How do I explain max horsepower and torque to a Honda owner?
10-14-2003, 02:15 PM
#16
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There are certainly a huge amount of the FnF ricer crowd around but there is also a large dedicated amount of people who are very performance oriented.
Now it depends on the honda motor and its level of prep, but you would be surprized how much they can get out of those little things (even NA). a well prepped b18c5 (ITR) engine will have a redline upwards of 9K and have well more than 200 whp. recently I've seen a very nicely preped SOHC 1.6L put down 181 whp at around 8600. Honda engines are probably the best mass-produced engines period. You can beat the snot out of them and rev them all day long. They are torqueless wonders, but in the hands of the right driver they can be very quick around a roadcourse.
given a huge budget a race team (like realtime) can get ungodly numbers out of the new K series (RSX)...like 250 whp naturally aspirated. Their redline is probably something ridiculous like 10.5K.
Now, I used to own a 944S and have driven a bunch of hybrid civics, most of them would pull on the '44 top end.
Now it depends on the honda motor and its level of prep, but you would be surprized how much they can get out of those little things (even NA). a well prepped b18c5 (ITR) engine will have a redline upwards of 9K and have well more than 200 whp. recently I've seen a very nicely preped SOHC 1.6L put down 181 whp at around 8600. Honda engines are probably the best mass-produced engines period. You can beat the snot out of them and rev them all day long. They are torqueless wonders, but in the hands of the right driver they can be very quick around a roadcourse.
given a huge budget a race team (like realtime) can get ungodly numbers out of the new K series (RSX)...like 250 whp naturally aspirated. Their redline is probably something ridiculous like 10.5K.
Now, I used to own a 944S and have driven a bunch of hybrid civics, most of them would pull on the '44 top end.
10-14-2003, 02:26 PM
#17
I'd stop trying to expalin it to them. If they are not getting it. Don't kill yourself trying.
However, using Car and Driver's data, the Civic Si makes 132lb. ft. at 5000 with a redline at 6800rpms.
At peak torque the hamster under the hood is making 125hp (132x5000/5252=125). IF it holds that torque to redline (and it won't) it would end up with 170 hp. The peak hp is 160 so that must be made at about 6000 rpms depending on torque at that rpm.
The drivers of such cars should be shifting at about 6200 rpms (600 below redline) so that the engine will drop near peak torque.
However, using Car and Driver's data, the Civic Si makes 132lb. ft. at 5000 with a redline at 6800rpms.
At peak torque the hamster under the hood is making 125hp (132x5000/5252=125). IF it holds that torque to redline (and it won't) it would end up with 170 hp. The peak hp is 160 so that must be made at about 6000 rpms depending on torque at that rpm.
The drivers of such cars should be shifting at about 6200 rpms (600 below redline) so that the engine will drop near peak torque.
10-14-2003, 02:35 PM
#18
Three Wheelin'
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I saw so many innacuracies, I had to step in.
Torque is analagous to force in rotational mechanics. It is the dot product of a force being applied at a point on a rotating body and the distance from that point to the rotational axis.
More torque at your tires allows them to push the earth back with a stronger force, giving you better acceleration.
Torque is vaguely proportional to the displacement of the engine (except in the case of turbos).
Power is energy produced (or consumed) per unit of time. Friction and air resistance will bleed off a certain amount of energy (as heat, vibration, etc.) per unit of time, slowing the car, so unless the power being produced is greater that the power being drained, the vehicle's kinetic energy will drop. Kinetic energy is equal to half the mass times the square of the velocity, so when kinetic energy drops, velocity drops.
As a related side note power must quadruple for speed to double. And that's ignoring internal and external resistances. Air resistance goes up with the square of velocity as well. Both of these are reasons why you have to add so much power to increase top speed by minimal amounts.
As for the honda. Explain to the guy that honda engines need to be in the upper rpm range to produce good power (I have an Acura, so I experience it first hand). But that's not because of physics, it's because of VTEC. At higher RPM ratings, the engine starts taking in more air and fuel, so it gets more power and torque, at a cost of fuel economy.
Torque is analagous to force in rotational mechanics. It is the dot product of a force being applied at a point on a rotating body and the distance from that point to the rotational axis.
More torque at your tires allows them to push the earth back with a stronger force, giving you better acceleration.
Torque is vaguely proportional to the displacement of the engine (except in the case of turbos).
