H engine

<h2 id="design">Design</h2>

<p>The benefits of an H engine are the ability to share common parts with the flat engine upon which it is based, and the good <a href="/facts/Engine_balance/PUNddFnh">engine balance</a> which results in less vibration (which is difficult to achieve in many other types of four-cylinder engines).<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a>
</p><p>However, H engines are relatively heavy and have a high centre of gravity. The latter is not only due to the second crankshaft being located near the top of the engine, but also the engine must be high enough off the ground to allow clearance underneath for the exhaust pipes.
</p><p>The <a href="/facts/U_engine/8ekDM5hH">U engine</a> layout uses a similar concept, placing two <a href="/facts/Straight_engine/T1537bJF">straight engines</a> side-by-side.
</p>
<h2 id="history">History</h2>
<h3>Aircraft engines</h3>

<ul><li><a href="/facts/Lycoming_Engines/8423nY4W">Lycoming</a>, US
<ul><li><a href="/facts/Lycoming_H-2470/Y707cSAE">Lycoming H-2470</a> H-24 "<a href="/facts/Hyper_engine/3IfEWkcq">hyper engine</a>" (1930s) 2,300 hp (1,700 kW)</li></ul></li>
<li><a href="/facts/Fairey_Aviation/yqxRgUmb">Fairey Aviation</a>, UK
<ul><li><a href="/facts/Fairey_Prince_(H-16)/4PH3qThm">Fairey Prince (H-16)</a> (1939) – 1,500 hp (1,100 kW)</li>
<li><a href="/facts/Fairey_Monarch/N6BlT9Qg">Fairey Monarch</a> (1939) – H-24 2,240 hp (1,670 kW)</li></ul></li>
<li><a href="/facts/Kl%C3%B6ckner-Humboldt-Deutz_DZ_710/1ze0942J">Klöckner-Humboldt-Deutz DZ 720</a> – H-32, 102.9 litres diesel</li>
<li><a href="/facts/D._Napier_%26_Son/26MHYApR">D. Napier & Son</a>, UK.
<ul><li><a href="/facts/Napier_Rapier/GmCtvoIk">Napier Rapier</a> (1929) – H-16 air-cooled vertical, 8.83 litres 340 hp (250 kW)</li>
<li><a href="/facts/Napier_Dagger/W3HaR7mW">Napier Dagger</a> (1934) – H-24, air-cooled vertical, 16.85 litres 890 hp (660 kW), a development of the Rapier</li>
<li><a href="/facts/Napier_Sabre/3cVux5Sl">Napier Sabre</a> (1938) – H-24, water-cooled horizontal sleeve valves, 36.7 litres 3,500 hp (2,600 kW).</li></ul></li>
<li><a href="/facts/Pratt_%26_Whitney/DI4FhYep">Pratt & Whitney</a>, US
<ul><li><a href="/facts/Pratt_%26_Whitney_X-1800/aEN0Nl9I">XH-2240</a> - H-24, liquid-cooled,</li>
<li><a href="/facts/Pratt_%26_Whitney_X-1800/aEN0Nl9I">XH-2600</a> - H-24, liquid-cooled,</li>
<li><a href="/facts/Pratt_%26_Whitney_XH-3130/cTnm1DHA">XH-3130</a> - H-24, liquid-cooled,</li>
<li><a href="/facts/Pratt_%26_Whitney_XH-3130/cTnm1DHA">XH-3730</a> - H-24, liquid-cooled,</li></ul></li>
<li><a href="/facts/Rolls-Royce_Eagle_(1944)/cDArxUW4">Rolls-Royce Eagle</a> (1944) – H-24, 46.2 litres, 3,200 hp (2,400 kW).</li></ul>
<h3>Formula One racing engines</h3>
<p>The <a href="/facts/British_Racing_Motors/96CBl0ko">British Racing Motors</a> (BRM) H-16 Formula One engine won the 1966 US Grand Prix in a <a href="/facts/Lotus_43/7BSUYaaU">Lotus 43</a> driven by Jim Clark.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> It was also used by the unsuccessful 1966 <a href="/facts/BRM_P83/3xuoTIbJ">BRM P83</a> car driven by Graham Hill and Jackie Stewart. As a racing-car engine it was hampered by a high <a href="/facts/Center_of_gravity/n4Lr9GAz">center of gravity</a>, and it was heavy and complex, with gear-driven twin overhead cams for each of four cylinder heads, two gear-coupled crankshafts, and mechanical fuel injection.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a><a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
</p>

