Hi there!

 

I've recently purchased an Octavia 1.8T 4x4 estate and these forums have already been more than helpful so a big thankyou to everyone on here

 

I have a couple of questions which I couldn't already find the answers to and would really appreciate the help....

 

First of all, I think it's overboosting. It'll fluctuate between 10 and 12psi (sometimes peaking to around 13 or 14psi) on full boost. I understand this is well over stock boost. However perhaps it's been remapped? Is there any way of me telling whether or not it's been mapped?

 

Secondly it feels to me like it's trying to boost prematurely. At about a quater throttle it'll suddenly, quite out of knowhere, boost straight to full boost. It's constantly trying to boost and it's not a gradual onset of boost, it's pretty much all or nothing. Seems to fluctuate a lot too.

 

Also, when I'm on boost and I let off the throttle there is a quite sudden deceleration. I've not owned a turbo before so perhaps this is normal, however I suspect it probably isn't.

 

Finally, the turbo is much louder than it should be (a loud wooshing noice on boost) and there is a very audiable blow off sound as the DV opens (there's a forge fully recirculating DV installed so surely there shouldn't be any blow off type sound?).

 

Performance wise it doesn't feel particularly down on power. The pickup is great as the turbo spools however it doesn't feel like it's pulling as hard as it should in the upper rev range.

 

Any thoughts and help very much appreciated

 

Olly

The forge dv are typically louder than the standard, but with an uprated air filter even the standard is still pretty audible.  However, if you have a running issue it may be a little louder as its purging more from an overboost, this may get resolved with the sorting of the other issues though.

 

I  can't remember standard boost for your car but I think its around that for the VRS so it may well have been mapped, standard for yours could be about 8?  Forgive me if I'm wrong, all that aside it sounds to me like you need to check your airflow, breathers and charge pipes for splits or loose connections which could explain your hissing sound.  Fluctuating boost could also be an issue with the N75 valve, if the previous guy tuned it they may have tried fitting an uprated one to increase boost characteristics but this can cause more problems without it being mapped correctly.  Or it could just be on its way out (not a particularly common failure though). But if I was you I'd start with a pipe check, maybe get a smoke or pressure test done if you can't see anything.  It may also be worth a scan, no eml doesn't mean the system hasn't logged a fault somewhere which could explain a lot.  While you're doing all that you may want to consider a standard dv or making sure the forge is tuned correctly, as it could be that the diaphragm is fluttering as the spring is wrong or diaphragm is worn, creating a sporadic boost leak.  You can tune the springs with a kit that has a revised piston.  Check it by removal, push the piston right up, put your thump over the top valve and let the piston go, it should stay right up there and you feel the pressure on your thumb, releasing your thumb it should slam down, if it drops significantly or completely with your thumb covering the valve that could be your problem.  There's nowt wrong with standard dvs and could be worth fitting one, much more reliable, check the parts section here or put a wanted post up for any bits you need, there's often plenty of stuff floating around.  Hope that helps? 

 

Jon

Do you have an open cone filter? A recirc valve will give you a TSCHHH sound if you have one. A cone filter may explain the sounds you're hearing on boost too, but they could also point to a boost leak.

 

My 1.8T is the first turbo petrol car I've owned and the first with an open filter and recirc valve, I was paranoid about all the noises it was making even to the point of rebuilding all the pipe work, but the guy who mapped it said it was perfect, no boost leaks or issues on that side of things. Its just how it sounds with the cone filter

 

If it has been modded and not mapped that may explain the spikey nature, mine was rather spikey and unpredictable with a bunch of mods until I got it mapped to suit. The dyno pre-mapped showed large torque spikes and a very unsmooth curve which is much better now.

The forge dv are typically louder than the standard, but with an uprated air filter even the standard is still pretty audible.  However, if you have a running issue it may be a little louder as its purging more from an overboost, this may get resolved with the sorting of the other issues though.

