N75 replacement

samblake92

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Oct 4, 2014
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Couldnt find a write up on here on how to replace / change the n75 valve on a mk1 leon so thought id knock one up :)

Not able to upload pics for some reason but when it allows me to i will.

First of all ive got a mk1 leon cupra 20vt engine mods are full custom built exhaust from turbo back built by prospeed exhausts in cardiff ( cracking company btw ), pipercross panel filter ( upgrading to sports cone soon along with direnza fmic ) dump valve, stage 1 mapped by performance engineering cardiff and bypassed the n249 valve aswell.

Anyways down to business first of all engine covers need to be removed and n75 located and next to the dump valve is a small unit with 1 electrical clip and 3 hoses attached to it.

Remove the silver locking clip from the connecter and keep safe and unclip the electrical sensor.

Pull the hoses off but you MUST remember wich hose goes on which extension from the valve as there are 3 and you dont want to get them mixed up.
The long piece of the new valve goes into the big air pipe running off the filter
The other two must be put in the right way around best to colour code or mark then up somehow i just used a marker and wrote s and m on for small extension and medium extension of the valve.

At this point its a good idea to have a few jubilee clips to hand or cable ties to secure pipes onto new valves preferably jubilee clips for a stronger hold.

Putting the correct hoses on the correct extensions put it all back together and tighten all jubilee clips and replace the locking clip of the electric connector.

Job done.

Hope this helps i know its not the best without pics but its a start hopefully can get some pics up soon

Sam

Sent from my SM-G900F using Tapatalk
 

samblake92

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So turns out after replacing the n75 that wasnt wvwn the problem the car will boost fine through the gear range and then randomly, could be after 5 or 20 mins driving, will just drop off and ill have no turbo at all kind of like a small limp mode feature but got no idea what it could be causing this any1 got any ideas
 

mty12345

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Jun 17, 2011
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That is limp mode by the sounds of it, it will only boost to 5psi max so will feel like no boost at all in my experience. If you turn the ignition off and on again does boost return? If so then thats limpmode for sure. Have yoy tried reading the fault codes when it happens?
Could be loads of things from a splt PCV hose or the N249 delete causing boost spikes http://www.audizine.com/forum/showthread.php/554859-N249-delete-Why-you-should-not-do-it
If you can get a fault code then it might give a better idea of whats causing it.
 

samblake92

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You hit the nail.on the head there mate thats exactly what its doing on the boost gauge its going up to 1.2 psi then dropping and suddenly no boost untill i turn ugnition off and back on have heard it could be were its been mapped stage 1 that the restrictor hasnt been taken off or changed so that after it hits a cetain peak the ecu sends it into limp mode bit of a pain in the backside of im honest
 

arb79

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Oct 18, 2010
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Sorry to crash thread but can I ask a quick question...

Is the N249 bypass only worth doing if car is mapped? Or does it make a difference to standard engines too....?

Mines a 225 Lcr by the way.

Cheers guys
 

samblake92

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Ive got a 180 LC and IMO mate i havent really seen any difference but then again the car keeps going limp on me so once the restrictor is sorted and i have a little play i will post and let you know
 

mty12345

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Jun 17, 2011
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You hit the nail.on the head there mate thats exactly what its doing on the boost gauge its going up to 1.2 psi then dropping and suddenly no boost untill i turn ugnition off and back on have heard it could be were its been mapped stage 1 that the restrictor hasnt been taken off or changed so that after it hits a cetain peak the ecu sends it into limp mode �� bit of a pain in the backside of im honest

Have a look for split hoses under the inlet manifold area mate. There is a metal bracket that bolts onto it, with a couple of allen key bolts. Underneath the bracket are lots of vacuum and PCV hoses, if one of those is split it can cause limp mode due to the mixture being too lean etc. That's the first thing i would look for as lots of faults and poor running can be caused by the hoses perishing. If any of those pipes are covered in oil then chances are thats roughly where your leak is.

Edit, it could be the lack of N249 causing limp as well mate. See the post below as to why, the ecu may well see it as overboost, i'd check the PCv hoses first, but if they are ok, try putting the N249 back and see if that makes a difference
 
Last edited:

mty12345

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Jun 17, 2011
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Sorry to crash thread but can I ask a quick question...

