Topic: Mike Rieck and Rick Stetson 35/28 K head mods.(ram air too)

[kmb69]

Beautiful!
Mike is THE MAN!

[gschuld]

Beautiful!
Mike is THE MAN!

👍

George

[scottly]

Flow numbers didn't improve that much over the 33.5 intake which indicates the port is limiting flow. The spigot entrance definitely holds flow back....it is too small.

1+ The ID of the spigots on the K heads is only 28.5mm, and the wall thickness is only 2.6mm, so they can't be bored enough to matter.

[PeWe]

Is ram-air-intake a possible way to force more air and fuel mix thru the tiny spigot?

[Tracksnblades1]

Is ram-air-intake a possible way to force more air and fuel mix thru the tiny spigot?

I have a spare 10-71 mooneyham that’ll ram some air through those tiny spigots…😁

[gschuld]

Is ram-air-intake a possible way to force more air and fuel mix thru the tiny spigot?

Interesting question:

N/A it is logistically possible in a land speed application. Packaging is pretty wide open.  Only peak speed where it is most useful is king.  Modern bikes are designed around the ram air systems, with the large air box where the tank is normally(feeding high angle intake tracts) and more direct routing from the front of the bike with ducking built into the fairing.  Our carbs are level with the ground, backwards.  So air would ideally be behind it under the seat(or above as second choice), then you need to efficiently get ram air slowed down(building pressure) and into that chamber through carefully designed twin ducts.  You can see the packaging challenges mount.  Now try this in a bike that is required to (or at-least certainly should be) period correct on the exterior.

Dennis build a system for his land speed bike.  Clearly that wouldn’t work for a road racer.

So the answer is likely, yes, but it depends😉

Granted, a kick of nitrous would do wonders🤣

George

[Tracksnblades1]

Is ram-air-intake a possible way to force more air and fuel mix thru the tiny spigot?

I have a spare 10-71 mooneyham that’ll ram some air through those tiny spigots…😁

On a more serious note.. Bernoulli and his equation has done the math.

1.7wg or .06psig at 60mph….   .17psig @ 100mph…depending on air density and elevation…you know same as blower stuff
😜

[gschuld]

Properly done, ram air works. No doubt.

Practically applying it to a non land speed cb750 would be a major issue though.  I’d just assume debate ram air on a separate thread though.

George

[MRieck]

Properly done, ram air works. No doubt.

Practically applying it to a non land speed cb750 would be a major issue though.  I’d just assume debate ram air on a separate thread though.

George

Just look at the early ZX-11...carb ram air set up. I worked on many of those bikes.

[gschuld]

Mike, OEMs really put in the R&D time and made it work.

Take a look at the ZX11 intake, expansion chambers, ducting to airbox, and the big ass airbox.

That sure is a tall order in practical packaging on even a full fairing road race cr750.

George

[Jerry Rxman Griffin aka MuthaF'er]

Very similar to Dennis' setup in principal.

[Tracksnblades1]

Mike, OEMs really put in the R&D time and made it work.

Take a look at the ZX11 intake, expansion chambers, ducting to airbox, and the big ass airbox.

That sure is a tall order in practical packaging on even a full fairing road race cr750.

George

The US Navy has published several papers of their findings of plenum sizes affects on torque and horsepower.
The test mule was a 2002 Honda CBR 600. The Navy boys model plenums volumes ranging from 2 to 10 time the engines displacement. Taking the Helmholtz Resonance Phenomenon to the next level. It’s another long read.. In a nut shell, big is better and really big is considerably measurably better. Really big maintains the highest ambients pressure even with a restricted inlet….small is better for low rpms torque, but really big is really better for high rpm torque. 

When new technology is really old technology borrowed from old War Emergency Power Research

https://www.researchgate.net/publication/267576458_The_Effects_of_Intake_Plenum_Volume_on_the_Performance_of_a_Small_Naturally_Aspirated_Restricted_Engine

[Don R]

 As far as ram air goes, my rear engine dragster has the tall K&N carbon fiber big mouth scoop. I use a K&N  cone filter inside just to keep the sand and pebbles out since we often race at sandy drag strips. I sealed the pan fairly well and put a pressure sensor inside it. At 177 mph, inside the scoop but not in the filter I measure about .5 psi.
  The legend is, it will be as just fast with the scoop turned backwards due to less wind resistance. Supposedly proven by actual track testing. My scoop mount isn't symmetrical so turning it around didn't work.

[PeWe]

The US Navy has published several papers of their findings of plenum sizes affects on torque and horsepower.

This is like using stock airbox but place it between carbs and head
I could not resist to search. motor tuning + plenum size + intake tract
Here is one, for cars but still interesting http://advancedperformancetuning.blogspot.com/2011/02/intake-manifold.html
Often used in turbo applications.

It would be nice to see the result using that beautiful head. Dyno run.

