185 or 195 thermo?

Well first I guess, count yourself lucky, youre cooling system is obviously working really well to stay at 185 in the land of 120s in the shade....
A 195 would allow it to warm up more, however why would you want to do this?
Not flaming, just asking....
The motor will have better emissions at 195, but will also have slightly lower power, and also be more prone to detonation.
Kinda a trade-off...
But yes you could do it if you want to, there is no reason it wont work.
If ya stop by AMP on University say hey to Tom...

Dave-

Other effects of running a warmer thermostat:

1. The engine doesn't wear out as fast.
2. Less oil sludge buildup inside the engine.

Emissions are not better with a hotter engine. NOx compounds are produced in higher quantities in a hotter engine.

Please explain to me why a hotter engine makes less power. I believe that a hotter engine makes more power.

Please explain to me why an engine with slightly warmer coolant (195 vs. 185) is going to detonate. I don't agree that 10 degrees hotter coolant will make a difference.

Hack said:

Please explain to me why a hotter engine makes less power. I believe that a hotter engine makes more power..

Click to expand...

A hotter engine , has a hotter intake, and hotter intake charge. And lower volumetric effeciency.

Hack said:

Please explain to me why an engine with slightly warmer coolant (195 vs. 185) is going to detonate. I don't agree that 10 degrees hotter coolant will make a difference.

Click to expand...

Why not ? Hotter air burns easier. A slight advance in timing can cause detonation. So can't a slight increase in any other factor that promotes denotation be seen as a possibility.

10secgoal said:

A hotter engine , has a hotter intake, and hotter intake charge. And lower volumetric effeciency.



Why not ? Hotter air burns easier. A slight advance in timing can cause detonation. So can't a slight increase in any other factor that promotes denotation be seen as a possibility.

Click to expand...

I do agree that a hotter engine will knock more easily. I don't think there will be an appreciable difference, and I think the other effects of running the engine hotter (less wear, less sludge buildup) are worth it. You should feel free to run your engine as cold as you want. I'm not going to recommend that you do so, however. I've noticed that auto manufacturers are running engines hotter - do modern engines work well? I think so. Do they have problems with detonation? I don't think so. Do they know more about engines than I do? OH YEAH!

I agree with you that a hotter intake charge affects volumetric efficiency. But I don't agree that the intake charge will be significantly hotter. If you figure the % change in volume of air between 185 and 195, you get (654/644 = 1.0155) so it's a 1.5% change roughly. That's not significant in my book.

I would expect that long tube headers have a greater impact on under hood temperatures (increasing under hood temperatures, that is). Most people expect better performance with them, though.

Also, people have done studies on ram air set ups and found that they don't make much of a performance difference. There is a difference, but it just isn't noticeable.

As you have said it may or may not be an appreciable difference, but it will still be a difference.

EDIT: I'm not up with the whole engine not wearing as much because it is hotter thing - how does that work?

Hack said:

I do agree that a hotter engine will knock more easily. I don't think there will be an appreciable difference, and I think the other effects of running the engine hotter (less wear, less sludge buildup) are worth it. You should feel free to run your engine as cold as you want. I'm not going to recommend that you do so, however. I've noticed that auto manufacturers are running engines hotter - do modern engines work well? I think so. Do they have problems with detonation? I don't think so. Do they know more about engines than I do? OH YEAH!

I agree with you that a hotter intake charge affects volumetric efficiency. But I don't agree that the intake charge will be significantly hotter. If you figure the % change in volume of air between 185 and 195, you get (654/644 = 1.0155) so it's a 1.5% change roughly. That's not significant in my book.

I would expect that long tube headers have a greater impact on under hood temperatures (increasing under hood temperatures, that is). Most people expect better performance with them, though.

Also, people have done studies on ram air set ups and found that they don't make much of a performance difference. There is a difference, but it just isn't noticeable.

Click to expand...

Well since you know everything already I wont waste my time trying to explain about ASE certification in fuel injection and emissions controll, well over 20 years wrenching, etc..., etc...

I will simply say that in my experience and training:

1. warmer thermostats run cleaner emissions, one of the original reasons the factories began increasing from the 160's and 180's of decades past to the 205's and 210's of today.

2. one reason todays cars dont have as manyt problems with dettonation is due to modern head design, increased swirl, alloy, 4v, etc... a benefit many of the stangers do not get to take advantage of due to lack of design (4v), or lack of funds, desire for originality, etc... that is the diff in running a modern engine at 205 vs a 40 year old design at 205...

3. Im not sure which studies you are sighting, but I have seen numerous back to back tests with things like ram air leading to a 1 or 2 mph increases in trap speed with no other changes. I personaly put a great deal of stock in actual drag strip results as opposed to lab conditions, or on paper "proof" but again this is just my .02

I wish you the best of luck in all you thread hi-jacking endeavors.
Dave-

ddonaca351 said:

Well since you know everything already I wont waste my time trying to explain about ASE certification in fuel injection and emissions controll, well over 20 years wrenching, etc..., etc...

I will simply say that in my experience and training:

1. warmer thermostats run cleaner emissions, one of the original reasons the factories began increasing from the 160's and 180's of decades past to the 205's and 210's of today.

