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Rather than make or use a box, I prefer just flashing to the 2002 OS and then using HP tuners to pull the timing whenever the N2O switch is armed. You can set how much timing to pull. Less wires, less chance of something going wrong.
Yep I use a relay and ground relay pins 30 and 85, and run relay pin 87 to pin R53 on the ECM, with pin 86 on the relay routing to the arm switch. (see relay #6 in diagram below)
150 shot so 6 degrees of timing is pulled.
Last edited by 5.7stroker; 10-12-2017 at 09:39 AM.
I'm running the "lil hoss" shot on NGK BR7EF plugs. Non projected at .028-.030 till I'm able to run with the big boys.
That's right, better get him to tune it for ya. You don't want it to last that long. I think one of the guys I race with has those e3 plugs in his and sprays it. I may be wrong but he has the sticker on his car for the contingency money.
That's right, better get him to tune it for ya. You don't want it to last that long. I think one of the guys I race with has those e3 plugs in his and sprays it. I may be wrong but he has the sticker on his car for the contingency money.
Yep I use a relay and ground relay pins 30 and 85, and run relay pin 87 to pin R53 on the ECM, with pin 86 on the relay routing to the arm switch. (see relay #6 in diagram below)
this sounds like the way to go but for the life of me I dont see relay #6 in the diagram
this sounds like the way to go but for the life of me I dont see relay #6 in the diagram
I had the wrong image up. Check it now, the relay 6 is on the left side, half way down. I should have done these diagrams with real software, not M$ paint.
I had the wrong image up. Check it now, the relay 6 is on the left side, half way down. I should have done these diagrams with real software, not M$ paint.
Dopeness! I thought I was going crazy for a few minutes, thanks
This mod is for those of you who want to retard the spark timing in your car while spraying nitrous but don’t want to give up that horsepower while on the street the other 99% of the time you aren’t spraying. Yeah you could buy a more expensive timing retard box that costs in the $275 range or you could do this mod for about $30. Your choice. I got the idea for this mod while tuning in my IAT Spark Tables for methanol injection spark advance. But like everything else, when I looked around online to see who else had thought of it of course somebody had already beat me to it so I guess I wasn’t the first with this bright idea. I notice that allot of people ask about these on here but not one has really posted a how to thread on what to do, so here you go.
Use this mod at your own risk. I will not be responsible for any wiring or tuning debacles you may put yourself in if you misuse the information in this post.
To understand how this mod works you need to first understand how the IATS (Intake Air Temperature Sensor) works and how it interacts with the ECU (Engine Control Module). Basically an IATS is just a thermally modified resistor (aka thermistor). At different temperatures that it encounters the sensor outputs a different electrical resistance (measured in ohms). The ECU outputs 5 volts on one wire leading to the IATS and measures the return voltage on the other wire coming from the IATS. The difference in voltage is in direct proportion to the amount of resistance the IATS causes but the ECU still needs to know how to interpret this. That is where the IATS Calibration Table comes into play that is in the ECU tune.
Here is an IATS Calibration Table from a 2009 Pontiac G8 GT. The tables for the GTO’s and other LSx vehicles look similar.
As you can see, different intake air temps are represented by differing resistance values. For the purpose of this modification we want to focus on the lowest temperature cell, which is -40*F in this case. Now we all know that short of a VERY few exceptions there is no one who will be driving their G8, GTO, or Corvette in -40*F weather so this cell is virtually useless for normal driving use. But we can use it for the purpose of retarding spark timing while spraying nitrous. Notice how the resistance value is 100,866 ohms. We will use that later in this writeup.
Now let’s move onto what the ECU does with this temperature data with regards to spark timing.
Below is your typical IAT Spark Adder Table. This one is from a 2009 Pontiac G8 GT but the ones in a GTO tune will look similar.
As you may have noticed, I have already modified the tune so that -4 degrees of spark is taken out at all cylinder loads in the -40*F cells in the IATS Table. Pretty simple, but there is one more item to change in the tune before you are finished.
Enter the IATS Spark Adder Multiplier Table. As always, this one is a G8 GT table but your GTO table will look similar, with a few small temperature cell differences.
