Still wiping oil off the side of your D16 after every run? Still getting through fuel faster than a 16cc engine should?
Good news — the Retrol 16cc Horizontal 4-Stroke Diesel Stationary Engine Model (D16) has finished its third round of development, and testing is done. Gen 3 puts out far less oil at the exhaust port and burns more of what you feed it, so it uses less fuel and stays cleaner on the bench. And if you already own a Gen 1 or Gen 2, you can bring your engine up to the same specification instead of replacing it.
Earlier D16s pushed oil out of the exhaust port — unburnt fuel on its way out. The Gen 3 puts out far less of it. More of the fuel burns where it should, so the engine gets through less of it, and the body stays much cleaner instead of spraying itself with oil.
Starting the Gen 3 engine.
Gen 3 running on the bench.
Three generations of the D16
The D16 has been revised twice since its first release. Knowing which generation you own decides which upgrade path applies to you.
The first release, identifiable by the exhaust smoke stack.
The smoke stack was removed and the exhaust arrangement revised, aimed at reducing fuel consumption — oil was being discharged from the exhaust port on Gen 1. The absence of the smoke stack is the quickest way to tell a Gen 2 from a Gen 1.
The current generation, covered by this page. Five systems were revised and 21 components were redesigned. Testing showed significantly less oil discharged from the exhaust port.
A Gen 1 engine running — the tall smoke stack on the exhaust is the giveaway. Compare it with your own to see which generation you have.
Five core technical updates
The newly reinforced base increases structural rigidity, complemented by an added metal guard plate. This protects the internal moving parts from external debris and enhances overall operational stability.
The piston material and machining tolerances have been re-engineered to manage thermal expansion more effectively. This greatly reduces the risk of cylinder scoring — piston seizure — under sustained running.
The complete injection pump, nozzle and fuel line assembly have undergone a systematic overhaul. This precise fuel management is the primary driver behind the cleaner exhaust and the significant improvement in fuel efficiency.
The internal combustion chamber and porting geometry of the cylinder head have been optimised, delivering better compression sealing, smoother power output and more reliable starting performance.
The entire valve mechanism has been precision-matched. The rocker arms, valves and camshaft now work with tighter timing tolerances, minimising mechanical friction and ensuring smoother operation.
The base, guard and piston changes are part of the engine build. The fuel system, cylinder head and valve train components are the ones supplied as upgrade parts for earlier engines, and they are listed individually below.
Every component that changed
First the two engines side by side, then the same comparison component by component. What a Gen 2 engine uses is on the left, what Gen 3 uses is on the right, with quantities per set.
The two generations compared side by side.
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Hatched panels are components we have not photographed individually. Every component listed here differs between Gen 2 and Gen 3, or is new to Gen 3.
What Gen 3 gives you
Which upgrade parts do you need?
Gen 3 builds on Gen 2, so a Gen 1 engine has to be brought to Gen 2 first. If you bought your D16 from Stirlingkit, we cover that first stage for you — you pay only for the Gen 2 → Gen 3 components, and we add the Gen 1 → Gen 2 parts to your parcel at no charge.
How do I tell which generation I have?
Look at the exhaust. Gen 1 has the smoke stack. Gen 2 does not.
I bought my D16 from Stirlingkit — what do I order?
If you have a Gen 1 engine: order the Gen 2 → Gen 3 components only. That is all you pay for. We add the Gen 1 → Gen 2 parts to the same parcel free of charge — our way of looking after the customers who backed the D16 early, before these revisions existed.
There is nothing extra to add to your cart and nothing to ask for. Our team includes the Gen 1 → Gen 2 parts when your order ships.
If you have a Gen 2 engine: the Gen 2 → Gen 3 components are all you need.
I bought my D16 somewhere else — what do I order?
If you have a Gen 1 engine: you need both stages, so add the Gen 1 → Gen 2 components and the Gen 2 → Gen 3 components to your cart. The Gen 1 → Gen 2 work has to be completed first — the Gen 3 parts are dimensioned for a Gen 2 engine.
If you have a Gen 2 engine: the Gen 2 → Gen 3 components are all you need.
Do the Gen 3 injectors need adjusting before I run the engine?
The injector setting matters — it is what controls how finely the fuel atomises — but you do not have to set it yourself. Every Gen 3 injector is adjusted on our side before it ships, so it arrives ready to fit.
The part itself was redesigned for that job: the body is longer than the Gen 2 one, the fuel passages were reworked, and it now goes through a heat treatment process. Fit it as it comes and leave the setting alone.
Will these parts fit a Retrol G16?
In theory some of them will, and it is possible to work a G16 towards a D16 that way. In practice we do not recommend it. By the time you have bought the parts and done the work, you have spent more than a complete engine costs, and the conversion needs a level of machining and fitting skill that most workbenches are not set up for.
If you want a D16, buying the engine outright is cheaper and far less trouble than converting a G16 into one.
Spare parts
Original replacement components for the D16 are stocked separately:
More stationary engine videos
Our stationary engine playlist, including the D16 test runs and generation comparisons shown above.
Gen 3 is done — and what comes after
Everything on this page is in the engines shipping now. That includes the heat-treated injection nozzles: that work is finished, not planned, and it is part of why the Gen 3 injector holds its atomisation over a long run.
As for what comes next, the part we would most like to improve is the fuel injection pump. Ours is currently a millimetre or two bigger than it needs to be. Bringing that down would make it easier to adjust and easier to live with, and of everything still on our list it is the change we think owners would feel most.
We would rather be straight with you about the timeline than promise something we cannot hit. Taking one or two millimetres out of a pump that has to hold pressure is slow work — realistically one to two years, not one to two months. When it is ready you will see it here, tested, the same way this generation was.
What should we change next?
Three generations in, and the engine is still moving. If you run a D16 and there is something you would do differently — a part that gives you trouble, a job that is harder than it needs to be, a change you would like to see — tell us. You are the ones running these on the bench, and you notice things we do not.
If we act on your suggestion, we will send you a gift from Stirlingkit to say thank you. Leave a comment below, reply under any of our videos, or email us at service@stirlingkit.com — whichever is easiest. Tell us which generation you are running and what you would change.
I like that improvements are being made available to an existing model without having to buy an entire new engine.