Resistor Mod in IAT Sensor?

[KenCary]

Has anyone tried adding a resitor in line with the IAT sensor?

If you do this you can fool the PCM into give more igntition advance.

I am about to try this and I am not sure of what resitance range to start with.

Suggestions?

Ken

[WingsOfSaturn]

Originally Posted by KenCary

Suggestions?

DON'T! You asked and you received.

[KenCary]

Originally Posted by romzek

DON'T! You asked and you received.

OK I appeciate your strong feelings about this, but this post does not tell me why you feel so strongly about this.

I have done this with other cars and it works, not as good as a PCM program or piggyback chip, but it works and it is free. What's the worst that could happen--- check engine light? A little spark knock? I can undo this mod in 1 minute if I don't like it.

On the other hand, maybe I am missing something. I don't claim to know everything, that is why I am posting this question.

Fair enough?

Ken

[Asterixx]

These cars run plenty rich as it is. I can't see richening them up even more helping matters, and will probably only serve to carbon up your rings even faster than stock...

[Low Saturn]

Originally Posted by KenCary

What's the worst that could happen?

These cars run way rich as it is. Fooling the PCM into thinking its colder than it really is would cause fouling of the spark plugs, the O2 sensor(s), clogg the catalytic converter, poor performance and poor fuel economy.

In the short term, you would waste money on gas the goes unburnt out the tailpipe. In the long term, you'd ruin hundereds of dollars in parts. All for a $0.25 part that really does nothing beneficial.

[KenCary]

Originally Posted by Low Saturn

These cars run way rich as it is. Fooling the PCM into thinking its colder than it really is would cause fouling of the spark plugs, the O2 sensor(s), clogg the catalytic converter, poor performance and poor fuel economy.

In the short term, you would waste money on gas the goes unburnt out the tailpipe. In the long term, you'd ruin hundereds of dollars in parts. All for a $0.25 part that really does nothing beneficial.

OK now this is some useful information. I did not realize that the Saturn ran so rich. I don't think a few degrees shift would cause as much disaster as you mention, but you point is well taken.

Thanks for the good info.

Ken

[fdryer]

BTW, the iat resistor mod is not an ignition advance trick as it has absolutely nothing to do with the ignition system's electronically controlled timing. There are numerous threads, if you take the time to research it, in these forums using the search function, reading the suggested threads initially posted at the bottom of these posts, or simply wading through the posts. The members here are not impressed when someone comes here presuming to know a few facts without some research behind this and will let you know very quickly, if not abruptly, to cease any lengthy postings since it been covered so many times in the past.

[asdf]

You have to realize though that it will only have an affect on the fuel control until the O2 sensor warms up. Once the O2 sensor is online, it makes all the corrections to maintain the 14.7:1.

If you disconnect the O2 sensor, it will always run off those sensors however.

If you really wanted to get serious, you'd want to use a scan tool to observe the effects to be able to tune it. The MAP and ECTS also play a part with those operations.

But, with a knock sensor integrated into the system, the car is suppose to utilize maximum spark advance without spark knocking anyways...

[Gerry Proctor]

Originally Posted by bmxgoof

...
But, with a knock sensor integrated into the system, the car is suppose to utilize maximum spark advance without spark knocking anyways...

Though it doesn't change anything in the original topic of the replies to this post, this statement isn't entirely true. Spark tables are tied to fuel tables. There are many fuel tables that have associated spark tables with very conservative spark profiles. In these tables, the engine would acheive nothing near full or optimum spark advance. Though, in general, what you write is true, just not in an absolute sense.

[sc2dave]

I did the opposite.I put a 110ohm resistor to fool the engine into thinking the intake air is 224*.according to my scanguage, it's netting me around 2-4 more m.p.g.

[deadmeat3344]

Originally Posted by bmxgoof

You have to realize though that it will only have an affect on the fuel control until the O2 sensor warms up. Once the O2 sensor is online, it makes all the corrections to maintain the 14.7:1.

At WOT is around 12 (from my readings)

[plastic torpedo]

My saturn ran 9.8:1 at WOT before I put the SAFC in. Adding more fuel would definitely NOT help you in this situation.

[asdf]

It does not run off the O2 sensor at WOT. WOT is not normal operation.

[asdf]

Originally Posted by Gerry Proctor

Though it doesn't change anything in the original topic of the replies to this post, this statement isn't entirely true. Spark tables are tied to fuel tables. There are many fuel tables that have associated spark tables with very conservative spark profiles. In these tables, the engine would acheive nothing near full or optimum spark advance. Though, in general, what you write is true, just not in an absolute sense.

I was pretty sure that, while yes it does use a table as a baseline, it was still constantly pushing the ignition timing to its max (for fuel economy).

[Gerry Proctor]

Under most of the maps, that's true. But under some, it provides a very slow and limited advance rate. That is why goofing around with the sensors anticipating some improvement somewhere can put you in a place you didn't intend. Doing these things without the benefit of at least reviewing sensor data for a baseline is not good tuning discipline.

And anyone running A/F ratios below 12:1 on a stock engine has some serious tuning issues going on. 9.6:1 would be pouring black smoke out the back. Must be something wrong with the wideband to see that kind of ratio.

[virnin]

Originally Posted by plastic torpedo

My saturn ran 9.8:1 at WOT before I put the SAFC in. Adding more fuel would definitely NOT help you in this situation.

WOT is not closed-loop operation but that sounds a little on the rich side, even for a Saturn. Stock injectors and fuel pressure regulator?