Intake Air Temp resistor experiment.
 

My Intake Air Temperature resistor EXP

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Intake Air Temp resistor experiments
Copied from general discussion.

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I saw some postings and some mentions but not too much on IAT resistors. Almost everytthing on the net is about more power not fuel economy. I apologize if this has been beat to death years ago.

I just went for the gold. I put in the lowest resistance that the computer would accept without setting a code for Intake Air Temp out of range and compared that with a 10k resister. Here is a little range of experiments and the intake temp I see on the Scangauge. I just used the nominal values of the resistors rather than measuring them. A co-worker tried to tell me about these "chips" a year ago or so and I just totally discounted it. This is darn near the stuff of urban legends. These resistors are 99 cents for a pack of five at Radio Shack. I have never done so much so cheaply before in my life. This is on my 2001 Saturn SL.

10k ohm IAT 28 F
940 ohm IAT 198F
136 ohm IAT 233 F this is two 68 resistors in series.
068 ohm IAT 279 F set an out of range code.

I did an ABAB experiment on the same 8.5 mile loop trying to drive identically. The lights did not cooperate 100% but I judge the experiment valid. The two runs with the 10k ohms were 43.3 and 44.1 mpg. The two runs with the 136 ohms were 61.0 and 63.9 mpg. The average speeds ranged from 29-31 mph. The difference between the average mpg's is 18.75 mpg giving an increase of 43%. The 10k ohm resistor was a slight handicap as the actual temp was 40 F. It was not far off since when I filled up yesterday my tank average was 46.2 mpg and this is just a little better than the 43.7 average of the two 10k runs.

Summary
136 ohm 61.0 mpg
10k ohm 43.3 mpg
136 ohm 63.9 mpg
10k ohm 44.1 mpg

Average difference 18.75 mpg or 43% using the 10k ohm mileage as the base.

I then went out on the freeway and made a 16 mile total loop at 60 mph and got over 60 mpg without any engine off coasting. I just drove easy. I did a bit of idle coasting on the last bit coming home as I could see the average was at 59 and wanted to break 60 mpg.

This morning I did the trip to work starting with a cold engine, I did not need to go to work it is just a familiar route. Against the slight grade and more than slight wind I made 53.8 mpg to work on the freeway at 61 mph. There was no drafting. The instantaneous mileage was between 55 and 60 mpg. I never shut off the engine but reset the current trip at work and started home. I came home on secondary roads so I could drive slower and pulse and glide with the wind to my back. By the time I got to near 1/2 way home my average was 112 mpg. I then lost a bit on as the lights would not turn green until I triggered them myself in the light Sunday morning traffic. I had to get into 2nd gear at several lights. At the stop sign at one road I botched the takeoff and lost about a mile per gallon. I only mention this because the trip home averaged 99.6 mpg. Darn it all anyway. The round trip averaged 70 mpg at an average speed of 40 mph. Here is the "today" summary:
70 mpg
40 mph ave
63 max
28.7 miles

My car obviously has a sensor that tells it when I am in fifth gear. The instantaneous mileage makes a distinct jump now when I hit fifth gear. Something beyond the usual expected with a shift. I can accelerate decently on a slight upgrade at 40 mph in 5th gear and get 50-60 mpg during the acceleration. This does more than just adjust the timing. I can watch the timing and while it changes some with the resistor the change is not that great and something else is going on. Some think it leans the engine out but it is running closed loop. My current theory suggests EGR. I have run engines lean and ruined one turbo 2.3 Ford engine running it lean. This does not feel lean. Drivability is not suffering in the least. I am excessively short shifting to get into fifth gear as soon as I can because I see the immediate benefit.

The only aero mods to my car are blocking the grill and removing the spoiler. I have not even proven that removing the spoiler is a good thing.

This is pretty unbelievable. Nothing will be really confirmed until more distance passes and I have to fill up and check the calibration again on the Scangauge. Last check was within 0.5% yesterday. I hope this is for real. It sure looks that way. I suspect that the exhaust temp is probably not warm enough to keep the catalytic converters on line. Just speculation at this point.

If someone else was writing this I would not believe it either.

Ernie

Nice report :)

So what do you think EGR is doing? It was my understanding that by making the ECU think its inhaling an inferno it will use less fuel at the cost of power. But you are saying that its not driving noticeably different?

I would not say I that I am not losing power. I really haven't used hard acceleration lately. I meant to say that it is running very smoothly with no bucking or hint of a lean condition. This was just beyond my wildest expectations.

