Printable Version of Topic

Posted by: Olympic 914 Jul 15 2020, 07:00 AM

So on the Oil Cooler thread the suggestion was made to place a thermometer under the trunk to check the temps to determine possible difference for cooling efficiency.

I don't know if anyone had done this before. So I broke this off into a new thread for future reference.

One of the Oil Cooler threads

http://www.914world.com/bbs2/index.php?showtopic=347075

So yesterday I did this.

Using a Wifi endoscope taped to a magnetic tool holder with a thermometer.

Placed parallel to the Setrab oil cooler to sample the air temp without the fan blowing directly on the thermometer










And went for a drive. My GF rode along to monitor the temps and take notes.

The outside temp was 80 rising to 85 yesterday.

Idling in the driveway the temp rose to 125, after 2 miles of two lane roads 30mph it had dropped to 120.

at 4 miles stop and go it was still 120, Oil temp 200 CHT 340

onto a two lane road for 11 miles with speeds from 30-50 mph air temp was between 118 + 120 deg Oil temp 212 CHT 322

at this point I stopped for 2 minutes to mimic sitting at a long light or in traffic.
the air temp rose to 140 deg Oil temp 210 and CHT 337

Pulled onto 4 lane and accelerated up to 70 mph. After 1/2 mile the air temp had dropped to 125deg oil temp 209 and CHT at 370.

mostly level with some slight grades.

Turned around at 23 miles

Air temp holding at 125 deg Oil temp 213 CHT 330

The battery was low on the endoscope and I had turned it off on the way back, and when I turned it back on I discovered that the duct tape had loosened and I lost my thermometer.

My setup is a 2056 9590 cam Djet. , Oil cooler is Setrab 119 fanpack 180 deg oil thermostat and 190 deg sensor for the fan. Exhaust is SS HEs and a Triad muffler.

When running in normal summer heat the fan runs constantly.

If any one else decides to do this Please add your results here.

Tom

Posted by: 914Toy Jul 15 2020, 08:11 AM

Posted by: 914Toy Jul 15 2020, 08:14 AM

Oops, I posted my reply in the middle of your comments, re "Thanks for your practical and very useful information."

Posted by: dirk2056 Jul 15 2020, 10:26 AM

Well done great work!! I would think its much warmer when you are under the car its HOT!! any idea how hot the muffler gets?

Posted by: BeatNavy Jul 15 2020, 12:49 PM

Great work, Tom! This is very helpful.

So with an ~80 degree temperature gradient between oil and ambient air over the HE's there has to be SOME cooling potential.

Some day I will try to replicate. And I owe you a new meat thermometer for sacrificing one for the cause

Posted by: Rand Jul 15 2020, 01:03 PM

Sometimes an unexpected thread comes along that hits. So simple but gold. Thank you.

But just keep things in good order and drive the hell out of it. Sometimes worrying about heat to THIS level sucks away the fun factor.

Posted by: GregAmy Jul 20 2020, 11:53 AM

This just arrived...$52 delivered. Four probes, Bluetooth to the phone, and logging.

Once the weather stops being hot as Hades I'll run a nice 4-point log of some interesting places in the car.

I'm thinking one in the engine compartment near the D-Jet plenum, one under the trunk near the transaxle, one inside the intake of my air duct to the rear-mounted oil cooler, and one above the exit of the oil cooler.

Then I'll go cook me some steakage...

Posted by: GregAmy Jul 26 2020, 07:54 AM

Ok, this morning wasn't unbearable heat, so here's my novella...

Test process:

- Equipment as in the above post. Probes were placed in four locations:

#1 (green dot in screen shots), intake of my oil cooler duct I built, with the intent of pulling cool air across the cooler.
#2 (blue dot in screen shots), top of cooler fan, air exiting the cooler
#3 (red dot in screen shots), probe stuck backwards from the engine compartment through a wiring grommet in the vertical sheet metal. So it's measuring the air temperature pretty much at the transaxle/engine interface.
#4 (orange dot in screen shots), probe tye-wrapped to the right side fuel line in the engine compartment.

