I\'m not too happy with my power to torque ratio. I\'m running about 350 at the fly, maybe a bit higher, but my torque peaks around 240-250lbs. Is there any way to increase the power to torque ratio on a car?
Power and torque are directly linked, power is calculated from the Torque multiplied by the angular velocity in Radians per second.
It all stems back to basic physics with workdone being a function of force, distance and time.
so its the same steps you will take to raise the hp in that section of the curve that will net you more torque low down.
so unless you are god and able to change the laws of physics you can\'t change the torque to power ratio :D
QuoteOriginally posted by MikeLMR
Power and torque are directly linked, power is calculated from the Torque multiplied by the angular velocity in Radians per second.
It all stems back to basic physics with workdone being a function of force, distance and time.
so its the same steps you will take to raise the hp in that section of the curve that will net you more torque low down.
so unless you are god and able to change the laws of physics you can\'t change the torque to power ratio :D
yeah I realise this but you will see two cars (two FD\'s even) with the same power output but totally different torque outputs.
What I want to know is why?
suppose its all down to how well the turbocharger and engine work together. Also a ported engine will make more power off boost and will also spool a turbo quicker vs an unported engine etc. etc. it really is very difficult to put an exact reason on it.
QuoteOriginally posted by MikeLMR
suppose its all down to how well the turbocharger and engine work together. Also a ported engine will make more power off boost and will also spool a turbo quicker vs an unported engine etc. etc. it really is very difficult to put an exact reason on it.
OK so at that point I have to conclude that I can increase my torque without increasing my top end power output. For instance If I can get my turbo up to pressure quicker I will see an increase in torque but probably not in the top end of my power, as at the top torque tails off bu power continues to rise.. So how about porting the wastegate?
the wastegate should not be open until you hit your boost limit. So porting it will make no difference at all as it is only there to control the boost by bypassing the turbine.
Theres far too many variables to give a concise answer ... you may get more low down torque with a better map ? who knows ?
also the torque peaking and then falling off towards the red line is normal, I think its all to do with getting the mixture in and out in an ever decreasing amount of time (I *think*) + even on a turbocharged engine it will have a peak where the inlet and exhaust harmonics work best to fill the chambers. The reason you still make power while the torque drops is because your engine is delivering less force but in a much shorter space of time so the power rises as long as the torqe doesn\'t drop faster than the rpm\'s rise.
I\'m sure lots of other factors affect it too. I\'m a little out of my depth when it comes to this stuff ...
What "out of your depth" that was great to read, thank you:)
Now why do you loose torque when you fit a lightened fly wheel but make revs faster?:wave
you don\'t loose torque you loose momentum on the engine side of the drivetrain which makes engaging the clutch more interesting as the engine will decelerate quicker if you don\'t get it right.
I am definetly out of my depth :D I can remember some of the facts but tend to fill in the blanks using common sense ... works some of the time ... but not always :o
I like things that you can take back to first principals and work out that way. its suprising what you can make sense of if you think of it that way.
Now you have lost meeeeeeeeeeeeeeeeeeeeeee:confused:
its difficult to explain but the flywheel does not consume energy (we are talking text book theory world here ... don\'t want to get really complicated!) it just stores it. The lighter the flywheel the less \'capacity\' it has for storing that energy.
so the reason an engine accelerates quicker with a light flywheel is the flywheel is storing less energy so the engine will have more energy to accelerate other things and itself.
Well that hit the spot. You do have a way with words, very good, thank you. Do you teach or is it a natural gift.:burnout :3gears-lh :3gears-lh :3gears-rh
QuoteOriginally posted by MikeLMR
also the torque peaking and then falling off towards the red line is normal,
Yeah I realise that, that was kinda my point.
The fact that BHP keeps increasing, to the redline but torque falls, surely means I should be able to get an increase in torque by increasing the speed in which the power is delivered, but not necessarily increase the actual top end power of the car. Therefore giving me more torque but not more power.
QuoteWell that hit the spot. You do have a way with words, very good, thank you. Do you teach or is it a natural gift
LoL no :D
I am more likely to be the one being taught than teaching ... just signed up for an engineering degree (or will have once I fill out the forms)
QuoteOriginally posted by Oedipus Rex
Yeah I realise that, that was kinda my point.
The fact that BHP keeps increasing, to the redline but torque falls, surely means I should be able to get an increase in torque by increasing the speed in which the power is delivered, but not necessarily increase the actual top end power of the car. Therefore giving me more torque but not more power.
yes if you improve the efficiency lower down but not at the redline you can change the low down torque and power but not alter the peak. so it is possible.
You could un-port it a bit which would give you torque at the expense of power, does that help? :D
(The amount of overlap is very relevant to low-rpm torque, which is why some cars based on that primitive piston technology have two sets of cams so it\'s torquey in the middle and powerful up the top. As does the Renesis, in effect, because the aux ports don\'t open until 5500 revs)
The map and timing affects it too...
