Lotus Elan

Air intakes and filters; learn from the bikers

PostPost by: lotuselan2 » Thu Mar 15, 2007 3:42 am

See the attached link from a Ducati web site discussing air intake plenums, air filters and related topics. My son, a former bike racer, sent it to me after we discussed my +2 air intake box. Link:
http://www.desmoducati.org/airfilter.html

Some items of note:
-They are discussing a 1000 cc 2-cylinder bike motor versus our 2 times 800 cc motors.
-After measuring the clearance from my #4 bell mouth to my intake housing my son declared the spacing was good, but he worried about the box's total volume. The 130% rule mentioned in this article eliminates my worry on this front since my air filter is in the nose with a long hose run to the air box.
-If you have twin K&N's or similar air filters, chick your volume versus the +/- 800 cc times 1.3 suggested.

Adjust your thinking to our situation as this article is not only for bikes but a specific bike. Take advantage of on-going development from a current source.
Ken
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PostPost by: RobCapper » Thu Mar 15, 2007 9:07 pm

whilst you mention the subject, what are the pros and cons of disposing with the airbox all together, and replacing it with a couple of the oval webber filters from Demon Tweaks? It's what my trusty mechanic suggested, and knowing nothing about it, it only seems good - more noise from the carbs, poss more power... why an air box?
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PostPost by: types26/36 » Thu Mar 15, 2007 9:18 pm

RobCapper wrote: why an air box?


1. A slight ram effect from higher air pressure zone (nose of car)
2. An unheated supply of air drawn from in front of radiator.
Possible other advantages which I cant think of now :roll:
Oh! of course, sacrilege to the purest
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PostPost by: berni29 » Thu Mar 15, 2007 11:55 pm

Hi There

On the standard airbox, I have always thought that the clearance to no4 carb is very tight. Also the trunking gets a bit crushed as it passes by the radiator. I did look into getting some Samco silicone hose. has anyone tried this stuff? Apparently it can be bought with a pre-formed angle at the end so that it will mate up with the air filter in the nose. The problem with the K&N type filters (for me) is the unacceptable intake noise. There is someone on ebay selling modified standard type boxes that give more clearance to no4. I might modify my own one if I get bored enough or run out of things to fix on the car (right!)

Berni
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PostPost by: archigator » Fri Mar 16, 2007 3:32 am

I bought some great air duct hose from www.intense-racing.com

http://www.intense-racing.com/Merchant2 ... ry_Code=IF

Works great, looks close to stock, and doesn't "scrunch up" as it makes its way past the radiator. I also originally had individual K&N's on my Webers, but read somewhere that there is a danger of backfire and potential gas leakage into the filters that is somewhat mitigated by using a sealed airbox setup.

Gary
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PostPost by: hethelfan » Fri Mar 16, 2007 11:06 am

Cliveyboy does a KN filter conversion to replace the air cannister at the front. He also has some flexible ducting which i bought from him at stoneleigh its very good quality and really flexible.
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PostPost by: lotuselan2 » Fri Mar 16, 2007 1:37 pm

My son has done a lot of dyno testing on race bikes and tested many air filter arrangements on bikes and also American V-8's. I discussed the Nr. 4 gap from the bell mouth to the air box. We measured mine as a bit over 1". His feeling is that that is more than adequate based on his dyno work. That is when he referred me to the Ducati article about the upstream volume being critical. What the Ducati people would say is that the air will accelerate to Nr. 4 bell mouth but without significant pressure drop.

I have a very large K&N in the nose of my car and the trunking is a bit crimped but still has a very large open area at the smallest diameter. Remember, only one cylinder is pulling at a high rate at any one time.
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