Hi everyone, I am Alessandro, new member writing from Italy.

I am restoring my Favorit, she hasn't seen the sunlight for about 12 years, since she was closed in a box, and now I want to get her on the road again..... despite finding spares is a really hard challenge!!

Let me say I'm just enthusiast for how many usefull informations I found here, so first of all thank you everyone!

 

My Favorit is a 1993 GLXi Monomotronic with light engine mods (catalyst removed, BMC air filter, intake manifold polished, custom camshaft and ECU remapped) and now I'd like to replace the rotary distributor with the static coil from Felicia MPI, more reliable, less noisy, plus I think it allows a more accurate adjust of the advances over the entire range of revs. I know a better option would be fitting the entire MPI and head, but for what I read here, starting from a low compression 54cv engine would not give significant benefits. Changing the pistons too is not an option (for now).

 

So my first question is, in addition to replace my HV coil and distributor with static coil and close the distributor hole on the engine, what do I need? I imagine that simply unplugging the 3 pin connector from old HV coil and plugging it on the new static coil wll not do the job.......

 

Second question: from all the test I've done I've found out that optimal fuel pressure in the SPI module is about 1.8 bar, but the original pressure regulator, even with the spring fully preloaded, gives at max 1.2 bar. The cheap solution I've found is to choke the fuel return pipe with a metal clamp until the pressure goes up..... it does the job, but I'd like to find a better solution. Any ideas?

 

Thank you so much!

On 28/09/2021 at 10:23, alle2381 said:

more reliable, less noisy, plus I think it allows a more accurate adjust of the advances over the entire range of revs

 

Distributor in SPI doesn't do anything with timing - that's already done by the ECU. The distributor is really just a distributor.

 

MPI module contains two coils - one fires with 1st and 4th cylinder near TDC, other with 2nd and 3rd. Which means that it needs two different signals per engine rotation - SPI ECU doesn't send such signals and its crankshaft sensor only detects 1st cylinder TDC.

 

1.2 bar is right pressure for the system. Choking outlet is not right thing to do - pressure regulator doesn't set absolute pressure, it sets relative pressure against intake air pressure, which is vital for proper fuel regulation. If you want increase amount of fuel, you need to remap the ECU.

 

"I know a better option would be fitting the entire MPI and head, but for what I read here, starting from a low compression 54cv engine would not give significant benefits"

 

You can increase CR by skimming the head. But that's main hurdle in converting to MPI - MPI has knock sensor mounted in the block, but SPI doesn't have mounting point for the sensor.

Edited 30 September, 20214 yr by Papez

Thank you so much for the clarifications! 

 

29 minutes ago, Papez said:

Distributor in SPI doesn't do anything with timing - that's already done by the ECU. Distributor is really just distributor.

I've always thought that timing was just "mechanical", setted by the relative position between camshaft and the distributor contacts. But from what you said, I guess that distributor just sets the order of firing and a "rough" timing, while the fine timing is done by the ECU. Is that right?

 

40 minutes ago, Papez said:

MPI module contains two coils - one fires with 1st and 4th cylinder near TDC, other with 2nd and 3rd. Which means that it needs two different signals per engine rotation - SPI ECU doesn't send such signals and its crankshaft sensor only detects 1st cylinder TDC.

Okay, so I guess the only option would be fitting the entire MPI system, correct?

In your opinion, would this upgrade give significant benefits?

 

46 minutes ago, Papez said:

1.2 bar is right pressure for the system. Choking outlet is not right thing to do - pressure regulator doesn't set absolute pressure, it sets relative pressure against intake air pressure, which is vital for proper fuel regulation. If you want increase amount of fuel, you need to remap the ECU.

Clear, but let me explain better the test I've done.

Connecting a pressure gauge on the inlet injection pipe I find out that 1.2 bar is the max pressure of the fuel. But with an oscilloscope connected to the lambda signal I found out that voltage was too low, meaning a poor combustion (engine at right temperature and 2500 rpm). Choking the outlet until gauge marks 1,8 bar, the lambda signal goes up to optimal value, and the engine runs tangibly better.

Note the ECU was already remapped.

I've always thought that the reason is that at 1,8 bar the injector can provide a better atomization, but maybe I'm wrong.

What's your opionion? Maybe ECU not properly remapped?  

19 hours ago, alle2381 said:

I've always thought that timing was just "mechanical", setted by the relative position between camshaft and the distributor contacts. But from what you said, I guess that distributor just sets the order of firing and a "rough" timing, while the fine timing is done by the ECU. Is that right?

