EFI 8 Stack injector build process

[my427cobra]

Hi all. I continue to make good but slow progress on my EFI 8 stack system.

I am at the point of deciding where to locate the Air Intake Temperature (AIT) sensor, sometimes called the Air Charge Temperature (ACT) sensor .

Various assembly instructions/articles I have read on line show a rather crude method of installing the AIT sensor.

A hole is drilled in the intake velocity stack/trumpet and two threaded bungs are ground down to match the curve of the velocity stack (one bung inside and one bung outside). See pics attached.

The resultant assembly looks kind of crude to me and of course none of the "glamour" pics on any of the EFI 8 stack manufacturer wed sites show the detail installations, only lots of glitz.

Also, there are two versions of AIT sensors. One is a brass straight version which sticks out of the velocity stack quite a bit. And the second is a 90 deg angle black plastic version which is more compact and may not look as obtrusive. Both are GM spec sensors widely used in EFI systems. See pics attached.

I am thinking of locating the black plastic AIT sensor in the throttle body below the velocity stack flange where it may be less obtrusive/visable and will require a smaller hole (and a custom aluminum bracket to hold it in place).

So can any of you give me any tips or show me pics of your EFI 8 stack injection systems with close-ups of the AIT sensor installation.

Thanks for your help.

Cheers
Greg

[Dwight]

I mounted mine between the two front stacks using a homemade stainless bracket that mount with two of the screws that hold the stack in place. With the tip just above the stack. I understand this sensor read air temp in the engine bay. I wish I could post a picture but it to large.

[Dwight]

I did it!

[my427cobra]

Thanks Dwight. Great pic and I like your solution.

Cheers
Greg

[my427cobra]

Dwight's eloquent and simple solution got me thinking about how effective it is.

An 8 stack in the confines of our typically hot Cobra engine compartments , a low hood profile with little clearance and even if you have a hood scoop (whether you believe it scoops air or not), it probably doesn't matter that the AIT sensor is mounted in the velocity stack.

Mounting the sensor close to the velocity stacks in the "airstream" would probably measure the air temp just as effectively as if it was inside the velocity stack.

So I'm going to use Dwight's method of installing/attaching the AIT sensor.

Any other thoughts or placement ideas?

Cheers
Greg

[eschaider]

My engine uses two IAT (Intake Air Temperature) sensors because it is supercharged. One is located in the intake manifold and is called IAT2 and the other is located in the plumbing from the air cleaner to the throttle body and is called IAT1.

IAT1 is used to measure the incoming air charge temperature. IAT2 is used to measure the post intercooler intake charge tmeperature. The IAT2 sensor is used to pull timing if the pressurized intake air charge goes over a fixed temperature that I have arbitrarily set at 125˚F. This is used for detonation suppression in a supercharged application.

IAT1 along with my mass air flow (MAF) sensor is used to calculate the weight of air that the engine is consuming to properly adjust the injector pulse width to provide the correct amount of fuel to meet my commanded A/F ratio in the tune.

The 8-Stack style systems while not impossible to build as a MAF based system is quite challenging to do so with. As a result they are typically built as speed density which is one of three typical fueling strategies that are commonly available.

The speed density fueling model uses ambient air temp settings and manifold pressure (vacuum) measurements to calculate air mass moving into the engine. By using a volumetric efficiency table similar to the AFR table in a MAF based system the tuner can build a V(e) MAP with sufficient accuracy the injection system can properly fuel the engine.

In your build you will be using a Speed Density system. Your IAT1 sensor for ambient air charge temperature can be located anywhere in the incoming air path. I would not attempt to locate it in the intake throttle body not only because of the obstruction it provides to the incoming air charge for that cylinder but also because it will get heat soaked by the engine heated intake manifold and provide a false reading. Did I mention it takes an absolutely gorgeous (and stunningly expensive) intake system and garbages up the appearance department with sensors.

Because all you need is the temp of the incoming air charge you can place that sensor in the air stream closer to the air inlet for the engine, just like the IAT1 sensor in my twin screw blown engine. The only thing you want to be attentive to is keeping the sensor inside and slightly down stream from the air intake point so you are actually measuring the temperature of the incoming air charge and not the temperature of the ambient air (which is going to be close but not the same).

Positioning your IAT1 sensor closer to the air intake point makes placement easier without needing to hack up an air horn. Your installation will look much cleaner — it's already way over the top sexy!


Ed

[my427cobra]

As for mounting the AIT sensor, I think I will use the mounting holes in the throttle body that are used to mount the Throttle Position Sensor.

Each throttle body at the rear of the stacks has the mounting holes for the Throttle position sensor.

So I will use the mounting location on the right rear (passenger side) to mount the Throttle Position Sensor and the mounting location on the left rear (drivers side) to mount a bracket for the Air Intake Temperature Sensor.

I think I'll use the black plastic AIT sensor and mount it so it just peeks above the top of the velocity stack.

Attached is a pic of the sensor and I'll post pics of it installed as soon as I fab a bracket.

Thanks again Dwight.

Cheers
Greg

[my427cobra]

Thanks Ed. great input.

Cheers
Greg

[Topfuelhydro]

You can barely see mine in between the stacks mounted to the body just under the center red stripe if that helps any.

[ERA 626]

here is where I mounted mine

[my427cobra]

Great ideas. I'm kinda liking Topfuelhydro's idea of a firewall mount.

Thanks guys.

Cheers.

[glenview289]

I mounted mine on the firewall behind the passenger side stacks and at the height even with the top of the stacks. The thought was to get it away from the engine heat but in the same general area as the air entering the stack.
Bill

[my427cobra]

Thanks to all.

As always a wealth of information and good guidance on this forum.

Cheers
Greg

[Bruebaker]

If you don’t mind, please post a picture of your final placement for the air temp sensor and thanks for asking the question. All the answers were great. I am just now where you were then. Thanks!