Cylinder Head Temps, My Experience + lessons learned Options

[rwilner]

I drove down to Chris Foley's shop to get his shift linkage installed this weekend. At the charlton plaza on I-90, I stopped to fill up. I usually put premium in the 914 but this time put regular in because it's what I put in my other cars and I was on autopilot. Oh well, I thought...let's see how she runs on 87, maybe I'm wasting my $$ on the good stuff.

Before the fillup, I was running between 300 and 325 F in 5th gear around 70-75 mph.

After the fillup, I was running between 380 and 400! (IMG:style_emoticons/default/ohmy.gif)

I spent the rest of the trip in 4th gear at no less than 3500 rpm to try and keep the head temps down. When I got to Chris' shop, we put the car in the air and drained out 5 gallons. I replaced them with 93 octane before getting on the highway for the ride home. My cyl head temps were back down to 310-350 for the return trip.

Here's what I learned:

• A cylinder head temp sensor and gauge are critical to know what's happening in your engine and should be on everyone's short list. Without it I would never have known of the dangerous operating conditions for the engine. The aircraft spruce gauge/probe are short $$ and a quick install.
• The state of tune has a major impact on running temps (duh). I am still tuning my car with the microsquirt and it's clear I have work to do.
• Higher octane gas makes your car run cooler.

As always YMMV but thought I'd share my experience.
Rich

[jsayre914]

I am learning sooo much from this thread. I have decided one more guage cant hurt (IMG:style_emoticons/default/rolleyes.gif)

While looking at all the 4 channel guages, i found that I really like the idea of seeing all four at the same time and the

MGL AVIONICS TC-2 THERMOCOUPLE TEMPERATURE DISPLAY Guage

seems to be the perfect one, you dont have to view it as a bar graph, if I am understanding the manual, you can read all four as a digital display at the exact same time in real time. look at the last pic of the guage. That is just cool (IMG:style_emoticons/default/beerchug.gif)

[falconfp2001]

I am learning sooo much from this thread. I have decided one more guage cant hurt (IMG:style_emoticons/default/rolleyes.gif)

While looking at all the 4 channel guages, i found that I really like the idea of seeing all four at the same time and the

MGL AVIONICS TC-2 THERMOCOUPLE TEMPERATURE DISPLAY Guage

seems to be the perfect one, you dont have to view it as a bar graph, if I am understanding the manual, you can read all four as a digital display at the exact same time in real time. look at the last pic of the guage. That is just cool (IMG:style_emoticons/default/beerchug.gif)

(IMG:style_emoticons/default/agree.gif) Very Nice. Besides being able to monitor CHT on all for cylinders, does MS have the ability to tune to four CHT inputs?

Maybe MS 3?

[rwilner]

(IMG:style_emoticons/default/agree.gif) Very Nice. Besides being able to monitor CHT on all for cylinders, does MS have the ability to tune to four CHT inputs?

Maybe MS 3?

Out of the box, Micro/Megasquirt, like most EFI systems, performs the fuel injection calculation based on a single engine temperature input. For water cooled engines, it's coolant temp; for air cooled engines, it's cyl head temp. There may be other temp sensors, like an air temp sensor, that go into the injection calculation as well...but there is only one *engine* temp input.

It doesn't matter where (within reason) you're measuring engine temp for this calculation as long as you tune the fuel map to the location at which you're measuring. However, for *monitoring the health* of the engine, you need to measure at the hottest spots...under the spark plug.

I suppose if you were running sequential (not wasted) spark, sequential (not batch) injection, and had individual CHT and/or AFR and/or EGT sensors for each cylinder, you could somehow adjust the mixture for each cylinder. No EMS system that I know of supports this out of the box; however, I guarantee you that you could make a system that would do it. Some combination of MS3 and MSExtra components may get you there.

Unless you are planning to run the engine at 99% of its performance envelope for an extended period of time (a purpose-built motor to set a land speed record or something), this level of cost, control, and complication seems excessive. But, it would be wicked fun to try and build it!!

As far as the group buy...I'm in given my recent experience...although the thought of ripping my interior apart AGAIN to run MORE wires makes me sad. (IMG:style_emoticons/default/wink.gif)