A likkle turbo will be more responsive which effectively boosts torque but it can\'t supply enough air at high revs, so peak power, and the point where it arrives, will both drop with a smaller turbo. (Which is why the 7 has two of different sizes, so it\'s got a lotta torque everywhere....)
Moving the point where peak power arrives upwards at the expense of torque is sometimes good because you can gear it shorter. The 8\'s engine has bugger all torque anywhere but because peak power is 8200 you can gear it like a bike, so the engine delivers POWER and REVS and the gearbox turns it into TORQUE.
The key thing to remember is that it\'s torque at the rear wheels that makes the car go, and to get it there it has to go through the drivetrain. This means you can use the drivetrain to trade off between torque and engine speed, but it also means changes in it will affect the way that torque actually gets to the wheels. A lighter flywheel means the engine does what you tell it with the throttle, instantly, whereas in most cars there\'s a bit of delay between changing throttle and actually getting more or less shove. So, if you are climbing a hill you need to anticipate and give it a bit more throttle - with a standard flywheel you get a bit more of a chance to do that because the momentum of the flywheel will keep the engine revving even if there\'s something trying to slow it down. Does that make sense?
Yes it makes things clear. Thank You.:)
Is a car with a lighter flywheel more difficult to drive then??
it would be more difficult to launch well... it will have less reciprical ( If thats spelt correct) mass. Ie it will decrease in speed faster due to its lesser mass.
Its a bit like standing in front of a train and trying to stop it and standing in front of a bike.
The train being the stock heavy fly and bike being the light one
Scott
I hope i am correct LOL
One way to boost torque is to increase the capacity of the engine, ie with a piston engine fitting a stroker kit will boost torque but not necessarily power.
Quoteit would be more difficult to launch well...
Understand the stopping bit, but not the above.... :confused:
Cheers
I\'m guessing that when you engage the clutch you are going to lose a lot of revs.
guessing here though.
v8=torque :rollin
thats a good option...
QuoteOriginally posted by rxv8
v8=torque :rollin
thats a good option...
Plus a couple of turbo\'s bolted on! :p
QuoteOriginally posted by J.j.
Is a car with a lighter flywheel more difficult to drive then??
Yes. Depending on the take-up of the clutch and the inertia of the car itself it can be a sod. Usually though you only go 10s of percent lighter and the car is still quite heavy, so keeping the inertia going is OK.
The problem is engine speed and road speed tend to match themselves more quickly - when launching, your road speed is zero and your engine speed is, I dunno, 20 mph, and there\'s nothing except your left foot controlling how much the one can slip against the other! If you make a mistake with a heavy flywheel the engine revs will drop quickly but not immediately and you can stop a stall by feathering clutch and/or throttle, but with a light flywheel the revs drop even quicker and you get less time to see the launch problem coming and prevent it!
Same if you cock up a downchange or you\'re riding the clutch...
The advantage, apart from response, is just the opposite - your brain is doing the work and your brain is generally cleverer than a flywheel. (Except maybe in Si\'s case :p )
Upshifts are quicker because revs take less time to drop to the new gear and downshifts are easier because a smaller blip will give you more revs, and not only that, the throttle controls engine speed more directly. (I CAN revmatch in the TDI but i have to stamp on the throttle like you\'re doing an emergency stop!)
Can someone FAQ this up? :D
QuoteOriginally posted by rxv8
v8=torque :rollin
thats a good option...
Skoda Fabia vRS = torque but it ain\'t a sports engine!
so are you saying a v8 cant hold its own against a sports engined vechile...:rollin
Big thanks for that zevans.
This is a really great post, been an interesting, if not confusing, read.
I think the point with rotaries, there\'s a lot less flexibility in managing torque and bhp over a piston engine. Just coz they\'re so simple, whereas a piston you\'ve got more flexibility over stroke, bore and compression as well as the obvious porting characteristics.
A point worth noting is that a 13b has two sets of ports as it were, to deliver low down and mid range torque as well as big power. I guess you may be able to increase torque (at the cost of top end power) by matching the secondary ports to the primary ones (this is just a guess btw ;) ) but why you\'d want to do that god only knows. Caravaning perhaps :rollin
H
QuoteOriginally posted by rxv8
so are you saying a v8 cant hold its own against a sports engined vechile...:rollin
Prolly think of some muscle cars with slower times than a 7 (or prolly slower even than a Cosmo) ;)
Peak torque is not the whole story, that\'s the point, but neither is peak power.
(And a V8 is heavy so in terms of power-to-weight... )
I think spotlamp has put it in a nutshell there - there\'s less bits in a rotary, which also means there\'s less to fiddle with!