Power is energy produced (or consumed) per unit of time. Friction and air resistance will bleed off a certain amount of energy (as heat, vibration, etc.) per unit of time, slowing the car, so unless the power being produced is greater that the power being drained, the vehicle's kinetic energy will drop. Kinetic energy is equal to half the mass times the square of the velocity, so when kinetic energy drops, velocity drops.
As a related side note power must quadruple for speed to double. And that's ignoring internal and external resistances. Air resistance goes up with the square of velocity as well. Both of these are reasons why you have to add so much power to increase top speed by minimal amounts.
As for the honda. Explain to the guy that honda engines need to be in the upper rpm range to produce good power (I have an Acura, so I experience it first hand). But that's not because of physics, it's because of VTEC. At higher RPM ratings, the engine starts taking in more air and fuel, so it gets more power and torque, at a cost of fuel economy.
Last edited by Ag951; 10-14-2003 at 04:53 PM.
10-14-2003, 02:42 PM
#20
Drifting
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Your reference to Civics not being useful over 4000 is off. Seeing as most of those things only make like 90 ft lbs of torque max, they HAVE to rev that high to get their horsepower. So essentially they only become useFUL after 5000+ rpms. Look at the S2k. 110 ft lbs of torque but 250 hp, and look how high the thing revs. To like 9500 rpms or some dizzying number. I drove one of those and you have to be upwards of 6 grand to have the thing move at all. Once you do though it's pretty quick...I still would never pay for one.
10-14-2003, 02:46 PM
#21
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944S Boyeee,
You do have to rev most Honda engines quite high to get maximum performance out of them. If a motor produces peak horsepower around 7.5k rpms (like most stock Honda's) then for maximum acceleration, you should rev to at least a little over that before shifting. Then when you shift it will drop you from ~8k rpms to ~6k rpms. This will be below the peak horse power but not to far below it because you waited till after the peak horse power rpm to shift.
BTW: Getting into arguments on subjects you are not knowledgeable about is not a good idea. It is much better to engage in a discussion of the subjects pro's and con's to develop a better understanding of it. This way even if you do not know very many pro's or con's the conversation can still be productive and both parties can leave the discussion wiser. But what do I know most of the time I talk to "Ricers" the conversation last about 1 minute before I say "yep your right" and walk away. This is mainly due to the fact that many do not want more knowledge about cars they want to prove the size of their phallus.
John
You do have to rev most Honda engines quite high to get maximum performance out of them. If a motor produces peak horsepower around 7.5k rpms (like most stock Honda's) then for maximum acceleration, you should rev to at least a little over that before shifting. Then when you shift it will drop you from ~8k rpms to ~6k rpms. This will be below the peak horse power but not to far below it because you waited till after the peak horse power rpm to shift.
BTW: Getting into arguments on subjects you are not knowledgeable about is not a good idea. It is much better to engage in a discussion of the subjects pro's and con's to develop a better understanding of it. This way even if you do not know very many pro's or con's the conversation can still be productive and both parties can leave the discussion wiser. But what do I know most of the time I talk to "Ricers" the conversation last about 1 minute before I say "yep your right" and walk away. This is mainly due to the fact that many do not want more knowledge about cars they want to prove the size of their phallus.
John
10-14-2003, 03:08 PM
#22
Three Wheelin'
One little detail that people are leaving out of the equation is gearing. The transmission and final drive act as torque multipliers, so if you have a higher-revving engine you can apply a larger torque multiplier (lower gearing) and achive similar torque to the ground. This is why a Honda S2000 with only 110 ft-lbs of torque but a 9,000 rpm HP peak is about as fast as a 951S with 263 ft-lbs of torque at 4,000 rpm. This is also why horsepower is a better comparison for performance than torque. Otherwise my brother's 1,500 ft-lbs (Cat diesel) would blow away my 951.
Extreme examples are modern 600 CC sports bikes. No torque at all below 8,000 rpm, measured in in-lbs above 8,000 rpm. However, with 110 HP at 13,000 rpm they are FAST!
Of course, all of this refers to driving in the power band, as discussed above. A Honda S2000 would probably be a pain around town, but a 944S2 would be better than either an S2000 or a 951.
Extreme examples are modern 600 CC sports bikes. No torque at all below 8,000 rpm, measured in in-lbs above 8,000 rpm. However, with 110 HP at 13,000 rpm they are FAST!
Of course, all of this refers to driving in the power band, as discussed above. A Honda S2000 would probably be a pain around town, but a 944S2 would be better than either an S2000 or a 951.
