Internal Thermostat and External Tank Question(s)?

[KTL]

The topic about internal thermostats got me thinking about the oil system upgrades.

Staying on the same subject, sort of.... I see when some switch to a forward oil tank and they install the fancy oil filter console in place of the engine-mounted oil cooler, the t-stat is removed. I assume this is because if you leave the t-stat in place, you don't get flow thru the filter until the thermostat opens?

http://www.smartracingproducts.com/pdfdocs/911oilsystemoptions.pdf

http://www.smartracingproducts.com/pdfcat/srp2009_engine_fuel.pdf (pages 5 and 6 of pdf, 29 and 30 catalog pages)

Shame to remove the engine cooler, as it's said to be quite effective? I suppose the key is to ensure the front external cooler is very effective.

That console, is it just SmartRacing's trick to getting a filter in the pressure circuit? I would think an inline filter elsewhere in one of the external lines could accomplish the same? Because one could leave the engine cooler in place and simply braze an appropriate AN fitting onto the engine cooler to replace its existing hose clamp beaded tube fitting. I do understand that installing a forward tank requires a new filter location because when the original rear oil tank goes bye bye, so does your oil filtration- on the scavenge circuit.

That got me to thinking, not that I want to try this, but has anyone ever seen an attempt to put the original oil tank in the front trunk? Just thought that was kind of funny to visualize what a mess of plumbing that could make....

Thanks,
Kevin

[neilca]

I have not put the tank up front but I have the cooler up front and a filter prior to the cooler.

Word of warning...when the scavange oil hits the oil filter on start up the pressure gets very high. Enough to blow the filter apart. Lets just say I have data on this. The factory tank has a bypass valve at the filter that bypasses the filter until the pressure equilibrates and can safely passed through the filter. I had to put in an external pressure relief valve prior to the filter that bypasses everything and dumps directly into my tank.

Hope this saves someone a big oily mess.

[Eagledriver]

Kevin,

The only way I know of to put an oil filter in the pressure circuit is to use the oil cooler circuit like the Smart Racing mod. You cannot put a filter on the big tube at the bottom of the cooler because that is a suction circuit from the tank to the oil pump. A filter there would cause a pressure drop and possible cavitation of the pressure pump with catastrophic result. The engine oil cooler is pretty effective as you note. I currently have my engine cooler bypassed due to a major leak in the cooler. The temps are about 20 degrees higher on the track without the engine cooler.

-Andy

[Walt Fricke]

One reason many of us who race replace the engine mounted oil cooler with a filter is that is what the factory did with its race engines.

I have three filters - one up front before the center mounted oil coolers, one between the coolers and the tank, and one in place of the engine oil cooler. It is always clean.

I use a Canton Mecca as the first filter, and stainless mesh filters for the others. I have no thermostats, so am careful to warm things up. No filters have blown apart. The CM does not have a bypass, and its cartridges only have looked bad when an engine has blown up.

I don't think the stock oil cooler would fit in the smuggler's box, which is the most common location for up front tanks. Not a very promising idea anyway.

Oil coolers mounted up front in the valance tend to be very effective. Way more so than fender mounted ones.

[KTL]

Thanks for the feedback guys. I didn't mean to imply I wanted to put the filter ahead of the lower tube on the cooler because that would indeed put it in the suction circuit like Andy said. I was suggesting that the cooler need not be eliminated if the tube is modified to accept an oil line fitting, which would make it easier to keep the engine cooler in place when the rear tank is replaced with a forward tank?

However with the engine cooler remaining in place, then we have to insert a filter in the pressure circuit elsewhere. The only choice would be the outbound line to the oil cooler. We wouldn't want to put the filter only on the inbound line from the cooler because it doesn't protect the cooler in the event of an engine failure?

Andy, did you bypass your engine cooler with the SRP thermostat blockoff or just modify your existing factory t-stat? Used coolers, while they sometimes may be of questionable condition, are fairly plentiful so I was surprised to hear you bypassed it instead of replacing. What temperature do you see right now? I see between 200-210 on mine, so i'm not sure i'd like to see 230 on a regular basis if I ditched the engine cooler.

