Re: [S4 (C4)] Hoppen, IA, TAP, MTM, Wetterauer: power + torque

["Frank Amoroso" <famoroso@sprintmail.com>]

For engine mods there is no doubt that an upgraded ECU provides the most
bang for the buck on the 20 Valve turbo (anywhere from $400 to $800). Some
would argue that a stiffer WG spring provides more bang for the buck. I'd
say you would then be fooling with BANG for the buck.

IMO though the first mod that should be done is the RS2 manifold. This is
purely from a safety standpoint as it helps safeguard against burning
exhaust valves on 1 & 5. The manifold is not cheap and not easy to install,
what with shortened studs and all. Some claim that you get an additional 10
bhp with this manifold. Sounds like a pretty round number to me and I am
pretty skeptical.

You can do a different turbo depending on what kind of boost pressures you
are shooting for and where you want the power in the rev range.

Do the manifold first, then the turbo if need be and then the chip (probably
the last two concurrently would be optimal). The PO of my car did this in
the opposite order, and installed the bypass valve backwards and
consequently blew the diaphragm on the valve. He then was getting 16 psig of
boost and the car was lagging hard and couldn't really get out of its own
way. He became disenchanted with it, sold it to me and bought an Acura NSX.
Such is life. I changed the bypass valve, found 6 psi and about 60 bhp.

I've driven:
        Stock,
        Stock turbo w/ chip,
        stock turbo w/ RS2 manifold and hot chip,
        hybrid turbo w/ chip,
        RS2 Turbo, RS2 manifold, and Lehman chipset (30 psi peak boost,
backs off to 25-26)

If you want to go with one of the major tuners, for the $$$ a Hoppen package
is tough to beat, no core charges or exchanges.

For low end power a Hoppen Stage 2+ includes a MTM 3.0 BAR box and a RS2
manifold. This setup sees about 26 psig and moves along nicely in the low
end. Nice for stoplight drags. The stock turbo does peter out at around
5,500 rpm. The tach needle slows a bit from 5,500 on up to redline.

For midrange and high end power the RS2 setup I've decided on moves plenty
of air through the motor. Has overboosted to as high as 30 psig (not good
from what some people have said) and then the computer backs it off 3 to 6
psi. Two words "freight train." This thing is a freeway monster and works
nicely on a 3,800 lb vehicle moving 75 mph. As soon as you start to get into
the boost in the upper 2,000s it begins to pull hard, then really comes on
and then the tach needle careens wildly towards the rev limiter. Good track
turbo.

The Intended Acceleration Car I drove with a very hot 3.0 BAR box RS2
manifold and stock turbo moved very nicely as well. It had the trip computer
boost gauge and its readings were too slow to react to the boost so I didn't
get a good feel for max boost.

I'm personally a fan of the K24 or the RS2. The engine was developed with
the K24 in mind and the RS2 was developed with that enigine in mind (along
with different ECU, cams, and exhaust).

I have been unable to find torque and bhp charts anywhere just claimed peak
bhp figures published. As soon as I win the lottery I'll buy a 4 wheel dyno
and will figure things out.

Product gauranties? As in bolt the ECU back in and the engine doesn't start?
Then I'm sure any of the reputable suppliers would replace the chip. Melt or
blow a hole in a piston? I'm pretty sure you are on your own.

WG spring. I've used a stiffer TAP version with an adjustable WG. It gave me
22 psig with TAP chip set and WGFV plugged in and 14 psig with the WGFV
unplugged. The stock spring and perch provide 6 psig with my current setup
and the WGFV unplugged.

Don't apologize for asking questions that is what we are here for.

Frank--