>At full power, the XR-7755 generated a tremendous amount of heat.
Speaking as a full time engine mechanic for a small chain of midwestern repair stores, this is the death-knell of every heavily customized car. Heck, 3/4ths of the engineering for a Dodge Hellcat or Mustang cobra is just to keep the thing cool enough that the driver isnt chased out of the cockpit. You cant idle them the same way you idle a Toyota...they'll burn up.
the Dodge Viper is another perfect example of engine displacement gone wild. The intercooler and radiator are massive, but the additional cylinders and their size means the V-10 motor has 10 cylinders firing onto a 90-degree crankshaft, which means it has an uneven firing interval for two of the ten cylinders. it makes the idle rougher than a garbage truck, and very prone to overheat with a 220 degree camshaft.
I'm not seeing how crank and cam specs significantly affect cooling at idle all else being equal. Any cooling system that can work under load will be fine at idle.
Edit:
For something like a race-car that's trying to minimize weight/power loss by running the minimum radiator/fan necessary and depending on airflow from movement (or rely on the fact that you're only running 1/4mi at a time) I can understand. Still, that's a cooling system sizing issue, not a cam or crank issue. A street going vehicle isn't going to have a cooling system that's sized within a hair of inadequate like that. Power output (and heat generated) at/near idle should be fairly constant regardless of cam and if it's not the higher power output cam profiles will probably have lower power output at/near idle (this depends a lot on the engine, some engines force you to choose where you want your power, some are hard to throw "too much cam" at). No matter how you cut it only so much air can get passed a closed throttle and that amount of air only corresponds to a certain amount of fuel, that puts an upper bound on heat generated at idle. I can see how adding forced induction could significantly affect heat generated at idle but even then, if everything is sized properly it shouldn't be much of an issue.
This place is really turning into Reddit where you get down-voted for questioning anyone who sounds knowledgeable.
Cars depend on air moving through the cooling system under load which means it's at speed. Cooling at idle can be a big problem for high performance cars. Going to the extreme, F1 cars have to be super careful not to overheat when stopped.
> Cooling at idle can be a big problem for high performance cars.
Or any air cooled car ever made. But the reality is that in a lot of designs, idling will test the effectiveness of the cooling system more than driving the car at speed. (Adding power only exacerbates such a problem. The OP completely fails to understand this)
It's much less of a problem than it used to be, with lots of cars including electric fans to help out the radiator, but it used to be standard to see a warning in the owner's manual about temperatures increasing in slow traffic or at idle.
They switched the 911 over to water-cooled in the late nineties, yes. Prior to that, Porsche got the idle temp problem somewhat under control using powerful electric fans positioned in front of some of the oil coolers, but there's essentially no reliable way to cool four-valve cylinder heads with a purely air-cooled engine (the 959 used separate water cooling just for the heads), so they decided the whole thing was a performance dead end. The air-cooled 911 Turbo did get up above 400hp with two-valve heads before the change, though.
> I had that fan breaking once in my Miata and temperatures went into the red really quickly in LA rush hour.
No doubt. Once you train yourself to hear that fan, you realize how much the car depends on it.
The problem is that they lost the air cooler sound. A long time ago I drove an air cooled 911 on track. It wasn't that crazy powerful (300hp) but the sound was just fantastic.
They got big and fat, too. The air-cooled cars had wheelbases similar to your Miata, but they were really pretty small compared to the modern Porsche stuff.
The new stuff is technologically stunning, of course.
True. The old 911s were really small. Now everything is way too big, including the Miata. Mine was a 2000 which was already much bigger than the original but the current ones are just way too big. That's not the point of a Miata.
It's funny, I actually admire the extent to which Mazda have managed to keep the Miata small. They're still very easy to pick out in a parking lot when viewed from above, even amidst other sports cars.
Is the extra width and weight the Miata has gained over the years down to changing safety standards? I guess on the bright side, in 2019 they're adding a little power.