I think i'll be using a full flow filter like Walt mentions. Either a Canton or a System1. It doesn't have a bypass, but since it's full flow there's no need for a bypass. It's my understanding that the stock Mahle filters run in bypass mode alot since they see high oil pressure at high rpms during racing?

I was really joking about the stock tank being used up front. Just thought it might prompt someone to share their what-the-heck-is-that experiences of seeing someone else trying to rig up a makeshift front tank installation. I've also considered sourcing a 964 tank to put forward in the rear wheel well. Others have done this with success and I think the plumbing is a little more to the engine's liking- closer thermostat. It doesn't go so far as to improve the 911's rear weight bias, but it does put the tank nearer the car's center of mass and avoids running a large oil line thru the cabin.

[Walt Fricke]

I run a filter in the scavange line before the front coolers, and another one after the coolers but before the tank. Works great with a turbo oil pump, and seems to work also with a 3.2 pump. The pressure side filter is just there as a last ditch measure. Having a filter on the scavange line is, of course, where the factory put it - even though it is all the way back on the tank inlet.

[KTL]

Whoops, I stand corrected. Thanks Walt, I forgot that the outbound line from the case to the front oil cooler is scavenge-pumped. I have a mean 930 pump in my engine. It's somehow been modified by Dawe Motorsports when the engine was built years ago. Cranks out a solid 80 psi on the mech gauge when i'm wide open on the track up to temp. At cold startup it's pushing 100 psi. So I should have no issues with an extra filters taxing my pump too much.

Was flipping thru Bruce Anderson's book last night and ran across mention of replacing the cooler in the pressure circuit, i.e. the engine mounted cooler, with a more efficient cooler. What I took notice of was he mentioned a cooler in this instance is typically more effective when placed in the pressure circuit. However he also noted that all of Porsches racecars have always had the cooler in the scavenge circuit. Just thought i'd share that bit of info. I found. Not planning to replumb my oil cooler system- i'll stick with what currently works ok.

[Eagledriver]

I bypassed the engine cooler by inserting 2 discs of aluminum under the seals. This blocks the flow of oil into the cooler. I then put a dummy thermostat in with the guts removed so the oil can flow all the time. I've blown 3 coolers in 2 years, and I got tired of replacing them. Might have to get another one for the summer races.

-Andy

[Walt Fricke]

Andy

If you still have one of those blown coolers, and can TIG or know someone who does, you can make use of part of one.

Cut the cooler part off of the base and discard. On the bottom of the base, weld on a big AN fitting as appropriate (or don't cut off the long aluminum tube, and leave it). Up top weld a plate over the area where the inlet/outlet holes are, being somewhat careful so no oil can cross from one to the other. Make holes in this plate, and weld on -12 AN fittings. You have to offset/stagger these in order to have enough room to attach and tighten the hose fittings.

Then you can either 1) mount semi-remotely another filter (poor man's factory setup, should be less expensive than using the 964 part?). A really good front valence cooler does away with the need for the engine mounted cooler, at least for track use (not sitting idling/low rpms in traffic).

Or, 2) you can mount in some suitable nearby place where you can duct air an aftermarket oil cooler.

Or, in your case, you could just have these two reconnect, but put a gauge in there, the further to chase down your mystery leaking coolers?

This could also accomodate the cooler setup Anderson mentions. If a guy is building a pure race car, and is after max weight savings, he might keep his oil sump tank back at the rear, and figure out how to move the engine oil cooler (perhaps increased in size) to a breezy spot back there also, thus saving a fair amount of weight in piping and the like. I've seen cars configured like this, though I am happy with my more conventional race car front coolers and front tank setup. I could save some weight by using aluminum tubing instead of Aeroquip, or the newer (very $$) light weight hose.

[Eagledriver]

Those are great ideas Walt. I don't think I have an oil pressure problem (dispite blowing 3 coolers!). I just think that used 30 year old coolers aren't that reliable. My first one lasted a couple of years with this motor. I have a pretty good front cooler in the bumper and can run like that for now. I'm actually thinking of trying one of the aftermarket replacement engine coolers from Tasker sold on Pelican for 500 dollars. I'm going to call them and see what they have to say. I also think I could add another front cooler (in the fender) to solve any issues I might have in the summer.

-Andy