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  #41  
Old 08-02-2011, 08:12 PM
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'08 CRD, Nissen snorkle, 40,000km.,auto. Average fuel consumption over this distance 11.8km/lt.

These figures are gps corrected and have been consistent from day one. Very little city work and no towing or roof rack have no doubt helped. Always uses a tad more when I'm up Darwin way, whether it's the fuel or the temp is debatable, but I suspect the former.
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  #42  
Old 08-02-2011, 08:19 PM
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2010 CRD Auto - stock - with Nissan snorkel since new - traveled 15000km which includes 5000km towing 1300kg camper trailer. Total average 14.0 - best 11.8 - worst 16.4 when towing through Flinders Ranges.

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  #43  
Old 08-02-2011, 09:04 PM
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Quote:
Originally Posted by bennoGU28 View Post
The CRD has a MAF (Mean Air Flow), MAP (Manifold Air Pressure) as well as the barometer so you cant trick it.
barometer (a pressure sensor) on the intake side it will easily calculate the change in absolute pressure pre turbo with a snorkel compared to no snorkel.
I always thought that "MAF" stands for "Mass Air Flow" and "MAP" for Manifold Absolute Pressure and barometer aka atmospheric pressure sensor is usually part of MAP sensor.
Do CRD ZD30 engines have both the boost and vacuum sensors? Cheers
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  #44  
Old 08-02-2011, 09:20 PM
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After reading this thread and with a technican point of view one could understand how one would think this could be the case. But with all the sensors a air filter and snorkle path to follow before enigne then with the diesel engines high sucking vacum feel doubtful that the ram air effect is the cause.

My 2 cents.

Plus owning a TDi with a air mas sensor as well.
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  #45  
Old 08-02-2011, 10:42 PM
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I agree with rumcajs, the MAF is Mass Air Flow past that sensor and the MAP is Manifold Absolute Pressure (in that it is the current ambient air pressure plus turbo boost pressure into the inlet manifold).

I have absolutely no idea whether or not having a snorkel fitted or not, will change the air pressure before the turbo inlet but here is my theory; (and please correct me if I am way off the mark)

The CRD turbo VNT setup is ECU/VACUUM controlled therefore the more easily the intake air can flow to the turbo, the quicker the boost can come on and more power can be made low down with less diesel.

I do not argue with the fact that the ECU will adjust diesel injection according to the MAF/MAP sensor input but I do put it to you that the flow of air with or without snorkel fitting may contribute to differing fuel consumption figures.

The early posts questioned whether the directional positioning of the snorkel ram head changes the fuel consumption figures or not; I am driving from Darwin to Brisbane later this week and will record some real life data to share with others to draw their own conclusions.

If you have any specific tests you would like recorded (within reason) let me know.

Cheers Heffers

P.S. The trip will be in a 2007 ST 3.0CRD Manual Wagon with Blocked EGR, Scangauge, Boost Gauge, EGT Gauge ( 50mm post turbo flange ), Dual Batteries, Nissan Steel Winch Bar (no winch), Standard Tyres, Frantz Bypass Oil Filter, Running Mobil 1 5w-50 (15,000km old) recently cleaned intercooler, New Oil Filters, New Air filter, New Fuel Filter, Tough Dog +50mm Coils and 41mm Foam Cells all round towing a 6'x4' with a few spare Mini Moke parts. Carting an Engel 40L with plenty of twiggy sticks and snacks for the maggots, son of 12kg, daughter of 16kg, me of 89kg and wife of .....I'm not that stupid.

Last edited by Heffers; 09-02-2011 at 06:28 AM.
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  #46  
Old 09-02-2011, 09:59 AM
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I did this yesterday evening.

Been driving today and the results are interesting. Definitely no change in performance (my old TD42 diesel felt restricted somewhat with the snorkel head rotated 180 deg...you wouldn't think this engine could feel less powerful but trust me it did!! what a ****ter).

Lets just say I've never seen the fuel economy meter on the dash go this low before..... Think VW golf sort of fuel economy @ 100km/hr.
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  #47  
Old 09-02-2011, 10:54 AM
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Sorry to but in, But this talk of ramming effect makes me think about the air filter. The air filter is made from a material that has x number of holes of x size in microns, so it is only going to let a certain amount of air through no matter what (unless a starve situation arises or you have a badly seated filter), what can't get through remains as pressureised reserve in the tubing.

The bigger problem would be the starving mentioned earlier, that will definitely have negative ramifications, but with a snorkel, you always have a positive charge of air (except maybe at idle sometimes). My thoughts, now I'll go away.
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  #48  
Old 09-02-2011, 11:20 AM
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I'll throw in my two Bob's worth in by saying the standard air filter and intake system fitted with or without snorkle will flow more CC's of air than what the engine requires. Only performance gain/fuel eco improvement would be the cooler intake charges. I don't believe in any ram effect what so ever.
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  #49  
Old 09-02-2011, 12:19 PM
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Quote:
Originally Posted by geeyoutoo View Post
Sorry to but in, But this talk of ramming effect makes me think about the air filter. The air filter is made from a material that has x number of holes of x size in microns, so it is only going to let a certain amount of air through no matter what (unless a starve situation arises or you have a badly seated filter), what can't get through remains as pressureised reserve in the tubing.