 

I  can't remember standard boost for your car but I think its around that for the VRS so it may well have been mapped, standard for yours could be about 8?  Forgive me if I'm wrong, all that aside it sounds to me like you need to check your airflow, breathers and charge pipes for splits or loose connections which could explain your hissing sound.  Fluctuating boost could also be an issue with the N75 valve, if the previous guy tuned it they may have tried fitting an uprated one to increase boost characteristics but this can cause more problems without it being mapped correctly.  Or it could just be on its way out (not a particularly common failure though). But if I was you I'd start with a pipe check, maybe get a smoke or pressure test done if you can't see anything.  It may also be worth a scan, no eml doesn't mean the system hasn't logged a fault somewhere which could explain a lot.  While you're doing all that you may want to consider a standard dv or making sure the forge is tuned correctly, as it could be that the diaphragm is fluttering as the spring is wrong or diaphragm is worn, creating a sporadic boost leak.  You can tune the springs with a kit that has a revised piston.  Check it by removal, push the piston right up, put your thump over the top valve and let the piston go, it should stay right up there and you feel the pressure on your thumb, releasing your thumb it should slam down, if it drops significantly or completely with your thumb covering the valve that could be your problem.  There's nowt wrong with standard dvs and could be worth fitting one, much more reliable, check the parts section here or put a wanted post up for any bits you need, there's often plenty of stuff floating around.  Hope that helps? 

 

Jon

 

It's a k03s but should only be 150bhp standard so maybe even less than 8psi as standard? Either way I'm guessing it must have been mapped.

A boost leak test and a fault scan sounds like a good way to go. Will any garage perform a boost leak smoke test or is it a more specialised task?

Also, I'm looking at an 'Any car fault code scanner' on ebay (link here). Will that do the job or do I need a VAG specific one? I'm guessing garages will spank me for the privilage of using there's!?

I will stick a standard DV back in Will a standard one still function properly under increased boost? (ie after remap).

 

 

Do you have an open cone filter? A recirc valve will give you a TSCHHH sound if you have one. A cone filter may explain the sounds you're hearing on boost too, but they could also point to a boost leak.

 

My 1.8T is the first turbo petrol car I've owned and the first with an open filter and recirc valve, I was paranoid about all the noises it was making even to the point of rebuilding all the pipe work, but the guy who mapped it said it was perfect, no boost leaks or issues on that side of things. Its just how it sounds with the cone filter

 

If it has been modded and not mapped that may explain the spikey nature, mine was rather spikey and unpredictable with a bunch of mods until I got it mapped to suit. The dyno pre-mapped showed large torque spikes and a very unsmooth curve which is much better now.

 

It's completely stock apart from the forge recirculating DV and boost gauge. At least it's had nothing obviously done to it that I can see. I was planning on getting it mapped but I'm getting the impression that it's already been done!

I suppose some of the above issues could been down to a bad map?

Standard dv will see you right all the way through stage 2 so will be fine. 

 

Smoke test is kind of specialist in that not all garages will have equipment, but most garages should be able to offer some kind of pressure test.

 

VCDS scan would be best, especially as no eml has come on, my friendly local will just read my codes for £25, I think garages can be a bit unreasonable regards the cost/time if all you want is the codes read...anyway, they may charge up to £40 I suppose, have a ring around, you can try generic scan but really you'd need vag com/vcds, a good garage will probably have it, but that's what you need to ask for, there may be someone on this forum who can help you for beer tokens, check the vcds owners map and drop someone a pm.

 

Sounds like it has been mapped, may not be beyond the realms of doubt that there is a software issue, but I'd check all this other stuff first.

I just went to my local garage who happened to have a vag-com. Scanned it for £10, nice bloke

It's brought up 3 seperate codes...

17705 - Pressure drop between turbo and throttle valve. P1297.

17608 - Boost pressure control valve (N249) Mechanical malfunction. P1200.

16395 - Bank 1 Camshaft A (Intake) Retard set point not Reached (Over Advanced) P0011

 

I guess the first 2 codes would explain the dodgy boosting. And the final code is just rather worrying! I suppose a new cambelt is in order :/

Could be cam tensioner or cam chain as well (intake cam is driven by a chain from the exhaust cam).

