Secondary Air System Removal

[Fastkwak]

Top write up as always Rob ..... you have done it now mate my blanking plate is on order lol !!!!. any faults from the N112 yet ????

[Bowders1]

Rob's not taken that off yet as he states earlier in the thread and on his site:D

I have the blanking plate and resistors sitting and waiting for a good day to have a go.

[Fastkwak]

Yes Bowders i know he hasnt taken the N112 off yet and was wondering if by not doing so it was causing any faults /problems because if not it is something that could maybe be left alone i was thinking !!!

[RobClubley]

No dash light so far after about 3 hours of driving both in traffic and motorway speeds

[Fastkwak]

Fingers crossed then Rob ....... you would think if it was going to throw one up it would be at start up when the fan and all the gubbins would be working !!!!!

PS - Anything showing up on Vag com ????

[RobClubley]

Another diagram showing the parts removed in part 1 (red), part 2 (blue) and the N249 system - as it's somewhat intertwined! (Orange)

I'm not sure if it's worth removing the N112 - there's not much more to it and the pipe to the right is a metal hard line which is fixed to the N249 pipes so that would have to stay.

[Bodge]

I was thinking that maybe I'd un-plumb the N112, but leave it there and wired in. So remove the T-piece into the N249, and just connect that hose directly to the N249. Then remove both hoses going to the N112.

On a side note.....(you may know this already) That Skoda diagram is slightly wrong for our cars. Our breather system and vacuum booster systems are not connected directly. We have an additional line from the turbo intake hose, that connects to the suction spray pump, opposed to the breather hose shown in the diagram. Our breather hose from the big T-piece runs directly to the intake manifold.

[RobClubley]

Guess what?! Engine light on the way home. Same one as before - 16795 - Secondary Air Injection System: Incorrect Flow Detected - but it didn't turn on the light before. have cleared it and we'll see how it goes.

[vrs180]

Guess what?! Engine light on the way home. Same one as before - 16795 - Secondary Air Injection System: Incorrect Flow Detected - but it didn't turn on the light before. have cleared it and we'll see how it goes.

Rob

Might be worth repositioning the resister...most dont like getting hot as it effects the resistance value, hence the heavy duty mounting lugs and cooling fins on the body to help dissipate the heat.

I would try securing it (via the mounting lugs) to the inner wing, somewhere it can get plenty of cool air.

PS. excellent write up

[andyrew]

i dont want to high jack this superb post, with the perfect write up.

but what is the activated charcoal filter for? why does it have a line from the fuel tank?

that is a perfect picture, where did you get that from?

[Bodge]

i dont want to high jack this superb post, with the perfect write up.

but what is the activated charcoal filter for? why does it have a line from the fuel tank?

that is a perfect picture, where did you get that from?

Here you are (official explanation):

The picture is from the Skoda pdf manual.

[andyrew]

Here you are (official explanation):

The picture is from the Skoda pdf manual.

iam sure i have seen some where, i think its vwvortex, that some people have done away with this. as well as the secondary air system! what would you do with the 2 hoses running to and from the charcoal canister then?

[RobClubley]

So far I've just disconnected the N112 like so:

The underneath of the plate which holds the N249 and N112 valves. N249 in the centre, N112 to the right. The top line feeding to the N112 is the one I capped off at the other end where I removed the combi valve.

The resistor

In place - I taped up the connector end and cable-tied the resistor to one of the pipes so it's free to cool.

Again I capped the end of the pipe with a self-tapping screw. Need to get an elbow to replace the T-piece into the N249 and tidy things up.

No further fault codes yet - one cold start and an hour or so's driving so time will tell.

[RobClubley]

Just removed that pesky bracket too - it's rather heavy - worth at least .05 bhp I reckon.

[Bowders1]

Good info Rob, so to recap you are bypassing the N112 by just blocking the existing pipes.

And the N249 is still in place.

