the performance of the CS) people just assume it's restrictive. This makes no sense to me - to "fix" something, someone must prove to me that something is broken first. Anyway, given your modification scenario above, the motor could very well need more airflow - or not - until it can be shown what maximum airflow is capable of going through the baffle, and what maximum airflow the motor needs. brad

De-snorking the Sleeper OK, I did it yesterday in about 20 minutes, including painting. Car sounds louder, not going to dyno or track it, etc. But I will say, looking at my wife's 2002 Boxster S without the anti-cigarette plate and my 2007 Cayman S, how did my car breathe? How does it breathe now with just a little 4" tube to the engine, not even with some modicum of "ram air" or a straight airflow to the opening? Bottomline, what ever gets more to the engine is good in my book, now just to get the engine to use it more quickly.... Warm regards to all, MISpuds:cheers:

Hmm, I remember doing a lot of calculations about the ram air effect while I was trying to improve my 300ZX's hp. (I had a masters in mechanical engineering at the time). Gains seemed to be very difficult to come by, provided the installation was specificially for ram air. If it is not, as in this case, I am guessing there is nearly zero effect. I also did some tests where I hooked up thermometers around the intake and drove around, this was about 10 yrs ago when all of this "cold air intake" stuff seemed to get popular. My conclusion was that if you were sitting idle for a little while the air would be heated from the engine. However, after you got going it leveled off to ambient temp very quickly. Therefore, I am very skeptical about "cold air" intake mods. The air will get "cold" or reach ambient with any install. I believe the gains are almost exclusively due to lack of restrictions with the mod. At the time, I considered this "cold air" stuff to be nonsense. PLEASE PLEASE tell me if I am incorrect on this though...I have not looking into this for many years. That said, my point is that the dyno should be run with fans mainly because of the heat that can be generated from a car idling. I assume everyone knows that heated air will reduce hp. This would be consistent with my actual field tests. Anyway, that was 10 yrs ago, I would be curious if my thoughts are still valid.

I would like to put a fairly electric powerful blower fan to the intake. Im even thinking of one of those blower vacs from the hardware store. Wella, Electric turbo! Another idea is I could get a scuba tank with an air feed and force some induction into the intake. Yes, its mad Friday here :beer:

Well, good luck with that.... However, I think you will find that any benefits do not outweigh the cost, hassle and weight involved. If something that simple were really useful, lots of people would be doing it. BTW, it's "voila".

ECU learning has a marginal impact on performance. While I can't say I have a lot of experience tuning Porsche ECUs, I do have experience with other ECUs. The "learning" is generally calculating a long term moving average correction to the amount of fuel delivered to the engine for a particular amount of airflow and rpm. This long term correction is applied to the stock tables and that much fuel is delivered. The O2 sensor reports whether the engine is running lean or rich and a short term correction is made to achieve the desired ratio of air and fuel. (typically 14.7 to 1 under normal to spirited throttle and around 12 to 1 at full throttle) If the short term corrections require more fuel for an extended time, the long term moving average goes up. The amount of fuel actually delivered does not change appreciably. Long term goes up, Short term goes down, net result is the same. The throttle might be slightly more crisp once the right long term correction is learned, but changes in the weather will have more of an effect. All that being said air intake mods a generally worth very few hp. Generally cooling the engine compartment will produce a greater bump in horsepower than the intake mod. A better measure of improvement would be to look at the numbers from the Mass Air Flow Sensor and see if the engine is actually moving more air at a given rpm and given weather conditions. Burn more air and fuel in a given time, and you are making more hp.

So to bring it back to the title of the thread, did we really 'De-bunk the de-snorkel'? The jury is still out for more testing.

I think what we've decided is that if you have no other mods at all and do it that you'll get more of a gain in HP than if you already have other mods like exhaust, ECU tuning, intake, etc. However, your gain could be anywhere from 1hp to 13hp at the rear wheels if you dyno test. Most people do it for the sound change, not for any HP change. No one has dyno'd a HP loss so there is no instance of reported performance loss either. As such I don't think "debunk" is the right term, even if it makes a catchy title when combined with de-snork. We've simply shed more light on the subject with additional testing and determined that for most it is an acoustic mod more than a performance mod.

Anyone else experience a stronger rush of air (draft) when a door is only partially open vs. completely open? On hot summer evenings, I've adjusted the door(s) in my house to maximize the flow of air through the rooms to cool off, and have definitely noticed partially-open doors seem to "suck" the breeze in from outside better than a fully open door (other than the instances, however, when the breeze is blowing *directly* into the doorway - fully open door is best then). Just a thinking aloud here.... the engine may be getting a sufficient volume of air entering the inlet with the plate in place, and in fact, the plate may *increase* the velocity at which a given volume of air enters the inlet when the vehicle is at speed. Like the partially-open door analogy? Or, maybe the plate also creates a higher pressure environment right behind it (and thus, right in front of the inlet) when air is rushing past the side of the vehicle at higher velocities. Ever tried to breathe while sticking your head out the window at speed? The air rushing past the opening of your mouth creates low pressure and your lungs must fight against that low pressure zone to suck in air. On a motorcycle, breathing behind the protection of a full-face shielded helmet is much easier than trying to breathe with the face shield up. In both cases, sufficient volume of air is available to your lungs, however, it is much harder to breathe in one case vs. the other. Just so happens, the perceived "restricted" scenario is the easier one. I might add, without a face shield, breathing through the nostrils is easier than an open mouth -- again, "restricted" airway seems easier when the velocity of air increases. So, maybe on a dyno with static air conditions (other than the fans which are there really to blast air at the radiators to keep your car from overheating on the dyno), de-snorking *might* get more air into the engine, especially with other mods, and thus yield power gains. On the other hand, maybe at speed... at high speeds, de-snorking makes it harder for the engine to breathe, just as it is harder for our lungs to breathe. thoughts?

Reading for you: Bernoulli's principle - Wikipedia, the free encyclopedia