parafrog

kid,
you just found the hole in my argument. the main recommendation i'm refering to advised coolant temps around 180 and oil temps at 210 for maximum performance. as you know, i have little experience with on the road temp readings on my vette (it's on stands waiting to be re-assembled). and you're right, the most important of the two is oil temp. this is because (i have read from reliable sources) the engine is mainly cooled by oil. the water jacket system has very limited access to the main friction engine components but does what it can, leaving most of the cooling to the oil system. you're definitely right abought watching oil temps during hard runs. i read last night that standard oils start to break down at 220 degrees, and running hard at low oil temps will encourage greater engine wear on the moving parts and reduced heat scavenging because the oil has not reached its optimum viscosity and flow-- meaning it can't get the job done till it's thin enough to flow easily.

i do seem to remember that in the short time my 85 was running in air temps around 80 degrees, my engine temps were on the money. this may have been because of the stock engine cooler. i read last night someone ran tests on an l98 with and without the oil cooler, and the cooler reduced oil temps 14 degrees.

but you're right. oil temp is where it's at; although, lower coolant temps will have have a definite effect on head temps since they are cooled by coolant alone, which will have an effect on detonation and through heat conduction intake manifold temps. reduced detonation means more fuel, ignition advance and more performance: which is probably why the ecm uses coolant temp and the knock (detonation) sensor in figuring fuel levels and ignition advance.

you'll have to excuse my bloviating posts, but it's my birthday and i've had a few drinks.

frog

Mike_88Z51

parafrog,

Not trying to flame you, but it appears that some of your current understanding of thermostats is as poor as mine was until I actually checked with a Stant Company rep. Stant supplies OEM thermostats to GM.

The goal of a thermostat is to restrict coolant flow in order to obtain or maintin a minimum coolant temperature for engine operation. By design, standard automotive thermostats are fully open approximately 20 degrees F above the listed temp. A 180 thermostat stays closed until the temp goes above 180. At 200 degrees it should be fully open. A 170 thermostat should be fully open at approx. 190 degrees.


I agree with CFI-EFI and eschoendorff that while a quality part isn't usually cheap, it isn't always the most expensive part available either. Sometimes you pay most dearly for mistakes and marketing.

"There's a sucker born every minute." - P.T. Barnum

65Z01

I dropped the big $$ on the HyperTech 160deg aux fan switch but, when it came to the 160deg T-stat, I picked up the cheapo at AZ; that was over 4yrs ago and still ticking.

C4Ownr24

my question remains unanswered.....

can i run just the 160 stat w/out modifying the PROM or running an aftermarket chip? Will the vehicle ever fall into closed loop, etc?

AGENT 86

I don't see a problem. I run a 160 stat and it goes closed loop at about 130*. Fan start up temps shouldn't change closed loop temps.

CFI-EFI

Either one of two things will happen. The engine will stay cold, shortening its life, or it will take longer to reach it's inevitable operating temperature, shortening it's life, somewhat less.



I paid about $8.00 for my fan switch. It is just a stock switch for a different application with lower settings. On at 205* off at 195*. It's about 10 years old and still good.

RACE ON!!!

65Z01

C4Ownr24 I agree, running a 160deg F T-stat with stock EPROM and fan switch will not adversley effect engine operation, in your context. The ECM will still go closed loop as soon as it did with the stock T-stat and the engine will heat up to 160deg F as quickly as before. The only change will be in what happens after coolant temps reach 160deg F.

There is a difference of opinion here as to potential engine damage/wear that may result from running oil temps low. My oil temp usually runs about 15deg F higher than coolant, i.e. ~175deg F. But don't foreget that the oil temp sensor is located just above the oil filter; for sure oil temp gets much higher as it passes through the engine.

Of course, you will not get the benefit of the 160deg T-stat in city traffic as coolant temps will mostly rise, though the T-stat will be fully open, till the fans kick on. On the highway you should see coolant temps running about 160deg F, unless air temp rises above say 90deg F.

CFI-EFI, that sounds like a great deal on the aux fan switch. What application did you find that was compatable with our application (I assume that the hole in the block is the same for CFI as TPI)?

Tom Piper

Look 3 posts up from mine:
Plus:
I didn't think any thermostat would cost $18, except the special type for the reverse flow LT1/LT4.


Tom Piper

CFI-EFI

I looked up the stock Corvette switch, then went to the specs on the back of the catalog. I picked a switch that had the same threads and wire connection as the stock switch. I don;t recall if I even looked up the application for the switch I selected. If I did, I've forgotten after all this time. Sorry.




I must have picked the wrong post and poster to name. I agree an $18.00 stat is likely to be for an LT, except the alternative was a $3.00 stat. I don't think you can buy ANYTHING for an LT for $3.00. Only someone selling "premium" snake oil could ask that for an L98 thermostat, which is EXACTLY what *I* think Hypertech is doing. The original post didn't name a year. I qualified my statements by specifying that I was referring to an L98. I'm sorry I picked on you, unfairly.

RACE ON!!!

C4Ownr24

so there won't be any noticeable performance gain from running a cooler stat? I assumed a colder motor would be more condusive to a denser, cooler air charge, IE more HP.

LT4BUD

[QUOTE=CFI-EFI]YEAH! Does anyone actually believe that Hypertech manufactures thermostats??? QUOTE]

Motorad makes the thermostats.......

http://www.motoradusa.com/index.html

Lone Ranger

Stant is the same tstat GM uses as OEM part. Stay with 180, though. Just say "no" to 160.

