i was just looking at someone tune and IAT tables... then thought to myself, where in the world is my IAT? i was told it should be in the intake, snorkel, or intake manifold...

however i NEVER seen that on my engine, even before the rebuild... the element has no holes at the bottom for a IAT, the snorkel box didn't either... and my intake manifold has 1 sensor near the thermostat, and im positive thats the coolant temp sensor, cause when i replaced it thats what i asked for, and it was identical to the old sensor...

so now here is the big question... where is the WORLD is a IAT sensor on a L05 block... ??? and how in the world is my engine running?

i have a extra harness in the engine near the back close to the distributor, but it was never hooked up, i was always thinking thats maybe some sort of diagnostic port or something...

help will be appreciated..

 

now im confused, as i dont have a IAT at all, no harness either that i can see that would fit a IAT...

i just looked at things again, and the harness thats to the back is a 4 pin wide harness.... so like i thought, that must be for some sort of diagnostics... its in a big bundle of wires... and its short...

the only other harness that is not hooked up is my EGR solenoid harness.. as i dont use EGR anymore.. and its tuned out...

so basically that leaves everything else hooked up...

the only sensor that look close to the IAT is a sensor I have on the driver side vortec head... i will have to unbolt it to see what the tip looks like, but it is a dual harness connector, but it only has 1 wire going to it.....

on the passenger side bottom of the block is my knock sensor

on the front of the intake manifold near the tstat is my coolant sensor

throttle position sensor & idle air control sensor are on the throttle body itself

purge canister solenoid is hooked up on top the manifold

so really im trying to figure out what is hooked up to my vortec head on the drivers side? can it be the IAT sensor or not? it has 1 wire, but looks like a dual connector...



i need to install a IAT before the re-dyno... i guess ish happens for a reason..

this is the only sensor i have in my intake right now.. Advanced Auto calls it a Coolant Temp Sensor for my truck... $10


when i looked up IAT for my truck, it shows me this, with a different part number... IAT sensor $25


the head of the IAT looks similar to whats screwed into my vortec head on the drivers side, but it only has 1 wire in a dual connector...

anyone know what is that sensor in my head? and is that a normal location for a IAT? i had not remove it yet, so i cant tell what the tip of it looks like, but its new sensor, it appears.

 

What ecm are you running?? I know that the trucks did not come with an IAT sensor until the later years, Vortecs I think. I know that mine does not have one either. I would like to hook one up though but cannot find the thread to do the conversion for the 7747.

 

yea its the 7747 pcm... so i take it some trucks didnt have a IAT.. so then how did they work properly? and what advantages does the IAT offer?

im doing the mod to convert to the IAT... seem simple as ground, and signal wire to pcm pin in.. then having the correct .bin to work everything.. maybe someone with more knowledge chimes in...

 

IF you get it figured out let me know!!! PLEASE!! I have been trying to find a thread on the conversion for a while and no luck with the new search feature. If you have the right bin for it I would think that you will beable to dial in your fuel curve a little better for engine and intake air temps. It would make life alot easier for me and my Air-gap manifold. Otherwise you ve and fuel is strickly based on your ve stettings and therefor can be slightly rich or lean depending on the temp of the intake air etc. This is how I figure it works?? I hope someone else will chime in as well with maybe a sticky or thread on where to look for the conversion and what changes to make in the bin file?? THanks for any help!!

 

yea it controls up to 10% of the fuel tables... i have alot of responses on my other thread, just start reading from this page to the end...

http://www.fullsizechevy.com/forums/...-alive-22.html

 

With TBI, the IAT doesnt matter as much due to the fact that there are fuel dynamics. The true intake air temp is really not known. GM used a heated manifold and thermac to keep the IATs high and constant and the fuel vaporized.

 

hmm. yea, i know we had the heated manifolds, and i do plan on using the heated riser on the BBC throttle body... but i was told that the IAT will effect as much as 10% fuel calculations, and that just seemed to be alot for a heavy brick im driving...

i dont use the thermac, but a open element, which might change to a CAI.. but basically it doesnt matter is what your saying?

thanks for that explanation, thats the 1st side ive heard of that nature...