 

It only sets order of firing, all timing is set by the ECU, using position sensor on crankshaft, which is more precise. Distributor had timing function on older carburettor engines, but because of missing timing chain tensioner, it was all over the place once the chain became loose

 

19 hours ago, alle2381 said:

Okay, so I guess the only option would be fitting the entire MPI system, correct?

In your opinion, would this upgrade give significant benefits?

 

Either that or some custom solution which would generate the right signal from SPI ECU signal and some additional sensor.

MPI is definitely better, its knock sensor allows for more precise ignition and higher CR - 40kW variant rated for 91octane fuel has similar CR as 50kW SPI rated for 95 octane fuel.  However, factory variant also have different cam profile to improve low end torque, which is why maximum power remained the same as SPI, but dynamics, emissions and fuel consumption improved.

 

20 hours ago, alle2381 said:

I've always thought that the reason is that at 1,8 bar the injector can provide a better atomization, but maybe I'm wrong.

What's your opionion? Maybe ECU not properly remapped?  

 

Lot of things could be wrong - there could be a vacuum leak, blocked injector or bad map. Have you checked valve clearance?

2 hours ago, Papez said:

 

It only sets order of firing, all timing is set by the ECU, using position sensor on crankshaft, which is more precise. Distributor had timing function on older carburettor engines, but because of missing timing chain tensioner, it was all over the place once the chain became loose

Clear!

 

2 hours ago, Papez said:

MPI is definitely better, its knock sensor allows for more precise ignition and higher CR - 40kW variant rated for 91octane fuel has similar CR as 50kW SPI rated for 95 octane fuel.  However, factory variant also have different cam profile to improve low end torque, which is why maximum power remained the same as SPI, but dynamics, emissions and fuel consumption improved.

My main focus are performance and reliability. For a car that will run max 1000 km per year, emissions and fuel consumption are not so relevant.

Dynamics and low revs torque are a nice goal too, my custom camshaft is optimezed for mid/high revs, and a more precise iginition with knock sensor would sure give benefits at low revs.

However, from what you said just upgrading injection system without highering the CR seems to be a "half work" (better dynamics but not significant improvement on power and torque).

I will think about, thank you!

 

2 hours ago, Papez said:

Lot of things could be wrong - there could be a vacuum leak, blocked injector or bad map. Have you checked valve clearance?

Valves clearance checked, no leaks on the exaust system, and injector seems to be in good shape. That's why I thought about a bad ECU map

Well, why don't you go to an aftermarket programmable ignition altogether, and if fuel consumption is not an issue run 100ron, and advance the timing a lot. 

Lambda sensor should really give a pulse and not a steady signal. At least in theory that is. 

Maybe you could fit an outside fuel pressure regulator if you think that's the problem. But what pressure does the pump deliver. If you really want tuning you should opt for custom exhaust manifold. At least that's my take..

Mpi as Papez said has wasted spark ignition. Which could be done utilizing the oe hall sensor and flywheel. 

Edited 2 October, 20214 yr by Thefeliciahacker

27 minutes ago, Thefeliciahacker said:

Mpi as Papez said has wasted spark ignition. Which could be done utilizing the oe hall sensor and flywheel. 

 

Unfortunately, MPI and SPI have different flywheels - MPI has extra teeth to mark 1st cylinder TDC. SPI doesn't need that... In theory, SPI signal could be similar to MPI, you'd just need something to route it to the right coil

On 02/10/2021 at 20:58, Thefeliciahacker said:

Well, why don't you go to an aftermarket programmable ignition altogether, and if fuel consumption is not an issue run 100ron, and advance the timing a lot. 

I didn't consider that option because I'd like to keep her as a normally usable road car. Being forced to use 100ron could be a problem sometimes because here it's not so common to find.

Plus, in my ingorance😄, in an ignition system that simple where you can basically adjust 2 parameters (timings and quantity of fuel) I don't think an aftermarked ECU could do something more than the original one can't do.

 

On 02/10/2021 at 20:58, Thefeliciahacker said:

Lambda sensor should really give a pulse and not a steady signal. At least in theory that is. 

  Of course, pulsed and sinusoidal-like. Sorry, I didn't specify.

 

On 02/10/2021 at 20:58, Thefeliciahacker said:

Maybe you could fit an outside fuel pressure regulator if you think that's the problem. But what pressure does the pump deliver. If you really want tuning you should opt for custom exhaust manifold. At least that's my take..

I will sure consider an external regulator if a better ECU remap will not do the job.

Full custom exaust is another upgrade I have in mind too (now I have only replaced the catalysator and the final silencer), but always considering to keep her as a road car in therms of noise, emissions, etc.....

