Fat 911 T4 Cooling .. datalogger results

[Wally]

Yeah, I also believe a stock (= low) compression ratio will definately help to keep head temps down.
Somehow, I think that the high fan set-up of the FAT shroud might help to get the cooling air easier to the 2 and 4 cylinder; the air doesn't need to make a sharp turn, like with the deeper sitting fan assembly's.
I'am curieus what your take is on this Jake?

Thanks,
Walter

BTW, 275 F up a hill in a high CR 2270 is amazingly low!
BTW II, my stock 1,8 with stock cooling runs 325 F on the right bank and 375 F on the left bank all year...

[Sandeep]

I'm using the pulley that came in the FAT kit, along with the pulley that comes with the 11 blade fan. How do I measure what the pulley diameters are ? I mean .. do I measure the diameter of the surface that the belt actually contacts on both pulleys ? I'm thinking so but just need clarification.

The AAT is also about 10deg C so this might explain the cool temps, just wait till we hit 35C with humidity in the summer Its getting cooler here by the day so the temps might seem fine ... just wish it was still summer ... I got my datalogger project completed about 6 months too soon

I'm using a stock 72 trans right now but am converting to a 914/01 5 speed this winter so the engine/trans combo will be stock for a 914.

I don't have any (big) hills nearby that I can drive hard up, and when I drive hard on the local roads, I reach the speed limit quite quickly.

Sandeep

[Wally]

Hi Sandeep,
AFAIK, the pulley diameter is measured on the outside edge, so just the biggest diameter of the wheel.
Mine is 145mm.

In my limited experience since the cyl. head temp measurement device is on, outside temps have hardly any effect on cyl. head temps.
Outside temp (environmental temp) does make a dramatic difference on oil temps, but not to head temps.
Can't logically explain it, but thats it.

Regards,
Walter

[zen]

Originally Posted by Wally

Yeah, I also believe a stock (= low) compression ratio will definately help to keep head temps down. .......BTW, 275 F up a hill in a high CR 2270 is amazingly low!

yep. as info, my engine is a 2316cc with 9.7:1. that "up hill" was literally about 1 mile or so at 20% grade or so (guestimates here) at around 80-90MPH and high RPM (i'm geared for acceleration). my oil temp gauge was not hooked up though to know what oil temps looked like. based on load hits head temps and RPM hits oil temps, i was VERY pleased with the head temps.

really looking forward to your info Sandeep. especially on head temps on a relatively stock engine with the FAT shroud. although not a favorite for cramming in a bug, it is the easiest (really only) retro fit 911 system out there and probably the most affordable. great way for low budget projects that just have to have the 911 system to get a running stock TIV in their bug.

[Sandeep]

Thanks for the info Wally, I'll take the measurement this weekend. Just got word that my Hall Effect sensors arrived , should have the RWS and RPM circuits running on the weekend.

Hopefully I'll have everything ready for the next BoxerAutoGruppe meeting, and I'll take the long way there to get about 50 mins of data. This is a nice trip, about 140kph for about 20 mins on the highway and then some in town driving.

I built this logger for my track days in 2005 so I'll post any data I accumulate before the car hits storage for the winter.

Sandeep

[Bill K.]

Kuhl project. How are you going to aquire oil temp data?

[Sandeep]

I will get the oil temp data by taking the vdo oil temp sender (thermister) in the sump location and remove the thermister and modify it for a thermocouple (thermowell).

I can drive the oil temp gauge with a D/A converter as well as the CHT gauge by modifying my program to feed the signal from the highest cht of the 4 to the cht gauge so it will always read the highest temp from the 4 cht thermocouples.

I'm not worried at all about oil temp right now because my cooler/ducting system never goes over 200F while driving at extended rpms for a long amount of time.

Sandeep

[Bill K.]

I'm interested in datalogging too, so your experience is very helpful.

Why are you converting the thermistor to a thermocouple? Are you using thermocouples for ambient and fan inlet temps too? Why?

The auto max-reading gauge is very kuhl. Will you know what cylinder is being read while driving?

[Sandeep]

I'm converting to a thermocouple for oil temp because the IC's I use to read the TC's have an error of 0.5 F and their output is linear. No need to calculate or extrapolate the temp from graphs that are provided for a particular thermistor, whose output in not linear with temp.

For AAT and FIT, I'm also using IC's with a linear output but the IC tells the temp accurate to 0.5 F, no TC's here and the IC is the size of a pencil eraser ... very small. FIT and AAT won't get above 50 C and the IC's are very accurate in this range.

The auto-max gauge concept is for me to tell if the heads are too hot when I am racing ... I can always tell which cylinder was too hot when I look at the graphs after the run.

I could have used an LCD on the dash to give me the required information, but I like the look of the gauges ... and I don't want my dash to look high-tech ... I want it to look like VW could have built it in '74

Sandeep

[Sandeep]

New columns added for run 2, check it out here. Its true that during the warm up stage the temps are uneven .. but later in the run they seem to stabilize. I'm using stock T4 under cylinder tins and a BAS 21152 header with dynomax super turbo 2 1/4" muffler.

I've got the rpm and rws sensors hooked up and hope to do some hard runs this weekend. There is some snow on the ground now but it is supposed to be gone for the weekend.

Sandeep

[Wally]

Originally Posted by Sandeep

Its true that during the warm up stage the temps are uneven ..
Sandeep

and that may even be an engine/tuning issue...who knows?

Thanks for the update and good luck on the run. Keep the car (and youself) in one piece!

Walter