Van

Great question. Is the stock cooler "bottom in"?

kurt M

dono, I am just an HVAC guy. I would guess that it is side in and out which for most thigns works best with regards to air trapping, draining during service and the like.

Low chin mounted coolers and oil lines make me nervous. Too bad there is not a better place/way to install them higher in 911 and the 944 variants that is less likely to get damaged in a off track. There is in the 911 but it is not a simple bolt in kind of thing. I see a fair number of cars come in busted from off tracks and the only thing damaged is the cooler and chin spoiler area.

Mike Buck

I had a second factory cooler installed in series. Not much savings over buying the KISS kit when you total in the cost of pricey metric/AN adapters you'll need more of to install a factory cooler to AN lines. Cleaner install though because there is a nice space for it already on the drivers side.

Willard Bridgham 3

There really isn't a lot of room on the drivers side wheel well and it is the same 5 lbs of poop in a 3 lb bag problem with the Kiss cooler.

We measured up for a stock and kiss cooler and what made my mind up is the much larger size of the kiss cooler for about the same amount of work/piping.

RedlineMan

Yep;

That is what it usually boils down to. I could do ANYTHING someone wanted, but it is usually easier and more effective to simply do it all myself. I spend more time modifying "pre-engineered" kits than I care to mention. However, if a customer insists, I will gladly charge them all the extra time it usually takes to use a kit.

Kurt - That is how the cooler/fittings fit best. Never considered air pockets. It's all presurized most of the time. The car is happy and healthy. Not sure it is an issue in the case of motor oil.

kurt M

simple to test for trapped air. have an IR gun at the ready. With the motor warm and ther thermostat open and oil flowing through the cooler spray the cooler with a garden hose for 20 seconds or so. Then right away start scaning the cooler top to bottom as it warms back up. If you have trapped air the top of the cooler will take a bit longer to warm back up. Trapped air will measurably reduce the cooling ability.

Van

So, I know everyone thinks the stock cooler is crap... But I've used it anyway. Primarily because I already had it - so it was free.

First I did a little hacking and modified the air duct, then I bolted it in place on the left side of the radiator, and then, by using a set of factory hoses, I was able to come from the top of the original cooler to the bottom of the new one, then from the top of the new one back to the engine. (I did have to weld up a little male-male coupler from parts I cut off of 2 spare hard lines, but, again, that was free!)

Anyhow, we'll see how it works.

joonas

Carroll Smith Tune to Win
"When using multiple heat exchangers remember that the greather the difference in temperature between the liquid to be cooled and the air that is doing the cooling, the greater will be the temperature drop across the cooler. First, plumb multiple coolers in parallel rather than in series. Second, do not mount your oil coolers directly ahead of or behind your water radiator. The air coming out of the water matrix is just about at water temperature and won't do much of a job of cooling the oil and vice-versa."

Jeff Lamb

I am putting a couple of large Setrab model #634 oil coolers in my 911 race car and I am mounting them side by side (not one in front of the other). The air entering the nose of the car is being properly ducted to the front of the coolers and then exits the rear of the coolers out ducted vents (large louvers) in my hood. The coolers are both the same size at 12" tall by 10.5" wide so when I run them side by side they will fit in a space that would have allowed me to run a single really large oil cooler that is 12" tall by 24" wide. The oil cooler cores are 2" thick. Since both coolers are exactly the same size, I was thinking about plumbing them in parallel by using the approriate T fitting to split the single oil feed line into two supply lines and then using a T fitting to combine the oil returns back into one line returning to the dry sump tank.

HERE IS THE INTERESTING PART -> I spoke with the guys at BAT Inc (they sell Setrab and Mocal oil coolers), and they recommended that that I should NOT plumb them in parallel unless I had TWO SEPARATE SUPPLY LINES WITH TWO SEPARATE OIL PUMPS to feed each cooler on totally separate circuits. Well . . . as we all know, the 911 engines only have one main oil pump supplying one main oil exit pathway from the engine. Therefore, this means I am going to plumb my two coolers in series.