The car: 1974 2L, dead stock long block (AFAIK) but powered by Microsquirt. The oil cooler has been replaced by a Tangering Racing kit which includes a thermostatic block that bolts up where the stock oil cooler was.

The cooler includes a Microsquirt-controlled fan, which comes on at ~220 and shuts off at ~200. Oil tmeperature is measured at the cooler exit line.

Ambient conditions: sunny, 79F. Started roughly 830AM so low sun.


Attached image(s)

Posted by: GregAmy Jul 26 2020, 08:12 AM

Test loop: my home is 5 minutes from I-91 in Middletown CT so I left the house and headed for the highway. Initial direction was southbound, which has a gradual decline to New Haven and Long Island Sound. Very light traffic.

As I started out I noticed something that surprised me: the bottom side of my cooling duct was baking. This duct extends downward between the transaxle and the right exhaust and ends roughly below the bottom of the heat exchanger. And it's close.

Recall that the oil cooler has a physical thermostat, which opens at around 180F. The fan does not come on until 220F. So until the thermostats kick in, these first two probes are roughly measuring actual air temperatures in between the heat exchanger and transaxle, and at the top of oil cooler near the trunk.

And it was baking.

It took a bit for the oil temp to come up to speed, but before the fan kicked on I was seeing nearly 200F at the bottom of that duct with 120F at the trunk:



The front under-trunk area and engine compartment wasn't too bad at that point:



Once the thermostat fully opened and the fan finally kicked on the temperatures inverted. What was surprising was how much higher the forward engine probe got:



Long story short, once I had been in highway cruise for about a half hour, everything pretty much stabilized. Oil temps were around 214F with the fan constantly on.



Here's the graphs for all four. You can distinctly see where the duct was baking until the fan kicked on, and how things stabilized. You can also pick out where I exited the highway and sat a bit at the light before reversing course.
[attachmentid=754
686]


Attached image(s)

Posted by: GregAmy Jul 26 2020, 08:42 AM

Conclusions? Eh, I'm not gonna make any declarations based on such a small data set. I was surprised kow baked that area between the heat exchanger and transaxle is; I expected some level of radiant shielding from the heat exhanger shroud itself, especially since there's air constantly flowing through there.

There seems to be a lot of stagnant air under there, too. If there was strong airflow then the exhaust heat would be carried away better and the forward temp probe would have pretty much stayed as solid.

In the interest of science, I flipped on my interior heat with the fan, to see if any additional airflow would cool the general airflow under there, and dump the hot air into the cabin instead of out the heater valve. Zilch, zippo. Ddid not affect the temps by even one degree.

I was also surprised at the minimal difference in air temps between the cooler inlet and outlet; I expected not only a higher delta but a higher overall exit temperature. 30F delta is not a lot, making me wonder how I can make it more efficient. Plus, it highlights the significant importance of the inlet temperature flow; if I could get the inlet closer to ambient instead of 130F then I'm confident it would affect the oil cooler temperature a whole lot more. This whole exercise shows how effective the front coolers are, and is making me rethink my support of rear-mounted coolers...but front coolers are such a major PITA on a street car...

Oh well! Digest the info, lemme me know what you think. And if you have some other places you'd like to see my try, I'm open to ideas.

BTW, I may try this again later today when it's hot as blazes, just to see how 15F ambient affects it. Depends on whether I hit the beer early or not...

Posted by: BeatNavy Jul 27 2020, 03:00 PM

This is good stuff. Thanks for posting. I just finally got a chance to read and digest.

I'm getting on board with this sentiment, Greg.

Rear mounted coolers can probably do the job under the right conditions, but they'll never approach the heat displacement of front coolers (which are a PITA...or at least require cutting).

Posted by: GregAmy Jul 27 2020, 04:04 PM

I never got motivated to try it out later in the day (beer). And today has been hot as f....udge.