Lone Ranger

The only thing a colder motor is conducive to is more piston ring to cylinder wall wear. And less likelihood of burning off condenstion from the crankcase as completely as with a factory temp stat.

silver84

Since when does a chevy small block t-stat cost twenty bucks?
.
160 is fine, just make sure that once during your ride,
the oil gets to 180.

Tom Piper

That is precisly what the reverse-flow engines are supposed to address -- the cylinder heads run cooler while the block is hotter.
With a 160 degree thermostat, my digital gauge reads a minimum of 183 -- that means the block, which gets the coolant last (after the heads), is running at 183 degrees. With a 180 (stock) thermostat, the digital readout was a minimum of 194.

My oil temperature on my modified LT1 reaches at least 208 degrees (when running easy) with the 160 thermostat -- I've noticed the oil temperature runs higher since it was modified (I'm guessing that is due to increased valve spring pressures). The oil temperature ran 195 degrees when stock with a 160 thermostat.

What I can tell you is my '92 LT1 with 83K miles still has the crosshatch honing pattern on the cylinder walls (plus, no ring ridge) and has had a 160 degree hypertech thermostat in it since 24K miles. Also, it checks out very well on a leakdown test and I get at least 3K miles to a quart of oil (that's when I change it).
So, I don't believe in the "excess wear" theory with a 160 degree thermostat in the reverse flow engines -- I don't know about the L98 or increased emissions.

My main reason for the lower thermostat is , in Florida, on 100+ days and the poor air flow the C4 has over the radiator when not moving, I wanted more breathing room. And, heating is not a problem.

As an added note: I've had three Hypertech 160 degree thermostats.
I just put the third one in yesterday -- the setting on them gradually increases with time. I tested it by putting it in a pot of heated water on the stove and it was opening at 172 degrees. I could see the digital readout change over about three years. The new one opened at 160.

Tom Piper

Lone Ranger

160 deg is still too cold for climates north of the Mason-Dixon line.

CFI-EFI

First, a cooler stat doesn't guarantee a "colder motor". If nothing else is changed, a cooler stat only prolongs the warm up time. Under controlled conditions, like at the race track, where you can keep the temp down, between rounds, it is likely a cooler engine WILL make better power. Around town, the stat, alone, won't make a bit of difference.

RACE ON!!!

parafrog

don't worry, my feelings aren't hurt. ignorance is a curable disease, and i like being wrong--it means i'm learning something.

i was just thinking about why i ran a 180 thermostat in my old nova, and the temp stayed generally at 180 if the stat doesn't open fully untill 20 degrees beyond. and then it came to me. the difference is the nova has a constantly running flex fan, and the vette fan runs only when told. maybe a faster opening stat is called for on an electric fan car to allow radiator air flow to have a greater effect. i still think that a quick opening 170 stat is better overall for the motor; and then program the fan to come on to try and maintain 180 degrees--as long as the cooler temps let the oil stay around 210.

now i just need to find a company that makes them. anybody know one?


frog

parafrog

FYI, if you go buy a custom stat which I see is anywhere from 60 to as high as 80 bucks what your really getting is a stock stat and they only shim it so it opens sooner and in most cases is not opening when they claim it will for to make even more profit all they do is pour some liquid solder in to make the shim height and have no real control of how thich it will be. A real shim would then be the height you want, cannot change height and can pop out when you want to go back to stock opening temp or put different shim height in.

If your handy you can shim it yourself, could be free if you have something to use as the shim.

I spent a month testing stats after I got screwed with a so called custom stat that was to be 160 degrees but was really like 178.
The shim mod is listed in the Mods section of my website.
By doing your own shim you can always later on change the opening temp by changing the thickness of the shim.

As to the WHY, to me alumimum engines and parts do not transfer heat out as quickly as steel does thus if there is a heat spike it does not cool down quickly and under high loads heat just builds up and always takes much longer to cool down.

GM does not even turn the low speed fan on until like 220 degrees by then if you heat spike then temps could go to 240 real easy.

This will induce engine knock and less timing so if you live in a hot area like NV in summer with a stock PCM tune you could spend the summer running in the low octane timing table due to all the knock.
Remember once your engine has gotten enough knock it assumes you might have a bad tank of gas and it trips into low octane timing table and you are stuck there until you add more gas in.

Now if you change the thermostat, you get cooler water temps, also but cooler intake air temps, hence less knock, better timing, better performance.

If you went with lets say a 170 degree stat, tuned PCM so 1st fan kicked on at 171 and high fan keeps water at 190 that is a hugh max temp difference of 240 GM uses.

You cannot lower fan speeds without tuning for that and you cannot just put a lower opening stat for in heat having stat open sooner but fans still set high buys you zip.

160 degree stat without reprogramming PCM makes car run rich.

Best case though is to also cool the oil for if you cool water but oil heat just dumps back into water you gain little but if you also cool oil then both water and oil stay stable.

I would say oil should be about 15 degrees hotter then water temp.


_________________
JR
Custom Performance tuning for all 1984 to Present Y and F body models




something i just found on another site fwiw.

frog

Gary Murray

I bought a 160 Thermostat from Summit and it didn't last long stuck in less than 500 miles. What thermostats are reliable?