Boost dropping hugely - Recirculation valve or Wastegate?

[Martin191]

So another, more serious boosting problem has reared its face. 

 

When in 5th gear / 4th gear and giving it some welly my car will boost to 22-24 psi, then occasionally (been much more frequent recently) drop the boost down to 5-10psi. It's as if the recirculation valve opens and recirculates the boost back in to the system, or on the other hand it could be the wastegate not holding boost, which is very plausible considering it's the original wastegate.

 

A bit of background information -  

I've got a Forge 008 with the yellow spring installed which I bought brand new in February 2016. This has also been serviced recently, which didn't solve the issue. I have also tried a forge 007 which didn't solve the soft limp mode (17705) issue I was having.

 

When I lift off the throttle then put my foot down again it will temporarily solve the issue. However this often doesn't last long. It can also occasionally boost to 22-24 psi, drop 2-3 psi off, then recharge back up to 22-24 psi once again (I have had this issue for a good while now but its never been serious enough to drop almost all boost).

 

Just seeing what others think about it. This could also be the 17705 issue I've been having, for any of you who remember my last post. 

 

Any help is appreciated.

Edited 28 May, 2016 by Martin191

[kentphil1]

Am I correct in assuming that this car would be mapped with those boost figures?. I am assuming the car is running good intake hoses rather than older slightly perished ones?.

[Mankee]

Sounds like overboost. Mine peaks at 21-22 psi (1.5 bar) when the turbo comes on song and then holds at 13/14 psi (1 bar). Who did the map, how long has it been on for, did the 17705 code appear straight after mapping etc.?

[Martin191]

All the hoses other than the tip have been switched for hard pipe or silicone, it was mapped to 23 psi, it's only in 5th that it will climb to 24 psi, even then that's occasional. The 17705 code has been with my car since I've bought it too, so I don't think it's a software issue.

What I don't understand is that it can sometimes be fine then other times it can slip in 3rd to 5th. But lifting off the throttle and reapplying the throttle always fixes it temporarily. This is why I think it's the forge recirc valve.

[kentphil1]

Have you tried substituting an oem valve?, 23psi should not bother the standard diaphragm valve to rule out the forge. Have you done any logging to see why you are getting the 17705 code?.

 

Without being nosey, was the map done by one of the better mappers?, as this was an issue that Shark and R-tech and others have worked really hard to eradicate from the standard code in the VAG ecu, the process of remapping just appears to put it under the spotlight so you notice it more often.

[Martin191]

Have you tried substituting an oem valve?, 23psi should not bother the standard diaphragm valve to rule out the forge. Have you done any logging to see why you are getting the 17705 code?.

 

Without being nosey, was the map done by one of the better mappers?, as this was an issue that Shark and R-tech and others have worked really hard to eradicate from the standard code in the VAG ecu, the process of remapping just appears to put it under the spotlight so you notice it more often.

The 17705 code wasn't really the highlight of the post as that only really happens when the engine is cold / in 1st gear. What I'm trying to work out is the persistent boost drop when in high gears. How I describe it is - imagine your car's clutch was slipping, where you put your foot down and nothing happens, well it's like that apart from rather than the clutch slipping all the boost is dropped off. It only happens when you strain the turbo.

 

In regards to the remapper - I got it remapped at V12 Tuning Manchester. They were highly regarded as a Manchester based remapper and I'm happy with what it's been remapped to. However, they skipped some vital health checks on my car like air leaks and error codes. So it's up to you how you judge them. Personally I was happy until he blocked my phone calls when trying to get it booked in for the health check he missed beforehand.

 

I'll be trying another recirculation valve when I get back to Manchester, but as said before, this didn't fix the 17705 code problem. (I can't say if it fixed the boost drop issue, as at the time, this wasn't a problem I was facing.)

 

I will do some logging when I next go for a drive. Though this may not show anything as the problem is very intermittent.

[YellowCar]

My Elite remap from a local dealer got round the 17705/limp mode caused by my 1st map. Did seem to purely be a software issue for me, believe this has been the case for others here too.

