Aviation’s Largest Piston Engine (2016)
tested.com
Aviation’s Largest Piston Engine (2016)
1–10 of 51 posts
Re: Aviation’s Largest Piston Engine (2016)
#2>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.
Re: Aviation’s Largest Piston Engine (2016)
#3>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.
Re: Aviation’s Largest Piston Engine (2016)
#4>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...th…
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.
Re: Aviation’s Largest Piston Engine (2016)
#5Sometimes 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.
Re: Aviation’s Largest Piston Engine (2016)
#6>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…
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.
Re: Aviation’s Largest Piston Engine (2016)
#7Sometimes 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 real…
Yeah now we do really better using surgical strikes on afghan weddings.
God bless america.
Re: Aviation’s Largest Piston Engine (2016)
#8Sometimes 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 real…
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.
Re: Aviation’s Largest Piston Engine (2016)
#9>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...th…
Take the hood off, bring a cooler of ice water, don't get stuck in traffic, stop every 10-15 minutes to cool off. Problem solved.
Re: Aviation’s Largest Piston Engine (2016)
#10>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...th…
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, tha…
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.