Boost Leak vs. Load
May 2, 2011, 02:38 PM
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Boost Leak vs. Load
I'm positive I have a boost leak somewhere, I can hear it and I'm boosting 1-2 psi less. My question is will Load in Evoscan be less with a boost leak. And will peak load come later?
I am seeing less load but peak load is actually a bit sooner than usual.
This is confusing to me.
I am seeing less load but peak load is actually a bit sooner than usual.
This is confusing to me.
May 2, 2011, 03:05 PM
#2
It increases load until the total drop in air mass is greater than the amount contributed to leak. So it might go as you said, spike early then tapers, but it realy depends on if your boost is controlled pneumaticall, by ecu, or whatever.
A leaking DV will not raise load.
A leaking DV will not raise load.
May 3, 2011, 05:04 PM
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I recently deleted my EGR system and the block off plate is leaking. So i know that's what's going on. I'm simply confused by what the logs are showing me as opposed to what I'd expect to see with a boost leak.
I just thought it was weird that, when logging, peak load was hitting 200-300 rpms sooner. I guess maybe I'm making a connection between boost leak=slower spool=later peak boost=later peak load.
Are these things not usually connected?
Last edited by motocooney; May 3, 2011 at 05:19 PM.
May 6, 2011, 09:52 AM
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It increases load until the total drop in air mass is greater than the amount contributed to leak. So it might go as you said, spike early then tapers, but it realy depends on if your boost is controlled pneumaticall, by ecu, or whatever.
A leaking DV will not raise load.
A leaking DV will not raise load.
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May 6, 2011, 10:01 AM
#8
Would you mind explaining this? I thought that load was determined by MAF and temp. Then wouldn't the load be determined before the leak and therefore be the same either way? Or are you saying that airflow at the MAF will change even though the leak is further down the line?
On a recirculated setup it would not since air would be recycled into the turbo and the maf wouldn't see an increase.
A leak to the outside simply means more air through the maf since the turbo is making up the difference in pressure with added flow.
May 6, 2011, 04:45 PM
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To clarify if you had a VTA setup it would increase load because more air flow would go through the maf.
On a recirculated setup it would not since air would be recycled into the turbo and the maf wouldn't see an increase.
A leak to the outside simply means more air through the maf since the turbo is making up the difference in pressure with added flow.
On a recirculated setup it would not since air would be recycled into the turbo and the maf wouldn't see an increase.
A leak to the outside simply means more air through the maf since the turbo is making up the difference in pressure with added flow.
Also, I understand that the turbo will have to work harder for the same result with a boost leak....but .....how will that result in more air through the Maf?
Like if you suck through a straw and get X amount of vacuum, then put a little hole in the straw, you'll have to suck harder to get the same amount. But does that mean that there will be more airflow at the end of the straw (like the MAF end of the intake)?
Last edited by motocooney; May 6, 2011 at 04:47 PM.
May 6, 2011, 04:51 PM
#10
That first part doesn't make any sense to me. If the only difference between a VTA and recirc setup occurs on throttle lift when the valve opens and either dumps or throws it back into the intake, why would the Maf see more air flow and higher load with a VTA setup?
Also, I understand that the turbo will have to work harder for the same result with a boost leak....but .....how will that result in more air through the Maf?
Like if you suck through a straw and get X amount of vacuum, then put a little hole in the straw, you'll have to suck harder to get the same amount. But does that mean that there will be more airflow at the end of the straw (like the MAF end of the intake)?
Also, I understand that the turbo will have to work harder for the same result with a boost leak....but .....how will that result in more air through the Maf?
Like if you suck through a straw and get X amount of vacuum, then put a little hole in the straw, you'll have to suck harder to get the same amount. But does that mean that there will be more airflow at the end of the straw (like the MAF end of the intake)?
The second is very simple since the turbo is "working harder" its moving more air. Air which has to go through the maf. The maf is pre turbo and thus sucking harder means more air is drawn through it when there is a post turbo leak.
Jul 17, 2011, 07:59 PM
#12
Are you logging boost? That just looks like a big spike and then some error correction gets rid of it. Load is airflow in hz divided by rpm * 852 (more or less), so if it was a leak it would hold high.
What boost controller and what boost level? If I didnt know better I'd say that was somewhere around a 27-28psi spike if its on a stock turbo.
What boost controller and what boost level? If I didnt know better I'd say that was somewhere around a 27-28psi spike if its on a stock turbo.
Jul 17, 2011, 08:26 PM
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Hmm. Well, I have a hallman mbc set to hit 23 max (set by looking at AEM gauge), and I have never seen higher than 23 - which I rarely see its usually 21-22 max. I was not looking at my boost gauge during that pull, but I'd be very surprised if it was that high. Car feels down on power.
Car is stock turbo, with turboback. I can't log boost because I am running the accessport stage 2 right now. I am waiting to tune until I sort the issues out. (loss of power) Thought it was a boost leak because AFR is a little low by about .5 across the board, but I wasn't sure if the increase in air was a symptom of boost leak or something else.
Car is stock turbo, with turboback. I can't log boost because I am running the accessport stage 2 right now. I am waiting to tune until I sort the issues out. (loss of power) Thought it was a boost leak because AFR is a little low by about .5 across the board, but I wasn't sure if the increase in air was a symptom of boost leak or something else.
Last edited by eb66; Jul 17, 2011 at 08:33 PM.
Jul 21, 2011, 08:37 PM
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Is there any other reason that I would have high airflow like that? It consistently has high load spikes, and airflow is at the max 1593 at about 5300rpm all the way up -too high for 22psi. But, I have done multiple boost leak tests, fixed leaks, and nothing else is leaking, and I have all tbolt clamps that are very tight - and all confirmed with soapy water boost leak test. I am also getting consistent 1-2 counts of knock on most pulls. Part of the problem with low power is that I need to adjust the timing, but I should not be getting knock with negative timing, and airflow should not be this high.
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