The original daewootech forum

Daewootech.net is selling an intake chip which is named Choco chip...

As I had problems in ordering it from daewootech.net I want to (if it is possible) make one myself. My questions are:
- how much petrol will my engine take
- is it absolutely safe for the engine ?
- how can I make one ?

The Chocolate Chip thing is just a resistor to fool your intake air sensor so that it thinks that it's very cold out.

As a result it enriches the air/fuel ratio which gives you a little extra horsepower if you have added some aftermarket parts such as a high flow air filter and intake.

This resistor costs about half a cent (when purchased in bulk like I do)

1) As with any enrichment of fuel, your car will use more gas.
2) is it absolutely safe for your engine....that's hard to say.... it depends upon how the chip was designed. (for more info see at the bottom of the post about insurance and liability)
3) How can you make one.... it's cheap and easy but not necissarily wise.

--> first you have to measure the impedance of the sensor to find out what value of resistor needs to be used.

--> I guess the best way would be to take the absolute coldest day your car will ever see and measure the intake air sensor output.

--> if you take this number and add a little extra for safety it should work fine.

Personally I could easily make this little device about a million times better (and safer) by not replacing the actual sensor but by simply modifying the existing IAT sensor.

Basicly it's just a "thermistor" which is a resistor that changes resistance based upon temperature.

I can't remember if the resistance goes up with temp or down ( it's been a few year since I played with one...I think the resistance goes up with temperature )

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This is just an example...don't use these numbers
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Let's say that the resistance at 20 degrees C = 5000 ohms and it's temp vs resistance constant is say 50 ohms per degree C

Then at -30 degrees C it would have dropped from 5000 ohms to 2500ohms

And conversly if it was +30 degrees C the resistance would have moved up to 7500 ohms.

If one were to put a potentiometer (variable resistor) in parallel with the IAT sensor you could "dial in" your mixture from "stock" to "extra rich" by simply turning the potentiometer knob.

I personally would pick say -40 deg C as my maximum rich level = ( 60 degrees difference X 50 ohms / degree) = 3000 ohms less than it was at 20 degrees C= 5000 - 3000 = 2000ohms

So my "maximum rich" level would require that I make the sensor read 2000ohms when it should normally read 5000ohms.

This is very easy and would cost only a few dollars to make.

Unfortunatly this is just an example as I have never measured the resistance of the IAT sensor and I have no idea what the ohms/deg constant would be.

In the future sometime when things slow down at work I will take measurements on various days to see what the actual value is.

I personally will never sell this type of device until insured to do so as there is a great deal of liability to whom ever sells this product (such as Daewootech.net)

For example.... say something happens and they blame it on the "chocolate chip".... if your not insured against liability you could be sued for whatever costs were incured by the damage.

Lets for example say that the "chocolate chip" was designed to simulate a 0 deg C day.... then on a -20 deg C day your car would run lean because it thinks the air temperature is 0 degrees.... which could lead to detonation...and damage to the engine.

Now lets say that the engine siezes while your on the highway and you cause a major 25 car accident which includes injury to several people.

The insurance company of the Daewoo owner is going to investigate why the engine siezed up....they will do whatever they can to get out of paying a multimillion dollar claim. (trust me on this one....my brother in law used to be an insurance man)

If they found this "chip" attached to where the intake sensor should be and found out what purpose it held they would most likely leave the owner of the vehicle and the person who sold/made the chip responsible for possibly several million dollars in damage and accident claims.

If you guys continue to remind me about this I will try to get all the reading I need to post a "how to" on making a "safe" IAT sensor hack.

PS ..... sorry for the long post.... and I will throw up a diagram a little later which shows what I'm talking about.

Erfinder, you are our Daewoo guru, and I'm serious

So if you want to, and have some time I would love to read you "how to make a safe IAT"

Well folks I have some progress to report on checking the intake air sensor.

It is so cold my car's intake throttle body froze and wouldn't allow me to rev the engine (pedal was actually stuck solid)

Presently it is -34 degrees Celcius which is -30 degrees F

So I braved the cold for a minute or two to check the resistance of the IAT sensor.

My reading was 17.8 K ohms accross the sensor.

It's supposed to warm up by the end of the week so I will take some more readings (if I don't freeze to death )

It's so cold that the water from the exhaust is actually forming ice on the tail pipe! To think it was about 40 deg Celcius warmer last week.

Oh well I guess that's Canada for you.

Ok as promised........ here is the best (and safest) way to fool your car's computer into thinking the air is much colder than it really is...

Here are the links

IATCCT.jpg is the original Lanos sensor circuit....
http://ca.f1.pg.photos.yahoo.com/ph/erf ... m=adb3.jpg

IATCCT2.jpg is the modified Lanos sensor circuit with manual enrichment control......
http://ca.f1.pg.photos.yahoo.com/ph/erf ... m=a60b.jpg

and last but not least is the sensor data the IAT should be putting out.....
http://ca.f1.pg.photos.yahoo.com/ph/erf ... m=1b4a.jpg

So basicly the way I've set this up is that with the potetiometer dial turned all the way to zero ohms the PCM sees exactly what the IAT sensor is putting out (correct temperature)

When you turn the potentiometer dial all the way up the resistance is then 50,000 ohms + IAT sensor resistance

For example.....lets say the temperature is 25 deg C (77 deg F)

According to the chart the IAT should measure about 2,055 ohms of resistance which is then fed back to the computer.

With the Potetiometer all the way up the computer would then see 50,000 ohms + 2,055 ohms = 52,055 ohms

This would result in the car thinking that the temperature is about -45 degrees out so it would dump in way more fuel to compensate ( air to fuel ratio becomes very "rich" )

Then if you turned the Potentiometer dial all the way down the computer would then go back to seeing a correct temperature.

If you turned the dial say 1/4 of the way up ( 12,500 ohms) and the temp was still 77 deg F your total resistance would be.........

12,500 + 2,055 = 14,055 Ohms

From the chart this makes the car think its about zero degrees F.

because of the very large swing in resistance it would be very important to find a high precision dial potentiometer that has 10 to 20 turns from one end to the other.

This way you could dial in the exact amount of "richness" you wanted.

Here is a great example of a potentiometer I use on a regular basis....

http://dkc3.digikey.com/PDF/T041/0919.pdf

The wirewound precision ten turn pot in the top right is exactly what I'd use.

To tell you the truth I think 50Kohms is too high..... the 25Kohm pot is probably better..... this would give you a resistance indicating around a -30 degree Celcius temperature.

The higher the resistance the less accurate it will be for doing small movements.

For example a 50K it's going to read 5K per turn where as the 25K will be only 2.5K per turn

So if your trying to make the PCM think it's 60 deg F instead of 80 deg F it would be harder to get that exact value with the 50K than with the 25K

The difference between 80 deg F and 60 deg F is only about 1000 ohms

On the 50K this represents 1/5 of a turn where as with the 25K it represents just under a full 1/2 turn.

So the 25K potentiometer with part number GU2531S26-ND would work the best.

As well the Concentric pot knobs on the next page on the bottom left make for real easy setting of the potentiometer..... http://dkc3.digikey.com/PDF/T041/0920.pdf

These dials will show you exactly how many turns you have moved and they have a "lock" to keep the dial in the exact position you want.

Plus these dials really look cool.... I have a couple for projects I use these things on.

I'm running a total of 25k ohms on mine and man what a diff. How much higher can I go with out screwing things up? I can tell a big difference between 4500 and 6000 rpm's and on the highway I'm up to 95 like nothing

whats your MPG like?

not sure what the exact mpg is but seems I'm not using to much more