It is understood that cooler air coming in at speed increases engine performance. The air intake sensor, located on the intake tubing (stock) or CAI tube (aftermarket), reads incoming air temperature and translates this to the ECM, and the ECM goes with it from there making necessary adjustments.

What would happen if you removed the air intake sensor and always supplied cold air to it, irregardless of what the temperature really is? For example, if the sensor were kept in a cup of ice at all times, and the sensor read 32F, but the air actually coming in was 100F, would the performance improve or would there be problems since the air actually coming in is warm?

 

You would definately lose power, potentially foul your spark plugs or a run lean situation (fuel is a key component of engine cooling). Either way, your Max's computer won't be able to "fine tune" the mixture to adjust for changing air temps and the engine
will definately run worse.

 

I have done this on another car, though not as extreme as putting the sensor in a cup of ice. I found that adjusting the sensor resistance using a pot in series was a reasonable way to richen the wot mixture a little. It will have relatively little effect under normal running conditions. Of course, you need to monitor the exhaust to get it right.

 

Altering the resistence values is what I meant, not actually using ice. The sensor converts temperature to a resistence value and passes that along, so I am suggesting the sensor value be hijacked, so to speak, electronically.

 

This mod is more effective on a forced induction car. When using a S/C or turbo (hell, even on spray for that matter), you run into lean spots, if you have increased the boost from stock levels and haven't touched the fuel system.

This is where altering the resistance of the IAT sensor comes in handy. It will trick the brain into thinking it's cooler, and deliver more fuel.

So yes, your idea works. It's just more effective on boosted cars. Alot of GTP's do it. Nothing like a 55 cent mod to drop a couple hundredths.

 

Look at a Nissan service manual. The intake temp sensor is ONLY used for diagnostic purposes...the temp is read to aid in troubleshooting ONLY. It is NOT used by the ECU for any adjustment purposes.

Altering this signal output would therefore result in no changes to the way the engine runs. It's a good idea that works on other cars (like GTPs that use this signal to alter ignition timing), but not on the Maxima.

Our MAF sensor and O2 sensors are solely responsible for adjusting fuel settings. The ignition timing is pre-set and is not altered by any sensor inputs (with the exception of the knock sensor, which is not used for "adjustment" purposes but rather "fail-safe" purposes).

 

I'm bumping this b/c Nissan is full of ****ing ****!

On my '02 and now my '03 the cars are SLOW when the air temp outside is over 70. If it's 70 or cooler it runs decent for the pos stock ecu. The hotter it gets the slower the cars gets linearly. And no, it's not due to less dense air. I'm losing about 50 WHP (at the least). ****, I think a stock maxima would smoke me with temps over 85-90 degrees.

I just tested it with a resistor simulating colder air. At WOT the car barely accelerated. A geo metro could've tied me. For the IAT not doing anything that sure is a big *** difference. Knock sensor is simmed and it doesn't matter if I use a brand new maf or not. It's 4 banger slow.

I'm removing the IAT. **** that pos. If it doesn't do anything then I guess the ecu won't care when it's gone, right?

*pissed*

If I wanted to drive a goddamn civic in the summer, I'd ****in buy one. Not tool around like an ******* in a slow *** v6.

 

:/
ummmm.ok. you think you have another underlying issue?

 

I have a similar issue however I really doubt messing with the air sensor would help. In the mornings when its around 60 degrees, my car is a beast and shifts quick, however in the afternoon once the car warms up it feels a lot more sluggish and delayed

 

Across 3 motors, 2 ecus with bypased KS and new MAF?

Nope, sounds like some retarded nissan crap. I think they should be world famous for making great engines and then tuning them so they run like ****.

I'm pretty sure the general consensus of the VQ is that it slows when hot, but mine are always abnormally slow.

Mods that matter are: CAI/H/test pipe/E, NWP spacers, UDP, SSIM (yeah, weak for stock ECU I know)

 

I agree with Child_uv_KoRn. Back in January when I first got my Maxima, it would break the tires loose in 1st gear (4AT) when the VIAS valve opened. It was totally stock; I hadn't even done the GAB mod at that time.
Fast forward to now. It's 85+ degrees outside during the day, and I wouldn't say it it's as slow as a Geo Metro, but it's definitely slower than back in January. I have a SRI and exhaust resonator delete now too.
Why do VQs lose so much power in the heat?

 

If you think the heat affects performance bad at low altitude you should see what happens at 6,800'! My Dad used to be a private pilot and one of the most important things to check for in the summer heat here is density altitude. He had a small single engine plane and wasn't even allowed to fly if the temps hit 90F. If the air temps are 90F here the D/A is well over 11,000'. My car is almost undriveable here in the summer when the temps hit 95F and the A/C is on. I have to rev the engine to 2,000 rpm and let the clutch out slllooowww to avoid stalling.

