Anyone ever tinker w/ trip/mileage computer?
Thread Starter
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Anyone ever tinker w/ trip/mileage computer?
Just wondering if anyone ever figured out how to adjust the mileage computer after going to larger injectors. It was always optimistic but now it's about double what I'm really getting. Thought it would be fun to try & fine tune the code for it.
Thread Starter
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Hmmm... not quite for my '90 L98 (Speed Density).
Yes that is the value we changed for my new 42 lb injectors (41.98 which work great by the way & a big thank you to Greg@blowerworks.net) but that didn't effect my mileage computer. It shows about 44 to 50 MPG & I'm actually getting about 1/2 that.
Yes that is the value we changed for my new 42 lb injectors (41.98 which work great by the way & a big thank you to Greg@blowerworks.net) but that didn't effect my mileage computer. It shows about 44 to 50 MPG & I'm actually getting about 1/2 that.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Thats cause your injectors are almost twice as big as they were from the factory. There is 2 settings, one is the injector flow rate which matters for tunning sake, and the other is DISPLAY injector flow which is different. Maybe the L98s were different in terms of ECM constants, but there will still be 2 setting there somewhere or your dash wouldnt show double the MPG due to there being double the flow capacity.
Thread Starter
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Okay, I'll look again for that constant. Didn't see it in TunerPro but doesn't mean I didn't miss it. I can email/post or you can pick up the 8D layout if anyone cares to look over my "shoulder". 
Well damn... just looked again & I don't see ANY constants for Display.
Well damn... just looked again & I don't see ANY constants for Display.
Last edited by Trog; Aug 11, 2006 at 10:30 PM.
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
I just looked through the TunerCat listing for $8D and don't see anything.
You might try contacting tunerpro and asking them if they know how to do it - maybe it's a byte that hasn't been identified yet.
You might try contacting tunerpro and asking them if they know how to do it - maybe it's a byte that hasn't been identified yet.
Cruising
Joined: Mar 2006
Posts: 11
Likes: 0
As far as I can tell from ANHT_hac
is 22 lbs/hr injectors and
is 3.776 gal/hr (display).
I don't know about TunerCat but in case of TunerPro I've added the latter constant my self.
Code:
L841C FDB 0460
Code:
L8824 FCB 0118
I don't know about TunerCat but in case of TunerPro I've added the latter constant my self.
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Thread Starter
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Okay, I need you to elaborate on what you just said...
ANHT_hac is something I've not seen/heard of before so lets start there.
And it sounds like you added a constant on your own in TunerPro, which that is the program I've been using so far to mod my bins for EGR delete, cooling fans off/on & now my injector flow update.
Just haven't gone so far as to add my own constant field definitions. If you can explain where, how etc. & define better what you wrote on those two Codes I would appreciate it.
TIA &
ANHT_hac is something I've not seen/heard of before so lets start there.
And it sounds like you added a constant on your own in TunerPro, which that is the program I've been using so far to mod my bins for EGR delete, cooling fans off/on & now my injector flow update.
Just haven't gone so far as to add my own constant field definitions. If you can explain where, how etc. & define better what you wrote on those two Codes I would appreciate it.
TIA &
Cruising
Joined: Mar 2006
Posts: 11
Likes: 0
The 90-91 Corvette uses the 122727 ECM. Inside it there is a 27256 EPROM that contains calibration data and the assembly program for fuel injection, spark advance and so on. Depending on you “application” there are different callibration/assemply programs. For example, the ANHT is for 90 Corvette with auto transmission and in my case I have AXCN which is for 91 with 6-speed. ANHT_hac is a translation of the EPROM into a commented assembly program and “tuning” parameters. The adresses of these parameters are specified by a “mask”, in case of the Corvette 1227727 it is named $8D.
You can find ANHT_hac on Moates site. Older Corvettes uses 1227165 ECM and in that case you can look at ARAP_hac which is for 89 Corvette ($6E mask and 27128 EPROM).
I added a constant “Injector flow [gal/hr]” at address 8824 (hex) and scaled it by a factor 0.032. To add a constant right click in the “constant/scalars window” in TunerPro and choose “Edit item”. Note that I have only found the factor 0.032 in one place so I have not confirmed it from a second source. In other words, can someone confirm/correct this factor please do so.
Good luck and don’t hesitate to ask more questions!
You can find ANHT_hac on Moates site. Older Corvettes uses 1227165 ECM and in that case you can look at ARAP_hac which is for 89 Corvette ($6E mask and 27128 EPROM).
