300Tdi airflow or max RPM? - Defender Source
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  #1  
Old July 11th, 2007, 05:06 PM
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George Kase
1983 110 200Tdi CSW LHD
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300Tdi airflow or max RPM?

can anyone tell me what these specs might be for a 300Tdi engine? am trying to create a home made snorkel for my truck.
George
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  #2  
Old July 14th, 2007, 04:02 PM
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Mike Hammond
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I beleve the Max RPM for a 300 tdi is 4800 and 4000 for a 200 tdi. I rarely go over 3000 rpm though which equates to a bit over 70 in top gear
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Old July 14th, 2007, 04:58 PM
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Centri has an equation for calculating the airflow (cfm) based on the displacement and max rpm:

http://www.centriprecleaner.com/specs.html

So for the 300Tdi: cfm = (2.5*61.02*4800*1.85)/3456 = 392 cfm max
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Old July 14th, 2007, 06:48 PM
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Clark Bowen
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The horsepower peak is 4000 rpm according to LR specs. Wouldn't you use that number? I don't think I'd want to wind the 300 Tdi to 4,800 as it sounds pretty spent at 4,000.
Interesting that you mentioned Centri, because using their calculator I need a 5" base diameter pre-cleaner (EX-40) at least and yet the largest snorkels that I've come across are 3". I emailed Centri asking if it was ok to neck it down to a 2 1/2" downpipe (the Southdown snorkle diameter) and am waiting to hear back. Reading their info it sounded like the pre-cleaners added some updraft and that is why a bigger cleaner and base was needed. It did make me wonder if the 2 1/2" snorkel is restrictive but I don't know how to calculate what is the optimum size. Anyone know how to calculate it?

Clark
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Old July 14th, 2007, 08:27 PM
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Clark - Using 4800 rpm is just a guideline for the max possible airflow (assuming 4800 rpm is the correct max rpm). Doesn't mean you have to run the engine there. Use that as a starting point, and then start backing down to the real world based on what will fit. I'm sure Centri is somewhat conservative in their recommendations, but you will get losses (restriction) with anything you put on. The question is how much is acceptable. All of the losses can be calculated but it gets complicated (easiest would be to model it using computation fluid dynamics, if someone has CFD software available). IMO, it really comes down to what you can fit - larger the better and minimize bends, obstructions, change in cross-sectional area, rough surfaces, etc.
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Old July 14th, 2007, 09:29 PM
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Jack Walter
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I've got a Centri Pre-cleaner on my 300Tdi - It's about 8 inches in diameter and sits on top of a custom built 3" diameter aluminum snorkel tube. I can't remember teh exact model number but I've got it around here somewhere.
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  #7  
Old July 15th, 2007, 12:10 AM
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Clark Bowen
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How will does it work Jack?
Did you notice any performance dropoff at higher revs?

Clark
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Old July 15th, 2007, 03:00 AM
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Mike Hammond
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Compared to the contortions represented by the stock air trunking from the wing to the air filter alomst anything would give increased airflow. There are most twists and turns than you can shake a stick at and restrictions down to around 1" x 3" if I remember correctly. It was a real pain to get the trucking fitted between the inner wing and the heater box, ( bear in mind I'm talking RHD & 200 tdi here), several push fit connections that would never be properly water tight without lots of silicon sealer.
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Old July 15th, 2007, 11:43 AM
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Jack Walter
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Quote:
Originally Posted by cdb
How will does it work Jack?
Did you notice any performance dropoff at higher revs?

Clark
No performance issues except when the panties get snagged on it - plus having to change the air cleaner element a lot less often - it's very high on the cool points and the other D-90 owners with the "less manly" 2-1/2 diameter ones exhibit some form of snorkel envy occasionally...
Actually given the restrictions in the stock intake tract I think the 2-1/2" system should be fine - I just enjoyed building something a little different.
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Old July 15th, 2007, 12:20 PM
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Jack - I'm curious why you went through the passenger side. Most snorkels I've seen are on the driver's side. I've been told that the passenger side snorkels are more intrusive to your visibility. That might not apply to yours though since it is custom. Anyway, I'm debating on mine since I'd like to keep the overall length (from air cleaner to top of snorkel) as short as possible. With the 2.8, the air cleaner is on the passenger side so that would make sense. But the turbo is actually on the driver's side. So the optimum would be to relocate the air cleaner to the driver's side, and run the snorkel from there. Just don't know if it will all fit or not.
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Old July 15th, 2007, 03:26 PM
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Jack Walter
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The stock intake position for a 300Tdi is through a grill in the side of the passenger side fender so I just made it to pick up the stock intake location. There is a hose that runs from the air cleaner housing to teh inside of the passenger fender.

I tucked the tube for the snorkel back and outboard of the right side window post. From the drivers seat you can just see about 3/8 of an inch of the leading edge of the snorkel tube. The mirror clears it nicely when you open the door. That took a lot of careful fitting to get it right - I spent almost a week building the darn thing. I built it one joint at a time and got a friend of mine to do all the tig welding for me - The Centri precleaner was about $150 - no telling what the rest of this thing would cost if I hadn't built it myself.
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