What is an H16 engine and how does it work?

If you think a rotary is quirky, wait until you get a load of this

2y ago

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There have been some crazy experimental engines designed for motorsport, with engineers messing around with cylinder number, cylinder layout and some even redesigning the whole IC mantra with a Dorito-shaped rotary.

Although F1 is now constricted to V6 turbo powertrains, back in the day the rulebook was much more open.

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There were heavily turbocharged inline-fours, balanced naturally aspirated V12s and even supercharged V16s at the top of the cylinder count tree. V8s became the bread and butter of the paddock however, especially after the success of the Climax-engined Lotus 25 in the early 60s, followed by the legendary Cosworth DFV motor. The tiny Climax and BRM 1.5-litre V8s screamed Jim Clark and Graham Hill to numerous Grand Prix wins, but change was on the horizon.

The FIA decided to increase the engine displacement limit from 1.5- to 3.0-litres. BRM had been using 1.5-litre V8s produced in-house at this point and decided that it was such a great engine that all they needed to do was double it to keep the run of success going. Lotus also continued sourcing engines from BRM, so this new development would certainly concern them too.

A V16 was deemed far too long and lacked the torsional rigidity to sit in the BRM and Lotus chassis, so the guys at BRM decided to experiment.

First, they flattened their V8 into a 180-degree V8 (not to be mistaken for a flat-eight, seeing as its pistons shared crankpins). Then, to meet the displacement limit, they placed another 180-degree V8 slap bang on top, creating a flattened V8 sandwich.

And, through the way it looked from the front, this new engine became known as the BRM P75 H16. This layout is not to be confused with the H6 engine we've seen from Subaru - that's just a flat-six. The P75 was instead a double decker beast that brought some serious mechanical engineering complications to the garages of BRM and Lotus.

The H16 worked by both blocks having their own crankshafts which were then connected with a gearing system containing three sprockets.

Each cylinder head had its own twin cam system too. Add in the fuel injection and having to leave space for a suitable exhaust system and you have one of the most complex engines ever seen in motorsport.

The biggest problem that the H-block had was its extremely high centre of gravity. The upper portion of the engine block and the need to mount the entire engine high to allow space for the exhaust system below meant that the placement was nowhere near where it needed to be to produce a championship-contending car.

The engine will have tugged and heaved at the BRM and Lotus cars during cornering, hindering them from staying stable and fast through the bends by causing adverse roll and pitching.

The P75 had to exhaust both sides of the engine, leading to the whole block being raised to accomodate the lower piping.

The P75 had to exhaust both sides of the engine, leading to the whole block being raised to accomodate the lower piping.

Crankshaft vibrations within the engine weren't ideal either and the quick solution only made things worse. Specially positioned counterweights were placed along the crankshafts to try and balance out the unwanted forces, but these small lobes had a tendency to fly off during a race, clattering around the engine and causing catastrophic damage.

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Each side of the H-block needed its own radiators, water pumps, distributor and fuelling system, with virtually the only component shared being an oil cooler.

In terms of stats, the H16 actually brought home some decent numbers. At its peak, it produced 420bhp at 10,500rpm which put it up there with the Ferrari and Honda engines of the time. Sadly, the bloody heffer initially weighed a whopping 252kg, being reworked over the season to bring it down to a still monstrous 181kg.

I would not want to be the engineer in charge of keeping this thing alive.

I would not want to be the engineer in charge of keeping this thing alive.

On top of the weight and COG drawbacks, the complexity of the engine led to a woeful reliability record. Cars bearing the H16 engine retired 30 times from 40 starts, with 27 of those down to mechanical issues.

Jackie Stewart himself said of the engine in his BRM: "It was unnecessarily large, used more fuel, carried more oil and needed more water - all of which added weight and diminished the vehicle's agility".

The H16 did have its one moment of glory in F1 at the hands of the late, great Jim Clark. He won the 1966 US Grand Prix in the H16-powered Lotus 43, but that race was the only time Clark finished a race using the quirky engine layout.

Jim coaxing the Lotus 43 and H16 engine to their only win at Watkins Glen in '66.

Jim coaxing the Lotus 43 and H16 engine to their only win at Watkins Glen in '66.

Although H16s were much more prominent in the aeronautical industry, it sadly never got off the ground in the motoring world. Much like the Subaru flat-12, it simply had too many engineering drawbacks to justify using such a setup at the pinnacle of motorsport, meaning that the technology never really trickled down into road cars of the time.

From a car nerd's point of view however, this kind of stuff gets my engineering senses tingling. And if I stumble across a Lotus 43 or BRM P83 at Goodwood, I'll be sure to give it a thorough looking over.

Do you know any quirky engine layouts that I should investigate next? Drop them into the comments below!

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Comments (17)

  • You should be doing the engine layout in the chaparral 2J Le man car. It had an engine for drive and a snow making machine engine in the back to power two fans under the car sucking it into the ground I’d like to se you find some info on this.

      2 years ago
  • Kind of reminds me of the Napier Sabre engine. It might have been an inspiration. That was 24 cylinders though but similar in a way. Powered some of the RAF most powerful fighter aircraft of ww2. Not sure they had similar issues to BRM, but an interesting concept all the same.

      2 years ago
    • Ah yes, the Hawker Typhoon engine? I guess the weird centre of gravity wouldn't have been as much of an issue in the air than when in a hunkered down F1 car.

        2 years ago
  • www.gordontronson.com That guy does some work that is interesting.

      2 years ago
  • They should have just copied the basic architecture of the WW2 Napier Sabre engine. That was a H24, but it was much more reliable than the earlier Napier Rapier X24 or the Rolls-Royce Vulture X24.

      2 years ago
  • Very cool looking engine. I'm sure the mechanics were tired of this thing after the first couple of races.

      2 years ago
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