That trick of transforming the GM High Octane and Idle Spark tables into Holley EFI format has been my pot of gold at the end of the rainbow. I cannot express how much better the car drives now! Years of frustration melting away in one moment of success. Credit goes to quarterbooty at the Holley EFI forum who shared his tune with me as a working example. I'm going to pay forward by explaining this so maybe it helps others struggling with the same kind of issues of engine bucking at low load, low rpm.

Bottom line is GM has stuff figured out... so use it. The general concept is to use the GM High Octane Spark table as your base timing table in the Holley EFI software, and to create another custom 2D table that will carry values from the GM Idle Spark table. These two tables blend together to create spark tables that make the car drive well. But first the GM data has to be transformed because it is not directly portable into Holley EFI formats. The attached spreadsheet (see attachment below) takes the Air Mass from a GM LS7 tune and transforms the data into a format that can be used with Holley EFI. Some little fixes are needed to smooth the table but most the work is done for you. How awesome is that?!?!

GM uses drive-by-wire so I had to make some adjustments for my cable throttle body. My custom 2D table is Timing Offset [°] as a function of RPM and TPS. I already knew from prior work what timing my engine wants at 0% TPS, so I dialed that into the 2D table and I was done. That allows my timing to follow the "High Octane map" (Holley base timing map) any time throttle is >0%. This literally made the buck all but disappear. Seriously.... it was that easy. And I was never going to be able to do this with just the base timing table because there is no crisp line of transition between 0% and 1% throttle, which my engine gets real finicky about.

Here is my 2D custom table with cable throttle body. So incredibly simple it almost hurts to think about all the crazy things I tried in the past. But truth is I just didn't know and I got a lot of bad advice from other people too. I hope this cuts straight through the BS so somebody else doesn't struggle for years like me.

 

Another lesson learned studying the GM LS7 tune.... I added a custom 1D table for cranking fuel compensation when fuel pressure is low. It has helped a lot with crank times - especially consistency from start to start. I normally would "key on" and wait for fuel pump to prime (get to operating pressure) and then crank engine. This works really well during cold start, but warm restarts have always been finicky with longer crank times and sometimes I need to clear flood to get started (a lean crank can cause a flood when fuel won't burn).

Crank times have tightened up and the engine fires pretty darn quick now that I have fuel pressure compensation. I've even rolled straight through to crank position without letting pump prime and the engine is starting waaaaaaaaay quicker than before. I haven't had to clear a flood yet either.

I wasn't quite sure what is best curve to use. I ended up trying a method using Boyle's Law to calculate how much extra injector opening time was needed to maintain constant fuel volume vs. rail pressure. Maybe not the best method but I think it got me in the ball park. The table below is based on a 58 psi fuel system. I clipped it at 200% because the numbers go crazy high as it approaches 0 psi fuel pressure and I didn't want the injectors going wide open during crank.



Update: Another method that I am trying is the fuel flow rate change calculation at, https://www.rcfuelinjection.com/technical. It results in lower fuel compensation values with changes in fuel pressure.

New Flow Rate = (Old Flow Rate) * SQRT(New Pressure / Old Pressure)

The value of the square root is the fuel rate change multiplier with pressure change. And the inverse of that value is the correction factor needed to maintain constant fuel flow rate with changes of fuel pressure. To be usable in Holley EFI, that inverse value has to get reformatted into a percent change relative to normal fuel pressure. All told it looks like this when implemented in a 1D custom table at 58 psi normal pressure,

 

I too have similar issues and my tuner said he would adjust my fuel prime table from the factory 2 seconds to whatever I feel necessary. However, when warm I am not sure how the stock ECM handles it. I assume this is a benefit of running the Holley system vs GM.

 

You have enormous accessibility to tuning parameters with the stock ECM as well. One of the things I learned through this process is the moment you build a custom engine you also unwittingly sign up to be a part-time tuner. It's inevitable that you're going to have to buy HP Tuners and work on your drivability. A shop doesn't get the seat time in the car to work out all the issues and there isn't enough money to pay them by the hour.

Don't fight against your destiny.... Buy HP Tuners.

 

Deep down I know this to be true. I have a few more week links to iron out before I pony up for HP tuners. Car has minimal tuning issues at the moment. It has severe noise, rear suspension and tire rub issues, lol.

 

Yep, still a project car. Just one that's driving now.

 

I've worn myself out researching bulkhead connectors trying to figure out how to pass a Holley EFI harness through the passenger side kick panel (yes, it's as boring as it sounds). That darn space in the kick panel is not as roomy as it seemed at first.

