Audi TT 1.8T - N249 Delete - Should you do it? Should you re-fit yours? The answer may surprise you! 

Thanks!

Can I ask how you rebuilt it did you use aftermarket hose or oem?

@@leegoodwin47 I used brand new valves and connected them with reinforced, silicone vacuum hoses. I bought 3 metres of 4mm hose and 1 meter of 8mm one to make sure I have enough. The hardest part to get (at least for me) were hose tees matching the sizes and shapes of the original ones (there were like 8mm-4mm-8mm or 4-8-4 connections or something like that and at least one reduction from 8mm to 4mm hose). I reused the metal plate that was holding all of those looping valves in front of the engine. Something has to hold all of that and there was nothing wrong with it (it's just a metal plate). The vaccum reservoir was also in good shape. It wasn't leaking and it's easy to check, so I didn't bother looking for new or aftermarket replacements.

Finally. I posted this comment 3 times already and every time it was disappearing. I wish YT at least showed an error or some explanation on why my comments are gone.

More than 10 years without n249 and car works as first days....

Sounds like your n249 did indeed save the engine!

Not a bad shout, ill add it to the list 👍

@@BWSTT I remember asking you about the n249 waiting for the rain to stop before you did my clutch so for me this was great! Remember I had a twirrupping noise that you said might be boost leak? I smoke tested but couldn't find anything, replaced the DV with aftermarket. Tried the three springs and the lightest one (red I think) reduced the twirrup noise massively (although still does it a little) I'm tempted to book a few hours with you and come up to see if you can give it a look over and see any issues that need sorting 👍

Combi gone too 😜

@@mickehoe Have you found out your issue?

Haha nah, you never drive it in anger, youll be dafe

It will throw a code for n249 missing, you can bypass it, or you can put a resistor on

@@BWSTT thanks for the reply man, it does make the head look messy and a clean up would be nice have a new fuel rail and coil packs to go on will do it then thanks

It could well be the actuator, I would test it manually with a pump and see what pressure it moves at

Нет.

Its the map sensor that detects the over boost. Regardless if it did cut fuel, you do not want more air than is wanted forcing its way in

I wouldnt advise bypassing the n75 to use an mbc, if you want more boost get it mapped in properly

@@BWSTT thank you

Well since the ecu controls the boost using those hoses, theres not much you can do, aside from the car shutting off completely. You could put in an mbc, but still, if the hose fails, an increase in load and rpm increases turbo spool, the only way to stop that is with a boost reference to the wastegate, or to dump the boost created, or to not allow any throttle movement.

@@BWSTT how about a blow off valve,it would do the same job but sorts of doing the same job as the one you have just removed. Seems like leave it alone.

Bad thermostat

I can’t see how clutch slip over rev could ever be the same as anything n249 related going wrong

Ok. This guy says his N249 is causing his RPM spikes, not clutch slip. m.ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-WtK1XoxW_1Y.html&pp=ygUMTjI0OSBmYWlsdXJl I don’t know what a bad M249 would cause otherwise. Here is another symptom that makes me not 100% certain I have a slipping clutch. If I set cruise control, and slow down, then resume cruise control it will start to accelerate but then dump all boost through diverter valve more dramatically that I can do my self. It’s very loud. I can also set cruise control then disengage by pressing the clutch, mimicking a slipping clutch, the boost isn’t dumbed nearly as dramatically.🤷‍♂️ I’m going to replace M249 valve and replace vacuum lines and I’ll let you know. Please let me know if I’m crazy and it’s something completely different

@@Thomas-rx9ur if the revs rise without you gaining any momentum, you’ve got clutch slip, it’s impossible for it to not be. The only way an n249 is involved, is if as I said in the video the boost control is at fault causing boost spikes, causing more power than the clutch can handle, causing slip- so a bad n249 that also can’t then prevent the boost spikes would “rectify” that but only like putting a plaster on the situation- the clutch is still at the end of its life, and you’ve still got overboost that needs properly addressing. The much more likely situation though, is that youve just got clutch slip.

As always, thanks for the help.

I tried to make it clear- if the boost reference to the n75 fails, the n75 cannot control the wastegate in any way, at all. At that point the n249 will open the dv to stop overboost. Also, you say they take too much time to work- then n249 valve is controlled before the throttle plate is closed, and the valve is allowing a closer source of vacuum to control the valve, so is measurably quicker to control the valve if the system is working, since theres no delay whilst waiting for throttle to close, and vacuum to be generated in the intake.

@@BWSTT in regard to the time of it, I mean a more instant response to the actual pressure inside the inlet manifold, the DV will sense the exact pressure inside there giving a more accurate and instant feel to the DV, which under harder driving helps with boost on and off, as you've agreed some differences are marginal, and I like marginal differences because when you add them all together it becomes a huge difference :) I do agree though Bryn with regards to it being a fail safe, the way you explained the overboost(on an unhealthy turbo) would potentially be the only real advantage of it.. but again thats on a system that isn't maintained or looked after. With a healthy n75 and all turbo workings, overboost will be instantly (or close to) controlled by the wastegate dictating how much boost to generate, as you put it very clearly. I don't see many n249's on many big power builds still suing n75 etc or without.. and I know of a good youtuber that's posted how to do n249 deletes also ;) As a general driver experience you will have more feels without an n249 as it's a computer operated system controlling the diverter valve. But there could be slight increase in MPG keeping the n249 potentially. It's not a design Audi implicated to help performance that's for sure. And most TT owners would prefer performance I believe over keeping as much economy but that's likely quite split with how the fuel prices are right now. Not taking anything away from the video mate was spot on 👌 keep up the good work. But I'll certainly not be putting my m249 back on,. I prefer the instant boost repsonse and raw feel(minor) over how it used to be with a working n249. I think the more important topic to be at hand is the fact that on a 1.8t, deleting the Pcv valve and removing positive crankcase pressure / ventilation will result in far worse symptoms and failures than deleting the n249 👍 You should do a video for people to see how and why they should be relocating their PCV Valve for A healthy internal system that doesn't build up acid and so on and so forth 👌

Of course I understand if the n75 wastegate fails, the car can overboost and n249 isn't there to help out.. that's as I say the only benefit I see.. but if you are driving your car like myself and always watch boost pressure, temps and 02 live data then things aren't a worry. But I understand for the other guys who don't get too into that stuff, some might want the fail safe as they have no clue about the running of an engine, and that's fine of course Motorsport isn't everyone's cup of tea 😊🏎️

Fancy featuring in a video titled “ mk1 tt specialist takes his first drive in a mk2 ttrs?” Lol

@@BWSTT if i had a TTRS i would definitely be up for that i only have a stage 2 225 bam lol. Maybe 1 day i get my dream car

@@BWSTT One of my work colleagues had a stage 1 TTRS, by god it was fast! Still have my MK1 that we did the steering rack on by the way!