Sizing cold air intake
Sizing cold air intake
(OP)
I hope I'm not breaking any rules, I posted this to "Automotive body" in error.
thruthefence (Aerospace) Aug 31, 2010
I'm interested in providing a 'fresh air' inlet for my Lotus Europa Toyota engine conversion. The engine is a twin cam four cylinder 1500 CC, mid engine configuration,winds pretty tight, I expect 7500 RPM or so "in anger" although this is not a race car. I am using the stock AFM, the inlet of which measures 2" X 2" at the 'swinging gate'.(sort of like an old Bosch). Is there a rule of thumb for the size inlet needed? I'm not expecting ram recovery, or any such nonsense, but the space limitations will require me to turn the airflow appox 90 degrees (through a filter box)to feed the actual intake plenum (using four individual throttle bodies) My boy-racer "naca like" submerged duct feeds two 3" flex ducts, which will terminate at the air filter enclosure. Is 1/3 greater area enough to prevent starving the engine of air?
thruthefence (Aerospace) Aug 31, 2010
I'm interested in providing a 'fresh air' inlet for my Lotus Europa Toyota engine conversion. The engine is a twin cam four cylinder 1500 CC, mid engine configuration,winds pretty tight, I expect 7500 RPM or so "in anger" although this is not a race car. I am using the stock AFM, the inlet of which measures 2" X 2" at the 'swinging gate'.(sort of like an old Bosch). Is there a rule of thumb for the size inlet needed? I'm not expecting ram recovery, or any such nonsense, but the space limitations will require me to turn the airflow appox 90 degrees (through a filter box)to feed the actual intake plenum (using four individual throttle bodies) My boy-racer "naca like" submerged duct feeds two 3" flex ducts, which will terminate at the air filter enclosure. Is 1/3 greater area enough to prevent starving the engine of air?





RE: Sizing cold air intake
The bigger the plenum, the less restrictive the ducting will be as you smooth out pulses and therefore lower peak airflow velocities.
Regards
Pat
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RE: Sizing cold air intake
You should red flag your other post so only one is running. I agree this is the more appropriate area.
It looks a lot better if you red flag the other one yourself before some one else does it to you.
Regards
Pat
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RE: Sizing cold air intake
Steve
RE: Sizing cold air intake
RE: Sizing cold air intake
Regards
Pat
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RE: Sizing cold air intake
Might be worth thinking about which has the most effect on power.
Cheers
Greg Locock
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RE: Sizing cold air intake
Insulating the air ducts and IM can help.
Regards
Pat
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RE: Sizing cold air intake
RE: Sizing cold air intake
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
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for site rules
RE: Sizing cold air intake
Usually the diameter of the inlet is whatever the throttle body o.d. is, and the length and access to cold air is what tunes in the power curve. Up to 7500rpm, 30-34" should work well. A 2"x2" square is equivalent to Ø2.25 tube, so 2.5" (64mm) dia should be okay.
RE: Sizing cold air intake
I have a 197+hp/132lb/ft Lotus 1600 twincam in our Lotus Cortina. Never used more than one 3 1/2" tube to feed the fiberglass air box over the two 45DCOE's and we red line at 8600 rpm.
We did put an 18RG in a MkII Cortina years back with a stock ~3" inlet hose. Street only, no problems.
Looking at the photos of a JPS Europa, I should think the stock twincam inlet and filter would perform adequately with your engine conversion.
Rod
RE: Sizing cold air intake
RE: Sizing cold air intake
Rod
RE: Sizing cold air intake
RE: Sizing cold air intake
I wouldn't mind owning one. Made a few years ago down here in San Diego and on the market for reallllly cheap considering how sophisticated they are.
Rod
RE: Sizing cold air intake