I have a 09 LS3 corvette with headers and the stock intake. I've been doing a bit of data logging and I've noticed that the MAP falls off a bit as the rpms climb at WOT. I replaced the air filter and it's better, but still falling. At 2000rpm it's 101, by 3500 it's 100, by 4500 it's 99, and by 5500 it's 98. I'm just wondering what people with aftermarket intakes are getting. Also, while cruising my IAT is about 2*C above what my console says the outside temp is. Do aftermarket intakes do better while moving? Thanks

 

It´s an interesting question! Don´t forget, that the barometric pressure fluctuates outside.
For varification you have to read the difference between Map and Baro-pressure.
My difference at wot is round about 3 kpa (stock Ls3 intake). Without Air-filter it´s the same. So there are no gains for aftermarket intakes for my car.

 

3kPa total pressure drop really isn't bad if you consider it's the total loss of the airbox, filter, zip tube/MAF, accordian, and throttle body.

The actual IAT entering the cylinders will always be slightly warmer. The GM ECU has a background model that skews the IAT measurement (taken at the MAF in front of the throttle body) toward the ECT to account for warming that happens as the air passes the intake manifold and cylinder head ports on the way into the cylinder itself. This effect is greater at low flow rates (cruising, idle). That 2*C shift really isn't costing you any serious power, it's really happening, and the ECU is using it to better estimate how much fuel the engine needs to run clean.

 

I'm still pretty new with Hptuners, I didn't know you could log baro. But I did check MAP with the key on and engine off, it was 101 that day. It looks like HPtuners can log outside temp too, which would be useful. I was just looking at the outside temp on my console and comparing it to IAT like a newb, lol. My thinking was that the data says there's very little to gain with an intake, just wondering if someone with an intake might be actually getting better numbers

 

I tried a ramair, there are no gains when your car runs.
Only when your car slowly rolls through town, or the first moments on the quarter mile IAT is a little bit colder than stock.

 

Good to know, thanks

 

Kpa usually means there is a restriction - I am seeing 5kpa by redline but I'm making 600whp so I am attributing that to the throttlebody size.

 

You guys have very good air I'm @ 1100' so 96-97kpa is the starting point on the dyno. The motor is an N/A LS3 stroker with a long list of stuff that I've run in my C5 & is now installed in my C6. In the C6 the differences are a ported 92mm TB with a Haltech CAI & stock MAF vs the C5 with NW 102 TB, large Haltech intake & a LS3 MAF. The other difference is the C6 has LG 13/4 pros, catted 3" mid & rear 3" GHL exhaust. The C5 had 1 7/8 AR headers catted 3" mid & 3" LG exhaust. The motor internally is identical as are the Frankenstein cyl heads, valve train & a ported Fast 102.

I'm starting to look for a 60rwhp deficit between the 2 cars & the map KPA head always caught my eye, I thought the C6 setup was gaining to much vacuum during a WOT power run. This thread & your question inspired me to compare the two logs.....something I was going to eventually do to confirm my suspicion.

The C6 @ the start of a 96kpa dyno run is 90-91kpa solidly by the 6400rpm so an easy 5-6kpa increase in vacuum......this is a problem. The C5 with a larger TB & matching intake setup barely has a 3kpa difference from the start of the run to the end. So a 2-3kpa looks to be the magic for a good N/A setup, to do list next season.

It was always part of my plan to do a compare of the 2 TB's & air intake setup's. This motor was freshened before installing in the C6, being new to tuning with VVE I wanted to break it in & familiarize with the Gen 4 ECU prior to trying to make a 102 TB run nicely.

 

Depending on who ported it...your throttle body could be to blame.

 

I have used FAST intakes and the WOT KPA will reach 102 !! As mentioned a lower than 100 is most likely just a dip caused by barometric air pressure that happens to be lower in some weather conditions
As far as the intake air temp sensors if you are getting IAT temps just barely over the actual outside temp that is really great
IAT temps can spike to as high as 140* if your car is driven in city traffic for awhile What happens is the IAT sensor gets heat soaked from underhood temperatures and will read very high As you said once you start driving at speed the IAT temps will go down as colder air cools off the sensor
Most tuners will massage the IAT timing deduct tables to reflect this heat soak
I typically will eliminate ALL the IAT timing deducts at WOT up to about 104* and remove about 50% of the deducts up to about 150* and after that leave it be
These IAT timing deducts are massive ! as much as 8-10* These engine typically at WOT run best between 24 and 28* timing But if the deducts are as much as 10--the ECM removes almost 1/2 of the "commanded timing "
Every car is different--If you start hearing detonation then simply add back some of the deducts------- only after data logging what your actual IAT temps are and where you hear the pinging (RPM) wise
PS I also remove ALL the P/T deducts up to 104* as well-- but after 104 I leave the stock P/T deducts alone