Using resistors to replace electrical components. - SEAT Cupra.net

**DPJ** · 13-02-2008, 19:53

Electrics have never been my strong point. I had to do electrical engineering as part of my Uni course but I haven't retained much (and it was a long time ago)!

This is mainly a 1.8T engine question....

Without getting into a discussion on why components can be removed, it's possible to remove N112, N249, Evap and Secondary Air from the engine. The ECU will (sometimes) throw up fault codes unless resistors are fitted across the remaining electrical connector.

Is there a simple way of calculating what size resistor is required? Can someone explain?

I've measured the resistance of the removed components.
N112 28 ohms
N249 22 ohms
Evap canister 24 ohms
Secondary Air Motor 0.8 ohms.

Are there other factors that need to be taken into account?

*PhilW* · 14-02-2008, 12:37

Bump for info.

*UncleFester* · 14-02-2008, 12:54

The only problem i could see Dave is if the resistance is variable. Can you not measure the resistance they provide when they're working as surely that's the action you want to mimic? I would assume the ECU is smart enough to detect their presence and then detect whether they're actually doing anything?

If they're similar to EGR operation, could a decent tuner not simply map them out of operation?

**DPJ** · 14-02-2008, 12:59

Sorry for being thick

..... How does resistance change?

(ie SAI is a motor - hence low resistance - apply a current to it and it rotates)

It's a little bit difficult to catch N249 or N112 in the act of switching - otherwise I ddon't know what voltage to apply to them.

*UncleFester* · 14-02-2008, 13:14

I was thinking out loud - i was guessing that the ECU detects their presence by resistance .... what i don't know is how it measures / records their operation ... maybe i was being thick and they record that by voltage and not resistance which doesn't change.

In which case all you have to do is fool the ECU into thinking they're not there, what i don't know is whether it would check or look for them working after that. You might not get an error after starting but you may get one after something fails to do something the ECU or another component expected it to do?

**DPJ** · 14-02-2008, 13:24

I know that I can get a Secondary air code through the Lambda detecting unexpected a/f. We can't easily avoid this sort of thing - and although it would be nice to get it mapped out, we don't want to ditch Revo etc just to solve this.

What I really want to understand is how you establish what the correct size of resistor is to replace the component. Is it the same as the component's resistance?

*UncleFester* · 14-02-2008, 13:33

/me goes to search google for answers ... i'll pop back if i find something

edit:

Had a scan around and whilst there is lots of info on specfic ECU mods, there appears to be nothing much on replacing general electric components with resistors that match the original resistance.

Neg. · 14-02-2008, 15:08

The ECU is looking for a change in voltage? Therefore as the components resistance alters through change, the voltage is also varying. What you need to know is what the resistance is in the components "normal" state, and apply that sized resistor. It could be that the resistance's youve stated could be in fail mode ie. the ecu thinks that component has failed.
HTH

What voltage goes to these components as you also need to know the current being handled. This is calculated via the ohms law equation which states

Voltage = Current * Resistance

Or in your case

Current = Voltage/Resistance

**DPJ** · 14-02-2008, 15:20

Cheers, Neg.

The thing is, these things aren't sensors. As far as I'm aware, N112, N249 and Evap Canister top are all electrically controlled valves (air switches) and the Sec air is an electic motor.

So surely if the substitute resistors have the same resistance as the components, the ECU will think it IS the component that's operating......

Feel free to say I'm talking sh1t....

ibizacupra · 14-02-2008, 15:41

in the case of the solenoids they are inductive-resistive devices... so adding a resistor is not an exact swap...
the resistance will change with frequency.. (inductance etc)

Simply adding a resistive load to mimic a coil is not the same, particularly when its a solenoid which is having a frequency applied to it to switch it.. (not on-off like a switch, but switching.... bzzzzzzzz)

A resistor is a fixed load a solenoid coil is not.

**DPJ** · 14-02-2008, 15:48

Quote:

Originally Posted by ibizacupra

in the case of the solenoids they are inductive-resistive devices... so adding a resistor is not an exact swap...
the resistance will change with frequency.. (inductance etc)

Simply adding a resistive load to mimic a coil is not the same, particularly when its a solenoid which is having a frequency applied to it to switch it.. (not on-off like a switch, but switching.... bzzzzzzzz)

A resistor is a fixed load a solenoid coil is not.

