90-100 hp from MPI 1.3 - what does it take?

[RedmeX]

isjakar:

1.4 have better crankshaft and reinforced block, so its better to start with. On the other hand, it isnt direct fit into felicia and its better to equip it with felicia 1998+ head. So if you have wrong access to Skoda engines use felicia´s one. In general 1.4 have much bigger strike, so its less likely to rev but adds nice amount of torque.

Best is to order cam and ECU from MotorExcel. They will ship it to u, but i cant serve with price. Write them Only with cam and ecu u get60kw at the flywheel.

About head porting, if you know what to do, do it, but its pretty easy to make it even worse. Maybe save some money.

If you can can get exhaust from Skoda Favorit with carb, use it. U will need only second part of exhaust manifold to add there nut for lambda probe (1. is same as for felicia) and favorit middle part with first silencer. I recommend to replace silencer with pipe or catalyst. Its cheap and work nearly as good 4-2-1. Saved money is good to spend on headworks

As i know mpi is much better than SPI, especially after mods.

Other stuff i meant matching head with exhaust manifold and air intake, skimming head, polishing the valves and other stuff to do. Im not engine specialist, so theres a lot i dont know...

[isjakar]

Thanks for this, the engine is intended for an old Mini to be my sons first car, so I use engine and gearbox together, making the Fabia 1.4 sensible, if I can find it. I can get modern 100 hp engines like Suzuki for free but the Skoda has a charm fitting the Mini that modern engines can't touch. So therefore the search of the most cost-effective mods to get from 68 to 90-100 hp,

Motor Excel list a 65 kw/88 hp kit at about 14.000 CZK, just under GBP 500, consisting of a cam and control unit, if I understand the Czech language site correctly. 94 hp kit is just short of GBP 900. Add to this transport, import duties, manifolds, engine rebuild etc and those 20-27 extra hp for 88-95 total are pretty expensive for this application. Over our budget, to be honest, as a 100+ hp standard Jap engine costs us nothing before it is installed.

If this is some way of getting our goal for less, we would be very happy. If this really is the cost of tuning this good, compact and light engine, we have to accept that and give up.

[waool1988]

Sorry for digging something that old up, but the information her is really great. I am working on turning my 1.4 v8 mpi fabia into a track car. From what I got and please correct me if I am wrong, the fabia has a better crankshaft that revs better and reinforced block. One the other hand, mine has smaller valves, single spring for valves, and poor finish for heads sometimes. I am not sure that I would face the ecu problem or not but I just hope it would be programmable! I would be really thankful for you guys if you help me with some questions.

You talked about camshafts but you did not mention if it would work with the standard springs. Would it?

Do anyone knows how many degrees the valves, exhaust and intake, open and how much there is overlap on the original camshaft?

What about turbocharging?

How much do you think the bottom end would take?

Thanks in advance

[djaychela]

The Fabia 1.4 8v head and the 1.3 Felicia MPi head are the same - valves, springs, everything. You can port it, but the springs are an issue, so changing to an earlier dual-spring head will be an improvement for high revs performance. I have a head from Motor Excel fitted to my car which is good for 140-150 bhp given an appropriate bottom end (which would rev to 8000rpm, being all steel with forged pistons). Larger valves can easily be fitted; the earlier head has 8mm stems making valve choice easier. Some MPi/Fabia heads are very poorly finished and have very small ports.

The Fabia crank is better, and will allow higher revs, but the oil pump drive is the weak spot of the engine design, high RPMs are not good for it (I believe the works teams replaced the worm gear frequently, hence not suffering reliability problems).

I don't have cam figures here, but this post here:

http://s3.zetaboards.com/skodaforum/topic/637722/1/

May help you.

You will want to get a replacement ECU; while it is possible to tune the standard ECU (with the right skills and experience), it's not worth the effort, and would be expensive to make subsequent minor changes; you have to expect to need to tweak a tuned setup over a period of time to get it working 100% and an aftermarket ECU will let you do that easily with a laptop.

Turbocharging is of course possible, but would involve a lot of fabrication.

Bottom end is reasonably strong, but remember that it's a 3 bearing crank, and the centre bearing has a hard life; while I've only got a Felicia bottom end, the middle bearing gets a really hard time, and needs replacing regularly on the rally engines I've had.

[waool1988]

Thanks very much for the reply ... I almost lost hope ... I really appreciate the link you sent; I never thought that guys play with these engines that much.