10-14-2003, 03:54 PM
#23
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Originally posted by 944S Boyeee
I made the mistake of saying that I thought most Civics would be useless over 4000 RPM (I know, that was too low). Now they all hate me!!!
But what RPM SHOULD a Civic driver be shifting at for optimal performance?
What do these things redline at?
Jeff (944S Boyeee)
I made the mistake of saying that I thought most Civics would be useless over 4000 RPM (I know, that was too low). Now they all hate me!!!
But what RPM SHOULD a Civic driver be shifting at for optimal performance?
What do these things redline at?
Jeff (944S Boyeee)
10-14-2003, 04:28 PM
#24
Horsepower sells motor cars.
Torque wins motor races.
Two cars producing 200hp max. can be very, very different cars. The most important thing to look at would be the torque/ horsepower curves. Where does the power come in, how linear is it, etc. An engine that produces say 90-110 HP until 6k RPM's and then spikes to 200 HP is going to behave a lot differently than something with a nice, flat torque curve that grows nicely as the revs climb.
Torque wins motor races.
Two cars producing 200hp max. can be very, very different cars. The most important thing to look at would be the torque/ horsepower curves. Where does the power come in, how linear is it, etc. An engine that produces say 90-110 HP until 6k RPM's and then spikes to 200 HP is going to behave a lot differently than something with a nice, flat torque curve that grows nicely as the revs climb.
10-14-2003, 04:38 PM
#25
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---- What rpm should a civic driver shift at? What do these things redline at? ---
For what its worth, this summer I converted my daughter's 2000 Civic Si to forced induction (supercharged). The stock engine produced about 170hp (at the flywheel -- figure 17% loss at the wheels?) at around 7800 rpm, and just under 100lb-ft of torque right around 3000 rpm. With the supercharger, it produced about 230hp (again, at the flywheel) and a little better than 125 lb-ft of torque (torque curve flattened, max torque moved to around 6800 rpm).
The vtec shift point was just above 5,500 rpm -- and the engine really doesn't start breathing until then.
That particular engine has a very short stroke; so low torque, but capable of sustained high rpm, sort of like the 4cyl honda bike engines.
It redlines at 8000 rpm, which (along with top speed) is limited by the ECU, but max rpm can be safely/reliably raised to 8300 rpm or more.
When you're really running one out, you're shifting right at the redline, and working to keep it above the vtec shift point at 5,500 rpm as you shift.
Again, for what its worth, my personal experience is that nearly every car I've rebuilt/built has its charms -- whether its a 61 mg midget, a 67 chevy impala, a 68 firebird, 72mgb, a 2000 civic, or even an '83 harley. Thank goodness, they're all different, all special!
I just got a 944 -- am am just starting to work with it. I can't wait for it to reveal its secrets!!
I really enjoy this forum, by the way.
Tom
I can't wait to
For what its worth, this summer I converted my daughter's 2000 Civic Si to forced induction (supercharged). The stock engine produced about 170hp (at the flywheel -- figure 17% loss at the wheels?) at around 7800 rpm, and just under 100lb-ft of torque right around 3000 rpm. With the supercharger, it produced about 230hp (again, at the flywheel) and a little better than 125 lb-ft of torque (torque curve flattened, max torque moved to around 6800 rpm).
The vtec shift point was just above 5,500 rpm -- and the engine really doesn't start breathing until then.
That particular engine has a very short stroke; so low torque, but capable of sustained high rpm, sort of like the 4cyl honda bike engines.
It redlines at 8000 rpm, which (along with top speed) is limited by the ECU, but max rpm can be safely/reliably raised to 8300 rpm or more.
When you're really running one out, you're shifting right at the redline, and working to keep it above the vtec shift point at 5,500 rpm as you shift.
Again, for what its worth, my personal experience is that nearly every car I've rebuilt/built has its charms -- whether its a 61 mg midget, a 67 chevy impala, a 68 firebird, 72mgb, a 2000 civic, or even an '83 harley. Thank goodness, they're all different, all special!
I just got a 944 -- am am just starting to work with it. I can't wait for it to reveal its secrets!!
I really enjoy this forum, by the way.
Tom
I can't wait to
10-14-2003, 04:59 PM
#26
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the simplest way to tell when to shift is to attach a small weight suspended by thread to the rearview mirror. as you accelerate the weight should move back and once you notice that the weight is starting to move forward again, shift. that way you should be in the part of the rpms which has the most tq and hp.