The problem I primarily have with front-mounted coolers is I really, really, really don't like having engine-pressure oil all the way to the front of the car, all the way through a thermostat/cooler system, then all the way back to the engine. There's just too much opportunity for pressure loss and introduction of air into the system.

Dry sump? Sure, no prob, there's a stage to drive the engine oil and its circuit is local, and another stage to drive the oil forward and then into a sump tank. I use a 2-stage CB Performance dry sump on my race car.

I know "it's done" but I don't like it in concept. So I run an aft cooler on the street car. It seems to do the job (I may try a Track Night in America event later this year to see if it's "enough").

Posted by: VaccaRabite Jul 27 2020, 04:25 PM

My rear mounted Setrab double with fans kept the oil temps right around 215 fro the HOT drive to, during, and from the meet last week to the tune of about 400 miles with ambient temps approaching triple digits.

Without the fans running (I did not re-wire the fins in until 90 minutes before we were supposed to leave for the event) oil temps would stick around 225.

Before I put the cooler in, I was seeing oil temps around 240-250.

Rear mounted coolers work just fine on street cars.

Zach

Posted by: Craigers17 Jul 27 2020, 04:54 PM

That's interesting data. Nice Work! One test I'd like to see you try is removing your cooler duct and then replicating the same test run. I wonder if you remove the duct, place the 1st probe as close to the same proximity as it is in the duct, and keep every other variable the same.

....I think that not only would the data from probe 1 be interesting to see, but also how that might or might not affect the #2 probe? Just curious.

Posted by: GregAmy Jul 27 2020, 05:03 PM

"Brilliant minds", and all that. I was thinking the same thing as I was driving homeward yesterday. It would be easy to do, given the bottom part screws right off.

Idea was that pulling air from right next to the heat exchanger didn't do what I expected (pull cool air passing underneath) and maybe have made it worse (pulling ho air from off the heat exchanger).

Maybe later in the week. "Watch this space."

Posted by: dakotaewing Jul 27 2020, 07:18 PM

Just to add more fuel to the fire, I know there are a few members that run their oil coolers inside the rear wheel well in front of the tires.. Anyone got any data for that placement?

Posted by: JmuRiz Jul 27 2020, 08:52 PM

Good info and confusing as always.
I never had issues with my carb-cam 2.0 with a rear cooler.

Plan to try a read cooler with fans and temp hoses. If it works well I’ll do in braided hose. If not, I’ll get out the hole punch and have to pony up $$ for a front setup

Posted by: 914sgofast2 Jul 27 2020, 09:00 PM

Why not put a heat shield on top of the heat exchanger to deflect heat away from the rear mounted oil cooler?

Posted by: DRPHIL914 Jul 28 2020, 10:59 AM

cool research thanks for posting, i amgoing to get one of these and do the same, but no shroud on my oil cooler , fan seems like it doesnt come on until about 220, i have a variable rheostat but thats the soonest so i might change this , but i am interested in seeing exact temps for the various locations of themotor even the heads and the oil .
could you put one each in alongside each head at the spark plugs , compare 1,2,3,4? i know we say #3 alwys hotter and thatswhere my single CHT gauge lead goes, .
got to love technology!!
Phil

Posted by: Olympic 914 Jul 28 2020, 11:38 AM

I used a 190 deg thermo switch inline before the cooler.

On at 190 off at 175 (what ever temp you choose it goes off at 15 deg drop)

https://www.pegasusautoracing.com/group.asp?GroupID=SETRABSWITCH

Posted by: DRPHIL914 Jul 28 2020, 12:04 PM

great, thanks for the tip.

Posted by: porschetub Jul 28 2020, 04:40 PM

Well done Greg,my experience with thermo couplers indicates your reading should be pretty accurate,wow never expected those temps for one minute.
Wonder if anyone has removed the rear valance to see if there is a drop in temp as per the Porsche factory race cars or was that done for another reason .
Cheers for your efforts.

