Boost Leak? Dyno graph example?
Thread Starter
Drifting
Joined: Mar 2003
Posts: 1,533
Likes: 171
From: Oklahoma City OK
Boost Leak? Dyno graph example?
Does anyone have a dyno graph example of a boost leak on a supercharged car? Can you post it?
Here is the back story...
I think I had a boost leak at the cylinder heads/intake manifold (bad/flat as pancakes manifold gaskets). Car is way down on power and had a weird spike at the beginning of dyno runs. The 2 Bar SD sensor was seeing 9-10 psi @ 6600 at the back of the intake manifold. Is it possible that the SD sensor and electric boost gauge would see the proper amount of pressure, but the cylinders wouldn't if the intake manifold gaskets were bad? Cylinders check out as good... so thats not the problem.
To give you an idea what my graph looks like I drew one up. Don't have the real graph with me.
The red line is the rough drawn example of mine.
Here is the back story...
I think I had a boost leak at the cylinder heads/intake manifold (bad/flat as pancakes manifold gaskets). Car is way down on power and had a weird spike at the beginning of dyno runs. The 2 Bar SD sensor was seeing 9-10 psi @ 6600 at the back of the intake manifold. Is it possible that the SD sensor and electric boost gauge would see the proper amount of pressure, but the cylinders wouldn't if the intake manifold gaskets were bad? Cylinders check out as good... so thats not the problem.
To give you an idea what my graph looks like I drew one up. Don't have the real graph with me.
The red line is the rough drawn example of mine.
Le Mans Master
Joined: Feb 2007
Posts: 6,674
Likes: 57
From: Mt Pleasant, TN
Melting Slicks
Joined: Jul 2005
Posts: 2,586
Likes: 2
From: Bardstown Kentucky
That spike is kind of weird... but my car shows the same thing on HP logs at the track.
What head unit are you running? I dont really see a boost leak but the way it drops off kind of makes it look like you are running out of head unit. Is this a stock cube engine? For the most part the boost should be linear on the rise as the RPM goes up.
What head unit are you running? I dont really see a boost leak but the way it drops off kind of makes it look like you are running out of head unit. Is this a stock cube engine? For the most part the boost should be linear on the rise as the RPM goes up.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
I've found small leaks in cars and was amazed at how much boost they lost from it,but at the same time, I've seen entire hoses come loose and hanging 1" away from the other end and still make 5psi.
OP, I would recommend you cap and hose clamp your supercharger intake and then pressurize the entire system through the brake booster line with a regulated amount of pressure while listening and looking for leaks.
What system do you have? Do you have the Vortech maxflow bypass valve in your system by chance? If so, I would start by pulling that off and trying to blow through it. Ditch it and get a better one regardless of the result. They are nothing but headaches.
OP, I would recommend you cap and hose clamp your supercharger intake and then pressurize the entire system through the brake booster line with a regulated amount of pressure while listening and looking for leaks.
What system do you have? Do you have the Vortech maxflow bypass valve in your system by chance? If so, I would start by pulling that off and trying to blow through it. Ditch it and get a better one regardless of the result. They are nothing but headaches.
Thread Starter
Drifting
Joined: Mar 2003
Posts: 1,533
Likes: 171
From: Oklahoma City OK
I will see if I can get the real dyno graph this week. The one I posted is just one I had drawn on for an example of what mine sorta looks like.
I am running a new A&A kit with a V3 Si head unit on a z06 with long tubes, off road x pipe, and stock cat back.
I am running a new A&A kit with a V3 Si head unit on a z06 with long tubes, off road x pipe, and stock cat back.
Last edited by Chrisrokc; Nov 1, 2011 at 03:26 PM.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
Who tuned the car? What did they say about it?
Does the dyno sheet show a boost log? I've seen clogged cats murder power too.
Based on your drawing, you show less than 500RWHP. Is that a correct figure? Something's wrong and if you showed 9-10psi at the intake, the answer to your question is "no" it is not possible to have 10psi at the intake manifold and lose it on the way to the cylinders. Clogged cats or valve float or tuning issues if it's making that low of a power figure.
Does the dyno sheet show a boost log? I've seen clogged cats murder power too.
Based on your drawing, you show less than 500RWHP. Is that a correct figure? Something's wrong and if you showed 9-10psi at the intake, the answer to your question is "no" it is not possible to have 10psi at the intake manifold and lose it on the way to the cylinders. Clogged cats or valve float or tuning issues if it's making that low of a power figure.
Thread Starter
Drifting
Joined: Mar 2003
Posts: 1,533
Likes: 171
From: Oklahoma City OK
Who tuned the car? What did they say about it?
Does the dyno sheet show a boost log? I've seen clogged cats murder power too.
