word of caution: dont run it too lean, it could burn a hole in a piston head. way to check and see if your running into way to lean burn is pull the plugs and if thier all white thats not a good sign...

VetteOwner -

100% agreement. That is why I started the "infer engine temperature" thread at saturnfans.

Thanks for the tip on the plugs. I didn't know that. I will do that.

Also, with lean-burn, there is the emissions issue. My goal would be the maximum lean that is engine-safe and still California emissions compliant. The good(?) news is that I am due for an emissions test, so this all goes together quite nicely.

Maybe my saturnfans question should be, how can I infer the temperature of the piston head? Would it still be an oil coolant temperature switch or a high-temperature probe in the exhaust manifold or ??????

CarloSW2

I bought some resistors so I could try it on my van. What's the ideal inlet air temp? Outside is 90F while driving I was getting about 110F-115F IAT. The resistors I got were 100, 150, 220, and 330 ohms. Any thoughts on a Dodge Van using this?

Some cars get to a point where they start to richen the mixture if you get the IAT too high, don't they?

popimp -

I did a quick google and found this :

IAT sensor hack
https://www.dodgeforum.com/m_152375/tm.htm

The above thread is not talking about a Caravan, but I would think that Dodge's share the same sensors. That thread led me to this :

https://www.hurricane-horsepower.com/

Which has this cool picture (for Toyotas! :confused: ) :

https://www.hurricane-horsepower.com/...-emissions.gif
https://www.hurricane-horsepower.com/...-emissions.gif

But, it looks like the gizmo is designed for HP, not MPG, :( . It would be worth asking them if the dial "goes the other way".

....

Anyway, if I were you I would :

1 - idle the car in the driveway with each resistor attached and observe the IAT temperature using the scangauge. Then you will have a "map" of resistor to temps for your IAT sensor. Since you would only be idling, aka 0 load, you would be able to "map" the resistors.

2 - Since you already know the "normal" IAT temps, add a resistor that adds maybe +30 degrees to the 110-115 degrees you are seeing and see what happens. If you do a test similar to mine, you should be able to make some kind of conclusion as to whether the scangauge is reporting the same response.

When Cheapybob did his tests with real HAI temps, everything seemed to work until around 180 degrees F. The question is, what are the little black boxes (ECU/PCMs) doing similar or differently?

What do other people think?

CarloSW2

Bill -

I think that's the rub, each car has it's own response. Each ECU/PCM is different.

Guess this commercial :
What's in your ECU/PCM?

CarloSW2

The answer to your question: Capital One?:)

I think that Saturn's start getting pretty fussy when actual IAT and coolant temps get up around 200F. They start backing of/retarding the timing so, if I remember right, you want to shoot for somewhere around 180F max.

OK guys I went outside and put in each resistor. I only turned the key forward (didn't turn on van to get the temp reading of the resistors). The temp should be the same regardless because the resistance value is fixed (could change while driving due to heat).

My results

100 ohm - 335F
150 ohm - 315F
220 ohm - 290F
330 ohm - 260F

I did idle the van with the 330 ohm resistor in, I guess I should have done it with the others also (going outside soon). While idiling the 330 ohm resistor installed I got .3gph, with the stock sensor in I got .4gph, and with no sensor or resistor installed (open ciruit), I got .5gph. It usually idles at .5gph in N or .6gph in P. During this test the van was in closed loop for all 3 settings, according to SG2. Feedback please.

I wanted to consult the gurus before I took it on a test drive.

I would say to go on a short test drive to see how the engine responds. That way, if the results are less than favorable you can come back home and make changes.