This table will multiply whatever figures are present in the corresponding temperature cell of the IAT Spark Adder Table. In this case we know that we are requesting -4 degrees in the IAT Spark Adder Table across all cylinder loads. So at whatever RPM vs IAT cell I request a multiplier of 1.00 I will retard -4 degrees of spark advance out of the tune below what is already in the Base Hi/Lo Octane Spark Tables. If my multiplier is 0.50 then I will only be pulling -2 degrees at that RPM. Most people start spraying at around 3,000RPM’s so that is what this example is setup to represent. I like to feather spark changes in and out gradually to keep things smooth so that is why I am already requesting that 50% of the IAT Spark Retard be taken out in the 2,500RPM cell.
Now what we have accomplished is setting up the tune so that it only pulls spark advance when it senses -40 degree IAT’s and only from 2,500RPM’s on up. Yes the ECU will also interpret the cooler aircharge as a more dense one and will want to add a bit more fuel to compensate. But you will want to use a richer WOT AFR anyways, so that won’t really be a problem because you will be jetting your wet nitrous system to enrichen WOT AFR’s anyways.
Now onto making the Timing Retard Box.
First off is a list of parts that will be needed:
• Radio Shack plastic “Medium Small Project Box” x1
• Relay, 12VDC, 5 pin automotive relay x2 (<----Make sure these are 5 pin with pin #87a)
• Resistor 0.5 watt, 100k Ohm x1
• Resistor 0.5 watt, 5k Ohm x1
• Electrical Spade connectors, ¼” x 18gauge x10
• Relay Harness pigtails x2 (this is optional and would replace the 10 ¼” spade connectors above)
• Wire, 18gauge various colors x10’
• Solder
• Heat Shrink Tubing Small and Large sizes
• Grommet, Rubber roughly 3/16”-3/8” x1 (Size of grommet depends on size of wire you go with)
• Zip Ties, Small x5
Total Price: $30
Tools Required:
• Basic Wiring Tools
• Digital Multimeter (<----Not 100% needed but helpful for testing resistance, voltage, and connectivity)
• Heat Gun or Hair Dryer
• Soldering Iron or Gun
• Drill and Drill bit
• Philips Screwdriver
Continued...
Where do you put the 5K .5watt resistor? its not in the illustration. Trying to build this for my 2000 Silverado 5.3
Looking at installing 150 shot over the winter and I like this idea the best from I have read. Has anyone else used this method and how did you turn out?
Yes, it works. All you need is a relay and HP tuners and your ECM flashed to 2002, because the older years don't have the menu option within HP tuners to pull timing by the traction control method. Yes, you will have to use 2 more credits within the HP tuners software as it will consider the 2002 flash as a different vehicle.
Yes, it works. All you need is a relay and HP tuners and your ECM flashed to 2002, because the older years don't have the menu option within HP tuners to pull timing by the traction control method. Yes, you will have to use 2 more credits within the HP tuners software as it will consider the 2002 flash as a different vehicle.
Awesome mine is a 2002 already so I'm good. What if my car doesn't have TCS? I can still access it in the ECM correct?
My 2000 had TCS but I completely removed it and pulling the timing still works fine. You should not have an issue. Your ECM should still have a wire going into pin 53 on the red ECM and that's the one you tap into. The wiring diagrams that I made and screenshots of the software are here:
Grounding pin 53 will pull the amount of timing in the traction control retard tables. There are a few other things that need to be setup as well like the maximum runtime... it needs to be maxed out to 410 seconds. This will keep the PCM from tripping a code and disabling traction spark retard.
My 2000 had TCS but I completely removed it and pulling the timing still works fine. You should not have an issue. Your ECM should still have a wire going into pin 53 on the red ECM and that's the one you tap into. The wiring diagrams that I made and screenshots of the software are here:
Grounding pin 53 will pull the amount of timing in the traction control retard tables. There are a few other things that need to be setup as well like the maximum runtime... it needs to be maxed out to 410 seconds. This will keep the PCM from tripping a code and disabling traction spark retard.
10-09-2017, 08:10 PM
