Wastegate opens early

[PrimeMvr]

As I've posted recently, I have my baby tuned up very nicely with the addition of an MSD 6AL-2. The smoother power curve has me noticing that the wastegate is actually opening early, around .6 bar on my MSD MAP sensor and NHS gauge, which is plumbed off the brake booster. The stock boost gauge, driven off the stock sensor on the IC, is pegged when the WG opens, so I don't think it's a weak spring and the WG was rebuilt within a few thousand miles.

My theory is since the WG is plumbed off the IC, it's seeing higher pressure than is actually in the manifold. On sustained WOT, the MAP catches up, but it takes several seconds, often reaching my prefered 6k shift point first.

The question for the gurus: Is this normal, or is there a different strategy that can be taken for plumbing the WG? The hose to it is too large to hook up to any post-butterfly sources.

My engine was so weak under 3k before working out the timing, that I never noticed this before. I basically had no power or full power.

Thanks,
Steve

[mooney265]

Why do you think it's "not" the spring? My WG is plummed off the intercooler, too - and, I can get any boost I want [manual boost gauge] - immediately...

I have a 0.8BAR spring and can turn my MBC all the way down and get 0.8BAR at 2,600RPM thru 6K+...

[drmatera]

There is a cool video on YouTube of the boost gauge of a 935 race car as it screamed around the race track. The gauge had two dials, one sensed at the turbo outlet and one at the intake manifold. As the boost came on the one dial would shoot up while the other lagged behind slightly. They both reached the same max boost but there was a delay in response from the intake referenced dial.