Engine oil temp. study results correction

Sweeeeet. Thanks, Bruce.

Looks like T-3 dipstick block off is the best spot for a sensor.

Bill......Thats what I think......Bruce

So, the big "ah ha" take away for me is this: laying all the collective worshiping at the shrine of (85 year old) German engineering aside and just looking at what a lot of us see on our gauges (and what Bruce has codified to some extent)-- the super-duper VW stand-mounted oil cooler seems to not be as fabulous as Gene Berg and his disciples over on the Samba keep telling me it is.

 

I'd never base a bunch of big statements on one uncontrolled experiment, but what Bruce has done is pretty nifty bit of data collection. So to hypothesize on the results: it really looks like the lack of delta across the VW oil cooler is probably a function of the cruddy airflow situation in a speedster engine bay, making the remote oil cooler most of us run a pretty important component in the big scheme of things. Enough so that I'd be interested to see how this experiment would go with a non-doghouse 36 hp shroud, taking the bypass pistons out of the circuit, and relying on an external pressure relief (I've got a Jaycee relief) and remote oil cooler only.

Looking at the pics in the other thread, Bruce, I don't see a thermostat for the extra cooler, and it could be playing with the mechanics of the stock cooler's control system. Also, with no sled tins installed, the expelled cooling air from the bottom of the engine is hitting a perpendicular higher pressure zone and isn't being removed efficiently. The purpose of the sled tins is to allow the spent cooling air to make that 90' corner and join the under-car airflow (which I've read can be as much as 2psi higher) behind the engine, so it has no chance at being recirculated. This higher pressure zone under the car isn't much of a factor around town, the stop and go of it along with the lower speeds allows the fan and upper sheetmetal to do it's job, but at freeway speeds I think that high pressure band doesn't allow the fan to push all the air through that it normally could. 

 

I'm not saying I disagree with you, Stan, I just think we don't have all the pertinent info yet.

 

Bruce- What weight oil is in the engine?

Stan....Could you explain your use of delta to me ? Pardon my ignorance. Your idea about eliminating the doghouse cooler and returning to a std 36 fan shroud along with the two relief valves is diabolical! I was actually thinking about the same but hadn't arrived with the concept of the relief valve elimination. That would be a scary project but maybe useful.

Most car radiators now have only one row of flues and more square inches of area compared to those in older cars. They are just more efficient in getting rid of the heat. The doghouse cooler is like an old radiator. 5 rows of flues, thick, very little surface area and not a lot of air flow thru it. I now don't know why I was so surprised to see such little change in temp. between the in and out ports. I really believe what temps I recorded because I just can't any closer to measure them. The sender bulbs are right in the flow just enough so as to not restrict the flow.

Anyway, I was dumbfounded at the results.......Bruce

Hi Al.....I use Brad Penn 30wt. I don't have a thermostat for my external cooler. My thinking at the time was to just let the oil circulate thru the cooler during warm-up. The fan wouldn't be on until 180F so no cooling effect before that. Also here in So Cal it's never really cold anyway. It also meant more plumbing and more places for potential leaks. Thoughtlessness and laziness dictated that decision pretty much. Since then I have changed my mind so the next two things I will install will be the sled tin and a thermal oil bypass. I'm going to leave all the temp senders in and do another road test to see if there is any changes , improvements or what ever. 

 

I really like the way I currently have that cooler, fan, and oil filter plumbed in. It's tidy and has easy access for inspection and repairs. Far superior to where I had previously mounted it up in the firewall void.

 

By the way.....I had Rhonda up to 105 mph yesterday on the fwy. My first time at that speed. Drove about 5 miles. T-3 dip stick sender hit 203F. CHT hit 340F. Ambient air temp was 88F. I didn't log any other temps because it takes another person to flip the switch and write down to temps. At 105mph it wouldn't take much to get out of control. I had just adjusted the tire pressures. 22 psi and 25 psi rear. It handled pretty well, no wander, no nothing. I have 6 degree neg. caster and the rear is higher than the front enough that I have not bottomed out yet on any driveways. California look on a Speedster??...........Bruce

Bruce, "delta" in a math context means "change in". In this case, it's just shorthand for "change in temperature". In formulas, primarily derivatives, you might see it as "Δx" or "dx" meaning the change in x.

 

 

Stan, see my reply in the "Study Results" thread on why his setup doesn't actually tell you anything about the stock cooler.

