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  #21  
Old 08-02-2011, 02:44 PM
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Quote:
ciapek
High 10's to high 11's, 2010 CRD Auto, totally stock. 10K on the clock.
Hope this helps.
ciapek, do you have a snorkel fitted?

Cheers
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  #22  
Old 08-02-2011, 02:57 PM
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It is getting pretty easy to see what is causing the bad fuel economy on the Nissan Common Rail Diesels........

Answer: Having a snorkel fitted

Why: The Ram Air effect from the snorkel increases pressure around the MAF which tells the ECU that I am at a lower atmosphere more dense air level and it in turn throws in more fuel.

Who TF would have thought? So simple..

I was speaking to a Diesel fuel injection specialist in Sydney this morning about some performance options for my D22 Navara and he said by the way I had a customer in the other day who had recently fitted a snorkel to his patrol CRD and his fuel economy out on the road was really bad since it was fitted. After much work and dead ends they turned the head on the snorkel around backwards and the customer went for a long drive and the economy went back to normal. (No it does not stuff the engine doing that)

They then deduced the MAF and the extra ram air pressure around it giving the ECU the wrong info and hence the bad economy.

Looks like the answer to the "Holy Grail" of CRD fuel economy and my mini survey seems to verify it.

Anyone want to sell me a grill kit for the back of the snorkel head.
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  #23  
Old 08-02-2011, 03:01 PM
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2007CRD factory fitted snorkel
cruising 12.5k/100
around town 14.5 - 17 k/100
cruising while towing jayco 16.5 k/100

Was told by Brighton Nissan that the air filter clogs very quickly with snorkel fitted.
The around town variance is new filter compared to 1 month old filter.
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  #24  
Old 08-02-2011, 03:45 PM
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Snorkel, Chip, 33's, Manual Tranny, Scanguage, Dual GPS. Done 25,000 K's in her now from when I got it with 55,000 on the clock.

Over the past year (25,000 K's) consistently returns the following...
11 to 12 LPH around town
14 to 14.5 110 Cruise
15 to 16 towing my 1 tonne camper and loaded up

I found the thread on the "Ram Air" interesting but there is one big Question from me.
Whats the difference in total flow past the MAF between Ram Air and Turbo Air?
Both are a form of forced induction and in both cases the Air has to travel past the MAF so of the total air flow how does the MAF know that X percentage is drawn by the Turbo and is normal and therefore fuel is calculated by the ECU but Y percentage has mysteriously appeared so must add more fuel.
To phrase it another way perhaps... How does the ECU understand that there is "more" air flow due to Ram Effect so therefore add more fuel.

I'm not saying it doesn't... just saying that given the sensor configuration I can't see how and need someone with more ECU knowledge than me to explain so I can understand.
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  #25  
Old 08-02-2011, 04:15 PM
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Didn't we just have a whole swag of threads on here in recent times about NOT turning your Snork's backwards at high speeds.

One thing I do know is that the Manufacturers rely on a percentage of Ram Air and particular Aspect Ratios to get the Snork's to work efficiently. Not saying that does NOT have a detrimental effect on ZD30 CRD's... just saying the majority are designed to face forward to get the "normal airflow" happening that would otherwise be restricted by the twists and turns of the flow thru the Snork.

Personally, I remain unconvinced either way but must admit I turn mine sideways never backwards when the "hoppers" are in plague proportions.

Great Thread tho... looking forward to lots more opinions
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  #26  
Old 08-02-2011, 04:18 PM
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Just bought my 08 Manual WITH SNORKLE and 88,000 on the clock. Done 2500km so far and filled 3 times and all 3 figures come in at 13.3L/100km, mix of motorway and urban driving. Truck does have 33's but stock apart from that.

My old Direct Injected GUIV religioulsy returned 12L/100 no matter what I did in it. It was on 32's so I reckon the new truck is pretty much on par given the larger dia tyres.
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  #27  
Old 08-02-2011, 04:20 PM
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It would be interesting to compare the Nissan air tech against others to see which has the best RAM effect and possibly the worst fuel economy. It would appear that it is definitely upsetting the sensors MAF, MAP.

I have just today fitted a brand new air filter and will see if it improves my fuel usuage greatly. After that I am going to remove the head off my snorkel for a while and see. Fingers crossed as I would like the low figures some other owners have out of their Non-Snorkel equipped CRD'S.
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  #28  
Old 08-02-2011, 04:32 PM
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2010 CRD Manual - Nissan Snorkel since new (steel roo bar, roof rack only external mods) no chip/exhaust/tyres changed/added.

At new fuel usage was circa 18L/100 but as the thing has been wearing in the economy has been slowly increasing over time currently at ~13L/100km (I get about 850km from 110-120L) vehicle has ~25-30k on the clock.

