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      05-13-2010, 06:08 PM   #1
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Drives: 4 Wheels
Join Date: Aug 2007
Location: Planet Earth!

iTrader: (15)

Fueling Resistors -- What Do They Do? Using This Data for Upgraded Turbos or Nitrous

Let me start by saying this is not going to be another one of my long winded reviews. LOL! My hope is this will turn into a valuable discussion, using real data, to discuss the fueling capabilities of the stock fuel system. All the testing you will see was done on a JB3 2.0 running Map 7 (~14 psi) and approximately 670 ml/min of water/methanol (~70/30). All the data was retrieved with an FJO wideband using high speed datalogging. Off nitrous, my car has an increase of about 150 rwhp over stock on a Mustang Dyno or about 165 rwhp on a dynojet. My car makes about 406 rwhp on a Mustang Dyno and about 445 rwhp on dynojet without nitrous.

Each tune has fueling resistors that determine how much additional fuel the tune can ask for. Why does this matter? Well on lower boost it is really not that important, but as you go to higher boost, race gas settings, nitrous, and ultimately upgraded turbos it will matter a whole lot. Through testing I am finding out what different fueling resistors will do. I want to present some of the data now for the community to look over.

5.5k Ohm Resistors

3.3k Ohm Resistors

2.2k Ohm Resistors

1.0k Ohm Resistors

Finally, a comparison between the 2.2k ohm resistors and 1k ohm resistors.

So what does that mean? Well you can see the lower the resistance on the fueling resistor the richer the car will run when the tune is asking for 100% fuel. You can also see that with the 5.5k ohm fueling resistor the car is aiming for an A/F ratio of 14:1 at 3000 rpms when asking for 100% fuel increase. With the 1.0k ohm fueling resistor the car is aiming for an A/F ratio of 12.5:1 at 3000 rpms when asking for 100% fuel increase. Up top with the 5.5k ohm fueling resistors the car is aiming for an A/F ratio of 12.5:1 at 6000 rpms when asking for 100% fuel increase. Up top with the 1k ohm fueling resistor the car is asking for 10.2:1 A/F ratio at 6000 rpms when the tune is asking for 100% fuel increase.

Those are the facts. Now why in the world would you want a rich A/F of 10.2:1 up top? You would not, but having the ability to richen up the mid rpms is tremendously important for upgraded turbos and nitrous. I am not sure how each tune works, but the JB3 can very easily swap fueling resistors on the board in about 20 minutes. It is easy work and clearly Terry was thinking of the future when designing the board this way. What this means is Terry can design an alternative set of maps for the 1.0k ohm resistors and allow us to run a much richer mid rpm and just ask for less than 100% fuel up top to keep the 12.0:1 - 12.5:1 ratios. On a low boost car, the DI clearly can handle the 14.0:1 A/F ratio without knock, but on nitrous or upgraded turbos that is just too lean for my taste. Terry is in the process of making the A/F adjustments for 1.0k ohm fueling resistors as I suspect a lot of people will be changing over with the introduction of nitrous and turbo upgrades.

One other thing that is very important to note is that this will give us REAL insight into the capacity of the N54 fueling system. Clearly at appoximately 445 rwhp on pump, the car has a lot of fuel left of it would not show such a huge difference between the 2.2k ohm resistor and 1.0k ohm resistor. I will be testing more and more nitrous to find out when the car cannot maintain A/F ratio and we will find the real limits of this fuel system rather than speculating. I was not going to run more nitrous until we were able to sufficiently richen up the mid rpms, but now with the 1k ohm resistors we have it where it needs to be. Once Terry leans the top from 10.2:1 up to around 11.5:1 then my testing with more nitrous will begin. Thus far I have made 487 rwhp on a Mustang Dyno with a 35 shot (.031 jet) or 526 rwhp dynojet equivelant on pump gas. I hope to make a little more shortly. I will hopefully test the limits of the stock fuel system on pump, then see what power we can make on MS109.

I have a lot of other thoughts, but I wanted to open this discussion. I have monitored fuel pressure during the testing as well, so I will now be able to comment with direct knowledge on how fuel pressure changes with increasing fuel demands. Anyone that wants to go this route on the JB3 (once Terry finishes the tune for the 1.0k ohm resistors) can simply change out the fueling resistors. I think this is going to be the future especially for the guys upgrading turbos and using nitrous. This will give you a whole lot more headroom and a lot more safety especially considering the N54 is a DI motor in my opinion.