It’s all about suck­ing and bang­ing this is­sue.

No, not what you and Polly Pretty Pants get up to in your spare time, rather, what an en­gine needs most for big power!

Fast Bikes - - CONTENTS -

Last month we talked about the im­por­tance of get­ting air out of our en­gines via ex­hausts, so this month it’s only pru­dent we dis­cuss suck­ing that air in for a big­ger bang.

Gen­er­ally, the more you can get in, the bet­ter, but the den­sity of air, al­ti­tude, hu­mid­ity and am­bi­ent tem­per­a­tures play a mas­sive part, which is why mod­ern fuel-in­jected bikes share all these ex­tra sen­sors and sen­sory tech­nol­ogy to make al­lowances for vari­ables.

A lot of bikes nowa­days use self-map­ping tech, us­ing closed loop sys­tems and lambda sen­sors to pick up ex­haust gases be­fore send­ing the info back to the ECU. The ECU then reads these sig­nals and changes the fu­elling ac­cord­ingly. The same ap­plies for MAP sen­sors (Man­i­fold Ab­so­lute Pres­sure), which mea­sures the amount of air be­ing sucked via the in­let tract, giv­ing a sec­ond in­di­ca­tion to TPS (Throt­tle Po­si­tion Sen­sor).

There are ex­cep­tions to get­ting as much air in as pos­si­ble. It de­pends on the con­di­tion of the air; that air might be slow mov­ing, and that’s the se­cret with gas flow­ing heads – get­ting air into a form that is much more ef­fi­cient than a stan­dard en­gine, so mod­i­fy­ing an in­let port or ex­haust port to in­crease the vol­ume/speed of the air pass­ing through, be it burnt or un-burnt gases.

You may think that re­mov­ing me­tal from that port will in­crease air­flow but in all hon­esty, it may re­duce it. En­gine tun­ing re­ally is a fine art. You can’t just pick up a text­book, get the Dremel out and learn how to tune a mo­tor.

As tem­per­a­tures rise, air rises with heat and the oxy­gen con­tent re­duces, and you need plenty of oxy­gen for the bang, but you need to mon­i­tor that oxy­gen con­tent (with an air tem­per­a­ture sen­sor). We are just above sea level here. If you’re be­low sea level, you’re prob­a­bly Jac­ques Cousteau. The bike has to per­form the same, whether it’s here or in the Alps where air is get­ting thin­ner and oxy­gen is re­duced, and the bike will con­stantly adapt along the way with­out sac­ri­fic­ing per­for­mance.

Very hot, hu­mid coun­tries have wet air – light air car­ry­ing less oxy­gen. Here it’s wet but bloody cold, so the air is heavy, highly oxy­genated and doesn’t want to flow very fast. So a fish out of wa­ter would last longer here than it would in, say, Malaysia. Aero­dy­nam­ics also play a part in vary­ing air types – if the air is thick, then you’ll need more force to break that air. Any­way, I di­gress.

Get­ting air into the en­gine is ob­vi­ously a vi­tal task. The eas­i­est, most di­rect way is through the head­stock, although it’s not nec­es­sar­ily the best way. Honda and Suzuki still use twin air tubes on ei­ther side, suit­ing

Some­times life sucks, just like this ram air in­take.

25th cen­tury bag­pipe?

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.