How come G37 torque is low?
12-10-2007, 07:48 PM
#16
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Well put Kahboom. I know you and I have discussed gear ratios to death elsewhere but since your post focused so much on the engine's characteristics, I felt the need to reinforce that gearing is VITAL to the performance of the car.
Thus we need to consider all of that together, since you don't drive the engine, you drive the car. It's pretty complex and thus we use things like 0-60, 0-150 and 1/4 mile numbers to guage performance.
I guess what I'm saying in the context of this thread is let's not judge a car by any one component -- especially something like a peak torque number.
Thus we need to consider all of that together, since you don't drive the engine, you drive the car. It's pretty complex and thus we use things like 0-60, 0-150 and 1/4 mile numbers to guage performance.
I guess what I'm saying in the context of this thread is let's not judge a car by any one component -- especially something like a peak torque number.
12-10-2007, 08:40 PM
#18
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Well put Kahboom. I know you and I have discussed gear ratios to death elsewhere but since your post focused so much on the engine's characteristics, I felt the need to reinforce that gearing is VITAL to the performance of the car.
Thus we need to consider all of that together, since you don't drive the engine, you drive the car. It's pretty complex and thus we use things like 0-60, 0-150 and 1/4 mile numbers to guage performance.
I guess what I'm saying in the context of this thread is let's not judge a car by any one component -- especially something like a peak torque number.
Thus we need to consider all of that together, since you don't drive the engine, you drive the car. It's pretty complex and thus we use things like 0-60, 0-150 and 1/4 mile numbers to guage performance.
I guess what I'm saying in the context of this thread is let's not judge a car by any one component -- especially something like a peak torque number.
12-11-2007, 12:18 AM
#19
Well put Kahboom. I know you and I have discussed gear ratios to death elsewhere but since your post focused so much on the engine's characteristics, I felt the need to reinforce that gearing is VITAL to the performance of the car.
Thus we need to consider all of that together, since you don't drive the engine, you drive the car. It's pretty complex and thus we use things like 0-60, 0-150 and 1/4 mile numbers to guage performance.
I guess what I'm saying in the context of this thread is let's not judge a car by any one component -- especially something like a peak torque number.
Thus we need to consider all of that together, since you don't drive the engine, you drive the car. It's pretty complex and thus we use things like 0-60, 0-150 and 1/4 mile numbers to guage performance.
I guess what I'm saying in the context of this thread is let's not judge a car by any one component -- especially something like a peak torque number.
01-03-2009, 03:17 PM
#20
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The new VQ revs several hundred rpm's higher than the old VQ. From Power = 1/5252*torque*rpm, you see that power is proportional to rpm. The increase from 298hp (or what ever it was) to 330 is due to the increased redline. Using the real numbers you get: Power = 1/5252*(270ft-lbs*7500rpm) = 385.6hp, which is 55hp more than the G is advertised to make. Maybe 270ft-lbs is indicated torque (the torque produced in the cylinder and before any parasidic losses are applied), but I think its a brake number. I'll have to do some digging and see where the discrepancy is? Can anyone help me out here? I'll drag out some of my old engineering books and see if I can figure this out.
01-03-2009, 08:58 PM
#21
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The new VQ revs several hundred rpm's higher than the old VQ. From Power = 1/5252*torque*rpm, you see that power is proportional to rpm. The increase from 298hp (or what ever it was) to 330 is due to the increased redline. Using the real numbers you get: Power = 1/5252*(270ft-lbs*7500rpm) = 385.6hp, which is 55hp more than the G is advertised to make. Maybe 270ft-lbs is indicated torque (the torque produced in the cylinder and before any parasidic losses are applied), but I think its a brake number. I'll have to do some digging and see where the discrepancy is? Can anyone help me out here? I'll drag out some of my old engineering books and see if I can figure this out.
with 7500rpm torque will be much lower
it will be like this
1/5252*2??ft-lbs*7500rpm = 330hp
01-03-2009, 10:47 PM
#22
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Ah, yeah exactly. I remember this now. Your not taking torque max and redlline numbers. If you look at a lug curve (torque curve) and look at the end of the curve close to redline rpm, you should see that torque is decreasing less than a 45 degree angel. The point at which the curve decreases more than than 45 degrees is your max power. This point is max power because torque is decreasing at a faster rate then rpm is increasing, hence you have reached max power (since power = 1/5252*torque*rpm). Hope this makes sense.
01-04-2009, 12:44 AM
#23
Torque is a function of displacement.
1.0L displacement is about 75 ft/lbs of torque on any N/A engine.
Try looking up everything from corollas, civics, accords, M3s, Ferraris, porsches, etc.
Any NA engine will do roughly 75 ft/lbs of torque.
Turbos/superchargers change things.
1.0L displacement is about 75 ft/lbs of torque on any N/A engine.
Try looking up everything from corollas, civics, accords, M3s, Ferraris, porsches, etc.