 

On 02/10/2021 at 21:31, Papez said:

Unfortunately, MPI and SPI have different flywheels - MPI has extra teeth to mark 1st cylinder TDC. SPI doesn't need that... In theory, SPI signal could be similar to MPI, you'd just need something to route it to the right coil

Okay that's another difference I will consider (plus I think they have different TDC sensor). I always prefear keep OEM-like solutions than custom ones.

 

Thank you Papez and Thefeliciahacker, you gave me valuable information and advices 👍.  The job will take months 'cause I don't have much time to dedicate, but I will update the topic with the results.

Oh, and If I'll have some issues (hope not......) maybe I will ask again 😄

18 hours ago, alle2381 said:

but always considering to keep her as a road car in therms of noise, emissions, etc.....

Proper 4-2-1 headers designed based on your camshaft and rpm target goals is not going to affect emmisions nor noise. You don't need to make noise or pollute if you want to make power. I can custom enginner headers for you liking and go to your fabricator to only figure out routing. All dimensions will be PROPERLY calculated. 

 

18 hours ago, alle2381 said:

ECU remap will not do the job.

Well look pressure is one thing fuel volume is another thing and injector trimming is another. 

If you start running longer and longer injection timings you will reach a point where you are spraying for more time than I.e. The valves are open. In that case you need either more pressure. Or bigger injectors in which case you will be limited by the volume the fuel pump can deliver. 

What I'm asking is what pressure does the pump deliver to see you headroom. 

18 hours ago, alle2381 said:

timings and quantity of fuel

Belive that all crap toooooners, if you give them a naturally aspirated car will only adjust timing and fuel. 

Even so you can make a fair bit more power by advancing especially a low compression engine which will have huge margins if running 100ron.

As for other things you can play with injection advances but I don't think it would yeild any significant results in a single point injection car. 

On 05/10/2021 at 06:46, Thefeliciahacker said:

I can custom enginner headers for you liking and go to your fabricator to only figure out routing. All dimensions will be PROPERLY calculated. 

That would be great, and of course I will pay you for the work. I will sure consider that. The only problem is how to find the distribution diagram of my camshaft..... it was custom built something like 15 years ago by a well known specialist of my zone, and now I don't know how to find all the geometrical details. Is there a reliable way to collect all characteristic data having it in hands...... or even mounted on car (first option would be more easy as now I have it not mouted on car)?

 

On 05/10/2021 at 06:46, Thefeliciahacker said:

If you start running longer and longer injection timings you will reach a point where you are spraying for more time than I.e. The valves are open. In that case you need either more pressure.

That's why I suppose my mechanic finded our that crap solution of clogging the return fuel pipe to increase the pressure in the injector module. But again, it was lot years ago.... I was young, really inexperienced, and I didn't ask too much.

Once all mechanical upgrades will be done I'll contact a good injection systems's specialist that will find the optimal solution.

 

The OEM fuel pump should deliver 5 bar...... but take this data with caution, as this information comes from the same mechanic that clogged the pipe for increasing the pressure.......

 

On 05/10/2021 at 06:46, Thefeliciahacker said:

Even so you can make a fair bit more power by advancing especially a low compression engine which will have huge margins if running 100ron.

As for other things you can play with injection advances but I don't think it would yeild any significant results in a single point injection car.

First of all I need decide the upgrades to do. Basing on your advices, I think the most reasonable options are:

- simply correctly adjust the OEM injection and timings, basing on my existing custom camshaft and fitting new custom exaust and manifolds (no further engine mods)

- fitting MPI ignition and head from a Felicia (plus all of the above)

- changing pistons too to elevate TDC (plus all of the above)

 

After so many years my engine needs to be opened to check his health, basing on what we'll find out I will decide.

8 hours ago, alle2381 said:

Is there a reliable way to collect all characteristic data having it in hands...... or even mounted on car (first option would be more easy as now I have it not mouted on car)?

Well reliable no..., you would be off a few degrees, you can locate tdc and go from there estimating degrees and valve openings, but sadly, it wouldnt be perfect we could get close though. Maybe that specialist has data (like what he would do to this cam today per say). I only want exhaust open BBDC and exhaust close ATDC, efective lift (only if you want very fine tuning which I would not advise since it's a roadcar). Obviously all measurements are at 1mm standard.

8 hours ago, alle2381 said:

The OEM fuel pump should deliver 5 bar...... but take this data with caution, as this information comes from the same mechanic that clogged the pipe for increasing the pressure.......

