Project Focus SVT Part III

Even on a stock SVT, the MAF signal looks like this. Note how erratic the signal is at low rpm. On our car, without the damping of the stock air filter box, the erratic readings happen under many more conditions, and each time there's a hiccup in the signal, there's a bog, stumble or surge. Time to move the MAF farther from the intake manifold.

Even on a stock SVT, the MAF signal looks like this. Note how erratic the signal is at low

The SVT Focus already laid waste to the Corba in the slalom, and the new tires just rubbed salt in the wound, pushing slalom speed to 72.1 mph, almost 5 mph faster than the Cobra. Yikes!

What's next
There are still some fundamental problems with our turbo setup. The MAF readings are highly erratic at idle and low rpm, causing it to buck and stumble at unexpected times. Even under relatively high-load part throttle acceleration, the sensor will occasionally spike, causing an annoying hiccup. Every time the ECU sees a spike from the MAF, it assumes there's really a bunch more air coming, so it throws in fuel and retards timing. The result is a car that is great at hauling ass, but sucks to drive in traffic.

The MAF also tops out at about 6500 rpm at 8.5 psi of boost. Wroblewski managed to supply the appropriate fuel at wide-open throttle between the end of the MAF's range and the 7800-rpm redline, (you can clearly see a dip in power when this happens, though) but at part throttle, the transition is usually accompanied by a huge stumble and fire shooting out the tailpipe. Not cool.The solution is to switch to a larger MAF (possibly from our nemesis, the Cobra) and to move it farther from the pulsating intake manifold. We're going to put it before the turbo, where airflow should be much smoother.

We also desperately need a blow-off valve. It's surprising the PTE kit didn't come with one in the first place, especially when it came with a 400-hp turbo. Because the airflow meter will read all the air the blow-off valve dumps, though, we'll have to plumb it to blow that air back between the MAF and the turbo. No big deal. We can drive the car to GT Fabrications now, and they can do all the work.

We'll also have to upgrade the fuel
pump as fuel pressure is rolling off from the target 40 psi to about 35 psi at high rpm. The Ford ECU is smart enough to adjust pulse width to compensate for the falling boost, but as this problem continues and we try to make more power, we'll run out of injectors. With a bigger fuel pump, pressure will stay up and our current injectors will be big enough. With the extra pump capacity, we can also increase the target fuel pressure with a few simple keystrokes, stretching our injector capacity even further.

We had a problem with oil getting into the intake after a few laps of the skidpad. The result was a storm of detonation and a frightening blue cloud. We suspect the scavenge pump is to blame. Oil is pumped into the oil separator used by the crankcase ventilation system, and it seems likely that this was filling up a bit and the high cornering loads caused it to barf into the intake. An oil catch can on the vent line from the valve cover to the intake might help, but we may go all the way and just reroute the pump's flow to the oil pan. It would mean welding, but we know people who do that.

With these problems fixed, we should be able to start cranking the boost. With the stock 10.2:1 compression and the 91-octane rancid pond water we use for gas, we'll crank it up slowly. With luck we can shave .7 seconds from our e.t. before a hole appears where none was before.

Of course, we'll also need a clutch. The stock clutch handles this power fine, even with a few quarter-mile passes, but try to do burnouts for the camera and it's toast. Needless to say, ours is toast. While we're in there, a limited slip is a must. On our measured tests it probably won't do that much, but in the real world, where we like to accelerate and turn at the same time, the open diff really sucks.

SOURCEBOX
Precision Turbo and Engine	Odyssey Batteries
FocusSport	The Progress Group
GT Fabrications	Shoreline Motoring

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