In short am not too unhappy with my economy.
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  #29  
Old 08-02-2011, 04:35 PM
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What would be interesting is installing a pressure sensors in front of the air filter both Pre and Post snorkel installation to measure actual pressure increase. Ram effect may have some merit in normally aspirated engines but as for forced induction..... Maybe a hyclone is the fix.
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  #30  
Old 08-02-2011, 04:40 PM
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IMHO and being Instro tech, I agree with Glort and The Evil Twin ..... The fuel consumtion may increase but it is not from the pressure increase ..... if there is any!
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  #31  
Old 08-02-2011, 04:40 PM
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Quote:
What would be interesting is installing a pressure sensors in front of the air filter both Pre and Post snorkel installation to measure actual pressure increase. Ram effect may have some merit in normally aspirated engines but as for forced induction..... Maybe a hyclone is the fix.
If any home genius can verify and come up with a fix I shall worship the ground they walk on. I bet there are some pretty switched on people out there that can solve this for us. Everything seems to point at the snorkel.

The first thing we need is someone with a CRD and good fuel economy to fit a snorkel and see what happens....any takers?
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  #32  
Old 08-02-2011, 04:47 PM
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I'm not saying the fuel consumption increase is not from the snorkel ..... It probably is, but because of a greater restriction caused by a pressure loss caused by increased resistance of the bends and greater surface area rather than an increase in pressure caused by "Ram" effect. Maybe every prime mover you see on the road should turn their snorkels around. LOL
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  #33  
Old 08-02-2011, 05:01 PM
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I have a 2009 CRD with factory snorkle, Last trip out on the weekend returned 12 > 13Lt per 100. It seems to be settling around this 12 to 14 mark depending on conditions, I am happy with this.

It seems to get better with every outing, its now got 19K on it

When I first got it fuel usage was much higher
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  #34  
Old 08-02-2011, 05:04 PM
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i didnt notice ant difference in economy when i fitted my snorkel (genuine nissan) and im a fuel economy nazi

what has me thinking this theory is B.S is that if its getting more air then adding more fuel to compensate you should be getting more power and therefor not need as much throttle input so economy shouldnt change , the same as how economy can increase when a chip is fitted.
Unless the extra air rushing past the AFM is tricking it somehow into thinking its getting more air than it actually is and then telling the computer to add more fuel ...
ahhh i dunno just my thoughts
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  #35  
Old 08-02-2011, 05:07 PM
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The guys in Sydney did it as a test to see if it was causing the high fuel consumption and it was. Not a lot you can do when you have a hole drilled through the guard.It is back the right way round.

I do not think the CRD likes the snorkel. The theory of more resistance may well be the answer and not the RAM air effect. One thing for sure after the posts here, the snorkel to non snorkel fitted CRD's have very different fuel economy. Some being much worse than others and some only getting worse out on the road at higher speeds.

A positive result and a positive fix would be good.

I am sure that the trucks out there are not running Nissan Patrol CRD diesel engines.
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  #36  
Old 08-02-2011, 05:27 PM
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I have a 08 CRd with safari snorkel and return 14.5L/100 and 23 towing 2.2t van. Had snorkel since new so never known any difference.
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  #37  
Old 08-02-2011, 06:32 PM
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As I dont have these sensors I know nothing about them, however could the MAP get tricked into thinking the engine is under higher load due to the restrictions in the air intake, via the snorkel, increasing the manifold vacuum and the computer sends out a call for more fuel to compensate.???

As mentioned I know zip, just a thought!! Is there a difference in fuel consumtions between the standard 3in nissan snork and say a 4in safari?? The safari would produce less pressure drop, which in turns reduces the vacuum in the manifold so the comp thinks, easy drivin, dont send as much fuel.

My 4.2 TD give me 13.5lts/100 around town with a factory snork, 12 with only my surfboard in the back on open road.
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  #38  
Old 08-02-2011, 06:58 PM
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Getting 12's to 13's /100 highway, 16's around town, 19's/20's with van in tow. auto crd no mods no snorkel
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  #39  
Old 08-02-2011, 07:50 PM
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Quote:
Originally Posted by BradM View Post
The first thing we need is someone with a CRD and good fuel economy to fit a snorkel and see what happens....any takers?
Yep, I got 11-12's when standard. Fitted a genuine nissan snorkle and got amazing figures of arond 11-12's.

I think the snorkel is a good 'theory' but I personally dont believe it. Technically it doesnt make sence. The flow of air past the AFM is determined by the engine throughput. The ram effect only come applicable with WOT. Perhaps if the engine ran a MAP in place of an AFM the principal would stack up, but again, I've never come across any ECU that can't easily account for a simple variable like air flow. If the engine was running huge boost, then the AFM would run out of voltage.

If it was an abnormal AFM reading, you would almost certainly get a CEL.
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  #40  
Old 08-02-2011, 07:50 PM
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Quote:
Originally Posted by Drillerboy View Post
As I dont have these sensors I know nothing about them, however could the MAP get tricked into thinking the engine is under higher load due to the restrictions in the air intake, via the snorkel, increasing the manifold vacuum and the computer sends out a call for more fuel to compensate.???
Turbo diesels dont have manifold vacuum (in the very broad sense) so no cookie for you.

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.
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