Hi,

 

I created this topic to solve issues i have with my 1996 Felly (135Mpi).

Here in France it's not easy to find parts (even with family working for Skoda ). I order most parts from Czech Republic.

From what i've read here it's a good start to change camshaft in order to have a small increase in performance.

After almost 6months, i decided to change the stock camshaft with one from Engitec.cz (278°/270°). I was already running a 4-2-1 stainless exhaust with a cold air intake (Dynamic admission) and using stock Siemens ECU.

Now the car idle strangely and acceleration are not as smooth as stock camshaft.

 

Any ideas ?

 

 

What's already done:

Changing timing chain

Ajusted the valve clearance (thanks RicardoM for the guide)

New spark plugs

Oil change

 

Thanks

 

Edited 10 May, 20188 yr by lulu14150

4 hours ago, lulu14150 said:

Now the car idle strangely and acceleration are not as smooth as stock camshaft.

Define "strangely". You see and hear the engine. We don't.

4 hours ago, RicardoM said:

Define "strangely". You see and hear the engine. We don't.

Sorry

Idle isn't stable (can even stall) and acceleration are not smooth. After ajusting the valve clearance it's better but not as good as using stock camshaft.

+ Engine produce more vibrations when idleing

My first thought is that you're pairing a stock ECU with a non-stock camshaft. The timing will be affected.

Maybe it would be easier to install a double carburator. So that you don't need to change the programme of the ecu or changing the ecu.

24 minutes ago, nimbus said:

Maybe it would be easier to install a double carburator. So that you don't need to change the programme of the ecu or changing the ecu.

 

33 minutes ago, RicardoM said:

My first thought is that you're pairing a stock ECU with a non-stock camshaft. The timing will be affected.

First thank you for the help you provide.

I've read somewhere that there are different revision of the same Simos ECU 40kw, does it tell you something ?

I've based my modifications from what i've seen here (Favorit Fan post, because i've alsmost the same engine configuration and using standard ECU too):

https://www.briskoda.net/forums/topic/292003-kermit-perhaps-highest-bhp-8v-1289cc-favorit-in-uk/?page=4

Maybe is there a way to remap the Simos ECU, with skills ? Or remplacing it ? (i'm not an expert in ECU...)

 

@lulu14150 @RicardoM - Well, given that Lulu has provided us with the duration, but not the lift, of the new cam, my first thought was that this is a longer duration and maybe higher lift cam, with a stock ECU (Yes Ricardo?). That by itself (without the other mods) would be enough to cause a lumpy idle.

 

Now, reverting the fuelling to carburetor(s) might or might not stabilise the idle, but will almost certainly cause issues with annual emissions testing if that's a thing in France.

 

I think the stock Simos ECU can't be remapped either, so we need to look at a remappable interceptor ECU (reads the outputs from the Simos and trims them by adding or subtracting from the fuel and or ignition timing signals), or replacing the Simos with an Emerald or Megasquirt ECU. At which point I recommend looking up Emerald's website because you need in-depth knowledge of using an Emerald ECU on a tuned Skoda engine.

23 minutes ago, KenONeill said:

but will almost certainly cause issues with annual emissions testing if that's a thing in France.

 

Only emissions test during the MOT in France

2 hours ago, KenONeill said:

@lulu14150 @RicardoM - Well, given that Lulu has provided us with the duration, but not the lift, of the new cam, my first thought was that this is a longer duration and maybe higher lift cam, with a stock ECU (Yes Ricardo?). That by itself (without the other mods) would be enough to cause a lumpy idle.

 

Now, reverting the fuelling to carburetor(s) might or might not stabilise the idle, but will almost certainly cause issues with annual emissions testing if that's a thing in France.

 

I think the stock Simos ECU can't be remapped either, so we need to look at a remappable interceptor ECU (reads the outputs from the Simos and trims them by adding or subtracting from the fuel and or ignition timing signals), or replacing the Simos with an Emerald or Megasquirt ECU. At which point I recommend looking up Emerald's website because you need in-depth knowledge of using an Emerald ECU on a tuned Skoda engine.

