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Racing V8 Engines

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#1 blueprint2002

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Posted 10 September 2020 - 06:21

Aside from ill-starred efforts by Maserati during the 30s, and CTA-Arsenal during the 40s, the first serious Grand Prix racing V8 was the Lancia D50 of 1954, although even this set no trend. It was 1962 before BRM and Coventry-Climax produced theirs, followed by Ferrari and ATS in 1963; they had numerous successors, to the extent that other types were largely eliminated for some considerable time.

The US passenger car industry had already adopted the type wholeheartedly, developing and refining to very high standards of reliability, if not of performance. One notable feature that became universal was the two-plane, or cross-plane crankshaft, which eliminates residual secondary forces and moments, contributing to low vibration levels, and hence to long life of the engine and even of other components. (Residual primary forces and moments already being reduced to nothing, even with the flat-plane or single-plane crankshaft).

All the early racing V8s, from Lancia onwards, also featured the cross-plane crankshaft, and thus shared the same benefits. It so happened that the late 50s/early60s was also the time that the science of arranging and “tuning” of exhaust systems really matured, and on this count the cross-plane V8 was none too handy. The firing order of such engines demanded that the exhaust “headers” of cylinders L1-L4 be blended with those of cylinders R2-R3, and likewise for the other four. (All the foregoing tacitly assumes that the angle between the cylinder banks is the usual 90 degrees).

With the usual arrangement of exhaust ports on the outer sides of the cylinder heads, this necessitated a cumbersome arrangement with the headers on either side snaking back at low level, then bending around and up behind the cylinder blocks, to meet above the gearbox, where they blended into two tailpipes running backwards as far as needed. Whether on this account or not, both BRM and Coventry-Climax developed new flat-plane crankshaft versions of their engines, whose different firing order allowed each bank to function as if it were a separate four-cylinder engine, with all four pipes blending, progressively and conveniently, into a single tailpipe, one each side. Ferrari did the same, apparently without even trying the cross-plane crankshaft in competition.

Simultaneously, Ford were developing their famous “four-cam” Indianapolis V8, but they took a radically different route. Retaining the cross-plane crankshaft (perhaps because Indy is an endurance race), they tackled the exhaust layout simply by reversing the cylinder head flow, bringing the exhaust ports in, towards the centre of the engine, and angling the inlet ports outwards. Now left and right bank headers were so close together that ingenious routeing and skilful pipe-bending was necessary to blend them together within the available space. Despite appearances, the “snakepit” over the engine did not cause overheating of anything, and the engine was a resounding success. The later, turbocharged version retained this feature, and was also successful.

Paradoxically, BRM adopted a similar reversed flow through the cylinder head, but with the flat-plane crank, so that there was no blending of left and right bank headers, even though all were located in the same valley between the two banks, just like on the Ford V8. It appears that BRM wanted to clear the space low down on either side of their engine, so as to maximise the dimensions of that part of the monocoque chassis which lies in that area; also perhaps to get the exhaust headers out of the airstream. This engine, too, was as successful as could be wished, despite the formidable opposition of Coventry-Climax combined with Jim Clark and Lotus.

Whether or not he considered these precedents, Keith Duckworth also adopted the flat-plane crankshaft for his famous Ford (Cosworth) DFV, with the astonishing success that is now the stuff of legend. However, it is a matter of record that the DFV suffered from severe vibration, which resulted in failures that sound and meticulous detail engineering was able to cure, even though the vibration itself was never eliminated. It does not seem too far-fetched to conjecture that the vibration originated in the inherent qualities of the flat-plane crank.

Since that time, there have been several other Formula 1 V8 engines. To name but a few: Alfa Romeo, Ford (Cosworth) HB and Zetec-R, Yamaha, Judd, Ferrari, and so on. One change from earlier racing V8s was that some of them reduced the angle between the cylinder banks (75 degrees being popular), apparently to improve aerodynamics by narrowing the engine and thus tucking its exhaust manifolds closer in to the centre.

Very little information has been released to the public about these engines, but from the very location of the exhaust manifolds, it is almost certain that the flat-plane crankshaft has been retained. This in spite of the possibility that a central location for the manifolds could be advantageous aerodynamically, while the necessary two-plane crankshaft is advantageous dynamically. Or it would be, if the cylinder bank angle were 90 degrees. How much a smaller angle (say 72 or 75 degrees) would change the vibration characteristics can only be calculated with detailed knowledge of various internal engine dimensions and weights of moving parts.

So the question is, why stick to the flat-plane crankshaft and the resulting “outside” exhausts, when the cross-plane crankshaft offers inherent reliability and possibly aerodynamic advantage?



#2 ray b

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Posted 10 September 2020 - 19:53

novi  indy

in 1941



#3 gruntguru

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Posted 10 September 2020 - 20:55

Another advantage of the flat plane crankshaft is its simplicity. I would guess the simplicity also lends itself to strength.

#4 Lee Nicolle

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Posted 12 September 2020 - 08:52

No simplicity in a flat plane. No real advantage either. A reliabilty issue though. As mentioned Cosworths used it and spent a lot of time getting reliability. 

My engines are common V8s. In the past there was flat plane cranks available. AFAIK nothing now. 

30 years ago and more it was a fad,, cost more for no real [if any] advantage. And they viabrated a LOT more.

Nascar tried them and rejected them, AFAIK nobody ever even bothered  with a Sprintcar.

Pan warmer headers as well, tried and rejected. Though I feel there was something in that. But defeated by the complexity and lack of room under the engine. Some Speedway sedans tried them, as they can put the pipes over the bellhousing. They can put the firewall where they want. Defenitly did not hurt and they generally sounded good. But still far more complex.

There was once a Sprintcar with them. Pipes went forward, between the radiator and the engine. Sounded way different to the rest. Though that was a wet sump car, very few if any of those left now. The oil tank and all the various drives limit space in that space