[Silver Bullet]

Very professional write up Rob :thumbup:

The pics and diagrams are so useful:thumbup:

Peter

NB: That resistor needs to be bolted to a heatsink or a suitable metal surface using thermal conductive paste if possible.

(I contracted at Motorolo in Stotfold working on engine ecu boxes before the site closed).

We used to bolt the big resistors to the inside walls of the die-cast boxes where possible to prevent overheating and premature

component failure.

Edited 26 October, 2009 by Silver Bullet

[Bowders1]

Very professional write up Rob :thumbup:

The pics and diagrams are so useful:thumbup:

Peter

NB: That resistor needs to be bolted to a heatsink or a suitable metal surface using thermal conductive paste if possible.

(I contracted at Motorolo in Stotfold working on engine ecu boxes before the site closed).

We used to bolt the big resistors to the inside walls of the die-cast boxes where possible to prevent overheating and premature

component failure.

That resistor is wrapped in heatsink? as is its part number description. Why would it need another one. I agree it needs to be air exposed and fixed somewhere that it is safe from being knocked and away from extreme heat.

Am I missing something.

[RobClubley]

Good info Rob, so to recap you are bypassing the N112 by just blocking the existing pipes.

And the N249 is still in place.

Yep - The N112 is disconnected and at the moment I've just blocked the pipe that feeds into the N249. Need to tidy that up but I didn't want to mess with the clips on the N249 pipes as I didn't have anything proper to replace them. Cable ties are always good I suppose

I have a CEL again though :(

EVAP may have been fixed with the resistor, but you cannot fix the N112/SAI simply with it, because not only is the ECU looking for the N112, it also has readiness codes for the pump flow, and will throw a CEL if they are non-existent.

From this thread:

The Car Lounge Forums: DIY: Engine Clean-up Pt. 1 - N249 delete

[Silver Bullet]

That resistor is wrapped in heatsink? as is its part number description. Why would it need another one. I agree it needs to be air exposed and fixed somewhere that it is safe from being knocked and away from extreme heat.

Am I missing something.

You are correct, the body is a heatsink, however depending on a components location, for example if there is no air circulating over the body, or no contact with a larger body or its in a closed space then eventually it will heat up as the generated heat will have no where to go, (conduction / convection), resulting in a possible shortening of the components life.

All I am saying is depending on the wattage of the device and its location any extra cooling is a big plus. (Robs location is prob ok, I dont know).

We used a bolt on software package on Pro-e (cad) and run thermal simulations to identify hot spots where high wattage resistors were vunerable to overheating and needed additional cooling.

The big 5 watt ones I used once on a engine test rig for Volvo trucks used to heat the surrounding metal it was bolted to so much that you couldnt touch it and a small local cooling fan had to be added.

Finally, consider, if a resister body surface area / fins were sufficient to keep it cool in any environment then there wouldnt be a market for add-on heatsink suppliers or manufacturers mounting guidlines.

Hope this has helped

Peter

[Bowders1]

You are correct, the body is a heatsink, however depending on a components location, for example if there is no air circulating over the body, or no contact with a larger body or its in a closed space then eventually it will heat up as the generated heat will have no where to go, (conduction / convection), resulting in a possible shortening of the components life.

All I am saying is depending on the wattage of the device and its location any extra cooling is a big plus. (Robs location is prob ok, I dont know).

We used a bolt on software package on Pro-e (cad) and run thermal simulations to identify hot spots where high wattage resistors were vunerable to overheating and needed additional cooling.

The big 5 watt ones I used once on a engine test rig for Volvo trucks used to heat the surrounding metal it was bolted to so much that you couldnt touch it and a small local cooling fan had to be added.

Finally, consider, if a resister body surface area / fins were sufficient to keep it cool in any environment then there wouldnt be a market for add-on heatsink suppliers or manufacturers mounting guidlines.

Hope this has helped

Peter

Fair point Peter.

[abinpete]

I have the same error code that prompted this mod. If I don't want to make any mods to my Octy vRS Mk 1, what do I need to do to get rid of the fault? Any advice would be much appreciated.

Pete