[2001SL2]

I know this has been called snake oil many times on the net and by some members on here.

THe mod involves installing a resistor on the connector of the Intake Air Temperature sensor, which would force the engine computer to make the engine run richer, because "air coming in is very cold" (thus dense, thus more oxygen and thus more fuel is needed)

Kidong once wrote that the only difference it might cause is the engine to run about a 3% richer mixture than usual.

But....what if?

I know the ideal stochiometric air/fuel ratio is about 14.7:1, but from the chemical formula its actually 15.1:1. So if that is the limit for the oxygen sensor, using a resistor appropriately sized would push the limit of at least the first oxygen sensor, and run the engine just slightly richer than usual, and possibly increase the power slightly for $0.99 (5 pack from Radio Shack)

SO, from the table I saw regarding intake air temperature and resistance of the IAT, installing a 1/4 Watt, 4.7 k Ohm resistor, would make the computer think that air is coming into the engine that is about 28 degrees F.

SO the computer tries to run the engine slightly richer, until the Oxygen sensor tells it to back off the mixture a little because it is too rich.

BUT the air coming in is still "VERY cold" according to the fake IAT (resistor) so it HAS TO keep the mixture at a maximum rich limit...

So according to the above info, what do you all think? My butt dyno says there is a slight difference, even running the A/C on (defroster), which usually kills the engine performance.

Comments / personal exxperience?

Again I used a 1/4 Watt 4.7 kilo Ohm resistor. Different resistors will yield different results. 4.7 k Ohms is just about the highest resistor you can run before there is a Check Engine light. If the resistance is too high it will make the computer think the sensor is disconnected completely and trigger a CEL

 

[DJ Sueno]

I think it's a waste of time and money...

For one, the car probably already runs rich enough as it is.... and if that's the case you will actually lose performance.... You would need to data-log the air/fuel ratios all across the RPM range with a wideband to see if there are any real benefits to it... I think it's in your mind that you are feeling a difference...

What you did is probably sold on Ebay and other websites as a cheap mod that "claims" to be a performance product...

I would remove it...

Anyways, that's my .02 cents about it...

 

[bell]

yea i'd pull it, you don't want to run TOO rich as you could "wash" the cylinder walls oil.......although if it was that rich you'd smell it

 

[2001SL2]

I really don't rely on my brain or butt too much, cause they are very subjective of course. So, I am just basing my assumptions on factual information about sensors and basic engine operation.

Yeah, they sell junk like that on Ebay, but its one size fits all. THe resistor I am using is 0.25 watt, according to my calculations, the perfect one for 28 deg F needs to be 0.032 watt, but 1/4 is the lowest they sell so oh well. But 4.7 ohm is about the lowest limit without Check Engine Light.

That's the thing. Even with the resistor on, with the engine thinking the incoming air is 28 deg F, there is no smoke visible at WOT, and it does seem the car is more responsive even with A/C on.

I know, I know, butt dyno junk etc etc, but I CAN tell a slight difference. My custom large diameter exhaust is routed out the passenger side, right behind the tire (gotta update pictures in album) and like I said, no visible smoke, or strange smells. No audible knocking or pinging so far, either.

I'll keep you all posted as far as gas mileage goes.

ANother possible alteration would be adding resistance in line with the MAP sensor, or slightly reducing the pressure in the intake plenum by adding a spacer at the Throttle body, thus adding volume to the plenum and lowering the pressure measured by the MAP sensor slightly.

Either of those, like the IAT, would tell the ECU to keep the injectors open slightly longer, within the limit of the first oxygen sensor.

Yes, I am not putting more air in the engine, to need the extra rich mixture, but if I do the RAM air intake, some other member made, and add some pressure to the stock air box at high speed, I may see more of a benefit.

And yeah, I have no way to data-log anything. As for washing the cylinder walls, I don't think its running THAT rich

 

[Rav4jptrk]

I would't mess with the sensor. You will get less MPG, and in the long run damage something.

A little note, my RAI adds about 2.1 PSI at 60 mph. recently a friend and I hooked up a vacuum gauge temporally to the intake manifold. One run we did without airbox (just a cone filter) then we did it with the modded airbox. However! you must keep in mind, that with my mod the computer will compensate for the leanness in the higher RPM range, automatically adding more fuel, same thing when you push the gas down harder in lower RPMS (and not change gears). BUT in curious as to what the combo of the modded sensor and my modded airbox would do together. try it, and if it don't work so great, it don't works so great, and go back to the drawing board.

good luck

 

[2001SL2]

^^ THat's the guy with the RAI, sorry couldn't remember your username... :lol:

Actually, the MAP sensor increases fuel delivery when pressure drops in the intake plenum. WHen you open the throttle plate.

SO if there is higher pressure than normal at WOT, because some air is pushed in from the RAI, the MAP sensor won't sense such a need of fuel, because its as if the throttle plate is not as open as it is, or there is a leak on the intake pipe (between the air box and throttle body), and the engine will run lean.

SO just running a RAI, that actually works as a Ram air intake, may make the engine run lean, at high speed that is.

I never thought of that actually..... interesting 8)

 

[Rav4jptrk]

SO just running a RAI, that actually works as a Ram air intake, may make the engine run lean, at high speed that is.

EXACTLY! thats how I got a 3 MPG increase just have to keep the foot off that pedal! but now when you get in it...hang on :twisted:

oh and our rav4s don't have MAP sensors

 

[2001SL2]

SO just running a RAI, that actually works as a Ram air intake, may make the engine run lean, at high speed that is.

