Boost Targets and Colder Weather - Page 2 - BMW 3-Series (E90 E92) Forum

JOe335i · 10-10-2008, 06:42 PM

Reading on another forum.
The JB3 will reduce PSI in hotter weather and of course high IAT
and it will increase boost in lower cooler temps.

it seems the STOCK car does the opposite.

M.A.C.K. · 10-10-2008, 06:47 PM

Quote:

Originally Posted by JOe335i

Reading on another forum.
The JB3 will reduce PSI in hotter weather and of course high IAT
and it will increase boost in lower cooler temps.

it seems the STOCK car does the opposite.

Its a safety feature of the JB3 pretty much.........

Sparkplug · 10-11-2008, 01:42 AM

I'm running Dinan and I've definitely seen a drop in boost with this cold (near freezing) weather we're having. When it was hot out (+85) I was getting almost 15 psi and now it's droped to 10. The car still pulls as hard (if not harder) though. I'll time a 1/4 mile with my FX-1 and see how it compares.

Dr_Dirt · 10-11-2008, 04:18 AM

Quote:

Originally Posted by Sparkplug

I'm running Dinan and I've definitely seen a drop in boost with this cold (near freezing) weather we're having. When it was hot out (+85) I was getting almost 15 psi and now it's droped to 10. The car still pulls as hard (if not harder) though. I'll time a 1/4 mile with my FX-1 and see how it compares.

Thats a huge drop, looking forward to you results.

cn555ic · 10-11-2008, 09:06 AM

Quote:

Originally Posted by Sparkplug

I'm running Dinan and I've definitely seen a drop in boost with this cold (near freezing) weather we're having. When it was hot out (+85) I was getting almost 15 psi and now it's droped to 10. The car still pulls as hard (if not harder) though. I'll time a 1/4 mile with my FX-1 and see how it compares.

yeah thats a significant drop in boost...It seems like too much of a drop. I can see maybe 2 psi drop, but 5 psi drop doesn't sound like it should be normal or effective tune.

Sparkplug · 10-12-2008, 12:34 AM

Sorry guys, on further testing, the boost is more like 11.5 to 12 at 38 F which is a drop of about 2 psi. I did a 1/4 mile run and got the same I usually get ie 12.8. It would be nice to keep the same boost to take advantage of the cooler air. On the other hand, at these temperatures, the snow is coming and more HP will just equal more wheelspin.

midlife · 10-12-2008, 07:43 PM

Quote:

Originally Posted by Sparkplug

I'm running Dinan and I've definitely seen a drop in boost with this cold (near freezing) weather we're having. When it was hot out (+85) I was getting almost 15 psi and now it's droped to 10. The car still pulls as hard (if not harder) though. I'll time a 1/4 mile with my FX-1 and see how it compares.

like most of you, my car pulls much harder when it is cold in the evenings.
i am also at v high altitude (27% less oxygen at 8,000 feet).

to get the same dense, cold nite air - but in the daytime - would spraying water (not nitrious) into the intercooler make the air going into the intake plenum that much denser??

note that if this could work for me, it should also work for you guys at sea level.

thanks

Tuned335i · 10-13-2008, 02:12 AM

Why is everyone so surprised that boost goes down when the temps go down? You do understand that the air is much more dense at low temps, which explains why you see the same power at lower temps and lower indicated boost psi, right? Do you really want the cylinder pressures that 15psi will produce at air densities that exist at 50 degrees F?

Actually, a lot of you guys will probably say "HELL YEAH!!!"

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

10-10-2008, 06:42 PM	#23
JOe335i Lieutenant Drives: R32-08STI-e92335i Join Date: Feb 2007 Location: AUSTRIA Posts: 525 iTrader: (0)	Reading on another forum. The JB3 will reduce PSI in hotter weather and of course high IAT and it will increase boost in lower cooler temps. it seems the STOCK car does the opposite.

10-11-2008, 01:42 AM	#25
Sparkplug Badge Whore Drives: Dinan 335xi Join Date: Dec 2006 Location: GSA Posts: 856 iTrader: (1)	I'm running Dinan and I've definitely seen a drop in boost with this cold (near freezing) weather we're having. When it was hot out (+85) I was getting almost 15 psi and now it's droped to 10. The car still pulls as hard (if not harder) though. I'll time a 1/4 mile with my FX-1 and see how it compares.

10-12-2008, 12:34 AM	#28
Sparkplug Badge Whore Drives: Dinan 335xi Join Date: Dec 2006 Location: GSA Posts: 856 iTrader: (1)	Sorry guys, on further testing, the boost is more like 11.5 to 12 at 38 F which is a drop of about 2 psi. I did a 1/4 mile run and got the same I usually get ie 12.8. It would be nice to keep the same boost to take advantage of the cooler air. On the other hand, at these temperatures, the snow is coming and more HP will just equal more wheelspin.

10-13-2008, 02:12 AM	#30
Tuned335i Major Drives: E92 335i Join Date: Jun 2007 Location: World of Torque Posts: 1,310 iTrader: (0)	Why is everyone so surprised that boost goes down when the temps go down? You do understand that the air is much more dense at low temps, which explains why you see the same power at lower temps and lower indicated boost psi, right? Do you really want the cylinder pressures that 15psi will produce at air densities that exist at 50 degrees F? Actually, a lot of you guys will probably say "HELL YEAH!!!"