I want to clean up my engine harness and make it really nice with a proper sealed bulkhead disconnect. Right now I have a Holley HP ECM but that idea morphed into dreams of growing into a Holley Dominator ECM. However, I just don't have the real estate to mount two Deutsch HD30 (Size 24) disconnects needed to take advantage of the Dominator, unless I eliminate the radio antenna. Now I understand why people use the teeny tiny Autosport connectors, but that's more money than I want to spend for a hobby.

So.... back to what can I do? Well, the other connector at my disposal is a Deutsch DRB 60-pin connector and it has just enough capacity to fully support the Holley HP ECM that I currently use in my car. I've also worked out a solution where I could add a second WBO2 sensor (with Dominator ECM) if I move a few wires to interior of car and pass a couple more through C100. And I've worked out a third solution where I can get dual WBO2 sensors entirely in the 60-pin bulkhead if I abandon the shielding of Cam and Crank speed sensors.

I'm not done yet trying to sort out how to use the twin 47-pin circular connectors. That would do everything I want and set me up for expansion in the future. Trick is just finding the real estate to mount it, or possibly moving my radio antenna somehow. All in all this little idea to clean up my harness is starting to sound like a bigger job than maybe I want to sign up for....

 

why add another connector vs just having the engine wiring harness pass through the kick panel hole and connect to the holley hp? that is what i did when i had my hp mounted in the OEM location before i ripped out the holley system due to the software issue they had with the hei ignition system... i made my own harness starting with their custom loose length harness kit and it worked out great. more connections just lead to more problems if you don't need them

 

I want it sealed off, truly water tight because the window cowl drain is directly above the harness and water will trace down the harness into the interior. Right now I avoid driving in rain and I stuff the hole with a towel when I wash the car.

And I'm being a bit **** too.

 

How many wires need to pass through... have you counted?

I have used these where the original Pass Through (Inseparable) goes, with the Square-Hole cleaned up to fit:


Sealed Metri-Pack 78-Way Connector:
-Two 46A Circuits.
-Twelve 30A Circuits.
-Sixty Four 14A Circuits.

Otherwise... I like the stupidly expensive Deutsch AutoSport or Amphenol Connectors.

No luck with the Deutsch HD30 Connectors from Maven Speed?

 

As in the industrial style Amphenol connector? A quick search turned up the typical "military" spec but I also saw some similar to a metri-pak or equivalent.
I'm asking out of curiosity not necessity.

 

If you have seen what the Deutsch Autosport Connectors look lilke...
I am referring to an Amphenol Connector that looks almost identical (not terribly different from some of the Mil-Spec Connectors that you saw):

Deutsch and other Companies have more or less just copied these.

 

not to try and discourage you from the connector, but if you want to make it watertight with the wiring just passing through you can use a grommet like this from speartech and even injected with silicone if you wish. this grommet actually fits pretty well in the hole as is and you can pack around it with the typical sealing putty or even better make a plate that seals to the kick panel hole and have a perfect fit

http://www.speartech.com/product_p/grommet.htm

 

Definitely interested. What's the part number on that sucker?

Edit: I found it

 

Here ya go!

 

The Metri-Pack 280 Terminals used here are NOT Tangless.

 

That thing is pretty wide. Do you lop off the ears of that sliding shroud and just let the clamped connectors hold it to sheet metal? Are there seals to the sheet metal (don't see any in the pictures)?

 

I do remove the Flanges...
Once the Sheet-Metal Fitment is very close to Component "F", I use Body Shop Seam-Sealer to hold and Seal to the Body.

 

That Delphi 78-pin junction does the job from a wiring perspective. It can do everything I want with 9 slots left over for future expansion. The best part though is that it can pass thru the ECM main power B+ and B- (10 AWG) --- Yay! I was going to have to pass those big wires through C100 before you showed me this option. I went ahead and ordered up parts for closer inspection.

Unfortunately my pile of bulkheads is growing which is unfortunate to my wallet. But sometimes you just gotta get stuff in your hands to see how it's really going to work out. If I don't do Deutsch connectors then all the Deutsch specific tools and parts I bought were pointless.

 

Awesome!

I like that 78-Way Bulkhead for that use case.
and I usually replace the C100 with a 38-Way Bulkhead:


34 of 30A Circuits, and 4 of 46A Circuits.


It has an optional fully flanged passthrough that I use:

 

Guessing you install it vertical lengthwise too? Looking too long to install horizontal.

 

Installing the Bulk-Head in the area of the original Pass-Through; works best by:
-Cutting the Original Rectangular Passage/ Hole to size (for the Connector Body) in the Body.
-Create a new sheet-metal Veneer to be welded over original Body/Material.
-Rotate Connector Body 90* Degrees from Original Orientation (for proper fitment, using original Hole).
-Size and mate the Connector Body and Veneer.
-Paint and seam-seal as needed for weather/ water ingress.

 

Not again...
Piece of crap 1980's GM.

