Muscle Mustangs & Fast Fords
Bullitt 5094's 9-Second Ride - Power Struggle Part 3
The Struggle Over Street-Worthy 9-Second Power Is Over, And We Won.
Leave Well Enough Alone? Not Us.
Mission accomplished, right? Not quite. Since we had confirmation from Vortech early on that the standard aftercooler would be a flow restriction on the new engine, we were already researching alternatives. This being a track car, we decided that staying with an air-to-water setup is the way to go. We realized that on some of the most recent track passes, inlet air temperatures rose to the 160 to 180 degree range, so we knew there was more air passing through than could efficiently be cooled by our existing system. But where do you put a larger intercooler? It was already tight in the modular engine bay, and in most instances, replacing the front seat with said intercooler, along with adding some large holes in the firewall for the air tubing, would be next.
Our friend, John McGuire, had the solution on his 9-second NMRA Modular Muscle track car, as he had installed a Precision Turbo 1000 air-to-water intercooler offset in front of his radiator. It offered greater airflow and inlet air temps so low they would occasionally cause a misfire. Watson picked up the PT1000 intercooler, and during this re-engineering session, he also eliminated the SCT draw-through MAF configuration and used an SCT 3000 tonsil-style MAF in a blow-through configuration. Jim Britts' fabrication talents were once again employed to reconfigure the new induction design.
After making these changes, we realized that the larger intercooler, with the Vortech Max-Flow bypass valve in a blow-off configuration, and a blow-through MAF has actually improved driveability. When we got the new setup on the dyno, we only saw a horsepower increase of 3, to 696 rwhp, but torque jumped up by 37 lb-ft to 588. Inlet air temps at the track went from 160-plus degrees to 60 degrees under similar track conditions. Also, boost dropped to 12 psi, but airflow increased so much that we had to install a MAF extender on the 3000 to keep it from maxing out.
The drop in boost pressure is due to the huge decrease in the charge temperature. Recalling high school Science 101, generally when you cool a gas, it shrinks, and that's what happened here. This means that the 100-degree drop in charge temperature has made the air charge much more dense, and that in turn lessens the flow restriction-basically, more power with less boost. Another upside is that the lower temperatures lessen the possibility of detonation.
At the track, there was a little more powder in the Bullitt, as it shot down the track with great speed and accuracy. Our best quarter-mile elapsed time dropped further to a 9.69 at 141.4 mph. This was promptly backed up with another 9.69 at 142.9.