Posted by: GregAmy Jul 28 2020, 06:39 PM

Tonight's tests, removing the duct. Probe is in a hole I drilled on the side of the enclosure that comes with Tangerine's cooler:



Conditions: ambient 84F, sun going down so also low on the horizon like last weekend (but of course on the other side of the car... ). Same route, slight descent toward the Sound, then reverse course for a gradual climb home.

After the thermostat opened, right before the fan kicked on:



After the fan kicked on and all temps were stabilized. Oil temp was at 214F:



All four graphs:



Spike is when I pulled off the highway and worked my way back around to the other direction.

Conclusion? My intake duct was a bust, made the problem worse.

Now I'm wondering what would happen if I cut Tangerine's enclosure down half-height (lot more work to get that out, trim it, get it back in. But not impossible...)

Posted by: Olympic 914 Jul 28 2020, 08:13 PM

Posted by: Craigers17 Jul 29 2020, 01:38 AM

You win some ....you lose some....progress is never made standing still. That said, you've got a rear mount set up that is working properly, and the oil temp is consistently stabilizing at 214. Looks to me like you've already won.... but I'm guessing you're now trying to optimize for track use?

Posted by: BeatNavy Jul 29 2020, 04:52 AM

Greg my duct work was a total bust as well. And I spent a fair amount of time to fab it and was pretty proud of it.

This is great info. From mine and others' experience I draw the following conclusions so far: a) a rear-mounted cooler can help, but it's not likely to get temps below 210, and that's WITH lots of air movement from motion, and b) hot day without moving you're likely to climb to 225+.

That doesn't mean we can't do better.

Posted by: GregAmy Jul 29 2020, 06:25 AM

Pretty much, yes.

My initial foray into this wormhole was because I was seeing 255-260 (needle into the red on the stock gauge) for the last several years while on the highway. That usually became a problem this time of year, July/August, as it was extremely sensitive to ambient temps (never a problem on cool days).

So the first install was over the winter, using the Tangerine ducting you see there but without a fan. Long highway run last Spring saw temps into the red again.

I took the Tangerine duct off, still no fan, and it reduced the temps about 10 degrees, to around 240-245.

I added the fan and reinstalled the Tangerine duct, wired hot to the ignition, and it came down another 10 degrees.

These were all measured via the Mainely dipstick, and correlated to the factory oil temp gauge using the common JPG we've all seen for what the temps are on that gauge.

At this point 225-230 wasn't hateful, but there was nowhere left to go when the ambient temp rose later in the year. So I bought the inline oil temperature sensor and input that into the Microsquirt and then used one of the MS' output to control a relay for the fan.

I reinstalled the Tangerine duct, added my "southern" duct, and config'd the MS to switch on the fan cooler at 215 and off at 190. I found that once the fan came on it would stay on, and the oil temp wouild stay right at 215; that indicated to me that I could control the temp to 215 on the highway but there wasn't enough BTU removal to reduce it (it cooled down below the "off" point when not under load). I did find recently that if I changed the fan set points to 220/200 then the fan would bring the temps down to 214-215. So I think I've reached a stasis there.

So that's about where we are. The current setup is sufficient for street use, but I'm of the theory that there's not a lot of BTU capability left in it. This will not be a high-use track rat; it's a driver street car. But I would like the opportunity to take it to a TNIA event once or twice a year.

There may also be something specific to this engine. I noticed that if I pull over at a rest stop and let it cool to 190F, then blast off for a full-acceleration run dwon the on-ramp to merge onto the highway, I can add 35 degrees to the oil temps within 15 seconds. Maybe that's normal?

I may take it to a TNIA event soon and see for myself if my theory holds. Who knows, it could be that as the gets hotter the cooler will pull a lot more BTUs out. Worst case I run 225-235 on the track and that's fine. As long as it stays well below the red I'm happy.

Greg



Attached image(s)