I was asking about the springs because I know that they are an issue. I over-revved the the engine several times to see how it reacts and you can hear that the valve train is going out of shape. Getting one of the earlier heads or even a performance head is too crazy because I live in Qatar. The shipping is mostly going to cost me more than the head itself. I can't go with anything except the head I have but it is going to face some serious porting! I am looking for 7000 RPM from this engine and not more at all. Taking a push rod engine above that would be too extreme from my point of view. The system includes too much momentum. I will look for ponies through forced induction which would be a safer rout from my prospective.

Please don't get me wrong. I love push rod engines since childhood, but I also respect its limitations.

I will take this to the other side where it seems more suited for my questions.

[hawkeracing]

You won't get 7000rpm from the valve springs.....you will be lucky to get 6000rpm on a regular basis. I broke a spring on an MPI engined car a couple of years ago and I had a rev limit of 6200rpm. A touch of light turbo charging would probably be the easiest route.....you just need to lower the compression enough so you don't blow the engine up. There was a turbo charged Rapid 136 running in Practical Performance Cars £999 challenge a couple of years ago so it is do-able - he wasn't using anything high tech. Ultimately it might just be easier to buy a 16v Fabia though.....

[waool1988]

My quest now is new valve springs. I have seen some solutions but all of them include tampering with the head or the valve caps; I don't believe that I have the skill to do that and there isn't someone I can depend on in this.

About the engine, I am doing this because I have an emotional attachment to it. I lost the car in the picture in an accident some years ago and I recently bought the exact same replica. If it was not for that, I would have bought a civic which would be MUCH EASIER to modify.

I am going to start the car as an NA and work my way up the ladder building my confidence in this and getting to know the car. Thanks for telling me about the valve spring to not be aggressive with it until I change them.

I really thank you for your help and if you have any solution in mind for the valve springs that would be lovely.

Edited 11 August, 2012 by waool1988

[djaychela]

I think the only solution for the valve spring issue with involve at least machining of the head and replacement caps (as well as replacement steel spring seats for the springs to sit on), which is possible but not cheap.

Is the shipping really that expensive? My head was expensive (over £1000) but the shipping from the Czech Republic where it was built was only about £15. If you want a look at the head, have a look here on my blog:

http://www.skodarallyblog.com/?p=1086

There's also a picture of the replacement inlet manifold which they sold me - this is like the MPi inlet, but much bigger (as you can see in the pictures) - for me this was important as the standard inlet is too restrictive, and the 'mini kit' manifold is legal for international competition. Obviously you won't be limited like that and could go for something else such as one that allows individual throttle bodies. Might be worth a look at Motor Excel's site - they offer a lot of options for the engines and really know their stuff; they pushed the boat out for me to get my head ready in time for fitting on Rally GB.

[waool1988]

I shipped some boshes from the UK which weigh nothing for £35! How it is going to be when I ship 15-20kg head from the Czech Republic? I wish to make this as money is not object project, but I can't. I am going to buy a used head and try to shave as much as possible of it. I would take my time doing it and make sure I won't affect its integrity. Correct me if I am wrong, the head you got is just like the old heads you told me about, isn't it? Surely I can see the difference between the fabia's and what you have.

About the valve springs, I would really appreciate if you tell me what you would recommend. You are running 7000RPM yourself. What is the spring constant of the springs you are using? .. My questions aren't nice, isn't it?

I took a look at at Motor Excel's website already. I could not understand anything which is really normal.

About the intake manifold, that is going to take a lot of tuning and it has to fit in a really tight place. I am looking into making something like this:

http://www.jukamotorsport.cz/images/gallery/fabia-s2000/PICT003.JPG

I won't do it out of carbon fibre indeed; I am going to use fibre glass. I am going to increase the pressure in the rail (change the injectors if I need to), get a wide band O2 sensor, let the engine work as a open loop, change the map sensor with another one can read up to 5 bars, get a 60mm or more throttle body, use ram intake to increase the pressure on the manifold, change the airbox with one can hold something much bigger air filter, and massive amount of tuning!

Thanks for helping

[djaychela]

I'm not sure, but I would think that the post of the bushes was expensive - prices can vary massively, and for freight items it's often not as expensive as you think - I shipped a MiniMoog synthesizer in a massive crate I made to Italy for £40, including insurance to £2000, and sending a small packet there would be around £20. I would get a quote, if I were you; there are lots of pitfalls to tuning cylinder heads, even more so when you start with a compromised design such as that of the 8v head with the ports all on one side and the exhausts being such an odd shape.