The reason the BAT guys do NOT recommend running the oil flow from a single supply line run through a T fitting to supply the coolers in parallel is because oil follows the path of least resistance which can cause dramatic flow differences between each cooler that is run in parallel. They explained that if one cooler starts running warmer (or warms up faster) than the other cooler, then the oil flowing through the warm cooler receives basically all of the oil flow because the oil naturally flows through the warm cooler since the viscosity of the oil flowing through the warm cooler is much more thin (like water), whereas, the viscosity of the oil in the cold cooler is still thick (like syrup). This creates sort of an endless cycle of the warm cooler receiving more warm oil, whereas, the cold cooler with cool thick oil just isn't getting any oil to get it warmed up. If you are running two fairly large oil coolers (like me), then the chance of this happening is much greater since the 911 dry sump oil pump probably doesn't pump quite enough volume to really force the warm-up of both coolers equally. Make sense?

The above issue is much less of a problem with water because water doesn't dramatically change its viscosity (when warm vs. cold) like oil does. Therefore, when running a single supply line (as opposed to two totally separate circuits) you should probably be able to run two water radiators in parallel without as much of a concern as running two oil coolers in parallel.

Does anyone have any additional information I should consider before plumbing my oil coolers in series?

Thanks,
Jeff

Larry Herman

Having experience with parallel coils in other disciplines (refrigeration and plumbing mostly) that makes a lot of sense. The changing viscosity of motor oil is quite unlike most other applications.

67King

Seems to me that running straight weight oil solves this problem. But furthering that line of thought, flow losses increase squared wtih velocity. As oil is incompressible, the difference in flow rate would result in a velocity change. So if you don't have a perfectly balanced system, it should be more or less self correcting, unless you start out with a big temperature difference. Havnig said that, you'd want your oil coming from the bottom of the T, so it is forced to make a turn. T-ing off one line to the side will cause a big difference in the losses between the two sides.

joonas

http://books.google.ee/books?id=dULs...esult&resnum=4
Page 123 point 6 for example.

I have not tested parallel setup so I cannot be sure.

Van

Great information!

Jeff Lamb

The book referenced in your link appears to be referring to building water cooled american V8 engines and my guess is the author is assuming that any oil coolers used for that application will be relatively small and restrictive when considering the volume of oil flow to be dealt with when dry sumping a big american V8. Therefore, I can see why running two oil coolers that are relatively small would result in the recommendation to plumb them in parallel.

In my case, I am running two very large coolers and probably either one alone could easily flow the full oil volume being generated by the 911 oil pump with very little restriction. Therefore, BAT was saying that I don't need to run my coolers in parallel to avoid any flow restriction. They then went on to explain why I should NOT plumb my two large coolers in parallel (as explained in my earlier post). My guess is that if I were running two smaller, more restrictive coolers, they would have recommended running them in parallel.

Please keep in mind that my comments about the book are only my assumptions of what the author is intending and I could be completely wrong!!

I guess my only point is that I originally thought that running two oil coolers in parallel would always be the best alternative . . . but it turns out BAT has informed me that things are more complicated than what I originally thought. I would have never thought about significant flow imbalances between two large oil coolers until they pointed it out to me. So . . . the size and flow rate of your two oil coolers is one other factor to take into account when deciding how to plumb your oil coolers.

Jeff

Jeff Lamb

These are some good thoughts, however, I think even straight weight oil still changes viscosity as its temperature increases. However, I am sure that it doesn't change quite as much as a multi-viscosity oil so it should be a help.

I think I am going to install a temperature sender on the exit of each one of my oil coolers so I can measure the results when I eventually experiment with running them in parallel vs. series. I will start out running them in series and at some point I will find some time to switch them over to parallel and take some more measurements to see if the temps ever really get out of balance between the two.

Jeff