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Thread Title:

MAP Resistor Install Mod?

Created On Tuesday August 26, 2008 22:33

DBR64

Posts: 5
Joined: Jan 2008

Tuesday August 26, 2008 22:33

Question. I have read in other forums and I believe here as well but wasn't able find any related articles when I did a search.

My question is : I have heard that by installing a resistor in the MAP sensor you can improve the throttle response of the engine at the cost of a little smoke. So if this is true, which one of the 3 wires off the MAP sensor does the resistor go in and what OHM rating do you use? Actually any information on the subject would be greatly appreciated. Once again thanks. DBR CAT 3126

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Roadking

Posts: 6
Joined: Sep 2008

Wednesday September 17, 2008 15:56

Hi DBR,

I have heard that a 150 ohm resistor installed in line with the green wire on the map sensor will work well. Not sure what your engine is but I have spent a lot of time and research into C15 Cat's. I can tell you from experience that installing a potentiometer in the cab tapped into the green wire will allow you to adjust as you drive. I use it to vary boost response depending on GVM and also to cut back when I dont want all that attention from the black smoke pouring from my duallies! Be aware that there is a point at which the engine senses too much boost and will derate. If you see a check engine light when adjusting you have reached the limit of the pot's use. It takes about 2.3 seconds for the ECM to log a fault code so as soon as you see the check engine light back it off, mark that point as the max and you will have no problems. It will not give you extra horsepower but will give you instant boost response on the pedal as opposed to the computers delayed reaction, very handy for passing heavier rigs- when you pull out and punch it she goes! Here's another trick that will give you about 40 horses... Unplug the fuel temp sensor on the main fuel filter on the engine and put a 15k resistor across the plug. Put a piece of electrical tape over the end of the plug to cover the resistor and gently push back into the socket so it looks ok. This tells the ECM that the fuel is hotter than it is resulting in a much denser charge. Beware that a heavy right foot may cause some engine damage over time but if driven properly these tricks will not be detrimental to the engine in any way. If driven properly you will also see a notable decrease in fuel consumption. Hope this helps.

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droy

Posts: 12
Joined: Aug 2008

Sunday September 21, 2008 10:33

<< Hi DBR,
Here's another trick that will give you about 40 horses... Unplug the fuel temp sensor on the main fuel filter on the engine and put a 15k resistor across the plug. Put a piece of electrical tape over the end of the plug to cover the resistor and gently push back into the socket so it looks ok. This tells the ECM that the fuel is hotter than it is resulting in a much denser charge. Beware that a heavy right foot may cause some engine damage over time but if driven properly these tricks will not be detrimental to the engine in any way. If driven properly you will also see a notable decrease in fuel consumption. Hope this helps. >>

Greetings, Roadking
(1) Are you possibly referring to the two wire fuel temp sensor? If so, will this work on an MBN single turbo C15?
(2) The "engine damage over time" thing has me a little nervous could you please elaborate a little more. Also is there another resistor that could possibly be used that would insure no chance of damage, (understandably the cost probably would be less gain, but I'd rather be on the safe side)

Concerning the "boost pressure sensor mod" I read in another forum that you could mount a small air compressor regulator on the manifold, where the sensor normally is, screw the sensor into the regulated side, which should be set at 28, or 29 psi.
The gain would be more boost, without the ecm derating.

Just repeating what I have read, I have not tried this, but it sounds like it should work. I did purchase a regulator, but have been experiencing the yellow "check engine" light that flashes momentarily in my overhead panel whenever I'm "standing on it" hills, overpasses, tall bridges, etc. As soon as this is corrected, I plan to proceed with the mods.

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Roadking

Posts: 6
Joined: Sep 2008

Monday September 22, 2008 05:59

Hi Droy,

1. I dont know about MBN as we dont have this in australia, but I am referring to a 2 wire FTS. Here is a paste from Catfreak which may help for a 3 wire although I havnt tested this as all ours are 2 wire.

"There is also a trick for fuel temp sensor havent messed with 2 wire like on C15 but if you have 3 wire cut orange wire leave it like that. Strip bare spot on black wire cut white wire solder end of white wire toward sensor to black wire then solder 150ohm resistor to other white wire and solder other end of resistor to the black and white you solderd first. This is good for about 40 horse and about .5 mpg on mine anyway. I hope instructions were clear enough if not post and we'll do something else you can call me and i'll talk you through it or something. Good luck "

Adding a physical regulator will do the same as a resistor- that is trick the sensor into thinking the boost is lower than it actually is. The check engine light can be avoided by letting more pressure thru the regulator.

2. The engine damage issue comes from commonsense. Extra fuel=more heat. Some say piston damage can occur. While I would be concerned about this on a Detroit, Cats arent known for weak pistons. Some say the extra dense charge can pit the liners, although I expect this will be a temperature issue. These are issues that can be avoided by remembering that you are driving a modified engine. Watch the pyrometer, if your exhaust temp rises so will your intake then engine temps. Engine oil temp should also be monitored. If it is getting hotter than usual back it off. You are taking some control back from the ECM so remember to control the throttle rather than just 'hold it flat and let the ECM control it'. The thing I have noticed most with these mods is that the engine feels much more "mechanical" say like an old 3406b. So drive it that way. Press the pedal as far it will give you power and no more. Dont burn it up! I have never had an issue with cats and these mods. Happy trucking.

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pipeline

Posts: 4
Joined: Dec 2009

Monday December 21, 2009 15:34
Hey roadking i was wondering how many watts the 5k resistor would be thanks.

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pipeline

Posts: 4
Joined: Dec 2009

Thursday December 31, 2009 11:32
Hey gang Happy New year,i'm still looking for the wattage on this 5k resistor if anyone could help that would be great.

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