Valve springs, I'm not sure what rate they are - they were pre-fitted by Motor Excel, and I saw no reason to take them apart. However, Martin did ask me what cam i would be using (lift, etc), so there may be some tuning done on them; he mentioned them needing to be shimmed correctly.

Are you experienced in making items from fibre glass? What kind of design were you thinking of? What inlet lengths?

I wouldn't mess about with the fuel pressure too much - the standard pump will provide enough fuel at 3 bar to work with uprated injectors, and from my testing with the Felicia that's the way to go - when I ran a higher pressure I had some reliability issues which only went when I went back to the standard pressure and changed to higher-flow injectors.

Why do you need a MAP sensor that will go to 5 bar?

I don't think you'll see any significant effect with any kind of ram air setup unless you're travelling at well over 150mph, from what I've read.

[hawkeracing]

Standard Skoda springs from other 136 or 130 type engines will cope with 7000rpm easily - they are a double spring design and very durable. On the subject of postage from CZ I usually find the sellers give a very high figure when you first ask for a price - if queried they then drop the price by at least a third.

[waool1988]

One of the drawback of living in the middle of nowhere from the worlds point of view is that no one ships here. I have sat up a POBox in the US and the UK but this service is quite expensive. Believe me, I would love to get all my stuff from the US and the UK. I have nothing available here! I don't even have performance tires.

I have seen a lot of video about head porting and some of them were by experts. It does not look like a hard thing to do. Moreover, I have a perfectionist nature and I take my time reading and understanding a task so I think everything is going to be all right. By the way, I am still working on the suspension system and I still need 2-3 months working on that. Mostly, serious engine work won't happen until next year.

The intake manifold is a challenge which I want to take. I know failing it is really probable, but I want to do it. I know someone who does have experience with fibre glass which is going to make things easier if god may. Moreover, I have done some calculations which sound good, 30cm runner length, but I would do it all over again when I finish working on the head itself.

I won't raise the pressure on the fuel rail that much. The pressure right now is 2.5 bar which is really low. I will just play with the fuel regulator to increase it to 3 bar. I would like to change the fuel injectors too, but the ecu drives 14.# ohm injectors. This makes it a bit hard to find larger injectors.

Did I say 5bar? Sorry, I meant 10 bar. All I am doing is tricking the ecu as you see from the illustrations. I have read that ecu can’t read above 1 bar, 1atmospheric, from some reason. These things I am going to find out when I start playing with the ecu.

About ram induction, let’s say that we have a very large scoop making air velocity going into it considered relatively zero to the air traveling along the bodywork. Let’s say also that the air traveling along the bodywork is 80% the speed of the car because of friction forces. Taking these two assumptions and putting that into Bernoulli's equation we get this chart.

I would like to say here that this is a really liberal approximation especially at low and high speeds. However, it gives a good image of what would happen.

About the valve springs, I have read two solutions until now and both of them need machining. The first one is the older head dual springs. The second one is 1275 Mini double valve springs. I believe that I need valve springs which are a bit stiffer. How much stiffer is the question.

[waool1988]

Just one thing, the pressure in the chart is absolute pressure not gage pressure. If you want gage pressure just subtract one bar.

[djaychela]

Head porting is a lot harder to do than a lot of people claim. Getting it right is a completely different kettle of fish altogether. You won't achieve optimum with your first head that you do, you will make mistakes in terms of the places in the head that you remove which will then reduce airflow. I take it you have access to a flow bench as well as the tools needed? Have you read much on Guy Croft's site? Extremely informative.

What size scoop did you calculate would produce those figures?

The ECU can't read above 1 bar because it will never see a positive pressure higher than that - it's a N/A engine and the inlet pressure will seldom be above atmospheric anyway, and will only do so if there is an odd event happening in the inlet (I can't even think of one offhand), or a tiny bit above because of atmospheric conditions.

[waool1988]

At the moment, all the tools I have fit into a shoe box! I know it isn't ideal, but it is going to get better in the future. I told you earlier that we don't have performance tires in this country, do you really think that I would have access to a flow bench? Although it is really easy to manufacture when you come to think of it. Anyways, Guy Croft's website became the priority of my readings. Thanks for the tip.

I really stressed that the figure is very liberal representation. According to the first assumption, the scoop is so big that the air velocity going into it to the engine considered zero compared to the air velocity travelling along the car bodywork. I mentioned that is no good at low speeds because the air is not travelling fast enough along the bodywork to satisfy the first assumption. Also, it is no good for very high speeds because Bernoulli's equation fails itself. Bernoulli's equation works for incompressible flows which is not the case for air at high deferential pressures. I will get you some empirical results if god may. That would be a very nice to put them against each others.

