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1990 DeVille
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181 Posts
Discussion Starter #1
A lot of heavily advertised products are just a resistor in series with the IAT sensor. This fools the car's computer into believing the ambient air is cooler (or warmer? I'm not sure) than reality, and the result is a different Fuel:Air mixture.

Claims include higher horsepower, better mileage, and improved hair growth.

What's going on?
 

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White Diamond '03 DHS (with DTS floor shift)
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It fools it into believing that it is cooler, thus a richer mixture, thus LOWER mileage. You can't have your cake and eat it too. Most of that stuff falls into the same category as the Tornado and the fuel line magnets. Remember what P.T. Barnum said.
 

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1990 DeVille
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181 Posts
Discussion Starter #3
Ranger, thanks.

Does it make sense to put a resistor in series with the IAT, and switch it in/out? That would permit the car to run normally unless the resistor were kicked in, which could be automated by activating the switch with the throttle linkage.

And what about my bald spot?
 

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70 Deville 77 Fleet 78 Seville 92 Deville 03 Deville
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I don't believe richer is faster. The law of the land is "let the buyer beware". There are no truth in advertising laws unless it is health related. Companies can claim anything in their advertising, it's called puffing, and it is up to the buyer to beware.
 

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1990 DeVille
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181 Posts
Discussion Starter #5
I may do an experiment.

I'll put 2-3 gallons of REGULAR fuel in the tank, and it should ping. After I add that series resistor, it'll run richer and should NOT ping. If that "works", perhaps I can begin using regular gas, activating the series resistor only when there's enough throttle to ordinarily cause ping.

Make sense?
 

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'85 Fleetwood FWD
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728 Posts
We used to cool the intake manifold on the SB Chevys with dry ice at the drag strip, for a denser air/fuel mixture, and it did help. Anything like that would reduce mileage though, so we are sort of stuck with what we have.
 

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1990 DeVille
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181 Posts
Discussion Starter #7
The idea is that the car would run fine on regular except for 0.1% of the time when the hammer is down. If the ECU can be fooled into thinking the IAT is reporting cold air at those moments, the system will go rich - and that will cool the combustion chamber and reduce pinging. As mentioned, the resistor would be switched into the circuit only when the car approaches full throttle.

Does this make sense?
 

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White Diamond '03 DHS (with DTS floor shift)
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Everything on these cars is computer controlled and intertwined. Usually when you try to fool them, you end up causing more trouble than you fix. What engine are you talking about? What are you trying to accomplish? Run faster? Run regular? As mentioned, I doubt it will make you run faster. Maybe just the opposite. I seem to recall someone doing that before and having that effect. Sub may recall it. If you are trying to run regular, what are you accomplishing? Cheaper gas (regular), but more of it (richer). Personally, I'd leave it the way the GM engineers designed it.
 

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1990 DeVille
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181 Posts
Discussion Starter #9
When you say "intertwined", perhaps you're talking about the combination of input sensors (IAT, MAF) and output sensors (O2), which the ECU reads to control fuel from the injectors. It's not really a closed loop system, nor is it very complicated.

I have experience in successfully modifying and racing an '87 Buick Grand National (hi 11's) that is not less complex than my '90 Deville, so at least I know which end of the soldering iron to grab. The simple modification suggested above is not designed to achieve more speed, but to permit safe usage of low octane fuel while preserving the performance of the car when it's needed. Going rich will reduce pinging, but I don't know whether the difference will be significant. This little modification probably won't damage anything - and, of course, it can be reversed in seconds.
 

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White Diamond '03 DHS (with DTS floor shift)
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Well, it sounds like you know more about it than I do, but as I mentioned it seems futile to me. If in order to burn cheaper gas, you have to burn more of it, you are not accomplishing anything. In fact, you might burn so much more as to actually cost you MORE. Just thinking out loud.
 

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69 Thunderbird | 90 Seville | 03 Corolla | 89 Marquis(scrapped) | 72 Torino(scrapped)
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This is a shot in the dark, but..... Is it possible to use a racing ignition box that can retard/advance the timing from the drivers seat? Maybe something designed for use with boost/nitrous? You could retard for regular and advance for premium. Just a thought.... I dont think it could improve hair growth, though...
 

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1990 DeVille
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Discussion Starter #12
I installed a timing controller in the Buick - it worked well, but was costly and complex.

In this Caddy, the end result will be the same amount of regular gas as the high-test gas that I'm currently using EXCEPT when the throttle opens wide and the IAT resistor is kicked in, thus enriching the mixture. It will happen ONLY under conditions of hard acceleration.

I drive pretty sedately, so expect no significant change in mileage.
 