10-14-2003, 05:05 PM
#27
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Originally posted by Sami951
No clue about "normal" Civics, but the Type-R (do you call it that over there, or is it something else?) doesn't start moving until it hits 6000rpms... then it pulls to around 8k, fun, but in a weird way
No clue about "normal" Civics, but the Type-R (do you call it that over there, or is it something else?) doesn't start moving until it hits 6000rpms... then it pulls to around 8k, fun, but in a weird way
On most honda/acura motors the VTEC point is in the mid 5000s, so you can get good fuel economy for most of your driving, but get the power when you rev it high, for spirited driving.
Here is a dyno for an Acura RSX-S with an injen intake. You can see the VTEC point at 5600RPM.
Here is an S2000. The VTEC point is not as dramatic.
If you do a 4000RPM launch (and my RSX-S can launch at 4k on Falken Azenis with minimal tire spin), you can hit VTEC quickly. And if you shift at 8400RPM or higher, you'll still be in VTEC when you get to the next gear.
10-14-2003, 05:36 PM
#29
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testock,
I am very amused that you supercharged your daughter's Si. Did she even ask for it? Also, in case you don't know, you can get VTECH controllers that let you lower the RPM in which the VTECH engages, Could help a lot, though fuel efficiency would be at a loss.
~Eyal
I am very amused that you supercharged your daughter's Si. Did she even ask for it? Also, in case you don't know, you can get VTECH controllers that let you lower the RPM in which the VTECH engages, Could help a lot, though fuel efficiency would be at a loss.
~Eyal
10-14-2003, 05:51 PM
#30
Welcome to Rennlist Testock, it is a nicely disfunctional community, you will like it.
As this thread shows, tech is kinda slippery here, but there are a lot of guys who have the knowledge to help with the 944 series questions you are sure to have. What part of Phoenix are you in?
Based upon some of the responses to the thread here, the differences between torque and HP are about as well understood as the difference between alchemy and chemistry.
But it helps to think about the engines themselves, at least I find it helpful. On a 1.5L engine, the combustion chambers are pretty small, almost exactly the same size as a Coke can. This limits the size of the explosion you can set off, (unless you increase the amount of air and fuel you compress into the space).
Small explosion=low torque=high RPM to do work effectively.
An 8.1L GM engine has more than a 1L Coke bottle per cylinder, meaning that each firing generates as much power as 2 of our cylinders, or 3 of a Honda 1.5L engine. Which is just a guess on my part.
Still have to give props to Honda.
http://www.sebringmiata.com/page66.html
sorry, its long but cool as ****.
As this thread shows, tech is kinda slippery here, but there are a lot of guys who have the knowledge to help with the 944 series questions you are sure to have. What part of Phoenix are you in?
Based upon some of the responses to the thread here, the differences between torque and HP are about as well understood as the difference between alchemy and chemistry.
But it helps to think about the engines themselves, at least I find it helpful. On a 1.5L engine, the combustion chambers are pretty small, almost exactly the same size as a Coke can. This limits the size of the explosion you can set off, (unless you increase the amount of air and fuel you compress into the space).
Small explosion=low torque=high RPM to do work effectively.
An 8.1L GM engine has more than a 1L Coke bottle per cylinder, meaning that each firing generates as much power as 2 of our cylinders, or 3 of a Honda 1.5L engine. Which is just a guess on my part.
Still have to give props to Honda.
Engine Standard Formula One Formula One
Year 1986 1987 1989
Size 1.5 litre 1.5 litre 1.5 litre
Cylinders 4 6 6
Aspiration normal turbo turbo
Maximum Boost - 58 psi 36.3 psi
Maximum Fuel - 200 litres 150 litres
Fuel 91 RON 102 RON 102 RON
Horsepower @ rpm 92 @ 6000 994 @ 12000 610 @ 12500
Torque (lb-ft @ rpm) 89 @ 4500 490 @ 9750 280 @ 10000
The details of the transition from Standard to Formula 1, without
considering engine materials, are:-
1. Replace the exhaust system. HP and torque both climb to 100.
2. Double the rpm while improving breathing, you now have 200hp
but still only about 100lb-ft of torque.
3. Boost it to 58psi - which equals four such engines, so you have
1000hp and 500lb-ft of torque.
Simple?, not with 102 RON fuel, the engine/fuel combination would knock
the engine into pieces, so....
4. Lower the compression ratio to 7.4:1, and the higher rpm is a
big advantage - there is much less time for the end gases to
ignite and cause detonation.
