Mikelly Posted September 24, 2000 Share Posted September 24, 2000 My fiance's brother made comment last night that it sounded like my motor was running to cool... I've been keeping it at about 180 degrees... Should I be shooting for a 190-200 degree running temp? I think I'm currently running a 160 temp thermostat.... Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
scarp Posted September 24, 2000 Share Posted September 24, 2000 TOO COOL ??? hmmm I have aways ran a 160 deg. therm on all my buildups and have not had any problems. I think the cooler therm. is worth close to 10 hp. Maybe someone else has more and better input. I may be running TOO COOL also.. Stan Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 25, 2000 Share Posted September 25, 2000 Actually, the efficiency (and max power) for any engine that tries to emulate the perfect Carnot cycle (our engines are known as the Otto cycle), the higher the temperature you can have at combustion, and lower intake temp before compression the better, until you get detonation. The problem being that as you appoach the boiling point of the coolant, the more of a problem you will have with nucleate boiling in the head waterjackets, and a hot spot in the combustion camber appears. Then you get detonation (or is it pre-ignition? I always get those confused). It's better to run a higher temp if your engine can handle it. I think this would be a great thing to test on a chassis dyno. Run with a 160, a 180 , a 190 F thermostat and tune to it, with fans blowing on the front of the car, and see how the power changes. The new cars have sensors that lean out the engine above 160F, so the hot tip for more power ends up being a 160F thermostat in that case. But Mike, with your low tech setup- carb, no computer (not knocking it, believe me!) I'd try a hotter thremostat. Remember, that puppy opens up at 160 or 180, and the cooling system still has to do the same work eventually. So putting a higher temp thremostat can be a power adder. With aluminum heads, I think you may be able to run a higher temp than iron. Also, a recent Stock Car Racing (I don't like the bump and crash NASCAR stuff, but the tech in NASCAR is phenominal) magazine had some really good articles on cooling systems. I'm interested in the "40 Below" additive, as they said it prevents nucleate boiling so that the hot spots go away. The Evans Cooling system looks interesting, a 370F boiling point, no water used, at 0 psi. Problem is I'd need to get their water pump and radiator, as it requires twice the coolant flow to work correctly. Quote Link to comment Share on other sites More sharing options...
John Scott Posted September 25, 2000 Share Posted September 25, 2000 My 2 cents: You want your oil hot and your intake charge cool. Thats why 160 thermos. make more power due to less heat transfer in the manifold. Kind of a band aid, but cooler mixture = denser charge= more hp. I can't find the low end for oil temp efficiency, but engine oil should not exceed 270 degrees. On the new cars, you'll see aftermarket chips that can't make power w/o the cooler thermostat. Is it just due to a leaner mixture? The hotter ones just peg the knock sensor even with the new calibration. I'd like to see a dyno test too. Would be interesting. I think there's going to be a big difference between FI and carburetion on this one. JS [This message has been edited by John Scott (edited September 24, 2000).] Quote Link to comment Share on other sites More sharing options...
scarp Posted September 25, 2000 Share Posted September 25, 2000 HEY DREWZ the more heat you make the less POWER you have... HEAT is wasted energy.(unless your trying to make heat) just check your physics books. maybe I'm from the old school but this is what I learned in PHYSICS class years ago... but maybe I'M wrong... hey peeps am I???? HEY good topic!!!!! maybe we will all learn something.... (hope I do) Stan [This message has been edited by scarp (edited September 24, 2000).] Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 25, 2000 Share Posted September 25, 2000 I think that DrewZ is actually correct, to a point, like I posted. When I was taking Thermodynamics class in college, I hated it, until I could see applications to hot rodding! That's where I got all that rot about the Carnot cycle, the Otto cycle, etc. Yes the heat that the cooling system and oil, and engine surfaces reject to the atmosphere is wasted energy, but the max power of an engine is theoretically greater for higher combustion temperatures (until pinging, melting, local boiling in the water jackets, etc.). I agree that if the oil is getting hotter and it's splashing on the underside of a V8's intake manifold, it's possibly a trade off. I tried to help that by installing a lifter valley cover to keep the oil from splashing on the underside of the manifold. I think the Edelbrock Performer RPM air gap intake is a much better way to go, but I had a manifold already. [This message has been edited by pparaska (edited September 24, 2000).] Quote Link to comment Share on other sites More sharing options...
scarp Posted September 25, 2000 Share Posted September 25, 2000 ok pete I see your point but back to the ? at hand 160 deg. therm. or higher? Stan again GREAT TOPIC....... Quote Link to comment Share on other sites More sharing options...
Guest Drewz Posted September 25, 2000 Share Posted September 25, 2000 A friend up the street always says heat is energy and energy is power. He has the worlds fastest propane powered car and has been racing for over 10 years this way so I trust his advice. He stays around the 210 mark but we are talkin about a killer engine, literally. I stay at 195 as steadily as humanly possible. Just my advice and opinion. Heat is power and that is my goal in all of this, POWER!!!!! ------------------ The only stupid question is one you wanted to ask but never did!!! Drewz Quote Link to comment Share on other sites More sharing options...
