Has anyone with a 4 valve had valve float issues on their turbo car?
I have 04 cobra heads with stock springs and stock cams, a Master Power 76mm with a .96 a/r turbine housing, 38mm wastegate (about 12psi spring), Eboost2 boost controller, stock exhaust manifolds, 3 inch downpipe w/ no cat, no mufflers dumped at the steering rack, Sullivan lower intake, HPP upper intake, stock throttle body, 80lbs injectors, running E85.
On 13psi the car makes about 540hp, and 16psi the car makes 615hp. The power carries all the way to 7,000 rpm. A/F is about 11:8
On 18psi the car made about 650hp on the same day, but the power falls off hard after about 6,000. From 6,000 rpm to almost 7,000 rpm, the car would drop from 650hp to 395hp. Its weird, the power would climb like normal until it hits about 6k rpm, and then just fall off.
This starts happening when we take it past 18psi.
The boost would never fall off after 6k rpm when the power falls, air/fuel is still straight while the power is falling off, timing isnt doing anything weird. A few people have suspected that the turbo was maxed out, but its only at about 650hp at 18 psi when the power starts falling off. And the IATs are only about 115-130 degrees.
There is a VERY SLIGHT sputtering sound when the power starts falling off at 18psi. You can barely hear it. Sometimes I dont hear it.
My tuner, Manny Alavarez (HPP Racing), told me that it might be the valve springs. He had a problem similar to mine on a turbo LS1 that he was tuning. The car carried the power all the way through the rpms on lower boost. When he tried to turn it up, the power would fall off hard at higher rpms, and it would have a slight sputtering sound. They put in a set of stiffer valve springs, put it back on the dyno, and it was able to carry the power all the way though the RPM range.
I have seen plenty of turbo 03-04 Cobras with stock valve springs making over 800hp without any problems.
This motor has also seen about 20psi of boost when I had a Whipple 2.3 about 2 years ago, and it carried the power all the way to 7000 rpm.
Let me know what you guys think.
Thanks for reading my novel
I have 04 cobra heads with stock springs and stock cams, a Master Power 76mm with a .96 a/r turbine housing, 38mm wastegate (about 12psi spring), Eboost2 boost controller, stock exhaust manifolds, 3 inch downpipe w/ no cat, no mufflers dumped at the steering rack, Sullivan lower intake, HPP upper intake, stock throttle body, 80lbs injectors, running E85.
On 13psi the car makes about 540hp, and 16psi the car makes 615hp. The power carries all the way to 7,000 rpm. A/F is about 11:8
On 18psi the car made about 650hp on the same day, but the power falls off hard after about 6,000. From 6,000 rpm to almost 7,000 rpm, the car would drop from 650hp to 395hp. Its weird, the power would climb like normal until it hits about 6k rpm, and then just fall off.
This starts happening when we take it past 18psi.
The boost would never fall off after 6k rpm when the power falls, air/fuel is still straight while the power is falling off, timing isnt doing anything weird. A few people have suspected that the turbo was maxed out, but its only at about 650hp at 18 psi when the power starts falling off. And the IATs are only about 115-130 degrees.
There is a VERY SLIGHT sputtering sound when the power starts falling off at 18psi. You can barely hear it. Sometimes I dont hear it.
My tuner, Manny Alavarez (HPP Racing), told me that it might be the valve springs. He had a problem similar to mine on a turbo LS1 that he was tuning. The car carried the power all the way through the rpms on lower boost. When he tried to turn it up, the power would fall off hard at higher rpms, and it would have a slight sputtering sound. They put in a set of stiffer valve springs, put it back on the dyno, and it was able to carry the power all the way though the RPM range.
I have seen plenty of turbo 03-04 Cobras with stock valve springs making over 800hp without any problems.
This motor has also seen about 20psi of boost when I had a Whipple 2.3 about 2 years ago, and it carried the power all the way to 7000 rpm.
Let me know what you guys think.
Thanks for reading my novel
