thermostat

[dskopek]

This whole thread can start as many questions as it can answer!! Most motors will make peak hosepower with a cool engine (160-180 deg F) and hot oil (210-225 deg F) This is seen all the time in dyno tests where the temps are more controlled then in a car. When you get to a street driven car I have to agree that you need to run about 180 deg water temp for everyday use and don't run a high flow thermostat. What you will find is again in most motors is the water flow is aready as fast as you want it to go and still get thermal transfer from the engine block to the water. If you move the water too fast the water temp will be lower coming out of the motor but the block temp and head temps will be up and so will the oil temp.

[95SleeperAcheiva]

Years back I ran a '92 Z-34 and if she was around 135deg coolant temp she was faster. This was on track temps of 95-110F. I tried a stock t-stat, then upgraded to a 180, she went faster. As I would experiment and let her sit and cool She ran faster yet. I modified a mustang stat of 110 deg and ran faster yet. I don't think it was too much to do with actual block/coolant temp as it did in allowing the intake or maybe motor in general to heat up and super heat the incoming air, and making it less dense. I watched my data records and noted a drop in engine temps along with the drop in ambient air temps, ya, denser air=more power. I confirmed this when I ran an air/water intercooler pumping ice water through it on natural aspiration engine and cut .7-1 full sec off my time! Remember this was USVI drag strip in the summer right on the ocean. So maybe in a street application you won't gain power untuned, but for single passes, it keeps the air cooler.

[reborngarcia]

OK i am going to add to this i live in Florida and it gets hot and sticky here. last time i was at the track at night i was still running over the 200 mark when i was staging after seating for a good 30 mins. my 2 cents is what if you run no t-stat in the car. it will still get up to temp??? and is it really that big of a deal if i do this? or can i run just water in the whole system with some water wetter.

[robertisaar]

no stat can still get up to 250*F, it just takes longer to get to the rated stat temps, but once it's there, it's more or less the same. and when there is airflow(either by some strong fans or lots of wind whipping through the radiator as you're driving, the temp won't be regulated at all, your coolant temp will be dependant on the amount of HP(and therefore heat) your engine is producing at the time and the amount of airflow going through the radiator.

[prophiseer]

Sorry to drag it up - but choosing a thermostat should really been a per application deal - unless you're dealing with an OEM motor. Reason being, everyone drives differently . . . as well, not everyone lives in the same climate . . .

Personally - I'm running a 175 for a few reasons. One, the collector on the front header sits less than 0.25" from the thermostat housing. There's an air gap, but it aint much . . . I was concerned with the coolant temps in this one specific area, especially if the motor is idling for long periods of time. Two; I live in a climate where our summers are absolutlely ridiculous between the ambient heat and the humidity, even with a stock motor, I was fighting to maintain temps I was happy with (I prefer the system to average 200F), and even more tired of the PCM constantly cycling the fans every couple of seconds. Three, our traffic lights here were designed by morons. It's not unusual to sit at one light for 3-5min, finally get the green, and the next light a few hundred yars ahead just turned yellow . . . get to the next light and wait another 3-5min. Unless you hit the highway or backroads, it's hard to get enough moving distance to let natural airflow cool things down.

Anyhow, my current setup tends to operate between 200F-210F (based on PCM's data) . . . she only pulls down cooler if I get it going for long stretches on the highway or the backroads. I haven't noticed any issues with oil contaimination, nor any reduction in fuel efficiency (through extended periods of highway driving) . . . hell, if nothing else, I average 34mpg on the highway as it is

But - such are my circustances for my situation . . . individual results may vary

[carbon]

Just have to throw it in because I haven't seen it yet reading through this thread...

FACT: A thermostat sets the lowest temp the engine will operate at after warm up, it has no effect on the maximum temperature. You cannot correct an over heating issue with a cooler thermostat. Only fans and/or a larger capacity cooling system can control high temps.

[geoffinbc]

Thats is very true.

[TechRod]

LOL


Couldn't miss the opportunity

[Daguse5853Z]

higher engine temps reduce emissions. this is a well documented fact. engines run better around 180 then they do 195 (performance wise). 120 is way too cold for anything. there is a upper and lower extreme to the spectrum. 195+ being the upper for emissions and 120 being the way low end for performance (using 120 as a example bc i saw it earlier in the thread). the reason 180* thermostats arent listed for newer cars is bc it's illegal for emissions. If you have a parts guy that knows his shit he can just cross over the demensions of your t-stat and find a good replacement IF he doesnt know his engine history. I would not worry at all about putting a 180* t-stat in my car. Put a 180* t-stat in, tune for it and enjoy the benefits.

[Daguse5853Z]

moisture in the crankcase isn't under pressure at certain stages through the oiling system.

So letting a car reach 212* will vaporize crankcase moisture, I never thought about it but it makes a lot of sense. So the fans should not turn on until 225*?

by the time the coolant reaches 180 or 195* you would think that the substance the coolant is taking heat away from would be well over the vapor point of water or condensation (the engine block is hotter then the coolant). Thats like saying the boiling water is just as hot as the flame that heats the pot. We all know that our stoves gets ALOT hotter then the water that it's boiling.

