DaveB 20 Report post Posted April 22, 2015 Why would my turbo run more boost when it's cold and wet? Share this post Link to post Share on other sites
KevinA 695 Report post Posted April 22, 2015 Air density Share this post Link to post Share on other sites
DaveB 20 Report post Posted April 22, 2015 Ummmmm... You may need to expand on that!! Share this post Link to post Share on other sites
Lee 82 Report post Posted April 22, 2015 It shouldn't - how much more boost are we talking? Do you have an electronic boost controller or is boost controlled just by wastegate spring / manual boost controller? Share this post Link to post Share on other sites
KevinA 695 Report post Posted April 22, 2015 A turbo engine will respond and mildly overboost in damp and cool conditions, this is quite usual. The air density changes and in a crude description the explosion in your cylinder is more aggressive. Share this post Link to post Share on other sites
Lee 82 Report post Posted April 22, 2015 Density changes but pressure should remain constant Share this post Link to post Share on other sites
Keethos 842 Report post Posted April 22, 2015 Even with NA cars, you can feel the car is a lot more eager when it's cold and damp compared to a dry hot day. Share this post Link to post Share on other sites
Lee 82 Report post Posted April 22, 2015 ^ Yep, thats to do with the density of the air though, not the pressure. Daveb specifically mentioned more boost, which makes me assume he has a way of measuring it. The wastegate is what controls the boost, and doesnt really care about the density of the air it is 'boosting'. If the car is driving at high altitude, the turbo just spins faster (as wastegate doesnt open as early) to achieve the set boost pressure, whether thats just the spring in the wastegate or by EBC it doesnt really matter. At lower altitudes because the air is denser it requires less work from the turbo to reach the set boost level, the turbo spins slower. So density shouldnt effect boost pressure. Unless the turbo is running flat out the above should be true. Share this post Link to post Share on other sites
DaveB 20 Report post Posted April 23, 2015 Have a boost gauge which records boost pressure, now it's warmer it's running .3 bar less Share this post Link to post Share on other sites
Lauren 2259 Report post Posted April 23, 2015 I think you'll need to give a bit more detail on the car and all that as what you are saying does not make sense. Boost pressure normally goes up when the inlet temperatures get hot, but produces less power as the air is heated. Share this post Link to post Share on other sites
rob275 1817 Report post Posted April 23, 2015 Well cooler air is denser so the pressure of that air in any given volume will be higher, but it's negligible in this scenario .3 bar seems a lot. Share this post Link to post Share on other sites
GTB 53 Report post Posted April 23, 2015 My Sprintex is noticeably more powerful on a cold slightly damp evening. The cooler air is denser. We notice this as well at the gliding club. On a hot day the tug plane struggles to get out of the field and over the trees with a glider on tow ! - which is fun. Share this post Link to post Share on other sites
JamesP1991 222 Report post Posted April 23, 2015 You should theoretically be making more power as cooler air is more dense, denser air = a bigger explosion in the combustion process therefore making more power. That is how it is for N/A cars, which is why your car feels faster in cooler conditions, and obviously a turbo car will still be going through that process. However your boost pressure should not be increasing and decreasing depending on how cold the air is, as that is electronically controlled at a set pressure (bar). Cool air will not "give" you more boost, it will only give the car more oxygen to use in the combustion process. Anyone is free to correct me though, not 100% on that. Share this post Link to post Share on other sites
Guest Report post Posted April 23, 2015 I'd just get a new gauge. I'd also check all mypipe/hose fittings if i were you. Share this post Link to post Share on other sites
Lee 82 Report post Posted April 23, 2015 My Sprintex is noticeably more powerful on a cold slightly damp evening. The cooler air is denser. We notice this as well at the gliding club. On a hot day the tug plane struggles to get out of the field and over the trees with a glider on tow ! - which is fun. Boost in sprintex / any other supercharged application is controlled by pulley size, there is nothing in the system to bleed off boost pressure to the 'target' so it possible to see slight changes in supercharged applications. As I said earlier with a turbo the wastegate controls the boost pressure. Dave - have you checked for something as simple as a boost leak? 0.3 bar isnt an insignificant amount of air to lose. Share this post Link to post Share on other sites
nikndel 509 Report post Posted April 23, 2015 Hey GTB are you a sort of Thomas Crown? 1 GTB reacted to this Share this post Link to post Share on other sites
Quixote 35 Report post Posted April 23, 2015 Air is not an ideal gas so PV=nRT does not apply perfectly Best advice, who fitted the turbo and who tuned it? Ask them Without knowing how boost is controlled in what you have fitted, there's no way to really diagnose anything. Share this post Link to post Share on other sites
Jamie_GRMN 177 Report post Posted April 23, 2015 I'm guessing this is on your Forrester (I think?)... Standard or aftermarket boost control? Either or 0.3 bar is a lot to be just climate effected, I'd check all vac lines etc to be sure. Used to have this issue with the GT4's running MBC's/EBC's, set up in summer for 1.1 bar, got colder and the boost could increase to the point of fuel cut @ 1.2... with EBC's this was filtered out by reducing the gain on the control unit (as you are losing boost, if using an EBC increase the gain). All boost control has some sort of compensation in the system to stop it fluctuating during normal use, the temperature affects this compensation... Share this post Link to post Share on other sites
DaveB 20 Report post Posted April 24, 2015 Yes on the forester. Will check the hoses :-( Share this post Link to post Share on other sites
DaveB 20 Report post Posted April 24, 2015 Have an sti gauge but it only records boost, turbo etc all stock. In wet and cold it would over boost Share this post Link to post Share on other sites
Quixote 35 Report post Posted April 24, 2015 For a scooby with an OEM setup, check the T hoses from the charged air to the wastegate actuator and the boost control solenoid. If there's a leak there, it will cause over boosting as this is the boost control mechanism However, doesn't explain why it only happens when cold... 1 DaveB reacted to this Share this post Link to post Share on other sites
Special K 442 Report post Posted April 24, 2015 Needs an ECU controlled map with wastegate sensor. It's not rocket science. Abbey/Fensport have been doing it for years. Spec K Share this post Link to post Share on other sites
DaveB 20 Report post Posted April 25, 2015 Can't see anything loose. Will check again, fill up with tescos finest see. Share this post Link to post Share on other sites
DaveB 20 Report post Posted April 25, 2015 More power Mr Sulu! Share this post Link to post Share on other sites