The bigger problem would be the starving mentioned earlier, that will definitely have negative ramifications, but with a snorkel, you always have a positive charge of air (except maybe at idle sometimes). My thoughts, now I'll go away.
although, your theory assumes that there is an air ram effect providing positive air pressure in excess of 1) what the air filter media is capable of flowing and 2) what the engine is utilising.

I would probably put money on a snorkel not providing enough positive pressure to overcome the air useage of a 3.0L turbo diesel @ full boost, regardless of the speed the vehicle is doing.

As it is the snorkel ram head is designed to disrupt the airflow going into it in order to act as a water seperator preventing excessive moisture reaching the airbox....any decent ram system typically utilises a bell type or smooth edge opening to provide less disruption to the airflow. This is not to say there is no change in air pressure at the airbox compared to standard!

In short, while very interesting I am not sure if it could be the full cause.
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  #50  
Old 09-02-2011, 12:42 PM
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Quote:
Originally Posted by Yom View Post
although, your theory assumes that there is an air ram effect providing positive air pressure in excess of 1) what the air filter media is capable of flowing and 2) what the engine is utilising.

I would probably put money on a snorkel not providing enough positive pressure to overcome the air useage of a 3.0L turbo diesel @ full boost, regardless of the speed the vehicle is doing.

As it is the snorkel ram head is designed to disrupt the airflow going into it in order to act as a water seperator preventing excessive moisture reaching the airbox....any decent ram system typically utilises a bell type or smooth edge opening to provide less disruption to the airflow. This is not to say there is no change in air pressure at the airbox compared to standard!

In short, while very interesting I am not sure if it could be the full cause.
Your Point is taken Yom, but, (your use of the word probably shows a small amount of doubt ) I imagine there is a significant difference in the air flow requirement between a vehicle doing 2000 and 3000, the mere fact of the swept volume dictates 1/3 more air is required when you increase the revs by 1/3, at least that's the way my feeble mind sees it, and it must get past the natural restriction of the filter. Hence my point about a bankable air supply (now I will put in the proviso of maybe not at considerable high revs)

So a vehicle at full boost at 2000 will not use as much air as the same vehicle doing 3000, I suppose we also must take into account these are not racing cars they are lumbering 4x4's we tend to drive like racing cars.

But what do I know, I'm one of those idiots who owns a grenade and loves it.
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Last edited by geeyoutoo; 09-02-2011 at 12:52 PM.
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  #51  
Old 09-02-2011, 02:25 PM
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Quote:
Originally Posted by Chip It View Post
We have discovered a little quirk with snorkel on late model vehicles. (diesels only at this stage but could be petrol variants too) Also it has been on 2 different vehicles.
If you have poor freeway fuel economy try this. Turn the head of the snorkel backwards and next time you are on the freeway is if your fuel economy has increased.
We have reasoned that the "fault" lies in the fact that the ram air effect is causing the MAF meter to "see" a higher air flow and that it tries to match this extra air with extra fuel thus causing poor freeway economy. City driving does not show this issue as there is not enough ram air effect to piss off the MAF.
If the fuel economy returns, don’t bother going to the Dealer ... they won’t have a clue. And don't go to ARB (for example) they too don't understand it (for now).
A simple solution is to slot out the rear of the scoop so that air can travel through it as well as down. This relieves the ram air effect
Hope this helps

Cheers
I believe Mass flow sensors are not effected by pressure or temperature.
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  #52  
Old 09-02-2011, 03:13 PM
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Quote:
Originally Posted by GP_STI View Post

Turning the snorkel head sideways, as one user does, would create a negative pressure in the snorkel. Turning it backwards might either cause negative pressure, or alternatively force more air in, depending on how the air swirls over the head. Taking the head off would be the same as truning it sideways, I think. Might even whistle as does a bottle when you blow over the opening.

The best option to try might be to drill some holes at the back of the head, to allow most of the excess pressure to breeze through but not allow enough that negative pressure is created.
That would be me...

I look at the whole discussion this way.

Firstly, Air has mass. Anything that has mass must have a force applied to change direction. Whilst I agree there may be a venturi effect it will be very small as there is no change in the flow pressure past the head. A true venturi has an increasing dia to lower the pressure for a given flow.
The problem I have introduced tho is that the air mass must now change its previous relative direction by 90 degrees. Because the bugs have a higher mass than the air only a small amount now enter the Snorkel.
Given the object of turning the head sideways is to keep the bugs out of the Airfilter I reckon I get the best of both worlds in very minimal bugs, the worlds most inefficient venturi and less force (pressure) to get the air mass to change direction into the Snorkel than if it was rearwards facing.

Secondly, Snorkels should have an aspect ratio to maintain the same efficiency into the airbox IE they do use a ram effect, albiet quite small in itself, to overcome the flow reduction due to the bends and walls of the snorkel tubing.
I believe the ballpark aspect ratio figure is 1.4 : 1 but I can't substantiate that number as I'm stuffed if I can remember where I dredged it from.

