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Old 01-07-2014, 09:11 PM   #1
mattyj
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Default Stage 1 91 HWG log …. Underboost still?

Hey all. Just got my AP today & flashed to Stage 1 91. Seems to be under boosting but maybe should be expected with where i live? 4500' & about 30* outside right now.

First log showed only 13.9 peak boost, so i re-flashed to Stage 1 91 HWG. definitely helped with peak boost now at 14.45psi.

https://docs.google.com/spreadsheet/...lE&usp=sharing

The map boost description from Cobb says 15psi peak tapering to 13psi by redline. I'm only seeing around 11.7psi by 6500rpm.

Thoughts?

Thanks in advance.
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Old 01-07-2014, 11:28 PM   #2
snoopy8818
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Actually your right on target. Your TD boost error is within +/- 1 lb of target boost. The maps notes are based on sea level targets. There are tables that adjust boost target and WG duty cycle based on barometric pressure and air intake temp to prevent pushing the turbo out of its efficiency range. So with these table kicking in you are right on target. In fact I would run the NWG map this way if the temp drops more or you are in a taller gear you do not over boost. The map notes and targets are all based on sea level... everything is then compensated from that point. Even on the stock tune it is. If not ur car would be a hand grenade. I am one state over in NV. So if I go out to CA at sea level my boost will be higher ... go up to the mountains it is lower. No real performance difference though.
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Old 01-07-2014, 11:54 PM   #3
mattyj
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Quote:
Originally Posted by snoopy8818 View Post
Actually your right on target. Your TD boost error is within +/- 1 lb of target boost. The maps notes are based on sea level targets. There are tables that adjust boost target and WG duty cycle based on barometric pressure and air intake temp to prevent pushing the turbo out of its efficiency range. So with these table kicking in you are right on target. In fact I would run the NWG map this way if the temp drops more or you are in a taller gear you do not over boost. The map notes and targets are all based on sea level... everything is then compensated from that point. Even on the stock tune it is. If not ur car would be a hand grenade. I am one state over in NV. So if I go out to CA at sea level my boost will be higher ... go up to the mountains it is lower. No real performance difference though.
Thanks a lot for your input. Makes sense!

Cheers!
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Old 01-08-2014, 12:54 PM   #4
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snoopy8818 is spot on. Here is a blurb that we are starting to put into all the map notes. I don't think this is in the 09+ WRX map notes yet, but I'll make sure it gets in there soon.

- Chris

---------

Monitoring Boost Levels:

The best way to determine if you are hitting target boost is to watch the TD Boost Error parameter. This parameter is your target boost (including altitude and temperature compensations) minus your actual boost (negative values mean you are over the target by the amount while positive values mean you are under). Ideally you want this value to be between 0 and 1.0 at wide open throttle (WOT), but -1.0 to 1.0 is acceptable assuming that you don’t have any significant knock corrections. Overboosting is more likely to occur in higher gears and with colder outside temperatures, so be sure to verify boost levels during these conditions.

High Altitude:

A quick note for those of you that live at higher altitudes. It is common for turbocharged cars at higher altitudes to run less boost pressure due to lower air pressure and air density. Your turbocharger has to work harder to compress a less dense air mass compared to the same turbocharger at sea level. This must be factored in when determining if your turbocharger is running the proper amount of boost pressure and not being pushed beyond its efficiency range.

Example: If you live in Denver at 5280 ft and are trying to run a peak boost pressure of 15 psi, your turbocharger has to work the equivalent of making ~17.5 psi at sea level.

There are barometric compensations within the factory ECU that lower boost targets as you climb in altitude in an effort to keep the turbocharger in its optimal range. The COBB performance maps utilize these compensations and therefore, it is perfectly normal for the final boost target to be lower than what is listed for your map.
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Old 01-08-2014, 01:04 PM   #5
mattyj
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Quote:
Originally Posted by Cobb Tuning View Post
snoopy8818 is spot on. Here is a blurb that we are starting to put into all the map notes. I don't think this is in the 09+ WRX map notes yet, but I'll make sure it gets in there soon.

- Chris

---------

Monitoring Boost Levels:

The best way to determine if you are hitting target boost is to watch the TD Boost Error parameter. This parameter is your target boost (including altitude and temperature compensations) minus your actual boost (negative values mean you are over the target by the amount while positive values mean you are under). Ideally you want this value to be between 0 and 1.0 at wide open throttle (WOT), but -1.0 to 1.0 is acceptable assuming that you don’t have any significant knock corrections. Overboosting is more likely to occur in higher gears and with colder outside temperatures, so be sure to verify boost levels during these conditions.

High Altitude:

A quick note for those of you that live at higher altitudes. It is common for turbocharged cars at higher altitudes to run less boost pressure due to lower air pressure and air density. Your turbocharger has to work harder to compress a less dense air mass compared to the same turbocharger at sea level. This must be factored in when determining if your turbocharger is running the proper amount of boost pressure and not being pushed beyond its efficiency range.

Example: If you live in Denver at 5280 ft and are trying to run a peak boost pressure of 15 psi, your turbocharger has to work the equivalent of making ~17.5 psi at sea level.

There are barometric compensations within the factory ECU that lower boost targets as you climb in altitude in an effort to keep the turbocharger in its optimal range. The COBB performance maps utilize these compensations and therefore, it is perfectly normal for the final boost target to be lower than what is listed for your map.
Great. Thanks for your response Chris.

