Fuel delivery and Pulley page

Fuel Delivery

There has been a lot of discussion regarding fuel delivery and the TRD Supercharger kit. Many owners of automatic transmissions have reported severe fuel delivery problems (too lean at high RPM) based on testing. I believe that the fuel delivery for my 5 speed transmission application is sufficient. I base this belief on these facts:

1) My truck currently has over 105K miles. 94K of these miles have been with the Supercharger installed. I have taken my truck to the drag strip many times, I probably have over 100 1/4 mile passes on it. Also, I use my truck to tow a 16' enclosed trailer containing two drag motorcycles. I have never experienced any problems that would be expected with poor fuel delivery / supercharged application.

2) I did install a Kenne Bell Boost A Pump and found that the truck performs better with a low setting (like 15~17) at the dragstrip. If I increase the BAP setting (thus increasing fuel delivery potential) I loose performance. This indicates to me that sufficient fuel is making its way to the combustion chambers.

To be certain that I am achieving proper fuel delivery I initially thought a simple air to fuel meter would suffice. I purchased an Autometer and hooked it up to the front O2 sensor. After some investigation I have determined that most stock O2 sensors and simple air to fuel gauges are not accurate enough to make any kind of tuning adjustments. The reason:

1) Most O2 sensors are narrow band. They will only read air/fuel ratios from 14.3 to 15.3 (or so). This is a very narrow band if you consider that most engines will produce most HP around 12.5 to 1. The narrow band sensor can not read this air / fuel ratio.

The wide band sensor on the other hand will provide a linear output capable of air / fuel ratio readings from 10 to 1 (very rich) to 20 to 1 (very lean).

So what to do??? I believe there are a couple of options...

1) You can take your vehicle to a Dyno that employs an exhaust gas analyzer


2) You can spend some bucks and get a Wide Band O2 controller and sensor. The wide band sensor will provide a linear read out with minimal affect by exhaust temp's. I am in the process of deciding if it is worth the $ to own one if these devices but am leaning very heavy to "yes". I have researched Three models:

1) http://plxdevices.com PLX M200, 250 or 300. These units have some neat features like an interface to the Autometer LED gauge so you can get linear / accurate readout from a simple Autometer gauge. Additionally, it provides a narrow band output so you can just replace your stock O2 sensor with the wide band and then run the narrow output to your stock ECU. (I believe the FJO requires you weld in a bung to your exhaust pipe to accommodate a separate wide band sensor). PLX will introduce two new models to the market in OCT / DEC of 2003. The new units offer the less expensive BOSCH O2 sensor. The cost range is $300 ~ 550. These boxes do not offer any datalogging options at this time.

2) http://www.fjoracing.com/ FJO Enterprises. They offer many complete kits that include extensive datalogging capability. Their boxes are very professional and probably offer more options but the cost factor has turned me away.

3) http://www.innovatemotorsports.com/ Innovate Motorsports. They offer a very reasonably priced box that offers datalogging of air/fuel over time. The unit is fairly new to the market (June 2003) and they are still developing some of the options, which include: Aux input cables. Once the input cables are available, you can datalog up to 5 additional inputs and download to your PC. I decided to go with this unit, mine arrived this week and I plan to install it soon. The price is around $349.00


Basics on AFR & ECU operation


Some key points about Air/Fuel ratio (AFR): During easy cruising our stock ECU uses the stock Oxygen sensor (narrow band) to adjust the AFR to a target of 14.7/1. The reason is like this. At 14.7/1 (this means 14.7 pounds of air to 1 pound of fuel) the amount of air will combine with all of the available fuel. This is the best condition for the catalytic converter to do its job thus providing for a better environment.

For performance most tuners will agree the peak horsepower is achieved with an AFR of around 12.5/1, So .. compare 12.5/1 to 14.7/1 you can see there is less air, which means the mix has got more fuel = Rich.

As mentioned above, our stock ECU tries to get the mix at 14.7/1 during easy cruising. The stock narrow band oxygen sensor is capable of reading 14.7/1 but not much more(or less). For example, a stock narrow band sensor will only read from around 14.3/1 to 15.3/1. The sensor can not understand an actual AFR under or over this range. So ... what happens when we mash it to the floor?

Well .. it is not so easy to explain in detail but in general this is what happens when we mash it: The stock ECU disregards the oxygen sensor readings and uses a fuel map to determine how to work the fuel injectors. The fuel map is just a table of numbers that an engineer has established to define the proper injector pulsing for a set of parameters. The parameters considered include: Intake air temp, Intake air flow, RPM, Throttle position and perhaps a few more. The stock ECU adjusts the injector pulsing according to the data in the fuel map. A simple example may be expressed like this:

The fuel map tells the ECU to pulse the injectors 10 times when ever the RPM is 1000, the air temp is 70, the throttle position is 25% open and the mass air sensor voltage is 1.25v.


Fuel delivery does relate to how well a smaller pulley will perform. As I stated above, I believe my fuel is being delivered properly ... but ... not completely convinced. At any rate, I did purchase a Pullyboys http://www.pulleyboys.com/ 2.2 for my truck. Unfortunately, my clutch is not cooperating and I can not determine how much it is helping me out. I do know this... the boost has increased per the gauge .. from a max of 7~8 with the stock pulley to 8.5~9.5 with the 2.2 pulley. I experience a little more spark knock at low RPM with medium load on the engine. I don't detect any other signs of too lean condition. The simple autometer shows two LED's above Stoch at full throttle but as you read above this could be BS (Bull shit).

I can sense an improvement in performance with the new pulley but as mentioned above, the clutch won't cooperate (I get great tire spin in first but when I bang second I get the same great spin but in the clutch). I also am experiencing a bit more spark knock with the smaller pulley.

To remedy the spark knock I purchased the FTC-1-017E fuel/Timing Calibrator from http://www.splitsec.com . I will use the wide band O2 meter to determine if fuel calibration is necessary but the main reason I got this box was to fix the spark knock.

The most difficult part of the install was figuring out where to put the box. Once I found the best spot the hook up was very straightforward and easy. This box provides three dimensional mapping of fuel and timing retard. A laptop computer is used to write the maps to the box. One note: the box provides an inherent 1.5 degree timing retard at all RPM when you install it. An additional 20 degrees of retard can be employed through the mapping process. I am still tuning and will post updates soon.


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