Not cooling, but heat output, which the cooling system at idle cannot keep up with. As a simple example, you can retard the ignition timing enough on an otherwise sound car that the coolant will boil just sitting there idling (DAMHIK). The moral is, where the piston is at when the spark goes off makes a difference, as well which valves are opening when. Crank those knobs far enough toward the extremes, and you'll blow past the design limits of the cooling system. Yeah, your system used to be fine at idle, but now you fiddled with things. It's like the kids that throw a K&N air filter in their Civic and call it a day. No, ya idjit, you changed one thing and now you have to go change some other things to compensate. In this case, get a bigger radiator or a bigger fan.
Put another way, one does those mods to increase power output. Not all of the increased power is used to turn the wheels, a lot of it is turned to heat (just like a stock engine). More power, more heat, more cooling is required.
Powerful motors will sometimes run well enough at speed but overheat at idle. For example, after receiving an upgrade like a camshaft with more radical timings.
One key point: you can increase the size of a radiator or oil cooler but that helps a lot more when the vehicle is actually moving.
Used to have an Alfa Romeo 180 boxer engine. Made a weird ratchety noise but it was quite fun to ride. Besides the obvious overhead of multiple cam shafts, synchronization and so on, what do you think of this engine?
>What was truly unique about the cams was that there were two sets of lobes for each cylinder. One set of lobes optimized the operation of the engine valves at high power settings
VTEC, yo. In in the 1940s no less.
There's tons of tech that was well understood for WW2 aviation that finds its way back into land transportation given enough time. Adding water and alcohol blends to the intake charge to reduce temperature and prevent detonation, ABS, Fuel injection, probably other stuff as well.
A large part of these technologies making their way into consumer automobile engines was advances in material science, lubrication, manufacturing, etc, that allowed for them to exist economically and reliably. Those WW2 era piston engines were horrifically expensive, and required dozens to hundreds of hours of maintenance per hour of flight time.
Avro Lancaster, one of the two most successful heavy bombers of WW2 had 4 27litre V12 merlins, with proven reliability.
The Avro Lancastrian was a passenger variant of the Lanc and developed into the large bodied Avro York that had the range to replace a few of the old flying boat routes. Some lasted into the 60s on commercial routes.
The Lockheed Constellation had four 18 cyl radials, and being pressurised survived in commercial service even longer.
Neither had a turboprop variant.
Mass aviation was going to happen anyway whether the DH Comet arrived or not. It would have looked rather different, and perhaps not quite as endemic as now, but definitely mass aviation as we know it. Jets just hastened the process, and came at just the right time.
Mass aviation could not have happened without the turbine. The big propliners of the 50s were notorious for having engines fail in flight and had insufficient power reserves to do anything but struggle to the crash site, even with the tiny payloads they carried.
64 years ago today a KLM Constellation crashed at Shannon in Ireland, it was carrying 56 people. That's miniscule and was only sustainable with fares that the 1%ers of the era could afford. A Norwegian 737Max on a thin Atlantic route today carries 186 and that is considered borderline small.
Incidentally the Constellation did have a turboprop variant but Lockheed and GE had a disagreement and it went ahead with pistons instead as the Starliner. Few people even remember that aircraft now because of the 707.
I disagree. The desire for aviation came in thanks in part to the war, and was there with or without jets in amongst post-war growth.
Jets certainly helped the growth in size, and grew the market faster than it could have without. The market was already there and growing. Prop aircraft would have grown too had there been no jet engines, though I doubt we'd have got to 300+ capacity - but who knows?
On seating. The DH Comet had a smaller passenger capacity than the Super Constellation, which was upto 110 depending on seating configuration, though usually a bit less. The 707 had 140 when first introduced. For the 1.5% - 2%ers then?
A turboprop constellation variant was prototyped but never produced commercially. The were none in service. I think the US Navy might have ended up with a couple for trials too.
At least over here, the last significant price drop was after 2000 or so with Ryanair etc. with 737:s and A320:s. Probably a new business model in other ways as well. Single aisle, two reliable high bypass engines. There were still DC-9 derivatives flying around but no more really.
I bet you could calculate maintenance man hour per kilowatt hour for all sorts of engines.