Ahhhh, I see.

Cheers Bill!

*Myki da Pyki* · 16-02-2008, 20:34

By the sounds of it the verdic is dont touch it in the first place!! Dammit lol

*cuprabaz* · 21-03-2008, 20:47

A bit off topic here, sorry lads.

Bill or anyone else that has removed their EVAP, have any of you had over fueling issues?

**DPJ** · 21-03-2008, 20:50

Quote:

Originally Posted by cuprabaz

A bit off topic here, sorry lads.

Bill or anyone else that has removed their EVAP, have any of you had over fueling issues?

None for me. My fuelling is really good. I've thrown an evap code a couple of times, but I can't see how evap affects fuelling

*cuprabaz* · 21-03-2008, 20:56

Bigboost ask the question on my emissions thread, and i wasn't sure so i ask on this thread. Here's my thread http://www.seatcupra.net/forums/show...2&postcount=34

13-02-2008, 19:53	#1
DPJ ........... Join Date: Dec 2004 Location: NN Yorks / Salento Posts: 11,756	Using resistors to replace electrical components. Electrics have never been my strong point. I had to do electrical engineering as part of my Uni course but I haven't retained much (and it was a long time ago)! This is mainly a 1.8T engine question.... Without getting into a discussion on why components can be removed, it's possible to remove N112, N249, Evap and Secondary Air from the engine. The ECU will (sometimes) throw up fault codes unless resistors are fitted across the remaining electrical connector. Is there a simple way of calculating what size resistor is required? Can someone explain? I've measured the resistance of the removed components. N112 28 ohms N249 22 ohms Evap canister 24 ohms Secondary Air Motor 0.8 ohms. Are there other factors that need to be taken into account? __________________ Dave ...................... dpj@seatcupra.net ...............................................................................Alhambra Stylance 140Tdi...KiwiCupra 8v...387.7bhp Leon Cupra GT

14-02-2008, 12:37	#2
PhilW 3071 Join Date: Nov 2004 Location: South Wales Posts: 10,120	Bump for info. __________________ Project Thread

14-02-2008, 12:59	#4
DPJ ........... Join Date: Dec 2004 Location: NN Yorks / Salento Posts: 11,756	Sorry for being thick ..... How does resistance change? (ie SAI is a motor - hence low resistance - apply a current to it and it rotates) It's a little bit difficult to catch N249 or N112 in the act of switching - otherwise I ddon't know what voltage to apply to them. __________________ Dave ...................... dpj@seatcupra.net ...............................................................................Alhambra Stylance 140Tdi...KiwiCupra 8v...387.7bhp Leon Cupra GT

14-02-2008, 13:24	#6
DPJ ........... Join Date: Dec 2004 Location: NN Yorks / Salento Posts: 11,756	I know that I can get a Secondary air code through the Lambda detecting unexpected a/f. We can't easily avoid this sort of thing - and although it would be nice to get it mapped out, we don't want to ditch Revo etc just to solve this. What I really want to understand is how you establish what the correct size of resistor is to replace the component. Is it the same as the component's resistance? __________________ Dave ...................... dpj@seatcupra.net ...............................................................................Alhambra Stylance 140Tdi...KiwiCupra 8v...387.7bhp Leon Cupra GT

14-02-2008, 13:33	#7
UncleFester Grumpier by the day! Join Date: Apr 2006 Location: Milton Keynes Posts: 5,100	/me goes to search google for answers ... i'll pop back if i find something edit: Had a scan around and whilst there is lots of info on specfic ECU mods, there appears to be nothing much on replacing general electric components with resistors that match the original resistance. Last edited by UncleFester; 14-02-2008 at 14:00.

14-02-2008, 12:54	#3
UncleFester Grumpier by the day! Join Date: Apr 2006 Location: Milton Keynes Posts: 5,100	The only problem i could see Dave is if the resistance is variable. Can you not measure the resistance they provide when they're working as surely that's the action you want to mimic? I would assume the ECU is smart enough to detect their presence and then detect whether they're actually doing anything? If they're similar to EGR operation, could a decent tuner not simply map them out of operation?

