Holley HP EFI
Advanced
Joined: Jun 2018
Posts: 50
Likes: 5
From: Springfield Mo
For an 89, you won't have any real issues except the instant/average fuel economy, and the "miles to go" won't work.
The 84-89 "Atari Dash" is self contained. The signal from the VSS sensor on the transmission VSS is fed directly to the Cluster. I believe there is a "VSS output" single wire, probably brown, that sends speed info to the ECM. The ECM uses speed for several computations. You should be able to use this output from the cluster as a speed input to the Holley. If for some reason you need to input raw VSS to the Holley, youu should be able to tap the VSS wires (pur/wht and lt grn /blk) going to the cluster for the Holley. If "Y-ing" the VSS doesn't work, Dakota Digital makes VSS buffers that will solve the problem. About $85 last time I checked.
EDIT / ADD: I see your screen name includes FX3. The FX3 also uses the pur / lt grn VSS pair for speed input. So I would suggest rather than mess with the raw VSS signal prior to the cluster / FX3, use the existing speed output from the cluster for the speed input to the Holley. You may have to futz with it a bit to get the Holley input configured properly, but I know this can be done. IIRC, the cluster outputs 4000 pulses per mile. An excellent resource for VSS information is Jags That Run. They have an excellent piece on their website regarding VSS for engine swapping.
Note that I used the word "should" several times. I know what I'm talking about, but I have never DONE the things I mentioned. That's why "should". But the take-away is that the 84-89 Inst Cluster won't present any un-solvable issues when used with a Holley for engine management. Go for it.
The 84-89 "Atari Dash" is self contained. The signal from the VSS sensor on the transmission VSS is fed directly to the Cluster. I believe there is a "VSS output" single wire, probably brown, that sends speed info to the ECM. The ECM uses speed for several computations. You should be able to use this output from the cluster as a speed input to the Holley. If for some reason you need to input raw VSS to the Holley, youu should be able to tap the VSS wires (pur/wht and lt grn /blk) going to the cluster for the Holley. If "Y-ing" the VSS doesn't work, Dakota Digital makes VSS buffers that will solve the problem. About $85 last time I checked.
EDIT / ADD: I see your screen name includes FX3. The FX3 also uses the pur / lt grn VSS pair for speed input. So I would suggest rather than mess with the raw VSS signal prior to the cluster / FX3, use the existing speed output from the cluster for the speed input to the Holley. You may have to futz with it a bit to get the Holley input configured properly, but I know this can be done. IIRC, the cluster outputs 4000 pulses per mile. An excellent resource for VSS information is Jags That Run. They have an excellent piece on their website regarding VSS for engine swapping.
Note that I used the word "should" several times. I know what I'm talking about, but I have never DONE the things I mentioned. That's why "should". But the take-away is that the 84-89 Inst Cluster won't present any un-solvable issues when used with a Holley for engine management. Go for it.
Thank you so much for the "Jags That Run" Suggestion. I will pick that up. I am currently gathering information now to do this properly. I also have the books " "Chevy TPI Fuel Injection Swapper's Guide" by John Baechtel and "Fuel Injection- Installation, Performance Tuning and Modifications" by Jeff Hartman On order heading my way.
I think there has to be a way to keep the Stock ECU for the Average MPG or emulate speed and injector width to either send that signal back to the ecu to get that calculation to the dash to keep that gauge. Also I will likely keep the stock ecu for the FX3 calculations as well but will likely have to send it signals to trick it into thinking it is still operating the engine. The Dominator ECU is pretty powerful I think I can make it work. So things like tach signal, pulse injector width, VSS and so-on can be sent to the stock ECU. That is the hope.
Keeping the FX3 is a must. This is a first year option and is very rare to find for 89s. It was a huge selling point for me. I cant loose it.
Last edited by Red89FX3; Aug 9, 2018 at 02:16 PM.
Melting Slicks
Joined: Aug 2003
Posts: 3,393
Likes: 392
From: Lakeville MI
Examples from $32B:
MW2 DETAIL (L0035):
;
; Bit 0 = 1= OVERDRIVE ON; 0= OVERDRIVE OFF
; 1 = ERR 14 or 15 THIS STARTUP
; 2 = REF PULSES OCCURRED (6.25 MSEC CHECK)
; 3 = 1= ALDL MODE, 8192 LOCKED IN, & MODE 4
; 4 = DIAGNOSTIC SWITCH IN DIAGNOSTIC POSITION
; 5 = DIAGNOSTIC SWITCH IN ALDL POSITION
; 6 = HIGH BAT. VOLT. , DISABLE SOLENOID DISCRETS
; 7 = SHIFT LIGHT (1= ON, 0= OFF)
;---------------------------------
;-------------------------------------------------
; >>> Serial Data Tables & Params <<<
;--------------------------------------------------
LC703 FCB 4 ; Dis String length, (Bytes)
********************************
* DIS ADDRESS'S , XMIT
********************************
LC704 FCB $C009 ; Num O cyl Addr
LC706 FCB $011A ; Running total of fuel supplied Addr
LC708 FCB $011E ; Running total of Dist. Traveled Addr
LC70A FCB $C712 ; Gal's/Sec Scale Factor Addr
LC70C FCB $0000 ;
LC70E FCB $0000 ;
LC710 FCB $0000 ;
LC712 FCB 122 ; Gals/Hr Inj flow rate
; Num = Arg * 32, (3.8125 G/Hr)
I've attached an adx file that I created for logging the dash data and also included a sample log file in the zip if anyone is interested in logging or viewing dash data.