5bar sounds realistic but quite high, well a returned system should not really be run returnless, the strain that puts on the whole system is way too much PLUS THE REGULATOR cant adjust based on relative intake vaccum, so altitude or what have you (bigger overlap, part throttle application) would cause much more of a hustle to control the fuelling

 

8 hours ago, alle2381 said:

simply correctly adjust the OEM injection and timings, basing on my existing custom camshaft and fitting new custom exaust and manifolds (no further engine mods)

Yes if you decide on custom intake manifold I can also help but the enginnering required grows exponentially, but yes advancing a lot, running a bit richer (may be damaging for the cat) and incresing scavenging at a desired rpm range (headers) would be quite a health upgrade

 

8 hours ago, alle2381 said:

fitting MPI ignition and head from a Felicia

even better althought as papez said timing controll is going to be harder

 

8 hours ago, alle2381 said:

changing pistons too to elevate TDC

I think you mean to increase CR(compression ratio) well yes, high cr factory pistons (witout the indent) will give you 10:1 to go higher you need dome pistons with valve pocket but where to source them... i honestly dont know (dont attempt what some people would suggest of welding a bulb onto your pistons and then machining it you would seriously compromise the piston) maybe cnc would be the answer but at what cost, what R&D like there are way too many parameters to get a custom billet piston correct on the first try, you simply can (it's either going to be an oil burner or very stiff and inneficent) plus I could help but I've never had such a tough project to accomplish, and I'm sure i wouldn't get it right the first time.

Hello Alessandro and welcome!

 

I saw your car and it's truly a fascinating specimen.

 

It's not related to your topic but may I ask you something please?

You have one of my favorite accessory installed. The grille with lights. Is that an aftermarket part or installed on factory for special models? Where are those lights connected? High beams? Fog lights?

20 hours ago, alle2381 said:

The OEM fuel pump should deliver 5 bar...... but take this data with caution, as this information comes from the same mechanic that clogged the pipe for increasing the pressure.......

Yes, I found this info too, it should be the same pump that runs MPI system at 2,5-3bar. But you need constant pressure between fuel system and intake to maintain proportionality between injection time and amount of fuel.

 

20 hours ago, alle2381 said:

changing pistons too to elevate TDC (plus all of the above

 

You don't need different pistons, the head can be skimmed - you need about 0,8mm to get to 9,5 on the 135B engine, if I remember correctly.

 

20 hours ago, alle2381 said:

fitting MPI ignition and head from a Felicia (plus all of the above)

 

Although Felicia head is better choice, I'm not sure if it's good for SPI injection - it lacks water channels for intake heating.

 

2 hours ago, Papez said:

you need about 0,8mm to get to 9,5

but at that point you make this engine an interference one and you also really dont have any option if a head gasket issue appears (the machining tab is if i remember correctly 1mm)

2 hours ago, Thefeliciahacker said:

also really dont have any option if a head gasket issue appears

There are thicker than normal head gaskets. (2mm)

15 hours ago, R_Blue said:

Hello Alessandro and welcome!

 

I saw your car and it's truly a fascinating specimen.

 

It's not related to your topic but may I ask you something please?

You have one of my favorite accessory installed. The grille with lights. Is that an aftermarket part or installed on factory for special models? Where are those lights connected? High beams? Fog lights?

Well, thank you so much!

Front grill with lights is an original Skoda accessory of that time. For what I know it has never been fitted as standard equipment on any model/version. I've found it somthing like 15 years ago on eBay and now I think it's very rare to find.

They work as a second pair of fog lights, they can be turned on once the main lights are turned on too. The switch is located under the main light's one (I've marked it in green).

P.S. Don't look at the mold on the steering wheel 😄 I took that pic after 12 years that the car was locked in a box and never opened. Now she's clean again! 😊

 

20 hours ago, Thefeliciahacker said:

Maybe that specialist has data (like what he would do to this cam today per say)

It makes sense, I will try ask him!

 

20 hours ago, Thefeliciahacker said:

5bar sounds realistic but quite high, well a returned system should not really be run returnless, the strain that puts on the whole system is way too much PLUS THE REGULATOR cant adjust based on relative intake vaccum, so altitude or what have you (bigger overlap, part throttle application) would cause much more of a hustle to control the fuelling

 

8 hours ago, Papez said:

Yes, I found this info too, it should be the same pump that runs MPI system at 2,5-3bar. But you need constant pressure between fuel system and intake to maintain proportionality between injection time and amount of fuel.

