Weasel Engine

Weasel Engine Water & bio ethanol diesel conversions.

We had an excellent day yesterday at the University of Lincoln, where Theo presented his thesis on the effects of pre-ch...
27/05/2026

We had an excellent day yesterday at the University of Lincoln, where Theo presented his thesis on the effects of pre-chamber port geometry on main chamber combustion. With a few tweaks his CFD predictions closely matched reality. The first graph is the CFD prediction of pressure oscillation and the second is as measured using a Kistler pressure transducer. The green line is a standard spark plug and the yellow is the PJI. Spark timing and AFR were left the same. The vertical line shows peak pressure position on the standard spark plug. Retarding the ignition for PJI would make two differences, the first is that peak pressure position would be realigned and the second is that the initial hit of the PJI would be stronger due to the increase in fill time. The difference in this case is around 7 degrees of crank rotation. One other interesting observation, each CFD compression and power stroke took over 20 hours of processing time, the Kistler probe had significantly less time @ 4k RPM!

This is the basic kit of parts that allows you to convert the Yanmar diesel engine, or its Chinese counterparts, into th...
25/05/2026

This is the basic kit of parts that allows you to convert the Yanmar diesel engine, or its Chinese counterparts, into this clean burning engine. It will run on gasoline or gasoline and ethanol blends all the way to straight ethanol. The RPM/power is controlled by fuel alone, this preserves volumetric efficiency unlike most spark ignited engines. In the picture we have a high output ignition system with automatic dwell control, vacuum fuel pump, fuel vaporiser(a carburettor can also be used, as can fuel injection), machined piston and of course, our Pulse-Jet Ignition pre-chamber assembly. If anyone is interested in building one of these high efficiency engine then please contact me via the website. www.pulse-jetignition.co.uk

This is the cylinder head from the LC 17:1 CR engine. One of the advantages to two strokes and having oil in your fuel,...
14/05/2026

This is the cylinder head from the LC 17:1 CR engine.

One of the advantages to two strokes and having oil in your fuel, is that you can see exactly where the Pulse-Jet is firing.

This was the silly experiment that started Pulse-Jet Ignition over 20 years ago, and is here to please all of those comm...
05/05/2026

This was the silly experiment that started Pulse-Jet Ignition over 20 years ago, and is here to please all of those comments saying that our engines aren’t Pulse-jets!. They are quite correct, however what delivers the ignition is! The first part of the video is in slow motion and reverts to real time at the end.

Theo, under the watchful eye of Prof Ron from the University of Lincoln and myself have been working to hone in on the specifics. Theo has created a 3D CFD (computational fluid dynamics) model to predict flows, temperature and velocities. The predictions generated were then tested against those measured on the test engine. To give you an idea on the detail of this project, each simulation took over 20hrs of computer time to run one compression and ignition cycle!

The paper will be on our website once published, http://www.pulse-jetignition.co.uk To give you an idea, the project showed that at 4k RPM the PJI insert had five peaks in mass flow and velocity on each spark event until it ran the pre and main chamber out of fuel.

29/04/2026

The previous video showed the change in emission profile by going lean on a standard spark ignition engine. This shows what is possible! The engine is 211cc and running with 15 inch/H2O vacuum, the same as the Honda. The difference is 20:1 compression ratio, minimum combustion chamber surface area and Pulse-Jet Ignition, pre-chamber ignition system. The engine is running well beyond Lambda 1.4, with an EGT in the 250c range. The reason for the exhaust extension is to remove any potential influence generated by the proximity of the propeller. The only change we observed with the extension was a slight, 10c or so rise in EGT. Sorry about the jerky video……I will try harder next time!😂

27/04/2026

I realise this isn’t the most exciting video……but it is interesting. This is the emissions of a 200cc Honda GX200 engine which is attached to a generator. There is a load of 2Kw on the generator and the inlet manifold is pulling a 15 inch/H2O vacuum. Watch the emissions profile change as I lean out the mixture. You can see by the bottom line of the display we start at around Lambda 1 and lean out to 1.25 ish. The CO and HC drop, but look at the NOx, that’s diesel levels!

13/04/2026

This week we had a visit from Prof Ron and Theo from the University of Lincoln. They were there to confirm that a CFD model of Pulse-Jet Ignition that Theo has been developing, matched reality……which after a few tweaks….it did!

The video is of what started life as a 3HP direct injection diesel engine. We have removed the injector and modified the piston. We then fitted Pulse-Jet Ignition and a novel Venturi to supply fuel to the inlet port. This is the engine used for the CFD modelling. The result is 20:1 compression and 10HP @ 5k RPM, fuel consumption is reduced and will run efficiently on gasoline or “Strait busting” home brewed ethanol! The PJI combustion system is so resilient to lean burn the engine RPM can be varied by fuel alone….without the hint of a “lean burn sneeze”. During the tests we never ran richer than 1.3 lambda and mostly off our scale which stops reading at 1.4. The exhaust gas temperature remained below 260c at all power levels.

09/04/2026

This is a standard 10:1 air cooled engine running with our new alloy sleeved PJI insert. They will be on the website by the end of the week. One of the reasons that we water-cooled the 17:1 CR engine was that the air cooled engine has only a few turns of thread for the spark plug. This made it hard to keep the PJI insert in its optimal operating temperature range. The cylinder head temperature on these little air cooled engines is high compared to larger air cooled engines. Typical CHT can be as high as 220c.

While the tandem engine is having a number of modifications, we are getting ready to test the 17:1 engine for altitude r...
30/03/2026

While the tandem engine is having a number of modifications, we are getting ready to test the 17:1 engine for altitude resilience. Sorry no prop guard yet, J.P…..but it’s coming…..Notice the quiet exhaust, E.R.S….keeping the neighbours happy!😃…

We wanted to test the difference in manifold pressure with the standard rearward facing inlet and then turned 180 and forward facing…….Forward it is from now on! Inlet pressure went from negative 8 inH2O to positive 4 inH2O, and gained a few hundred RPM…….Still at 1.4 Lambda, an EGT of 300c and it loved it!

21/03/2026

This is our proof of concept tandem engine running with both engines @ 8k RPM on a 26 x 12 propeller. Why tandem? It’s 60% lighter than two engines. The rear cylinder can be completely deactivated and uncoupled by means of a centrifugal sprag clutch. We can compound engine characteristics, the front engine high torque high altitude and the rear engine high RPM sprint. This allows for a high power takeoff and climb to operational altitude, then deactivate the rear engine for a huge increase in range/loitering.

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