 

hey diemented, i was told by 91chevZ71 that the new sensors work better... and is it funny how the older TBI has the IAT sensors? but why not my later model TBI? the problem seems to be with the 7427 PCM, that they didnt offer the IAT... except for the CPI 4.3 and L31 export trucks....

so are you basically saying, to just keep without it? or swap it in?

here is some pics of the new IAT sensors..



and here are the new CTS sensors

 

so are you talking specifically about the IAT?? what about a MAT?? as its in the manifold I want to place the sensor.... I heard its alot to be gained.. please let me know what you think..

from what i found out, its better to have a reading in the manifold, anything in front the TBI does no good...

 

you got it

 

During cruise, intake coolant also helps to cool the intake from the presence of EGR. So either from fuel vaporization (a coling process) or from EGR (a heating process), the warm coolant is there to help stabilize the IAT.

 

so you are saying TBI dont need a MAT or IAT?

yea, but you guys are thinking STOCK! i dont have a snorkel, with heat riser from exhaust... i dont have a heated intake manifold with coolant circulating around the TBI.... I dont have a EGR system....

now i guess that answers my question, i need to run a MAT then.. On FSC i was reading how involved the guy said tuning the MAT sensor was... I plan on tunning the MAT sensor in myself, after I hook up the wires and buy the sensor.. but this will be my 1st tuning project.. getting my MAT tuned in..

 

So long as you use a heated manifold (almost a must with TBI), then no, its not absolutly necessary, but it can help at WOT when the intake temps are closer to the temperature of ambient air. But, only EBL and the later PCMs have the capacity to utilize the IAT properly by blending it with the intake temp to provide a better picture of the entering air temps.

 

well the manifold is a cyclone performer, its not heated.. im going to use the heated BBC throttle body riser... im hooking those coolant lines to the intake manifold line outs..

but that will be my only source of heat, and im switching from a 160* to a 180* stat...

so is the MAT sensor more trouble than its worth or what? i talked with oldred95 and he said his tables are zeroed out for now, till he gets other stuff working. and some other guy said its involved in tune it....

91chevZ71 was telling me my gas mileage can be way better with the MAT... which is what i would like.

atleast i know my truck didnt come with 1 now.. i thought i was missing it for a second there... why didnt GM give the trucks with 7427 pcm the MAT?

 

When you stray away from the stock configuration, then your sort of up the creek without a paddle. One thing to keep in mind is that with a performance manifold and CAI, the IATs change CONSTANTLY and its difficult to predict what the actual IAT is due to how much the fuel influences the temps inside the manifold at P/T. Putting the IAT in the manifold can help, but the stock IATs have a looong transient response. If you could find something small, then you could use the IAT.

 

yea, i heard the dry type intake is difficult to tune, so the wet type intake (tbi) is even more difficult to tune... the changes are so inconsitent in the intake, like you said.... with the 1st dyno tune, it idled fine, and always has.. maybe i really dont need 1 still... but i was thinking of the mpg.. i guess ill put the MAT sensor on hold then... cause my mpg is pretty good for a stroker.

 

The MAT will help the computer make the right choice in terms of how much fuel to squirt. Not having a heated manifold and no MAT could be having a negative affect on the mileage. Having a MAT will let you dial in the tune more accurately

what dimented says is totally true. a light shot of AE will drop the temp by about 15 deg F. Hell, just more TPS in general will cool it off.
And my manifold is heated!!!

 

how hard was it for you to dialing your MAT sensor in your tune? do the tables change or are consistent once dialed in? wont i have to dial in for each season as well? that is what make me think its involved...

question about heated manifolds...

isnt the only difference with a stock manifold, is that it heats around the circles where the TBI mounts? if so then with my BBC tb riser, it should perform the same task, but better...

 

well, the code itself is set and doesn't really need to be messed with. What you can mess with is how much split you give the two sensors to control fuel.
e.g. 60% CTS, 40 %MAT. or 80 CTS, 20 MAT.
then the spark advance table also.

The split %'s are determined at g/sec airflow, so the more air flowing the more I give the IAT, since the air is moving faster

THis is with the EBL.


Like around idle, 95 % CTS and 5 MAT. WOT- 65 CTS, 35 MAT. (air is going faster, no time to pick up heat)

 

sounds interesting.. i will take up the task after i finish this dyno, then tweak it from there.. im not sure how or if the 7427 is more involved or not...