[Martin191]

My Elite remap from a local dealer got round the 17705/limp mode caused by my 1st map. Did seem to purely be a software issue for me, believe this has been the case for others here too.

I know I still can't rule out a software issue, but when on part throttle I can hear what sounds like my recirculation valve opening to release air back in to the system. This has also got progressively worse since owning the car, which also adds to my hardware theory.

[Ade VRS]

Have you tried a stronger spring in the Forge 008?

Ive heard a LOT of stories that after a remap this issue is more prevalent, there are quite a few threads about on the subject - just search for 'Octavia VRS Hesitation after Remap'.

Different things have worked for different people, I dont think there is a definitive answer.

some have just cleaned and refitted electrical connections, others have just cleaned the throttle body or replaced the N75 valve for an uprated race version.

Have you upgraded your spark plugs since the remap and gapped them correctly?

[kentphil1]

To the OP, just out of interest, have you read through this? - http://www.briskoda.net/forums/topic/252862-17705-fault-code-sticky/

[YellowCar]

I know I still can't rule out a software issue, but when on part throttle I can hear what sounds like my recirculation valve opening to release air back in to the system. This has also got progressively worse since owning the car, which also adds to my hardware theory.

Hmmm I see, did we rule out the actuator? Think we did didn't we...

[Martin191]

To the OP, just out of interest, have you read through this? - http://www.briskoda.net/forums/topic/252862-17705-fault-code-sticky/

Hi, yeah I've been through that check list. I'll do some logging tomorrow to see if I can find an obvious problem.

Yellowcar -

How would I diagnose a bad wastegate? Also the boost does drop off fairly quickly, would that be a sign of a weak actuator?

[YellowCar]

Hi, yeah I've been through that check list. I'll do some logging tomorrow to see if I can find an obvious problem.

Yellowcar -

How would I diagnose a bad wastegate? Also the boost does drop off fairly quickly, would that be a sign of a weak actuator?

It could be, they can perish internally and the spring can get weak. You can unplug the N75 for one run to log boost so it only runs off actuator pressure which should crack at around 5psi. It should get there and hold a flat line. If it tails off in that situation then the actuator is struggling, imagine then how it would cope at full boost...not very well.

[Martin191]

It could be, they can perish internally and the spring can get weak. You can unplug the N75 for one run to log boost so it only runs off actuator pressure which should crack at around 5psi. It should get there and hold a flat line. If it tails off in that situation then the actuator is struggling, imagine then how it would cope at full boost...not very well.

When it goes into soft limp mode it does exactly that. Boosts to 5-5.5psi and won't go any higher than that. I haven't tried taking it above 4k revs when in limp mode to test if it tapers off though. I assume unplugging the n75 will have the exact same effect?

[Bowders1]

if you have yellow DV spring that should be ok . the limp mode will restrict boost to around 5psi. from what you describe I would still suggest bad map. a lot of these so could generic maps can work well on some cars and not on others . especially if some of your hardware is starting to wear . maps tend to expose what is already there but increase it further . most generic maps I have seen cause really bad over fuelling , so perhaps when you de throttle you are bringing fuels trims down to a workable level . fuel pump is another weak spot on mapped cars and 23/24psi boost is on the high region. I would be checking fuelling and logging what is going on at certain revs . I bet your fuelling is all over the place. post some logs and folks will be able to assist better . [emoji106]

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[Martin191]

if you have yellow DV spring that should be ok . the limp mode will restrict boost to around 5psi. from what you describe I would still suggest bad map. a lot of these so could generic maps can work well on some cars and not on others . especially if some of your hardware is starting to wear . maps tend to expose what is already there but increase it further . most generic maps I have seen cause really bad over fuelling , so perhaps when you de throttle you are bringing fuels trims down to a workable level . fuel pump is another weak spot on mapped cars and 23/24psi boost is on the high region. I would be checking fuelling and logging what is going on at certain revs . I bet your fuelling is all over the place. post some logs and folks will be able to assist better . [emoji106]

Sent from my iPhone using Tapatalk

What measuring blocks should I be logging for fuelling?