I've just found better informations on an original Skoda self-study program sheet of that time. The original pump can provide 1,2 bar / 70 lt per hour. 
I'm surprised that my car can run at 1,8 bar without problems..... but maybe the pump is overloaded and cannot guarantee reliability over time. Now I just remember I had to replace it one time years ago......

I think I will need to find a pump with higher pressure..... not easy, as it needs to have exactly the same dimensions to be fitted inside the fuel delivery module in the gasoline tank.

 

Anyway the system is not returnless, as the return pipe had not completely closed, just clogged with a metallic clamp to achieve the desired pressure.

 

21 hours ago, Thefeliciahacker said:

Yes if you decide on custom intake manifold I can also help but the enginnering required grows exponentially, but yes advancing a lot, running a bit richer (may be damaging for the cat) and incresing scavenging at a desired rpm range (headers) would be quite a health upgrade

No sorry, I meant exaust manifolds. Intake manifolds had already optimized (nothing special, just eliminated the burrs and evident casting roughness)

 

21 hours ago, Thefeliciahacker said:

even better althought as papez said timing controll is going to be harder

I will sure fit the MPI fonic wheel and sensor too, as to generate the missing further TDC signal

 

21 hours ago, Thefeliciahacker said:

i honestly dont know (dont attempt what some people would suggest of welding a bulb onto your pistons and then machining it you would seriously compromise the piston) maybe cnc would be the answer but at what cost, what R&D like there are way too many parameters to get a custom billet piston correct on the first try, you simply can (it's either going to be an oil burner or very stiff and inneficent)

OMG really some people suggests that?? No, I would never do! 😄 And custom pistons sounds like a too "exotical" and expansive mod 🤑

 

8 hours ago, Papez said:

You don't need different pistons, the head can be skimmed - you need about 0,8mm to get to 9,5 on the 135B engine, if I remember correctly.

Yes, although it could be done, I prefear OEM-like solutions. It gives me more "peace of mind" in case of problems.

Plus, I think a kit of four pistons and gaskets should not impact too much the total amount.

 

8 hours ago, Papez said:

Although Felicia head is better choice, I'm not sure if it's good for SPI injection - it lacks water channels for intake heating.

In that case, Felicia head will be together MPI injection, I will not mix my SPI injection with MPI head or pistons 😉

9 minutes ago, alle2381 said:

just clogged with a metallic clamp to achieve the desired pressure

Nah thats not right not the way to go like no...

 

9 minutes ago, alle2381 said:

custom pistons sounds like a too "exotical" and expansive mod 🤑

 

it is and given the engine's combustion chamber topology it would be very hard to get proper flame propagation at the first few degrees ATDC without creating hotspots 

 

9 minutes ago, alle2381 said:

Felicia head will be together MPI injection

have you considered speeduino

Edited 7 October, 20214 yr by Thefeliciahacker

What is speeduino? Something based on Arduino? 

Programmable cheap ecu with a multitude of adjustments and connection options. 

On 07/10/2021 at 18:34, alle2381 said:

I took that pic after 12 years that the car was locked in a box and never opened

Your car's name is Kathy right?

 

So you have a full range speaker system in the front door including a tweeter and with the bass placed so delicately aimed at the lucky passenger's right places to give a massage while listening your favorite songs. 😉

and.....electric front windows?

You let a genie out of a box. Wishing time.

12 hours ago, R_Blue said:

Your car's name is Kathy right?

😅😅 yes exactly! 

 

12 hours ago, R_Blue said:

and.....electric front windows?

Yes, another rare (in italy) original Skoda accessory, but with some additional functions non originally provided. 

 

There are many "not so evident" features I've added. If you like, I can create a more detailed presentation post of her, since we would be a bit off topic here 😉

36 minutes ago, alle2381 said:

There are many "not so evident" features I've added. If you like, I can create a more detailed presentation post of her, since we would be a bit off topic here 😉

I'd love to see more from Kathy. Please do that. 🥰

On 28/09/2021 at 11:23, alle2381 said:

despite finding spares is a really hard challenge!!

You can find some items on Greek e-stores (payment via card), in CZ-Polland e-shops (payment via bank transfer, high shipping rates), in ebay.co.uk-ebay.re-ebay.it etc.

On 15/10/2021 at 17:00, D.FYLAKTOS said:

You can find some items on Greek e-stores (payment via card), in CZ-Polland e-shops (payment via bank transfer, high shipping rates), in ebay.co.uk-ebay.re-ebay.it etc.

I'm actually finding most spares on some Czeck and Ucrain e-shops, tried ebay too but didn't find parts I need. I didn't know about Greek, thank you for the advice!