- Written by webmin
It’s been a few months since our friend David Greenlees posted the above photo of a mystery engine to the H.A.M.B.’s awesome and lengthy History of auto racing, 1894-1944 post, and we’re no closer to a solid answer explaining the engine’s design now than we were then. David noted that the photograph’s caption identifies the man as Giuseppe Merosi from Alfa Romeo, and he pointed out that the magneto (toward the right of the photograph) only has two leads, to what appear to be the rear-most two cylinders. The intake appears to be common among all six cylinders (snaking upward to meet the two rearmost cylinders), and each cylinder appears to have its own appropriately sized exhaust pipe. What’s most unusual about the design of the engine is that the forward cylinders appear to have just one valve per cylinder. David wrote:
From what we can see it appears to have one cam for the vertical intake valves on this side of the engine. We cannot see the other side to verify it but this engine may have NO EXHAUST VALVES.
If you look again at least on the rear two cyls. the exhaust stubs are connected to an area on the side of the cyl. that appears to have a port which is probably near the bottom of the pistons stroke when the crankshaft is at bottom dead center (BDC).
I have read about it before and I think part of what they were trying here is to let the pressure still left in the charge that had already fired to exhaust itself when the piston was at the bottom of its stroke. When the piston was in this position and dwelling there as the crank approached and passed BDC I believe during this time the exhaust exited thru these ports and the exhaust stubs which would have been above the top of the piston at its lowest position of the stroke.
This engine may have had exhaust valves on the other side and if so what they were trying out this system to see if the bottom ports helped with the exhaust. This was tried by others and I think some Indian racing bikes used this system also. Some engines just had an open port in the side of the cyl. wall at the bottom for this but it was reported to be very noisy and dirty.
Regardless these experiments were not a success because these systems were all abandoned I believe by 1920.
We will never know of course as we cannot see the other side to see if it has exhaust valves.
Whatever was going on here it was very time consuming to build this engine. It appears to maybe have a common crankshaft (probably with different strokes front & rear) but it has two different gear drive trains for the cams on each end for the front four cyls. and the rear two.
It could possibly have a supercharger or some form of blower hiding on the other side. One other possibility is that this could also have been a two stoke engine as they were being experimented with at this time and later.
With the long intake manifold feed from only one end it must have something like this as you would think that the cyls. at the end would be somewhat starved of a decent charge. This could also explain the gauge which may have read pressure if it was set up this way. If not it may have been a vacuum gauge.
Hopefully some Alfa expert out there that can shed some light on this unique engine.
The other mystery to this photo concerns the date at the bottom right of the photo, which could either be 28.August of 1900 or 28.August of 1906, both of which predate Alfa Romeo’s existence. Merosi did indeed become Alfa’s chief designer upon the formation of the company in 1910. H.A.M.B. member Vitesse noted that Merosi was with Orio & Marchand in 1900 and with Bianchi in 1906, while member psalt suggested that the engine looks very similar to the 1906 Dolphin engine developed by Sir Harry Ricardo:
a stratified two stroke with pumping and working cylinders. The exhaust valves were mechanical and the intakes automatic or atmospheric. The pumping cylinders deliver a delayed charge to the working cylinders through read valves. The benefit was good low speed idle without a heavy flywheel.
Right about there, however, is where the speculation ends. Anybody out there want to take a stab at identifying the engine and then telling us what Merosi’s involvement with it was?