Any NA engine will do roughly 75 ft/lbs of torque.
Turbos/superchargers change things.
01-04-2009, 01:03 AM
#24
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Your thinking to BMEP or brake mean effictive pressure. BMEP is a ROUGH was to compare apples to apples when considering outputs of (for example) a B16A2 and a VQ37. BMEP is the mean pressure that if applied to the top of a piston from top to bottom (stroke) would produce the given brake torque of the engine. BMEP is only theoretical and DOES NOT represent actual cylinder pressures. Its only a formula used for comparison (like Volumetric Efficiency). Torque is not a function of displacement. Torque = Force x Distance, which basically means the longer the crank throw (distance from the crank journal center to the crank centerline) the more torque you create.
01-08-2009, 08:03 PM
#26
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Hmmm.. torque AT THE WHEELS is acceleration. Since the engine's output is channeled through a transmission that multiplies the torque, the gear ratio becomes important when considering a car's acceleration. The shorter the gear ratio, the more the torque is multiplied and the faster the input has to turn. Since horsepower, as you stated, is directly related to RPM (in fact, describes the engine's relationship of torque to RPM), horsepower is an important component of the acceleration of a car.
Short version: Very high rpm == lots of torque multiplication at the wheels == fast car, given reasonable torque numbers. Real world example: Formula 1 race car, <200lb/ft torque, 19,000rpm redline, 800HP, 0-100-0 in <5s, top speed about 230mph, nurburgring time < 6min.
Short version: Very high rpm == lots of torque multiplication at the wheels == fast car, given reasonable torque numbers. Real world example: Formula 1 race car, <200lb/ft torque, 19,000rpm redline, 800HP, 0-100-0 in <5s, top speed about 230mph, nurburgring time < 6min.
01-09-2009, 02:32 AM
#27
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Torque multiplication is dependant upon gear ration, NOT rpm. If you had a F1 car run wide open at 19,000 this in no way necessarily means its multiplying torque. When you talk about "overdrive" in an transmission what you are really saying it its output shaft is turning faster than its input shaft. In this instance torque is low and IS NOT mutliplied. Torque is ONLY mutliplied when you are running a ratio lower than a 1:1, beyond that output torque is lower than input torque. If your in first gear you have lots of torque (torque multiplication), but no speed. Conversely, if your running in 6th gear you have to down shift to climb a steep hill. You clearly see torque and speed are INVERSELY proportional and torque is independant upon rpm.
Point being -- the higher the revs the shorter the gears can be, which means more torque at the wheels through multiplication. While you are (of course) stating facts, unless the car in question is rolling on quarter-sized wheels or is traveling at hundreds (thousands?) of MPH, a high rpm is going to mean a shorter gear ratio is in play. Especially when we are using the example of a 19,000 rpm F1 car.
01-09-2009, 12:41 PM
#28
Your thinking to BMEP or brake mean effictive pressure. BMEP is a ROUGH was to compare apples to apples when considering outputs of (for example) a B16A2 and a VQ37. BMEP is the mean pressure that if applied to the top of a piston from top to bottom (stroke) would produce the given brake torque of the engine. BMEP is only theoretical and DOES NOT represent actual cylinder pressures. Its only a formula used for comparison (like Volumetric Efficiency). Torque is not a function of displacement. Torque = Force x Distance, which basically means the longer the crank throw (distance from the crank journal center to the crank centerline) the more torque you create.
force = bore, and distance = stroke.
Force x distance = torque
Bore x stroke = displacement.
Very crude, I know, but it does work...
01-09-2009, 01:59 PM
#29
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LOLs I dunno what size wheels you are thinking of, but when I think about normal cars running engines turning at 19,000 rpm, I think that better be some f-ing short gear ratios!
Point being -- the higher the revs the shorter the gears can be, which means more torque at the wheels through multiplication. While you are (of course) stating facts, unless the car in question is rolling on quarter-sized wheels or is traveling at hundreds (thousands?) of MPH, a high rpm is going to mean a shorter gear ratio is in play. Especially when we are using the example of a 19,000 rpm F1 car.
Point being -- the higher the revs the shorter the gears can be, which means more torque at the wheels through multiplication. While you are (of course) stating facts, unless the car in question is rolling on quarter-sized wheels or is traveling at hundreds (thousands?) of MPH, a high rpm is going to mean a shorter gear ratio is in play. Especially when we are using the example of a 19,000 rpm F1 car.
The reason an F1 cars engines is built to turn those kinds of rpm's is because the cars travel road courses and are constantly in the corners, and having such a high rpm allows for a super broad power band, thus the need for shifting is greatly reduced.
01-09-2009, 02:09 PM
#30
This is a great thread, shows how useful myg37.com can be - simple question that could have been blown off with quick answers was instead delved into with a lot of thought and educated speculations. Much thanks to the "Kahboom & Mal_TX" fountain of knowledge. I know I learned a lot. Thanks guyz!