Candid Cameron

CANDID CAMERON

When reading Kevin Cameron's Sporthike Perfhrinance handbook, I came across the section on Ram Air. which lie claims does not have a meaningful effect on real-world power. It all made complete sense to me, but I am curious: Is this a fact or just his `opinion"? It would be nice to know. Tommy Brock Jacksonville, Florida

Th'o things are happening wit/i. an airbox: 1) Rain air gets all tile publicity because oft/ic rac'~' sound qi its na/ne. Back in /929, RoIls-Roi'ce ran i/ito mixture lean-out/ram rising ram-air pressure `with their Schneider Cup air racing "R " engine. At the tiiiie, they ii'ere cible to get to about 35() nip/i, at which /)oiiit the rail/-air pressure gain is about 14 percent. As a nzeans of soli'ing this lean condition, they just included an amiaeroid capsule that controlled an enriciiinc'mit valve. Because ram air causes ci V-squared pressure gain, i/ic pressure rise at /60 or 170 iiip/i (average sporthike top s/iced) is about 3 /)erc'ent; at 8() mph, the gain is less than / percent. And bear in mimic! I/nit not all qf I/ic theoretical pressure gail! is actual/i achieved: getting 75 percent of it is considered decent. Air is taken in at high speed, then decelerated in a widening cliff user to convert the velocity energi' i/Ito pressure. 2)/ft/ic airbo,v is designed to resonate (its pressure rising cimid /blliiig 1~() degrees out of step wit/i the engine :~ ijitake events), there can be a gcmin from the cmirbox alone, and nofbrwara'-/ac'ing imitakes cire necessary/br

II~LLJ~tLf /~Jf L4f Jt4L tli~, IVII&~(ItL..~ (11 L (1~L.( .)~)t_flI It/F tills gain. Power is increased because cadi /11k/Li S iiltaI%c C Lilt OCL1IJ S (it maximum box pressure. with the box refilling betweemi intake strokes. The gain can be substantial, /0-15 percent ii doiieproperl~ The bigger the engines iiuli~'icliuiI c~'/t nders. the bigger i/ic airbox has to be. so it hard to hai'e eiiough box ru/u/nc' on a Twin, hut that s not the case with smna/lc'r cr/inder~.

Kevi Cameron