Q45Tech, would you be able to help me with my two air conditioning questions:
How much horsepower does it take to drive the AC? How many CFM can the system flow?
Corey
Air Conditioning
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Q45tech
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Ib a small car with small engine AC can decrease MPG by up to 28% the Q's be affect by roughly half that or 12-14%!
By definition 12,000BTU = 1.0 HP my guess based on the injector time change is roughly 4 HP to turn the compressor at full stroke.Standard AC is 24-36,000 BTU but it depends on compressor speed:
http://www.mitsubishi-motors.c...6.pdfThe HVAC fan is fused with two 15 amps in parallel so ~~ 200 watts so the alternator adds 200/746 x1.2= 0.32 HP surely less than 5 HP combined at 60 mph. Probably 3.3-5.0 HP > 2.3 HP once temp is down to 70F.
As the temp differential drops it consumes less power.
300CFM would be a good guess at max speed with an as new clean evaporator.........ideally each of 4 main outlets would flow around 65 CFM.
More when I find it.
By definition 12,000BTU = 1.0 HP my guess based on the injector time change is roughly 4 HP to turn the compressor at full stroke.Standard AC is 24-36,000 BTU but it depends on compressor speed:
http://www.mitsubishi-motors.c...6.pdfThe HVAC fan is fused with two 15 amps in parallel so ~~ 200 watts so the alternator adds 200/746 x1.2= 0.32 HP surely less than 5 HP combined at 60 mph. Probably 3.3-5.0 HP > 2.3 HP once temp is down to 70F.
As the temp differential drops it consumes less power.
300CFM would be a good guess at max speed with an as new clean evaporator.........ideally each of 4 main outlets would flow around 65 CFM.
More when I find it.
Dennis, can't say enough about you man! Thanks.
Lets say the AC robs the engine of 5hp and blows 300 CFM of 40 degree air. The most a stock engine uses is what, 400 CFM?
I always see people trying to make the intercooler colder by using the AC. As much as that makes sense, it seams pretty complex once all's said and done. I've got something else in mind which may make an intercooler unnecessary.
Corey
Lets say the AC robs the engine of 5hp and blows 300 CFM of 40 degree air. The most a stock engine uses is what, 400 CFM?
I always see people trying to make the intercooler colder by using the AC. As much as that makes sense, it seams pretty complex once all's said and done. I've got something else in mind which may make an intercooler unnecessary.
Corey
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Q45tech
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Look up Fords Motor Company patent on using a small separate ac compressor to chill water to use with a water to air intercooler.
But is may take 15 miutes to chill 400 CF [3-4 times the passenger area internal volume] of hot air and you would use it in 45 seconds.
Actually 274/2=137 x 6,000 rpm/1728= 475 CFM @ 100% VE ~~380CFM corrected fo 80% VE.
Remember 24,000 BTU per hour is only 400 BTU per minute
# BTU/ hour = 500 (the weight of water) x GPM x Temperature Difference (delta T) :
500 x 1GPM x 50F= 25,000 BTU/HR to chill 1 gallon of waterer minute 50F from 95F to 44F!
1 BTU will heat or cool 1 pound of water 1 degree F in an hourthe thermal conductivity of water is about 23 times that of air.
But is may take 15 miutes to chill 400 CF [3-4 times the passenger area internal volume] of hot air and you would use it in 45 seconds.
Actually 274/2=137 x 6,000 rpm/1728= 475 CFM @ 100% VE ~~380CFM corrected fo 80% VE.
Remember 24,000 BTU per hour is only 400 BTU per minute
# BTU/ hour = 500 (the weight of water) x GPM x Temperature Difference (delta T) :
500 x 1GPM x 50F= 25,000 BTU/HR to chill 1 gallon of waterer minute 50F from 95F to 44F!
1 BTU will heat or cool 1 pound of water 1 degree F in an hourthe thermal conductivity of water is about 23 times that of air.
Thanks Dennis. I saw Ford's patent a couple days ago and read a bit about it... apparently there's one very similar in Japan too. As much as it seams viable, even for the home DIYer, I wouldn't want the added complexity. Then again, I'll probably be a boost monkey in a couple months and will do anything for another 5hp :rolleyes .
More questions later... gotta jetter to a bachelor's party.
Corey
More questions later... gotta jetter to a bachelor's party.
Corey
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texasoil
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Q45 tech make a strong subtle point. With tiny cars, here in hot humid Houston, A/C load is a VERY significant part of total engine (fuel) load. Toyota Prius first version was unbearable in traffic unless you forced engine to keep running at stops (turned A/C to MAX). Dropped in-town fuel economy from 45 to 25 MPG. New version has electrically driven A/C compressor and the computers figure out most economical thing shut down engine and run on battery, or keep engine running to supply electricity. Has better in town economy, but still no where NEAR that without A/C load( the advertised value).
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Notice or measure accurately over thousands of miles?
AC uses at least 2 pounds of fuel per hour ~~ 1/3 gallon per hour or so assuming it is running at maximum continuously at 60-70 mph cruise. Obviously as the variable displacement compressor reduces the stroke volume the drag declines.
