I'm not sure if this is the proper forum, but here goes.

On Camaros, 1990 was the first year for SD and the electronic speedo. On Firebirds, the first year for SD was also 1990, but the electronic speedo debuted in 1986 (I believe). So is there a difference in the Camaro and Firebird ECM and/or EPROM from 1986 thru 1989?

In conclusion, there is no SD/cable driven system. So to convert my 1987 MAF system (with cable-driven speedo) to SD, are there any modifications required to my VSS system?

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Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
Paxton (6-psig): 12.57 @ 111 mph.
Paxton (6-psig) & 50-hp nitrous: 12.04 @ 114 mph.
ATI D1SC (10-psig): ?

http://willie.camaro-firebird.org/

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

[This message has been edited by Willie (edited February 26, 2001).]

 

Willie, go here:

http://www.ece.udel.edu/~davis/z28/ecm_swap_730/

Mike Davis uses an input for the speed sensor not shown on the F-Body '730 schematics and makes a PROM change (as you'll see at his site). Frankly, this was confusing to me. My Helm's for '85 Firebirds shows an optical VSS (2K PPM)for mechanical speedos which, in turn, is fed thru an electronic buffer into the ECM. The '730 reads from a Magnetic (4k PPM)VSS directly. Apparently, Mike knows of some input for cable-driven speedos on the '730 ECM.

 

First let me say that I am NOT sure about this. Theory often differs from reality. However, the PROM change that I believe Mike is referring to is setting the 4000 pulse constant to 2000. In TunerCat this is called the 'Road Speed Constant'.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org