The fun of assembling a hot engine combo comes from the anticipation of what we expect it to do. If you've been following the progress of this twin-turbo, 505ci engine buildup for Jeff Hutchens' '67 GTO, then you know it's dyno time! In this installment, we show you how much power it makes and discuss some aspects of tuning its FAST (Fuel Air Spark Technology) electronic fuel-injection system.
FAST's EFI system aids in making a seemingly impractical-for-the-street engine like this much more tractable on the boulevard. Yes, turbocharging has been around for a long time, but up until electronic fuel-injection systems became readily available, street tuning a turbo involved more compromises than most care to admit.
Don't let this apparent rat's...
Don't let this apparent rat's nest of wires scare you off. The FAST wiring harness is clearly labeled and easily connects the FAST ECU to all of the various sensors.In this application, there's a 3-bar (up to 30 psi) map sensor; water and air temp sensors; an idle air control motor; a throttle position sensor; and, of course, a wideband (9-1 to 19-1 A/F ratio) oxygen sensor.
The real benefit of an EFI system is very precise control over fuel and spark functions across the entire rpm and load ranges. It's critical that these parameters are precisely set. That's why an experienced tuner is so important to a build such as this, so Travis Quillen of Quillen Motorsports Engineering was called upon to tune the 505 for the break-in and power pulls at Wheeler Dyno Service in Blaine, Minnesota. A professional EFI tuner knows how to set up safe timing and air/fuel ratios at the start so the engine isn't destroyed on the first pull. It can run rich with retarded timing all day long-but excessively lean and too advanced only once. This is especially true under boosted conditions.
One myth that we should dispel right away is that EFI in and of itself will produce significant power gains. The truth is, a properly tuned carburetor that has an equal flow rate to the EFI system will pretty much match what an EFI system will produce when it comes to peak power. But with very accurate control of the fuel and timing, you might be able to push the limits a little closer to the edge and run a little more compression or boost, and a little more timing. Improvements in part-throttle operation and in the lower-rpm ranges can be possible with judicious tuning because there is more control over the fuel and timing at every rpm and load level than with a carb and standard distributor.
FAST can supply a dual-sync...
FAST can supply a dual-sync distributor that sends cam position info to the ECM to run sequential injection instead of bank-to-bank firing of the injectors. The advantages of sequential injection are individual control over each cylinder's fuel, and less stress on the fuel system since the injectors are actuating one at a time.
One way that EFI has more flexibility is with the ability to switch back and forth between more than one tune. You can optimize the first for general cruising on pump fuel and have the second for when you are feeling restless and want to dump in some C16 and go racing. Think of it as a jet-and-timing change by way of a laptop. Consistency should also improve because EFI systems can be more accurately tuned.
At the heart of the FAST system are tables or "maps" that control the amount of fuel delivered at every rpm and load; the amount of timing at every rpm and load; and target air/fuel ratio for every rpm and load. Quillen is an experienced tuner who knows how to program these tables with safe numbers for any engine. Initially, he likes to be conservative regarding timing, beginning just a little rich with the fuel, and only allowing moderate boost until he can get a good baseline pull he can use to find out what each engine really likes.
While showing all of the steps in this process is really beyond what we have room for here, we will show you some highlights so you can speak intelligently with your tuner. (FAST also has a rather in-depth DVD that is worth a serious look.) In simple terms, the tuner will decide on a target air/fuel ratio and then modify the volumetric efficiency table until that target air/fuel ratio is reached with a near-zero correction on the oxygen sensor.
Though not a part of this story, once the session at Wheeler Dyno Services is complete, the engine is off to MCR to be bolted into the GTO and tested on MCR's Mustang chassis dyno.