I will no more tomorrow once the engine compartment gets HOT, but running around for a while this evening, it seemed to have that "cool weather power" longer than it normally does since i did this in the afternoon. Not bettin the farm yet but it for some crazy reason seems to be better, will post tomorrow

 

How, i dont know but for some reason, i have a little more throttle response, and seemingly a nudge of power all the way through the band. That cool engine compartment situation that eugene was talking about seems to be on full time now. Not quite as noticeable when the engine is HOT(95 degrees with 92 percent humidity) but ive got more umph when it is HOT. Im about to fill up in the morning and we'll see if it has any effect on mileage.

With out some intense testing i cant say for sure the benefits but i CAN say it doesnt hurt. We need more people who REALLY know how there truck runs to do this to get more data.

 

There's a good review article on the 6.4L in the new PSR magazine, and it explains how fueling is done almost exclusively by using the IAT1 and MAF sensor at the air filter, but they do adjust fueling some with the IAT2, which is what our MAT is called on that truck.

For any engine, the IAT1 along with the CFM going into the air filter inlet is what determines the MAF (lb/min) that flows into the cylinders. This MAF is given by MAF=CFM*AD, and the AD here is determined by the IAT1 and not by the IAT2 or MAT.

This MAF is really the # of air molecules per min that flow into the air filter, and these molecules get hotter as they go through the turbo, and then they get cooler as they go through the IC and into the engine, but their #/min and lb/min flow remains constant from the air filter inlet all the way into the cylinders. This is why it makes sense to use the IAT1 and MAF measurement at the air filter as the primary input for fueling.

Having a good IC to get a lower IAT2 or MAT just means that it takes less BP to push this given lb/min past the restriction of the intake valves and into the cylinders. That's why it makes sense to use the IAT2 as a secondary input for fueling.

 

I guess I missed the point of that one Gene. Are you adapting a MAF sensor to use on a 7.3, or is that general information?

 

Mostly general info, but I'm not 100% convinced that the 7.3L isn't using the IAT and BARO to calculate inlet AD and use that as part of the fueling command. I realize the manual says otherwise, but Jody mentioned to me that he's still learning new features of the 7.3L software all the time, so the manual might not be giving (or even know) all the details!

 

That's always a possibility. Shouldn't be too hard to check that one out. The guys in the gas world have been using a resistor in the IAT for some time to get the PCM to add fuel. Might be worth the effort to plug one in and see if anything changes. We know that resistors work in the ICP and EOT circuits, anyone ever test one in the IAT?

 

I'm going to relocate mine to the inlet pipe and see if it changes anything. Scott, you may be onto something, but makes me wonder how it might affect other things like GP's - especially in cold weather. I know the PCM cuts pulsewidth when the EOT is below a certian temp, and wonder what it does when the IAT is low as well.

 

Glow plugs shouldn't be an issue. The PCM is supposed to run them a maximum of 120 seconds. The actual, or perceived IAT should not matter past that point.

 

The bag of ice experiment would be easier to do, and you'd see a larger difference, if in fact there's any to be seen. Since Benny thinks he's seeing a difference by relocating the IAT sensor, you should see a larger difference my cooling it to 32 F, especially if you start with a hot engine that's been run for an hour, then do a couple of timed acceleration runs, ice the sensor and immediately repeat the times runs.

 

Well some things that I have noticed about the AIT, MAT, and MAP. Apparently with a chipped truck, they don't affect fueling and power output nearly as much as everyone thinks.

Last several times at Bandimere this summer I've been running 15.4X at 86.X MPH. Last night I was out there again with the best time still in the 15.4's and at 86 MPH. So what's different?

- This time the MAP sensor was reading correct pressures up to 23.7 lbs of boost. Last time I ran it was only reading up to 13 lbs due to a mis-adjusted Overboost Annihlator. So adding 10 lbs to the MAP sensor made zero difference to fueling.

- Temperature was lower. Last time I ran it was upper 90's for a high and track temps over 100 degrees. This time I was racing in the evening and night with temps in the mid to low 70's. A 30+ degree drop in temps did not affect times or trap speed.

So, for those of you who are wondering how much these sensors really affect fueling, well apparently it's not as much as we all were thinking. I was going out yesterday evening hoping for better times because of the favorable weather and a corrected MAP sensor reading, but it didn't happen. Kinda disappointing. But now I can relax and not sweat too much about these sensors.

 

The problem with your comparisons is that hotter air reduces HP, but hotter air also reduces aerodynamic drag force, which is a significant factor in determining your ET. Colder air increases HP, but colder air also increases aerodynamic drag force, which is a significant factor in determining your ET. So you have to be careful what conclusions you draw when comparing hotter vs colder air ET's. Dyno's give HP that's corrected for air temp and pressure, and to try and relate drag ET's back to HP is even more complicated than correcting raw dyno data.

I recently saw a post which basically said that when using AE to measure MAP, you only get a correct reading when in a stock tune, and that any chip tune gives a false lower reading for MAP. To me that means that any AE data taken with a chip will probably be in error because the chip is giving false information to various PCM data tables, which is how a chip fools the PCM into giving more fuel!

 

That very question was brought up to Jody last time he was here in Colorado for live tuning. Jody does not fool the MAP sensor reading, and doesn't see any benefit in doing so. Also my AE readings from the MAP sensor are 1 psi lower than my gauge from nothing all the way up to 23.7 psi. So yes, I do get correct MAP readings in any tune: stock, tow, econo, and extreme.

Please re-read my post where I said that MAP was reading only up to 13 psi. It wasn't the chip, it was the overboost annihlator. At 13 psi the PCM isn't seeing full boost, so my fuel should have been cut. It wasn't fooled to see higher boost by the chip.

 

Yeah, I find it odd Jody would sell me tunes and an OBA at the same time if he was fooling what the PCM was seeing. Maybe he was just fooling it down low and it is needed when the wick is turned up, but I did not get that impression.

Now on my restriction testing, I have noted that the AE map #s are significantly lower than my mechanical gauge. I may be turning that **** some the next time, right up to where I get an SES light but that will have to wait until my next logging run.

 

When I visited Jody in Asheville, I noticed that on his truck he employed the trick of relocating the MAP sensor to the turbo outlet so it would see a higher reading sooner, and make the PCM fuel sooner and higher during acceleration. He said that the effect of relocating the sensor wasn't dramatic, but that he could definitely tell the difference from his SOP meter. So the PCM definitely fuels based on MAP.

I had back to back dyno runs with and without a boost relief valve back in the days when I had my K&N cone and Banks Big Head and was making 27 psi boost, and I got 12 more RWHP with the relief valve, so I know that de-fueling is a real effect if the PCM see's too high a MAP.

 

That's a neat trick. I'll see Jody today so I'll ask him how he did it. Wonder if it does anything for high altitude lag?

Yes, that's the purpose of the boost relief valve or the overboost annihlator, they prevent the PCM from sensing an overboost condition and defueling the engine. Depending on your PCM code, that can be either 22 psi or 24 psi of boost. Now I've run a relief valve before, and didn't like it. Some of those can start bleeding out at lower boost pressures, which would make the MAP read lower than your actual gauge pressure. With the overboost annihlator, my MAP and gauge readings are consistent all the way up to just under 23.7 psi. At that point the overboost annihlator regulates the pressure to the MAP so I don't throw a code and start to defuel. I also bought that from Jody back when I first purchased the chip from him. ITP also carries the same thing. Definately something to look into instead of using the relief valve.