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Old 11-18-2010, 09:53 AM   #32 (permalink)
Joseph Davis
Join Date: May 2008
Location: ashEVILle, NC
Posts: 35

Beater Deluxe v2.0 - '89 Honda Civic DX
90 day: 44.68 mpg (US)
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No, a wideband isn't needed for daily operation. Only for the initial tune on the vehicle. Narrowband O2's are actually very accurate away from stoich; but their curve is logarithmic, a low amplitude analog signal prone to being molested by ground ofsets, and their calibration varies with sensor temperature. Run a heated four wire sensor a little ways down the exhaust stream so engine heat doesn't molest it - approx where the driver's feet are on a distributor Honda is fine - and make sure you keep the sensor's power and signal grounds seperate until they finally reach the block which is THE ground point in a car's electrical system. Chassis grounds are garbage.

I've been doing a mini engine R&D project with a friend, putting the 01-05 D17 cranks into earlier D16 engines. There's a lot of misinformation about the reliability of this combo resulting in few people doing this combo - it's mostly kids who don't know how to build an engine messing things up.

Anyway, 9:1 static CR 1.7 stroked D16Z6 1991 RT4WD wagon with an Evo8 turbo and Siemens Deka 500cc (at 43.5 psi, aka 04-05 SRT-4 injectors). Part throttle maps were tuned for 15.5-16:1 AFRs, and runs a (fresh!) stock O2 sensor whose lean/rich switch point has been set to 0.39 volts. The combo makes 185 whp at 7.5 psi and 235 whp at 12.5 psi, uncorrected figures. In 4WD, some spirited driving, 32 mpg. In 2WD, normal driving, 43-44mpg. Wagons are heavy and aerodynamic bricks, 4WD/AWD drivetrain loss is appreciable, and the air is thin as well as the land not flat up here on the mountain.

A third of the gains are tuning the vehicle. A third of the gains are having a working O2 sensor with a lowered switch point. A third of the gains are having a modern pencil core injector that atomizes far far better than earlier injectors. I've also spent a number of hours on the dyno placing the ignition event at the optimum point for all NA loads and speeds under 4000 rpms, as lean burn doesn't accomplish as much if the ignition timing doesn't place peak combustion pressure accurately at the "sweet spot" where the rod has best mechanical leverage against the crank.
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