I added a constant “Injector flow [gal/hr]” at address 8824 (hex) and scaled it by a factor 0.032. To add a constant right click in the “constant/scalars window” in TunerPro and choose “Edit item”. Note that I have only found the factor 0.032 in one place so I have not confirmed it from a second source. In other words, can someone confirm/correct this factor please do so.
Good luck and don’t hesitate to ask more questions!
Cruising
Joined: Mar 2006
Posts: 11
Likes: 0
Originally Posted by Spankyellow
I have a tunerpro ecu file for my 87. The mpg readout is the last item listed in the constants.
Thanks!
Race Director
Joined: Sep 2003
Posts: 16,838
Likes: 341
From: Database Error Indiana
The is for a 6E arap bin. location is 70c. I just remembered seeing it and thought it may give you a place to look. I actually saved the file for a possible future use, but I have a pretty good chip done by someone else, so I never got that far. Remember, I have an 87 with the 165 ecm. Its likely different from yours.
Remember, I have an 87 with the 165 ecm. Its likely different from yours.
Cruising
Joined: Mar 2006
Posts: 11
Likes: 0
Originally Posted by Spankyellow
The is for a 6E arap bin. location is 70c. I just remembered seeing it and thought it may give you a place to look.
Melting Slicks
Joined: Aug 2003
Posts: 3,407
Likes: 400
From: Lakeville MI
In 32B, the display gallons/hr constant is located at location 712 with a default value of 122 (decimal) or 7A (hex). This raw value (in decimal)must be divided by 32 to convert to gallons/hour.
default value at LC712: 0x7A or 122/32 = 3.8125 gal/hr.
I'm currently using 8C (hex) at this location. 0x8C = 140 decimal.
140/32 = 4.375 gal/hr
This was changed to better fit my raised fuel pressure (54 psi).
Ok, Just checked 8D (anht_hac.pdf):
L8824: FCB 118 ( or 76 (hex)). Look for a hex value of 76 at location 824.
This is shown as 3.776 gal/hr, but 118/32 = 3.6875 gal/hr doesn't quite fit. However: 118 * 0.032 = 3.776 Bingo!.
I would simply scale up this value by the new injectors/old or 42/22 * 118 = 225 decimal or E1 (hex). The exact resolution? 0.032 or 1/32 (0.03125) doesn't really matter since this is a proportional change.
default value at LC712: 0x7A or 122/32 = 3.8125 gal/hr.
I'm currently using 8C (hex) at this location. 0x8C = 140 decimal.
140/32 = 4.375 gal/hr
This was changed to better fit my raised fuel pressure (54 psi).
Ok, Just checked 8D (anht_hac.pdf):
L8824: FCB 118 ( or 76 (hex)). Look for a hex value of 76 at location 824.
This is shown as 3.776 gal/hr, but 118/32 = 3.6875 gal/hr doesn't quite fit. However: 118 * 0.032 = 3.776 Bingo!.
I would simply scale up this value by the new injectors/old or 42/22 * 118 = 225 decimal or E1 (hex). The exact resolution? 0.032 or 1/32 (0.03125) doesn't really matter since this is a proportional change.
Last edited by tequilaboy; Aug 15, 2006 at 11:06 AM.
Race Director
Joined: Sep 2003
Posts: 16,838
Likes: 341
From: Database Error Indiana
If anyone wants a look at the ecu file send me an email and I will attach it to a reply. I could be reading the location wrong.
Wrightxx@sbcglobal.net
Wrightxx@sbcglobal.net
Thread Starter
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Looks like you guys have the right info to get me going. Unfortunately, I'm so tired tonight that my brain doesn't even want to coop. Too much time today trying to convert, merge & clean up a database in the County Assesors office... amazing how poorly end users can set up data structures, attempt to key the same data into 4 or 5 diff. tables & then can't figure out why the reports always have diff results... but then not say anything until 6 or 7 years worth of data has been input. duh
Thread Starter
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
And a BIG thank you to both Tequillaboy & Corvette91. Tested the new entry on my bin on the way to work today & it works great. Very close but I will continue to test/compare mileage & adjust as needed. 
Pro
Joined: Jan 2005
Posts: 686
Likes: 62
From: San Jose Ca
Hijack time! Since the thread appears dormant, I'll ask a related question. How does this apply to a '94. I've got 42lbs inj too and it kinda bugs me that the trip computer is now useless. I would LOVE to get it working properly. I'll always thought that the BCM had an inj constant in it too and just read the PW from the PCM along with the speed/distance. Anybody know what to do in my case? I've got both LT1 edit and Tunercat. Thanks!
Scott
Scott