Leak down test is always a good idea on a tracked 911.

Just on really humid days, Thomas. I ran it down at Streets of Willow back in May, on an unseasonably hot day even for there, and it stayed in the 220-ish range. Maybe there is something to this "but it's a dry heat..." quip. So, temps were similar to those experienced last Wednesday up here, but nowhere near the humidity, and oil temps were not an issue.

I'm running the Electromotive crank fired ignition, set at 28 degrees total advance. The motor is running 11:1 compression, so I backed the timing off and twin plugged it in an effort to control detonation on pump gas.

It would be interesting to be able to compare air flow over the cylinder heads on our cars vs air cooled bikes. I agree, the correlation to oil temp may not even be close between these two markedly different platforms.

Yup. The engine compartment tin fits very well and is quite well sealed. I've now tested both the engine and oil filter console thermostats in boiling water, and both open fully.

I run the early, larger diameter 11 blade fan rather than the smaller SC fan that would normally be found on a 3.0 liter. Is there a way to alter the pulley ratio to increase fan rpm's?

http://forums.pelicanparts.com/uploa...1662241002.jpg

I'll go ahead and run this test and see what I get.

I actually do run a leak down test every winter. I've not seen anything to raise concern over the years. And, well, this is anything but a new problem, it began the day I installed the motor. I've kind of outlined my attempts to address it above. Granted, it only rears its ugly head on hot, humid days on a race track. Otherwise it appears there is nothing I can do to make it heat up.

I dunno, maybe as a cooler weather Pacific North Westerner, I'm letting that rare day when it will reach 250 concern me more than it should. What oil temps do you guys who live in much warmer, more humid climates see as far a on-track oil temps? Am I creating "much ado about nothing"?

I havve seen this issue on a couple of cars. As noted, I have had both a bad sender and a bad gauge (on the same car at the same time). I replaced the sender and it was about 10 degrees closer to correct. A new gauge gave me another 20 or so degree improvement (and fixed the issue). Old cars, old parts. Heat/time is the enemy of electronics.

If you indeed have the 150C sender as noted, you can swap in any of the 911 (120-300 degree) 70s gauges to test...or just the temp module out of one. If you were local, I could provide a sender or gauge out of to try.

Strangely enough, a dirty connection on the sender and/or the connection on the gauge will also affect the accuracy. If you have not cleaned both, it is not a bad idea

Personally, I would not be shocked to see 250 on a really hot day...pushing a car hard...as long as that was as high as it got.

Nice looking car/engine.

Jeff,

Another thought about your oil - - - do you ever send a sample to be tested after one of
your 250F track days in the SoCal heat? We try to send in a sample about twice a year
just to check on the oil quality situation.

Regards,
Roy T

Remove gauge. Remove sender. Put together a test rig to check 212° F with a pot of boiling water (or your significant other's Breville steamer). Apart from sending the gauge + sender to Palo Alto Speedometer, North Hollywood Speedometer, etc. and having them confirm the calibration, it's the only way to know for sure on YOUR gauge / sender combo.

http://forums.pelicanparts.com/uploa...1643799025.jpg

Alan Caldwell had an Upfixin' Der Porsche write-up on the procedure for a 914. It's pretty easy to do, especially if you have a 12VDC bench power source.

Check post #8 in this thread. It details the procedure...

http://forums.pelicanparts.com/porsche-914-914-6-technical-forum/206128-center-console-temp-gauge.html

Nice looking engine. The factory had a good reason to place an oil cooler in the front spoiler on their 2.7 and up race engines. It has way more airflow than anything that you can achieve in the fender wells. It would save some weight too over 2 fender radiators.
The holes also produce some turbulence that is not helping.

O.k., per Rick's (and now Frank's as well) recommendations, I did the hot water test on my thermostat/gauge combination. I simply made a "test lead", an extension so I could have the temp sender plugged in while sitting in a pot of water on my Coleman stove behind the car. I put the ol' meat thermometer in the water along with the temp sender, fired up the Coleman stove, and let 'er rip.

The good news is that the gauge in the dash tracked remarkably well with the meat thermometer. The "bad news" then, of course, is that yes - it really is hitting 250 degrees on our rare hot and humid days. This is just about as rock solid of an affirmation of that that I think I can muster.

So, with that settled, where do I go from here? Obvious first steps will be to seal off and block in the driver's side cooler as thoroughly as I have the passenger side. That will be a relatively fun, easy little project for a rainy day (no shortage of those coming up here in the Pacific North "Wet"...).

Additionally, it would be pretty easy to throw my headlight ring and screen back into my track box and start using it again. I'll even go so far as to make one for the driver's side, and cut that bucket out as well.

Lastly, I guess I could add some symmetry by adding holes to the bumper on the driver's side as well. I've always intended to fill them ("some day"...) on the passenger side, but I have waffled between liking the look and being too lazy to do it.

So, I have things I can do that should help. I'll start with sealing the driver's side in. Beyond that, it sounds like many of you really don't think 250 degrees is all that big of a deal anyway, and I think I tend to agree. Especially as infrequently as the weather factors stack up in that direction up here.

So, yeah, thanks for all of the input and suggestions. This has been a great little "sanity check" for me on a couple of different levels. I've got a couple of simple things to try but, alas, it will be next summer before I can gauge their affect. Thanks again, guys.

