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.

57 minutes ago, D.FYLAKTOS said:

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.

Where I said that? I pointed out quite clearly what's wrong with your post, are you ignoring that on purpose? The point you are trying to make is nowhere to be found in "your" posts.

Or are you trying to say that what you posted isn't whatever AI spat out and an actual informed human wrote and fact-checked that? Because it's wrong anyway.

Also another point, swapping the engine with a different type is illegal in CZ.

Edited 2 hours ago2 hr by Papez

Swapping is illegal in the majority of cases in GR.

Is not my post and only a blind could see it because i write exclusively based in Greek Grammar-Syntax (by the way these are Greek words) ,i do it in purpose and the text isn't.

No logical man will ask AI ''should a take the A medicine or the B from internet for cancer?" or ''should i do heart surgery or leave it as is?" but let my give you a characteristic example: a friend of mine want to install Led bulbs in his 40 years old motorcycle and in forums when asked he read posts from ''i don't know-sigh...first time i hear such a joke-do you really have an old motorcycle and you haven't bought a new as i did? don't do it won't work-ha,ha are you serious?" etc or just nobody replied to him, i suggest him to ask the AI just to get an idea because you can not rely 100% on it in crucial matters.

He did it, the AI not only suggest to him a simple modification to do in the harness, the specific type of bulbs that needed and pay attention do not buy other design and some other things for the voltage regulator rectifier that no one told him about when he asked. The result? He got rid off the halogen bulb, installed Led, saved many W from the whole electrical system, can see better and the other drivers pay more attention to him at night.

All i did what to give a suggestion from what i have found and let me remind you that few years back we had"The other guy" with an attitude:

''do as i told you-What? you ask for further analysis? i know better i am expert your opinion doesn't count-What? you didn't follow my instructions? so i am not talk to you any more-you are now by your own here".

What the gained? He argued with bad manners with 99% of the members,caused nothing more than problems in every topic so now that he is away no one is remember him.

@keywacat after all this fuss (which i had the prediction that will be continued) what's your decision? You will buy a cheaper 40Kw engine and then pay to make it 50Kw or you will go straight to 50Kw.

PS: from my humble experience you need a lot of money lot of money and time in ECU programming-air filter,new air induction-whole exhaust system to get some HP on Felicia.

Gentlemen, to return to the topic, I've not driven a 40kw LX version before, so I don't know how noticeable the difference between it and my 50kw LXi truly is.

Would any of you have that experience?

In that light would swapping an intake from a 50KW motor provide any benefit? I wonder if I can make smaller changes rather than engine swaps / overhaul, which, as has been noted, is illegal here.

To sum up I'm thinking about buying an LX model Felda in a colour I prefer to the flat white my current car is, and part of the consideration is will a 40KW motor be as enjoyable in a light 'city runner' as what I have now?

Edited 1 hour ago1 hr by keywacat
Mistake in terms

That's nice and all, but I simply asked you to not repost AI outputs, because it's factually wrong and low-effirt that does more harm than goodm And since AI takes most of its knowledge from the Internet, it will end up in another model and spread the nonsense further. It's different

I don't have personal experience, but on paper, the difference will be most noticeable beyond 3000RPM. And I know a lot of Felicia drivers just don't do that.

The gearbox would be probably more noticeable during normal driving (going from 3.833 10S to 4.118 14SK adds around 13% of torque to wheels, at the same wheel speed and adds ~500RPM engine speed), especially in the city. Though, to be honest, back in the day, I swapped gearbox in my 50kW Felicia for pre-fl one (136M 10S, around 250RPM less on 5th) and I didn't really notice a difference, but that may be because the 10S gearbox has better spacing between the gears, compared to the newer 14SK type.

@D.FYLAKTOS I simply asked you to not copy&paste chatbot outputs, because it's often factually wrong, always low effort and does more harm than good. It's fundamentally different from using the AI yourself. This provides no way to check the original sources (if there are any) and instead ends up cited as a source for another unfortunate person who tries to ask AI for a similar info. So please. Just. Don't. Do. That.

If you simply stated YOUR opinion it'd be more useful. I agree, with that it's not worth it. A 40kW in good shape is better than a beaten 50kW.

Edited 50 minutes ago50 min by Papez