EXACTLY! thats how I got a 3 MPG increase just have to keep the foot off that pedal! but now when you get in it...hang on :twisted:

That's funny. SO forcing the engine to run rich, will balance out the leanness of the RAI..... 8)

I'll find some time to make myself a RAI like yours. But since I don't have the turn signals in the front, I may just get the air from that hole, under the headlight. I am thinking about molding a scoop out of PVC using a heat gun..... and maybe some duct tape :lol:

 

[Rav4jptrk]

you want it to be the most direct as possable - you want the air to be being rammed into the airbox, if you have a few turns it slows the speed down, which reduces the effect. cold air sinks in the roads...lower intake point the better. hhehe, duct tape use #783,647,211: to keep a cars intake together

 

[DJ Sueno]

oh and our rav4s don't have MAP sensors

Where did you get this misinformation ? Did you remove yours? :shrug:
Last time I checked my engine bay, mine still has one... onder:

 

[2001SL2]

MAP = Manifold Absolute Pressure sensor. They are present on 2000 and earlier models. It is installed on the firewall, right above the extreme left side of the intake plenum.

2001 and later models have a MAF sensor, Mass Air Flow.

Yeah, from the turn signal area it may have a turn more but the air pressure going in depends on the size of the intake and position (aerodynamics of the car at that position), and I really think that is a better position. We'll see what I can figure out

cold air sinks in the roads...lower intake point the better.

Not necessarily. The heat reflected by the asphalt creates a hot air boundary, a few inches to a foot I imagine, above the road surface. Above that the temperature should be fairly constant so that is not a big deal. Plus a lower intake is more prone to suck dust and dirt lifted by other people's car tires



Sorry that ^^ was my Mechanical Engineer coming out :lol:

 

[2001SL2]

Ok, I did the RAI. Not with duct tape but with gorilla tape. And the duct stuff is just because its durable and very flexible, kind of a tight fit in there.

I had cut out part of the sheet metal behind the headlight in the past, so I got room to pass that duct through there. I tried it by blowing a bit of air at the scoop, and I could feel it moving into the airbox quite a bit so, it must be working just fine.


Results? Torque seems a little more constant. The engine seems to pull a little bit better, like when passing a car on the highway. With a butt-dyno that is.



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[Rav4jptrk]

looks great! umm it looks a bit funny with the intake point being the turn lens :lol: but if it works great, function over looks :thumbs_up:

I noticed the most gain in power at around 45 mph what do you think - that translated into between 1750 RPM and 2300 RPM

I noticed another gain of power around 70 MPH or between 2750 and 3500 RPM

I also noticed that the engine accelerates faster from 3900 RPM+ at any speed

do you agree?

 

[2001SL2]

looks great! umm it looks a bit funny with the intake point being the turn lens :lol: but if it works great, function over looks :thumbs_up:

I noticed the most gain in power at around 45 mph what do you think - that translated into between 1750 RPM and 2300 RPM

I noticed another gain of power around 70 MPH or between 2750 and 3500 RPM

I also noticed that the engine accelerates faster from 3900 RPM+ at any speed

do you agree?

Agree.

I quote you cause my observations are about the same. I am not too sure as far as speed, but I did feel more torque above 2000 rpm, and at highway speeds, 70 mph or more, 2500 rpm or more on overdrive, it is a bit easier to pass without going pedal to the metal.

It struck me that on first gear, even around 30 mph, around 3500 rpm the engine suddenly pulls hard. It definately allows the engine to breathe a lot better at any speed.

 

[2001SL2]

I was thinking, something else to consider about the IAT stuff and ECU measuring fuel delivery is that my car is a CALIFORNIA version. THerefore the upstream oxygen sensor in my car is not an oxygen sensor, its an air/fuel ratio sensor.

Instead of pulsating like a regular oxygen sensor at stoichiometric ratio, the air/fuel ratio sensor tells the ECU exactly what the air/fuel ratio is by varying the voltage output. So IT COULD BE that the ECU in my car gets more information and reacts more precisely, thus there might be a difference regarding how my car reacts to mods and how you all's does, just a little bit, like with the IAT.

I dunno why they would sell a CA version in Maryland. Baffles me :?


Here's how it looks from a distance

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[2001SL2]

Well, as an update, I got 22 mpg today, mostly city. THat's about the same I get most of the time, although this time I got stuck in a lot of stop and go traffic during the week so its a little lower than usual.

I'll be doing mostly highway this week so I'll post another update.

So far the engine does not seem to be running horribly rich

 

[Rav4jptrk]

does your engine sound like this when accelerating in 2nd gear?

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[2001SL2]

SImilar, mine has a different rumble. I'll try to make a vid. WHat's up with the check engine light being on?


So your range with the most power increase is about 2500 to 3500 rpm? Of course when you stomp on the gas it almost goes to 5500

 

[Rav4jptrk]

SImilar, mine has a different rumble. I'll try to make a vid. WHat's up with the check engine light being on?


So your range with the most power increase is about 2500 to 3500 rpm? Of course when you stomp on the gas it almost goes to 5500

cel is for stupid emissions....it for some reason isn't affecting power, or fuel ecomomy, so it don't bother me

I was showing the acceleration, when im on 70mph highways (~2700 rpm), it doesn't shift down like that, and stays in overdrive and PULLS

Keep in mind I also am staying within legal speeds :wink:

 

[2001SL2]

Alright her's my video, accelerating from about 45 mph to 75 or so

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I dunno if you can measure how long it took for my car to hit 60 from 45 mph, but I think it took mine less time