ECU is quite restrictive on this car, and changing for an aftermarket one seems hard to me

One post suggest that "the only way to remap those siemens simos ecu's is to desolder the eeprom from the circuit board and solder in a new one":

https://www.briskoda.net/forums/topic/131802-spi-mpi-conversion/

Don't know if it's doable. Here another member is using this camshaft with standard ECU and it seems to work well (15 August post).

Still searching for the easiest way to use this new camshaft correctly.

Edited 11 May, 20188 yr by lulu14150

Well... a much better choice would have been to replace the 135M engine with a 136M engine.

That would have get 14 extra HP and extra 7 Nm of torque.

4 hours ago, lulu14150 said:

I've based my modifications from what i've seen here (Favorit Fan post, because i've alsmost the same engine configuration and using standard ECU too):

https://www.briskoda.net/forums/topic/292003-kermit-perhaps-highest-bhp-8v-1289cc-favorit-in-uk/?page=4

Lulu, that is a highly modified beast.

Just now, RicardoM said:

Lulu, that is a highly modified beast.

Not talking about this fantastic beast, just the post from Favorit Fan (with a green Felicia photo) who have almost the same engine configuration.

Edited 11 May, 20188 yr by lulu14150

@lulu14150 - Favorit Fan also says that their car has a custom tuned exhaust. This can move the peak power and torque up or down the rev range, but won't change the idle behaviour.

 

Ricardo and I are trying to help you, and sometimes the best way to help is to say "you've done this wrong and that's why it won't work".

1 hour ago, KenONeill said:

@lulu14150 - Favorit Fan also says that their car has a custom tuned exhaust. This can move the peak power and torque up or down the rev range, but won't change the idle behaviour.

 

Ricardo and I are trying to help you, and sometimes the best way to help is to say "you've done this wrong and that's why it won't work".

I don't know what is it using for his custom exhaust but i've a 4-2-1 stainless manifold and a simplified backbox.

Anyway, it could be interesting to see which Siemens standard ECU he is using (number part or reference). I've heard that Simos 2P exist with different firmware revision, don't know if it can help...

Again thanks for the help

 

Edit: you can find comparaison between standard ECU firmware here

Edited 11 May, 20188 yr by lulu14150

@lulu14150 - Well there again we have known unknowns*. A 4-1 manifold will give different characteristics to a 4-2-1 (presumes one (or 2) exhaust ports per cylinder. Siamesed ports are different again), as will changing the lengths of the 4 primary pipes, 2 2 secondaries on a 40201, and indeed the length of the system from the last collector to the first exhaust box.

 

*This means that we know we don't know everything; none of us know all the pipe lengths in question, and some of us don't actually know any of them.

I believe main issue is ECU not paired to engine. Afaik, engitec doesn't provide ecu to their cam. But motor-excel.cz does.

But since you have 135M engine, I would start with conversion to 136M. Theres not big difference in hw, 135 has lower compression ratio (different pistons) and small difference in camshaft. Increasing CR and sourcing 50kW ecu might be enough to make improvements. Also it's good idea to find 50kW MPI gearbox. It has shorter diff ratio, so it improves dynamics a little. 

 

And one last idea: 50kW  MPI ECU (not sure about 40kW variant) has feature of higher idle for A/C. There's one pin, which triggers it, but I need to find which one

Edited 15 May, 20188 yr by Papez

Since the early 70's I have tuned more than a few cars simply by fitting bigger exhausts and a cam change and the results have been great but on most of those cars tweaking the jets in the carb was also easy plus there was usually the option of fitting a bigger carb from a similar model. No ECU's to bother about. One thing you could guarantee though was a lumpier idle than standard and in some cases it was difficult to get the engine to run smooth lower down the rev band.

 

First time I tuned a modern car with EFI I simply junked all the OEM injection and ignition kit and replaced with an aftermarket ignition ECU and a pair of Webers I had in the shed. Coupled with a bigger exhaust (no CAT) and a pair of cams the power went from 130 bhp to about 170 bhp, quite a result. Idle a bit lumpy and a bit tiresome below 3000 rpm but your granny could have taken it to the shops.

