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MAP and Knocking
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ski21 Offline
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Post: #1
MAP and Knocking
I made a MAP sensor to the specs of the water4gas books. It works great, I can tune the car to where it starts to spit and sputter, then tune it up a little more until it runs. The only problem I'm have is knocking when I accelerate. I know you need to tune it to be lean, but how do u take care of the knocking. This can't be good. I'm using 87 octane from exxon, should I go up to 89 or 91 octane to prevent this knocking. Can I add xylene or acetone to help. Any suggestions would be greatly appreciated. Thanks.
07-31-2008 03:12 AM
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PanamaRik Offline
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Post: #2
RE: MAP and Knocking
Add a resistor in Parallel to the Intake air temp sensor. With a normal 2 wire sensor that means put the resistor between the 2 wires. This will raise the temperature that the computer 'sees' and retard the ignition slightly as well as leaning out a bit more. Then ease back on the MAP a bit. I use a 2.2kohm on my IAT, or a 5k pot can also be used. Don't cut the wires to the sensor, just bare the insulation a bit and add in the resistance either with soldering or self cutting snaplocks.

PanamaRik

ski21 Wrote:I made a MAP sensor to the specs of the water4gas books. It works great, I can tune the car to where it starts to spit and sputter, then tune it up a little more until it runs. The only problem I'm have is knocking when I accelerate. I know you need to tune it to be lean, but how do u take care of the knocking. This can't be good. I'm using 87 octane from exxon, should I go up to 89 or 91 octane to prevent this knocking. Can I add xylene or acetone to help. Any suggestions would be greatly appreciated. Thanks.

Drop by my site at http://gassaver.panamacentric.com and say 'Hi' Rik
07-31-2008 03:30 AM
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ski21 Offline
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Post: #3
RE: MAP and Knocking
PanamaRik Wrote:Add a resistor in Parallel to the Intake air temp sensor. With a normal 2 wire sensor that means put the resistor between the 2 wires. This will raise the temperature that the computer 'sees' and retard the ignition slightly as well as leaning out a bit more. Then ease back on the MAP a bit. I use a 2.2kohm on my IAT, or a 5k pot can also be used. Don't cut the wires to the sensor, just bare the insulation a bit and add in the resistance either with soldering or self cutting snaplocks.

PanamaRik

ski21 Wrote:I made a MAP sensor to the specs of the water4gas books. It works great, I can tune the car to where it starts to spit and sputter, then tune it up a little more until it runs. The only problem I'm have is knocking when I accelerate. I know you need to tune it to be lean, but how do u take care of the knocking. This can't be good. I'm using 87 octane from exxon, should I go up to 89 or 91 octane to prevent this knocking. Can I add xylene or acetone to help. Any suggestions would be greatly appreciated. Thanks.

So what wire do I need to put the resistor on. My IAT is grouped with my MAP sensor wires. For example I got 4 wires.
Ground
IAT to ECU
5 volt supply
MAP to ECU
Where would I want to put the 2.2k resistor?

thanks again.
07-31-2008 03:51 AM
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PanamaRik Offline
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Post: #4
RE: MAP and Knocking
You need to connect the resistor between the 2 wires going into and out from the IAT. Here's a link to Mike's tuning for mileage document which explains the different sensors in far more detail.

http://www.fuelsaver-mpg.com/doc/TuningForMileage.html

PanamaRik

ski21 Wrote:
PanamaRik Wrote:Add a resistor in Parallel to the Intake air temp sensor. With a normal 2 wire sensor that means put the resistor between the 2 wires. This will raise the temperature that the computer 'sees' and retard the ignition slightly as well as leaning out a bit more. Then ease back on the MAP a bit. I use a 2.2kohm on my IAT, or a 5k pot can also be used. Don't cut the wires to the sensor, just bare the insulation a bit and add in the resistance either with soldering or self cutting snaplocks.

PanamaRik

ski21 Wrote:I made a MAP sensor to the specs of the water4gas books. It works great, I can tune the car to where it starts to spit and sputter, then tune it up a little more until it runs. The only problem I'm have is knocking when I accelerate. I know you need to tune it to be lean, but how do u take care of the knocking. This can't be good. I'm using 87 octane from exxon, should I go up to 89 or 91 octane to prevent this knocking. Can I add xylene or acetone to help. Any suggestions would be greatly appreciated. Thanks.

So what wire do I need to put the resistor on. My IAT is grouped with my MAP sensor wires. For example I got 4 wires.
Ground
IAT to ECU
5 volt supply
MAP to ECU
Where would I want to put the 2.2k resistor?

thanks again.

Drop by my site at http://gassaver.panamacentric.com and say 'Hi' Rik
07-31-2008 04:09 AM
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ski21 Offline
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Post: #5
RE: MAP and Knocking
Thanks for all the info, but Im still confused. Here is a wiring diagram for my car. Does the resistor go in between the IAT wire and the ECU?


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(This post was last modified: 07-31-2008 04:50 AM by ski21.)
07-31-2008 04:39 AM
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PanamaRik Offline
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Post: #6
RE: MAP and Knocking
IAT normally uses a 5v ref voltage and a signal line back to the computer. Looking at that wiring diagram it appears that the 5v ref is shared with the MAP. I would try the resistor between the 5v © and the IAT signal (B). As the resistor is in parallel with the IAT sensor it will lower the resistance in the IAT sensor and increase the voltage going back to the computer, without affecting the 5v supply to the MAP sensor. Probably easiest to do at the sensor end, rather than at the computer.

PanamaRik

ski21 Wrote:Thanks for all the info, but Im still confused. Here is a wiring diagram for my car. Does the resistor go in between the IAT wire and the ECU?

Drop by my site at http://gassaver.panamacentric.com and say 'Hi' Rik
07-31-2008 06:18 AM
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ski21 Offline
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Post: #7
RE: MAP and Knocking
That would be nice to do at the sensor, but the sensor is in a place I can't really get too. Could I run a 14 or 16 guage wire with one end connected to the resistor to the 5v and the other end of the resistor connected to the IAT wire near the ECU. Of course I would solder and liquid tape.
07-31-2008 06:52 AM
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ski21 Offline
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Post: #8
RE: MAP and Knocking
So does anyone know if that set up would work. Or if I run 14 or 16 gauge wire from both ends of the resistor one going to the IAT and the other to the 5V. I can use a quick splice connector that way.
07-31-2008 12:26 PM
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hogie Offline
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Post: #9
RE: MAP and Knocking
ski21 Wrote:So does anyone know if that set up would work. Or if I run 14 or 16 gauge wire from both ends of the resistor one going to the IAT and the other to the 5V. I can use a quick splice connector that way.

Yes you can use a quick splice connector,but I would put it between A and B,IAT and sensor ground.
07-31-2008 06:36 PM
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ski21 Offline
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Post: #10
RE: MAP and Knocking
Hmm, now i'm really confused, Pan says the 5v and IAT, and Hogie says Grnd and IAT. Which one is it. This will stop the knocking right,
07-31-2008 06:49 PM
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