[82-T/A [Work]]

I kinda wanted to add to this... because people get really emotional on some message boards about thermostats. I always remind people that engines like the small block chevy were originally designed to be used with 160-degree thermostats, and they switched to 180-degree thermostats because that improved efficiency and combustion. The switch to 195-degrees was done almost entirely just for emissions. It kept the exhaust hotter and allowed the catalytic converter to perform better. But the V6/60, when it was in the original design phase, would have called for a 180 degree thermostat, just like the SBC at the time. They'd already gone to 195-degree thermostats across the board for emissions... but never the less, it was designed to work optimally with a 180-degree thermostat.

[SappySE107]

What makes it designed for 180 stat? The metallurgy? Piston ring material? Gaskets? Oil? The tune?

[82-T/A [Work]]

What makes it designed for 180 stat? The metallurgy? Piston ring material? Gaskets? Oil? The tune?

Kind of all of the above. I will preface this with you know way more about this engine than I do. But I hate losing an argument that I think I'm right on, though very willing to accept when I'm wrong. But there's a lot of misunderstanding about thermostats. I'm not saying anything you don't already know, but it bears repeating for this answer. The small block Chevy, for example, was originally designed and sold with 160 degree thermostats in the old shoe box Chevy cars. They realized eventually that 160 degrees was not necessarily optimal for engine efficiency and started selling 180 degree thermostats. This is why we actually have thermostats in these degree increments.

Eventually though, you guys all know how things went from 1974+. With the new catalytic converter requirement (which were charcoal canisters rather than the newer honeycomb ones we had), they sucked. They then mandated smog pumps on larger engines, because the single cat generally didn't work well, etc., etc.. Fuel systems weren't as efficient then, so most cars ran pretty rich... and increasing the engine temperature was done almost entirely to help ensure a more complete burn, and thus, emissions. It was basically done to help vehicles pass stringent emissions standards.

Specifically though, the V6/60's design began in the mid-1970s when almost everyone still used 180 degree thermostats. An all-cast iron engine does much better with a lower temperature thermostat because it cannot transfer heat in the same way that an aluminum engine can. This can result in the engine potentially running hotter longer than is ideal. The lower thermostat of course doesn't necessarily make the car run cooler; however, it does lower the potential floor for the engine's operating temperature so that it can cool to a lower temperature in most conditions so that it is overall less destructive.

People also say that the only way to improve cooling is to improve other things within the cooling system... e.g., a larger radiator, more cooling capacity, etc. That's not necessarily true as most vehicles are designed with some overcapacity intentionally... and thus, when you switch to a lower temperature thermostat, it does in fact, actually cool more quickly because it takes full advantage of the car's cooling capacity. For example, the Fiero is one example where there is significantly more capacity. The 84 Fiero has nearly 14.2 quarts of coolant (for the manual transmission car), compared to the 1984 Corvette which has an engine more than twice the displacement, which has 13.9 quarts of coolant.


All that said, there's other things to consider...

Most 80s GM vehicles go into closed loop mode at 167 degrees (if I remember correctly), so a 160 degree thermostat (if you wanted that for some reason) would actually require an ECM reflash, otherwise you would constantly be going in and out of open loop. More modern vehicles go out of open loop around 179 degrees, so a 180 degree thermostat would, like with the older cars, constantly have you going in and out of open loop.

The benefits of course to a cooler running engine (which is obvious to everyone) is that you're less likely to fatigue all the other parts in the engine bay... from alternators and starters to cooling hoses and everything else. The plastics will last longer, etc. What I like to also do with my 80s cars is wrap the exhaust manifolds and / or headers with header wrap. I'll do this all the way up to the catalytic converter, which helps the cat operate more efficiently. I rarely ever disconnect or remove the EGR system, mostly because it has zero effect at wide open throttle, and helps cool the pistons when I'm just cruising around anyway. A little bit of carb cleaner once in a while is a small price to pay for what it does add overall to the system. Plus if I wanted to remove it, I'd have to change the programming.


Hey, if you don't mind, I see you work for (or are the owner of WOT-Tech?), would you mind very much taking a look at my post that I made in this thread? https://www.60degreev6.com/vb6/forum...87-fiero-se-v6

I have MOST of what I need for an engine rebuild, but I really want to go "all out" on this Fiero. It's my car from high school, and I want this to be the last engine rebuild I ever do in this thing. I'm sparing no expense, and want the best rings, best bearings, etc. I'd be looking to buy a few things from your store to finish up everything I need before I start building it out.


Thank you!

[SappySE107]

How can you say higher temps = more efficient, and dismiss it as emissions. Efficiency is power.

Wrapping your exhaust manifolds to the heads causes detonation. The heads will get super hot. Speaking of heat, this is where the engine bay gets most of its temp from, not the radiator/block.

There is nothing that says open loop = rich. Its all in the tuning. We have done tunes with no O2. Permanent open loop. It can still run stoich and use coolant temp and intake air temp as modifiers. It just won't have O2 feedback to make adjustments in real time.