Pullers are much more efficient than pushers. Design the fan size, placement, and shroud correctly and you shouldn't need both.
Both True. But you get a little offset in piston diameter vs thinner walls - smaller pistons hold less heat and have less frictional losses. Most modern smaller engines that are being designed for mileage are favoring small bore, long stroke do to the frictional losses.
Excellent Post I learned a lot today Thank You wish there were more post like this one.Like 4sd Trans a close and wide ratios the one I have in my Falcon is out of a 67 Mercury Cyclone wide ratio the 347 that's in it now should put out about 350hp but the plan is a 427 SBF not trying to Change the subject but will it hold ? I am running a Currie 9" 389 Trutrack with a 10" tire
It depends on what trans it is, But lets not dilute this one - start a new thread asking the question
Yes it does but often you must take into consideration HOW it leaves in the exhaust. Back when I lived in Az. I played with several engine/car combos and with the same engine in the same rush hour traffic route I got the following: with headers the engine would overheat until I put a hood scoop on the car I could make it home just about as it got hot. Take the same car/engine and with stock exhaust manifolds and no problem, put the engine in a '57 pickup and even with headers no problem. So a way for the hot air to leave the engine compartment, or a bigger space under the hood help keep engine temps down. This was done with stock radiator, no shroud back then except if you could find some factory one to install some how, a stock fan etc. in all cases and fellow hot rodders there and then had similar problems and results. All my engines were .030 or .060 over and compression from just warmed up to 11.5 to 1, the latter with 30 over cylinders was the worst in Az. but fine in San Francisco.
The peak temperatures difference doesn't compare to the faster pressure decay of the higher compression ratio. At similar power levels the higher compression runs more thermally efficient, therefore less heat to the cooling system.
I saw the weirdest thing at the Ventura Nationals one year. We were sitting around the Motel 6 parking lot at midnight when a '32 Coupe pulled in. Naturally, we crowded around to look and had a WTF moment. No FAN, no GENERATOR and no BELTS for the water pumps. We asked him where he had come from. If I remember correctly, it was Palm Springs. We asked were the aforementioned pieces were. He said he didn't need them. He went on to explain that hot water will siphon cold water from the radiator therefore he didn't need the fan or pumps. He charged his battery overnight so he didn't need the generator. The following year, he showed up again, but this time, he had one of those emergency belts which look like a plastic bicycle chain running his water pumps. He still didn't have a fan or generator. Go figure........
I'm not so sure. For sure the higher compression is more thermally efficient overall but that is not the same thing as what % of the inefficiency ends up where. A real cycle comparison graph has the higher compression starting temp higher...a LOT higher if you're comparing 15: to 2:1..... you might be right that the lines never cross but......it seems like there is probably more to it and that is a different graph than normally gets drawn in thermo cl***. It seems like it may be a bit like the adding insulation to a pipe problem where more always seems good but at some point the extra surface area mean adding more insulator effectively makes the pipe less well insulated. maybe not through.....
Just as an added rule of thumb I believe this is the correct way, jump in of not. Higher temps at idle indicated inadequate air flow, higher temps at highway speeds relates to lack of coolant flow problems. My flat head mopar 6 runs the stock fan and radiator with 0 pressure and a 160 degree stat. Usually cruises at 170 to 180, barely ever goes over 190, regardless of ambient temps. I have also been running 30 coolant 70 water for the past 12 years. Don't drive in the winter, and it never goes below 30 in the garage.
Since it has not been mentioned yet let's not forget the how critical engine oil temperature is in the grand scheme of things. It accounts for a large percentage of cooling. Some of the most effective cooling systems incorporate heat exchangers that use radiator water to cool engine oil. I would not completely agree with everything that's been said but every engine is different, some even have different coolant flow patterens and certainly things like air in the system, cavitation,boiling point, coolant capacity, oil capacity and allowing proper time for heat exchange are key. As mentioned there are many variables that effect the combustion temperatures but oil temperature is very important.
Being that antifreeze/coolant raises the boiling point of water, I find it very hard to believe that straight water has greater cooling capacity than a 50/50 mix...
Boiling point and ability to cool are 2 very different things. The boiling point goes up but you aren't going to run the system hotter really becasue you damage the engine so that doesn't help you other than providing a bit more safety margin on top to boil.....and less safety margin to damage so it's a trade off. The cooling question is different though. The ethylene glycol only holds about 1/2 the heat that water holds at the same temperature....and a 50/50 mixture holds about 3/4. That means a 50/50 mixture needs to circulated about 1/3 faster than straight water to take out the same amount of heat...and that in tern means the radiator needs to be about 1/3 bigger to give the mixture enough time to dump the heat into the air. I know a few that swear by Evans coolant that boils at 500F or something like that but again it has a lower heat capacity than water so.....but they claim it wets out better and has better thermal contact so it works better even with the reduced heat capacity. I've never tried it in a car because not boiling scares me because it means I HAVE to always watch the temp gauge or get the ECU to do it for me. I did use something very similar in a high temp fuelcell system and it worked fine, but the stuff was pretty thick when it got cold.....and I had 2 separate sensors hooked to 2 separate computers monitoring things.
I'd like to point out that an older engine is not designed to run at higher temps. If you have a nailhead in your coupe then it is designed to run at 180ish, you have a sbc cratemotor then 200ish. Don't think you can apply todays principles to an older motor, they were not stupid back then and they could design the engine to run at whatever temp they wanted and they determined that 160-180 is what they wanted and they went to a great deal of effort to make that happen.
