Pump Calibration Resistors

[Jochen Woern]

While installing a new Remote Mounted PMD/FSD, I used the #5 resistor as recommended by Kennedy Diesel with their Deluxe FSD Cooler Package.
(Unfortunately, I was not able to figure out what # the original resistor on the original PMD was).

Questions:
- Will the power of my truck increase if I install the #9 resistor?

- Will a different resistor throw me any codes?
(Truck is operating fine right now, but it almost appears as if it is a bit slower off the get go than before installing the new PMD/FSD. Could however be my imagination???)

- Can anyone explain what the different #'s on the resistors mean and what difference they will provide in regards to performance?

Many thanks in advance.

[DA BIG ONE]

The members area has all this information. You can use a small mirror w/extension handle to see value of resistor might need a flashlight too to reflect off mirror into opening where resistor is.

[Kennedy]

People spend way too much time fretting about this. If you click on the title of the item (Calibration resistor) on my site you will find a detailed page explaining the operation.

http://www.kennedydiesel.com/detail.cfm?ID=135

[Jochen Woern]

Dear Mr. Kennedy,

Thank you so very much for your reply to my question. Unfortunately, not all of us spend as much time on our 6.5's as you are and maybe some of us are not as technically inclined when it comes to the subject matter as you are.

Believe it or not, I did read the detailed page explaining the operation of the Calibration resistor on your site. But, (and I am sorry to say), this was way too technical and overwhelming for me and therefore I asked the very simply questions which still are not answered.

My assumption is (after reading your site) that there is NO real difference in running a different resistor. However, I would like that confirmed (if it is not too much trouble).

So, I am asking the questions again, maybe you (or someone else) can answer them so the average guy like me can understand as well:

- Will the power of my truck increase if I install the #9 resistor?
- Will a different resistor throw me any codes?
- Can anyone explain what the different #'s on the resistors mean and what difference they will provide in regards to performance?

For all your troubles, I would like to thank you very much in advance.

[DmaxMaverick]

......So, I am asking the questions again, maybe you (or someone else) can answer them so the average guy like me can understand as well:

- Will the power of my truck increase if I install the #9 resistor?

Yes/no. Will you notice a difference? Very unlikely. Much depends on where your current fueling map is. If you are already fueling at the maximum power your engine will produce, there will be no increase in power, but fuel consumption and EGT's will increase, due to the additional fuel injected. Any increase you are able to produce will only be realized on instrumentation (EGT increase) or a dyno, if at all. The maximum possible power increase will not be impressive. At most, fuel will be increased about 5% between the minimum and maximum resistors, and % fuel increase does not equal power increase. Power increase % will be less than fuel % increase. Maximum fueling volume only occurs at WOT (Wide Open Throttle), and has no effect at less than WOT.

- Will a different resistor throw me any codes?

Possibly. This depends on your current fuel map and PCM parameters. If the PCM is currently commanding fuel and is calibrated for your current resistor, at or near the PCM maximum envelope, then increasing the resistor value will set code 56. If a DTC 56 is present, then the PCM will command fueling at a level equivalent to resistor #1 (minimum calibration fueling).

- Can anyone explain what the different #'s on the resistors mean and what difference they will provide in regards to performance?

Resistors are numbered from 1 to 9. 1 being the lowest fuel calibration, 9 being the highest. Each number increment increases maximum fuel volume by .5 mm3 (1/2 cubic mm). A higher number allows for a higher maximum fuel volume delivery at WOT. Increasing the resistor number will increase the PCM's maximum fuel delivery volume command. This does not necessarily translate to more power, only more fuel.


Clear as mud?

[JohnC]

I don't believe any valid resistor will cause a code to set.

The difference in fuel delivery is proportional to the difference between the correct resistor and the one you are using. If your pump requires an 8 and you put in a 9 then the difference is minimal, whereas if your pump is a 1 and you put a 9 you get the maximum change, about 4 mm3 which is about a 6% increase. Most pumps come in at 4, 5, or 6, so the average increase is a lot less.

Lastly, the PCM never looks at the resistor unless the value stored is lost, so, simply changing the resistor will likely have no immediate impact. The only reliable way I've found to make it read a new resistor is to force a TDC Offset Learn. If you have not done so, chances are your PCM is still running off the original value. (Hint: you can read the stored value with a Tech 2 and learn what it was...)

[Jochen Woern]

Thank you DmaxMaverick and JohnC. It is now indeed "clear as mud" and you are now talking my language.

Many thanks!