About the MAP sensor, do you mean that the ecu ignores it because it is not in the injection timings map itself. If it is the case, it would save me a MAP sensor because the fabia's can read up to 4bars!

[djaychela]

OK, first things first - I think this is a case of enthusiasm over experience. I've been messing about with cars for over 20 years, and have built a few in that time and learnt a fair bit... anyway:

Porting is not simple. It's not just a case of removing a bit of metal here and there and then polishing the ports (indeed, it's not a case of polishing the ports at all!). The more you look into the science of the way the air flows into and out of the engine, the more you realise you don't know. A DIY porting job will be OK for a basic improvement over a standard (series production) head. The reason for this is simple; the machining that is done to heads such as the 8v Skoda is done down to a price, not up to a standard. Therefore it is dead easy to see some limited gains by working in the valve throat area and smoothing it into the port walls; this is where the bad machining step usually is, and some decent gains can be had here. On modern engines then there are far smaller gains to be had as machining has improved in the quest for increased outputs and improved efficiency; if you dismantle a series production engine of the last 5 years and look at the internal design of it and the machining standard, it will be equivalent of a race part of a couple of decades ago; for instance the Ford Sigma engine has a lot of characteristics of a BDA engine - aluminium block, thin-skirted pistons, high-quality porting, etc., etc.

Once you go beyond cleaning up of inadequate machining, you have to have a flowbench if you want to get good results. OR you have to port the cylinders, fit the head, set it up on a rolling road, and then measure power. There are no shortcuts - what you think will improve flow will not, always, and in addition it may even make less power than you started out with. This (as I said above) is even more true when you have an oddball engine such as the 8v Skoda - there aren't many people who tune them, and the setup is unusual; you can't take tips from other people's similar engines because there aren't many.

You will spend more money trying to do it yourself than you would to get a decent head built by someone else - you will need to wreck many heads to find the optimum port shape and size for a given spec of engine. In addition, the tools you need to do a good job (such as a high speed die grinder) are easily broken in the wrong hands; removing metal from a cylinder head takes a combination of force and precision and this is not easily achieved.

On the ram air front, let's see your maths. I think you've made some sizeable errors. As it happens, in a former life I was an instrumentation engineer, so I spent years measuring flow rates etc in large industrial processes (actually in the nuclear industry), so I'm not afraid of a little maths, nor talking formulas, etc. I think your calculations are massively wrong, and don't think you should waste a lot of time chasing up a blind alley, but I'm prepared to be proved wrong, so let's see the maths and see what's what. Why do I say this? Because all practical experience points to it, particularly in the field of motorbikes where I spent a fair bit of time in the past; ram air boxes etc didn't provide gains of even a fraction of the order of magnitude you're talking about on machines doing 160mph; I think it's unlikely to work on a car doing half that.

The MAP: The ECU ignores it because it will never see such figures. It's not uncommon to see people replace MAP sensors with ones with similar output characteristics in the original pressure region but with a higher maximum pressure, but that's when using forced induction. The standard ECU on a Fabia may come with a MAP sensor which could sense higher figures than it will ever see in practice (I have no idea offhand what it uses), but the ECU will not be programmed for such because of the characteristics of the engine - it may be that the signal conditioning in the ECU before the ADC would mean it would be incapable of reading large positive pressures anyway (you'd need to see the diagrams to have an idea about that). If what you say is correct, then that's would indeed save you the cost of replacing it, but I think it's the least of your issues here - as said ages ago, you'll need a programmable ECU if you want to do anything worthwhile anyway.

[waool1988]

You are totally right, it is a case of enthusiasm over experience .. I don't mind breaking and ruining stuff occasional as long as I am learning .. Lets say this would be my first tare down

About the figure, I am very sure of it if the flow was water instead of air. Anyways, I will find a way to send you the EX sheet. It isn't anything fancy believe me.

About the ECU, I just got my COM cable .. Now I can start playing with stuff around and getting to know the cars brain

[djaychela]

You can mail me the sheet to djaychela (at) hotmail (dot) com.

[djaychela]

OK, got the sheet, thought I would reply on here as it's then searchable by the world if someone else wonders what the answer is/was.