 

I'd get them cleared and see if it comes back, you have no idea when the codes occurred. Get an ELM ODB2 adapter and you can read/clear them with your smartphone.

 

I'd get your leak found first - boost pipes and breathers. I made myself a smoke tester, worked quite well and indicated where my issues were even if it wasn't able to generate high pressures. Depends how much time and patience you have

Yes you never know which are old uncleared codes. Cam one could also be cam sensor, easy swap but could be an old code.

As said get your leak tested. The n249 could be giving funny readings as a result, or there could be a dodgy connection somewhere. At least it's been narrowed down a bit.

Buy a blue vcds cable on ebay for £7 and download vcds lite from the rosstech site for free. That'll do all your code reading needs

Having a leak test tomorrow. I hope there is a leak, will explain a few things!

 

I'm thinking the camshaft code might be down to the cam tensioner...I've not noticed it before but there's a very definate rattle/tappety noice coming from the cambelt area. I've heard that a bad tensioner can cause this? Would tie in with the error code anyway.

 

Thanks BrownBarge, very helpful!

Don't think lite is free anymore?

Yep it's free, I just downloaded it

Sweet, is that a free trial? The ebay cables are usually fine mine was ok and didn't cost much. Wish there was a free trial for Saab diagnostics lol

I haven't used it yet but as far as I can tell the lite version is free, permanently

That's good. It won't have full features but will get your codes read and cleared which is the main thing we need it for. I had the full version but never exploited it fully...ask me no questions I'll tell you no lies lol

Just to add a bit about your dump-valve noise...

 

I fitted a Forge re-circ DV to my VRS about four years ago, along with a Pipercross replacement panel filter, when I had my stage 1 Revo remap done at JKS.

 

This setup is ridiculously loud on mine - I don't know if the noise is down to the new valve, or the panel filter...probably a combination of the two. However, i'm still running all stock inlets and airbox etc. and stock intercooler, so it's strange how loud it is.

 

I can hear EVERYTHING that the turbo is doing, from low rpm spooling up, right up to full pressure - and when I let off, the WOOSH is comparable to some cars I have heard with a completely open vent DV! Under bridges and through tunnels it's good fun, and anywhere there are pedestrians nearby, the dump noise is often enough to make them look round. Even when driving sedately, I love the constant ssshhhhh-tssshhhh sound that it makes all the time

 

So I wouldn't worry about the noise - it's normal with the Forge it seems.

^^ mine was loud with a Pipercross panel when I had a forge, car ran better with standard dv which was also still pretty loud with the pipercross panel. The noise if the forge was reduced slightly when my bad map was corrected, but as you say ray it was still almost 'dump valve' loud, but sounded more consistent and less asthmatic.

haha ok well that makes me feel much better about mine! I can hear everything too, loud and clear. I like it, however I'm going to swap a standard one back in to see if it runs better

Standard dvs are much less hassle, need no tuning or servicing. When I spoke to CR Turbos (who know their onions) when I needed an actuator they said "most forge stuff is junk to be honest with you" lol. Get stuff mapped and tuned right then yeah all good, and the stuff looks nice, but going through the tuning process I learned that you don't have to uprate everything to suit.

Yeh it's certainly running better now with the stock DV.

Had the sump off and cleaned all the gunk from the oil to tensioner pipe. Replaced the tensioner and belt (belt looked terrible, needed doing!). However the tappetty/ticking/rattling noice is still very much present, if not louder. Sounds like it's coming from the left side of the head or belts, hard to pinpoint but it's pretty loud and driving me mad! Any ideas?!

Yeh it's certainly running better now with the stock DV.

Had the sump off and cleaned all the gunk from the oil to tensioner pipe. Replaced the tensioner and belt (belt looked terrible, needed doing!). However the tappetty/ticking/rattling noice is still very much present, if not louder. Sounds like it's coming from the left side of the head or belts, hard to pinpoint but it's pretty loud and driving me mad! Any ideas?!

