How boost leaks can KILL your power - and how to test for them
Jun 6, 2005, 09:20 PM
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How boost leaks can KILL your power - and how to test for them
Guys - its funny how 90% of the time when I run across a customer who is complaining of low dyno numbers or slow 1/4 mile times a BOOST LEAK is the culprit.
By way of example - my car was making some decent power when I put my new GT40R turbo kit on - see this dyno sheet
This was on low boost and with my 1,000 injectors maxed out at over 100% duty cycle - I had to take the car to the Atlantic City SEMA show later the same day and head to Texas for tuning
When I came back I put some 1,600 cc injectors in and turned up the boost, oddly the car stared making less whp as I turned up the boost. The WHP was down at least 60 whp even at 10 more psi of boost.
Then when we turned down the boost the power was going down even further despite my best tuning efforts
A compression test showed the engine was 100% and the plugs looked good
Time for a BOOST LEAK TEST which is critical to have in your tool bag as a diagostic test for Evos with low power
The way it works is you weld a flat piece of metal to the end of a metal tube. You put a tire air valve in the end and attach it to your turbo inlet. By adding compressed air with a pressure gauge you can see how much boost your system is holding and quickly listen for any leaks.
Sure enough it seemed that my Magnus intake manifolod was not up to high boost and cracked down the seam
Photo attached
Remember - if your evo is not holding a steady boost to red line and if your boost is falling down more than 2 psi from peak to red line take a close look at vacum hoses, intercooler pipes and turbo flanges for leaks which can kill your power
By way of example - my car was making some decent power when I put my new GT40R turbo kit on - see this dyno sheet
This was on low boost and with my 1,000 injectors maxed out at over 100% duty cycle - I had to take the car to the Atlantic City SEMA show later the same day and head to Texas for tuning
When I came back I put some 1,600 cc injectors in and turned up the boost, oddly the car stared making less whp as I turned up the boost. The WHP was down at least 60 whp even at 10 more psi of boost.
Then when we turned down the boost the power was going down even further despite my best tuning efforts
A compression test showed the engine was 100% and the plugs looked good
Time for a BOOST LEAK TEST which is critical to have in your tool bag as a diagostic test for Evos with low power
The way it works is you weld a flat piece of metal to the end of a metal tube. You put a tire air valve in the end and attach it to your turbo inlet. By adding compressed air with a pressure gauge you can see how much boost your system is holding and quickly listen for any leaks.
Sure enough it seemed that my Magnus intake manifolod was not up to high boost and cracked down the seam
Photo attached
Remember - if your evo is not holding a steady boost to red line and if your boost is falling down more than 2 psi from peak to red line take a close look at vacum hoses, intercooler pipes and turbo flanges for leaks which can kill your power
Last edited by DynoFlash; Jun 6, 2005 at 09:24 PM.
Jun 6, 2005, 10:43 PM
#3
I wish it was that easy. I spent all day by first putting together my own homemade pressure tester, then by testing the system, but I still can't figure out what's happening. At 1.6 bar on the pressure tester, I had no leaks, yet when I go drive, I blow open a hole in every gear at high rpm, which lets all the boost out. All I did was a simple Hallman Pro install with it set to near-stock boost, yet I have a phantom leak that has only gotten worse after 5 separate attempts to re-install/re-tighten everything.
I have no idea how to find it at this point after having found no leaks at 1.6bar using a pressure tester.
I have no idea how to find it at this point after having found no leaks at 1.6bar using a pressure tester.
Jun 6, 2005, 10:45 PM
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Originally Posted by Warrtalon
I wish it was that easy. I spent all day by first putting together my own homemade pressure tester, then by testing the system, but I still can't figure out what's happening. At 1.6 bar on the pressure tester, I had no leaks, yet when I go drive, I blow open a hole in every gear at high rpm, which lets all the boost out. All I did was a simple Hallman Pro install with it set to near-stock boost, yet I have a phantom leak that has only gotten worse after 5 separate attempts to re-install/re-tighten everything.
I have no idea how to find it at this point after having found no leaks at 1.6bar using a pressure tester.
I have no idea how to find it at this point after having found no leaks at 1.6bar using a pressure tester.
Jun 6, 2005, 10:56 PM
#5
Originally Posted by Soon2BEVO
What do you mean you blow a hole in every gear at high rpm? If your system is holding 1.6bar you dont have a boost leak!
Yes, you would think that if my system could hold 1.6bar using the pressure tester that it would be able to handle 1.4bar while driving, but that's not the case, and I don't know why. The only difference in setup between the pressure tester and when driving is that the BOV-to-intake port is plugged when doing the test, but when driving, it is connected to the hole in the intake-to-turbo hose (stock intake/bov). It could be this connection and/or the BOV being overpowered, but it never did this before the MBC (stock boost 1.4bar), although the boost would taper at higher rpm...hmm.
