Jump to content
Sign in to follow this  
Akirasoft

2011 GT500 Boost dropping off in higher gears

Recommended Posts

I've been asking around about the following issue and have taken the car to a dealership.

 

In any gear higher than 3rd, even with TC off, I see a significant drop in boost as RPM increases. In 3rd gear the car will be down to 3-5psi (inaccurately measured by stock boost gauge) by redline and in 4th I will be down to zero boost.

 

So far the dealership was not helpful, after a ride along with a master tech he claimed this is simply a function of the calibration of the car.

 

I actually got around to filming this today. It is about 70 degrees outside with 43% humidity.

 

video below:

 

 

thanks!

Share this post


Link to post
Share on other sites

that was definitely with the pedal to the floor.

 

 

Video sucked I guess then. It definitely seems way down on power then. Check for air leaks in the intake tract from the filter to the throttle body. How does it idle?

 

That is not "the calibration" doing that. Either the guage is shot or you bleeding off boost / slipping belt. Does the blower whine stay strong till the top?

Edited by ChrisSD

Share this post


Link to post
Share on other sites

Video sucked I guess then. It definitely seems way down on power then. Check for air leaks in the intake tract from the filter to the throttle body. How does it idle?

 

That is not "the calibration" doing that. Either the guage is shot or you bleeding off boost / slipping belt. Does the blower whine stay strong till the top?

 

 

idles fine, blower wine does seem to correspond to gauge reading but I'll be honest, the blower wine is not as pronounced on this car as it was on my buddy's 2008.

Share this post


Link to post
Share on other sites

Video sucked I guess then. It definitely seems way down on power then. Check for air leaks in the intake tract from the filter to the throttle body. How does it idle?

 

That is not "the calibration" doing that. Either the guage is shot or you bleeding off boost / slipping belt. Does the blower whine stay strong till the top?

 

 

*removing double post*

Edited by Akirasoft

Share this post


Link to post
Share on other sites

idles fine, blower wine does seem to correspond to gauge reading but I'll be honest, the blower wine is not as pronounced on this car as it was on my buddy's 2008.

 

 

The 08 is louder. Car is not made as well, less sound deadening, and the 10+ have a noise baffle in the intake tract. Try tightening all the fittings from the air filter clamp to the TB.

Share this post


Link to post
Share on other sites

idles fine, blower wine does seem to correspond to gauge reading but I'll be honest, the blower wine is not as pronounced on this car as it was on my buddy's 2008.

 

 

 

unless you have installed a resonator eliminator you will never match the sound of the 2008.

They installed a "muffler" in the CAI of 2010 + vehicles to reduce that terrible S/C whine..lol..

Share this post


Link to post
Share on other sites

unless you have installed a resonator eliminator you will never match the sound of the 2008.

They installed a "muffler" in the CAI of 2010 + vehicles to reduce that terrible S/C whine..lol..

 

 

I always thought it was funny that the blower was like 10x louder than the exhaust in the 08. My 2011 is the opposite, when I'm not LOSING BOOST! :(

Share this post


Link to post
Share on other sites

In any gear higher than 3rd, even with TC off, I see a significant drop in boost as RPM increases. In 3rd gear the car will be down to 3-5psi (inaccurately measured by stock boost gauge) by redline and in 4th I will be down to zero boost.

 

So far the dealership was not helpful, after a ride along with a master tech he claimed this is simply a function of the calibration of the car.

 

I actually got around to filming this today. It is about 70 degrees outside with 43% humidity.

 

 

 

 

That is NOT right.

 

Check your by-pass valve for operation.

 

And that is NOT a "functin" of the calibration. Whoever told you that is either a liar or stupid (give him his choice).

 

By-pass valves are notorious for this type of problem so I'd check it first.

 

Make sure it is all the way CLOSED when it should be and that the diaphram holds vacuum (compress the plunger, hold your thumb over the hose and see if the plunger stays retracted).

 

 

HTH,

Phill

Share this post


Link to post
Share on other sites

That is NOT right.

 

Check your by-pass valve for operation.

 

And that is NOT a "functin" of the calibration. Whoever told you that is either a liar or stupid (give him his choice).

 

By-pass valves are notorious for this type of problem so I'd check it first.

 

Make sure it is all the way CLOSED when it should be and that the diaphram holds vacuum (compress the plunger, hold your thumb over the hose and see if the plunger stays retracted).

 

 

HTH,

Phill

 

 

does a BPV function any different in a GT500 vs a turbo car? I have previously had two turbo 4 cylinders, in those they remain closed until opened by the solenoid. They remain closed if there is any kind of failure in the line leading to it leading to overboost situations (ask me how I know!) Does it function the same way here? In which case I would think that if I have some sort of actuation issue I would possibly see overboost?

 

I've been reading more and it I've heard quite a bit of things are done with the throttle body in these cars since the PCM has so much control in a drive by wire setup. Could that relate somehow?

Share this post


Link to post
Share on other sites

That is definitely not normal, like someone else stated...the BPV would be my initial thought of the culprit.

 

 

 

That is my first thought. Second thought would be a slipping blower belt.

 

Make sure your belt is TIGHT. They *will* slip with higher RPM (more load).

 

 

Phill

Share this post


Link to post
Share on other sites

That is my first thought. Second thought would be a slipping blower belt.

 

Make sure your belt is TIGHT. They *will* slip with higher RPM (more load).

 

 

Phill

 

 

If a belt is slipping would there be any visual indications such as the grooves or belt surface taking on a different appearance?

Share this post


Link to post
Share on other sites

If a belt is slipping would there be any visual indications such as the grooves or belt surface taking on a different appearance?

 

 

I've been told on other forums if the belt was slipping there would be visible belt debris under the hood (of which i have none.) That being said, the belt seems tight to me but I can move it a bit by hand just deflecting in one of the longer spans. I have no point of comparison there to see if it is truly tight "enough", but the lack of belt debris makes me think a slipping belt is unlikely.

 

to add some more fuel to the fire, I purchased an xcal3 to do datalogging (which happened to come with a john lund tune.)

 

application of the tune introduced the issue to 2nd gear as well.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

×
×
  • Create New...