[Gmecm] 1227747 rpm vs gear table

Wed Jun 8 11:50:42 UTC 2005

David: From what i have learned so far you are correct partially. The TCC
tables, and shift point tables, and load tables are all inter connected.
The TCC portion of the tables control shift light if no TCC or Kick down
relay used. you simply do not connect any of these things. At this point
you can use a light to show best shift point. Yes the ECM does not use
this data for anything when shift light is used, but does use this stuff
when TCC or Kick down relay. is required. I was just playing with it to
better understand how the tables were derived. I do know that the 1st
table does tell the ECM what gear you are in based on MPH/RPM ratio If
these ratios are correct for your car it will then point to the correct
entry in the shift point table. So far I have it working properly in 1st
and 2nd but when in 3rd it still thinks i am in 2nd, this means the 1st
table in my case is still incorrect. For 4th gear it is correct for i
have that set to 254 and the light no longer comes on. What i was wanting
to know is how is the first table computed?. I just wanted to know this
to understand how they arrived at the numbers in there To determine what
gear i was in i set the shift light at several points 1st 3000, 2nd 2500,
3rd 2000 and 4th 254 which is probably 200mph or better when in 3rd it
still comes on at 2500 RPM meaning it did not move to the proper point in
the shift table. It does however know i am in 4th for light never comes
on like i told it not to.
thanks for the reply...did you ever use RT TUNER??????
Darryl
On Wed, 8 Jun 2005 01:32:30 -0500 "David Haggard" <david at newcovenant.com>
writes:
> 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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