I was thinking of trying to fool the Intake Air Temperature (IAT) sensor to reading a lower value.

The reason behind this that I believe our ECUs are very conservative when it comes to ignition timing. Especially in the summer months, I notice a huge drop in power, mainly at the top of the rpm band. In the morning, when the car is cool, it pulls hard. Once everything is heat soaked and hot, the response and power drop off rapidly.

I remember someone make a device for mustangs that would allow you to set the te,perature that the computer would see. By setting a temp of 75 degrees on a 90 degree would prevent the ECU from pulling the timing back so much.

For obvious reasons, you wouldn't want to be stupid about it, but some added timing could be put back in without running into a pinging problem.

If the Infinti system works simlarly to the Ford one, a variable resistance (resistors) could change the voltage signal being sent to the ECU which controls the IAT.

So, who is going to get to work and make a prototype???!!!???

 

its funny cause i too was thinking about this same thing, not sure how to go about it though, i am sure it is just a simple voltage fix, but not sure how much you would want to throw it off before it hurts more than it helps...

 

it would take a little testing to see what voltages the IAT sends at different temps. This could be a cheap effective aid for us florida guys.

 

All you need is one of those 99 cent performance mods on ebay. Its the same idea.

 

I wouldn't bother. It won't make any difference plus I believe the IAT is intergrated into the MAF on the VQ35. On my Maxima, the IAT was a seperate unit plugged into the intake pipe. Fooling the ECU into thinking it's colder outside than it really is does the following:

1) Adds more fuel because the ECU thinks the air is cold and dense. If you think about it, why would you want to do this in hot weather? Adding more fuel to less dense air (less O2) makes for a richer fuel mixer. Rich fuel mixtures = lower power.

2) Increases timing because the ECU thinks the air is cold. Same deal as #1. This isn't good because increased timing in hot weather leads to one thing, detonation. Once the knock sensor picks up on the detonation, the power goes down a lot because the A/F ratio is richened and the timing is dialed back dramatically to cool the combustion chamber (ie stop the detonation).

There's no way of getting around with laggy performance in the warmer months. The air has less oxygen, the air is hotter, and once the engine heat soaks, you're loosing power. Fooling with a sensor won't help these things.

 

Dave,
It's my understanding extra fuel by itself acts as a coolant inside to combustion chamber. I guess the question would be if the added fuel would be enough to offset the higher ambient temps in the summer. If it is, and you can keep full timing, then it's a helluva thought.

In this case, I would be interested in hooking up something like the UTEC to datalog what happens. Apparently you can get knock values from the thing. That would tell you in absolute terms if timing is being pulled.

 

I thought about this because I have feeling that the ECU is ultra consersative when it come to ignition timing.

 

Exactly right. Richening the fuel mixer cools the combustion chamber. Take a look at any aftermarket SC/turbo system and you'll see that the way they get around the stock NA ECU programming and induced detonation under boost is to saturate the combustion chamber with a ton of fuel. It works, but it kills power. That's why tuning these aftermarket forced induction kits the right way is so expensive.

As for richening the A/F in the summer, the VQ is already doing it to reduce the detonation and you see where that leads...less power. On an OBDII datalog, you can see the A/F ratio richening fuel and the timing getting lowered as the air density lowers (higher temps). I've logged things like this before with my OBDII/laptop.

If you want better performance in the summer, run higher octane (93+). The higher the octane, the more resistant it is to detonation. SCC magazine saw a 8whp/5wtq just by using 100 octane vs 91 octane on their project 350Z.