If that aspect ratio is important then drilling holes or vents will be quite detrimental. On the other hand if it doesn't matter then cut sick

Anyway, all that leads me to believe that a properly designed Snorkel (Nissan or Aftermarket) will deliver pretty much the same mass of air to the Airbox as a standard setup drawing from the inner guard BUT as I said earlier a very interesting thread.

Bottom line is without a Lab, a doctorate in Aerodynamics and a Wind Tunnel it's all pretty much arbitary but good exercise for the brain.
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  #53  
Old 09-02-2011, 03:44 PM
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I was thinking more about this today and im even more convinced than ever the snorkle has no effect. Next time someone is driving, stick your arm out the window and put your hand over the snorkle inlet. At cruising speed and most certainly under acceleration, it is sucking very hard. There aint any ram effect at all.

You would have the increase this inlet size by a massive amount for excess air to be 'pushed' into the airbox/inducer.

Quote:
Originally Posted by the evil twin View Post
Anyway, all that leads me to believe that a properly designed Snorkel (Nissan or Aftermarket) will deliver pretty much the same mass of air to the Airbox as a standard setup drawing from the inner guard BUT as I said earlier a very interesting thread.
Agree 100%. The physics and the concept of how the AFM calculates the AFR doesnt remotely support the theory.
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  #54  
Old 09-02-2011, 03:56 PM
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OK, we seem to have moved away from the original question of "CRD and bad fuel economy" linked to snorkels. And now just talking of the impact of the snorkel.

My experience with the snorkel admittedly on a DI, which was fitted a year after I purchased the vehicle new was that nothing changed, I already had a good history of fuel economy, even though the supplier suggested I would achieve better fuel economy, I didn't and didn't expect it.

What I did expect was to have the ability to drive through considerably deeper water, which I did achieve. And was happy. I'm sure many of our DI colleagues on here would have similar stories, so is it something in the CRD or is it B*******.

Don't get me wrong I am enjoying the thread, there can never be too much info to assess. Just need to sort the BS from the logical due to lack of academically documented hard data.

By chance, does anyone have a dyno sheet for before and after.
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  #55  
Old 09-02-2011, 08:15 PM
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Well. was in the process of shopping for a snorkel for my 2010 CRD with 10 000 on the clock but now have my doubts. Consumption at the moment is between 11.5l/100km and 13l/100km stock vehicle in manual. No matter how I drive I can't return the fugures of 9l/100km I was getting from my old 2003 ser III direct injection, which had a bull bar and a few other accessories. This post has been very interesting and it re-inforces the fact that the CRD engines are not as economic as the older DI ones, even though the salesman had me convinced that the CRD was even more fuel efficient than the DI. One peace if mind is that I have been told by some CRD owners is that after about 20 000 kays the fuel economy improves. I am waiting patiently for this!!!
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  #56  
Old 09-02-2011, 08:27 PM
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4th fill and got 14.2L /100.
This may have been due to roof racks and roof top tent being on for 300km.
Still not happy. Old truck always had roof racks and awning and never went over 12L/100.
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  #57  
Old 09-02-2011, 09:02 PM
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09 CCRD auto with steel bar and ally roof rack all else bog stock snorkel from new - nissan between 13's and 15's. 11's touring.

How can you create ram air to a turboed engine. The air being "forced" in will never overcome what the hair dryer is sucking.

My 2 cents
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Old 09-02-2011, 09:25 PM
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Um ok.

The more load you can take off the turbine which is driving the compressor the more air you will get into the engine, via the turbos energy wont be wasted by drawing air, instead it will be using that saved energy to spool faster and stay spooling faster to compress even more air.

Worst case, if you had a kilometre of intake pipe (hypothetical here) the resistance of the air passing through would be quite high yes?? So if you blow down it the easier the air is to draw from on the other end? YES OFCOURSE! Air mass, its not negligible.
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Old 10-02-2011, 10:34 AM
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Um ok.

The more load you can take off the turbine which is driving the compressor the more air you will get into the engine, via the turbos energy wont be wasted by drawing air, instead it will be using that saved energy to spool faster and stay spooling faster to compress even more air.

Worst case, if you had a kilometre of intake pipe (hypothetical here) the resistance of the air passing through would be quite high yes?? So if you blow down it the easier the air is to draw from on the other end? YES OFCOURSE! Air mass, its not negligible.
but with a snorkel travelling at road legal speeds it will make 2/10 of stuff all difference..
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Old 10-02-2011, 12:28 PM
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Quote:
Originally Posted by Scrotumus View Post
How can you create ram air to a turboed engine. The air being "forced" in will never overcome what the hair dryer is sucking.

My 2 cents
Exactly. Like yom said, the difference I dont think, would even be quantifyable. I dont believe there is any load to be taken off the compressor wheel. Air has resistance and it doent matter if the air is stagnent or mobile for blades spinning at 100,000+rpm.
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