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70 Deville 77 Fleet 78 Seville 92 Deville 03 Deville
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So your car pings on regular fuel Notaguru? You must live in a hot climate. Why not try a cooler thermostat? Up here in Maine it rarely gets in the high 80's and my Deville never pings on regular. Maybe stop and go driving in heavy traffic will get them hot enough to ping but my car doesn't see much of that. Maybe it's just carboned up and needs a good flogging. It sounds like the GN runs nice; another nice ride.
 

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1990 DeVille
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Discussion Starter #14
So your car pings on regular fuel Notaguru? You must live in a hot climate.
It pings only on the combination of REGULAR GAS + HARD ACCELERATION. That's why (today, hopefully) I'll install that experimental circuit, squirting additional fuel only when past 3/4 throttle.

I don't know whether the ECU response to IAT changes is instantaneous, but will find out.
 

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97 ETC
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The best thing to do here is make a true cold air intake system. I dont mean these underhood metal jokes that they sell on Ebay which they dont make for ETC or anything like that. now to do this you need to know you will have to clean it monthly. I made one in 02 for my 97 ETC as I was board and wanted to see if i could do it....

Well I did and on a whole it lowerd intake temps greatly and depending on ambient where it is and really makes a big differance in the midrange and I did pick up almost 2 MPG HWY. I left the air intake sensor under the hood but its in a 2' 4" I think cant remember PVC tube that conect to the original flexable coupler and the other end i have attached to flexable dryer duct hose that goes out thru the headlight assem. to the front of the grill. Then i mounted a 10" K&N filter to the center support and its half in the grill and half under the bumper cover.

I also sheilded the radiator and hoses from the intake ducting also with flashing so the even on hotest day at idle it its still cooler then was before. i cant remember exact numbers but performance is what i looked at also. I used my Snap On MT2500 scan tool to monitor things when i did this and also used a seat of the pants and then milage as I am always on the road. now being out fron tlike this requires maintance every 4 to 6 weeks. I clean it,if not after 8 to 10 weeks mileage drops ...I guess milage wise I am saying about 5 to 6 thousand or depending on your driving. Its outfront and if it looks nasty then clean it.....so there you have it you want something you need to give up something. Colder true intake air will give you many things but fooling a sensor will only fool you in the long run and probably cost you more in the long run with fuel,O2 sensors and cat problems........

I have run what ever is the cheapest meaning 87octane since 2000 and never have I heard the 1st ping. I live in the Crolinas so its hot here...You have other issues if you hear pinging in that engine.....still 28mpg at 75MPH avg 238,000 miles and yes it burns oil.....leaks it too but runs great still
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Clever way to resurrect an old thread............

What did you use to measure before and after air duct temperatures in order to determine that your modification actually resulted in "greatly" lowered temperatures ??

A handy gadget is available at www.scangauge.com . It will blow all so-called "CAI" myths out of the water. Just call up IAT as one of the display gauges.
 

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69 Thunderbird | 90 Seville | 03 Corolla | 89 Marquis(scrapped) | 72 Torino(scrapped)
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The best possible CAI for your car came from the factory. The point is to pull air in from outside of the engine bay and as long as the intake can flow equal to or more than what the throttle body flows at WOT then there can be no more improvement. If your TB flows 500CFM and you install a pipe in front of it that flows 1,000,000 CFM, you successfully accomplished NOTHING. A chain is only as strong as its weakest link.
 

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1985 Sedan DeVille
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1,883 Posts
The OP was asking about mods to the MAT although the thread has drifted to "real" CAI. First of all using a resistor is kind of silly since you can just move the damn thing to somewhere else that has colder air. Second fooling the computer will work right up until the car enters closed loop at which point the O2 will probably cause the computer to lean out the mixture again. So it's pointless to try and trick it unless you have made other mods that are causing the car to run lean during open loop.

A real CAI will improve performance a bit but you won't be winning NASCAR or anything. Seat of pants dyno may be worth the price, that's up to the owner. A good AEM dry-flow filter in the stock housing is probably the smartest thing you can do here.
 

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69 Thunderbird | 90 Seville | 03 Corolla | 89 Marquis(scrapped) | 72 Torino(scrapped)
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The factory air filter and intake already flow more than the engine can use. Aftermarket intakes are louder which only adds power to the placebo effect. The only time you get any gain is when you upgrade the heads, cam, bore, stroke, etc at which time the factory intake becomes the choke point.
 

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White Diamond '03 DHS (with DTS floor shift)
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Keep in mind that not only is the factory intake system already breathing "cold" air, but it is also routed over the PCM under the air filter box to cool it. They must have done that for a reason, don't ya think.
 
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