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  1. #1
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    Bleed valve on AGU

    Hi guys,

    I know this is quite a common question for AGU owners so I decided to install a bleed valve on my 1999 A3 with an AGU engine.
    Little bit of background, I currently have an aftermarket turbo intake pipe, pod filter and front mount intercooler.

    I have a digital (very accurate) boost gauge wired into the vacuum line going from the inlet manifold to the dump valve (right next to the fuel pressure regulator).

    I was seeing around 9 psi standard and with the bleed valve I am hitting and maintaining 13psi throughout the rev range. It certainly pulls a lot harder and for the money I spent I am very happy. I might push it a little higher in the future but I am very happy for the moment.

    This post is just to prove that you can do it (note AGU's don't have a map sensor which would possibly throw a fault code with a bleed valve installed in other cars).

    Just wondering, is there anything I can do to the actuator itself to increase boost. I have heard that you can tighten it so it doesn't open as much and will spin the turbo faster but I'm not sure how true that is.

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  3. #2
    <tuffty/>'s Avatar
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    Check your fuelling... AGU's are narrow band and have the potential to run lean as it can't see what the AFR is doing... it will compensate to a degree based on load but its still blind to stuff... when mapped properly you normally have to alter the fuelling tables to compensate for the increased boost/airflow...

    Personally I think this approach is a little bit reckless and could not recommend it to anyone without dyno verification (or by fitting an AFR gauge) of what is actually going on with fuelling etc...

    Just because you 'can' do it doesn't make it right to do it...

    <tuffty/>
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    <tuffty/>'s Avatar
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    ...and while the AGU doesn't have a MAP sensor it calculates boost from airflow thought the MAF sensor so it does know what boost is... its how these ECU's work... ME3.8 is just a little more tolerant than later ECU's due to being dumb as f***

    K03's are spiky on boost delivery... once peaked its all over so chances are its not been a problem long enough for the ECU to pick up on... I suspect under the right load conditions it will still pick up on the boost deviation

    <tuffty/>
    Silver 2001 AMK S3. Silver alcantara interior... now with added powarrrrrrrr, torques. VAGCOM + KII-USB. >> My build thread...

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    Thanks for the reply tuffy, I will check that. What AFR should I be looking for? And when would you start to worry. I was thinking of fitting an AFR gauge to go with my boost gauge. I currently know nothing about how they measure the level of fuel. Is it something to do with the sensor in the down pipe or am I completely off the ball

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    Also wouldn't it see how much air is going through the MAF and adjust the fuel accordingly?

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    It would yes, but it would maintain a near stock afr, which is typically fairly lean for efficiency, and safe at factory boost levels as not much heat is created.

    Runing those same afr's at higher boost creates much more heat. Typically a remap will alter fuelling tables to be richer at higher boost levels and leaner at lower boost for efficiency.

    13:1 afr is reasonably safe at 6psi, not so much at 13psi! Factory fuelling is typically all in the 0.9x range.

    Whilst an mbc can indeed be used as you say, drive it a little more and I think you'll start to notice things you don't like. Once the novelty of more power wears off you'll notice part throttle response is very poor, fuel economy will suffer even when not driving fast, and you'll get a nasty jerk when coming off part throttle as the car gets confused.

    Around 10-11 psi seems to be the 'sweet spot' for an mbc on an agu. Any more and the part throttle jerk starts to ruin the drive, not to mention the previously mentioned dangers.

    i discovered this years ago. I fitted an mbc and went straight for 18psi. The car flew, but I soon realised the downsides. Backing it down to 10psi saw it driving better again, but the drivability was transformed when I eventually got a proper remap.
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    Thanks for the reply prawn. I didn't know boost affected the AFR you should be running. Is there anyway to increase the fueling, if I brought the full version of vag com for example? I have searched nearly everywhere for a place to custom tune but it seems like I can't get it done over here without installing a new ecu. Also I can't find a generic tune for under $1000. Do you know anywhere that would ship a tune I can plug and play?

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    Also does narrow band / wide band affect what AFR gauge you you can run?

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    Ah I see, you're not in the uk?

    Over here, st1 maps for an agu are about £200.

    If you're running the stock ko3, theres really no point in a custom tune, as the turbo is the limiting factor and no amount of hardware mods will really add much to it.

    Where abouts are you? Do you know your ecu part number?