I'll carry out some more logs & take note of the TD boost error. If I'm continuing to be near the -1.0, as I am currently near 3200rpm, I'll go back to the std stage 1 91 map.

Maybe I was mistaken, but the car did feel like it accelerated better/stronger with the HWG map, so if possible I'd like to run that. I'll just keep an eye on knock correction.

Cheers!
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Old 01-08-2014, 08:36 PM   #6
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You might want to monitor Injector Duty Cycle. Actually you definitely want to monitor that regardless. But in general with the colder weather the injectors might starting hitting 100% or over when you get towards the higher RPM range. More boost will mean more fuel as well.
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Old 01-08-2014, 11:52 PM   #7
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Quote:
Originally Posted by snoopy8818 View Post
You might want to monitor Injector Duty Cycle. Actually you definitely want to monitor that regardless. But in general with the colder weather the injectors might starting hitting 100% or over when you get towards the higher RPM range. More boost will mean more fuel as well.
Thanks again for the advice. I'll start to monitor IDC now in my logs.

I took your advice & flashed back to Stage 1 NWG after carrying out a few more logs today & seeing TD Boost Error readings in the -1.2 to -1.6 range from about 3200 - 3800 rpm.

Slowly learning!
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Old 01-09-2014, 12:00 AM   #8
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Yeah you don't want to see a TD negative error of 1.6 unless its right after you take your foot off the gas. Do a solid pull in 3rd gear on a flat road if you can from 2500 up to redline and see if that shows in the log.
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Old 01-09-2014, 01:20 AM   #9
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I was adjusting my boost baro compensation today up at 9500'.

Normal relative boost, at 5000' is 18psi. Up at 9500', I was getting 14psi.

The biggest factor in that 14psi was the IAT waste gate duty compensation table. My iat was in the low 30's-the table was pulling something like 40% of the normal waste gate duty cycle.

Lowered it down to about 10%(in the 30 column) and I was back up to 18psi. (had to adjust a few other tables too).

Super stoked to have real time, altitude compensated boost levels. For me, thats the holy grail of boost control.

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Old 01-09-2014, 01:25 AM   #10
mattyj
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Quote:
Originally Posted by snoopy8818 View Post
Yeah you don't want to see a TD negative error of 1.6 unless its right after you take your foot off the gas. Do a solid pull in 3rd gear on a flat road if you can from 2500 up to redline and see if that shows in the log.
sorry, should of been more clear in my last post…

I did a couple of WOT 3rd gear 2500rpm to redline logs & found that the TD error was -1.2 to -1.6 as revs climbed through 3200 -3800 rpm, it then continually lowered to around -0.5 to -0.2 at redline.

Im back on the NWG map now, so i'll try for more logs soon ….. damn snow rolled in tonight so i'll see if i have some dry road conditions tomorrow.

Cheers!
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Old 01-09-2014, 01:32 AM   #11
mattyj
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Quote:
Originally Posted by point78 View Post
I was adjusting my boost baro compensation today up at 9500'.

Normal relative boost, at 5000' is 18psi. Up at 9500', I was getting 14psi.

The biggest factor in that 14psi was the IAT waste gate duty compensation table. My iat was in the low 30's-the table was pulling something like 40% of the normal waste gate duty cycle.

Lowered it down to about 10%(in the 30 column) and I was back up to 18psi. (had to adjust a few other tables too).

Super stoked to have real time, altitude compensated boost levels. For me, thats the holy grail of boost control.

Correct me if I'm wrong,…. but doesn't making those changes to achieve your lower elevation target boost (18psi @ 5000') at high elevation (9000'), create a massive addition load on the turbo due to the less dense air its trying compress?
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Old 01-09-2014, 01:46 AM   #12
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Yep, that's why I put a turbo with a taller compressor map in, so I can run higher pressure ratios.
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Old 01-09-2014, 08:02 AM   #13
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Yeah if you go with an after market turbo its safe to do. The stock one even if you pushed it as hard as you wanted would never be able to hold sea level boost targets at altitude in most cases. You will see your WGDC maxed out and no change in boost after a given point.
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Old 01-09-2014, 08:06 AM   #14
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That -1.6 when the boost comes on would concern me... I just like to be on the conservative side. If your not seeing any knock associated with it then I guess its not as big of a deal. I just like to be on the conservative side because I did loose a ring land on a previous engine.

Quote:
Originally Posted by mattyj View Post
sorry, should of been more clear in my last post…

I did a couple of WOT 3rd gear 2500rpm to redline logs & found that the TD error was -1.2 to -1.6 as revs climbed through 3200 -3800 rpm, it then continually lowered to around -0.5 to -0.2 at redline.

Im back on the NWG map now, so i'll try for more logs soon ….. damn snow rolled in tonight so i'll see if i have some dry road conditions tomorrow.

Cheers!
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Old 01-09-2014, 10:29 AM   #15
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Quote:
Originally Posted by point78 View Post
Yep, that's why I put a turbo with a taller compressor map in, so I can run higher pressure ratios.
Ok gotcha! Thanks for the information.
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Old 01-09-2014, 10:31 AM   #16
mattyj
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Quote:
Originally Posted by snoopy8818 View Post
That -1.6 when the boost comes on would concern me... I just like to be on the conservative side. If your not seeing any knock associated with it then I guess its not as big of a deal. I just like to be on the conservative side because I did loose a ring land on a previous engine.
For sure, I'm taking your words of wisdom. I'll take conservative over an expensive rebuild any day!
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