[Gmecm] 1227747 rpm vs gear table

[David Haggard]

I have an '88 Firebird with T5 manual, and running a '747. The shift light does not let the ECM know what gear you are in. Just the opposite. It uses vehicle speed and engine load to turn on the shift light so you know when to shift for best fuel economy vs. how hard you are accelerating.

My Firebird, even though the shift light is a stock feature, has nothing to indicate to the ECM what gear the transmission is in, except 5th gear. There is a switch in the side of the transmission to do this. It is only switched on when in 5th gear.

I'm afraid that with your Saginaw 4-speed, you won't have any way to control the shift light in 4th gear. So when you get in top gear and settle into a cruise mode, the shift light will switch on and stay on, unless you give it more gas for power enrichment mode.

Somebody correct me if I'm wrong about this.

Personally, I always found the shift light to be an irritation at best. Mostly it's useless because it's neither bright enough nor in a good position to be effective. So I have disabled it. 

If you don't have a shift light installed, then don't worry about it. It will have no affect on your tuning. But if you do have have a shift light, or you want to be sure it can have no affect, then here are the settings I used. The shift light circuit also controls the TCC with an automatic transmission. I set it up to turn on the shift light ONLY if I over-rev the engine. My self-declared red-line is 5500 rpm, even though the motor will easily rev well past 6000. Don't want to blow it up! But I doubt I'll ever notice the light if I'm revving that high!

With these settings, my shift light will not come on unless I rev past 5500 rpm or get over 255 mph.

In the ECM Constants table (TunerCATS software):
	TCC Lock, Low Gears, High Speed: 255 mph
	TCC Lock, Low Gears, Low Speed: 254 mph
	TCC Lock, High Gears, High Speed: 255 mph
	TCC Lock, High Gears, Low Speed: 254 mph
	Force Shift Light On RPM Threshold: 5500 rpm


Dave Haggard


> -----Original Message-----
> From: gmecm-bounces at diy-efi.org 
> [mailto:gmecm-bounces at diy-efi.org] On Behalf Of Darryl M Gilbert
> Sent: Saturday, June 04, 2005 9:04 PM
> To: gmecm at diy-efi.org
> Subject: [Gmecm] 1227747 rpm vs gear table
> 
> Hello: Really new at this, so bear with me. Getting feet wet 
> on a 1227747 running a 355 TBI. Have several issues, but lets 
> take them one at a time (easy ones first) There is a table 
> associated with SHIFT LIGHT. It appears to be able to let the 
> ECM know what gear you are currently in. I would like to know 
> what is the formula for calculating the entries into this 
> table. Using a 4 speed Saginaw, so i guess 4th is not used 
> due to no more gears left to shift to. Does that make any sense?
> thank you
> Darryl...
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