In the last installment, the Galant received a front-mount intercooler, high-flow cat and a new mass air unit. Power increased modestly, even using the stock turbo.
While it would be possible to make 300 hp to the wheels or more with the stock unit, Doug's Dynopower (DDP) decided to install the upgraded turbo. The TD05-16g, a direct replacement bolt-on, is undoubtedly the most popular and widely used turbo on 4G63 DSMs, whether it be a 1g or 2g vehicle. With a healthy flow rate of 505cfm at roughly 15 psi, the TD05-16g flows more than 100cfm more than the standard issue TD05-14b. Its reliability and relatively low cost add to its appeal. The new turbo spools a little slower than stock, but more than makes up for that when engine speeds climb above 3500 rpm. Boost remains constant all the way to redline. The stock unit would start to drop off after 5500 rpm. The stock exhaust manifold was ported during the turbo swap to enhance flow. Simply removing some of the casting flaws and restrictions in the collector resulted in improved throttle response as exhaust backpressure back into the cylinder head is reduced. This also helps regain some of the lost spool-up performance.
Anytime a larger turbo is used on the 2.0-liter 4G63 turbo engine, the fuel pump needs to be upgraded. The Galant has a rather small factory fuel pump, similar to that of a 2g Eclipse. Doug's Dynopower installed a Nippendenso upgrade unit that required a little modification to fit. The upside is the pump is known to support up to 400 hp at the wheels, which is DDP's goal with this car.
Having the ability to adjust the air/fuel ratio on the engine becomes more important as power levels climb. The stock ECU has a rather rich air/fuel table at wide-open throttle, which can hurt peak output. Using an A'pexi AFC, allows the manipulation of the airflow signal from the mass air to the ECU. In essence, opening and/or closing the injectors in a plus or minus amount over the stock table at eight engine speed settings on the AFC. On this car, we spanned 1000 to 8000 rpm in 1000-rpm increments, which provides the aforementioned eight fuel tuning points. Once larger injectors are used, the AFC will be invaluable in keeping the bigger injectors in check at idle and low-rpm levels, with good idle quality and a respectable air/fuel ratio.
In order to monitor the air/fuel ratio, an ATR meter was installed on the car. Having used this style of meter for many years, Doug's Dynopower reports it is very reliable and easy to read at a glance. No swirly or circular faceplates with colors that don't show up during the day. Just a simple bar graph with three different colors of lights, and incremented in terms of the actual air fuel ratio in relation to stoich, ( 14.7:1).
On a turbo engine, Doug's Dynopower tends to aim for a ratio of 12.5:1 to 12.7:1. Alternatively, using a standard voltmeter attached to the engine's O2 sensor, roughly .90-.95 volts at WOT should be realized to attain the desired ratio. With pump gas as suspect as it is these days, richer is safer.
When it came time for a boost controller Doug's Dynopower's Doug Derby chose the Turbo XS HPBC manual unit. Its ease of adjustment, ability to hold boost levels rock solid and its budget-friendly price were prime attractions. Once dialed in, one turn of the adjuster really does increase the boost one psi. It doesn't get much more straightforward than that.
Off To The Dyno Cell
The upgraded turbo made a healthy gain from 2,500 rpm on up. Most notable was the increase in the torque curve. Boost steadied at 16 psi all the way to redline. Peak power checked in at 299.1 hp and torque was an impressive 322.4 lb.-ft. A Technomotive datalogger program on a laptop was used to monitor air/fuel ratio and timing in relation to engine speed. The data was used to tweak the AFC on the second dyno pull.
The second run adjusted the AFC based on the logged data, and increased the air/fuel ratio from .88 volts to roughly .90 to .92 volts from 3000 rpm up on the high load table of the AFC. This was accomplished by upping the fuel by 5 percent at each 1000-rpm increment from 3000 to 8000 rpm. Power bumped up to 307.2 and torque registered at 334.6 lb.-ft. There was a hole in the previous run's air/fuel ratio from 3000 to 4500 rpm. Adding fuel in this range smoothed out power delivery. The extra fuel in the upper range was a safety measure to guard against detonation. It never hurts to run slightly rich.