Porsche TURBO Engine Cooling Issues

[kenikh]

Well analyzed!

[mamut]

Originally Posted by Speedy Squirrel

Blade curavature design is based on the speed at which the efficiency of the fan is desired to be greatest. Current automotive fans have the S curve design. This is good with electric motors running them at very high speed, where it is desired to have the best efficiency.

For an engine driven fan, (no longer used in new automobiles), you need to produce the target airflow, pressure, and efficiency at a range of speeds, and at a lower speed, which makes such a design less suitable. Also, a Porsche fan is actually a ducted axial fan, in which case I would think the backward curvature is better for efficiency, especially with variable speeds. It seems Porsche also reached that conclusion. Also, noise and efficiency are really the same thing really. Acoustic energy is wasted fan energy.

None of that really matters though. What makes anybody think that more airflow is going to produce more cooling? Think on it a little more.

Then what is the reasoning behind Porsche flat fan? better air distribution?, it seems that those flat fans flow much more air!.

[kenikh]

Originally Posted by mamut

Then what is the reasoning behind Porsche flat fan? better air distribution?, it seems that those flat fans flow much more air!.

It was crank driven by bevel gear, so it produced the same airflow as a stock fan, but being on top spreads the air around much better. PLUS, in moving to long motors in racing like a 8 and 12 cylinders, the front fan was not ideally set up to push air those long distances.

[patkeefe]

I have aviation cylinder head temp gauges on the turbo SC, 14mm ring sensors on the #2 and #5 cylinders. I have to look uo the temps I run when I get home...the car hasn't been driven for a year, so I forgot. They are under 300F, though. I also run water injection, a very slick system. Drops the inlet temperatures quite a bit between incoming air and entry to the mainfolds.

Also, I once melted a VW head when changing valve guides...got it too hot in the oven (back in my USAF machine shop days). There was a bad thermocouple in the oven. I estimated the head was at between 500 and 600F, and when I grabbed it from the oven, fins came off in my (asbestos gloved) hand.

I have a bunch of data posted for posterity somewhere on this board regarding this stuff. I would go out on a limb and speculate that if anyone gets a head that hot, it is the least of your problems.

Also, agree with midlife...you can never get an electric fan to perform like an engine driven fan.
Pat

[jwasbury]

Reviving an old thread here...

I was searching the forums for "CHT" references and found this discussion interesting, so wanted to add some data.

Since my rebuild (back on the road this past April), I've added a CHT sensor and have been monitoring it in realtime (also have datalogging capability). My experience has been that the CHT, like oil temp, is very much influenced by ambient air temps. 150C (300F) seems to be normal in cooler temps (50-70F). When it gets hot (like this past weekend in the Northeast, nearly 100F), I am seeing 170-180C (350-360F).

No matter the ambient temps, I will normally see the CHT rise fairly quickly by 10-15C with hard acceleration on boost, or during a long uphill pull. Going back downhill, or with the throttle closed the CHT drops quickly. During the intense heat yesterday, I briefly maxed at 190C (375F) during a longish uphill pull at a constant 75mph speed in top gear (probably 2800rpm).

I also notice that dropping a gearand increasing the rpms will typically reduce the CHT by 5-10C due to the increased airflow.

A photo of my digital dashboard...this is a windows XP touch screen UMPC running innovate logworks. This shot taken on the way home from Hershey, I-78 eastbound cruising (and just shy of 400 miles on the rebuilt engine):

[jpnovak]

More details on your setup please.

[Les Paul]

Very cool. How much?

[jwasbury]

My setup consists of an innovate LC-1 for wideband afr, an innovate DL-32 datalogger, and a Viliv X70 UMPC.

The innovate components are set for monitoring and logging of the following parameters:
1) AFR

2) CHT - using K-Type thermocouple wire with a ring terminal in place of the washer under a spark plug. I am monitoring cylinder #6.

3) RPM - taken off tach signal wire from electromotive ignition unit

4) MAP - using the DL-32's built in MAP sensor

5) Acceleration/braking G's - using the DL-32's built in accelerometer

The DL-32 is mounted below the passenger seat



I have a permanent gauge installed for purposes of monitoring AFR. I can trigger a log by pressing a button on my aux gauge panel and the DL-32 will record to an SD card. I can plug the SD card into my laptop at home for analysis after the fact.



Using the DL-32's serial output, I can plug into the Viliv X70 UMPC and monitor the system in real-time using the innovate logworks software. I can also datalog directly on the UMPC using logworks, instead of recording on the DL-32 SD card. In Logworks, I can also program triggered logs, where a log will be started upon a specific set of parameters (such as AFR>13 while MAP>100kpa).

Finally, as the UMPC is a fully functional windows based PC, I can do other things with it. I have Electromotive wintec software installed, so I can interface with the ignition system if needed. The Viliv X70 has a built in GPS receiver, and I have installed Garmin Mobile PC software for navigation. Works exactly like any off the shelf garmin navigator, but with a 7" touchscreen. I also have iTunes loaded up on the Viliv X70 and can jack in to the stereo, but I'm not very happy with its audio output quality. I don't care because I almost never turn the stereo on anyhow and prefer to listen to the mechanical music. I've got all the photo documentation of my rebuild on the Vilix, plus PDF scans of the factory service manuals, electromotive manuals, and innovate manuals. The viliv has built in WIFI so I can use it to browse pelican forums whenever I'm near a hotspot