Air flow restrictions

Submitted: Tuesday, Mar 14, 2006 at 11:25
ThreadID: 31723 Views:3037 Replies:11 FollowUps:14
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I have a mate with a 4.2TD patrol the same as mine (but pretty much bog standard). He is a farmer and has had a bit to do with a small device often fitted to headers/harvesters etc. This device is known by a few different names and it is fitted downstream of the vehicle's airfiltration system. It "trips" when the airflow is inhibited to a certain extent (indicating a blocked air filter in the case of heavy farm equipment). The gauge of measure is in "feet of water" and these devices come in a variety of sensitivities. The one my mate has on his Patrol is a "30 foot" type which is the most "forgiving" one he could buy. With a standard paper air filter in place, the device trips quite easily when the vehicle is under moderate acceleration or load. He has even taken the Patrol for a short test run with no filter at all (he does have a snorkel) and it still managed to trip this device....but only under full acceleration. Note: he only did this on an open country road after a shower of rain so there was virtually no chance of any air born dust. It is not something I would try myself!
Just wondering if anybody has any thoughts? The device he is running is made by Donaldson, but I can't find any reference to them on their web site. He has spoken to the Donaldson blokes and they can't believe a 4.2 TD patrol could trip a 30 foot model.....it means there is an intake restriction of high proportions. It's just made me wonder as I'm typing this, whether he might have a piece of foam rubber just before the air filter box....I think Nissan have this fitted in the inner guard and it should be removed when/if a snorkel is fitted.
Any info or other people's experience would be appreciated. We all tend to talk about getting our vehicles breathing better (by whacking on 3" exhaust systems etc), but all that is gunna be useless if the bloody thing can't suck in enough air to start the whole "breathing" process.
Cheers
Roachie
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Reply By: Geoff M (Newcastle, NSW) - Tuesday, Mar 14, 2006 at 11:46

Tuesday, Mar 14, 2006 at 11:46
Hello Roachie,
The gadget your mate has isn't a plastic cylinder about the size of a film canister by any chance? It shows a green ring when all is good, shows yellow as the filter dirties and locks into red as a trip. Also has a reset button on top. If it's what I'm thinking of I have one somewhere and had it fitted to the Donaldson filter on my old 82' model 2H Table Top. Basically an air filter service indicator.
After all that we'll get to what I have to say, I could regularly trip mine if I got right up the Cruiser.
Thing to remember is they are a truck part. The 4.2 litre diesel at 4,000 rpm is the equivalent swept volume of a truck engine displacing 8.4 litres at 2,000 rpm. If you add in the compression effect of a turbo then the volume you are pulling is pretty significant. Leastways that's what the Donaldson man in Newcastle told me.
Still doesn't answer your blockage question beyond pulling everything apart for a squizz. Or upping the tube sizes and removing as many bends as possible in the intake path.

Geoff.
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Follow Up By: Member - Roachie (SA) - Tuesday, Mar 14, 2006 at 11:59

Tuesday, Mar 14, 2006 at 11:59
Thanks Geoff......the description you gave in your 1st paragraph is SPOT ON mate....

I guess you're right about the number of twists and bends we have in our intake systems too....it all helps to slow down the air's progress towards it's firey and explosive destination!!!
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Reply By: Philip A - Tuesday, Mar 14, 2006 at 12:04

Tuesday, Mar 14, 2006 at 12:04
Thats INCHES of water. ie the difference in pressure between the intake and outlet side of the air filter measured using inches of water vacuum as if you had a hose connected with water in it held vertically.. I think Thirty inches of water is about 2 inches of mercury , but I am sure someone will correct me if I am wrong.
I have measured my Range Rover 3.9 snorkel and it contributes 8 inches of water at full throttle using a Minihelic gauge.
Thats quite a lot if it trips at moderate throttle . Maybe a candidate for a different airbox and snorkel arrangement.
There is a comparison of airboxes in a past issue of Autospeed.
Regards Philip A
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Follow Up By: Member - Roachie (SA) - Tuesday, Mar 14, 2006 at 12:12

Tuesday, Mar 14, 2006 at 12:12
Thanks Philip.....now that I think about our phone conversation last week, he did say "INCHES" and not feet. You seem to have a good grasp of what it is I'm trying to get to the bottom of here. This bloke doesn't currently have a 2nd battery in the Patrol and that means he has a large void area which he is considering putting in a larger Donaldson air filter box in place of the standard one. It'll be interesting to see what happens if he does go ahead.
I should also add that he HAS already done the 3" exhaust modification, as have I.
Cheers
Roachie
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Follow Up By: Member No 1- Tuesday, Mar 14, 2006 at 12:39

Tuesday, Mar 14, 2006 at 12:39
inches water gauge = 0.07355 ins mercury or 0.03613 lb/ square inch or 249.08 pascals

a simple manomoter will read this type of stuff with out having to source a maghehelic gauge
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Follow Up By: Truckster (Vic) - Tuesday, Mar 14, 2006 at 13:02

Tuesday, Mar 14, 2006 at 13:02
did anyone else get a techno chubby reading nudies reply?
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Follow Up By: Member No 1- Tuesday, Mar 14, 2006 at 13:19

Tuesday, Mar 14, 2006 at 13:19
leave me alone truckie
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Follow Up By: Michael ( Moss Vale NSW) - Tuesday, Mar 14, 2006 at 14:12

Tuesday, Mar 14, 2006 at 14:12
Truckster!! I think he meant Manometer, As it happens, I fould one in my lunch box today!!!
Patrol 4.2TDi 2003

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Follow Up By: Michael ( Moss Vale NSW) - Tuesday, Mar 14, 2006 at 14:19

Tuesday, Mar 14, 2006 at 14:19
ooooppps , I meant I found one.,,,
Patrol 4.2TDi 2003

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Follow Up By: Member - Brian (Gold Coast) - Tuesday, Mar 14, 2006 at 20:13

Tuesday, Mar 14, 2006 at 20:13
Techno chubby!!!!!!!!

