90GSX-03EVO

iTrader: (27)

No way. A boost controler will take out the stock taper. The taper comes from the OEM boost control solenoid. You can hold 19PSI to redline with no problems. When you start pressing 21PSI and up, you start tapering around redline once again because of the turbo running out of strength to press that hard at that high of a CFM rate.

trinydex

iTrader: (12)

hmm... are you positive of this? because that sounds like great news to me, but i've heard so many different stories from different people. is it really just that the stocker runs outta breath?

90GSX-03EVO

iTrader: (27)

I'm positive that I have installed boost controlers on both of the Evo's that I have owned (2003 GSR and a 2004 RS) and neither had any ECU work done to them at the time and it eliminated the taper.

It's simple turbocharger principles. Look at how the stock layout is. There is a boost control solenoid that tapers the boost. That is it's job. When you remove that, you remove the taper.

The first Evo I had set to run 19.5 PSI with no worries. The second one is now set to 20 PSI, again, with no worries.

Ted B

iTrader: (6)

The turbo will not taper only if the engine can't use enough air (making enough power) to bring it to its limit.

propellerhead

iTrader: (3)

I think there may be some confusion regarding boost taper.

One taper is 'caused' by the boost profile designed by the factory and is controlled by the ECU and boost control solenoid.

The other taper, as Ted B mentions, can occur when the CFM capacity of the stock turbo at a given pressure is exceeded. At higher RPMs and especially at boost levels above stock levels, the stock turbo runs out of breath. This is evidence by the characteristic drop in horsepower as the motor winds up towards redline.

trinydex

iTrader: (12)

isn't there also a boost pill in one of the vac lines that causes a taper when it sloshes around.

propellerhead

iTrader: (3)

The pill in the line doesn't slosh around or move. It's pretty welljammed into the line. It's purpose is to dampen the action of the wastegate when the boost solenoid opens.