Air flow restrictions
Submitted: Tuesday, Mar 14, 2006 at 11:25
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Member - Roachie (SA)
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
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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