danxt3

My crate ls3/480 has some awfully high MAF readings at idle, it is 16-17g/s or 2.20 to 2.33 lbs/min at idle. (naturally aspirated) That is about double what it should be.
I have the old LS2 style (GM oem part) circular MAF, tried cleaning it no change, replaced it no change. It is located ok, about 8 inches downslope from the bend at the throttle body. Wondering why this reads so high? I checked the pin wiring grounds/5v/12 v etc. As a result i am showing much more air incoming that actually is, thus more fuel is dumped than actually needed, then the o2 sensors read rich and drastically cut fuel. Yes i can redo the MAF tables to correct, but it seems like i have a fundamental problem. Is it likely that the scaling of this MAF itself is so different to the LS3 blade style? (I did try a temp setup with a ls3 blade style and the engine would not even run...wiring mismatches with the pinout differences? I did change some to match what i found for pinout diagrams on line...but it didn't work).

turbolx

YES, the scaling of the two sensors is different. Even the diameter of the pipe that the LS3 sensor is install into will change this (if you were using the LS3 sensor). Your easiest option is to either copy the LS2 MAF curve from another LS2 file (ASSuming that you have a completely stock LS2 airbox in front of the MAF), or just take 20 minutes and build the new correct MAF for whatever you have.

Also, double-check your IAT reading after it has been off overnight. At key-on (engine off), it should read the same temperature as the ECT. The LS2 and LS3 have different integrated IAT sensors in them as well, so if you also just have the LS2 IAT sensor feeding your LS3 ECU, that is probably wrong too. This will mess up lots of other stuff as well. You'll have to copy the LS2 IAT curve over as well, which may or may not be easy.

Personally, I would prefer to run the LS3 MAF/IAT whenever possible. It is better in every way than the LS2 element.

danxt3

Thanks, I have a really weird setup, this actually has a LS2 tune a 2006 caddy cts_v tune from the operating system shown. This is an e67 gen 4 contoller. So i have a really weird duck here, it was built this way in 2010/11. So the MAF table is a LS2 table, (i compared it to ls3 tables and it is 20/30 percent lower in values as expected. So if anything i Should be reporting less air according to the fuel trims/ls2 table. It is a custom intake tube, this is all fitted in a 55 chevy. Just trying to get it to run without surges from 1000-3000 rpm. I will check the iat temp with my ait (ambient air temp) when cold. Actually i noticed the ait seemed much lower than it should be. So ya, i have a gen4ls3 with a ls2 tune. This was an early crate ls3/480 (2010) and in the parts list that came with it it specs a LS2 (silver blade) throttle body by part number...so it looks like some early gen 4 ls3's did come with the silver throttle body, at least mine did.
I may be better of having this reflashed with a stock ls3 tune, but thought i would play with this first. Idles runs well except for surge while driving a steady state, i know there are a lot of posts about that, but i need to get my fuel trims settled down first.

danxt3

followup to turbolx
Checked ECT with IAT they match. MAP pressure consistent with Baro pressure.