[Martin191]

Have you tried a stronger spring in the Forge 008?

Ive heard a LOT of stories that after a remap this issue is more prevalent, there are quite a few threads about on the subject - just search for 'Octavia VRS Hesitation after Remap'.

Different things have worked for different people, I dont think there is a definitive answer.

some have just cleaned and refitted electrical connections, others have just cleaned the throttle body or replaced the N75 valve for an uprated race version.

Have you upgraded your spark plugs since the remap and gapped them correctly?

Sorry I missed this.

Yeah I've tried up to the blue spring and yeah I'm now running bkr7e's gapped at 0.28.

 

It's hard for me to tell what has and hasn't worked because when I have tried a different recirculation valve or n75 I was looking out for the 17705 code, not this boost issue. Saying that, I've done all the basic checks ( throttle body / air leaks / removed n249, n112, sai.)

[YellowCar]

I'm with Bowders I still think it's more about the software.

[Mankee]

Another vote for software here.

 

I hate mentioning the "s" word because people are always adamant that the map is good, there must be something wrong with the hardware yadda yadda. But when a car runs perfectly on a factory map and then post-map surges its tits off, bleeds off boost several times throughout a single full-range dyno pull without lifting the throttle, comes up with the 17705 code etc. etc., there must be bugs in the programming. Been there, done that, got neck ache from boost dropping in and out.

 

I did back-to-back dyno runs with standard and modified maps and found that some programming tools just can't control boost as well as others. I used Italian Dimsport tuning tools and we just couldn't iron out the surges. Until we loaded a factory AUQ Leon Cupra 1.8T 180bhp map and it was silky factory smooth, but (relatively) gutless.

 

I'll get off my soapbox now. I'm not having a moan (honest!), just sharing the experience with my own car. Good luck! :sun:

[Martin191]

Another vote for software here.

 

I hate mentioning the "s" word because people are always adamant that the map is good, there must be something wrong with the hardware yadda yadda. But when a car runs perfectly on a factory map and then post-map surges its tits off, bleeds off boost several times throughout a single full-range dyno pull without lifting the throttle, comes up with the 17705 code etc. etc., there must be bugs in the programming. Been there, done that, got neck ache from boost dropping in and out.

 

I did back-to-back dyno runs with standard and modified maps and found that some programming tools just can't control boost as well as others. I used Italian Dimsport tuning tools and we just couldn't iron out the surges. Until we loaded a factory AUQ Leon Cupra 1.8T 180bhp map and it was silky factory smooth, but (relatively) gutless.

 

I'll get off my soapbox now. I'm not having a moan (honest!), just sharing the experience with my own car. Good luck! :sun:

 

I'm sure I previously mentioned (may have been in another thread), but if not: It had the 17705 code before and after it was mapped. 

 

I mean its still a possibility that it's a software issue, but doubtful? 

I'm not an expert by no means, but surely a stock map can't also throw the 17705 code.

 

(I'm not arguing by the way, any input in to getting this fixed is appreciated!)

[Martin191]

I've just been out and done some logging - 

https://drive.google.com/open?id=0B7hLN8RnjHmnczg2VU9YQ0VtRW8

 

The file 3-gear-pull is the extracted data, the others are raw data.

 

Before I lifted off in 3rd gear it did the stutter that I was talking about. The data does not seem to show this very clearly though. 

 

I also logged block 032 which gave me the results - 

-0.8 / -1.6%

[Mankee]

Your coolant temp is lower than normal isn't it?

[Martin191]

It doesn't move from the mid point / 90 degrees. 

 

Last time I took the temperature sensor off It did look a little old though.

[YellowCar]

It doesn't move from the mid point / 90 degrees. 

 

Last time I took the temperature sensor off It did look a little old though.

The gauge doesn't tell the full story unfortunately

[Martin191]

The gauge doesn't tell the full story unfortunately

What would / could this cause? and could it be the source of my 17705 problem?

 

Edit - Only just realised that it was reporting 75 degrees. On the dash it has always averaged 90 degrees.

Edited 31 May, 2016 by Martin191