Speed Scene Wiring

1986–1991 Tuned Port Injection

TPI Wire Harness | TPI Wiring

Stand-alone TPI harnesses for Y-Body Corvette and F-Body engines. VATS removed, fully custom-built with all relays, locks, and EPA-approved wiring.

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TPI 1986–1991 Wire Harness

TPI 86–89/1991 Y-Body design fits the Corvette engine and can also be made to operate the F-Body engines. The computers from this era have something called VATS (Vehicle Anti-Theft System) — this is removed on all Speed Scene Wiring harnesses through a computer process.

The layout is uniform on all Stand Alone harnesses built from scratch. Complete with all relays, locks and much more.

We also take custom orders. If you have a specific harness layout that you would like, we can tailor fit to your measurements.

TPI 1986–91 wire harness assembly

TPI 1990–1991 Speed Density

Tuned Port Injection

TPI 1990–1991 Speed Density Tuned Port Injection systems of this year are dubbed with the name Speed Density. The transmission choices are 4L60 (No E, Vette), 700R4 (F-body), 6-speed (Vette), and 5-speed (F-body).

The distributor of this year was a small EI (Energy Ignition) system that sported an external coil. The meaning of the name Speed Density is composed of the simple truth — the metering air capabilities are based on speed from the EI distributor being RPM, temperature of the incoming air, and temperature of the coolant.

The IAT is left to modify mixture values. Along with a good base idle, the Idle Air Control Valve (IACV) supplies a controlled vacuum leak, allowing the engine to idle smooth.

In the older 1985–89 TPI computer, the fuel injection system could measure the mass amount of air coming into the engine as well as the temperature of the air. The speed density system is a solid performer — if left stock, a great performer in water/wet off-road applications simply because there is no Mass Air Flow sensor to short out.

Transmission Options

  • 4L60 (Vette)
  • 700R4 (F-Body)
  • 6-Speed (Vette)
  • 5-Speed (F-Body)

VATS Removed

Vehicle Anti-Theft System (VATS) is removed on all Speed Scene Wiring harnesses through a computer process — no bypass modules, no workarounds.

All EPA Approved Wire Harnesses Come With:

  • VSS Circuit
  • Diagnostic Link Connector
  • Correct Connector for Emissions Components
  • VSS Pigtail
  • Alternator
  • Tach Pigtail

Ready to Build Your TPI Harness?

Custom length, stand-alone build. VATS removed. EPA approved. USA made since 1999.

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