What does the ECM use the data from the speed sensor for? I've noticed that when i'm on the brakes in neutral, the RPM's stay up to about 1300 and then drop to idle when i come to a stop. Is that to keep the vacuum up and pump up for the brakes? just wondering. thanks!

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85 2.8L Sport Coupe 5-speed.
Mods: Hpertech chip and powerstat, MSD 6A-L, Crane fireball coil, Dynomax hi-flow cat and catback system with a dynomax magnum race bullet muffler on the i-pipe, K&N filterchargers, Eibach Sportlines and Tokiko springs/shocks setup, Global west sub frames, Suspension techniqs front and rear sway bars, and good ole 88 IROC wheels with Kumo Ecstas on em!
"I'm out to seek those pesky VTEC boys!" (don't get me wrong, I'm asian myself! hehe)

Wins: 2000 V6 Accord, 69 302 Mustang, 2000 Auto VR6 Jetta, 89 Toyota MR2, 90 Civic Si, 76 350 Camaro.

 

The computer has several calculations in its memory that depend on the speed of the car. But it mostly looks at the speed of the engine, in RPMs, for its calculations.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.23 @ 107.62 MPH
Southern California
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The ECM looks at your speed to keep the RPM's up I think because it's expecting you to shift. I guess it's so the RPM's don't drop too much while your shifting. You could be right about the vacuum thing though, but I think you actually loose vacuum as the RPM's go up. Or is it the other way around? I'm confusing my self so I'll shut up now .

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88 firebird formula
350 Vortec TBI
214int/224exh, .471int/.491exh
Edelbrock headers
T56 - SIX-speed
open 3.73's
2 1/4 stock catback
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