I'm looking at a 1997 Skoda Felicia with a 40kw engine, and I'm wondering what I would need to change to get it up to a 50kw engine.

The blocks are the same, no? So maybe I could just swap out the throttle body and air intakes?

Edited Tuesday at 09:302 days by keywacat
Mistake in terms

The below text is not mine but it will help you:

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To upgrade a 1997 Skoda Felicia 1.3 MPI from the 40 kW (54 hp, engine code 135M) version to the 50 kW (68 hp, engine code 136M) version, the engine blocks are fundamentally identical, but the internal pistons and the cylinder head are different.

Because the 40 kW and 50 kW models use the same engine block footprint, you do not need to alter engine mounts or swap the gearbox. However, achieving the extra 10 kW requires addressing the differences between the two factory setups:

1. The Pistons (The Core Difference)

• 40 kW (135M): Features pistons with a deep dish/recess in the center. This lowers the compression ratio to roughly 8.5:1 to accommodate lower-octane fuel.

• 50 kW (136M): Features flat-top pistons. This increases the compression ratio to approximately 9.7:1, which is the primary source of the extra 10 kW.

• What you need to do: To do this properly, you must swap the 40 kW dished pistons for the 50 kW flat-top pistons.

2. The Cylinder Head & Camshaft

• While the cylinder heads look identical externally, the 50 kW (136M) head has a slightly altered combustion chamber volume to work with the flat pistons.

• The camshaft profiling on the 50 kW version is also slightly optimized for better breathing at higher RPMs.

• What you need to do: It is highly recommended to source a complete cylinder head assembly (including the camshaft) from a donor 50 kW (136M) engine rather than mixing 135 parts.

3. Engine Management (ECU)

• Both engines use the Siemens Multi-Point Injection (MPI) system, but the fuel maps and ignition timing parameters are configured differently to match the compression ratios.

• What you need to do: You will need to swap the ECU for a 50 kW version or get your existing ECU remapped to match the new compression profile.

The Reality: Is it worth the teardown?

Tearing down the engine block just to replace pistons and liners for a 10 kW gain is a labor-intensive project. If you want to proceed, you have two primary options:

Complete Engine Swap (Recommended) : Easiest, fastest, and cheapest. A full 50 kW 1.3 MPI drop-in engine is highly affordable. Requires pulling the whole engine unit.

Internal Parts Conversion : Keeps your original engine block/serial number. Requires a full engine teardown, new gaskets, and piston ring installations.

In short I should swap the complete engine from my rustbucket LXi Felda into the LX if I buy it, jo? 😃

Cheers for it, would you know if the exhaust assemblies are different?

''No, the exhaust assemblies are identical between the 40 kW (135M) and 50 kW (136M) versions.

Because both versions share the exact same 1.3L multi-point injection block layout and 8-valve cylinder head shape, they use the same:

• Exhaust manifold

• Front downpipe and catalytic converter

• Middle resonator section

• Rear muffler assembly

The factory 42mm exhaust bore diameter is more than enough to handle the extra 14 hp from the 136M flat-top pistons''.

Thanks again for your rapid, helpful replies. Really gets to the heart of the matter. 👍🏻

@D.FYLAKTOS Please, do not just copy&paste AI nonsense here, it'll just scrub here again and reinforce bad information and will be even more inaccurate. Anyone can ask LLM themselves, no need to do it for them and spread misinformation.

Pistons raise CR from 9.5 to 10. Not that big of a difference and it may be possible to reach through head skimming.

The biggest difference is valve timing and ignition timing. The ECU is tuned for 91RON fuel, so it has milder advance settings. The valves have narrower timing because of the fuel, too.

There may be different head, but not ignition volume, but rather different cross section of inlet ports - though this changed so much throughout the production that I'm not sure if it's difference between the two variants.

Also, one difference not related to the engine - the 40kW has FASTER gearbox - in fact, as tall as the 1.6. 50kW is 250/500RPM faster on 5th gear (pre-facelift/facelift), to increase torque on wheels.

There's another potential issue - around 1997 MY, there was change in camshaft bearing size, which also affected timing chain sprockets. So you'll need to check which variant you have and find correct donor, if you proceed with swap.

13 minutes ago, Papez said:

it'll just scrub here again and reinforce bad information and will be even more inaccurate.

That's good news.

So according to you worht to buy a cheaper 40Kw engine and then pay to make it 50Kw? I not, the ''AI nonsense" not so let's collect different opinions from members for the best result.