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

[shuie]

Those of you who have spent time on the Pelican tech forums over the years probably know who Grady Clay is. If you don't know him, he is a really sharp retired ex-racer & Ace mechanic who raced a 917, owned a 904, Abarth Carrera, currently owns a 2.8L MFI RSR powered -6, etc., and then ran a shop in the Denver area for many years. Anyway, he has posted there many times about his 'rubbermaid solution' for keeping -6 cylinder head temps down during tracks days in Denver at high altitude with crappy fuel. Grady's rubbermaid solution is basically just a cool water reservoir/bladder, a stock VDO windshield washer pump, and a stock washer nozzle that is fixed in front of the cooling fan. The water gets pumped and sprayed into the fan when a switch is flipped from the passenger compartment.

It all sounds pretty hokey when you read about it for the first time on the interweb, but it really works. Grady knows his stuff and has posted the math about how much heat the cool water vapor that is sprayed through the fan sucks out of the -6 heads and the hp figures to back it up over on Pelican for years.

I have seriously thought of implementing something this on my 914 just because of the ambient temps here in the summer months and crappy fuel. I sent Grady a PM about it on Pelican a couple of months back and didn't get a response. I don't know if this kind of thing is necessary for a big IV, but it seems like it might be worth a shot.

Here is an old thread from Pelican where Grady posted the details.

http://forums.pelicanparts.com/porsche-911...d-solution.html