Is this Valve Float?
00 C5, 05 CTS-V
Joined: Dec 2005
Posts: 1,031
Likes: 0
From: Ashland Ohio
Check out this dyno graph. I was talking to LV Vette, and in conversation, he asked if I had any crazy dips on my dyno curve at high RPM. When I described what I have, he said that it is probably valve float, and I should go ahead and change my springs. Here is my dyno graph:
After doing some reading, I have to agree with him. I'm guessing I'm do for a spring change.
After doing some reading, I have to agree with him. I'm guessing I'm do for a spring change.
Norm
Le Mans Master
Joined: Oct 2005
Posts: 7,088
Likes: 1,829
From: Metro Detroit Michigan
The valve spring resonance problem usually shows up between 5350 and 5500 rpm.
Belt slip?
Why would the belt slip around 5400 and not slip at higher rpm as boost and belt load increase?
Belt slip?
Why would the belt slip around 5400 and not slip at higher rpm as boost and belt load increase?
Le Mans Master
Joined: Dec 2005
Posts: 8,475
Likes: 332
From: Port Arthur, Texas 77642
Also, how about the HP & TQ lines, they do not cross at 5250. Something strange going on here
Former Vendor
Joined: Feb 2004
Posts: 10,876
Likes: 8
From: Las Vegas NV
St. Jude Donor '06 & '12
Nothing strange.. You gotta look at the graph closer. They ONLY cross at 5250 when the hp and torque scaling is the same. In this case its not. Thats because usually either the HP or torque is far enough apart from the other that it causes the software to make the necessary adjustments on the graph in order to get it to show properly on the screen.
No biggie.
No biggie.
Thread Starter
Racer
Joined: Feb 2005
Posts: 482
Likes: 1
From: Waveland MS
Le Mans Master
Joined: Dec 2005
Posts: 8,475
Likes: 332
From: Port Arthur, Texas 77642
Nothing strange.. You gotta look at the graph closer. They ONLY cross at 5250 when the hp and torque scaling is the same. In this case its not. Thats because usually either the HP or torque is far enough apart from the other that it causes the software to make the necessary adjustments on the graph in order to get it to show properly on the screen.
No biggie.
No biggie.
Thread Starter
Racer
Joined: Feb 2005
Posts: 482
Likes: 1
From: Waveland MS
BTW, to get the correct crossing point, just multiple the crossing RPM point by 500/600 or 5/6, and you will get the same 5250 result. At least mathematically it should.
Le Mans Master
Joined: Dec 2005
Posts: 8,475
Likes: 332
From: Port Arthur, Texas 77642
Yeah, it's just plotting. The scale for HP is max at 600, while the torque scale is 500. It did that because the HP just crossed over the 500 mark, while the torque is just under it.
BTW, to get the correct crossing point, just multiple the crossing RPM point by 500/600 or 5/6, and you will get the same 5250 result. At least mathematically it should.
BTW, to get the correct crossing point, just multiple the crossing RPM point by 500/600 or 5/6, and you will get the same 5250 result. At least mathematically it should.
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St. Jude Donor '12
Burning Brakes
Joined: Aug 2004
Posts: 849
Likes: 1
From: Dallas TX
i just checked my graphs. mine actually only had the dips when i would spray. the n/a run was smooth as silk. i would think if it is resonance it would happen regardless of power level. now, blowing out the kernel, that may be more on track. at least with my graph. i'm thinking the added cylinder pressure of the n2o may have had a role in this. would love to find out once and for all though.