I stumbled across this stuff recently: http://www.jegs.com/p/Engine-Ice/Engine-Ice-Hi-Performance-Coolant/1348309/10002/-1 but have never tried it in anything.....they claim it will drop your operation temp 10-15 degrees and it is water based so at 240-250 it boils to let you know something is wrong.
a ton of great info here, without a doubt. but again you have to look at your specific car, truck etc. a grille on a forty ford lets a small amount of air flow in, compared to a 55 chevy with a larger opening and larger engine compartment. alot of good info, you need to take it all in, and see whats works for you. great read guys, on what we all get to deal with on our cars. thanks.
I'm talking about the same amount of fuel burn with a higher CR. I we are well within knock limits the higher CR engine will make more power from the same amount of energy because more of the energy is used because of the greater expansion cycle. Now that's a generalization. As I said when 9-1 came into vogue we had all kinds of heating issues. Of course there will be other situations and examples, I just wanted to say that raising CR probably won't increase heat load on the cooling system.
It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so. Theoretically, straight pure H2O (water) has the best cooling capacity. Cooling capacity is the ability to absorb and shed heat. The problems are: * its really hard to find pure h20 . * there's no corrosion protection * there's no water pump bearing help. * it freezes. So we need to add stuff to help. Like everything it's a compromise, and don't add more than you need because it has draw backs and you'll pay for it someplace else. Anti-freeze from the parts house has most of the problem solvers in one package. These adatives reduce the cooling capacity. The more you add the more its reduced. For most guys with hot rods, the biggest issue is not overheating durring our driving season. Some guys with 4 season drivers need freeze protection, and some guys never ever see a day below 32F depending on locations. So for most guys, a 50/50 mix's biggest benefit is freeze protection to -58f. Are you really going to drive your hot rod in 58 below zero weather???? The cost of that huge benifit is about a 30% reduction in cooling capacity. In other words- you'll be 30% more closer to overheating in the hottest of days. Sure seams counter productive if you ask me. An 80/20 mix will give you the beneficial additives, and only reduce the cooling capacity by a few percent with some freeze protection below 32*f for the fluke cold snap.
i don't disagree with anything you are saying really...there is no question that going up on CR will reduce exhaust temp. Where I'm struggling is how much heat ends up in the coolant. All the engineering books and graphs I've ever seen ***ume adiabatic compression and expansion which means no heat loss from the system, which mean zero heat going into the coolant.....but that's not true, heat does go into the coolant so the standard graphs don't really answer the question at hand. Then I got thinking about what I'd need to know to solve the question of how much heat into the coolant and I think the temp profile inside the cylinder and the profile changes with compression.......I would need to graph it I think and toy do that stuff like rod ratio come in.....and it turns into a pretty tricky thermo problem pretty fast. You might be exactly right....I just don't know
True and I can't swear that what I said is an absolute truth, but I know the opposite hasn't been true in my experience. The increased efficiency from the same heat content comes from higher Max T and Lower T or increased Delta T. If the average T was the same then the higher CR would benefit from less exhaust heat into the cooling system. The 9-1 engines were kind of extreme examples as we went from 14-1 or so down to 9-1. That's why Turbines are more efficient at a fixed load, 10-1 compression, 100 - 1 expansion. Hoop
Just to further my understanding- The conservation of energy law has to apply someplace here right ? If the same amount of fuel goes into two different engines , one with high compression and the other with low compression. Both engines will convert the same amount of lbs of fuel to energy - power and heat ( out the pipes and into coolant) . The high compression engine will produce more power so there needs to be less heat someplace, right ?
Okay, how about this. My radiator is buffed aluminum and sits out front, I have a T bucket with no hood. Would being in the direct sunlight on a 95+ degree day have that much of an effect on cooling temps? I've read where a couple guys have noted that under hood temps seemed to cause cooling problems, so how come a hot rod with NO hood would suffer? Naturally, a proper setup is needed, but wouldn't the open hood car run cooler? It's amazing that for a lot of stuff, there's a basic formula for efficiency, but cooling an engine is always a mystery.
Conservation of energy ALWAYS applies and a higher CR engine converts more energy into work and less into heat. The heat goes out in 2 ways, the exhaust and the coolant. On a higher CR engine the exhaust is for sure cooler but the PEAK temps in the combustion chamber are higher and I'm wondering if that could cause the heat into the coolant to also be higher than in a low CR engine...... and I don't know the answer.
The problem with a 95 degree sunny day is that it's a 95 degree sunny day. The sun will try to heat anything it hits.....a black surface could hit 150-160. The 95 part is a problem because heat transfer rate is set by temp differences....so if the T'stat is 180 and out side is 95 delta T is 180-95=85....but not for get the Sun heating so make the effective deltaT about 70. then say the sun goes down, and the temp drops to to 70.....now you have an effective deltaT of 115 and your cooling system will be MUCH happier..... about (115-70)/70 = 64% happier An open hood will probably help....it allows some air cooling of the engine but the bulk of the cooling is normally handled by the cooling system so how much it helps I'm not so sure. so there are some basic formulas......but when you have a specific desing question you need specific case solutions and that is often not all that basic
For those of you suffering this problem and are running an automatic transmission? Try putting the transmission into Neutral when you get to the stop light. That way the motor is not 'fighting' the fact it wants to spin the torque convertor/transmission internalas - but it prevented from dooing so because you are sitting on the brake-pedal. It works for me - and until three years ago I didn't run ANY fan on my F100. (Luckily where I am traffic delays and stop lights are few and far between but when I did visit the city the above trick got me through without overheating.)
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