Even the old manual flight control operations without computers meant the amount of work hours per flight was big - meaning for an ordinary worker it would not be possible.
Even if you ignore the heat and the power/weight ratio, reliability starts to become a problem. Adding more smaller piston engines improves reliability and safety in long flights.
The number of moving parts and the complexity of the piston engine compared to a gas turbine is significant.
Sometimes I think about aerial bombardment, and what that really meant during that period of conflict.
When you think about the effort to concoct the compounds for the air war, and drop them on cities, with no guidance like lasers or anything, and then you look at the sheer tonnage dropped, and how indiscriminate it really was, you wonder how aerial bombardment is at all distinguishable from chemical weapons.
It really is chemical warfare by another name. The only real difference being the explosive burning. Clean up was still a similar problem, since, as with shells, munitions would hit but not detonate. Couple this with such indiscriminate bombings that cities were engulfed in fire storms, and I think it's splitting hairs, for the most part.
The taboo against chemical warfare developed after a war that involved mass bombardment with both chemical weapons and explosives. I’m not qualified to discuss the reasons, but the people on the pointy end of the stick seem to have come away thinking that there’s a significant difference.
The reason is not complex, it’s just rarely discussed. The first time Chlorine was used it killed a lot of soldiers, because nobody had a clue what was going on and no one was equipped or trained to deal with it. By the end of the same war, chemical weapons killed very very few soldiers, because they had training, and masks. What a chemical weapon does really well is kill civilians. In particular it kills the young and old who can’t get away, who are weakest. Chemical weapons can render an area uninhabitable, one thing they’re terrible at is killing soldiers. They have MOPP suits, and training, and vehicles with filters and overpressure seals, and autoinjectors with reversal agents.
So why are chemical weapons banned? Well the talking heads like to say “they don’t work, they’re just as likely to blow back on your own troops, they’re cruel.” Really though, they do work on non-combatants. Intentionally targeting non-combatants is what’s actually illegal and discouraged. Dropping bombs to destroy a city or AA batttery while knowing that you’ll massacre civilians is seen as tacitly kosher, but just gassing the populace to the exclusion of armed manpower and armaments is very much a taboo. At least, legally and officially, although countries find ways to skirt that with defoliants, pyrophorics, nuclear weapons, etc.
People who ended up on the pointy end of that stick in the next war still didn't make it taboo, even though they did with the weapon of mass destruction made famous by that war.
I see the argument that it ultimately doesn't make much difference how a vast bunch of civilians end up indiscriminately dead, but the people who actually experienced it seem to think differently.
There's obviously a
difference because
people differentiate.
Sorry, but I'm not buying it. In exactly the same way I don't differentiate between being maimed by a flamethrower, versus being maimed by battery acid. The presumptive idea of innate wisdom of the crowd doesn't sway me.
Ask most people choose between burning their face off with a chemical or fire, and they'll likely choose fire, but getting your face burned off is categorically bad. Why distinguish.
I’m not saying they must be right. But they were there, they experienced it, and we did not. They may be wrong, but it would take a really strong argument to convince me of that. I’m going to start from the assumption that the people who experienced these weapons and came away with the belief that they should never be used again had some good reason for that.
What I really come away from the impression veterans and civilians of the time give of, is simply that it was unsporting, undignified, and unfair.
That, much more than it was punishingly cruel, in excess of death and dismemberment by other means.
They say, yeah, it's okay to zip a supersonic bullet through soft tissue such that it shreds with cavitation, and smash it through bone that splinters and explodes, so people lose whole limbs. And that's okay. It's like a deer hunt.
But hey, you don't hunt animals by mutilating their lings with bug spray. That's no fair. You wouldn't consume an elk carcass tainted with persistent organic pollutants. No fair. We can't even bury our dead.
But, you know what? You aren't going to bury your dead, when they're incinerated by high explosives.
And hey, what's fair about war at all? What's fair about several hundred planes unloading kilotons of conventional munitions, indiscriminately, to break an apparatus of geopolitics.
Gee, unfair, undignified, unsportsmanlike, in the pain, injury and slow death (leaving a contaminated corpse) department.