You sure it's not the good old evap can? Put your thumb on top when you hear the ticking see if you can feel the rhythm.

A quick question while theres attention on this topic. I've got a boost gauge in mine after the recirc valve on a 150bhp AUM. Accelerating in gear will peak at 10psi of boost trailing off to 7-8 in higher rev ranges, but accelerating through the gears it will tend to peak at 7-8psi and trail off to 6-7psi. I plug a code reader into mine every now and then to see if theres been any hidden faults logged and it came up with 17705, I cleared it, drove it a short distance both accelerating through the gears and accelerating in a single gear, again the gauge showing boost levels as above, re checked it on the code reader and no faults logged. It will feel like it hesitates slightly mainly going from 2nd to 3rd under full acceleration, 2nd to 6k, put it into 3rd, a seconds hesitation and you can feel it boost again. Is this a feature of the traction control, boosting characteristics of lower power versions or a sign of issues to come?

The fault code isnt severe enough to throw up any dash lights, it just appeared when I read it.

A quick question while theres attention on this topic. I've got a boost gauge in mine after the recirc valve on a 150bhp AUM. Accelerating in gear will peak at 10psi of boost trailing off to 7-8 in higher rev ranges, but accelerating through the gears it will tend to peak at 7-8psi and trail off to 6-7psi. I plug a code reader into mine every now and then to see if theres been any hidden faults logged and it came up with 17705, I cleared it, drove it a short distance both accelerating through the gears and accelerating in a single gear, again the gauge showing boost levels as above, re checked it on the code reader and no faults logged. It will feel like it hesitates slightly mainly going from 2nd to 3rd under full acceleration, 2nd to 6k, put it into 3rd, a seconds hesitation and you can feel it boost again. Is this a feature of the traction control, boosting characteristics of lower power versions or a sign of issues to come?

The fault code isnt severe enough to throw up any dash lights, it just appeared when I read it.

I should add its always felt like it hesitates under hard acceleration going from 2nd to 3rd but this is the first time ive seen 17705 logged.

A quick question while theres attention on this topic. I've got a boost gauge in mine after the recirc valve on a 150bhp AUM. Accelerating in gear will peak at 10psi of boost trailing off to 7-8 in higher rev ranges, but accelerating through the gears it will tend to peak at 7-8psi and trail off to 6-7psi. I plug a code reader into mine every now and then to see if theres been any hidden faults logged and it came up with 17705, I cleared it, drove it a short distance both accelerating through the gears and accelerating in a single gear, again the gauge showing boost levels as above, re checked it on the code reader and no faults logged. It will feel like it hesitates slightly mainly going from 2nd to 3rd under full acceleration, 2nd to 6k, put it into 3rd, a seconds hesitation and you can feel it boost again. Is this a feature of the traction control, boosting characteristics of lower power versions or a sign of issues to come?

The fault code isnt severe enough to throw up any dash lights, it just appeared when I read it.

Sounds like it could be either a split or loose connection in an air line somewhere, could also be weakening actuator.

However there are many reasons for a 17705 and I believe there is a sticky thread on this forum menu.

It's at 10psi for the 150? Is that a cheeky little map or is that standard boost?

The Ko3s turbo does run out of puff a little at the top end but it shouldn't really drop much below what the ecu is requesting. Mine used to hit peak boost in all gears and follow requested until around 5500rpm where it would really tail off, I suspected a weak actuator as I'd tried just about everything else. It could be the spring or the diaphragm inside can perish a little.

It sounds like there is something that needs sorting, a smoke test for leaks would probably be my first move. But as far as anything terminal I wouldn't worry too much yet, only problem is your turbo is having to work a bit harder than it should as it's losing boost somewhere. Hope that helps

Thanks for the reply. I read that they should be between 8 and 10psi as stock. Just had a read of the sticky thread, it sounds basically like it could be a whole bunch of things, its a real shame the fault codes aren't more specific. I had a check of the hoses I could easily access yesterday after resetting the fault code and gave them all a little extra push on. Ill just have to see how it goes.

A smoke test sounds thorough, is it something most places can do?