High ambient temps = lower boost ???
This is not for my Miata, it is for my Subaru. So this is a general turbo question on boost control.
I'm tuned for 21psi from gt3076r using a Hallman MBC with the heavy spring in it. Yesterday my outside temp on the dash read 95*F, and I was only hitting 15-16psi max. Tonight when it was cooler out, I tested and was hitting 20-21 like I am supposed to be. Did a couple more pulls on the way home and hit about 19-20 pounds. Why are my boost pressures so low when it is hot out? Shouldn't the ball/spring in the Hallman be reacting at the same boost pressure no matter what the ambient temp is? Maybe there is something to do with air density that has to do with the boost controller responding, but I can't think of it if there is. -Nick |
Anyone have any ideas?
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Most factory cars do this, I believe as a form of knock control. But idk for sure
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Yeah, if your motor is knocking, it is going to lower the boost. More heat means more likely to knock.
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Did you get it figured out? Give us something. If we are going to answer your questions, we like a little feedback.
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I am a subaru / evo / skyline tuner
the ecu in a subaru has temp compensation maps on timing / boost (but that boost wont do anything since the mbc is in place) the scoob has its intake air temp sensor in the MAF so if intake temp is greater than x value - the ecu reduces timing - by reducing timing this may impact your boost - I have seen many cars overboost in lower ambient temps - than when they were tuned - during the heat of the day |
So, it goes off of temperature not knock? I was under the impression that it would retard timing when there was any kind of knock going on.
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it will pull timing based on knock / knock severity as well
what model car is it - let me look in the ecu and post up the images |
also hot air is less dense so the turbo would have to spin up more to get the same ammount of air in there ... just a thought.
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I think I may have figured it out.... my boost gauge is not accurate at all. I also blew the motor, pretty sure its rings or ringland for cylinder 2.... not sure why, but thinking it might be due to overboost since I was unable to accurately monitor my boost levels (boost gauge was reading low and not consistent).
For the sake of figuring out if this is possible and why, I will answer all the questions though.
Originally Posted by J.T.
(Post 258375)
Most factory cars do this, I believe as a form of knock control. But idk for sure
Originally Posted by 3barboost
(Post 258572)
I am a subaru / evo / skyline tuner
the ecu in a subaru has temp compensation maps on timing / boost (but that boost wont do anything since the mbc is in place) the scoob has its intake air temp sensor in the MAF so if intake temp is greater than x value - the ecu reduces timing - by reducing timing this may impact your boost - I have seen many cars overboost in lower ambient temps - than when they were tuned - during the heat of the day The car was also tuned at night, we finished up at about midnight so ambient temps were pretty low.
Originally Posted by 3barboost
(Post 258910)
it will pull timing based on knock / knock severity as well
what model car is it - let me look in the ecu and post up the images
Originally Posted by akaryrye
(Post 259463)
also hot air is less dense so the turbo would have to spin up more to get the same ammount of air in there ... just a thought.
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How the hell did you toast that motor so quickly? You just beat the shit out of on a poor tune?
I had a friend w/ an 05 making 485/485 on a FP Red on a stock motor w/ bolt-ons (3" up pipe, downpipe, headers, etc.)...for like...20k miles or so...toasted the motor when Hydra got pissed at his meth and cut injection @ 29.5lbs of boost. It still made in the 300s with a compression of like 60 in the #4 cylinder. I have a new found respect for that motor. |
You know what is strange, my miata did the "exact same thing". "Exact same thing" being that, once after boosting the car for like 10 minutes of driving/ hot ambient temps. , the boost started to drop.
It was tuned for 12 lbs. , but as the car started to get hotter the boost would drop lower and lower. Eventually it would settle around 8 lbs. which you all know the difference between 12 and 8 lbs. is going to be pretty dramatic, so it really sucked. |
Originally Posted by miatamania
(Post 259514)
How the hell did you toast that motor so quickly? You just beat the shit out of on a poor tune?
I had a friend w/ an 05 making 485/485 on a FP Red on a stock motor w/ bolt-ons (3" up pipe, downpipe, headers, etc.)...for like...20k miles or so...toasted the motor when Hydra got pissed at his meth and cut injection @ 29.5lbs of boost. It still made in the 300s with a compression of like 60 in the #4 cylinder. I have a new found respect for that motor.
Originally Posted by crashnscar
(Post 259492)
I think I may have figured it out.... my boost gauge is not accurate at all. I also blew the motor, pretty sure its rings or ringland for cylinder 2.... not sure why, but thinking it might be due to overboost since I was unable to accurately monitor my boost levels (boost gauge was reading low and not consistent).
Originally Posted by ak47bravo
(Post 260442)
You know what is strange, my miata did the "exact same thing". "Exact same thing" being that, once after boosting the car for like 10 minutes of driving/ hot ambient temps. , the boost started to drop.
It was tuned for 12 lbs. , but as the car started to get hotter the boost would drop lower and lower. Eventually it would settle around 8 lbs. which you all know the difference between 12 and 8 lbs. is going to be pretty dramatic, so it really sucked. |
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