Based on your drawing, you show less than 500RWHP. Is that a correct figure? Something's wrong and if you showed 9-10psi at the intake, the answer to your question is "no" it is not possible to have 10psi at the intake manifold and lose it on the way to the cylinders. Clogged cats or valve float or tuning issues if it's making that low of a power figure.
Does the dyno sheet show a boost log? I've seen clogged cats murder power too.
Based on your drawing, you show less than 500RWHP. Is that a correct figure? Something's wrong and if you showed 9-10psi at the intake, the answer to your question is "no" it is not possible to have 10psi at the intake manifold and lose it on the way to the cylinders. Clogged cats or valve float or tuning issues if it's making that low of a power figure.
I will get the actual dyno sheet tomorrow. I do not believe it has the boost log on it. It was making 490 ish at 20 degrees of timing (it was taking it w/ meth). After, we backed off the timing to around 13 because it seemed high, the car made less hp. We also removed the high flow cats, didn't solve the problem.
Last edited by Chrisrokc; Nov 1, 2011 at 09:10 PM.
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Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
My tuner is located here in OKC. He is pretty good, has lots of other cars under his belt including a few other A&A cars. He is an Official A&A Reseller. One posts on this forum from time to time. He thinks it could be valve float possibly, so we are thinking about some 918 valve springs. Does valve float happen at 3000rpms? I just want to make sure I have covered all the bases we might not have thought of.
I will get the actual dyno sheet tomorrow. I do not believe it has the boost log on it. It was making 490 ish at 20 degrees of timing (it was taking it w/ meth). After, we backed off the timing to around 13 because it seemed high, the car made less hp. We also removed the high flow cats, didn't solve the problem.
I will get the actual dyno sheet tomorrow. I do not believe it has the boost log on it. It was making 490 ish at 20 degrees of timing (it was taking it w/ meth). After, we backed off the timing to around 13 because it seemed high, the car made less hp. We also removed the high flow cats, didn't solve the problem.
I prefer double springs on a boosted motor. Patriot or PRC's are most popular and considering how many Patriot springs I know are out there, failures as a percentage are next to nil. I would love to see your logs if your tuner is willing to send them. I might be able to quickly diagnose the problem with the tune and logs.
Is your tuners name Bret? If so, tell him he has the coolest name there is!
Thread Starter
Drifting
Joined: Mar 2003
Posts: 1,533
Likes: 171
From: Oklahoma City OK
Do you know if you have the older Maxflo valve? I never heard on that one.
I prefer double springs on a boosted motor. Patriot or PRC's are most popular and considering how many Patriot springs I know are out there, failures as a percentage are next to nil. I would love to see your logs if your tuner is willing to send them. I might be able to quickly diagnose the problem with the tune and logs.
Is your tuners name Bret? If so, tell him he has the coolest name there is!
I prefer double springs on a boosted motor. Patriot or PRC's are most popular and considering how many Patriot springs I know are out there, failures as a percentage are next to nil. I would love to see your logs if your tuner is willing to send them. I might be able to quickly diagnose the problem with the tune and logs.
Is your tuners name Bret? If so, tell him he has the coolest name there is!
Thread Starter
Drifting
Joined: Mar 2003
Posts: 1,533
Likes: 171
From: Oklahoma City OK
There was a couple of things that may have stopped the car from making the power, but really it was about the tune. I did the following....
Replaced the rubber o-ring gaskets on the intake manifold. There was a leak there early on.
Removed the catalytic convertors. (fixed any air blockage, if it existed)
Replaced the stock valve springs with dual value springs. (fixed any valve float, if it existed)
Installed a Wideband AFR Sensor and Gauge.
Bought HP Tuners.
Took the car to BLOWNBLUEZ06 (Bret) for a proper tune.
The car drove like crap around town and the first SD tune from my local turner was sub par. Learned that through talking to people on here. After realizing that I took the car to the best IMO.
A cam, methanol, and smaller pulley later it is making north of 660rwhp. I just recently put a larger intake on the blower and adjusted the tune for the additional air. Still running strong and healthy after 5 years of fun!
Replaced the rubber o-ring gaskets on the intake manifold. There was a leak there early on.
Removed the catalytic convertors. (fixed any air blockage, if it existed)
Replaced the stock valve springs with dual value springs. (fixed any valve float, if it existed)
Installed a Wideband AFR Sensor and Gauge.
Bought HP Tuners.
Took the car to BLOWNBLUEZ06 (Bret) for a proper tune.
The car drove like crap around town and the first SD tune from my local turner was sub par. Learned that through talking to people on here. After realizing that I took the car to the best IMO.
A cam, methanol, and smaller pulley later it is making north of 660rwhp. I just recently put a larger intake on the blower and adjusted the tune for the additional air. Still running strong and healthy after 5 years of fun!
Last edited by Chrisrokc; Jun 19, 2016 at 11:20 AM.
