Requested boost vrs actual boost

[Watto]

Does anyone know if the requested boost should closely match actual boost on a 1.8t mk1 octavia vrs.

I ran a 115 log and notised my rquested boost at WOT is around 2000 mbar and my actual boost never rises above 1350 mbar. Would this be why my 17705 pressure drop code keeps showing.

Items that have been replaced are the N75, N112, N249, DV, PVC, MAP sensor, MAF sensor, all OEM parts. The throttle body has been taken of and cleaned till looking new and reset with vagcom. Tedted for leaks and non found. Mostly happening in mornings or when car has been left standing for awhile but when I start up and go to give it some I hear the turbo starting to spool up then nothing, no boost at all till a switch of and back on then its ok again. But dont do this all the time and sometimes its spooling up late at around 3000 revs and never really pulls like it should. All other blocks read are reading fine and the car runs spot on, very quite very smooth. Its just a very intermitent boost problem. Im starting to suspect the turbo on its way out but not sure yet.

And also does anyone know what the requested boost should be on a stock mk1 occy vrs

[Watto]

Also cars not been mapped. Running stock. And all parts replaced are OEM parts.

[mk1pat]

probably,

 

sounds like you have a boost leak

[Watto]

Thanks for the reply. Its been checked for leaks and non found so now suspecting a faulty or sticking actuator or waistgate.

[missingmyvrs]

Very large leak

Need to smoke test her

Then check wastegate issues etc

[Watto]

did a second log the next day and the requested is around 2000 mbar and the actual is the same, sometimes reaching 2200 mbar,  its been checked numerous times for leaks and non can be found, the engine bay and boost pipes are dryer than a nuns c...  just dont know whats causing the intermittent boost

[BrownBarge]

Condition of DV?

[Watto]

Dv has been replaced with a new oem dv.

[missingmyvrs]

Any codes

[Watto]

The only code that keeps showing is the 17705 pressure drop between turbo and throttle valve check dv. Even after clearing the code. Start the car and rev it and the code comes right back.

[Sysvrs]

Ok I'm only adding my experience bug thought if it cured my code 17705 it might be helpful to others and I'm not sure if something else happened and it was just coincidence but hear it is........

The code kept coming up..... I checked pipes replaced as necessary ..... Code still there ..... Boooooooo!!!!

Got annoyed red the posts and came across a post for secondary air pumps whilst browsing .... So as annoyed as I was with reoccurring fault thought I would do something else and check my pump to clear my head... So off I went and checked my pump.... All seemed ok except the plug was holding in......

Fixed that and jus for giggles cleared the code.....

Yep the code was there so cleared it...... And since that day ........

No code!!

Not saying its gonna work and maybe it's got bugger all to do with the fault but since I have done that plug...... On my car at least..... No 17705 code

[Watto]

Funny you should mention secondary air pump as mine was splitting (rivits wearing out) took the pump of and fixed using stainles steel nuts and bolts. Everytiing was rechecked before re fitting. The only thing that I havnt checked is the turbo. Could a faulty IAT sensor cause boost problems and show that code.

[Sysvrs]

Not entirely sure but I'm replacing my turbo tommorow.....

If there's cracks on the hot side I'm wondering if that could cause the fault as tbh I'm hardly running boost as the turbine is suffering with the Latin disease of singulus bendius bladius

So thought I'd better wind the old actuator down

Possible???

[Watto]

Yeah, report back if you find out. Im just thinking of sending my turbo ti a company called midland turbos for a clean up and diagnostic for £180 plus vat. They replace the bearings and stuff and comes back fully working with 2 year guarantee but checking all options before going to that trouble.

[G-slave]

are you sure you mean 2000 mbar as that would be something like 29 psi?  From a standard k03s?  what gear are you using to read this?

[David 8]

are you sure you mean 2000 mbar as that would be something like 29 psi?  From a standard k03s?  what gear are you using to read this?

 

 

Yeah then you knock off 14.7 psi for atmospheric pressure giving around 14 psi which make me think mapped.

 

 

Watto I'll take a look at the logs soon.

[G-slave]

between the turbo and the TB, you also have an IC setup, which does not appear to have been mentioned here.

How did you smoke test this car?

[Watto]

The intercooler was taken off and checked emptied a little oil out of it and put back as no leaks found. The leak test was done with a compressor and most hoses have been taken off and tested of the car. I haven't had a smoke test done yet as no leaks have been found using all other methods and also cant find anywhere local that does smoke testing.

Thanks david 8. I Appreciate it.

Any one know what the stock psi is on a auq 1.8t 20v 180hp ? A friend said the specs are 1800 mbar but not sure what that is in actual psi or if its correct data.

[BobIzYaUncle]

Watto- midland turbo are great, quite local to me and I know many of people who have had turbos from there recon and new. A friend recently bought a turbo for 2.2 dti vectra, fitted by a garage but had some issues, midland turbo had no problems exhanging it.

A cheaper option could be to replace the main section of your turbo, £120 on ebay new, seen one earlier today

Sent from my GT-I9300 using Tapatalk

[Nerd]

Like Bob said, I've also posted about them before, do a search for CHRA cartridge followed by your turbo type- as long as the cold and hot side housing are intact (including wastegate) that's all you need when most turbo's go. It's a half hour job to strip down and rebuild it with a new CHRA but if you do it just make sure you mark the actuator position beforehand as they're a doozy to get right again if you don't.

 

To test the actuator itself just get it off the turbo (again marking it's set position) then simply suck on the vac control hole, if not then use a syringe and small vac line to check it's holding vacuum- if not then new actuator or uprated forge one that'll hold your boost steadier.

 

To check the wastegate you need the turbo off and you basically do a visual inspection to make sure it isn't warped, the arm isn't bent out of shape etc

 

Turbo seals and bearings is just checking the play with your finger, there should a tiny tiny amount of play but if it's moving about then bad turbo, get a new CHRA and done.

 

Most turbo refurb firms simply replace the CHRA, they don;t refurb yours, they just replace then sell the old onto a firm who then does the main refurb and sells them back on as refurbed CHRA cartridges.

[Gonzaga]

stock boost is 0.7bar for AUQ engine

[Nerd]

I thought stock was 9 psi with the upper maximum safe levels being around 20-21 but holding to around 16 on the stock actuator

[BrownBarge]

0.7bar is around 10psi which is what the standard is on AUQ

[Nerd]

Wonder where other forums are getting 9psi from. 0.7 bar is 10.1psi - that's a 10% discrepancy in values which is pretty big

Sent from my GT-I9300 using Tapatalk

[Watto]

So if mine is suspected of having a map then how would i tell if iv got a turbo failing of a map problem. My requested acording to vagcom is around 2000 mbar and when it goes into a safe mode the actual never goes above 1350 mbar but after i switch of and back on my actual will be anything from 1900 to 2200 mbar buts its boosting intermittently, sometimes kicking in late at around 3000 revs but always dhows up the 17705 code even after clearing it after the car has been left to cool down all it takes is a start and a rev up and the codes right back again. I just dont know whats causing the intermittent boosting when its boosting and also why it keeps going into a safe non boost mode after its been sat a while. And now stuck between a possible failing turbo or dodgy map but brought it on the assumption of it being stock and never messed with.