Here's a great calculator to help you realize the effect heat and altitude have on a car's performance. Using this I can see that at 90F here my car only produces about 73% of the power it produces at sea level. It only shows a 3% loss in power at the same temps at 100' elevation.

http://wahiduddin.net/calc/calc_hp_dp.htm

 

^ Thanks for that link! That's really interesting. What I don't understand is why VQs are so sensitive to heat. My last car was a 2001 Toyota Celica with just 140 HP, and it felt equally slow regardless of the temperature. My Maxima on the other hand, was breaking loose in 1st in the winter, but can't even do that now despite being having a SRI.

 

The IAT sensor is actually a thermistor that's built into the 5.5 gen MAF.

You should hook it up to a scanner and log your ignition timing. You may have bypassed the KS wrong, if you don't have a good ground it will effectively give you limp-d1ck timing. Or just dyno the car on a Dynojet 248C, Dyno Dynamics, or Mustang Dyno so your numbers are comparable to someone on this board.

 

i say go for it. just take it out and let us know how that works out for you, we all cant wait to see what you find when the ECU can no longer target the correct a/f map

 

i call on this and here is why i think the air intake temp sensor DOES affect performance.
i believe that the air intake temp sensor on the VQ (along with the KS) is additional insurance against detonation.
i say this because being a former die hard LS1 owner, the 1st cheap mod that every brand new LS1 owner would do is the famous "air intake temp sensor mod". there are two ways to do it. one was to either pull out the sensor from the air box and shove a 500ohm resistor (i think, could be off) in the plug fooling the ECU to think that there is constant cool air coming in. the other way was to relocate the IATS alltogether to a "cooler" location. here is a link (out of many) of free LS1 mods. scroll down to modification number 3.


http://www.ultimateresourceguides.co...-freemods.html


i honestly believe there is a way to "fool" our ECU as well and trick it to give us a better fuel curve for optimum performance. again i could be wrong..but i seriously doubt that Nissan put it there just for "troubleshooting".

 

Its was 96*F today, and I have 100% stock maxima. I can roast those tires with out any issues. I don't think there is big difference in temp wise.

 

I unplugged my IAT sensor (since I have a 5th gen. On 5.5s you can't really do this, read my above post for more detail).

No change in SHORT TERM performance/driveability at part-throttle or WOT. It threw a code for IAT sensor failure since it wasn't receiving a signal. Plugged it back in 15 minutes later. I wouldn't leave it unplugged long term,

What the FSM says could be true The MAF/O2 sensors read airflow at part-throttle, and then the MAF reads airflow and KS keeps timing in check and then above 5000 rpm the KS steps out of the picture and runs a constant timing map.

Every engine is different, so the LS1 IAT sensor works differently, same with the GTPs, from my experience the knock sensor has more of an effect in making the car feel like a dog in hot/humid weather than anything.

 

unplugging the IAT is not the solution. all it's going to do is throw a code as you mentioned and maybe even send the ECU into failsafe mode making the air/fuel ratio "pig rich"
but we need to find out what "ohm resistence" sends the signal to the ECU, tricking it to give an optimum fuel curve all the time.

 

Put my stock intake back on this weekend after it was hot all of the week before.I was losing hp and car was driving alot slower....got some power back but miss my growl and upper rpm power, still A beast IMO now. Im gonna go to homedepot soon and make A custom heat shield for my intake.

 

now thats a project worthy of a whole 'nother thread!

 

Never said it was the solution, my IAT sensor is plugged in, no codes. Just reporting my experience.

Well that only depends on how the Nissan A33 IAT sensor works. All IATs aren't created equal. The FSM is probably right, someone could give it a shot, but it's more useless than grounding the knock sensor.

 

well we should get to work and find out more about this sensor asap!

 

I can plug in the KS and it makes zero difference. I just do it b/c I know how dumb the ecu is. I'm not giving it any chance to retard timing...yet it does it anyway.

I'd love to dyno it and prove it, but that costs cash, but trust me. When cool I can accelerate from 0-20 with a tap of the pedal. 20-40 when warm mashed seems to take forever. I literally have plenty of time to wait for the rpms to climb in 1st when warm. That should never happen in this car. While the max is no super car, it should push you back in the seat. Good luck with that when warm. All noise and no go. There's not even any torque steer. The power band feels mostly unchanged from low to redline. It's just a very smooth rise. When operating "normal" (for lack of a better word ) it's half *** down low from the SSIM, then takes off when it hits 4k.

I removed the IAT and contrary to all logic and belief, NO CEL! It drove about the same as usual for 87* (hot *** nights). I'm not sure what that means.
I'm thinking that the resistor was simulating too cold of a temp (below freezing). I'm gonna try for something around 50* tomorrow.

If I can get a hold of a consult... I DEFINITELY will test this **** out completely and report back.

 

Damn dude, chill out and blow your car up.

Any how, only reason I'm posting is to sorta verify/confirm the altitude thing. My UNC #'s for my dynosa re about 28-30% lower than their SAE counterparts @ 5200'.