 

Had to pull the Top Down Solutions new one too after just a few years. Gear broke. Motor was always slow as molasses. I wish somebody offered a manual latch to replace these electric latches.

 

That's crazy, had my car for 30 some years, all I've replaced are the guides and clear motor/gear housing. 20 plus yrs ago

 

Ugh. I lost my head a few weeks ago, hurried and slammed my hatch pretty hard on the motor. First time since the rebuild. I usually treat it like it's made of egg shell, which it sort of is. So far, it's still working.

 

LOL!!!

 

I have a junk yard hatch motor housing, no motor and the latch part is tack welded in place. The remote trunk release works great, with no motor or gears to worry about, may have to shut it with some effort to latch but its effectively a manual system now.

 

I'm of the mind to ditch my pull down mechanism before I'm stuck. Considering my Coupe is pretty much a stripped down model complete with crank windows and manual door locks, I see no need for the "fancy" pull down.
That said, I've 3 or 4 in reserve should that happen. There may even be a plan to ensure that these are all functional and sell them.

What's your plan now QwkTrip?

 

I must be one of the few people here who uses the "Pull Down" Motor all the time...
And have it be all original (never touched)!


I used to go to a small 3D Printing Shop in Manhattan to have replacement Parts made for my Customers...
Too bad that guy went out of business during SARS2.

 

My 1st car was an eight year old 68 Beaumont. Such extravagance didn't exist so I guess it's somewhat ingrained into my car approach. Less to go wrong (right QwkTrip?).
Hell, that first engine ran with one +12v wire and one fuel line...OK. Maybe a couple of wires. But simplicity it was.

 

in the past before i would fix the motor i would lock the broken one in an intermediate position. this allowed for reasonably easy latching but didn't put a ton of stress on slamming the hatch and its glass... this is a balance of how much force vs sealing affect you want. i do have one of my 3rd gens that came from the factory with just the mechanical latch vs the pull down... these are welded in so not a quick bolt in if you go get one from the junk yard

 

I stockpiled the Standard (Non-Motorized) Latches years ago... I wonder what the hell I did with all of them...

Probably went in the Trash with soo much other Third-Gen Stuff.

 

I can relate.

 

I temporarily swapped in an old gear that I had from another motor. Temporary will probably become permanent until next time. I have some parts on order to fix my other motor to have as a spare. Basically keep rotating stock.

Interesting idea, thanks!

 

Do you have the 3D model? My buddy has a 3D printer.

 

Unfortunately no.

I did not design the Model either... the Business that I used took care of it for me.

 

GM did. i believe they were in 82-85 cars.
fully manual version:
https://www.ebay.com/itm/35395470754...SABEgJ8Z_D_BwE

and i believe a power release version:
https://www.ebay.com/itm/11550657097...SABEgLCFPD_BwE

 

Are the OE style hatch motor gear housings still made? All I find are the Cadillac style with the smaller motor. I want to keep my old motor that is more powerful.

 

Bump the Voltage.
It's not like you have never done that before (boost-a-pump or window-racer).


These OLD Amperage hungry Parts are very happy at 14.5V (compared to 12.5V) let alone 16V.
Do not skimp on wiring as overall Wattage should still go up some even with Amperage dropping.

 

Hmmm.... I actually have a Boost-A-Pump laying around.

Got my spare unit completely rebuilt, cleaned, everything inspected and tested individually. Had to move those nylon sliders around several times until I found the magic sequence that fits best in the tracks. Now that I've completely gone through one from top to bottom (literally every piece), I'm going to do the same to the one in my car and get it all tuned up, maybe give 'er some boost.

 

Curious what you see the best way of bumping the voltage being @vorteciroc ?

 

I would recommend an off the shelf solution like a "Window-Racer" or a "Boost-a-Pump".
(I do NOT recommend going DIY).

Unlike AC to DC rectification...
Stepping up DC to DC Voltage is a VERY inefficient (and comparably difficult) Process.

 

Starting to collect parts of a different kind. Here's a hint....

 

Going auto?

 

Because I really hope so.
Then I can rely on your R&D for my own development...!

 

Have you been having issues with the T56?

 

ANYBODY with Qwik's output is going to have problems with a T56. Face plated or otherwise bulletproofed. Eventually anyway. (Although I'll admit the Super Stock guys really run them for all they're worth).
But the latest generation of auto trans appear to be immensely capable of handling what you can throw at them. You, Mr vorteciroc, probably appreciate that more than most. (And here's hoping my GM supplied 5-pinion planetaries don't **** the bed ).

 

It will take a while though, it's a big project. I don't have anything in my car needed to support an auto trans.

 

Not the trans itself. Clutch and hydraulics have always been very high maintenance.

Car will drive better and be much quicker 0-60 mph with an auto.