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Re: BRM V16
Posted: 12 Sep 2022, 03:26
by johnny comelately
gruntguru wrote: ↑11 Sep 2022, 23:05
saviour stivala wrote: ↑08 Sep 2022, 21:43
Inlet valve 31.8mm. exhaust valve 37.8mm.
Pretty sure the inlet valve was larger than the exhaust - like most engines.
Just a typo, everything I type has them mandatorily
Re: BRM V16
Posted: 12 Sep 2022, 05:19
by saviour stivala
gruntguru wrote: ↑11 Sep 2022, 23:05
saviour stivala wrote: ↑08 Sep 2022, 21:43
Inlet valve 31.8mm. exhaust valve 37.8mm.
Pretty sure the inlet valve was larger than the exhaust - like most engines.
Yes. it was a typo between inletand exhaust sizes.
Re: BRM V16
Posted: 12 Sep 2022, 23:13
by Billzilla
With those valve and bore diameters, the valve timing must have little-to-no overlap. Looking at the cross-section of the heads in that first video pretty much confirms that I think. Small amounts of lift with one valve seems to largely preclude the other from lifting as well.
Re: BRM V16
Posted: 12 Sep 2022, 23:31
by johnny comelately
Billzilla wrote: ↑12 Sep 2022, 23:13
With those valve and bore diameters, the valve timing must have little-to-no overlap. Looking at the cross-section of the heads in that first video pretty much confirms that I think. Small amounts of lift with one valve seems to largely preclude the other from lifting as well.
Yes, we call that the clip, for obvious reasons
Re: BRM V16
Posted: 13 Sep 2022, 01:24
by Tommy Cookers
Billzilla wrote: ↑12 Sep 2022, 23:13
With those valve and bore diameters, the valve timing must have little-to-no overlap. Looking at the cross-section of the heads in that first video pretty much confirms that I think. Small amounts of lift with one valve seems to largely preclude the other from lifting as well.
yes ...
neither the exhaust valve period (that I quoted) nor the exhaust system design correspond to large overlap
ie they were normal for the supercharged era
the era started by Mercedes & Fiat c.100 years ago - (the 2 valve large VIA fashion came from NA Fiat design diaspora)
at first boost was at limited to high rpm only
https://motorsportmagazine.com/archive/ ... -1922-1925
(btw the very successful Sunbeam (NA 2 litre) GP car had a 3 speed gearbox (saving length/weight) ...
some earlier famous NA cars ie Peugeots had such large ports and valves they had 5 speed gearboxes)
(imo)
high mechanical supercharging wouldn't develop worthwhile 'tuned length' exhaust effects
then with NA F1 (emulating GP motorcycles) overlap became important and designers chose smaller VIAs