stevekh44

Well the autocross season ended yesterday and I put the car away
tonight. Now I'm trying to put together the winter plan for
improvements. The car is a 13b with a single TO4B turbo with dual
Tial 38mm wastegates and a Greddy Type R BOV. Engine management is
through a Haltech 6K. 550cc primaries w/ 680cc secondaries.

Throttle response and straight line power is amazing. My concern is
that the power comes on quickly and like a hammer. While it is
wonderful launching and in a straight line it causes the car to be
difficult to drive in corners and I find I am always on and off the
gas which is not the fastest way around because it upsets the balance
of the car.

My question is: Is there a way to enjoy the power without the feeling
that my right foot is controlling a switch?

I want the straight line power, but I also want to improve the
driveability in corners. I sometimes think that limiting boost under
5k rpm would allow me to keep the car balanced in the corners and then
allow boost to build over 5k rpm would give me the straight line
power. I don't know how to set this up. I originally was running
10psi wastegate springs, but moved down to 7 psi. The car was more
driveable and my run times dropped, but I feel there is a better
answer than just limiting total boost.

A friend suggested that the problem is the way the turbo spools up.
His thought was that the turbo housing is too big for the application.
He said that having a housing that is too big will result in a
relatively high rpm spool up with an abrupt hit of boost. He
recommended using the existing turbine but go to a smaller housing.
This would give you boost at lower rpms and it will seem to spool up
slower and make it more drivable. Does this make sense?

I've looked at boost controllers and they don't appear to give me the
control I'm looking for. Or am In looking at it wrong. Should I go
to some really weak wastegate springs and then try to control building
boost vs. RPM instead of looking to limit boost?

Any help would be greatly appreciated. Thanks!!

Crusader_9x

going to a bigger hotside will slow down the spool up. although i havent looked at that particular feature i am pretty sure that the avcr offers something loke that for boost control. if not the avcr then i am sure some boost controller out there will.

kks_John

the greddy and Apexi electronic boost controllers both do RPM based boost and Gear based boost. you should check them out, sounds like what your looking for

Infini IV

Do you know what turbine housing A/R you are currently running? You could try running a tangential .81 collected or .84 divided (depending on whether you have a divided or un-divided manifold) if that's not what you already have.

The Apexi AVCR has gotten several good reviews, especially with it's gear-dependent boost feature. It's very well-priced for what it does, although it's getting old already.

stevekh44

I understand that a boost controller allows the boost level to build in certain situations by interupting the signal to the wastegate. How does a boost controller limit the amount of boost that can be built??

Infini IV

Your wastegate spring still needs to be rated to however much boost you want as your lowest setting. Basically, turning off your BC will allow however much boost your spring is rated at.

Each BC has a different design, but they all do the same thing (which is what you said... interupt the signal to the wg). They dont't really "limit" the amount of boost, but only add-on to the amount of boost allowed. Your base level of boost will always be found in the pressure of the spring in your wastegate.