boostjunki New Member 5 Member For: 3m 28d Posted 10/05/24 05:04 AM Share Posted 10/05/24 05:04 AM I have a tuned G6ET that runs fine when driving normally but when I put the boot in up a hill or to overtake etc it will start running really rough and blow black smoke at around 3500rpm. Once I back off it takes a couple of seconds before it runs smoothly again. It's not logging any codes. It was running great for 18months after HP tune was done. So far I have replaced all plugs and gapped at .7, new Bosch coil packs, 02 sensor, Walbro 460, Scan tool shows its getting to 35psi (absolute) boost, so that's about right for tune at 18psi. Mods done before tune injectors, intercooler, cat delete, CAI, exhaust. Like I said, it ran great after tune, 389kw I'm at a loss. Any help would be greatly appreciated Link to comment Share on other sites More sharing options...
k31th less WHY; more WOT Site Developer 28,724 Member For: 16y 4m 28d Gender: Male Location: Melbourne Posted 10/05/24 05:11 AM Share Posted 10/05/24 05:11 AM "absolute" pressure will be atmospheric (14.7psi) added to your boost created by the turbo (18psi, you said)... that'd be a total of 32.7psi so if it says it's making 35psi then you're 2.3psi over your 18psi, e.g. 20.3psi from the turbo... this might explain the black smoke if it can't get enough fuel at that point and it's running lean... or it might just be that your valve springs are going soft and you're getting valve float in the higher revs, as those symptoms point to valve float: where it "runs rough" for a while even at idle RPM until the valve springs recover from being fatigued with considerably less RPM/pressure. Link to comment Share on other sites More sharing options...
boostjunki New Member 5 Member For: 3m 28d Posted 10/05/24 06:34 AM Author Share Posted 10/05/24 06:34 AM Thanks for your reply. Forgot to mention that the valve springs have been upgraded. Black smoke indicates that is running rich not lean. It only blows black smoke once it starts to run rough so smoke could be a symptom not a cause. The spark plug colour indicates that it's not running rich Link to comment Share on other sites More sharing options...
k31th less WHY; more WOT Site Developer 28,724 Member For: 16y 4m 28d Gender: Male Location: Melbourne Posted 10/05/24 07:17 AM Share Posted 10/05/24 07:17 AM how long ago were the valve springs upgraded? they can go weak over a few years, depending on a few factors. Link to comment Share on other sites More sharing options...
boostjunki New Member 5 Member For: 3m 28d Posted 10/05/24 08:47 AM Author Share Posted 10/05/24 08:47 AM Couple of months ago. No change with fault after they were changed. Link to comment Share on other sites More sharing options...
xr6tForMe Donating Members 247 Member For: 11y 2m 9d Gender: Male Posted 29/07/24 12:08 AM Share Posted 29/07/24 12:08 AM How did you go with this? If it is running rich, then I guess it is either tune, or fuel pressure too high? Link to comment Share on other sites More sharing options...
Puffwagon Puff Gold Donating Members 15,609 Member For: 9y 7m 9d Gender: Male Location: South Australia Posted 29/07/24 07:07 AM Share Posted 29/07/24 07:07 AM Stock overboost setting is 2.2psi, could just be doing that and going brrr Link to comment Share on other sites More sharing options...
boostjunki New Member 5 Member For: 3m 28d Posted 07/08/24 10:20 PM Author Share Posted 07/08/24 10:20 PM I have now also replaced fuel pressure reg. MAP sensor, all intake gaskets, pressure tested IC and pipes. Checked waste gate operation. Thanks Puffwagon, I didn't know it was only 2.2psi. I have noticed when replaying data logger on scan tool the waste gate control actuator voltage drops to zero before FP and boost drop off. Does the actuator have the waste gate open or closed at zero volts? Link to comment Share on other sites More sharing options...
Puffwagon Puff Gold Donating Members 15,609 Member For: 9y 7m 9d Gender: Male Location: South Australia Posted 07/08/24 10:49 PM Share Posted 07/08/24 10:49 PM The actuator is pneumatic, it is controlled by air aka boost pressure. The solenoid lets the air through to open the actuator, or stops the air getting through to keep the actuator closed. 25 minutes ago, boostjunki said: the waste gate control actuator voltage drops to zero before FP and boost drop off You answered your own question. Something to check is any splits or cracks in both the line connected to the boost solenoid. Apart from that, you'll need to take it back to the tuner and get them to have a look at it for you. Link to comment Share on other sites More sharing options...
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