    Without an actual remap, there's really no way you can increase fuelling sadly.

    Wide / narrowband doesn't really make any difference with regards to gauges, because the gauges use their own standalone sensors, and. It the cars standard sensor. An afr gauge will need a second lambda boss welding into the downpipe.
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    Nah over in Western Australia.
    I am still running the ko3. I don't know my ecu part number, how can I find this out and what's the reason for you asking? All the gauges I were looking at were saying they are wideband, I finally understand now. I thought you bridged the current sensor I didn't realise you needed to weld in a new standalone sensor! What a pain in the ass!

    Do you know of places that would send a tune I can 'install' myself. And is that done through the VAG port?

    With the Rosstech cable and full software version can you tinker with the tuning yourself? (I wouldn't do it myself I have a tuner for my other car who I'm sure would be able to do it but he just doesn't currently have the correct software)

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    Another question for tuffty, is there anything he doesn't know?

  13. #12
    Rick @ Unicorn Motor Dev.'s Avatar
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    AGU's actually run rich with more boost - that is providing your MAF is healthy which is very important.

    Rich of course means less power, and ignition timing around this area of the map is very retarded. As Prawn says, the power delivery isn't very nice either.

    Rick
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    Thanks for the reply Rick. I notice you're from unicorn motor developments. Do you sell generic maps that I could install myself (and ship to australia :P )

    Also I've tried logging with vag com to see if the engine is running lean or rich and I have no idea what block I should be looking at. There are heaps of blocks that have a lambda value and I'm not sure what one is relating to fuel. One of the lambda fluctuates wildly from -10% all the way to +10%.

    Can anyone point me in the right direction?

    Thanks

    A side note, the power delivery for me has been fine, no jerkyness or anything alike that I have notice. But then again I'm only boosting it to 13psi (and it drops off over 4k rpm to around 10psi which I guess is the turbo running out of steam)

  15. #14
    RIP S3dave

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    you cant log lambda under boost where it matters on narrow band

    get yourself a wideband in car gauge if you want to see whats occuring.
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    Thank you for saving me from wasting a heap of time badger5! I feel honored to have a reply from yourself, you seem like royalty on these forums.

    Can I get a gauge that will piggyback off the current sensor I have in the downpipe? For example I see this gauge which does not have a sensor, it just has a bunch of wires.
    Black Face 7 Colour 2" 52mm AIR Fuel Ratio Gauge Meter 4x4 4WD AFR Petrol Diesel | eBay

    Or do I need to weld a new sensor into the downpipe (there must be an easier alternative that isn't too expensive).

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    If you're doing it the pikey method the stock tune shouldn't put you in limp mode till you go over about 160G/S which occurs at about 14psi boost with the Ko3, so its best to leave it set about 12psi to account for cold weather.

    My AGU is running even more pikey than this, I stuck a 7lb extension spring on the actuator and the car runs like a champ at 11psi. Throttle response is way better and the car drives like it was meant for this. I don't recommend it though.

    This is only very temporary, just waiting for spare funds to get my turbine housing machined for a baby hybrid and a proper tune.

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    Quote Originally Posted by Jenno007 View Post
    Thank you for saving me from wasting a heap of time badger5! I feel honored to have a reply from yourself, you seem like royalty on these forums.

    Can I get a gauge that will piggyback off the current sensor I have in the downpipe? For example I see this gauge which does not have a sensor, it just has a bunch of wires.
    Black Face 7 Colour 2" 52mm AIR Fuel Ratio Gauge Meter 4x4 4WD AFR Petrol Diesel | eBay

    Or do I need to weld a new sensor into the downpipe (there must be an easier alternative that isn't too expensive).

    The stock O2 sensor is narrow band and reads upto 1V.
    Widebands usually read 0-5V.

    You need a full wideband controler gauge

    INNOVATE MTX-L AFR Wideband 8 ft. Air/Fuel Ratio Gauge 3844 | eBay

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    so that would involve welding in the new sensor? Or could I replace the existing sensor with the one that comes with the gauge and attach the ecu wires to it?

    You say that narrow band reads to 1volt. What affects the voltage to go up and down, the amount of airflow?


    edit: Sorry if I sound like an idiot this is all very new to me. I have done a few logs on my MAF and I am quite sure that it is accurate and I cleaned it as well just to make sure. Given that it is mentioned above that AGU's run rich when you increase the boost providing the MAF is accurate I am quite relieved that it's unlikely that I am leaning out the engine

    edit2: why don't you recommend your pikey spring mod out of curiosity
    Last edited by Jenno007; 12th May 2014 at 14:52.

