When wiring the IAT for the EBl, is the other wire a ground or do I have to tap into a 5v ref line??

Yes, it is to ground. This ground is typically shared with the CTS and TPS. The MAP ground is by itself.

RBob.

Are the air temp provisions in the EBL calibration referenced to intake air or manifold air, or are there tables for both selectable by a flag depending on application? Just curious.

Thanx Rbob, I made the tables 100% for now, but I am going to hook up the IAt and I think it'll run better.

There is a single 2D table that is referenced by airfow. The values in the table define a blend of CTS and IAT/MAT. The table value is a percent of CTS to use, the remainder being the IAT/MAT value. The blended temperature value is used for various fueling functions. This set up can be used with either an IAT or a MAT sensor.

On one vehicle that is fed nothing but cold air I placed a bird cage style IAT behind the front grill. When mounted in the air cleaner it picked up heat from the engine. When mounted in the plenum the vehicle was undriveable.

The vehicle with the stock style aircleaner I placed a bird cage IAT in the air cleaner. This engine also has the stock GM water jacketed TBI intake.

Another person using the EBL placed a solid style MAT sensor (such as used on TPI's) in the plenum. He is happy with that setup. He is also running a stock style aircleaner with pre-heat (as far as I still know).

RBob.

I have the GMPP 4bbl vortec intake, no water crossover, open element with the hyperjunk powercharger, and a 4.5 cowl hood. I think I may mount it in the scoop. And try that. I just have to go get a sensor. So I pretty much can pick the style I want cause all the gm's have the parameters?

The bird cage style sensor has a faster response time then the solid style sensor. Otherwise the temperature parameter is the same, they are interchangeable. Not sure if the connectors are the same.

For a bird cage style specify a '90-'92 Camaro w/a 3.1L engine.
For a solid style specify a '90-'92 Camaro w/a 305 or 350 TPI engine.

RBob.

I have moved the IAT to the air cleaner, but still am using the solid style one. I still have the stock style air cleaner with preheat.

I am however controlling the heat off the EBL. I switched the EGR wiring over to the PE output, inverted the PE output, then hooked the vacuum lines to the solenoid for the heat.

Non PE=Heated air
PE=Cold air

Works great, lets me run leaner mixtures than otherwise possible, and cleans up the HC emissions.

Ah! O.K., so you covered all the temp related fueling in one fell swoop. Cool. Thanks.

That's what I had been thinking about. Electrical control on the heat door. Until now I did not have a way of doing that.

Mine ran better this winter with it hooked up.

Now we have options

I may pic up a MAT, like stated, I know my manifold is super cold all the time, and the TB has condensation while running, Maybe it'll be better to use that temp?? Any suggestions?? I may just go the the junkyard and get a few different sensors and try them all out, that would probobly be the best route.

what would be the best option for me? i have an open 14x5" open element. i still have the stock deal laying around, but would prefer to keep my open element.

RBob,

My Xfire Vette has air channels under the hood leading to openings for the air cleaner assembly. I'm thinking of putting the IAT screwed into the side of one of those passages. Also thinking of the cold air box ahead of the radiator.
Any thoughts?

If the open element is drawing under hood air then it would be best to put the IAT in the air cleaner. If the open element is sealed to a cowl hood then placing the IAT behind the front grill works.

RBob.

I would place the IAT where is represents the actual incoming air. I say this as IIRC that setup has a cold air flap? If the air is always being drawn from the cold air box up front, then that would be a good place for the sensor.

If you could temporarily mount the sensor in various locations, the data log will also show how much heat is being picked up from the engine. Even behind the front grill the sensor will pick up radiator heat when at a stand still. Not much but a little. I've always felt this wasn't an issue as the manifold is going to do the same thing.

However, in the air cleaner the sensor picked up a bunch of engine heat. This didn't work out too well.

RBob.

Bob,

The cold air flap is something that was on the 82 Xfire. The 84s have channels leading to 2 opposing inlets on either side of the air cleaner assembly. The channels have an inlet in the front air box. One of the mods for the Xfire is to drill some holes in the top of the air box and then seal the air box to the air channel inlet so that engine heated air doesn't enter the channels. At top end, there's hopefully a bit of a ram air effect.

Ahh, OK, so it sounds like placing the IAT in the cold air box would be the best method. Keeps it away from engine heat, along with straight forward wiring (no wires from engine to hood).

RBob.

Im sure you probably know, but this was also used in the later PCMs for when CPI was in use.

One thing I wonder is whether or not a MAP or vacuum based multiplier would also be of use in addition to a flow based multiplier? It seems that at high vacuum, the fuel basically turns into refrigerant and keeps the TBI and plenum quite cool. It also seems that having MAT/CTS based correction terms would also be useful. In the earlier ECMs it seems that GM sort of fudges the fueling while in the later stuff they just pretend those effects dont exist and use actual air density based on coolant temp. Thinking about it, it probably doesnt since they used a stove pipe on the stock air cleaners so they could modulate the temperature of the air going to the motor.

And also the 4 cyl PFI applications. That is the reason I asked the question in the first place, to see if the EBL code was indeed similar to the later PCM code. I still haven't figured a good reason why an IAT/MAT sensor was not utilized on such a powerful PCM in the V6/V8 TBI trucks. GM never ceases to amaze me. In this case they are penny wise and dollar stupid. JMHO

I think part of the reason is that there are fuel dynamics to consider since its a wetflow system. The fuel in the manifold alters the temperature/density of the intake charge that isnt really reflected in the IAT or CTS alone. GM seemed to handle it with the thermac crap in the air cleaner so that there was always a somewhat constant air temp when the engine was fully warmed.

With a CAI, I had envisioned a 5x5x5 matrix for idle/part throttle fuel corrections to compensate for the dynamics involved. It would be based on MAP, IAT, and CTS, and would apply a multiplier to either the air density term, or the BPW based on what those parameters where.

Well, I went to the junkyard and picked up three different styles of IAT sensors from various GM cars. I hooked one up right at the entrance to my cowl hood. It seems to run alot better. When I am idling, the IAT goes up as the engine heats up the incoming air. When driving down the highway, the IAT reflects the ambiant air entering the cowl scoop, which is RIGHT at the aircleaner. It made a noticable differnce in performance. I hooked up the ford taurus electric fans. I used 4 relays to make a Hi/Low fan conroller. Work rather well. No I just have to change some settings in the bin for the fans. I love the EBL!!

I want to hook an IAT up to mine, and was wondering if anybody knows the terminal p/n so I can plug it into the empty C12 slot on the connector to the EBL. Any recommendations?
THanks

All I did was go to the local u-pull-it and get 3 different styles of IAT, and the corresponding plug with a long lead of wire still on it. All the IAT's I picked up had the same plug. The cheap way out.