improving power to torque ratio.

[zevans]

You could un-port it a bit which would give you torque at the expense of power, does that help?

(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?

[Warthog]

Yes it makes things clear. Thank You.

[J.j.]

Is a car with a lighter flywheel more difficult to drive then??

[sdminus]

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

[Evo6extreme]

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.

[J.j.]

it would be more difficult to launch well...

Understand the stopping bit, but not the above....  :confused:
Cheers

[Oedipus Rex]

I\'m guessing that when you engage the clutch you are going to lose a lot of revs.

guessing here though.

[rxv8]

v8=torque :rollin

thats a good option...

[nikp]

Originally posted by rxv8
v8=torque :rollin

thats a good option...

Plus a couple of turbo\'s bolted on! :p

[zevans]

Originally 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?

[zevans]

Originally posted by rxv8
v8=torque :rollin

thats a good option...

Skoda Fabia vRS = torque but it ain\'t a sports engine!

[rxv8]

so are you saying a v8 cant hold its own against a sports engined vechile...:rollin

[J.j.]

Big thanks for that zevans.

[Spotlamp]

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

[zevans]

Originally 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!