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Old 01-04-2013, 07:04 PM   #1
jamesashe
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Join Date: Nov 2012
Vehicle:
2005 WRX Wagon

Default Reducing boost in stage 1 91 Octane OTS map, other programming changes needed?

Iím a neophyte to this, Iíve worked on cars for a long time, but this is my first turbo vehicle and my first attempt to change the engine behavior with ECU changes.

The thing I donít like about the map, is the way the torque hits hard and tapers off. Iím coming from NA cars and I donít like the way the engine feels in the top half. I think that I would be happier if I reduced the boost to have a flatter torque curve (after threshold).

Can I just reduce the boost target in the map? Is there enough information in the map to allow the ECU to handle a lower boost without trouble? Or is the ECU constantly going to be doing something undesirable (running rich, etc)?

Thanks for the help.
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Old 01-05-2013, 08:06 AM   #2
Cobb Tuning
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Quote:
Originally Posted by jamesashe View Post
I’m a neophyte to this, I’ve worked on cars for a long time, but this is my first turbo vehicle and my first attempt to change the engine behavior with ECU changes.

The thing I don’t like about the map, is the way the torque hits hard and tapers off. I’m coming from NA cars and I don’t like the way the engine feels in the top half. I think that I would be happier if I reduced the boost to have a flatter torque curve (after threshold).

Can I just reduce the boost target in the map? Is there enough information in the map to allow the ECU to handle a lower boost without trouble? Or is the ECU constantly going to be doing something undesirable (running rich, etc)?

Thanks for the help.
First thing to check would be to make sure that you do not currently already have a boost spike or are overboosting overall. You can do this via data logging (see video below). If you are overboosting, then you can download the low wastegate (LWG) version of your map from the maps section at cobbtuning.com (use AccessPORT Manager software to transfer map from computer to AccessPORT and then reflash to car). Even if you are not overboosting, you could try the LWG map anyway to see if it reduces that initial surge of power to more of your liking.

If that does not work for you, you can certainly reduce boost in the boost targets tables. You will also likely need to reduce the wastegate duty in the wastegate duty low and high table (keeping the same spread between the two), otherwise you may overboost (relative to your new target). Boost tuning can be very time consuming - you will need to make small changes at a time, data log to verify, tweak and repeat.


Bill
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Old 01-07-2013, 02:42 AM   #3
jamesashe
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Thank you for the prompt reply. I'll log the boost over the next couple days, and see what it looks like.

I did turn on the live monitoring for boost for a few drives, immediately after flashing the map. It did not report a number higher than what the map notes said to expect.

Do you happen to have a sample dyno graph for the LWG vs regular map at stage 1? Or just the shape of the torque curve on the LWG map?
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Old 01-07-2013, 10:09 AM   #4
Cobb Tuning
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Originally Posted by jamesashe View Post
Thank you for the prompt reply. I'll log the boost over the next couple days, and see what it looks like.

I did turn on the live monitoring for boost for a few drives, immediately after flashing the map. It did not report a number higher than what the map notes said to expect.

Do you happen to have a sample dyno graph for the LWG vs regular map at stage 1? Or just the shape of the torque curve on the LWG map?
You'll want to compare boost levels to the boost map in 3rd gear wide open throttle (WOT) run from around 2500 RPM on up (if you can do so safely). That is a good run to get a data log in to see how boost control (and everything else) is doing.

With normal use (i.e. using one or the other when it is necessary) of the LWG and HWG map, there is basically no power difference because you are simply using these maps to achieve the level of boost that you are supposed to. Using the LWG map when you don't need to will likely lower boost. That is not a normal scenario that we would check via dyno. Hard to say exactly what performance hit you will see - that will depend on to many variables to guess. But, you can use the road dyno function to compare if you like (use the same flat section of road with both tests with no to little wind).

Bill
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Old 01-08-2013, 03:01 PM   #5
jamesashe
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I ran a couple WOT tests in second, and one in 3rd for as long as was legal. With exception of one data point, it looks like the car is consistently under the boost target. In general the peak is 14.5, which is consistent with what I remembered from the last time I used the live data monitoring.

I loaded the LWG map on the AP when I was looking at the data. I'll load that tonight or tomorrow and give it a shot.
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Old 01-09-2013, 09:27 AM   #6
Cobb Tuning
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Originally Posted by jamesashe View Post
I ran a couple WOT tests in second, and one in 3rd for as long as was legal. With exception of one data point, it looks like the car is consistently under the boost target. In general the peak is 14.5, which is consistent with what I remembered from the last time I used the live data monitoring.

I loaded the LWG map on the AP when I was looking at the data. I'll load that tonight or tomorrow and give it a shot.
3rd gear is what you want to look at for peak boost (for 5-speed tranny), if you can do so safely. You will likely see a lower peak boost in 1st and 2nd - this is normal and does not indicate you are underboosting unless you also see a more than 1 psi underboost in 3rd.

Bill
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Old 01-09-2013, 07:44 PM   #7
jamesashe
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Alright, I'll go to a different location with a higher speed limit and log again. I'm glad you posted, because my logs were not consistent with what I was expecting.
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Old 01-11-2013, 01:12 PM   #8
jamesashe
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With the third gear pulls the boost ramp consistently has a smaller slope and I lose 1-1.5 psi off peak boost. I'm much happier with the transition at boost threshold now.

Thank you for the help.
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