14-02-2008, 13:14	#5
UncleFester Grumpier by the day! Join Date: Apr 2006 Location: Milton Keynes Posts: 5,100	I was thinking out loud - i was guessing that the ECU detects their presence by resistance .... what i don't know is how it measures / records their operation ... maybe i was being thick and they record that by voltage and not resistance which doesn't change. In which case all you have to do is fool the ECU into thinking they're not there, what i don't know is whether it would check or look for them working after that. You might not get an error after starting but you may get one after something fails to do something the ECU or another component expected it to do?

14-02-2008, 15:08	#8
Neg. Full Member Join Date: May 2007 Location: Bristol Posts: 177	The ECU is looking for a change in voltage? Therefore as the components resistance alters through change, the voltage is also varying. What you need to know is what the resistance is in the components "normal" state, and apply that sized resistor. It could be that the resistance's youve stated could be in fail mode ie. the ecu thinks that component has failed. HTH What voltage goes to these components as you also need to know the current being handled. This is calculated via the ohms law equation which states Voltage = Current * Resistance Or in your case Current = Voltage/Resistance Last edited by Neg.; 14-02-2008 at 15:11. Reason: addional info

14-02-2008, 15:20	#9
DPJ ........... Join Date: Dec 2004 Location: NN Yorks / Salento Posts: 11,756	Cheers, Neg. The thing is, these things aren't sensors. As far as I'm aware, N112, N249 and Evap Canister top are all electrically controlled valves (air switches) and the Sec air is an electic motor. So surely if the substitute resistors have the same resistance as the components, the ECU will think it IS the component that's operating...... Feel free to say I'm talking sh1t.... __________________ Dave ...................... dpj@seatcupra.net ...............................................................................Alhambra Stylance 140Tdi...KiwiCupra 8v...387.7bhp Leon Cupra GT

14-02-2008, 15:41	#10
ibizacupra Jack-RIP my little Friend Join Date: Jul 2001 Location: glos.uk Posts: 30,307	in the case of the solenoids they are inductive-resistive devices... so adding a resistor is not an exact swap... the resistance will change with frequency.. (inductance etc) Simply adding a resistive load to mimic a coil is not the same, particularly when its a solenoid which is having a frequency applied to it to switch it.. (not on-off like a switch, but switching.... bzzzzzzzz) A resistor is a fixed load a solenoid coil is not. __________________ BADGER 5 LTD: PERFORMANCE TUNING RACE PROVEN PRODUCTS & HONEST ADVICE: Contact:07976 800775, 01453 822880 Bespoke Big Turbo conversions,AEM WMI,Forge,Ferodo,AP Racing Brakes,Custom Mapping,REVO,H&R,Eibach,KW,Koni,Milltek,Jetex,Vibratechnik,Compomotive,DTA,Jenvey,Brembo brake kits,EBC,Koni,Neuspeed, and much much more... http://www.badger-5.com email me at:bill@badger5.co.uk

16-02-2008, 20:34	#12
Myki da Pyki Senior Member Join Date: Jul 2007 Location: Bristol Posts: 3,387	By the sounds of it the verdic is dont touch it in the first place!! Dammit lol

21-03-2008, 20:47	#13
cuprabaz HUD'ER CHAPPIN!!!!! Join Date: Jun 2004 Location: Aberdeenshire Posts: 2,214	A bit off topic here, sorry lads. Bill or anyone else that has removed their EVAP, have any of you had over fueling issues? __________________ BlackwidowTurbos DMC Performance

21-03-2008, 20:56	#15
cuprabaz HUD'ER CHAPPIN!!!!! Join Date: Jun 2004 Location: Aberdeenshire Posts: 2,214	Bigboost ask the question on my emissions thread, and i wasn't sure so i ask on this thread. Here's my thread http://www.seatcupra.net/forums/show...2&postcount=34 __________________ BlackwidowTurbos DMC Performance

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