Start-Up Issues and 3k rpm cutout 1.8t ARX 4x4

[Shrako]

Hello guys,

Unfortunately the first post on the forums would be about something not pleasant rather than a build thread.

First off - the car is a 2001 Skoda Octavia 4x4 with the ARX engine, hence the K03s turbo and the full SAI, n112 and n249 package.

Ever since I got the car I had issues with the cold start but not other issues. Then being very smart I got a tune which resulted in a cut out at around 3,000 rpm - the car just stops accelerating followed by a big bang somewhere at the front and then I have to get off the throttle and back on it and everything is fine past 3,500 rpm.

After changing coils and sparks, knowing that the stock DVs are prone to failure after a tune, I got a new DV. Being the smart lad that I am, I ended up getting the infamous SPLITR from Forge. The result was... The exact same behavior. After vising another tuner, he concluded that the issue was with the SPLITR and indeed, disconnecting the vacuum going to it, putting a small screw to block the vaccum line. Indeed the issue with the cold start and the cutout was gone. However, I knew that running the car like this was not fine, and I was mildly worried that with the disconnected DV I still couldn't hear the distinct tutututu, which I should be getting at this config.

I ended up bypassing the N112 and the N249 (the correct way - getting the vacuum from the manifold, not tapping into the FPR) and the result was a much better DV operation, however by twisting the SPLITR I was only moving the cut out point between 3 and 5k RPM. Disconnecting it again made the car run perfectly.

A couple of days ago my 007P arrived, since after reading many posts about the beauty that the SPLITR, and having the tuner opinion that it should not be used on a 1.8T, I decided this was my point of failure. After I installed the 007P (tried both ways) I get the same result. Engine rattles like a mofo when starting up and cuts off a 3k RPM. Whatsmore, with the vacuum line disconnected and the much clearer noises that the 007P does compared to the SPLITR, now I can certainly say that when disconnected I can hear air going trough the filter (running a standard cone filter which results in a woosh sound). However, when connected I can hear only a sound of air going trough a small metal pipe (thats what it sounds like) below 3k RPM and can hear the air filter woosh above 4k. With the 007p disconnected, I cant hear any sound of turbo surge, which I guess I should get.

 

Replaced the N75, checked the fuel pump relay - no issues.

 

 

Did the full SAI and EVAP delete, chain tensioner and chain (terrible start up rattle is gone, intake cam was way off) and a new OEM Bosch MAF.

Not only did this not fix anything, but the car now devours fuel like crazy.

With the A/C off I get around 0.8-0.9L/hour while still, however with the A/C on in gets to 1.8-1.9 and this difference goes over to driving and etc - with the AC on I average 14 l/100 city driving, with the AC off - 10.5 l/100.

 

Logs - 

 

https://log.malonetuning.com/chart/261485#H8KLCABfZHNdAgNNwozDgQ7DgiAQRMO%2FwoXDs8KSFG3Con4Lw6HCgMKywqHCm1RowpbDhVTCv17CoMKJw7E4M2%2FCnsK1w6rCkcKfd0rCqCPDp8K6FQXCk8KDXsKuwpnDqcKDLcKCworCmMKQwr3CoDrClsO0QhYtWcOvw5rDr8OUH8OHZ8KhwoA6eMOxBcKlwpdnEMKuw5gXH8KCfsO%2FYMOFFBcZwrJGw74NdgIDM8Kcw6ACV8K4woFpVmUGw6fCq8OkwrLCrTTCvGZ2w64LWQJuTsK4AAAA

https://log.malonetuning.com/chart/261486#H8KLCABfZHNdAgNtwo5BCsKDMBBFw68yw6sJJGppw68SwrJIwpshBjTCkXEUw5vDk1cjFBddw457w79%2Fw4ZaYBrDi0oqeMOxMwlgwoPCrcODf8K4OcOwwqvCjMOPwpRJRS7DizQDw6oTDsKFw5PCh8O2EyFSJsO2QnDCmsK8EsKLwpLCojbDpcK3dDTDjk7Cn8OCZV1jwovDggsdw4bCh8Kgw57CvzBwworCvcOUwrE9eRFWwqPDgRvDnsOxwrHDv8OWOQRTQ37CkTJPQ8KqwqPCpnPDrgvCjCEkc8OjAAAA

 

 

 

 

[mac11irl]

Thats a lot of info...

First thing i ask though, do you have the correct spring in the 007p? Iirc they come with many different ones depending on what boost pressure you are mapped to run. If the wrong pressure spring is in it, then it wont activate as your engine "wants" it too.

Might be worth checking..

[Shrako]

Hi,

 

Currently I am running a blue spring (got it with two spings - blue and green).

 

I know it might be a bit stiff, but since the DV is on a vacuum directly to the manifold worst case scenario is that it won't be able to open it and I have the 007 currently mounted in the "wrong" position where the piston is getting constantly pushed by boost so it might need the extra stiffness. 

[mac11irl]

Have you maybe tried setting it up correctly then, with the other spring? And rule it out completely??

[Shrako]

Hey, gave it a go in the correct (silent) position with the softer spring and there was no difference in the behavior of the car.

[SuperbTWM]

Just buy a stock DV, the forge ones are over-rated IMO, I've had one in front of me in a bowl of water and pressurised it with 2 Bar and it didn't leak at all. The Forge splitR is part BOV anyway and cannot be used on your engine so its not surprising you had issues with that, by venting with with a BOV you are removing metered air from the intake so you would have less air than the ECU was fuelling for.

 

IIRC you should be running a yellow spring at most in the 007p with that boost pressure, I would say the others are too hard.

[Shrako]

Tested it with a perfectly working stock DV off of a friends Golf, the car behaved in the same way, while the Golf had no issues, so I would rule out the DV as a cause.

[robek85]

Hello. I own exact same car. Tuned to about 220hp.

Looks like you're overboosting - do you have a standard downpipe? 

MAF reading looks to low for a tuned car.

So after new plugs and coils you still get a big bang from the front?

 

[Shrako]

New plugs and coils - big bang continues. Replaced the MAF with a brand new Bosch unit. I am running the standard downpipe.

[robek85]

Can you check your water temperature reading via vag-com?

Also your intake temps are way too high if you ask me. From what i know above 50 celsius computer pulls back timing and boost.

[Shrako]

It was really hot outside when I did the logging. Today I checked what VCDS showed prior to trying to start the car - the outside temp was around 12 degrees. The coolant and intake air temp both showed 18 and the Throttle Valve Angle was at 4.7 %. When the car failed to start on the first attempt, the coolant temp value stayed at 18, the intake dropped to 12 and the TVA went to 0.4 %. On the second attempt the car started perfectly.

[Shrako]

New Chain and tensioner are in, everything that is a vacuum and can be gone is gone and a new FPR vacuum is in. The car definitely feels better and the loss of power is now almost not noticeable when going flat out in a high gear from low to high RPM. Cold start still sucks though.

[Shrako]

In case someone faces the same issue - resolved by replacing both the fuel pressure regulator and the fuel pump. Both were faulty.

[SuperbTWM]

Good to hear you have got to the bottom of the issue