2. one reason todays cars dont have as manyt problems with dettonation is due to modern head design, increased swirl, alloy, 4v, etc... a benefit many of the stangers do not get to take advantage of due to lack of design (4v), or lack of funds, desire for originality, etc... that is the diff in running a modern engine at 205 vs a 40 year old design at 205...

3. Im not sure which studies you are sighting, but I have seen numerous back to back tests with things like ram air leading to a 1 or 2 mph increases in trap speed with no other changes. I personaly put a great deal of stock in actual drag strip results as opposed to lab conditions, or on paper "proof" but again this is just my .02

I wish you the best of luck in all you thread hi-jacking endeavors.
Dave-

Click to expand...

OK so you're angry with me. Not my intention, but that's fine. I've never said that I know everything - let me re-read my posts and check that...

1. Please check your facts. NOx emissions increase with higher exhaust temperatures. If an engine is really cold, HC emissions are higher. That may be the higher emissions that you are talking about. At "normal" operating temperatures, 185 vs. 195 - I don't think HC emissions will be affected, but I don't know.
2. Your statement makes sense. Also a modern engine doesn't vapor lock as easily due to the send/return fuel pump set up. And the cooling system is designed to run at a higher pressure to stave off boiling. People with aluminum heads get some of these advantages. If you are trying to tweak for every last bit of horse power you can get, this makes complete sense to me. Not sure the original poster is after that, though.
3. It also makes sense to me that you can get 1 or 2 mph in the quarter running cooler or using ram air. I doubt most people would quantify that as a noticeable change. If the thread subject had been "how to go as fast as possible in the quarter mile", that advice would apply as part of optimizing a car.

Not trying to hijack - am I off topic here? I don't want to fight, just to present my view point and the things I've read. I'm not a mechanic, just an engineer (my coherent electives in school were on engine design - I've always loved thinking about motors, too bad I couldn't get a job at Ford). My wrenching experience is much more limited than yours, I'm sure. Just 20 years of fixing my own vehicles (and I always drive old crummy stuff that breaks down frequently), that's about it.

Route666 said:

As you have said it may or may not be an appreciable difference, but it will still be a difference.

EDIT: I'm not up with the whole engine not wearing as much because it is hotter thing - how does that work?

Click to expand...

I'm not sure how the engine not wearing as much at warmer temps works. That's a great question that I wish I could answer.

On page 53 of a Tom Monroe book on rebuilding 351Cs and big blocks, there's a table. Under the table it says that the data is courtesy of Continental Motors. It's a graph of cylinder wear versus temperature during a 60 hour test. Tom includes it in the book as a tool to explain why you should always run a thermostat. It shows about 0.001" wear in 60 hours at 160F, and 0.002" in 60 hours at 100F, for instance. At 200F the line on the chart is very near zero (maybe at 0.0003" or less).

I would expect the graph is in most or all of Tom Monroe's engine rebuilding books. I know some people will knock book-learned knowledge, but when a hands-on guy writes the stuff down, it isn't just theory! Also, the graph is based on test results. Anyway, upon reviewing the graph, I see that the difference in wear between 185 and 195 is negligible on the graph.

So as I think about it I'm probably arguing one set of negligible effects against another and it makes very little difference whether you choose to run a 185 or a 195 thermostat in your car. However, one other thing that Tom says in his book is that the end cylinders tend to be more worn than the middles. I'd also like to run my engine a heck of a lot more than 60 hours before I tear it down.

Hack said:

Emissions are not better with a hotter engine. NOx compounds are produced in higher quantities in a hotter engine.

Please explain to me why a hotter engine makes less power. I believe that a hotter engine makes more power.

Please explain to me why an engine with slightly warmer coolant (195 vs. 185) is going to detonate. I don't agree that 10 degrees hotter coolant will make a difference.

Click to expand...

I used to have this car that would fail emissions every damned time when it was cold. Let it warm up for a couple hours...pass every damned time. Can't say overall emissions were better, but it certainly passed.

Less power is simple: ambient air will be warmer, therefore less dense, therefore less power, and also richer, thus it will be LESS likely to detonate and pass emissions unless there is a jet change.

skywalker said:

I used to have this car that would fail emissions every damned time when it was cold. Let it warm up for a couple hours...pass every damned time. Can't say overall emissions were better, but it certainly passed.

Click to expand...

Yeah, but if it had to pass smog, it more than likely had a Cat. And they shouldn't have tested it unless it was hot, and checked to make sure the Cat had fired off first. That's prolly why it passed when it was run for a while first.

Come back 65notch !! If it's not overheating, I wouldn't fix it man.

Hack said:

Stuff on temp vs wear that Hack said removed to save space. lol

Click to expand...

Ok cheers for that, it certainly is making me re-think some of my design, but I've been leaning away from the TOTAL extreme edge anyway, so maybe this will be part of it.

Do you think it could be that the pistons were designed to be heated to a certain temp to be properly round, and that cooler temps keep the pistons more ovoid and ill-fitting? Surely if that is the case though someone could make a piston less ovoid for an engine designed to run cooler?

Aren't high NOx caused by the continued catalysing of the HCs and CO, so while yes it is true that NOx will increase with heat, CO and HCs will actually decrease? Then perhaps OEM engines are designed for higher temps and thus the whole wear thing. Maybe piston shape has nothing really to do with it at this stage.