Turbo Minivan Dyno Fun

On Feb 12, 2003 my minivan and I visited a local chassis dynometer. This was a new experience for both of us; it proved to be quite fun. As background info, my van's current setup is as follows:

all stock 2.5L bottom end, balance shafts removed
PowerStroke intercooler
lightly ported G-head plus .020" copper shim
stock cam with 130,000 miles
stock intake manifold with stock throttle body
exhaust manifold lightly ported by Gary Donovan
Garrett turbo off a junkyard Daytona (unrebuilt) with 2.25" downspout
+40% injectors, adjustable regulator plus Cartech secondary regulator
3" mandrel exhaust with cat and UltraFlow bullet muffler
K&N drop-in filter in a TurboII airbox (no airbox-to-computer accordian hose)
Turbo Action reverse pattern manual valve body

That last item is a crucial one. It allows me to begin near idle in third gear but when I floor it the trans stays in third without downshifting. Factor in 20 psi of boost--my daily driver setting--and this produces some interesting results:

Upon seeing this, the first question most people ask is how I make so much bottom end torque. Turns out torque converters do this really nifty thing called torque multiplication, which means your crankshaft torque is actually amplified in the low RPM range. It doesn't happen all the way to redline, of course, but it's a ton of fun while it lasts!

Anyway, examining the plot shows output figures which get rather jumpy in the upper rev range. In my case, this was due to a rich fuel mixture; my Dawes Device's top light was glowing steady. I didn't have time to actually tune at the dyno, but I'll address this concern before I go back again.

For those of you who also install manual valve bodies and head for the dyno, I must warn you about something. The engine rev limiter kicks in at 6100 RPM, as we all know. I was planning to make a pull all the way to that point and I was in the process... until the computer halted the fun at 5500 RPM. Turns out these vans also have a top-speed governor! So if you plan to go faster than 120 MPH, you'll have to counteract it. Just lettin' ya know.