Indy Project Sled - Installing EGTs

Nov. 01, 2005 By ORC STAFF
Cost: $160 (US)
Risks: Minor
Benefits: Precise knowledge of how well you are jetted, a safety edge
Tools Required: Drill, sockets/wrenches, screwdriver
Parts Required: EGT Gauge, probes, mount pod
Mechanical Skill Required: Average "shade-tree" mechanical skills

EGTs on a stock Indy 500? Hmmmm, I can hear a few of you, OK, a lot of you asking "why?" Because they were there?

Yeah, pretty much. Actually, I was pretty sure I was going to do something to the motor (more on this topic soon) and I knew I'd want EGTs sooner or later. So when I had a chance to get a set of them cheap, I jumped on them.

I could have let them sit in the box until I needed them, but I decided to put them on so I could get used to reading them. I do keep my jetting pretty lean, so it would be a good opportunity to learn about how EGTs report on temps.

I got the type of mounting pod that bolts onto the side of the instrument pod. They are a little tricky to put on, it's hard to know just where to drill the holes - you need three holes for mounting screws and one for the probe cables to go through. It's easier to install if you remove the instruments from the pod. I made a carboard template to mark the holes on the pod.

Once the gauge is mounted, you need to route the probe cables down the hood and to the engine compartment. They're pretty bulky and might not fit in the stock wire guides. I used a few wire ties to secure mine.

Mounting the probes is the most critical piece of the installation. Where they are mounted depends on what engine and what pipes you are running. For a single pipe, you can mount the twin probes in the y-pipe about 2 inches from the cylinder. Temperatures will register about 100 degrees cooler here, so you'll have to remember to compensate for that, but the advantage is that you can monitor both cylinders separately. You get more accurate readings on a single pipe with a single probe located 6 to 8 inches away from the cylinder mounted on either side of the ball joint where the y-pipe and exhaust meet, but you cannot tell which cylinder is lean that way.

Once you've decided where to mount the probes, installing them is as easy as drilling two small holes, inserting the probes and tightening down the hose clamps to hold them in place. Be careful to drill the holes in a spot where you can get to the hose clamps to tighten them.

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