Has anyone tried this?
Has anyone tried this?
(OP)
I have been taken on myself to do a refresher in port configuration as it relates to airflow dynamics. I am about to "port" a cylinder head on a vintage racer and since it's been about 20 years since I did one of these I thought I would catch up on some "modern theory". In my research, I found something that, even at my age, totally surprised me. This is a partial quote from an article in 1993.
"There's another way to get airflow, but not by changing the head or manifold. (We)...found that the pressure plate in a tight bellhousing kicked out 700 CFM of 10 PSI air pressure at 7000 RPM. Races have been won that way---with the exit from the bellhousing somehow linked to the bottom of the air cleaner. How much will it put out? If you get serious about the (design)..., how about 30 PSI at 7000 RPM?" Smokey Yunick.
Rod
"There's another way to get airflow, but not by changing the head or manifold. (We)...found that the pressure plate in a tight bellhousing kicked out 700 CFM of 10 PSI air pressure at 7000 RPM. Races have been won that way---with the exit from the bellhousing somehow linked to the bottom of the air cleaner. How much will it put out? If you get serious about the (design)..., how about 30 PSI at 7000 RPM?" Smokey Yunick.
Rod





RE: Has anyone tried this?
Hmm, not a bad move efficiency wise, a big slow supercharger is more likely to be efficient than a small fast one.
Let's see, say the blades are 25mm deep, and the clutch is 280mm across, then the crude swept volume is 25*pi*140^2*7000
=380 cfm, with no compression. Well, that's in the right ballpark
2 litre engine at 7000 rpm will need 250 cfm
a 3:1 pressure ratio is no mean feat. I'd be looking at the compressor stage of Whittle's gas turbine, or the Nene, for inspiration, ie an axial/radial design.
Make this one work and you'll be a legend. Or even more of a legend. I'd love to be the scrutineer.
Cheers
Greg Locock
RE: Has anyone tried this?
It's not a supercharger, it's a clutch cooling device. HONEST. Would I kid you.
Regards
pat pprimmer@acay.com.au
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RE: Has anyone tried this?
Yup.
Cheers
Greg Locock
RE: Has anyone tried this?
RE: Has anyone tried this?
RE: Has anyone tried this?
I met him once when we were at tech inspection for the Mission Bell 250 Trans Am race in 1968 and listened to him talk (argue with John Timanus, mostly) for several hours. If my opinion is worth anything, that man knew what he was talking about. If he told me the moon was a head of lettuce---I'd go buy a bottle of Newman's Own ! How many builders would try to pass off a sub-scale Camaro at a Trans Am event? Indeed, how many builders would have even THOUGHT of it? Smokey did! That particular car now belongs to Vic Edelbrock. I could go on and on as his stories are legend. He was truly the "Real Deal" !!!
Rod
RE: Has anyone tried this?
RE: Has anyone tried this?
The pressure difference and flow rate suggested equates to a lot of power. This comes from the engine so you're not getting anything for nothing.
However, the issue is whether the clutch would absorb this power even if the bellhousing was not connected to the inlet tract. Aerodynamic drag is not my speciality, but I recall that a stalled compressor turbine absorbs much less power than when delivering useful airflow. This is because blades (or any shape) thrashing about in stagnant air aren't doing much work. They 'attach' to a disk of (relatively) static air which just whirls round as one entity. There's not much energy change.
So maybe the issue is that if you drill big holes in the bellhousing for cooling, the clutch becomes an air compressor and you're losing lots of power. So routing the air into the inlet tract is a really good idea if it improves volumetric efficiency.
But possibly, sealing the bellhousing to prevent it working as a pump would stop most of the power loss in the first place - if you can live with the clutch temperature problems. Sealed bellhousings don't seem to get uncomfortably hot just from running at high speed.
Am I way off beam with this explanation?
John
RE: Has anyone tried this?
Cheers
Greg Locock
RE: Has anyone tried this?
I have my experimental thinking cap on as my 850 cc trials car needs all the help it can get at the top end. I have optimised the engine's output for the bottom and mid-range. This will presumably be more akin to a turbo-charger than a crank driven supercharger, which might well show some overall benefit.
I am concerned about the thought of clutch plate effluent going through the engine though, the friction material contains mineral and metal particles and is no doubt highly abrasive. The pressurised outflow (sorry, used coolant air), requires at least a separate air filter prior to reaching the engine intake.
It might be possible or more likely, necessary, to weld on vanes to the clutch cover and to fit a "scoop" to the outlet pipe to increase the flow of "cooling" air outflow.
I see a long-term project coming up.....