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Old 11-17-2007, 03:22 PM   #9
mickeyd2005
Scooby Newbie
 
Member#: 122595
Join Date: Aug 2006
Chapter/Region: NWIC
Vehicle:
2005 LGT Wagon
ABP

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Quote:
Originally Posted by joe-6STi View Post
The way i understood It - you'll never really hit target boost in 1st - rare in 2nd - always in 3rd if things are set up right. Certainly in 4th you should be hitting bosot targets.

Someone said (think it was mickeyd2005) that a .5 psi overboost was alright. In logging my stocker I would set that much at times, prior to ever having touched the ECU.
What do you mean? Did you look at the graphs? I can hit target boost in 2nd gear. It's just at a later rpm. The lower load due to the taller gearing results in a faster acceleration of the engine. Spool is affected but you can still hit target boost.

In fact, I can hit target boost in 1st gear if I start my log from a low enough rpm. It's kind of hard to tell though because you only get a handful of data points and the rpm and boost are out of synch. I can tell I hit target boost because my TD proportional is close to zero. In the graph I plotted above, there was some kind of delay in TD integral in 1st gear. I datalogged again later at a very low rpm start (1200 rpm) and the delay in TD integral went away. Not sure what happened but 1st gear datalogs are pretty meaningless...

IMHO, I try not to overboost, at all, but I have to live with some. My opinion is 0.5 psi overboost for a stage 1 or 2 car. The problem with overboost is that TD integral winds down and this causes a dip in boost after overboost. It's better to shoot for a "soft landing."

The way to set up a "soft landing" is to control TD integral. Datalog TD integral and TD proportional and you will learn to control it.

I also datalog a 4th gear transient (start at a high rpm) to make sure that I don't overboost in 4th gear when I punch it at an already high rpm. TD proportional needs to be set up correctly here.
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