<h3>Motorcycle engines</h3>

<p>The <a href="/facts/Brough_Superior_Golden_Dream/VjDDBTyC">Brough Superior Golden Dream</a> motorcycle, first shown in 1938.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> A 1,000 cc H-4 design and a few units were produced in early 1939. Any development planned was interrupted by World War II and subsequent years of austerity.
</p><p><a href="/facts/Wooler_(motorcycles)/IsgqB1zU">Wooler</a> built a motorcycle prototype with a similar configuration to the Brough Superior Golden Dream and exhibited it at the <a href="/facts/British_International_Motor_Show/gl86yxMg">British International Motor Show</a> at <a href="/facts/Earls_Court_Exhibition_Centre/Gto3WnMc">Earls Court Exhibition Centre</a> in 1948 and again in 1951. This was replaced by a <a href="/facts/Flat-four_engine/ooHjdXTx">flat-four engined</a> prototype at the 1953 show.
</p>
<h3>Powerboat racing engines</h3>

<p>German firm Konig, who specialised in racing outboard motors,<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> built a few 1000cc  H-8s in the 1970s, which were basically two of their VC500 flat fours mounted one above the other, with the direction of rotation reversed on one of them. Each half of the engine was a water cooled 2-stroke with rotating disc valve driven by a toothed belt via two 45/90 degree pulleys, plus two siamesed expansion chamber exhausts, fed by two single choke carbs. Both cylinders at each end of each engine fired at the same time, hence the siamesed exhausts for each pair.
</p>
<h2 id="other-engines-named-h">Other engines named "H"</h2>
<p>Subaru has marketed its <a href="/facts/Flat-four_engine/ooHjdXTx">flat-four</a> and <a href="/facts/Flat-six_engine/eRzmnBTW">flat-six</a> engines as "H4" and "H6" respectively. The letter "H" in this case refers to "horizontally-opposed", an alternative term for <a href="/facts/Flat_engine/MMHDYBzH">flat engines</a>; these engines can also be said to look like a "H" or conjoined "H"s, albeit from the top and in schematic form.
</p><p>The <a href="/facts/Saab_H_engine/AFKLKmgh">Saab H engine</a> is a <a href="/facts/Straight-four_engine/NVgxSDFb">straight-four</a> engine produced from 1981 to 2009. The letter "H" represents "high compression".
</p>

Wikimedia Commons has media related to H engines.

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Willoughby, Vic (1989). Classic motor cycles. Ivy Leaf. ISBN 0-86363-005-7. <a href="0-86363-005-7" target="_blank">0-86363-005-7</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>"BRM engines H16". Members.madasafish.com. Retrieved 2010-09-12. <a href="http://members.madasafish.com/~d_hodgkinson/brm-e-H16.htm" target="_blank">http://members.madasafish.com/~d_hodgkinson/brm-e-H16.htm</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Taylor, Roger. "Lotus 43 & B.R.M. 83". Model Cars (July 1967): 327. Archived from the original on 26 March 2016. <a href="https://web.archive.org/web/20160326130659/http://vsrnonline.com/mags/mc/Vol4/V4N7/MC_V4N7_p327.jpg" target="_blank">https://web.archive.org/web/20160326130659/http://vsrnonline.com/mags/mc/Vol4/V4N7/MC_V4N7_p327.jpg</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Taylor, Roger. "Lotus 43 & B.R.M. 83". Model Cars (July 1967): 328. Archived from the original on 4 March 2016. <a href="https://web.archive.org/web/20160304185506/http://www.vsrnonline.com/mags/mc/Vol4/V4N7/MC_V4N7_p328.jpg" target="_blank">https://web.archive.org/web/20160304185506/http://www.vsrnonline.com/mags/mc/Vol4/V4N7/MC_V4N7_p328.jpg</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Wilson, Hugo (1995). "Brough Superior Dream". The Encyclopedia of the Motorcycle. London: Dorling Kindersley. pp. 34–35. ISBN 0-7513-0206-6. <a href="0-7513-0206-6" target="_blank">0-7513-0206-6</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>"Quincy vs Konig". www.quincylooperracing.us. Retrieved 16 November 2019. <a href="http://www.quincylooperracing.us/gpage8.html" target="_blank">http://www.quincylooperracing.us/gpage8.html</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
</ol>

H engine open-in-new

H engine