q: parallel MBC -- boost lag & tuning strategy
03-27-2005, 04:07 PM
#1
AudiWorld Senior Member
Thread Starter
Join Date: Sep 2004
Posts: 1,166
Likes: 0
Received 0 Likes
on
0 Posts
q: parallel MBC -- boost lag & tuning strategy
i seem to have more boost lag since i've installed the MBC in parallel. i had the impression that the boost cut would be sudden; but now that i think about it, if there's a spring inside, it'll release boost before the max level.
anyone experience this? i STFA and the only relevant post i found was <a href="https://forums.audiworld.com/s4/msgs/1528972.phtml">this</a> by VonK.
also, what should my tuning strategy be for the cut off point? max boost differs for every gear.
anyone experience this? i STFA and the only relevant post i found was <a href="https://forums.audiworld.com/s4/msgs/1528972.phtml">this</a> by VonK.
also, what should my tuning strategy be for the cut off point? max boost differs for every gear.
03-27-2005, 04:42 PM
#2
Elder Member
Join Date: Jan 2004
Posts: 30,248
Likes: 0
Received 0 Likes
on
0 Posts
Boost should hit just as quickly with the MBC in parallel and even quicker with MBC only.
As for tuning it, I usually use 3rd gear and sometimes 2nd.
Log block 003 and see what the throttle position is doing if you think there is throttle cut. With the parallel setup, you can't boost above requested unless you have a TCD....you can only limit boost below requested. That should not induce throttle cut, nor should it result in slower ramp up.
Log block 003 and see what the throttle position is doing if you think there is throttle cut. With the parallel setup, you can't boost above requested unless you have a TCD....you can only limit boost below requested. That should not induce throttle cut, nor should it result in slower ramp up.
03-27-2005, 06:07 PM
#3
AudiWorld Senior Member
Thread Starter
Join Date: Sep 2004
Posts: 1,166
Likes: 0
Received 0 Likes
on
0 Posts
just came back from logging..
003 looks fine. no TC. T% stays at 100% like before.
i got a few codes now. can't search now because search pukes.
17862 - Exhaust Gas Temp Sensor 1 (G235): Short to Ground
P1454 - 35-10 - - - Intermittent
17963 - Charge Pressure: Maximum Limit Exceeded
P1555 - 35-10 - - - Intermittent
16487 - Mass Air Flow Sensor (G70): Signal too High
P0103 - 35-10 - - - Intermittent
the thing is, in 3rd boost won't go over 13psi. but in 6th it goes up to 16psi. so i set the MBC to 15psi.
here are graphs of similar boost levels in 6th gear:
(there is about .3sec between each point)
<b>without mbc:</b>
<img src="http://bagodoosh.home.comcast.net/s4/115_nom.gif">
<b>with mbc:</b>
<img src="http://bagodoosh.home.comcast.net/s4/115_mbc.gif">
maybe i should set it to 16 or 17.
i got a few codes now. can't search now because search pukes.
17862 - Exhaust Gas Temp Sensor 1 (G235): Short to Ground
P1454 - 35-10 - - - Intermittent
17963 - Charge Pressure: Maximum Limit Exceeded
P1555 - 35-10 - - - Intermittent
16487 - Mass Air Flow Sensor (G70): Signal too High
P0103 - 35-10 - - - Intermittent
the thing is, in 3rd boost won't go over 13psi. but in 6th it goes up to 16psi. so i set the MBC to 15psi.
here are graphs of similar boost levels in 6th gear:
(there is about .3sec between each point)
<b>without mbc:</b>
<img src="http://bagodoosh.home.comcast.net/s4/115_nom.gif">
<b>with mbc:</b>
<img src="http://bagodoosh.home.comcast.net/s4/115_mbc.gif">
maybe i should set it to 16 or 17.
03-27-2005, 06:10 PM
#4
Elder Member
Join Date: Jan 2004
Posts: 30,248
Likes: 0
Received 0 Likes
on
0 Posts
Definitely turn the boost up to 16 or 17. How long has it been since you checked codes?
They are all intermittent so I'd say clear them. If they come back, then you know you need to do something.
03-27-2005, 06:55 PM
#7
AudiWorld Super User
Join Date: Nov 2003
Posts: 5,885
Likes: 0
Received 0 Likes
on
0 Posts
it does look like you might be getting more lag w/ MBC. but you should plot vs. time and log more
log more runs and take an average for both to be sure.
you could plot before and after on the same plot, as averages to do a really good comparison.
but it's easy for me to sit here and type that. :-)
you could plot before and after on the same plot, as averages to do a really good comparison.
but it's easy for me to sit here and type that. :-)
Trending Topics
03-28-2005, 08:19 AM
#10
AudiWorld Super User
Join Date: Nov 2000
Posts: 4,219
Likes: 0
Received 0 Likes
on
0 Posts
Here's my problem: --->
AFAIK, spec boost is an ECU calculated value, that is unaffected by actual boost as long as actual boost doesn't exceed the (internally mapped) max allowable boost. In your first pic, spec doesn't spike while boost builds up, but it does so in the second pic. While the MBC appears to slow boost buildup somewhat, spec spikes instantly. So the slower buildup can't cause a feedback. What's telling the ECU that you installed an MBC?