I have this on my car as well.

 

I do agree that the factory sensor is not only fast but it also accurate, if you could or make a flange in the IC piping for it that would be better than replacing it.

However, I do disagree with your logic as to why the external sensor is wise to add. The explanation starts with our cars are not using a MAF so we have to resort to speed density management. The trouble is that you have to estimate the mass flow of air into the engine is by analyzing the temperature and pressure. Now if I am not mistaken the factory ECM can measure barometric pressure to help accurately determine the actual mass flow but I am not so sure this is available in the EMS. Regardless, if you are FI then you need to be able to measure and accurately track mass flow which can change very rapidly and several people have shown the intake sensor cannot accurately report temperature changes during compression you will have to interpolate based on the available readings. You can use the factory sensor and set the breakpoints in the intake temperature sensor tables in small increments around the normal operating temperature. The difficulty is that this point floats based on ambient temperature and unless you live in San Francisco where it is sunny and 70F everyday you will be off a bit as the weather changes. The other example where the factory sensor would be acceptable is when using an Air to water aftercooler that maintains a more even temperature. By using a sensor in the intercooler piping you can get a more direct picture of what is happening without interpolating. Contrary to the above this will allow for a more linear temperature scale that is more accurate for larger ranges of temperature. I offer my final argument on the fact that intake temperature sensors on newer cars are nearly all mounted in the air intake rather than the manifold. Now if it was more advantageous to have the sensor in the manifold they would not have done this.

 

I'm not sure if you can use that as a "final" argument. Honda has been all over the map in regards to their IAT sensor placement.

They started in the intake manifold, then moved it to the intake tube, then back to the intake manifold, now you are saying cars are putting them back in the intake tube.

You can argue it either way.

 

aem does have a baro pressure sensor built in, but like everything else you have to set the corrections that it uses.

the good thing about ait's being hot is the fact that you can set a flat correction over a certain temp. hotter air will make the car run richer, however the extra fuel will keep it from detonating as easily.

as i said before, ait corrections are usually so small that a "quick" reaction to a 10-20 change isnt "really" needed.

if you go from 20 deg temps to 80 deg or 120deg then yes you will see a good amount of change, but from 100 to 120 or 130 its not going to matter.

Typically i dont lean it out any when the temp goes more than 20 deg above what i have tuned the car at, but i do add fuel as it gets colder based on a pretty set correction that i have come up with over the years of tuning things.

 

[QUOTE=siadam,Jul 17 2009, 11:53 AM] I'm not sure if you can use that as a "final" argument.

 

I apologize I must explain better.

We are talking about optimizing the tune and as with anything there are compromises to be made. So in the case of FI and more specifically a turbo, you can optimize the temperature measurements under boost by mounting the sensor outside of the manifold then interpolate off boost conditions. Alternatively you can retain the sensor in the manifold and create a tune better suited for off boost conditions and interpolate to boosted conditions. A good tuner should be able to create a good map over time in a range of conditions this way but this will take time and require an iterative approach.

For a more optimal tune, knowing the temperature under boost is very important. The mass flow is changed greatly by the heating which is illustrated in the below graph.

As far as the sensor goes, I honestly have no idea about Honda's but this is exactly what GM, Ford and others have done. I unfortunately, have less specific knowledge on Honda and substitute my general automotive knowledge to cases such as these.

Thanks for all the great input

 

Air temp compensation is very important if you want a correct tune.

The Honda sensor does NOT respond fast, i've tested this numerous times. It never has to, Honda's never see quick swings in air temp in the stock configuration. That does not hold true anymore with a turbo or supercharger.

In back to back testing on my car, with an OEM Honda sensor and a GM open element sensor, there was a 12 second delay between the GM one which was right on par and the Honda one, which was slow.

As far as placement, if you have an AEM, you want the sensor a little before the throttle body.

When it's in the manifold, it does get heat soaked and it is true that the manifold heats up the air going into the motor. The thing is, the amount of air picked up from the manifold changes drastically depending on air speed. At idle and cruise, the air temp in the manifold is pretty accurate to what's going in the cylinder. At full throttle, it's not. The Honda ecu has air temp compensation tables based on air speed. Since you don't have that capability with an EMS, you're better off with having the correct air temp when you're under power than at idle and cruise.

 

your OEM sensor was broke if there was a 12 second delay, that's just nuts. when you do a run and let off the gas at the end there's a delay but that's just the hot air trapped in the intake manifold from all the vacuum. in my experience with all motor the light loads with lots of vacuum that's when the temps are high. all motor as soon as you get on the gas the temps will drop as it gets fresh air and vacuum isn't pulling air from the cylinder. any other delay I believe is the time is takes to cool the manifold and get the manifold to the point where it's not hurting the air temps.

it's kinda like the AC in your car on a hot day. just because you get into your car and turn the AC on full blast doesn't mean the temps in the car will automatically match the air coming out of the vents. it takes time for that volume of air in the car to cool down. plus all the surfaces in the car are radiating heat, just like the inside surfaces of the intake manifold and all the runners would be doing. moving the sensor in front of the throttle body would be like measuring trying to measure the inside temp of the car with a thermometer just outside of the window.

boosted there's so many variables, with a really good intercooling system you may not see a rise in intake temps in boost but most likely you will. and mostly likely that change in temp will be gradual and over time as the whole intercooling system gets heat soaked and starts to lose efficiency. pretty funny on camuman's car with the AEM water injection the temps drop in boost, pretty cool

looking at logs I have with the OEM sensor in the manifold I see temp changes within .3 seconds on an all motor car the moment the throttle body is closed on a dyno run. considering that the resolution on the IAT sensor is 1.8 degree increments, so it has to change 1.8 degrees before the AEM sees a change in voltage. I think .3 seconds is pretty quick, quick enough for a sensor that's not super critical to the tune of the motor, not as critical as the MAP sensor for example. don't believe it's that quick? take it out and breath on it, you'll see the AEM jump like crazy, not 12 seconds.

 

Call it what you want. I've tested it and come to the same conclusion multiple times.

It's no secret that an open element sensor responds much quicker than a closed tip sensor.

I've done the same comparisons with the GM sensor and the Bosch air temp sensor, which is a closed tip sensor and the Bosch is VERY similar to the Honda sensor in response.

 

Sorry, just looked back at the logs from the Bosch sensor, it's not as bad as the Honda one, but still pretty slow. It's about a 3.5-4 second delay.