With respect to the EGR it is partly used to limit detonation and control peak combustion temperature. When the engine is fed very hot air both of these will increase. I think the EGR ratio is increasing and this is lowering the throttle loss. The only instruments I have that could give a verdict on this are the TPS and MAP sensors. It was just too much to watch in my excitement.

Ernie

I've been meaning to do this, but I'm not sure of exactly how to perform this modification. I'm pretty useless under the hood. I couldn't even find the IAT sensor under the hood. What exactly should I be looking for?

You would be looking for a connector on the tube that let's air into the air cleaner box. I suppose that some manufacturers may put an IAT after the aircleaner but, on my Saturn, it's near the end of the tube that extends outside of the engine compartment.

IAT sensor
 

[QUOTE=What exactly should I be looking for?[/QUOTE]
It is a small connector on the other side of the aircleaner from the pipe to the manifold. It is down about 3 inches below the cross stucture just to the front of the air cleaner. You can just reach it. I chose to pull the aircleaner assemble to get my hands on the wires. There were three 10mm headed bolts holding the air cleaner in on my car. Here are some excellent instructions. These are just for a different purpose and a different car but the principle is the same.

https://kingenterprises.net/IAT-Timing-Tricker.htm


Ernie

Thanks alot!

I gotta believe that you are forcing an extra lean condition that the O2 sensor feelback can not compensate for and are producing a lot more NO2 emissions as a result. Pretty impressive results however.

That's interesting. That's been discussed here before and it seems to work with the Saturns but not with those kinds of results. I wonder if you have something else going on with the engine. Maybe pull the plugs after a few more trips to see what they look like. You have hit the mother load :). Keep us posted.

Too bad the SG doesn't show short/long term fuel trim - that would answer some questions.

JanGeo: if the O2 sensor wasn't able to correct for a lean condition, I'm pretty sure it would throw a code, wouldn't it?

I have no data based reason to disagree with you. Another known phenomena is HCCI Homogenous Charge Compression Ignition. It is very difficult to control but Honda has managed to do so for some years now on 2-stroke scooters sold external to the US. They call it Active Radical Combustion. It is associated with high EGR rates, but that is a real stretch in this case. That is very unlikely. Major corporations such as Catepillar are spending large sums trying to control HCCI but the efficiency gains are in line with what I am experiencing. Here is a definition. This actually is associated with low levels of NO.

https://en.wikipedia.org/wiki/HCCI

Ernie

usedgeo -

(copied from https://www.gassavers.org/showpost.ph...18&postcount=2)

Thanks for making a new thread on this. I keep imagining a "clicking dial" on my dashboard that goes from "off" to different resistor settings that mess with the IAT input. Different cars can have different resistors. I don't think a potentiometer would work because the resistance range is too great (right?).

1 - For car ECU/PCMs that like this mod, I think it makes a big difference. I also think that, if possible, it would be nice to know what the emissions are. For the purpose of an experiment, anything goes, but I also want to know the long term effects are on the emissions.

2 - You'll burn your valves out! Ha ha ! This is the "A Christmas Story" argument, aka "you'll shoot your eyes out!". How is you engine doing? Can you gauge the engine temperature with and without the mod? Since we are "driving gentle" I don't think the engine is at risk, but I would like to know that the long term effects are on the car and what the "danger zone" is.

CarloSW2

MetroMPG -

If you know the code, you can get a solicited response from the ECU/PCM (in hex :thumbdown: ), but that won't help you with continuous monitoring.

This will become available on the next generation of SG software, where you have programmable gauges.

CarloSW2

usedgeo-

Here is what I read. I apologize for not having the URL :( . In lean burn conditions that go to far, you can burn out your catalytic converter. Here is an ideal world test that you could do if you have the $$ to burn :

1 - Get a high temperature thermometer that is rated to about 1000 degrees.

2 - Install it post catalytic converter. EDIT : INSTALL IN EXHAUST HEADER, NOT POST CAT

3 - Run the car as normal without the IAT mod.

4 - Run the car with the mod.

In step 4 you *should* see the temperature increase as compared to step 3. If the temperature increases 180 degrees F over the temperatures in step 3, then you are in danger of damaging your catalytic converter (EDIT : DAMAGE WILL RESULT TO VALVES, NOT CAT). For me, that would mean shooting for a "safe" maximum of 100 degrees F over step 3.

EDIT : SEE (https://www.gassavers.org/showpost.ph...19&postcount=8) FOR SOURCE OF INFO.

CarloSW2

What may happen is the table for the fuel injection has entries for that false air temperature but the O2 sensor can only correct for slight deviations from the table entries. If you have a lot of EGR gasses coming back in then that would reduce the NO2 levels. Isn't NO2 Nitrious Oxide and a combustion enhanser?? Humm that would explain the dizzyness I felt one time when I got a big whiff of a car's exhost.

