Hp/L...BS
12-02-2003, 08:13 AM
#32
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Originally posted by rai
What's the hp/# for the RX-8 ?
What's the hp/# for the RX-8 ?
weight....303............326...........497
power.....238 @ 8500.....240 @ 8300....405 @ 6000
hp/#......0.79...........0.74..........0.81
torque....159 @ 5500.....153 @ 7500....400 @ 4800
tq/#......0.52...........0.47..........0.80
I was able to find the RX8 engine weight. I would really like to see the '03 Cobra engine info but I was unable to find the weight anywhere.
12-02-2003, 12:18 PM
#36
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um, yeah... the weight of the engine has absolutely nothing to do with its power output. if you want to compare the power to a weight, compare it to something that maters like the car's whole weight.
12-02-2003, 12:44 PM
#37
Interesting thread. To expand on UL's post, here are a couple more ways to think about the engine design trade:
1) (As brought up by UL in other threads) Instead of specific HP, consider specific torque. As UL has mentioned elsewhere, 75 lb-ft/L seems to be about the "magic number" for high-output normally-aspirated production powerplants. The F20C is right on target at 76 lb-ft/L, while the LS6 makes about 70.
To put in perspective how difficult it is to make high specific torque, consider modern F1 engines. At 3.0L and 900 HP, they make 300 HP/L, putting any street car's specific power to shame. However, assuming the power peak is near the 19000-rpm redline, specific torque works out to only 83 lb-ft/L (or just 250 lb-ft total)! Admittedly, peak torque is surely a bit higher at lower rpms, but probably not more than 15-20% or so.
2) As UL points out above, economies of scale work in favor of larger motors. But put another way, they work *against* smaller motors. That is, given you want, say, 240 hp, what is the lightest possible package you can build to produce it? Just because you can make 400 hp with a 500-lb motor, it does not necessarily follow that you can make 240 hp with a 300-lb motor. Frankly, at 326 lbs, I think the F20C acquits itself well.
1) (As brought up by UL in other threads) Instead of specific HP, consider specific torque. As UL has mentioned elsewhere, 75 lb-ft/L seems to be about the "magic number" for high-output normally-aspirated production powerplants. The F20C is right on target at 76 lb-ft/L, while the LS6 makes about 70.
To put in perspective how difficult it is to make high specific torque, consider modern F1 engines. At 3.0L and 900 HP, they make 300 HP/L, putting any street car's specific power to shame. However, assuming the power peak is near the 19000-rpm redline, specific torque works out to only 83 lb-ft/L (or just 250 lb-ft total)! Admittedly, peak torque is surely a bit higher at lower rpms, but probably not more than 15-20% or so.
2) As UL points out above, economies of scale work in favor of larger motors. But put another way, they work *against* smaller motors. That is, given you want, say, 240 hp, what is the lightest possible package you can build to produce it? Just because you can make 400 hp with a 500-lb motor, it does not necessarily follow that you can make 240 hp with a 300-lb motor. Frankly, at 326 lbs, I think the F20C acquits itself well.
12-02-2003, 03:31 PM
#39
Well weight isn't th only consideration of the 13b Rotary engine, size is but here's a break down I found on the web.
Q. How much does the rotary weigh?
A. Weight was one of the primary reasons I chose this engine. The only thing that really counts is what the total system with re-drive, cooling systems, engine mount, etc weighs. This is called firewall forward (FWF) weight. In my case, this is about 345 pounds. From my research, it appeared to be the only auto engine available which would equal the weight, power and reliability of the O-320 or O-360 Lycoming. ANY automotive V6 piston engine will be much heavier.
Here is the breakdown of system weights in my airplane. This list is a bit out of date because it does not reflect many changes I have made (like the EFI system) but will give you a good idea of what you can expect.
Mazda 13B Engine Core 190 lbs. (incl. water pump)
Ross PSRU 37 lbs.
Starter (Toyota, geared) 10 lbs.
Alternator (Mazda 70Amp) 9 lbs.
Evaporator Cores (Qty. 2) 7 lbs. (total)
Oil Cooler (stock Mazda) 8 lbs.
Carburetors (3 Mikuni) 5 lbs. (total)
Intake Manifold 2 lbs.
Air Box 1 lb.
Coolant (7 qts.) 14 lbs.
Ignition Coil Assys. 5 lbs.
Total Engine Weight 288 lbs.
Q. How much does the rotary weigh?
A. Weight was one of the primary reasons I chose this engine. The only thing that really counts is what the total system with re-drive, cooling systems, engine mount, etc weighs. This is called firewall forward (FWF) weight. In my case, this is about 345 pounds. From my research, it appeared to be the only auto engine available which would equal the weight, power and reliability of the O-320 or O-360 Lycoming. ANY automotive V6 piston engine will be much heavier.
Here is the breakdown of system weights in my airplane. This list is a bit out of date because it does not reflect many changes I have made (like the EFI system) but will give you a good idea of what you can expect.
Mazda 13B Engine Core 190 lbs. (incl. water pump)
Ross PSRU 37 lbs.
Starter (Toyota, geared) 10 lbs.
Alternator (Mazda 70Amp) 9 lbs.
Evaporator Cores (Qty. 2) 7 lbs. (total)
Oil Cooler (stock Mazda) 8 lbs.
Carburetors (3 Mikuni) 5 lbs. (total)
Intake Manifold 2 lbs.
Air Box 1 lb.
Coolant (7 qts.) 14 lbs.
Ignition Coil Assys. 5 lbs.
Total Engine Weight 288 lbs.
12-02-2003, 05:47 PM
#40
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[QUOTE]Originally posted by AbusiveWombat
What would be really interesting would be, how would a 2.0L version of the LS6 compare to an S2000? Obviously it wouldn't see a 9000 rpm redline but it would see much more torque.
What would be really interesting would be, how would a 2.0L version of the LS6 compare to an S2000? Obviously it wouldn't see a 9000 rpm redline but it would see much more torque.