Author: Ken Payne
The previous article in our Roush F-150 project truck series covered the Roushcharger intercooled supercharger installation article.
Before and after power gains were left out and I’m sure many of you are dying to know the bottom line results. We did
a series of dyno pulls before and after the supercharger installation in order to get a picture of the power gains. Graphs alone
don’t tell all the data unless I present some additional information with each graph.
You’ll notice the graphs do not start at idle speeds. When you go from idle to full throttle on these trucks there is a sudden shock of power through the torque
converter. With manual trannies you’ll generally see numbers generated lower in the RPM range. The more power from the start, the higher the RPMs before the
dyno’s drum sampling settles enough to get good numbers. This power surge is even more apparent with the supercharger.
In the above graph you see stock horsepower and torque. There are a couple of things to note here, or the Roushcharger graphs persented later won’t make sense. First, you’ll see that this chart plots the truck’s power all the way to 5800 rpm. This will not happen in real life driving. The 5.4L 3-valve V8 has shift points around 4800-4900 RPM so the graph in real-world usage would suddenly drop around 4900 rpm. Second, the abrupt drop-off at 5800 RPM is due to the factory RPM rev limiter.
In this chart you see the Roushcharger horsepower and torque. Again, there are a few things of interest here that help make sense of the plot lines. First, you’ll see horsepower and torque drop off quickly at about 5400 RPM but it doesn’t on the stop graph. This doesn’t mean there is a power loss here. What is happening is the computer is kicking in the boost-dump to prevent over-boosting the engine. This happens at (according to the raw data from the dyno) exactly 5316 RPM. This does not impact the truck at all in real-world conditions with the standard Roush tune because the shift occurs at 4900 RPM, well before the boost-dump kicks in.
Here you see the graphs overlayed. The total power increase was 121.26 HP and 118.22 ft/lbs. torque. Based on the graph trends it looks like peak torque with the
Roushcharger is actually much higher in the lower RPM ranges than this chart reveals (this truck will launch hard from a standstill). These numbers,
for "at the wheel numbers" are impressive and well within Roush specs when you consider drive-line loses on a 4×4 truck with 20 inch wheels. The torque
peaks very early meaning the truck starts up quick, and stay nearly flat across the entire rpm range, with horse-power increasing throughout the chart.
What does this all mean? Basically, not only does the truck come off the line fast but it keeps gain speed very quickly without falling off in power
like you’ll typically see in natually aspirated engines. Unlike a Mustang GT, which takes time to get into its peak torque area, a Roushcharger
equipped F150 is almost at peak torque right off the line. With proper launching for traction, most Mustangs don’t stand a chance even against the much
Roush F-150 Project Truck Source:
(Copyright 2007 Ken Payne, All Rights Reserved. This article is used by Internet Brands, Inc. with permission – no license is given beyond this permission and may be revoked by Ken Payne.)
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