Guest Drewz Posted September 25, 2000 Share Posted September 25, 2000 The reason a cool can works so well is that it cools the gas and the air it mixes with. To simplify, if a steam engine has no heat it has no steam and no power. This is why nitrous is so effective. It condenses the air fuel mixture to make the engine work at or above 100% efficiency. There have been dyno tests in the past that I have read that prove this point. I read as much as possible so I can avoid small mistakes. I will try to find these articles but it was some time ago. Technology is better now so maybe I am wrong. I trust the guys I talk to since they are actually doing this for a living, 1/4 mile racing that is. They sell intake valley pans so you can keep the intake from being splashed with hot oil thus keeping the air/fuel mix cooler. Lots of things to take into account. I am sometimes right and sometimes wrong. Any effort from others to clarify would be helpful but please try to quote facts we can all rely on. ------------------ The only stupid question is one you wanted to ask but never did!!! Drewz Quote Link to comment Share on other sites More sharing options...
Mikelly Posted September 25, 2000 Author Share Posted September 25, 2000 I'm gonna pick up a 180 and 190 degree thermo and do a little testing to see what happens.... Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 25, 2000 Share Posted September 25, 2000 Scarp, I think the 180 or 195 thrmo is worth trying, especially on a wet intake system. It should raise the efficiency of the engine (more power from the same fuel) from a strictly thermodynamic engine cycle standpoint, but it might cause local boiling on the waterjacket surfaces adjacent to the combustion chamber. When you get local boiling there, the metal temps go up and you get hot spots that tend to cause pinging. I think it's worth messing with, especially if you have a Gtech or access to dyno time abd can do back to back comparisons. Not sure if a Gtech would be accurate enough though. Scarp, I hope that helps clarify my ideas? Quote Link to comment Share on other sites More sharing options...
Andrew Bayley Posted September 25, 2000 Share Posted September 25, 2000 P(v)=nRT Ideal Gas Law Basically, The warmer a gas (in this case, intake air) gets, the less density it will have. Picture this, compare a block of ice next to a plume of steam. Which is more dense? They are both chemically the same, only in different states. I've always hated Chemistry and wondered the same questions myself... why do they (the OEM's) run their engines so hot? Well, it comes down to efficiency. Not the volumetric efficiency that we all hear about, but the thermodynamic efficiency. Basically, it's the ability to burn all the hydrocarbons (gasoline) in the combustion chamber. Has anybody stood behind their car while it was warming up on a particularly cold day? Smelled a little rich, didn't it? Has anybody ever floored their car with the windows down (not that it matters in most Z's out there, just making a point)? Smelled a little rich again, didn't it? What's happening is that many of the hc's being drawn into the combustion chamber are not igniting in the combustion process. All these extra hc's exit the tailpipe as noxious fumes that contribute to the majority of the pollution's the government is trying to control. As we all are WELL aware of, automobile manufacturers are being mandated to comply with strict emissions regulations. A quick and easy way for the OEM to drastically reduce tailpipe emissions is to increase the operating temperature of the engine. With the hotter combustion chamber temperatures, the incoming air charge will be less dense. With a less denser air charge (less oxygen) fewer hydrocarbons are needed to slow the burn rate of the oxygen. This equates to less fuel consumption and fewer noxious tail pipe emissions. This was a popular solution GM used to solve high emission problems on many of their vehicles. The 305 and 350 TPI's both had an operating range in the 200's. Now ask yourself one easy question: did GM do this for horsepower, or emissions? Anything the OEM does is 99% of the time emission or safety related. So how does this affect us, the power hungry do-it-yourselfer's? Easy: Cooler Air = Higher Density Higher Density = More Oxygen More Oxygen = More Gas (to prevent a super-sonic burn rate, or simply called 'detonation') More Gas = More Emissions More Gas = Less Range Of course the following is also true: Cooler Air = Higher Density Higher Density = More Oxygen More Oxygen = Louder BOOM!!! (more power) Judge for yourself. Economy and clean, or power and smog? Knowing this, it's easy to see why people would be coming from both sides of the fence. Personally, I don't drive my Z enough to warrant a few extra miles per gallon as well as the lowered emissions. I live in an area that does not require emission controls on any vehicles, so this is not an issue. Also, in my search of a ten second ticket, I will do ANYTHING that might get me another tenth, or even a hundredths. This is why I run a 160 degree -stat. I hope I didn't bore too many people to death. Heck I warned everyone by putting an equation in the very first line of this post. Everything I've said is based upon a very basic theoretical understanding of thermodynamics. Exceptions ALWAYS exist. If I missed something here, please point it out to me. I value everyone's opinion here. -Andy Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 25, 2000 Share Posted September 25, 2000 Andy, I think you are basing your theory on intake air temperature/density. Very true that colder intake temps mean a denser charge and more power available in the compressed mixture, plus better knock resistance.. But that is only one of the temperatures that matters to the efficiency of the engine cycle, the other being the temperature of the charge after compression when ignition occurs. If the intake temp is the same (not