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Old 02-01-2006, 08:24 PM   #1
rsr14
Scooby Newbie
 
Member#: 77245
Join Date: Dec 2004
Default Poor boost response question

A little background before I ask my question.
I have a 2004 WRX. At one point, I had the following modifications.
Invidia catless uppipe
VF39 turbo
Invidia catless downpipe
STi catback
Sti intercooler
Accessport
Since I still had stock injectors, I used the Cobb stage 2 map. I drove the car conservatively, knowing the stock injectors could not keep up with the turbo.
With this set-up, boost response was unbelievable. It spooled at least as quick as it did with the stock turbo and stock uppipe with cobb stage 2 map.

Then, I installed Sti pink injectors and loaded the VF34 map. Now my boost response it MUCH worse. Worse to the point, that my wife noticed it imediately. I emailed cobb, and pretty much the only advice I got was to get rid of the intercooler (which is obviously not the problem) or get a custom tune. This is understandable, as OTS maps have to be conservative, but I know the turbo can build boost faster. It seems the wastegate duty cycle with this map is way too conservative.

The simplest solution I've come to is a MBC, which is not recommended. I've spent hours searching on various forums about mbc's but I can not get an answer as to why they are so adamantly frowned on. Most of the time people try to use an MBC as an alternative to an AP, but I have an AP and still want the controller. I understand that running too much boost is bad, so I don't intend on running more than cobb target boost. Then I read about PTFB, but that seems to only apply to the stock ECU again. I haven't heard of how the AP map handles boost at part throttle, and it seems to me in any case the MAF and O2 could correct.

So, I guess my questions is...
How can I get better boost response from my set-up?
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Old 02-03-2006, 03:17 PM   #2
rsr14
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Member#: 77245
Join Date: Dec 2004
Default

Someone has to know why MBC's are condemned like they are.
Is PTFB really a problem?
As long as the car is in closed-loop, I don't see where there would be a problem. Anyone know if/when Cobb's maps run OL/CL?
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Old 02-04-2006, 04:34 PM   #3
rsr14
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Default

to the top
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Old 02-04-2006, 07:16 PM   #4
hondaeater69
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Location: a pillow.
Default

Quote:
Originally Posted by rsr14
The simplest solution I've come to is a MBC, which is not recommended. I've spent hours searching on various forums about mbc's but I can not get an answer as to why they are so adamantly frowned on. Most of the time people try to use an MBC as an alternative to an AP, but I have an AP and still want the controller. I understand that running too much boost is bad, so I don't intend on running more than cobb target boost. Then I read about PTFB, but that seems to only apply to the stock ECU again. I haven't heard of how the AP map handles boost at part throttle, and it seems to me in any case the MAF and O2 could correct.

So, I guess my questions is...
How can I get better boost response from my set-up?
1.) get a protune. this is my first suggestion. Your tuner will be able to get quicker spool, plus get more power out of your setup. Win-win

2.) get a mbc. PTFB is real. One of the problems is that MAFv is not one of the cl/ol triggers within the stock ecu's logic. When you install a MBC, you bypass the stock BCS, therefore the stock ECU cannot limit or cut off boost. So if you get PTFB, or over boost and knock and it's a bad event, your stock ecu can no longer pull boost (which it can and will do). It can only pull timing.

I would suggest if you go for route 2, DL the free logging software and learn about tuning and some of the important parameters to watch. Dynamic Advance and Knock Correction are among them.

Most frown on MBC's because if you don't have the knowledge to use it properly, you can blow your ish up in short order.
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Old 02-06-2006, 09:07 AM   #5
rsr14
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Member#: 77245
Join Date: Dec 2004
Default

Thank you!
I'm looking into getting a professional tune, but that won't be for another few months at least, as I do not have any options locally.

Is the logging software used through the AccessPort? I was not aware it had that capability.
I have adequate knowlege of tuning, but I do not know what parameters the Cobb map uses under part-throttle and spool-up.

I was considering welding in another bung and hooking up our LM1, but the traffic around here isn't very freindly towards that, and it won't tell me anything about knock or ignition retard.

Thanks for the input. Sounds like getting the logging software is the first step.
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Old 02-06-2006, 12:51 PM   #6
Veck
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Join Date: Feb 2002
Vehicle:
2002 WRX
WRB

Default

Before you change anything I'd get some logging software so you can properly document where you are today. The logging will help you understand why you may be having issues with spool up.

If you feel comfotable doing some basic tuning you can always go the street tuner route. I've got the AP/ST combination on my WRX and like the results i've been able to get so far. With ST you can change the CL/OL transitions to make sure you dont have a bad PTFB situation. I know i had to make some changes to get rid of that condition when I installed my AVCR.
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