Jun 6, 2005, 11:03 PM
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Originally Posted by Warrtalon
By "blowing a hole," I mean that I am at full boost until about 6500, then the leak occurs, I hear a whistling noise, and my boost falls off completely. I can then shift to the next gear while keeping it at WOT, and the whistle continues the entire time while I am at .1-.2 bar at most. If I go WOT and hit full boost but let off before 6k or so, the leak doesn't occur. It's the strangest thing I've ever encountered.
Yes, you would think that if my system could hold 1.6bar using the pressure tester that it would be able to handle 1.4bar while driving, but that's not the case, and I don't know why. The only difference in setup between the pressure tester and when driving is that the BOV-to-intake port is plugged when doing the test, but when driving, it is connected to the hole in the intake-to-turbo hose (stock intake/bov). It could be this connection and/or the BOV being overpowered, but it never did this before the MBC (stock boost 1.4bar), although the boost would taper at higher rpm...hmm.
Yes, you would think that if my system could hold 1.6bar using the pressure tester that it would be able to handle 1.4bar while driving, but that's not the case, and I don't know why. The only difference in setup between the pressure tester and when driving is that the BOV-to-intake port is plugged when doing the test, but when driving, it is connected to the hole in the intake-to-turbo hose (stock intake/bov). It could be this connection and/or the BOV being overpowered, but it never did this before the MBC (stock boost 1.4bar), although the boost would taper at higher rpm...hmm.
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Jun 6, 2005, 11:12 PM
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Originally Posted by Warrtalon
By "blowing a hole," I mean that I am at full boost until about 6500, then the leak occurs, I hear a whistling noise, and my boost falls off completely. I can then shift to the next gear while keeping it at WOT, and the whistle continues the entire time while I am at .1-.2 bar at most. If I go WOT and hit full boost but let off before 6k or so, the leak doesn't occur. It's the strangest thing I've ever encountered.
Yes, you would think that if my system could hold 1.6bar using the pressure tester that it would be able to handle 1.4bar while driving, but that's not the case, and I don't know why. The only difference in setup between the pressure tester and when driving is that the BOV-to-intake port is plugged when doing the test, but when driving, it is connected to the hole in the intake-to-turbo hose (stock intake/bov). It could be this connection and/or the BOV being overpowered, but it never did this before the MBC (stock boost 1.4bar), although the boost would taper at higher rpm...hmm.
Yes, you would think that if my system could hold 1.6bar using the pressure tester that it would be able to handle 1.4bar while driving, but that's not the case, and I don't know why. The only difference in setup between the pressure tester and when driving is that the BOV-to-intake port is plugged when doing the test, but when driving, it is connected to the hole in the intake-to-turbo hose (stock intake/bov). It could be this connection and/or the BOV being overpowered, but it never did this before the MBC (stock boost 1.4bar), although the boost would taper at higher rpm...hmm.
Jun 6, 2005, 11:13 PM
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Originally Posted by EVOMIZ
thats the 2nd manfold that has a crack in it.
is this common?
is this common?
Mine lasted for a long time till this happend - but it happened right away when I tried to go over 40 psi
Jun 6, 2005, 11:15 PM
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Originally Posted by EVOMIZ
thats the 2nd manfold that has a crack in it.
is this common?
is this common?
Jun 6, 2005, 11:23 PM
#11
Originally Posted by DynoFlash
Whats your mod list
Nothing major, and the first 3 mods were working like a charm with no leaks and no problems whatsoever until I installed the Hallman. At first, I was peaking and holding 1.4bar or so in 3rd gear with only a slight taper near redline (assuming the stock bov was leaking it off). I could run full boost at WOT to redline in gears 1-4 without the bad leak ever happening.
I then went to the drag strip, and on my first launch, PSHHHHHHHHHHHHHH, the leak occurred. At first, it would only happen when there was immediate full boost like on a launch or after a really fast 1-2 shift near redline. Now, after re-installing EVERYTHING 5 times, the leak occurs in every gear at 6k rpm, so it's much worse now. I assumed that I had made a mistake in reassembling everything, but now that I've done the pressure test and ruled out all the IC connections and vaccuum lines, I am clueless. My only guess now is its either the Hallman somehow messing up (doubtful) or the stock BOV is sticking open, if that's possible.
Jun 6, 2005, 11:35 PM
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Originally Posted by bigjhoney
Anyone have any good links on how to make a tester, all the ones I found so far are dead links.
Simple and effective
Jun 6, 2005, 11:38 PM
#14
Originally Posted by Addicted4Life
