Tim,

No argument from me that the IAT1 is almost the same as ambient air with a fresh air intake set-up (JLP, etc) and the IAT1 from an open element filter will be several degrees hotter due to the engine compartment heat.

I will argue that the IAT2's with a fresh air setup are not as reduced as the variance from open element IAT1 to fresh air IAT1. I've witnessed it and datalogged it on very similar trucks. I discussed this on NLOC and Jody (camcojb) agreed that he saw similar results at times. Unexplainable but similar results.

If outside temps are 85 and the IAT1 is 85-86 on my fresh air intake while a similarly modded truck is seeing an IAT1 of 105 with an open element, the IAT2 will NOT show a similar 20 degree variance. I can't even tell you with certainty what the variance will be as I've logged spreads from zero to the fresh air system having hotter IAT2's.

What's the IAT2 number where the PCM starts retarding the timing? I think understanding this is more important than an actual number or spread. Staying below that number might be more relevant. And how does the PCM uses IAT1? I realize cooler air usually means denser air and with denser air comes more fuel, but isn't that determined by the MAS?

My logic tells me cooler air in should mean cooler air out and maybe it is. We can't measure the air temperature after the supercharger and before the intercooler, can we? That would give us some good data. Since the IAT2 is after the intercooler (aftercooler) we have to consider the efficiency of this device. I think it is high and my results show this.

I like the idea of providing the intake with cooler air, though. And I will keep my fresh air system for that reason. I might also start checking intercooler fluid temps after the fluid leaves the heat exchanger. If it isn't ambient (and I doubt it is), replacing the OEM heat exchanger or adding another one in-line might help the cooling capacity of the aftercooler.

Robert

 

That is why the IAT2's normally reported show less difference than the IAT1's. The intercooler removes a percentage of the heat. If the intercooler were 100% effective, it would not matter what IAT1's you put in.

But the intercooler is not 100% effective. So there must be a temperature increase -- just not as big as the increase in IAT1's.

I am concerned that the data is being logged with the OBDII sensors. I have never seen any data to indicate how accurate they are. That may explain the varying results.

 

Tim,

You have a point. They may not be accurate. I will add that my IAT2's did show a decrease when I added the fresh air box. I was able to log this and show the decrease. So, for my specific truck, there was a change between the two applications.

But what are the actual gains from a slight drop in IAT2? Again, how does the PCM use the IAT2? I've been told it uses it to retard timing at a certain temperature (and what is that temp?)?

Robert

 

We can spout theory and empirical data all we want, but what it boils down to is this...

Show me a better MPH and/or ET from a fresh air ducted CAI vs a 12" open element kit, and I'll buy one. It all boils down to real world performance.

I run a 12" open element filter. Is it because I can't afford a JLP or other fresh air kit? No...it's because it won't make any difference in real world performance, and I chose to go the that route to meet my goals. I think that is what most people need to understand.

 

Once again, my perspective appears to depart from most.

I consider a true "cold air" intake versus an open filter to be a reliability mod, not so much a performance mod.

A few degrees in IAT2 can make the difference between detonation or not.

 

Well said Tim, and I agree with you 100%. As long as my IAT2 stays under XXX degrees, I am very happy, because as you said, that helps prevent detonation. My IAT2's are low enough with my open element filter, so I see no need to change at this point.

 

I would love to install one of those Auto Meter dual-channel intake air temp gauges -- one channel between the supercharger and intercooler, one after the intercooler.

Memory max recall for both channels. Pimpy. I love gauges that don't have to be watched.

 

rmfreeze and I were talking about the best way to install a temp probe between the SC and the IC. Any ideas? If we can figure out a good way to do it, I am going to install one in there and get that setup. I would love to get some hard data like that. Then we could have IAT1.5 readings.

-Shawn

 

Maybe give Richard Holdener a call. He did just that in his Kenne Bell testing writeup.