Toyota Prius Analysis

With the results of the Prius being what they were, we decided to run another one to verify our results from before. The 2007 Prius was what we got. Since we had tested the 2005 with the stock gap we ran this one with the recommended gap we tell you guys to set them at, but why are we able to get such great results from this already highly efficient car?

The answer was actually staring us in the face but we didn't notice it until the second car was being run. At say 55mph, the rpm of the engine is less with Pulstar plugs installed as opposed to stock plugs. What does this mean for fuel economy though?

Fuel economy is simply with engine load (throttle position) vs RPM vs speed. If our speed stays the same and our throttle position stays the same but RPM drops, we have an increase in fuel economy. In our case the throttle position directly relates to RPM because of the Continuously Variable Transmission (CVT) this car is equipped with.

The above graph shows RPM over time. The speed is pretty much fixed because of the drivers trace. You can see that the Pulstar line averages a lower rpm standing than the stock plugs. Amazingly, the engine turns only about 1800 rpm at around 75mph when equipped with Pulstar plugs.

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2005 Hyundai Accent

If you were asked to picture an economy car in your head what would it's qualities be? Underpowered? Slow? Good gas mileage, right? It seems that 'good gas mileage' is synonymous with 'slow', but what if there was a way that you could have mileage and a little bit of speed? That's where Pulstar plugs come into play. Lets see how the Accent fairs.

Stock, this car pulled 103 HP at 5900 rpm and 102 Ft-Lb at 4700 rpm. The little car accelerated from 65 to 80 mph in 6.65 seconds over .14 miles of simulated road. The fuel economy test ended at 998.59 cc of fuel used.

With Pulstar plugs BE-1 installed the engine made 105 HP at 5900 rpm and 104 Ft-Lb at 4550 rpm. The acceleration test gave us 6.57 seconds in .13 miles and only consumed 953.17 cc on our dyno. That was the least we'd seen on our dyno so far for fuel economy.

The difference is there and can be seen. For those of you that wonder if the 2 hp was from dyno error, the runs with both sets essentially superimpose each other, the only difference is seen when the plugs are swapped out. We saw a 2 HP increase (1.9%), an extra 2 pounds of torque (2.0%) and a 4.5% increase in fuel economy.

Unfortunately, this car was an automatic, because of this it made getting power pulls difficult. As you can see, the only part of the engine's powerband that we have graphed are between 4250 and 6000 rpm. We are able to see peak torque and horsepower in that graph so it does tell the tale but We aren't able to see what torque gains gave us the MPG increase. With a fuel savings of 4.5% you'll use that much less fuel, or at $3.50 a gallon, you save an extra 16 cents per gallon.

www.pulstar.com