If that's the case, will an altered O2 sensor correct the emissions increase? EFIE makes a voltage alteration chip for the O2 sensor that exists so that you can make the O2 sensor give off a false reading.

yes but again it can only correct so far - within the expected variations that is programmed into the ECU injection tables. This is why when a Turbo is added the tables have to be reprogrammed to allow for more than usual fuel when more than expected air is forced into the engine and to run a little richer to prevent detonation. Changing the readings from the O2 sensor will operate the CAT at the wrong temp fuel gasses mixtures and could result in costly damage but it sure does increase the MPG!

repete86 -

I just ordered one for my hydrogen gizmo thingy. Of multiple exhaust mod choices to go with the gizmo, this is the easiest mod because it is "automatic" (you dial-in the air/fuel ratio bias). This will give me a guaranteed lean-burn condition. I also have access to a dyno through my mechanic, so I will be in a position to quantify my emissions. The goal is lean-burn and NOx compliance.

CarloSW2

I would have been doing this with the intention of reducing emissions. I'm going to have to do more research to find a way to fix this problem. My mileage improvements have been done for environmental, not economic reasons.

repete86 -

My goal is to comply with clean emissions also. The law, in the case of California, is pretty strict. If I can comply with California emissions, then I am good to go.

Lean-burn, from what I understand, reduces HC and CO emissions. It's the NOx emissions that go up. NOx emissions is the bain of diesels. I think that the key to Honda's new clean diesel is the emissions scrubber :

Honda Previews Next-Generation Engine and Power Technologies
https://www.greencarcongress.com/2006...previews_.html
However, please don't hesitate to *test* the mod :) .

CarloSW2

The problem is that I live in Florida. The state of Florida doesn't believe in things such as emissions, so I have to do what I do based on what will most likely lower my emissions since I have no way of testing affordably. I would really ideally like to even outdo Japan's emission requirements.

repete86 -

.... Wait, now I understand. You have no rules ....

Florida Smog & Emission Checks
https://www.dmv.org/fl-florida/smog-check.php
If I were in your situation, I would take advantage of Florida and just get it to work first. I checked and Georgia has emissions requirements. Eventually you can put the car on a dyno over there.

From my POV, the idea is to in increase MPG "within the rules" of emissions that everyone else has to comply with. You've been given a no-rules barred experimental lab. Go for it!!!!!

Here's Georgia emissions requirements :

Georgia Smog & Emission Checks
https://www.dmv.org/ga-georgia/smog-check.php

CarloSW2

I think I will. Any ideas for countering the NOx emissions being created by the resistor mod though? I'm thinking that if I add a second, or maybe even two more catalytic converters behind the first one that I might be able to counter them at least partially. Again, I know very little about the mechanics of a car. Does this make sense, or am I way off?

repete86 -

I don't know how to reduce NOx. If I were you and I had access to a dyno, I would keep putting in resistors until I found the one that would fail emissions. Then, I would use the previous resistor that still passed emissions. In this way you would be pushing the envelope but still "playing by the rules".

I'm also not a mechanic. Other people have asked about multiple catalytic converters, so maybe someone else will pipe up on this.

Question : Would a secondary catalytic converter designed for a diesel reduce lean-burn NOx?????

The following is NOT an advocacy for the gizmo I am evaluating, but I do like the analysis that is presented because it first talks about stock engine emissions behavior :

Emissions Analysis With Hydrogen Boost
https://www.hydrogen-boost.com/August%202006.html

In the above article, a "steady-throttle" is one key to low emissions in all cars. I think this would be true in the lean-burn case as well. As a gentle GasSaver driver, you may already be emphasizing behavior that reduces your emissions.

Here is something else on cat-cons. I think this is a good place to find "google phrases" to look elsewhere on the net :

How Catalytic Converters Work
https://auto.howstuffworks.com/catalytic-converter.htm

CarloSW2

For a Saturn, you can go as low as 110 ohms before the ECU freaks out and throws a code. I have tried 105 ohms and got a code. At 110 ohms, the IAT shows 247F. With the cold weather, I have went up to 220 ohms. This is ~200F.

You guys should be using a potentiometer instead of fixed resistors that way you can just dial in the value you want.

