Next, AEBS supplied a set of Tomei Pro-series cams with valve springs and a set of AEBS lightweight titanium retainers. The Tomei cams are a short-duration, high-lift design featuring a lift of 11.5mm and a duration of 260 degrees, with recommended lobe centers of 110 degrees on the intake and 115 degrees on the exhaust. After the cams were installed and broken in, we changed our oil to Motul 300V synthetic in 15-w50 for protection even under severe track use. We also used a genuine Mitsubishi oil filter.
With fast valve action caused by the lift with this short duration, Tomei springs are mandatory with these cams. The cams' short duration makes for a nearly stock idle, with no loss of bottom-end power and good driveablity.
The cams and exhaust tie for "best bolt-on mod," dramatically increasing power above 4500 rpm with no loss in power on the bottom end. We experienced a peak gain of 8 hp, now up to 253.7 hp with a peak gain of 14 hp after the power peak. Unfortunately the dyno operator only took data to 7000 rpm on this and subsequent runs when our prior data went to 7500 rpm. If we extrapolate our power curves to 7500 rpm, our peak gains would be estimated in the 25-hp range. Of course, we selected a conservative run to report these gains and still suffered run-to-run variability, although the cams slightly reduce this variability.
To suppress the detonation and changes in boost pressure and spark advance, we installed an Aquamist water injection system. Usually water injection doesn't produce gains unless the engine is tuned around the water, and/or the boost pressure is increased, but we wanted to see the water's effect.
The Aquamist system is unique in that it uses a high-pressure 130-psi pump and atomizing nozzles that provide a fine spray of mist vs. a stream of water. The pulsating effect of the pump produces a variety of sizes of water droplets. Fine drops vaporize right away and provide charge cooling. Bigger drops reach the cylinders and suppress combustion and detonation. Water injection is very useful in road racing and does a great deal to keep the engine's temperature down and ensure reliability.
We used a Hobbs pressure switch to trigger out water injection at about 10 psi of boost. The Aquamist system can be tuned by changing nozzle size and nozzles, from .5mm to 1.0mm, in .1 mm increments. We used a .7mm nozzle to start with. When water is injected into an efficient turbo engine without any tuning changes, a power loss of around 10-15 hp usually results. We were expecting this and that's what we got.
We lost nearly 11 hp to the water, but what's interesting is that with the elimination of detonation, all of our power runs are now very consistent. Since we know the water is working to stop detonation, in our next installment we'll tune the engine and water injection system to exploit what can be done with very poor quality gas.
Finally, we readjusted our cam timing, running the exhaust cam straight up and the intake cam 2 degrees retarded. We were rewarded with an 8-hp gain up to 262 hp with no loss of power anywhere else in the powerband.
The combination of cams and timing gears is awesome, with 16-peak hp more and, if our dyno operator had revved it to 7500 rpm, we suspect a peak gain of 50 hp could've been had at high rpm. When the cam timing is optimized, the Tomei cams are the best single mod we applied to Project EVO.
All in all, we gained 30-peak hp, with a minimum of 3-hp right off of idle and a maximum estimated 50 hp at 7500 rpm. Our maximum verified gain is nearly 40 whp. This is seemingly impressive, but we're disappointed.
Other EVO tuners have reached 300 whp with similar mods, but with higher-than-stock boost levels and 93- or 94-octane fuel, we can't turn up our boost without detonation. Considering this, we're not doing so bad.
Our bad gas is hampering our goals. In our next installment of Project EVO, we'll tweak the ECU and tune around our water injection system in an attempt to reliably get more than 300 whp on 91-octane gas. We'll be back, crappy gas and all.