affected by coolant temp) then if you increase the combustion charge temperature (after compression) you get a more efficient combustion process, like you stated. The thing is that more efficiency is your friend for making more power with the same fuel! The two do not oppose each other. The main reason that the new muscle cars can beat up on the 60s ones in the quarter, etc. for less fuel burned is that they are more efficient - not a bad thing! The larger the difference between the intake temperature (for reasons beyond just density) and the combustion charge temperature, the more power and efficiency the same engine has. This is all based on an adiabatic (no heat loss) perfect model, but if the same heat loss exists for both cases, it's a fair comparison. Sure a hotter running engine will loose a little bit more heat than a cooler running one, but not enough to make a big difference. So yeah, a cooler, more dense intake charge is better. But so is a higher combustion chamber temperature, which you can effect with a higher temp thermostat- up to the point that you get that local boiling I was referring to. John brought up the issue of possible hotter oil (from running a higher coolant temp) splashing on the underside of the manifold and heating the intake charge. Good point as that causes difference between the intake temp (actually the temp of the mixture before compression, which is what matters) and combustion temp to get smaller than if the manifold were insulated from the engine. But the under manifold splash tray or an air gap type manifold should help this. As would having a heat barrier coating put on the underside of the manifold. Quote Link to comment Share on other sites More sharing options...
Guest Drewz Posted September 26, 2000 Share Posted September 26, 2000 You are quite a bit more technically apt than I am but we seem to be along the same line of thought. I try to ask as many questions as possible so I can seem to know my way around before starting something totally blind. I am catahing your drift on things. Thanks for the time and input. Every bit helps in the end! ------------------ The only stupid question is one you wanted to ask but never did!!! Drewz Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted September 26, 2000 Share Posted September 26, 2000 quote: Originally posted by Andrew Bayley: P(v)=nRT Ideal Gas Law Has anybody stood behind their car while it was warming up on a particularly cold day? Smelled a little rich, didn't it? -not once I got the choke setup right A quick and easy way for the OEM to drastically reduce tailpipe emissions is to increase the operating temperature of the engine. With the hotter combustion chamber temperatures, the incoming air charge will be less dense. -Andy I do follow what you're saying and agree majority of manufacturer's efforts have been to meet emissions issues and the byproduct of some of their efforts has been more power to their surprise in many instances. But jumping up to bit " With the hotter combustion chamber temperatures, the incoming air charge will be less dense. " a higher head temperature can not dictate a less dense incoming air charge IMHO? Intake air temp is independent and if V.E. is good the air no matter what temp the source has, is drawn in and has a volume (swept volume) to fill. If engine has cold air intake and is drawing in 80F air it's making substantially more power than same temp head pulling in 180 degree engine bay air (~10% more from what they say). Now I don't know if the engine/intake of air happens fast enough to negate expansion of the air it just ingested and hinder filling of the cylinder or if it's fast enough to make this expansion before firing negligible? If I'm in lala land feel free to let me know:-) Been doing more soil/earthquake dynamics lately than thermo. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted September 27, 2000 Share Posted September 27, 2000 My vote? Go with a hotter thermostat - Pete is right on. Yes, th eINTAKE charge needs to be cool so that you get dense air and more oxygen but the ENGINE will make more power with a hotter shortblock. As for things liek Watter Wetter and 40 Below - this is easy, those chemicals break down surface tension and allow a better heat transfer to take place. I've used Water Wetter - it does exactly what it says it will do - lower temps. This is simply because it cools the engine more effeciently and draws the heat out. Mike on your setup the fresh air will keep intake temps cool once you get moving but at an idle the temps will be higher - no biggie and yes I've instrumented this with my Mustang. Even with turbos a WOT blast would see ambient temps in the intake with 10lbs of boost - very nice GM and others didn't just bump engine temps up for emissions. If you floor a cold car and smell gas it's running rich. If you could keep it at that temp all the time and tune th ecarb fo rthat you wouldn't smell gas - but it owuld run like crap too. Not to mention the wear on the components from the cold oil - piston scuff anyone? check out some of Smokey's stuff - I'm pretty sure he advocated a hotter engine temp for more power. Evans cooling sounds really cool - but mucho' expensive. Pullies, pumps, radiators, and special coolant. Engine will run much hotter temp-wise but the coolant will prevent local hotspots and detonation if memory serves - very nice but too pricey for me. P.S. The stuff you put in your dishwasher to stop spots also breaks down surface tension ala 40 Below. I've been told it works great in a cooling system too but I've always worried about water pump wear. Straight water cools better than anti-freeze too if anyone didn't already know that. Anti-freeze raises boiling temps at the expense of heat transfer. If you doubt this try running straight anti-freeze but don't drive far -) Quote Link to comment Share on other sites More sharing options...
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