Hi all, I'd appreciate anyone's thoughts/suggestions as to the cause of some low performance/running issues I'm having please! Car is a 1.8TSI Skoda Yeti 4x4 with a K04 and appropriate hardware/software to match (S3 intercooler, 'sport' catalyst, large bore downpipe, remapped etc). It made 320+bhp when built for the previous owner, but since I picked it up it's never been quite right - feels more like 200-220bhp at the moment. It's already been back to the tuners that built it, but they're stumped as to the cause, and set off on the course of throwing new parts at it in the hope that they'd get lucky. This wasn't a course of action I wanted to sponsor!! Symptoms Down on power. Black smoke on full-throttle = fuel. Occasionally logs P0299 "Control Range not Reached", but no other fault codes. MAF reading fluctuates whilst on full-throttle, you can see a corresponding change in actual boost pressure (all logged in VCDS). Sounds very 'surgey' when the above happens, sounds and feels air-path related... Things checked/replaced Boost leak check done by tuner Mitivac test on turbo actuator done by tuner MAP sensor replaced by tuner MAF sensor replaced N75 replaced Diverter valve replaced PCV replaced New correctly gapped spark plugs Do these motors suffer from carbon build up issues like the earlier direct-injection VAG motors? Any thoughts/suggestions gratefully received! Cheers, Andy
P0229 = Underboost condition, although there might be some other driver as the root cause. I will point my friendly master tech in this direction if that will help. Not so up to speed on things gone wrong on the EA888.
Thanks Eddie! Pete (Yoof) and I have given it a going over, but the EA888 is new to us. The P0299 code is what led me to replace the PCV, N75 and diverter valve - but I think it's a red herring... The larger turbo obviously means the boost threshold is higher (2500rpm ish) than the baby stock turbo (~1800rpm), so if you hold it WOT at 2000rpm the unmodified diagnostic is expecting to see some boost - but the big snail can't deliver, and logs P0299. I'm fairly sure that's right, as I can get it to log repeatedly under the same condition - but never when rpm is above the boost threshold. If my VCDS logs are right, then these motors run quite lean til fairly high rpm. It's close to stoich around 3500rpm, and hits lambda 0.8ish by 6000rpm. It pulls 3deg of timing out due to knock close to max rpm, and once you've kicked it's head in a lot that might hit 6deg eventually - but around peak torque it's all fine, and when it has its boost/MAF spazz there's no timing retard due to knock. Andy
A good tuner would not leave that fault code flagging.... Can you share your vcds logs of airflow and boost? A complete set of the 1-5 logging blocks from APR's site provides a good base for looking into error states. http://www.goapr.co.uk/support/datalogging.php
m1keh - agreed re: leaving the code flagging - but I should reserve judgement 'til the car is back to full health to be fair to them. Here's some VCDS logs from last week which I've also plotted out into Excel. The "Timing Retard" one has more data in it, and the car has a good old fit between 3500rpm and 4500rpm in that trace at 230-234 seconds. It's also a bit special at 228 seconds whilst spooling. https://www.dropbox.com/s/2rvkugo5128j8zb/BetiYetiTimingRetard.xlsx?dl=0 This "Boost" plot has less data, but at a higher sample rate. https://www.dropbox.com/s/55x6by4riy4cm7c/BetiYetiBoost.xlsx?dl=0 Any thoughts gratefully received! Edit to add - if you view the logs directly in Dropbox it's a bit hard to see what's going on, but it should let you download them to have a proper look. Andy
Well - actual boost in those logs looks reasonable for the amount of power you are after. Seems like the weirdness maybe more fuel related... Have you done any logging of the fuel pressure and lambda at all?
Thanks again for your input! Here's a log of lambda (scaled x100 to fit it on the graph nicely!); MAF; rpm; rail pressure (target and actual) and injector timing. https://www.dropbox.com/s/fbhb7fu6h5rrxna/BetiYetiRailPressure.xlsx?dl=0 Around 220 seconds you can see the MAF value have a fit. Boost pressure isn't shown to fluctuate too much, but the sample rate here is quite low (as I was logging so many parameters) so I think that's why you don't see it. At ~4000rpm it's just shy of 1.5 bar boost (2450mBar), is running lambda 0.94 (steadily richening from about 3k onwards) and rail pressure is circa 160bar (target and actual very similar).
Rail Pressure seems to be ok too. I cant understand with what is fairly consistent boost pressure why the MAF is seeing such a big fluctuation. Can you log the wastegate duty cycle request too and throttle plate position too? Does your engine have runner flaps?
It's a weird one isn't it?! Both those values are actually in the raw data of some of the existing logs posted up, I can re-plot them if that's easier? Throttle position is always 100% when accel pedal is floored, and the N75 valve duty changes during acceleration - but doesn't fluctuate wildly at any point. N75 duty is pegged at 100% below the boost threshold, and is between 70-85% ish across the rest of the rev range. It doesn't appear to clamp or flitter around at any point. If you only log MAF and boost pressure so you can get a higher sample rate, you do see variation in the boost pressure when the MAF fluctuates - but not a wild variation. Yes - it does have inlet manifold runner flaps. I believe these are binary in their states: on/off, and are in the 'tumble' position below 3000rpm and open up above that engine speed? With the engine idling I've moved them to the open position manually, and it logged the appropriate fault code - so I'm assuming the position sensor is working correctly. That also made me assume (perhaps incorrectly!) that the flaps must be working properly during normal running - as I'm not getting any DTCs relating to the flaps. Thanks again for the input - it's really useful to have someone to use as a sounding board!
Scratch that, I took a higher sample rate log tonight and N75 duty faffs around too: https://www.dropbox.com/s/cev0ikmq2s6nti8/BetiYetiBoostFuelN75.xlsx?dl=0 MAF is all over the shop in the above trace, N75 duty fluffs around at one point, and boost pressure isn't very stable either. What's weird is that lambda is 0.8 from 2200rpm all the way to 6700rpm this time, whereas in the previous logs it was initially much leaner (stoich to 0.94 by 3000rpm, richening to 0.8 by 5000rpm or so). The fact that N75/wastegate request is going wonky suggests that the EMS is having trouble managing boost for some reason? Ergo do I have a boost leak and/or actuator problem that the tuner didn't pick up?
Had the system pressure checked locally today, no leaks... Also had it on a dyno (4wd) at a respected local tuner. 305PS at fly was the answer, but with it pulling 6 degrees of timing top end - and enrichening to lambda 0.73 above 6,000rpm. The timing retard and extra enrichment probably account for the missing 20PS or so over its original claimed figures.
Just too much boost being requested and running into surge possibly? A ko4 on a 1.8 shouldn't make much more power than that...
Yeah, not too fussed about the power - it's just a number at the end of the day, and you don't see the timing pull on the road until you've done a few WOT pulls. Edit to add: switching from Tesco 99RON to Shell V-power/Nitro seemed to be the answer in the end. Car was mapped on the Shell fuel and just seems happier on it!