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    I don't recommend it because the ECU is trying to open/close the wastegate via the N75 and expects a 5psi spring.
    Having the extension spring on just keeps the wastegate closed until about 10psi and the ECU isn't controlling it.

    The extension spring is usually used by people to hold high boost as a weak/old actuator spring can not hold the boost at 20+ psi all the way to redline.

    The air fuel mixture changes the voltage reading for narrow band and wideband.
    Some wideband controllers can simulate narrow band outputs for stock ECU's so you only need the one sensor but I know some ECU's didn't work so well with this. I am not sure if this was resolved.

    To be honest I wouldn't bother running a wideband, that money could be spent on a stage 1 tune or a Ko3s turbo.
    You can send your ecu off to be flashed/chipped or you can get a tuner to send you an unlocked ECU/immobiliser turned off and just use that ECU.

  21. #20
    RIP S3dave

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    Quote Originally Posted by Jenno007 View Post
    Thank you for saving me from wasting a heap of time badger5! I feel honored to have a reply from yourself, you seem like royalty on these forums.

    Can I get a gauge that will piggyback off the current sensor I have in the downpipe? For example I see this gauge which does not have a sensor, it just has a bunch of wires.
    Black Face 7 Colour 2" 52mm AIR Fuel Ratio Gauge Meter 4x4 4WD AFR Petrol Diesel | eBay

    Or do I need to weld a new sensor into the downpipe (there must be an easier alternative that isn't too expensive).
    no unfortunately your existing lambda is a narrowband one, and is only relevant around lambda 1... either side of this lean or rich its of little use.. The tap on gauges you refer to will just dance about from lean to rich telling you nothing but loking like a disco light.

    For wideband we use an AEM wideband afr gauge, which includes the lambda probe.
    you will find them for sale on egay.. or amazon. eg> AEM Digital Wideband Air / Fuel Gauge PN: 30-4100: Amazon.co.uk: Car & Motorbike

    a lambda boss would need to be welded onto your downpipe close to your existing lambda.. You will then see real time afr's

    Whether this seeing the actual afr is of use to you however and what adjustments you can make yourself is the next question. You will be informed of its actual afr's which for me is never a bad thing. spot issues before they damage your motor for example. eg weak fuel pump etc
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  22. #21
    RIP S3dave

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    Quote Originally Posted by antwan64og View Post
    The extension spring is usually used by people to hold high boost as a weak/old actuator spring can not hold the boost at 20+ psi all the way to redline.
    not that any k03 based turbo has sufficient compressor flow to manage this tho
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  23. #22
    Rick @ Unicorn Motor Dev.'s Avatar
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    As Bill says, having a wideband is nice - but isn't going to allow you to actually adjust anything. Would I have one? Yes, but i realise it's all money. I can do you a generic chip, yes. I have a number of customers in Australia but they are running custom setups and so bought they're own programmers so I could tune to suit their setups. You might want to get a K03S or K04 turbo for example.

    Rick
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  24. #23
    Prawn's Avatar
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    Quote Originally Posted by badger5 View Post
    not that any k03 based turbo has sufficient compressor flow to manage this tho
    bang on.

    In the name of foolish experimenting, I once tried unplugging and blocking the actuator feed all together, to just let the ko3S run wild and see what it could do.

    The result was a very brief 28psi spike, quickly settling to 20psi or so, eventually dropping to 12psi at the redline. No amount of trickery will get it holding much more than that, even with an uprated actuator.

    Sadly Jenno, a remap is the only decent option to get more power with half decent driveability and economy.
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    Thanks for all your replies guys. The purpose of this was, if I could easily and cheaply measure my AFR I would to make sure I'm not damaging the engine. I know I can't make any adjustments as I'm not a tuner apart from lowering the boost.

    Since its a fair bit of effort for this to happen I will leave the AFR gauge for now. I notice when cars are getting dyno tuned they have a prong in the exhaust, is this to measure AFRs? I wouldn't have thought it would be as accurate all the way down the exhaust

    Rick that is exactly what I'm after I'll drop you a pm.

 

 

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