Strange Behaviour

[pinkgti]

Hi I'm a newbie but have been looking at these forums for a while.

I had my Mk6 GTI tuned recently and it's not exactly behaving itself.

Anyway thought I'd post some pics of some logs and see if anyone has any idea whether it's a problem with the tune or hardware.

First one's shows the actual boost vs requested boost @ full throttle 2nd gear



Second is moderate acceleration with fixed throttle position running with DSG in "D". Short-shift in 1st, 2nd gear to 3,000RPM and then cruising. Note that the boost drops off after 2,000RPM which results in loss of power.



Anyway interested in your thoughts and yes I will be going back to the tuner but want my ducks in a row first.

[h100vw]

You need to do logs in 3rd, you get a much better idea of what's happening. What do you mean by not behaving itself?

Back to the tuner is the way to go. Boost leaks are not uncommon.

Gavin

[pinkgti]

You need to do logs in 3rd, you get a much better idea of what's happening.

Thanks Gavin. OK 3rd gear but then I'll have to wait until I can find a nice bit of highway (110km/hr) zone to try that out

What do you mean by not behaving itself?

Boost comes on way too late - 3,500RPM. I would have thought that the requested and actual boost would have followed each other a lot more closely until the K03 runs out of puff.

Back to the tuner is the way to go. Boost leaks are not uncommon.

Yep just thought that I'm eventually getting boost that maybe it's something else.

Thanks for your suggestions.

[h100vw]

Thanks Gavin. OK 3rd gear but then I'll have to wait until I can find a nice bit of highway (110km/hr) zone to try that out



Boost comes on way too late - 3,500RPM. I would have thought that the requested and actual boost would have followed each other a lot more closely until the K03 runs out of puff.



Yep just thought that I'm eventually getting boost that maybe it's something else.

Thanks for your suggestions.

You'll get a better look at the boost on a 3rd gear pull. A rip up to 5000 would probably give enough info, it's going to die off any way but assuming your tune is from a known source, they won't be requesting more boost than the turbo can make low down. Otherwise you could spend a lifetime chasing non-existent leaks.

As a mild comparison my Polo makes full boost by 2800 and the S3 by about 3200.

Gavin

[pinkgti]

You'll get a better look at the boost on a 3rd gear pull. A rip up to 5000 would probably give enough info, it's going to die off any way but assuming your tune is from a known source, they won't be requesting more boost than the turbo can make low down. Otherwise you could spend a lifetime chasing non-existent leaks.

As a mild comparison my Polo makes full boost by 2800 and the S3 by about 3200.

Gavin

Yeah not too concerned about the 5,000-6,000 at the moment - mainly bottom end as that's what I use 99% of the time anyway.

The other thing is under moderate accelerate the power delivery isn't smooth - kind of surges. Between 2,000-3,000RPM is a flat spot.

So do you think it might be a problem with the turbo if it's not spooling up fast enough? Or maybe just a stuffed up tune.

[gldgti]

I would check with the tuner ASAP, but if it was a hardware problem it could be an exhaust leak between turbo and engine (manifold somewhere) or perhaps the wastegate is not closing properly.

Antoher thing to consider might be foreign object damage of the turbocharger compressor wheel.

[pinkgti]

I would check with the tuner ASAP, but if it was a hardware problem it could be an exhaust leak between turbo and engine (manifold somewhere) or perhaps the wastegate is not closing properly.

Yeah talking to the tuner but just logistically a challenge so trying to eliminate possibilities a the moment. What's the best way to check for an exhaust leak? and waste gate?

Car is only 18 months old, but I guess anything is possible.

Another thing to consider might be foreign object damage of the turbocharger compressor wheel.

Is that easy to check?

[h100vw]

Yeah talking to the tuner but just logistically a challenge so trying to eliminate possibilities a the moment. What's the best way to check for an exhaust leak? and waste gate?

Car is only 18 months old, but I guess anything is possible.



Is that easy to check?

I'd say don't look too deep just yet. There's every chance of a boost leak. It may take 10 PSI to cause the leak and it may not leak at a fixed rate.

Definitely speak to the mystery tuner

[pinkgti]

I'd say don't look too deep just yet. There's every chance of a boost leak. It may take 10 PSI to cause the leak and it may not leak at a fixed rate.

Definitely speak to the mystery tuner

OK mystery tuner it is. Just tryingto get a logical explanation for how it's driving.

[pinkgti]

Going to remove my ECU and get it sent off for reflashing - car is going to be off the road for a few days but hopefully a new tune file will fix the issue (though if it's a boost leak we're back to square 1).

Will post back once I have a new tune file in the car.

[h100vw]

I reckon the PCV system is a likely candidate. Can lend you a BSH plate if you want to try that after the ECU gets back.

Gavin

[pinkgti]

Righto. After some investigations with the vernier calipers this afternoon I have found an issue with the DP that has been installed. It's a straight through 2.5" system. Not that it's a problem in itself as it's a long piece of stainless tube with some nice blue/purple hues - eye candy for the mechanic.



The issue is the tune file in my ECU is set for a 3" DP

Now just wondering what effect that's going to have and whether that explains the flat spot from 2,000-3,000RPM.

And you can be assured I'll be talking to my tuner on Monday at 9am!!!!

[pinkgti]

I reckon the PCV system is a likely candidate. Can lend you a BSH plate if you want to try that after the ECU gets back.

Gavin as always going above and beyond the call of duty. If it doesn't get sorted will definitely be asking for a full refund and will be giving you a call. Either way I'm up for a DSG tune so I'll give you a call or maybe you can let us know when you're next down this way.

[h100vw]

Gavin as always going above and beyond the call of duty. If it doesn't get sorted will definitely be asking for a full refund and will be giving you a call. Either way I'm up for a DSG tune so I'll give you a call or maybe you can let us know when you're next down this way.

The important bit of the DP is right after the turbo. The gases contract to an extent afterwards, so dropping to a 2.5 system is unlikely to restrict flow.

Can you see the diameter of that?

Logging would be the answer to the flat spot. Surely they need to see that before writing up another tune?

Gavin

[pinkgti]

The important bit of the DP is right after the turbo. The gases contract to an extent afterwards, so dropping to a 2.5 system is unlikely to restrict flow.

Can you see the diameter of that?

Logging would be the answer to the flat spot. Surely they need to see that before writing up another tune?

Gavin

Yep 2.5" straight off the turbo. Managed to get the verniers onto it and confirmed diameter before the weld onto the flex section.



I'm going to go back to the tuner as they were meant to put a 3" system on.

It's 2.5" behind the cat so that it can connect up to the standard muffler which is OK but it's meant to be 3" out of the turbo.

Anyway not sure what effect putting a smaller exhaust on a tune for larger exhaust would have anyone???

Yes so new DP and then logging in that order.

Anyone after a 2.5" straight through DP as I know where there'll be one going cheap.