 

Next time (and at the moment the final time) I junked all the OEM injection and ignition kit and replaced it with an aftermarket ignition and injection ECU. I used a pair of Jenvey throttle bodies and a big exhaust (same as before). Lack of time resulted in not getting a pair of cams but the results were brilliant, power up from 130 to 175. Best of all the idle was factory perfect and no running issues at all, pulled like a train from tickover to the red line. Anyone driving it would not have suspected it was not OEM (except for the performance). Not been tempted with the cams, its too nice as it is.

@skidpan Among those "more than a few" tuned cars was a Skoda Felicia or Favorit? If yes, can you provide specific details?

52 minutes ago, RicardoM said:

@skidpan Among those "more than a few" tuned cars was a Skoda Felicia or Favorit? If yes, can you provide specific details?

 

Afraid not, all Fords. But a wise man told me many years ago that tuning engines is exactly the same for all makes. To get more power you need more air, fuel and a spark at the correct time. Obviously many parts are specific to each brand but the principal remains the same. One good example, one tuner was getting particularly impressive results with his engines but would not tell anyone how he did it, if you wanted his engine spec you had to buy one. Eventually the scrutineers stripped one of his race winners and it was found to be totally legal with no obvious special bits. But the fact was discovered some time later, instead of using a cam from one of the regular parts suppliers e.g. Piper, Kent, Holbay, Cosworth, Newman (there are more) he was having his cams specially made form blanks and then ground to a Honda bike profile. The profile kept the duration and lift within the regs but there was magic in the way the valves opened/closed that somehow Honda had mastered better than anyone else.

@skidpan - Were the base circle and open/close ramps free in that class?

8 minutes ago, KenONeill said:

@skidpan - Were the base circle and open/close ramps free in that class?

 

Yup. 440 thou max valve lift (valve gear free so a lower lift cam with high ratio rockers could be used) and 280 degree duration (with the specified clearance set) were the only requirements. Later they specified a certain Kent cam in an effort to level the playing field. As always those with the most cash had the most power. But you were still free to time the cam in to personal tastes, some liked loads of top end, others liked mid range, some varied the timing to suits different circuits.

1 hour ago, skidpan said:

 

Yup. 440 thou max valve lift (valve gear free so a lower lift cam with high ratio rockers could be used) and 280 degree duration (with the specified clearance set) were the only requirements. Later they specified a certain Kent cam in an effort to level the playing field. As always those with the most cash had the most power. But you were still free to time the cam in to personal tastes, some liked loads of top end, others liked mid range, some varied the timing to suits different circuits.

OK cheers. At that rate yes, you could do something "clever" with base circle and ramps to get faster valve opening and closing, which would theoretically give you more power, but possibly at the expense of drivability.

9 hours ago, skidpan said:

Afraid not, all Fords. But a wise man told me many years ago that tuning engines is exactly the same for all makes. To get more power you need more air, fuel and a spark at the correct time.

Well, yeah, in very simple terms. Yet I think just the theory doesn't help the OP. Tuning an engine is a science in itself. We could make this topic 140 pages long with the theory. Problem is the OP has a specific engine. Any specific and realistic advice for a 'backyard DIYer'?

11 hours ago, Papez said:

I believe main issue is ECU not paired to engine. Afaik, engitec doesn't provide ecu to their cam. But motor-excel.cz does.

But since you have 135M engine, I would start with conversion to 136M. Theres not big difference in hw, 135 has lower compression ratio (different pistons) and small difference in camshaft. Increasing CR and sourcing 50kW ecu might be enough to make improvements. Also it's good idea to find 50kW MPI gearbox. It has shorter diff ratio, so it improves dynamics a little. 

 

And one last idea: 50kW  MPI ECU (not sure about 40kW variant) has feature of higher idle for A/C. There's one pin, which triggers it, but I need to find which one

Thanks for advices.

I've sent a mail to motor-excel to know about how they change ecu program, and prices to expect.

I've already tried an unlocked 50kW MPi ECU i have, and it didn't solved anything except that the engine doesn't stall anymore.

Edited 15 May, 20188 yr by lulu14150