When you piece those explicit details together, the real problem is that it deals a degree of harm to the perception of gallantry, duty and honor of service. It's pretty much impossible to pat a chemical burn on the back, and say "there, there, thanks for defending the country" but, you can still pull that off, when sharing the room with an amputee that lost a limb to ballistics.
Exchanging chemical weapons for aerial bombardment exhibits "differences" but nothing that makes me say "wow, one is okay, and the other isn't."
Both are essentially equally bad, and neither is remotely good, or an improvement over the other.
People have their preferences, but in the same way that they rationalize the side effect of rampant smog and pollution as bad, but millions of fatal car accidents as normal, and a calculated risk.
The real choice being put on the table though, is: Would you choose between an air war that includes both regular explosions and chemical attacks, or just a regular air war only?
At that point, the choice becomes more rational. We say: "Hmmm, well, at least I can take some of the destruction out of the equation. I get to make one kind of misery go away. I can choose X = A as an alternative to X = (A + B + C). A never goes away, and nothing can be done about that, but at least I don't have to think about B and C anymore."
So, it's not about incediaries and high explosives being okay. Or aerial bombardment being different, and better. It's just that they can't be taken off the table, under any circumstances, no matter whatever else gets negotiated. I guess it's just a fundamental characteristic of destruction, that if destroying things is on the table, the basics of destruction get to keep their scalar qualities. You can limit the method of destruction but not the quantity.
It's an arbitrary distinction a lot of the time, really. But you have to draw the line somewhere. I just wish we could draw the line at eliminating all war and violence, instead of playing semantic games.
It's super bad if some bad guy destroys innocent lives with chemical weapons, but totally fine if we drone strike them. Doesn't make much sense, although in this crazy world things aren't as black and white as we'd like.
Who says it is totally fine when we drone strike them? There are reviews and large numbers of staff who do their best to minimize drone striking of innocents. Chemical weapons on the other hand are designed to maximize striking innocents.
The distinction seems to be based on the level of disability in the survivors. Dead people are not a burden after the war is over, but maimed people are, and a huge part of that is blindness. Old-style chemical weapons tended to blind people. Post-war civilian life doesn't work so well if a significant chunk of the population is blind.
It’s all well and good to examine these things while we have tjr benefit of having vanquished an enemy or enemies. Twiddling about this and whether we should bomb Hitler or Hirohito would either result in more total deaths or our defeats, neither would have been better alternatives. It’s not as if we’d go to Hitler and Hitohito and say stop killing indiscriminately in your conqured areas and we’ll stop bombing you and while you're listening, be good and surrender to us.
There's another aspect to the sheer insanity of the period that probably would be worth exploring, if only it were possible.
People were so mentally numbed and damaged by the carnage of the first world war, that the second world war was put on track by the leadership that had survived the carnage.
But looking at engines like this, and knowing that they ran on leaded AvGas, and knowing that leaded mechanization was the norm, you wonder if the psychotic leadership was actually an expression of lead poisoning from environmental factors. Just like all those crime curves that trend according to leaded gasoline bans, what if front line WWI veterans were driven psychotic by frontline exposure to heavy metals through exhaust fumes?
Rommel, IIRC, was initilly just one of those kids carrying spades as pretend arms (ok exaggerating a bit). People like him were not near a front during the first war. Hirohito’s men were in some conquest wars, but not heavy wars. So I’m not sure this applies.
Speaking as a full time engine mechanic for a small chain of midwestern repair stores, this is the death-knell of every heavily customized car. Heck, 3/4ths of the engineering for a Dodge Hellcat or Mustang cobra is just to keep the thing cool enough that the driver isnt chased out of the cockpit. You cant idle them the same way you idle a Toyota...they'll burn up.
the Dodge Viper is another perfect example of engine displacement gone wild. The intercooler and radiator are massive, but the additional cylinders and their size means the V-10 motor has 10 cylinders firing onto a 90-degree crankshaft, which means it has an uneven firing interval for two of the ten cylinders. it makes the idle rougher than a garbage truck, and very prone to overheat with a 220 degree camshaft.