It's actually much more complex than the sheet you sent me, which also ignores the outflow (i.e. going into the engine) - that is a considerable volume of air which would flow out of any ram system. Rather than work it out from first principles, I did a bit of searching, and found an interesting post on the subject, which I'll copy and paste here:

Doing the math, assuming no losses:

pressure increase = 1/2 density speed ^2

pressure of air at sea level at 70 F = 14.696 lb / in^2

density of air at sea level at 70 F = .074887 lbmass / ft ^3

1 slug = 32.174 lb sec^2 / ft

1 foot = 12 inches

density of air at sea level at 70 F = .000001346969 slug / in ^3

if speed is feet / sec

pressure increase = 1/2 .000001346969 (slug / in ^3) speed ^2 (ft^2/sec^2)

1 slug = 32.174 lb sec^2 / ft

pressure increase = 1/2 .000001346969 (lb sec^2 / (ft in ^3)) speed ^2 (ft^2/sec^2)

pressure increase = 1/2 .000001346969 (lb / in ^3) speed ^2 (ft)

1 foot = 12 inches

pressure increase = 1/2 .000001346969 12 (lb / in ^2) speed ^2

pressure increase = .00000808181 (lb / in ^2) speed ^2

1 kph = 0.621371192 mph = .9113444 ft / sec

at 100kph, pressure increase = 0.067123 lb / in^2, less than 1/2% increase

To check the math, I compared with an article on ram air:

150mph = 220 ft / sec, and pressure increase = 0.391160 (2.66% increase)

1 psi = 68.948 mb (millibar)

150mph, pressure increase = 26.97 mb

The article to which he's referring is this one (coincidentally which is from a sport bike website, where I know there was lots of "promise" for ram air inlets initially and then someone did the maths - I believe it was the excellent John Robinson in Performance Bikes magazine when I first read about it - and showed that the gains were nowhere what people had thought).

http://www.sportrider.com/tech/146_9910_ram/index.html

As can be seen in the second part of the article, there is a small boost there, but most of those gains don't happen until relatively high speed (over 80mph in most cases), and these are worth a few percent of power gains for a correctly-mapped engine; clearly worthwhile at high speed (and in some cases it took well over 100mph before any gains were seen), but it would take careful design to achieve. Not to say that it's not worth doing at all, but your original maths was miles out - you won't even get 1psi (0.069 bar), let alone the 20+bar (290psi+) you were talking of originally.

For the record (and from your email!), you're not making me angry, i think i come across like that sometimes, but I'm just writing what I think, and don't want you to waste loads of time doing something which won't work - you'll get far more from decent head, inlet and exhaust than you ever would from a ram air system.

[waool1988]

100 mph in a vehicle weighing 1 ton might need 120bhp, to do 120mph you might an engine with 140 bhp

It is really hard for me to believe that someone with his background can say such thing! When it comes to top speed it is all up to aerodynamics, drive-train inefficiencies, wheel bearings, wheels set up, and tires.

http://www.guy-croft.com/viewtopic.php?f=2&t=43&sid=3f96fa1f16596345bfb260963aaa7189

[adurer]

I hope I am not interrupting any ongoing discussion about 1.3MPI engines tuning.

If yes, I will open a new topic.

I don't have in Warsaw people to ask about, so I would need your advice about a similar tuning but for a 1.3 carburettor engine:

What does it take to add only some 10 kW to existing 43 kW power?

Edited 1 September, 2012 by adurer

[djaychela]

If you convert it to MPi, that will be 50kW (on a 136, not a 135 engine). If you removed the cat you may get a bit more, and give you the 53kW you are looking for. There is a thread on here about it, you need all the injection and head, wiring, ECU, fuel pump, immobiliser and the flywheel (as the ECU uses the pattern on it for timing).

100 mph in a vehicle weighing 1 ton might need 120bhp, to do 120mph you might an engine with 140 bhp

It is really hard for me to believe that someone with his background can say such thing! When it comes to top speed it is all up to aerodynamics, drive-train inefficiencies, wheel bearings, wheels set up, and tires.

http://www.guy-croft...fb260963aaa7189

Yes, it is hard to believe. Guy Croft really knows his stuff in terms of engines and flow, etc., but there are other areas he is not good in - he still believes that carbs are superior to mapped injection, which is just crazy. No-one is perfect, and no-one is logical in every sphere!

[Per F]

What size are std valves? 30 exhsust and 34inlet? How big can I fit? Valve seats? Excuse bad english. From Sweden

[Per F]

hello! I really want to know what valve sizes you have in your engines. I building a 136 for my Rapid, MC-carbs, extractor, cam, ported head, hoping for 100hp on flywheel.

[djaychela]

Probably best to speak to Ken on the Skoda Forum - he's been there and done that with most valve sizes!

http://s3.zetaboards.com/skodaforum/topic/644073/1/#new