hi all, ive seen a few threads regarding the removal of the n249,212 & sai, excuse my ignorance but why are people removing them?

im quite curious to know what benefits there are and what downsides there are removing the above?

an explanation of what these features are and what they do would be greatly appreciated so i can have a better understanding of them, that way i can make my own mind up if i should leave well alone or remove them.

ive seen a couple of how to guides on removal of the sai and to be honest its a little shocking just how many parts are removed and thats just the sai part.

this leaves me thinking surely there will be some sort of negative after effects?

as i say excuse my ignorance, but if anyone can spare the time to explain all or some of it to me id be very gratefull.

thanks

nick

SAI system injects extra air when the engine is cold to make the cat more efficient for the first 60-90 seconds of running

This is to meet cold-start emissions regulations in certain parts of the world.

The N112 is the actuator that controls the SAI pump.

The N249 system allows the ECU to open the diverter valve if it wants to. The DV is a mechanical system that does the same job, and removing it can smooth out the power delivery, as well as tidying up the engine bay and removing a few more air pipes.

The evap system has an activated charcoal filter which takes a feed from the petrol tank and absorbs petrol vapours. When the engine is running the petrol vapours are pumped into the intake.There are two feeds, to the throttle body and the turbo intake. I've removed the feed to the intake.

SAI system injects extra air when the engine is cold to make the cat more efficient for the first 60-90 seconds of running

This is to meet cold-start emissions regulations in certain parts of the world.

The N112 is the actuator that controls the SAI pump.

The N249 system allows the ECU to open the diverter valve if it wants to. The DV is a mechanical system that does the same job, and removing it can smooth out the power delivery, as well as tidying up the engine bay and removing a few more air pipes.

The evap system has an activated charcoal filter which takes a feed from the petrol tank and absorbs petrol vapours. When the engine is running the petrol vapours are pumped into the intake.There are two feeds, to the throttle body and the turbo intake. I've removed the feed to the intake.

thanks for that rob, so the sai and the n112 can certainly be removed with no ill effects then? and did you remove them for any reason other than asthetics and does it bring the ecu light up on the dash once removed?

my car has the annoying spluttering / missing characteristics from cold for the first 10-20 seconds which seems to be linked to the sai from some of the threads ive read, would removing it cure that problem then?

the n249 system sounds a little more important? is there any risk of engine damage by removing this? and again does this bring up the fault code light on the dash?

thanks again for your time in explaining it to me rob.

regards

nick

Edited 4 April, 201016 yr by nick_vrs

I removed the SAI because the rivets on my pump were failing and it had started to leak. Removing the SAI turns on the check engine light and the only way I know of to get rid is to get it removed from the map by a tuning company (Shark Performance did mine).

Why not try unplugging the SAI pump to see if it resolves your issue? You might be able to reach it from above. If no you'll need to get the car jacked up, remove the undertrak (4 or 5 torx screws) and you will be able to reach it.

http://www.pimpmyskoda.co.uk/V2Images/ModsEngine/AirSystemRemoval.htm

The N249 doesn't bring up a fault on the dash as long as you replace it with a resistor.

Here's a good explanation: Clicky

N249 is controlling the DV (Dump Valve). It is installed between the intake vacuum source and DV itself. When no current is switched to the N249 (default state), the DV will get vacuum or boost from the intake manifold. This is how almost ALL turbo cars are working. When shifting gears, you let off throttle, TB closes and vacuum is generated which can open DV to vent boost (which cannot enter engine, because TB is closed).

On never 1.8Ts (2000+) they introduced the N249 (along with lots of other stuff) which is a possibility for the ECU to open the DV any time (!), even during full throttle/acceleration. When the engine is running and turbo is boosting, there is no vacuum generated, but to open the DV (which is mechanical), vacuum is needed. This is what the black vacuum reservoir on top of the engine is used for. When idling, shifting, etc - so when vacuum is available, vacuum is led into this reservoir from the intake manifold and kept inside using a check valve (white/black), so when boosting again, vacuum will stay there (air cannot enter into the reservoir).

When ECU wants to open DV during full throttle/acceleration, simply "energizes" N249, which will "de-select" the DV from the intake manifold (boost), and "switches" it onto the vacuum reservoir. The vacuum in the reservoir will open the DV instantly and release your boost, which, in most of the cases (tuning, etc) is not that highly required . In the case ECU sees a little overboost problem, it can turn N249 on/off repeatedly for very fast (just as N75 is working), which will open/close DV all the time, trying to settle (lower) the boost level.

PROs: By removing N249 valve, you can prevent this bad habit of the ECU, and by removing N249 valve, you are removing an approximately 2mm narrow bottle neck restriction (ID of the N249 valve) in the line to the DV, which will result in a somewhat faster DV response. I am using the stock bosch DV, but it feels just as good as an aftermarket DV with N249 (restriction) inline. Boost curve is smooth and progressive.

CONs: Boost overshots/spikes may grow higher, especially in high gear/low rpm situations (using the small K03), which can result in a leaner condition (for the moment). These spikes depend on N75 type, wastegate setting and software programming, but they usually don't last long (0.5-1s max). In the case these spikes are very high (car enters limp even), minor adjustment on the wastegate can be done. Ibiza engine covers cannot be used anymore (by removing the accessories above, two mounting points of the cover are removed aswell).