Two-stroke gen­er­a­tor

New patent by Honda sug­gests a sim­ple, clean, over-stroked en­gine that can burn diesel

The Witness - Wheels - - FRONT PAGE - LOZ BLAIN

TWO-STROKES are far sim­pler ma­chines than four-stroke en­gines.

They’re also lighter, eas­ier to work on, and down­right an­grier, pump­ing out a lot more power per cu­bic cen­time­tre of dis­place­ment, which has won them a lot of fans.

But they’ve had a rep­u­ta­tion for belch­ing out a fair bit of smoke and un­burnt fuel, a sit­u­a­tion that just couldn’t fly along­side tight­en­ing emis­sions reg­u­la­tions around the world, so they’ve fallen out of favour.

But now there’s hope. Ear­lier this month, Honda sub­mit­ted a patent ap­pli­ca­tion for a brand new two-stroke mo­tor that uses di­rect fuel in­jec­tion for a cleaner burn and bet­ter pis­ton cool­ing. We may yet see a res­ur­rec­tion of the ring-dingers.

Un­cov­ered by ea­gle-eyed patent hawks at Morebikes, the new patent de­scribes a new twostroke en­gine with a fuel in­jec­tion sys­tem mounted on the back of the cylin­der, point­ing up­wards to­ward the back wall of the cylin­der bore.

The in­jec­tor is set to spray the fuel when the pis­ton is near top dead cen­tre, so that un­burnt fuel won’t get swept out with the ex­haust gases, and the fuel is aimed such that the cylin­der and pis­ton can both be par­tially cooled as the fuel evap­o­rates against them.

Honda be­lieves this de­sign can help elim­i­nate some of the com­plex­ity of other in­jected twostroke de­signs, help­ing bring the pro­duc­tion and main­te­nance costs down and po­ten­tially mak­ing them rel­e­vant for man­u­fac­ture again.

It’s widely be­lieved that Husq­varna and KTM, among oth­ers, are sit­ting on in­jected two-stroke mo­tor de­signs and wait­ing on the right time to de­but some­thing.

But word is KTM ex­pects its in­jected two-strokes to be so com­plex that they’ll end up be­ing as ex­pen­sive and heavy as a fourstroke en­gine, which could well kill de­mand.

Per­haps with this de­sign, Honda has man­aged to break down some of that com­plex­ity and find a pack­age that can welcome the braap­pers back into the mod­ern mo­tor­cy­cle land­scape.

But lan­guage in this Honda patent, as well as the de­sign draw­ings, sug­gest that this might not be con­ceived as a mo­tor­cy­cle en­gine at all — at least, not in its cur­rent form.

In the first back­ground para­graph of the ap­pli­ca­tion, Honda states that “the two-stroke en­gine is of­ten pre­ferred over the four-stroke en­gine in the field of gen­eral pur­pose en­gines be­cause of the sim­plic­ity in the struc­ture”.

The di­a­gram in­cluded would seem to show a long-stroke en­gine with a pushrod valve sys­tem and a thick mount­ing flange at the bot­tom. In ad­di­tion, the patent word­ing states that “the liq­uid fuel may con­sist of diesel oil or any other fuel that is pro­vided with a lu­bri­cat­ing prop­erty”.

All of which points to­ward an in­dus­trial gen­er­a­tor-type ma­chine rather than a high-per­for­mance mo­tor­cy­cle en­gine.

Even so, it shows Honda is still look­ing to in­no­vate and de­velop in the two-stroke world — and there is most cer­tainly a mar­ket that would love to see ef­fi­cient, clean two-strokes come into the mod­ern era. Stay tuned.

— Giz­mag.

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