LOL..... Jeeze...... you crack me up Bruce!!
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Follow Up By: Member No 1- Wednesday, Mar 15, 2006 at 07:51

Wednesday, Mar 15, 2006 at 07:51
its not that funny Brian
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Follow Up By: Member - Brian (Gold Coast) - Wednesday, Mar 15, 2006 at 07:52

Wednesday, Mar 15, 2006 at 07:52
oh yes it is!
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Reply By: revhead307 - Tuesday, Mar 14, 2006 at 12:12

Tuesday, Mar 14, 2006 at 12:12
Gday Roachie,

Im a paid up member of autospeed.com which is an online performance and tech issue magazine. (this isnt an ad, just stating a fact)

They ran a series of articles a while ago on eliminating airflow restrictions using a manometer (which is ur feet of water thing) to show drops in intake pressure.

was a 5 part series entitled eliminating negative boost.

Just thought your post was very interesting as the autospeed article was aimed at performance cars but has equal application to 4x4's.

Cheers
Rev

AnswerID: 160415

Reply By: Sand Man (SA) - Tuesday, Mar 14, 2006 at 12:34

Tuesday, Mar 14, 2006 at 12:34
So Bill,

Something else to fit to your GU????

Bill.
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Follow Up By: Truckster (Vic) - Tuesday, Mar 14, 2006 at 13:03

Tuesday, Mar 14, 2006 at 13:03
I was thinking the same.

Roachie, you need one
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Reply By: muzbry 3175 - Tuesday, Mar 14, 2006 at 12:55

Tuesday, Mar 14, 2006 at 12:55
Gday
These little doovers can be purchased from your local CAT dealer or from JOHN DEERE or earth moving places that have a spare parts counter.
Muzbry
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AnswerID: 160424

Follow Up By: Pajman Pete (SA) - Tuesday, Mar 14, 2006 at 13:21

Tuesday, Mar 14, 2006 at 13:21
"I have a mate with a 4.2TD patrol the same as mine (but pretty much bog standard)."

This is a new use of the word "same" that I haven't been aware of before! :o)

Pete
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Follow Up By: Member - Coyote (SA) - Tuesday, Mar 14, 2006 at 17:01

Tuesday, Mar 14, 2006 at 17:01
You beat me to it Pajman Pete.. I was going to say: "since when is any GU patrol the same as Roachies????" AS IF....
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Follow Up By: Member - Brian (Gold Coast) - Tuesday, Mar 14, 2006 at 20:15

Tuesday, Mar 14, 2006 at 20:15
Guys!!! Stop it... I'm hurtin' from laughin'.....

And it ain't Phriday!!!!!

LOL...LOL
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Reply By: Darian (SA) - Tuesday, Mar 14, 2006 at 13:44

Tuesday, Mar 14, 2006 at 13:44
Indeed Roachie re "what we don't know about the breathing system" - a lot of users might not know about the restrictor that Safari put into "some" models of their snorkels (while saying nothing about it) to reduce resonance - the loss of efficient airflow from that metal disc would be dramatic.
AnswerID: 160436

Reply By: bombsquad - Tuesday, Mar 14, 2006 at 17:00

Tuesday, Mar 14, 2006 at 17:00
Maybe looking into testing immediately on each side of the air cleaner to assertain if the restriction is in the air cleaner or he plumbing of the snorkel??

Cheers andrew
AnswerID: 160464

Reply By: Member - Brad S (SA) - Tuesday, Mar 14, 2006 at 18:01

Tuesday, Mar 14, 2006 at 18:01
I had one of these air flow indicators on my SWB Pajero 2.6p. It also had a Donaldson swirl type pre-cleaner which did a really good job. However, I changed the standard air filter for a Finer Filter and the difference was amasing. It when from asthmatic to almost athletic (yeah...I know...it is all relative). The indicator never went off again.

Cheers
Brad
AnswerID: 160471

Reply By: Peter 2 - Tuesday, Mar 14, 2006 at 19:20

Tuesday, Mar 14, 2006 at 19:20
My humvee is fitted with a dash mounted air filter restriction gauge standard, 2" diameter and would fit any standard gauge mount, just needs a length of rubber hose to connect it to the air cleaner. On the Humvee it is on the outlet side of the filter before it connects to the intake manifold.
They are freely available on ebay occasionally or can be bought as a spare part
Peter
1996 Oka Motorhome

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AnswerID: 160489

Reply By: Taipo - Wednesday, Mar 15, 2006 at 21:23

Wednesday, Mar 15, 2006 at 21:23
Yeah, I had a 4.2td cruiser in NZ and it required a 4 inch air intake with no restrictions to air box and was only begining positive pressure after 100 kms by ram effect.
AnswerID: 160763

Reply By: Truckster (Vic) - Friday, Mar 17, 2006 at 13:01

Friday, Mar 17, 2006 at 13:01
If you have a safari snorkel, try it without the ram on the top, notice BIG power difference (better)
AnswerID: 161136

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