[gschuld]

Mike, OEMs really put in the R&D time and made it work.

Take a look at the ZX11 intake, expansion chambers, ducting to airbox, and the big ass airbox.

That sure is a tall order in practical packaging on even a full fairing road race cr750.

George

The US Navy has published several papers of their findings of plenum sizes affects on torque and horsepower.
The test mule was a 2002 Honda CBR 600. The Navy boys model plenums volumes ranging from 2 to 10 time the engines displacement. Taking the Helmholtz Resonance Phenomenon to the next level. It’s another long read.. In a nut shell, big is better and really big is considerably measurably better. Really big maintains the highest ambients pressure even with a restricted inlet….small is better for low rpms torque, but really big is really better for high rpm torque. 

When new technology is really old technology borrowed from old War Emergency Power Research

https://www.researchgate.net/publication/267576458_The_Effects_of_Intake_Plenum_Volume_on_the_Performance_of_a_Small_Naturally_Aspirated_Restricted_Engine

The helmoltz resonator plenum is really it’s own thing. Again modern sportbikes tend to use huge volume air boxes to take advantage of this concept.

Introducing ram air challenges things further.  The high speed air must be decelerated in a controlled way, tapering out to a large volume, which essentially converts fast air into low speed higher pressure air, which then is delivered to the large central air box containing the carb velocity stacks.  In the ZX11 case, from two ram plenums(one on each side) to the airbox(which has an air filter incorporated in it FWIW).

But like I said, IF DONE RIGHT, it works.  Doing it right requires getting a lot of details correct, some of which aren’t that intuitive.  But regardless, the packaging of all that stuff is not an easy thing to overcome. 

[MRieck]

What that diagram doesn't show is the tube that pressurizes the carbs. Leave it off and the engine runs like crap once you get going over 30 MPH. Don't ask me how I know that.

[gschuld]

I was skipping that issue entirely.  Equalizing pressure from airbox to carb bowls is huge.  I assume that is what the separate tubes coming from the inlets are for in the diagram/photo.

Proof positive of the pressure differential from standard….

George

[Old Scrambler]

George......Wrong Hose  

The small vent tube from each carb must be extended and sealed into the pressurized airbox to prevent fuel syphoning.

I use a CBR600F3 airbox and filter. I copied the basic design for my C.B.R. after reading a lot of USAF, Formula 1 & NASCAR info. BTW.......square or rectangular tubes will flow more air than round or oval designs of same or larger area.

[gschuld]

Well since we’ve seemed to exhaust the 35/28 head section of this experiment, this seems to be a good place to inject this.  It’s a 25 year old magazine article, from the early days of production bike ram air with carbs.

George

[Old Scrambler]

Good one, George That little hose leading from the front intake to the airbox after the air-filter must be necessary for injectors to properly work.

My take on this is the air-boxes provide sufficient air to ALL of the carbs/fuel-bodies at no less than ambient pressure from 0 to 125+ and contribute incremental added power as the speed increases. The dyno chart in the article fails to replicate actual air-speed which may indicate that even more HP was available to extend the power-curve to red-line.

[gschuld]

I agree.  They were only able to reproduce 30mB on the dyno with forced blower air.  At around 150mph in real life, it should have been a bit above 30mB, and climbing fast beyond that.

Again, no doubt it works.  Average speeds for road racing is in the 65-80mph area depending on the track.  So clearly the bulk of the time on track would see marginal if any improvement.  Only the back half of the straight sections (few of them) would see and potential gains of substance.

Land speed racing is perfectly suited to ram aim as it’s all (and only) about absolute top speed.  And the 140+ mph range certainly can make use of it.  Plus, you have ample opportunity to incorporate it packaging wise.

George

[Tracksnblades1]

Sorry for the crude pencil hand drawing, but everything in the marked area is effective squish. I find it hard to imagine a much larger percentage of bore area covered by squish than this.

George

Blair has published paper on squish/quench. Primarily for two strokes. States effective squish to bore percentage between 30-60%. Primarily he was interested in squish speed @ 20-28m/s. Some have ran squish speeds considerably faster without detonation and flame kernel degradation. High percentage/ tight clearance squish is known to impart high loads on crank pin and rod bearings…Old Smokey used to tighten is up until no carbon could form on the piston or head…😁😜

[mad mike]

Nice job ..... I'm led to believe the modern thoughts on two stroke tuning now require a very narrow squish band as opposed the the much wider one used years ago, .... wondering if this would benefit our   "performance dinosaurs"  ?

[gschuld]

I couldn’t begin to guess on two stroke technology, but tight squish bands are widely accepted as beneficial to a four stroke performance engine.

The factory chamber shapes make good squish at 61-62mm bore all but impossible without significant alterations and/or some sort of 3D piston crown shape.

But 70mm on up bores allows far more options.

George

[grcamna2]

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