Yikes! That is pretty surprising that you would run at 250 on a 90F day with double the cooler than most folks have (who run at a lower temp). One would think either your thermostat was not opening or you had a gauge error (but you seem to have eliminated both). I know your engine looks clean enough to eat on, but have you blocked your air in your deck lid or could air flow from the fan be hindered (mouse's nest, fins missing/not installed correctly etc.?

Fint - I think you may have hit on something. My engine grille... I have been running a custom X-Factory grille for a few years now. I think it looks great, and really sets off the back of the car, but... maybe it's the culprit here? Maybe it's not as "cool" as I think?

I know lots of folks running these but, come to think of it, no one else that I personally know with one runs it on the track. Al is a great guy, and does fabulous work, but I'm relatively sure he does not have the means to "flow test" one of these. While certainly never a problem on the street, and quite possibly not the problem on the track, I think it at least bears looking into. I still have the stock grill. I think I'll try swapping them out at the next really hot track day.

I'll still finish up blocking in the driver's side cooler, since that has to be done anyway.

http://forums.pelicanparts.com/uploa...1662338422.jpg

Given the sealing the tins and the deck rubber are supposed to provide, anything restricting the 1300+ liters/sec the fan is supposed to flow would be a problem for your cylinder temps and proportionally your oil temps. I would check the flow rate of that deck grille. It does look nice, but does it flow?

Decklid grille is absolutely the first place to start.

+1... that does look a bit restrictive.

Nice off-label use for the Coleman stove! #ingenuity

Bummer about confirming your high oil temps, especially on a car with finned oil lines and dual fender coolers! Seems like, short of a properly vented center mount cooler, you're rocking belt and suspenders.

On the one hand, your decklid grille seems like Occam's Razor / the most obvious smoking gun. Then again... finned lines and dual coolers!

+2
Like sucking porridge through a straw.

holy ****e!!!!!
 

jeff,
When I 1st started making these grilles, people were worried that too much water would get in ...I.E.....a possible problem with too many frikken holes. I didn't do any flow testing, but I did calculate the open area of the stock grille (mine) and the perf grille.......

The perf grille has slightly more open area than the stock grille that was mounted on my 73 at the time.

here was the original question, posted by Haycait911 (you might know Don) and my answer.....back in 2011

Quote:
Originally Posted by haycait911 View Post
looks very cool Al. one thought, how much area is open compared to the original grill? in doing some math a while back I came up with a number of around 150 liters/sec that a 3.0 draws at 6000 rpm.
Don,
How are you? I did think of this. The plastic grille that was on my 911 has a diamond shape grille, under the plastic. but it is restricted somewhat by the ribs in the plastic grille. I calculated that the plastic grille has approximately 88.15 in sq. of open/intake area, while the perf grille has slightly more at approximately 90.35 in sq.
So it's about a wash.


Let me know what your testing shows......



regards,
al

I don’t think it’s a flow through issue with the grillle.

Tested the engine T-stat? My first 911 had one that would only open partially.

Ok, assuming as stated, mostly in the original post, that thermostats are nominally operational, and guage and sender are sympatico and accurate, and temperature generation is similar to equally similar engines, and there is no flow restriction at the deck grille, there should be two variables left to measure: effective radiator rate to energy (heat) generated, that is, is the radiator area sufficient to dissapate the heat generated; and is the Oil to Air exchange delta being restricted at the point of exchange? Two possible issues at the latter: no/too little air flow to move the heat away from the radiator, or not enough time in the radiator to cool the fluid. I think we can dispense with the radiator area being insufficient given the stated setup, so the next exercise is to identify how fast your oil flow is (presumably stock and no different than the rest of us), and whether or not air is passing through the radiators (just because they are open to air at the front doesn't mean there isn't an equal mass of air behind preventing flow; it's speculative I know, but should be ruled out.).

I found this to be an interesting video on radiator physics: https://m.youtube.com/watch?v=34Ylxf_6ZGw

Do you have the louvered grills behind the coolers? These use the low pressure area from the tires to help the flow.

On a 95° day I can get my 3.0 SC to 250° if I flog it hard for minutes at a time. Once I settle back down it'll drop to 210° or so. Hard to get the oil above 200° if the outside temp is less than 80°.

So I'm saying that 250° while tracking it on a hot summer day isn't a sign of something bad.
What weight oil again? If pressure is holding good, could go to a thinner oil which will run cooler.

It's the airflow through your front oil coolers and most likely the only way you're going to get it under control on hi temp and humid days is to increase the flow or a center mounted cooler.

I have a 72 with a 3.6 that I tracked for several years. It has a center cooler that is not ideally mounted as it sits close to the front panel so it will fit under an RS style front bumper. It vents under the car. I also have a factory passenger side cooler enclosed to push air through the cooler. Driven normal, even on 90 degree days, temps don't exceed 180. However, I would see temps approaching 250 on several outings during 30 minute races. I tried alot of different tricks; bigger lines, drilled out headlight bucket, but nothing really helped. The concensus was more air flow. Others cars with similar combos but with center mounted coolers that vent over the front hood, thus flowing more air through the cooler, were not experiencing elevated temps during tract sessions.

Just my thoughts.

Tinker