docmirror

Hmmmm, one of us - should feel insulted. Not sure which though!

Cuda911

Schnell Gelb

According the Hartech and Jake Raby ,the problem reduced by installing a LTT is cylinder deformation. The temperature spikes that cause cylinder deformation are not indicated by a high coolant temp gauge reading - because it does not measure the temp of the critical part of the cylinder .
The problem IIRC is lack of adequate flow around the vulnerable area. Once the OEM Tstat is partially closed ,flow to the vulnerable area (Bank 2 thrust face) is inadequate and cylinder overheating occurs - but is not measured by the stock instruments.
The LTT stays open longer and reduces this issue. The next stage is to modify flow in the coolant console and the cylinder head gasket and water jackets.
If cylinder deformation is the concern, the stock coolant temperature gauge in the instrument cluster is not a direct measure of the problem.It is barely an indirect measure. And driver anecdotes are obviously not a substitute for cylinder temperature measurements.
If coolant boiling is the problem ,that is a different discussion.
A simple way to measure bore thrust face temps on 4 ,5 & 6 would help.Anything closer to this area than the coolant temp sensor would help.
Just follow the coolant temp flow chart- the coolant sensor is a long way in the wrong direction from the critical area.

RennPart

We bought a boat load of the low temp t'stat's and need to move a few out the door.

https://rennpart.com/product/thermos...removed_item=1

while you're down there check to make sure your water pump isn't a duck call, we're glad we replaced this water pump on our 986. There was no reason to believe we needed to replace it until we pulled it off

docmirror

IIRC, both of those individuals found some design issues with the size of the coolant passages in various parts of the head casting on later engines, 3.6L? Where the coolant flows were restricted due to the same size holes being downstream from the flow direction caused some cyl to be poorly served by the coolant. But - I admit it's been a while since I read it.

As for the measurement of the entire system, unless we instrument every passage, every bottleneck, and every inlet/outlet pair, all I can say is the overall temp of the engine went down. If that means I had a hot spot in one cyl area(but I don't because I'm a 3.4), then reducing the aggregate of those instrumented collection of points means I had a reduction over all. My memory of thermodynamics from school is 30 years old, but I do believe the thermal xfer parameters between two areas of different temps still holds. So, If the coolant in the nearby passage is lowered, it will offer a thermal path for exchange to a hotter area. After all, that's the whole idea behind temp extraction of the entire cooling system.

I am unwilling to go to the expense of removing the engine, removing the heads, and grinding out the coolant passages for greater flow. So, I added a rad, and a lower t-stat as a reasonable low tech, low cost, modest gain alternative.

Schnell Gelb

It is not that hard.
The critical factor is the temperature of the thrust face of Bank 2.
An aftermarket cylinder head temp sensor + gauge for Bank 2 would be a huge step in the right direction.Just bolt on the ring terminal in the best convenient location.
http://www.ebay.com/itm/CHT-Cylinder...1UrtHM&vxp=mtr
http://www.autometer.com/cylinder-he...rmocouple.html
http://www.ebay.com/itm/CYLINDER-HEA...4AAOSwPhdVNzLe

JayG

I hope you weren't driving when you took those pics.
If so, you are in violation of CA Vehicle code and could get a cell phone usage while driving ticket

docmirror

I was driving. the pics were taken west of Fort Worth TX, and then in town.

The Republic of Texas does not recognize/enforce CA vehicle codes.

(*don't try this at home, pro driver closed course, YMMV, all sales final, contents have settled and may cause **** leakage*)

johnireland

To the other 99% of you who aren't having any problems, enjoy your car.

I once was driving my race car back from the track (old school), it was night, no dash lights, and as I passed an overhead street light I saw that my engine temp was at full max. I have no idea how long it had been there but I immediately pulled over. The pully that drove the water pump had failed...it split and took the belt with it. I let the engine cool down, it was bone dry so I added some coolant and made it to an all night gas station. The next day it was flat bedded to the guy who built it. Bottom line, no damage. No warped head, etc. This was on a 1958 Alfa Spider Veloce...1290cc, 8000 rpm red lilne every lap every gear every race. We put on a new aluminium pully, filled up the coolant and I continued to race it for two more years.

I have to believe that a Porsche that is 40+ years newer has enough engineering expertise invested in it to allow it to drive normally without thermal destruction.

JayG

LOL

johnireland

To the other 99% who are not having a problem, enjoy driving your car.

Many years ago I was driving my race car home from the track (old school) and without dash lights it wasn't until I passed under a freeway overpass that I had light to glance at my gauges. The temp was at the max...pegged all the way. I immediately pulled over. The pully driving the water pump had split, taking the belt with it. The engine was ticking like a bomb and bone dry. I let it cool, put in some fluid and made it to an all night gas station. The next day it was flatbedded to the shop. There was zero damage to the motor. No warped head, etc. We gave it a new aluminium pully, refilled the radiator, and I raced the car for another two years. This was vintage racing and we could not used normal coolant, only water. The car was a 1958 Alfa Spider Veloce 1200 cc, 8000 rpm red line, which it did in every gear, every lap, every race.

I have to belive that a 40+ year newer Porsche is built with enough reserve strength and capacity to handle day to day driving, even in 100 degree weather. And I have to believe that the engineers who design and build these cars, test them well enough to discover any thermal issues before they sell them to us.

docmirror

I never had any problem with the cooling system on my car prior to this alteration. It operated nominally.

I just made the nominal better.

Finally, I must say I'm flummoxed with all the picking of nits in this thread. I was hoping it would be used as a simple benchmark for what could be accomplished by making a mod which I found quite beneficial. Rather, it's been a list of 'yeah - well, GFY, I don't need it' theme of comments. All in all, a bit disappointing, and why I haven't offered any more observations on methods to improve.

Schnell Gelb

" it's been a list of 'yeah - well, GFY, I don't need it' theme of comments. All in all, a bit disappointing, and why I haven't offered any more observations on methods to improve. "
Sad, I agree when those of us who try hard to share and discuss technical issues get shouted down by the peanut gallery. On one other Forum I participate in, the Mod is ruthless and just deletes the posts you mention. The 'contributors' of the petty sarcasm and dismissive comments soon move on .The result is a very useful resource that I gladly support.
To be clear, your mod
1. did no harm
2. was inexpensive
3. follows expert conventional wisdom
4. was interesting and helpful.
Few other posts rose to that standard. So thank you for Posting.

Cuda911

I disagree. So far, it's been a good thread with various opinions. Tons of people recommend doing the low-temp T-stat swap, but I've also seen arguments against it, and also discussions that it has limited or no value. I think its a topic worthy of discussion from all points of view.

Since I put the low-temp thermostat in my Boxste' it has definitely been running cooler. Never even gets above the 180 mark during highway driving. On the track, it's bumping 225 or so. But, I changed out my water pump and did a coolant flush at the same time the t-stat was replaced, so too many variables.

KoB

Bear in mind that the center rad doesn't have a fan behind it. I see a decent temp reduction at highway speeds, virtually no effect otherwise.