Reed valve in intake = 'infinitely variable' cam timing - Fuel Economy, Hypermiling, EcoModding News and Forum

Logic · 10-06-2022, 04:41 AM

If you have a 'very hot' racing intake cam in your engine,
BUT
with a reed valve/s just behind it
then
You get self adjusting 'infinitely variable' cam timing...

Well not infinitely variable like Koenigseg's FreeValve system, but with a mild exhaust cam; pretty damn good!?

The Honda 500cc single cylinder 'Thumper' had/s such:

And Alfa Romeo (and other manufacturers) experimented with them, losing ~1kw in top end power for a vast improvement in drivability.
(35% more low end torque apparently)

In those days Reed Valves were made of spring steel.
That meant that if one broke; your engine was a goner.
You also lost some power due to the greater vacuume reqd to open the reed valve.

Nowadays we have carbon and glass fibre reed valves negating the above issues.

If your intake tract bolts to the head, it should be pretty easy to fabricate a bolt on Reed Valve Box.
A bit far from the intake valve, but much easier and simpler than the very beta open source Freevalve setup mentioned in the Freevalve thread.

Some discussion:
https://www.speed-talk.com/forum/vie...hp?f=1&t=42425

Reed valves on a 4-stroke.

I can see this making a big difference in low rpm economy..?
Has anyone here tried this??

aerohead · 10-06-2022, 12:11 PM

As a 'passive' component, in today's sophisticated world of sensors, ECUs, and servos, a non-controlled device like this might be a non-starter, and also redundant.

freebeard · 10-06-2022, 02:00 PM

Quote:

Originally Posted by Logic

Nowadays we have carbon and glass fibre reed valves negating the above issues.

IIRC carbon fiber is notoriously brittle.

aerohead · 10-06-2022, 04:01 PM

let's see if this works
http://https://ecomodder.com/forum/s...ille-7838.html
Didn't work!
A search for 'lamellar self-blocking grille' located it

Piwoslaw · 10-06-2022, 04:16 PM

Quote:

Originally Posted by aerohead

let's see if this works
http://https://ecomodder.com/forum/s...ille-7838.html
Didn't work!
A search for 'lamellar self-blocking grille' located it

Phil, you were soooo close, but too many https://!

https://ecomodder.com/forum/showthre...ille-7838.html

oil pan 4 · 10-06-2022, 05:58 PM

Well if you are running a really hot cam or have the cam timing retarded you get reversion back into the intake manifold, this reversion is what makes hot cams or heavily retarded cam timing make the engine run poorly at lower RPMs. So I would be surprised if adding a reed valve didn't work as advertised.
To be able to take advantage of a hot cam or retarded cam timing the engine has to be spinning faster than about 3,000rpm. Just having hydraulic lifters can tame the reversion on mid range cam grinds that have poor idle quality.

freebeard · 10-06-2022, 07:13 PM

Wrong thread? But I do appreciate the effort.

So the grille self-throttles when the engine is working hard? What could possibly....

serialk11r · 10-06-2022, 08:40 PM

I imagine there would be a clacking sound at idle which would be really annoying? Don't see why the concept wouldn't work though, it's basically crude VVT. That said I am not sure this is worth the effort, since it mostly improves idle.

My V8 engine has very hot cams (peak power at 7600rpm) and IIRC it'll idle as low as 620rpm (I have it set to 675, that's about where the fuel consumption stops improving from dropping the speed). That said, if the coolant temp is at say 85C instead of 100C the fuel burn is WAY higher (like 25%), so it's clearly sensitive to that exhaust reversion.

cRiPpLe_rOoStEr · 10-08-2022, 04:14 AM

AFAIK some very ancient engines with an IOE valvetrain had a passively-actuated intake valve which was of the conventional poppet layout, pulled open by the vacuum at the intake stroke. But I'm not sure how a reed valve could be so beneficial in a 4-stroke engine which already resorts to mechanically-driven intake valves.

serialk11r · 10-08-2022, 05:36 PM

Quote:

Originally Posted by cRiPpLe_rOoStEr

But I'm not sure how a reed valve could be so beneficial in a 4-stroke engine which already resorts to mechanically-driven intake valves.

It helps when the cams have too much overlap like on a motorcycle and especially at low load. The exhaust blows back into the intake and screws up the air fuel ratios and dilutes the intake air. The reed valve prevents the backflow and ensures a higher % of oxygen for good combustion.