The Bourke/VBL(modern modified Bourke stlye) engine

[RightWingZionist]

http://bourke-engine.com/


http://www.vlbengine.com/
http://en.wikipedia.org/wiki/Bourke_engine
www.rogerrichard.com

There are videos and supposed tested claims on the first site.
First main problem I see is the reliability and friction losses at high rpm of the Scotch Yoke, but it seems that can be addressed.

Compared to H/F/Boxer engine:

What do you guys think of the tests, claims, and thermodynamics of the Bourke type engines?

[RightWingZionist]

Guess it's not interesting at all. No wonder it's not in use lol

[2.2 Straight six]

you waited 30 minutes, you need some patience. don't expect to get a reply instantly.

if it offered all advantages over a conventional flat (including manifacturing costs) it'd probably be made. obviously it doesn't meet all the criteria it needs.

[KiwiBacon]

What advantages does the pure sinusoid give over a normal rod/crank motion?

500ftlb of torque from 400CI isn't impressive at all by todays standards. Are there any modern application of the concept?

While a slightly lean burn offers advantages with regard to emissions, a very lean burn engine ends up pumping a lot of air to produce the same power. If you can offfset that through eliminating throttling losses completely then you're going to be winning. But otherwise I'm not convinced of radical gains.

[2.2 Straight six]

i'm trying the see the benefit of passing the air/fuel mixture around the bottom of the piston. it may offer cooling, but oil squirters are effective enough. that passage for the fuel/air just seems like more resistance for the piston.

besides, it's 400ci and it makes 200bhp and 500lb/ft. that seems a little underpowered to me. a conventional-style 4-stroke V8 with 400ci could make 500lb/ft and make ~500bhp with it.

i can't see any benefit to that engine design.

[curtis73]

It doesn't hold any mystery for me. Its no different than a normal 2-stroke except that the articulation at the crank comes from the sliding yoke instead of an articulating connecting rod. The benefit should be less rotational mass, but at an extreme cost of friction at the crank yoke.

I've also never seen a 2-stroke that wasn't hurting in the emissions department. Regardless of the fact that this one doesn't mix fuel with oil, the fact remains that without the precision of a cam to time events, you have a tough time tuning the engine for broad RPM ranges. Below peak RPM you dilute the exhaust with tons of HC and above it you quickly starve the engine for flow. The same can be said for 4-strokes, but the cam can provide a much larger powerband with fewer emissions.

And I also agree... 200 hp/500 tq is nothing from a 400-cube engine...especially a 2-stroke. The 2-stroke should be able to trump the 4-stroke per cube, even in a garage prototype.

[curtis73]

Originally Posted by 2.2 Straight six

i'm trying the see the benefit of passing the air/fuel mixture around the bottom of the piston. it may offer cooling, but oil squirters are effective enough. that passage for the fuel/air just seems like more resistance for the piston.

Almost all 2-strokes have to pass the mix below the piston. The power stroke compresses the charge below the piston so that when it uncovers the port there is pressure to force intake charge in. The piston rises, sucks charge in, then as it falls it compresses. The piston uncovers the intake port, and the open exhuast valve combined with high pressure intake charge replaces the exhuast gasses with fresh charge. exhaust dilution and HC emissions usually suffer big time.

[2.2 Straight six]

in that case, i can't really see much in the way of benefits at all.

and being a 2-stroke, it'll probably sound like a supercharged fart anyway.

[534BC]

Here are some claimed benefits of the original bourke design.

High rpm capability due to decreased friction (no rod angles and a tripple slipper bearing and scotch yoke)
No combustion contamination in oil.
Very smooth and balanced.
High power and low emmisions and high mpg due to extremely lean mixture.
Lightweight and easy to service.

The tripple slipper bearing allows far higher rpm and the scotch yoke allows for a long dwell at tdc compared to a regular rotating/reciprocating rod/crankpin engine. The increased dwell (time spent at high pressure) combined with exteme ignition advance and very lean mixtures were to allow the cheap low octane fuel to burn in a different (cycle) running on detonation safely and getting tremendous power from those lean mixtures.

[RightWingZionist]

Originally Posted by 2.2 Straight six

you waited 30 minutes, you need some patience. don't expect to get a reply instantly.

if it offered all advantages over a conventional flat (including manifacturing costs) it'd probably be made. obviously it doesn't meet all the criteria it needs.

Umm.. I submited my post on 03-28-2007, 11:36 PM.
That's not 30 minutes.

Anyways, those numbers are at only 2000 rpm, not bad for 1958.
The engine is supposed to give much more HP per pound and have a higher effieciency.
There was also a video clip of the engine some where running on hydrogen, the exhaust was actually a stream of water and not gas.

# 30 Cubic Inch 2 Cylinder Bourke Cycle Engine.
# Constant RPM Stationary Power Plant.
# Potential Adiabatic Operation @ Specific RPM Range.
# Test Fuel: Low Octane Gasoline, Coleman And 1-K.
# Weight: +/- 38 pounds.
# Aluminum crankcase, cylinder castings and pistons.
# Steel cylinder liners, connecting rods, yoke plates, camshaft, wrist pins, bearings.
# 35 hp or more @5,000 RPM.

One of their claims. You can see clips of the engine itself on one of them sites.

[KiwiBacon]

So what mechanism do they claim gives the high efficiency?

Is it the ability to run higher compression (and expansion) ratios without the associated detonation issues?

Do they have any claimed numbers for BSFC (lb/hp/hr)?

[Moppie]

Originally Posted by RightWingZionist

, not bad for 1958.

I think theres the problem, it ain't 1958 no more Mc'Fly.

[534BC]

Originally Posted by KiwiBacon

So what mechanism do they claim gives the high efficiency?

Is it the ability to run higher compression (and expansion) ratios without the associated detonation issues?

Do they have any claimed numbers for BSFC (lb/hp/hr)?

The claimed fuel ratios were very lean and were stated to produce MORE power while running WITH detonation. Bourke called regular engines "running on the carbon cycle" and his engine "ran on hydrogen cycle"

[KiwiBacon]

Originally Posted by 534BC

The claimed fuel ratios were very lean and were stated to produce MORE power while running WITH detonation. Bourke called regular engines "running on the carbon cycle" and his engine "ran on hydrogen cycle"

Any engine is going to produce more power when run at the detonation limit (provided the ECU doesn't start retarding the timing). But it's not going to last very long doing that.

[534BC]

Think of this engine running way past that point (not running at the limit, but rather over the limit) capitalising on the destructive high forces of detonation and turning it into higher power.

Bourke used a mag on his small engines and instead of retarding spark , he ran (I think up to 90 degrees) even more advance.