Note: My display constant is set to the maximum value of about 8 gallons/hr due to 63 lb/hr injectors. For better accuracy, I would need to set this value to 10.5 gallons/hr if it were possible.
Note 2: The distance signal has a resolution of 0.0005 miles per bit (1/2k ppm), so just multiply the raw signal by 0.0005 to see actual distance in miles.
Last edited by tequilaboy; Aug 11, 2018 at 01:46 PM.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Last edited by scorp508; Aug 10, 2018 at 05:12 PM.
Advanced
Joined: Jun 2018
Posts: 50
Likes: 5
From: Springfield Mo
Under normal mode (without 10k resistor), the 165 ecm transmits 5 bytes at 160 baud which is used by the dash to calculate fuel economy and also to display the shift light and O/D on/off status depending upon year and trans type. The 5 bytes are: MW2 (which includes the shift light and O/D or cags status flags), number of cylinders, accumulated fuel, accumulated distance, and the injector display constant. The calculation is apparently done in the dash with the serial data input.
Examples from $32B:
MW2 DETAIL (L0035):
;
; Bit 0 = 1= OVERDRIVE ON; 0= OVERDRIVE OFF
; 1 = ERR 14 or 15 THIS STARTUP
; 2 = REF PULSES OCCURRED (6.25 MSEC CHECK)
; 3 = 1= ALDL MODE, 8192 LOCKED IN, & MODE 4
; 4 = DIAGNOSTIC SWITCH IN DIAGNOSTIC POSITION
; 5 = DIAGNOSTIC SWITCH IN ALDL POSITION
; 6 = HIGH BAT. VOLT. , DISABLE SOLENOID DISCRETS
; 7 = SHIFT LIGHT (1= ON, 0= OFF)
;---------------------------------
;-------------------------------------------------
; >>> Serial Data Tables & Params <<<
;--------------------------------------------------
LC703 FCB 4 ; Dis String length, (Bytes)
********************************
* DIS ADDRESS'S , XMIT
********************************
LC704 FCB $C009 ; Num O cyl Addr
LC706 FCB $011A ; Running total of fuel supplied Addr
LC708 FCB $011E ; Running total of Dist. Traveled Addr
LC70A FCB $C712 ; Gal's/Sec Scale Factor Addr
LC70C FCB $0000 ;
LC70E FCB $0000 ;
LC710 FCB $0000 ;
LC712 FCB 122 ; Gals/Hr Inj flow rate
; Num = Arg * 32, (3.8125 G/Hr)
I've attached an adx file that I created for logging the dash data and also included a sample log file in the zip if anyone is interested in logging or viewing dash data.
Note: My display constant is set to the maximum value of about 8 gallons/hr due to 63 lb/hr injectors. For better accuracy, I would need to set this value to 10.5 gallons/hr if it were possible.
Note 2: The distance signal has a resolution of 0.0005 miles per bit (1/2k ppm), so just multiply the raw signal by 0.0005 to see actual distance in miles.
Examples from $32B:
MW2 DETAIL (L0035):
;
; Bit 0 = 1= OVERDRIVE ON; 0= OVERDRIVE OFF
; 1 = ERR 14 or 15 THIS STARTUP
; 2 = REF PULSES OCCURRED (6.25 MSEC CHECK)
; 3 = 1= ALDL MODE, 8192 LOCKED IN, & MODE 4
; 4 = DIAGNOSTIC SWITCH IN DIAGNOSTIC POSITION
; 5 = DIAGNOSTIC SWITCH IN ALDL POSITION
; 6 = HIGH BAT. VOLT. , DISABLE SOLENOID DISCRETS
; 7 = SHIFT LIGHT (1= ON, 0= OFF)
;---------------------------------
;-------------------------------------------------
; >>> Serial Data Tables & Params <<<
;--------------------------------------------------
LC703 FCB 4 ; Dis String length, (Bytes)
********************************
* DIS ADDRESS'S , XMIT
********************************
LC704 FCB $C009 ; Num O cyl Addr
LC706 FCB $011A ; Running total of fuel supplied Addr
LC708 FCB $011E ; Running total of Dist. Traveled Addr
LC70A FCB $C712 ; Gal's/Sec Scale Factor Addr
LC70C FCB $0000 ;
LC70E FCB $0000 ;
LC710 FCB $0000 ;
LC712 FCB 122 ; Gals/Hr Inj flow rate
; Num = Arg * 32, (3.8125 G/Hr)
I've attached an adx file that I created for logging the dash data and also included a sample log file in the zip if anyone is interested in logging or viewing dash data.