8-10-12% decline on a Q depending on temperature , solar radiation, speed.
The sunload is very very accurately measured by the infra red dash sensor.
AC uses at least 2 pounds of fuel per hour ~~ 1/3 gallon per hour or so assuming it is running at maximum continuously at 60-70 mph cruise. Obviously as the variable displacement compressor reduces the stroke volume the drag declines.
8-10-12% decline on a Q depending on temperature , solar radiation, speed.
The sunload is very very accurately measured by the infra red dash sensor.
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texasoil
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'94 Infiniti Q45A
'94 Mercedes-Benz SL600
Look at it this way--the Q45 A/c system is about 40,000 BTU/hr (roughly 3.4 tons) All satisfactory auto A/C systems are sized to achieve quick 'cool-down' from a hot parked car. Interior can easily reach 130-140F. Cooling the air AND stuff down to 75F takes a lot of cooling (and horsepower). 40,000 BTU/hr takes about 5 Hp of compressor+belt loss power. Cooling fan can easily absorb another 1-2 Hp. The blower takes another 1/3 Hp
During the 'cool-down', total load of 6 HP is quite probable. That takes about 0.6 gal/hr of gasoline. At 60 MPH, geting otherwise 20 MPG, the A/C changes fuel use from 3.0 GPH to 3.6 GPH (20%) , or drops mileage fro 20 to 17 or so.
In town driving, A/C load is still constant at 0.6 GPH.Say a 15 mile trip tqkes 30 min, and otherwise is @15 MPG (reasonable). A/C load is 0.3 gal, so trip total is 1.3 gal instead of 1.0, or a 30% increase, dropping economy from 15 to 11.5 MPG.
Above scenarios all assume max cooling duty (not unusual down here in summer), and in milder climates, impact of A/C is less significant.
During the 'cool-down', total load of 6 HP is quite probable. That takes about 0.6 gal/hr of gasoline. At 60 MPH, geting otherwise 20 MPG, the A/C changes fuel use from 3.0 GPH to 3.6 GPH (20%) , or drops mileage fro 20 to 17 or so.
In town driving, A/C load is still constant at 0.6 GPH.Say a 15 mile trip tqkes 30 min, and otherwise is @15 MPG (reasonable). A/C load is 0.3 gal, so trip total is 1.3 gal instead of 1.0, or a 30% increase, dropping economy from 15 to 11.5 MPG.
Above scenarios all assume max cooling duty (not unusual down here in summer), and in milder climates, impact of A/C is less significant.
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Based on inside inlet [return] to center outlet the temp drop is around 20-22F depending on humidity ONCE the evaporator has chillled to 34F.
The system is set up to achieve no lower than 44F outlet [factory spec is 46-50F at 77F inlet at 50-60 reltive humidity] temperature before the heater door opens [slightly] to avoid evaporator freeze up...........this might take 15-30 minutes depending on car color and solar radiation and angle.
300CFM old cold air is enough for around 230 HP at 6,000 rpm......the Q consumes around 380 CFM at 70F at sealevel.
It pretty well stalls as to CFM as rpm increases to 7,000 rpm......maybe 400CFM on a perfect day.
Entropy says no free lunch: 22F cooler air would yield 2% more density which might allow 6 HP but I'll bet the system would consume more than 6 HP..........or the evaporator would be restrictive dropping air flow..............[75% efficiency would be darn good, World Class].
Remember an engine is less than 30% efficient in creating power vs fuel burned.........so burning 2% more fuel because of 2% denser air doesn't work well.
Why you heat sink a quantity of cold water to allow a 15 second burst ocassionally.
Ideally one would use 2 smaller aftercoolers [one air and one cold water] in series then run the supercharger at 8 psi to deliver a real 6-6.5 psi at plenum. The cold water would get you to 100 mph then the air flow in air to air would take over to 150 mph.
What we really need is a 2-3 speed transmission for the supercharger!
The system is set up to achieve no lower than 44F outlet [factory spec is 46-50F at 77F inlet at 50-60 reltive humidity] temperature before the heater door opens [slightly] to avoid evaporator freeze up...........this might take 15-30 minutes depending on car color and solar radiation and angle.
300CFM old cold air is enough for around 230 HP at 6,000 rpm......the Q consumes around 380 CFM at 70F at sealevel.
It pretty well stalls as to CFM as rpm increases to 7,000 rpm......maybe 400CFM on a perfect day.
Entropy says no free lunch: 22F cooler air would yield 2% more density which might allow 6 HP but I'll bet the system would consume more than 6 HP..........or the evaporator would be restrictive dropping air flow..............[75% efficiency would be darn good, World Class].
Remember an engine is less than 30% efficient in creating power vs fuel burned.........so burning 2% more fuel because of 2% denser air doesn't work well.
Why you heat sink a quantity of cold water to allow a 15 second burst ocassionally.
Ideally one would use 2 smaller aftercoolers [one air and one cold water] in series then run the supercharger at 8 psi to deliver a real 6-6.5 psi at plenum. The cold water would get you to 100 mph then the air flow in air to air would take over to 150 mph.
What we really need is a 2-3 speed transmission for the supercharger!