Is the N249 bypass only worth doing if car is mapped? Or does it make a difference to standard engines too....?

Mines a 225 Lcr by the way.

Cheers guys

Don't do it mate, it causes nasty boost spikes when you lift off the throttle. The N249 is there to open the DV ASAP when you lift off the throttle, you gain nothing except more space in your engine bay by removing it and you risk damaging your turbo. See here for more details http://www.audizine.com/forum/showthread.php/554859-N249-delete-Why-you-should-not-do-it
 

arb79

Old but never too old
Oct 18, 2010
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mty12345

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Jun 17, 2011
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I'm not sure about PCV delete, not had any experience of it mate. Myself i'd leave it as is and just make sure all your pipes are ok and not split. The PCV system has a extra tough life due to hot oil vapours which perish the rubber.
 

mty12345

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Jun 17, 2011
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The only thing i would consider deleting is the secondary air system that runs for the first 90secs when you start the car. Mine is still intact though as it's quite a bit of hassle wiring up the resistors so you don't get a EML light all the time.
 

samblake92

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Was toying with the idea of doing that to mine as when it had full diagnostic run before stage 1 two faults flashed up which didnt on my own diagnostic reader which were
1. Secondary air intake system fault
2. N249 fault
Hence why i removed the n249 as was advised to either replace or remove and saving a bit of money i removed it bit silly of me in the long run now though thinking about it
 

mty12345

Active Member
Jun 17, 2011
3,727
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bristol
Was toying with the idea of doing that to mine as when it had full diagnostic run before stage 1 two faults flashed up which didnt on my own diagnostic reader which were
1. Secondary air intake system fault
2. N249 fault
Hence why i removed the n249 as was advised to either replace or remove and saving a bit of money i removed it bit silly of me in the long run now though thinking about it



It's not your fault mate, lots of people say to remove the N249, but i'm not sure they actually understand how it works or why it is there tbh. It basicly allows your dirverter valve to open half a second earlier than it would on it's own when you lift off the throttle. This allows the turbo to freely spin down rather than trying to force air through a closed throttle body. It's only fractions of a second but it prevents a boost spike.

Secondary air fault can be either a pipe that has come off the pump, or the multivalve that controls the system. It's the big silver thing on the right of the cylinder head, might be worth checking the electrical connector is plugged in properly
 
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samblake92

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Yeah will take a look tomorow ive got an early finish in work so afternoon will be spent checking pvc pipes under the inlter manifold and tracing pipework from SIA and checking its plugged then hopefully relax
 

samblake92

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Sorry for the late reply but checled all the pipework and is all fine no splits or loose pipes so thats not the culprit at least but the answer that keeps being given is that it wasnt mapped right and the restrictor at 1.2 bar wasnt taken off the engine so everytime it goes to 1.2 or above then it cuts into linp so will have to try and get it mapped again by a different company and see if thwy can sort it but in the mean time the k04 001 turbo is on but cant boost it as the gasket supplied was the wrong size so have had to order a new gasket and a strongly worded email has been sent to the compnay at fault also there has been a delay in the dispatcg of my uprated fuel injectors so need to wait for both items to arrive now then get stage 2 done. Just delay after delay tbh but hopefully will be a beaut at the end
 

samblake92

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Right turbos all on and sealed properly the bam 225 injectors are in and the limp mode is still continuing after 1.2 bar but no engine management light is coming on for it so unfortunately no codes to scan but have spoken to a few tuning companys and theyve all said that the stage 1 wasnt done properly and that the limiter wansnt either heightened or removed so looks like 99% thats the problem.
 

samblake92

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And in regards to the n249 removal the same companies have said that it is advised to remove / bypass for a stage 2 and also the SAI which i understand can be done with a blanking plate and a few bolts so might look at ordering the kit for it. Even r-tech have it on there website for stage 2 remap about removing the n249
Link posted below to check it out

http://r-techperformance.co.uk/vag/...lf-audi-seat-skoda/1-8t-stage-2-tuning-guide/
 
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