Boost dropping off post throttle: Boost leak, ECU correction or ? - logs attached - Rennlist - Porsche Discussion Forums

Go Back  Rennlist - Porsche Discussion Forums > Turbo Technical Discussion Areas > 997 Turbo Forum
Reload this Page > Boost dropping off post throttle: Boost leak, ECU correction or ? - logs attached
Notices

Boost dropping off post throttle: Boost leak, ECU correction or ? - logs attached

Reply

Old 03-18-2017, 02:39 AM
  #1
vman932
Addict
Rennlist Member
Thread Starter
 
vman932's Avatar
 
Join Date: Nov 2014
Posts: 91
Default Boost dropping off post throttle: Boost leak, ECU correction or ? - logs attached

After some recent mods, I noticed by manifold boost pressure is not reaching target levels as the rpms climb. I found some very interesting info in this thread https://rennlist.com/forums/997-turb...s-it-safe.html about the ECU effectively capping power. My car is reaching target boost levels pre throttle, but post throttle the pressure is bleeding off. I performed a boost leak test from turbo outlet to turbo outlet and everything was holding pressure up to 22.5 psi. The logs back this up showing pre throttle boost pressure at or above target levels, only after the throttle and at upper rpms does the post throttle pressure drop.
The turbos are capable of producing 20+ psi and the manifold is capable of containing it as witnessed by the log showing between 19 and 21 psi from ~3800 to ~4000 rpm as the pull starts.
Setup:
2008 997 turbo cab 6MT
stock airbox
stock turbos
Cobb Stage 2 93 octane OTS tune
do88 inlets, ICs, and y-pipe
FVD headers and catted exhaust
Max IAT 77* F
0 knock retard

Full log here:
http://www.datazap.me/u/vman932/data...18-24-25-28-35

zoomed log here:
http://www.datazap.me/u/vman932/data...8&zoom=143-187

What say those wiser than I? Boost leak in the manifold? Weak/leaking diverter valves? ECU shenanigans?
vman932 is offline  
Reply With Quote
Old 03-18-2017, 04:16 AM
  #2
Kevin
Addict
Rennlist Member


Rennlist
Site Sponsor

 
Kevin's Avatar
 
Join Date: Jun 2001
Location: Northwest
Posts: 8,082
Default

I took a brief look at your logs..

Basically the ECU is calling/requesting boost at pressure levels less than 1.2 bars. The turbochargers are meeting the target levels. As you shift into 4th, 5th and 6th gear the turbochargers will struggle to meet higher requested boost levels. On this platform we don't have a constant pressure level requested thru the RPM rev range. The requested boost does vary between 1.05 to 1.2 bars..

Another point.. If the ECU load targets are met with timing.. There is ZERO reason why the ECU will overboost and supply pressure levels over the requested pressure.

Check your DV's and maybe another intake pressure test....

Last edited by Kevin; 03-18-2017 at 04:33 AM.
Kevin is offline  
Reply With Quote
Old 03-18-2017, 10:19 AM
  #3
A418t81
Addict
Rennlist Member
 
A418t81's Avatar
 
Join Date: Feb 2014
Location: Montgomery, Al
Posts: 275
Default

Post throttle body MAP value is modeled, not real. There is no MAP sensor in the intake mani like a 997.2TT. The only sensor is the pre-throttlebody one. What is funny is the deviation grows even larger if you pop a larger plenum in there, but at the end of the day this value is of little relevance.
A418t81 is offline  
Reply With Quote
 

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
cstyles
997 Turbo Forum
1
07-07-2017 03:55 PM
saabin
997 Turbo Forum
19
06-11-2017 08:43 AM
Voith
944 Turbo and Turbo-S Forum
9
04-27-2016 11:53 AM
powdrhound
996 Turbo Forum
11
04-26-2016 06:03 PM
saabin
997 Turbo Forum
17
04-13-2016 05:17 PM

Thread Tools
Search this Thread
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump


All times are GMT -3. The time now is 08:03 AM.


Copyright ę 1998 - 2017 Rennlist.com
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: