Cold AIT's and boost
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Joined: Jul 2009
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From: Northampton/Leeds
Cold AIT's and boost
Hey,
I knew air temp affected boost pressure due to density..but not to this extent!
I was having a load of trouble with my fueling the last week or so, it would be really inconsistent between say 20mins of driving.. i figured it was the IAT's so i did a load of messing around with the compensations and I made improvments but it was still crap. So I started to look into my MAP pressure logs and found it was pinning at 10.9psi at 7500rpm right up to redline (my car usually runs 10psi boost @ redline with AIT's of around 40 degrees celcius in summer) so I immediately ordered a hondata 4bar sensor and found I was actually hitting 14.8psi at redline with 6 degree celcius IAT's! so over a 4psi increase due to the 34ish degree drop in IAT's.
Car's SC'd btw using Rotrex c38 with FMIC
BTW I started coming off the throttle towards the end of the pull due to grip issues.
Dan
I knew air temp affected boost pressure due to density..but not to this extent!
I was having a load of trouble with my fueling the last week or so, it would be really inconsistent between say 20mins of driving.. i figured it was the IAT's so i did a load of messing around with the compensations and I made improvments but it was still crap. So I started to look into my MAP pressure logs and found it was pinning at 10.9psi at 7500rpm right up to redline (my car usually runs 10psi boost @ redline with AIT's of around 40 degrees celcius in summer) so I immediately ordered a hondata 4bar sensor and found I was actually hitting 14.8psi at redline with 6 degree celcius IAT's! so over a 4psi increase due to the 34ish degree drop in IAT's.
Car's SC'd btw using Rotrex c38 with FMIC
BTW I started coming off the throttle towards the end of the pull due to grip issues.
Dan
Joined: Jan 2006
Posts: 20,788
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From: location, location
Surprised you got any grip Dan in this shit weather 
Mine runs a little more boost but to be expected as you say at this time of the year.
How come you were using the stock MAP sensor, IIRC it fluctuates far too much and will probably top out around 10-11PSI.
I bought a greddy 2 bar boost sensor, and put an inline small fuel filter in to dampen the fluctuations and the difference between pre and post filter is a hell of a lot better.
Mine runs a little more boost but to be expected as you say at this time of the year.
How come you were using the stock MAP sensor, IIRC it fluctuates far too much and will probably top out around 10-11PSI.
I bought a greddy 2 bar boost sensor, and put an inline small fuel filter in to dampen the fluctuations and the difference between pre and post filter is a hell of a lot better.
Thread Starter
Registered User
Joined: Jul 2009
Posts: 331
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From: Northampton/Leeds
Surprised you got any grip Dan in this shit weather
Mine runs a little more boost but to be expected as you say at this time of the year.
How come you were using the stock MAP sensor, it fluctuates far too much and will probably top out around 10-11PSI.
I bought a greddy 2 bar boost sensor, and put an inline small fuel filter in and the difference between fluctuates and accuracy is a hell of a lot better.
Mine runs a little more boost but to be expected as you say at this time of the year.
How come you were using the stock MAP sensor, it fluctuates far too much and will probably top out around 10-11PSI.
I bought a greddy 2 bar boost sensor, and put an inline small fuel filter in and the difference between fluctuates and accuracy is a hell of a lot better.
Haha, the grip is pathetic at the moment, it was in 3rd and a dry road.
the DBW stock map sensor readings were quite consistant up untill this cold weather hit. glad I caught it quickly though!
Joined: Oct 2002
Posts: 8,044
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From: South Florida
I use to gain a psi when the wether dropped from 90f to 40f. But not 4 psi. That's nuts. My guess is u were running more boost then u thought on the stock map sensor. What sucks is your gonna have to rescale the tune and retune up top at the very least. R u the tuner?
Joined: Oct 2002
Posts: 8,044
Likes: 6
From: South Florida
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From: Denton, TX
Originally Posted by DFWs2k' timestamp='1328148198' post='21375402
I gain 2-3 psi from 90f to 55f.
Sent using free Tapatalk - Android FTW
Sent using free Tapatalk - Android FTW
My EMS controls the boost solenoid.
Joined: Oct 2002
Posts: 8,044
Likes: 6
From: South Florida
Originally Posted by camuman' timestamp='1328198837' post='21377164
[quote name='DFWs2k' timestamp='1328148198' post='21375402']
I gain 2-3 psi from 90f to 55f.
Sent using free Tapatalk - Android FTW
I gain 2-3 psi from 90f to 55f.
Sent using free Tapatalk - Android FTW
My EMS controls the boost solenoid.
[/quote]
Feed back boost control. I set mine up so it monitors boost and always adjusts to hit my target boost.
Huge shout out to wadzii for taking the time to teach me about it.