Note: My display constant is set to the maximum value of about 8 gallons/hr due to 63 lb/hr injectors. For better accuracy, I would need to set this value to 10.5 gallons/hr if it were possible.
Note 2: The distance signal has a resolution of 0.0005 miles per bit (1/2k ppm), so just multiply the raw signal by 0.0005 to see actual distance in miles.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
So do you think it is possible for an ECU like a holley Dominator ECU to send a similar signal to the dash to emulate the stock ecu? Sounds likely. And this would be the updgrade I am looking for. Would give ultimate tuneability with any cam or displacement I wanted, plus keep my retro 80's driving feel.
- 20 high side (+12V) PWM or switched outputs
- 16 low side (ground) PWM or switched outputs
Without some creative thinking I'm not sure how to get total fuel delivered and a miles driven sent to the dash. Someone good with Raspberry Pi could probably get a serial stream going to the das, but there's still the need to get information out of the Dominator and sent somewhere else. Holley uses a CAN bus between their ECMs and digital dashes, but don't publicly document the protocols they use. Racepak apparently has a loose partnership of some kind with Holley to read their CAN bus protocols, but I'm not sure if that'd buy us anything.
Advanced
Joined: Jun 2018
Posts: 50
Likes: 5
From: Springfield Mo
I kind of doubt it from what I've read about the Dominator's extra output channels it comes with..
- 20 high side (+12V) PWM or switched outputs
- 16 low side (ground) PWM or switched outputs
Burning chips on my 89' really limits my cam shaft selection and tuning ability.
Plus NOBODY tunes OBD1's
Last edited by Red89FX3; Aug 12, 2018 at 12:03 AM.
Le Mans Master
Joined: Feb 2005
Posts: 6,477
Likes: 565
From: Clearwater Florida
..... Call Holley's tech line @ 270-781-9741 or go to www.holley.com and click on support and search the forums …..
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Advanced
Joined: Jun 2018
Posts: 50
Likes: 5
From: Springfield Mo
I am convinced I can keep the stock ECU to operate all the fuel calculation dash functions. The stock ECU only needs to “see” all of its inputs to believe it is operating an engine. I can give the stock ECU all of its parameters from additional sensors or from the Holley ECU. Then the stock ECU will just interface with the dash like it always have. All the while using the Holley Dominator to actually control fuel and spark. My car is a ZF6 with manual A/C controls. This can’t be that complicated.
And yes I understand it’s just one gauge (Technically 3 gauges but only one that will look dead). And I suppose it’s not a deal breaker. But I really really want the dash to function properly. Dead gauges just scream “rigged” to me. This car is clean, and that’s all part of the driving experience.
Thank you you everyone for the feedback.
And yes I understand it’s just one gauge (Technically 3 gauges but only one that will look dead). And I suppose it’s not a deal breaker. But I really really want the dash to function properly. Dead gauges just scream “rigged” to me. This car is clean, and that’s all part of the driving experience.
Thank you you everyone for the feedback.
Last edited by Red89FX3; Aug 12, 2018 at 10:02 PM.
Pro
Joined: Apr 2001
Posts: 744
Likes: 13
From: Lenoir City TN
..... I've been using Holley EFI stuff forever … started with the Commander 950 , which is a perfect set-up for early EFI cars like ours … am now using the Dominator … Buy the Holley harness and let the HP control what it needs to run the engine … the HP will control all ignition functions including DIS (distributor-less ignition systems) and CNP (coil near plug) and will control timing via knock sensors … fully lap top tuneable or use a touch screen for more basic set-ups … your only regret will be not having done it sooner …..
Le Mans Master
Joined: Feb 2005
Posts: 6,477
Likes: 565
From: Clearwater Florida
….. Just to be clear … the 950 is not self tuning , the HP is … And , no it will not self tune the timing maps , that needs to be done manually … it is knock sensor capable ! …..
Burning Brakes
Joined: Dec 1999
Posts: 983
Likes: 152
From: Columbia MD
Under normal mode (without 10k resistor), the 165 ecm transmits 5 bytes at 160 baud which is used by the dash to calculate fuel economy and also to display the shift light and O/D on/off status depending upon year and trans type. The 5 bytes are: MW2 (which includes the shift light and O/D or cags status flags), number of cylinders, accumulated fuel, accumulated distance, and the injector display constant. The calculation is apparently done in the dash with the serial data input.
Thanks for posting this. I've been curious about the contents of the 5 byte data packets that feed the instrument cluster. I've written an Arduino Sketch that decodes the 160 Baud ALDL data packets and now I have the info I need to decode the instrument cluster data packets. Cool stuff.
-Wes