[Gmecm] 1227747 rpm vs gear table
David Haggard
david
Wed Jun 8 13:01:27 UTC 2005
Darryl--
Thanks for the insight. But like I said, I find the light just plain irritating, and basically useless because of where it is located on my dash (far right, and out of line of sight when driving).
>From what you just described, I now understand what that table is for that I never used. (The mph/rpm ratio table.) When I started, the TunerCAT definition file for '747 didn't have that table defined yet. I never saw it until I downloaded an update after I had already disabled the light. That table wasn't right for my car, because the '747 bin I started with was one from Edelbrock for a different model. My car originally had the 1228063 ECM, and the TunerCAT definition file for it was definitely lacking in the settings I needed. My 305 build is so radical (1.25 horses per cubic inch without power adders) that I had to use a combination of TunerCAT and WinBin to get it right. Even had to build my own WinBin definition file to get all the settings I needed. And even with that, the only way I found to get a stable idle was to force it to open loop idle by setting the open-loop idle threshholds at 1175/1200 rpm, and opening up the throttle plate to allow less than ten IAC counts at idle. That gives me a lopey but stable idle at 700 rpm, where a closed-loop idle will hold for a few seconds, then try to stall, then jump up, then settle in again. Even if I shot for a high idle speed.
But I digress....
I haven't used RT Tuner. I've built my car on extremely limited budget. Get the parts as I can save up for them and buy them basically one at a time. Took me 9 months to build the motor that way! So while RT Tuner is a great piece of software, I haven't been willing to spend another nearly two hundred bucks to get the software and the ROMulator. So I did it the "old fashioned" way like Bruce Plecan described. Like him, I've burned about 100 chips to "get it right," and another 300 to "get it perfect."
Glutton for punishment-- Now I'm looking at building an LS2 copycat starting from a 350, to get the torque that the 305 lacks.
David
> -----Original Message-----
> From: gmecm-bounces at diy-efi.org
> [mailto:gmecm-bounces at diy-efi.org] On Behalf Of Darryl M Gilbert
> Sent: Wednesday, June 08, 2005 6:51 AM
> To: gmecm at diy-efi.org
> Subject: Re: [Gmecm] 1227747 rpm vs gear table
>
> 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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