I missed the part about no external oil bypass stat. That's a very important piece of the puzzle. Thanks for catching it.

Stan and Justin.....OK...So it looks like the external oil bypass will be the next addition to my system and then more testing. Skid tins will have to come later. Do you guys have recommendations on what one to use ? Keeping in mind that I like to have the least amount of hoses and connections ? if it means ditching my current oil filter arrangement....so be it........Knowledge is power........Bruce

 

Bruce, thanks for all of your efforts.

 

Apparently, obsessive-compulsive types do serve a useful function in society.

 

Was wondering if, while gathering all of this and reading the various sensor data while driving, if you got a feel for which sensor location best tracked the changes in cylinder head temperature.

 

Many of us with stock instrumentation have an unmarked oil temp gauge and no CHT gauge. We're always wondering what the oil temp needle is telling us about what the cylinder head temp is doing - which is probably more important than the temperature of the oil, anyway.

 

Any thoughts?

 

 

Yeah, absolutely. I keep recommending the Mocal sandwich thermostatic bypass filter base over and over to anybody who will listen. It reduced the amount of hoses to an absolute minimum.

 

Buy them here.

 

I would agree a sandwich plate is probably the easiest. Though you'll have to rework your hoses.

 

The sandwich plate just gets screwed on to your existing oil filter mount. The oil filter then screws onto the sandwich plate.

 

Hoses:

#1 Engine case outlet --> temp sensor adapter 1 --> oil filter mount inlet

#2 Oil filter mount outlet --> temp sensor adapter 2 --> engine case inlet

#3 Sandwich plate outlet --> oil cooler inlet

#4 Oil cooler outlet --> sandwich plate inlet

 

The temp sensor adapters would need to be relocated so they will always read the case outlet and inlet temps. If they were to be left on the oil cooler ports, there would be times they would give invalid readings depending on the state of the thermostat bypass.

Sacto.....Here's the way i think about this. i absolutely hate having those two Dakota gauges hanging under my dash. i am indulging them until I am satisfied and comfortable knowing that my engine is running cool and OK. Once that is satisfied i will remove them and get back to the simplicity of a wonderful looking dashboard form the 50s and 60s. I don't know of any way to correlate CHT temp to Oil temp.

I think CHT is more important than oil temp because oil temp. is subsequent. You only have to run one wire from #3 plug to under your dash and on to a gauge. How you run that wire is not too important since, in my mind, it's temporary. It's too bad that someone doesn't make a digital gauge for CHT that's 3/8" high by 1/2" and can be mounted in one of our instrument clusters where there's room to do so! There is plenty of room....I've looked.....Any electronic inventors out there?

Sacto....I hope this helps.......Bruce

Justin....is there any way you could send me a diagram of what you're suggesting ?......Bruce

 

Bruce, I know there are all kinds of compact CHT gauges available for the air-cooled engines used in aviation, but putting 'aviation' before most things means adding a few zeroes at the end.

 

 

Stan,

 

Mocal's ad doesn't say if the sandwich adapter allows some oil to flow to the cooler while the valve is closed to prevent air pockets or oil shock.  Do you know if the sandwich adapter allows any oil to flow through the cooler?

Justin and Bruce and all,
I am currently working on a 4 cylinder CHT gauge. It has 4 K-type temp. compensated thermocouples, and a 16 x 2 line display. It is run by an Arduino. I will temporarily install it under dash until I am satisfied all 4 are close enough to each other. Running a 911 fan on a type1 with a 911SC diverter (much modified). Just wanting to verify/modify until good. I know others have tried, especially Jake. I believe he was close but then sent all his efforts to the DTM, which he now owns.

Oh, and I have less than $40 into it, so reasonable for others to duplicate. When I get it done, I'll offer my code for free!

Danny.....Thank you.   Is it possible to post some photos ?  Bruce

Yes, when I get it working. It will be two small boxes, one under the shroud, connected by an RJ-45 cable to the display up under the dash. The thermocouples and hot/cold junction will all be hidden under the shroud.

Very interested to see what it looks like, Danny. Al

I added a temp control valve to my oil cooler because the engine would never get warm enough to produce any heat during sustained outside temps below 45F. Now my engine comes up to operating temp in 10 minutes regardless of ambient temps. I also added flaps and a thermostat. Once it snows I just park it.