Please Help

[Paulie2256]

Im guessing because after the thrashing the valve springs become really soft and are having trouble keeping the exhaust valves closed on combustion.

But I may be wrong.

[Benji_vs]

Is this a generic tune?

If so dont use it and get it properly tuned, these tunes which come with the cappa box can cause huge problems, but from what you have described it sounds like a mechanical problem. I agree get the valve springs replaced as the BA's are know to have fairly weak springs.

[Ralph Wiggum]

BA's have weak valve springs to start with, but once you up the boost and dont make changes to exhaust back pressure (ie dump/cat/exhaust) or intake pressure drop (ie free flowing coolers better pipework etc) the back pressure between the turbo and exhaust valve pushes down on the valve. In simply terms if you have a valve spring with a seating pressure of 10psi (in reality its much higher than that) and have 3 psi of back pressure your effective seat pressure is down to 7 psi. If you Hydraulic lifter is able to provide more the 7psi of "lift" it will open the valve slightly or hold it open slightly after its open.

At high revs you have more gas trying too escape, more back pressure, more oil flow to the lifters so all these factor combine to cause the exhaust valves to stay open. the rough running is caused by low compression in the cylinder(s) that have a valve not sealing properly.

Thats the simple version of events. Theres a bit more to it but in brief BA1 springs + Higher Boost = Rough running after a high rpm high boost run (it can also happen lower in the rev range depending on how the boost is ramped up

New valve springs with Higher seat pressure will stop this.

[darkness]

sweet thanks alot guys ill try that and see what happens if it fixes it all good