JanGeo-

Yes, that's a good idea too, but I don't think the IAT sensors work on a linear scale. Here is an example of the temperature graph for my Saturn (please ignore the red lines and circles) :

https://home.earthlink.net/~cfg83/gas...t_vs_ohms2.jpg

In the above example, in order to "dial in" IAT temperatures above 100 degrees, I would need a potentiometer that has a range of 63 (284 degrees F) to 1700 Ohms (100 degrees F). Do potentiometers come in this range? I would think that a 0-1500 ohm potentiometer would have "low granularity" at the bottom end of the dial.

CarloSW2

I tried a potentiometer when I first started messing with the IAT mod. It was difficult to control down near the bottom of the range; very jumpy.

diamondlarry -

That's why I was imagining a dial that "clicked" into each position. I am imagining in my head a dial on the cockpit that had an OFF position and then X number of R(esistor) positions. In the off position, the real IAT input would go to the ECU/PCM. In the other R positions, you could have a breadboard with different (and changeable!!!) resistors of your choice. That way, there would be no "jumpiness", but you would still have control over the range of IAT temperatures.

Hrmmmm, sounds like a kid's electronic project to me. Where's my crystal radio kit!?!?!?!?!?!?

CarloSW2

I think you may be on to something. A different value for different stages of engine warmness.

I applaude your decision. It's the same reason that I run a E15 blend.:thumbup:

Go for it buddy! you could market it as a mileage/performance chip for any vehicle and make millions selling on ebay!! :rolleyes: J/K!!!!!

I'm gonna see about doing this mod myself. maybe not with as low a resistance as usedgeo or diamondlarry. just to see if my car would respond to something like this.

Okay, I bought the resistors in order to start experimenting weith this project, but I'm having some problems under the hood. I can't seem to find anything that could be an IAT sensor. Is this an OBD2 thing? My car was built in '93.

Get an audio taper pot, which adjusts along on log scale rather than on a linear scale as do normal pots. In general, the more expensive the audio taper pot pot, the more log-like the output curve.

well shucks! the haynes manual for my car shows where the iat is but when i went to look there was nothing there. all i found was a lil flat area on the intake tubing where it should have been. now i'm gonna have to go searching for it on my day off when i have more time and light.

basjoos -

Thanks, I didn't even know they existed. Here's some URLs describing them :

All About Audio Amplifiers
https://www.angelfire.com/electronic/...mp-Volume.html

The Secret Life of Pots
https://www.geofex.com/Article_Folder...s/potscret.htm
https://www.geofex.com/Article_Folder...s/pottaper.gif

CarloSW2

repete86 -

Check this out :

Where is __________? (on 4th Gen Honda Accords)
https://www.mycb7.com/bb/viewtopic.php?t=53
This "mycb7" website is dedicated to your Honda Accord, so I think this will be a place that you troll for all the grimey details of your 4th gen Accord.

CarloSW2

LxMike -

There are already "dialing" performance mod chips on ebay. But maybe they only cover the "performance" end of the spectrum, or are (cheapy) audio pots.

Hrrrrmmmm, maybe I'll get one and perform an autopsy ;) .

EDIT : Here's one on ebay for $30 !!!:mad:!!!
88-95-96-97-98 99-04-05-06 Saturn SC/SL/SW Chip Module
https://cgi.ebay.com/ebaymotors/88-95...QQcmdZViewItem

EDIT : Oh, brain fart on my part. Nowwwww I see the J/K.

CarloSW2

If too good to be true, it probably is
 

This mileage is just too darn good. It cannot be true. Here is an unpleasant hypothesis.

What is the chance that the ScangaugeII incorporates the IAT temperature into its fuel use calculation?

Maybe I am fooling the scangauge not the car. I am doing well on this tank but the scangauge is showing 2.1 gallons used. This is about the 5th tank of gas I have used in this car and the gauge is quite accurate. I have driven 130 miles now and the fuel gauge looks like I have used 2.5-3.0 gallons. That would be right in line with my last fill up of 46 mpg.

I won't be fueling up for a couple weeks unless I take a trip. The suspense is killing me.

Yes, I will keep you posted.

Ernie

Asnwers to some questons.
 

I wrote to scangauge asking this question.

I called and a local dynamometer emission test would cost $100 minimum. I won't do that yet. I might pay for a 5 gas no load emission test, but I think I will wait a while first. 5 gas. CO, CO2, O2, HC, NOx.

There has been some discussion about Exhaust Gas Temperature comparisons. I have experience with airplanes and trucks that used such instrumentation. This is a good idea. I might by a cheap gauge for comparison purposes. I wonder if my infrared thermometer would be useful for this.

A standard catalytic converter is never going to clear up NOx. At least as far as I know.

I have come up with a really nice sounding theory for what is going on in the engine but I am going to wait until it is more clear that I really need such a theory.

If I missed a question hit me up again.

Ernie