5. Optimise engine design. 80 degree bank angles V for aerodynamic
reasons, and go to six cylinders = V-6
6. Cool the air. The compression of 70F air at 14.7psi to 72.7psi
raises its temperature to 377F. The turbos churn the air, and
although they are about 75% efficient, the air is now at 479F.
The huge intercoolers could reduce the air to 97F, but that
was too low to properly vaporise the fuel.
7. Bypass the intercoolers to maintain 104F.
8. Change the air-fuel ratio to 23% richer than stoichiometric
to reduce combustion temperature.
9. Change to 84:16 toluene/heptane fuel - which complies with the
102 RON requirement, but is harder to vaporise.
10.Add sophisticated electronic timing and engine management controls
to ensure reliable combustion with no detonation.
You now have a six-cylinder, 1.5 litre, 1000hp Honda Civic.
For subsequent years the restrictions were even more severe, 150 litres
and 36.3 maximum boost, in a still vain attempt to give the 3 litre,
normally-aspirated engines a chance. Obviously Honda took advantage
of the reduced boost by increasing CR to 9.4:1, and only going to 15%
rich air-fuel ratio. They then developed an economy mode that involved
heating the liquid fuel to 180F to improve vaporisation, and increased
the air temp to 158F, and leaned out the air-fuel ratio to just 2% rich.
The engine output dropped to 610hp @ 12,500 ( from 685hp @ 12,500 and
about 312 lbs-ft of torque @ 10,000 rpm ), but 32% of the energy in
the fuel was converted to mechanical work. The engine still had crisp
throttle response, and still beat the normally aspirated engines that
did not have the fuel limitation. So turbos were banned. No other
F1 racing engine has ever come close to converting 32% of the fuel
energy into work [136].
Year 1986 1987 1989
Size 1.5 litre 1.5 litre 1.5 litre
Cylinders 4 6 6
Aspiration normal turbo turbo
Maximum Boost - 58 psi 36.3 psi
Maximum Fuel - 200 litres 150 litres
Fuel 91 RON 102 RON 102 RON
Horsepower @ rpm 92 @ 6000 994 @ 12000 610 @ 12500
Torque (lb-ft @ rpm) 89 @ 4500 490 @ 9750 280 @ 10000
The details of the transition from Standard to Formula 1, without
considering engine materials, are:-
1. Replace the exhaust system. HP and torque both climb to 100.
2. Double the rpm while improving breathing, you now have 200hp
but still only about 100lb-ft of torque.
3. Boost it to 58psi - which equals four such engines, so you have
1000hp and 500lb-ft of torque.
Simple?, not with 102 RON fuel, the engine/fuel combination would knock
the engine into pieces, so....
4. Lower the compression ratio to 7.4:1, and the higher rpm is a
big advantage - there is much less time for the end gases to
ignite and cause detonation.
5. Optimise engine design. 80 degree bank angles V for aerodynamic
reasons, and go to six cylinders = V-6
6. Cool the air. The compression of 70F air at 14.7psi to 72.7psi
raises its temperature to 377F. The turbos churn the air, and
although they are about 75% efficient, the air is now at 479F.
The huge intercoolers could reduce the air to 97F, but that
was too low to properly vaporise the fuel.
7. Bypass the intercoolers to maintain 104F.
8. Change the air-fuel ratio to 23% richer than stoichiometric
to reduce combustion temperature.
9. Change to 84:16 toluene/heptane fuel - which complies with the
102 RON requirement, but is harder to vaporise.
10.Add sophisticated electronic timing and engine management controls
to ensure reliable combustion with no detonation.
You now have a six-cylinder, 1.5 litre, 1000hp Honda Civic.
For subsequent years the restrictions were even more severe, 150 litres
and 36.3 maximum boost, in a still vain attempt to give the 3 litre,
normally-aspirated engines a chance. Obviously Honda took advantage
of the reduced boost by increasing CR to 9.4:1, and only going to 15%
rich air-fuel ratio. They then developed an economy mode that involved
heating the liquid fuel to 180F to improve vaporisation, and increased
the air temp to 158F, and leaned out the air-fuel ratio to just 2% rich.
The engine output dropped to 610hp @ 12,500 ( from 685hp @ 12,500 and
about 312 lbs-ft of torque @ 10,000 rpm ), but 32% of the energy in
the fuel was converted to mechanical work. The engine still had crisp
throttle response, and still beat the normally aspirated engines that
did not have the fuel limitation. So turbos were banned. No other
F1 racing engine has ever come close to converting 32% of the fuel
energy into work [136].
sorry, its long but cool as ****.