Increasing Torque

[HolyEvil]

anyone have any suggestions how we N/As can increase torque for off de line useage?

cheeeeeeers

[Eug]

there's a few things you can do, some wont increase torque - but will help you get off the line quicker.

- extractors

- sensible sized exhaust

- lightened components (i.e. flywheel, tailshaft, rims, etc).

- nitrous

personally i'd go for the flywheel, thats on one of my list of things to do.

hope that helps

eug

[SKiT_R31]

there's a few things you can do, some wont increase torque - but will help you get off the line quicker.

- extractors

- sensible sized exhaust

- lightened components (i.e. flywheel, tailshaft, rims, etc).

- nitrous

personally i'd go for the flywheel, thats on one of my list of things to do.

hope that helps

eug

pfft, forgot 3L bottom end

Cams could help (if you want to sacrifice top end) Maybe a tune?

bigger (or twin) TB, more compression........

[scathing]

Stroker kit. Long stroke = torquey, low revving engine.

Increase compression. More compression = more bang per power stroke.

Shorter final drive. Pulling the gears tighter increases the tyres' tractive effort.

[HolyEvil]

hmm i've always thought that the higher the torque.. the better the off de line acceleration..

I thought longer stroke are a big no no in engine world??

how much better can off de line acceleration be if the flywheel is changed?

cheers

[scathing]

hmm i've always thought that the higher the torque.. the better the off de line acceleration..

I thought longer stroke are a big no no in engine world??

A longer stroke is a big no-no if you want an engine to rev. So if you're chasing outright power (especially with a NA engine) then you want something with a short stroke. But if you want something to pull boats or carry a family, you'd buy something with a long stroke (like those old Holden V8s)

Lots of torque is great for rolling acceleration. Off the line its good too, but cars without torque tend to be geared accordingly and can mask it a bit better. For example, I remember reading a review of a petrol powered BMW X3 vs the diesel X3. The petrol had a 0.1s advantage 0-100, but the torquey diesel was significantly faster at the in-gear 40-80 and 80-120 times.

[MBS206]

Be aware, that when you change the flywheel to a lighter component, you will start to require more throttle when climbing hills. And by more throttle, I mean a significant amount of throttle change for hills.

[scathing]

Be aware, that when you change the flywheel to a lighter component, you will start to require more throttle when climbing hills. And by more throttle, I mean a significant amount of throttle change for hills.

.............Which means you effectively have less torque in the low-end while rolling.

[Eug]

Be aware, that when you change the flywheel to a lighter component, you will start to require more throttle when climbing hills. And by more throttle, I mean a significant amount of throttle change for hills.

i dont have a lightened flywheel so i cant give my personal opinion... but i have heard otherwise... maybe a search might yield some results (i know i will when i get a spare minute)

as long as you are reasonable with the weight of the flywheel i.e. 6kg then i dont see a problem. once you start dropping down to 4.8kg flywheels then expect a significant change in driveability.

for the record i believe the standard fly is somewhere in the vicinity of 7-9kg?

[djr81]

Be aware, that when you change the flywheel to a lighter component, you will start to require more throttle when climbing hills. And by more throttle, I mean a significant amount of throttle change for hills.

Please don't take this the wrong way, but that statement is just plain wrong.

The motor will be dragging 1500kg of car up the hill. So a kilo or two in flywheel weight imakes no difference at all.

[Modena]

Bolt on a turbo

[Eug]

Bolt on a turbo

bolt on two turbos... bolt on a supercharger... dont be an idiot

[scathing]

The motor will be dragging 1500kg of car up the hill. So a kilo or two in flywheel weight imakes no difference at all.

Are you speaking from personal experience?

I am, when I say that after installing my JUN lightweight flywheel (14lbs vs the OEM 28lbs) I started having to drop down a cog on hills that I previously could traverse in top gear. Most prevalent when doing 60km/hr, since the engine's only turning over at 1500RPM or so.

In the context of the original question (off the line torque) if you're doing a hard launch a lightweight flywheel would be an advantage. The engine will rev harder.

Edited April 4, 2007 by scathing

[MBS206]

Please don't take this the wrong way, but that statement is just plain wrong.

The motor will be dragging 1500kg of car up the hill. So a kilo or two in flywheel weight imakes no difference at all.

Ah mate, the difference isn't in the weight of the car dropping, if it was, the car would accelerate better.

What the difference is, the flywheel actually stores energy.

Seriously, do some research on flywheels etc and why they're used.

A lighter flywheel can't store as much energy, hence, you need to supply more energy from the engine to go up hills.

Oh, and I'm talking from a theory point of view in studying engineering, and from a practical point of view seeing how I run a lightweight flywheel in my R33.

Hence, if you're talking from "guesstimates" and no real study or experience, STFU!

[342Four]

ive seen it

an old datto 1200 with an A14 with a lightned flywheel had to keep knocking back a cog up a certain hill otherwise it would almost stall, whereas a similar 1200 with a a12 and standard flywheel had no probs

its got to do with rotational mass, same thing with sprung vs unsprung weight on a car

add chunky bling chromes, and ur acceleration is shit

go to light forged rims - marked increase in acceleration over stock

[djr81]

Ah mate, the difference isn't in the weight of the car dropping, if it was, the car would accelerate better.

What the difference is, the flywheel actually stores energy.

Seriously, do some research on flywheels etc and why they're used.

A lighter flywheel can't store as much energy, hence, you need to supply more energy from the engine to go up hills.

Oh, and I'm talking from a theory point of view in studying engineering, and from a practical point of view seeing how I run a lightweight flywheel in my R33.

Hence, if you're talking from "guesstimates" and no real study or experience, STFU!

OK, well first things first - it is nice to be nice. So maybe it is not so polite to tell people to ^*#@ off all the time.

Secondly, it is usually an indication of someone having a lack of proof that they trot out their qualifications. So if you want to get into pissing competition about how qualified an engineer should be before making a statement then I would submit my degree from UWA & 10+ years as a practising mechanical engineer.

Now, with regard to stored energy. There are two situations we need to consider:

1. When the clutch in disengaged, ie there is no drive. In this circumstance a lighter flywheel will reduce the inertia of the motor & allow it to gain or lose revs more easilly. You notice it when you blip the throttle & also to a lesser degree when you dump the clutch. It usually makes the car more driveable except off the line.

2. When the car is being driven by the motor the motor & the flywheel are connected to a few things. Like the clutch, the gearbox, tailshaft, the diff, the halfshafts, the wheels etc etc. It is also propelling the body of the car along. So as I said the engine "sees" approx 1500kg of mass that is needs to propel. In all that a lightened flywheel makes next to no difference.

Lastly, you said

"A lighter flywheel can't store as much energy, hence, you need to supply more energy from the engine to go up hills."

Now I had thought the idea was to ACCELERATE up the hills, not just coast up them. That being the case a lightened flywheel will allow the car to accelerate that little bit faster both because of its lower mass & its lower rotational inertia. The faster you go the more energy is stored in the flywheel, so unless you are trying to get up the hill and slowing down whilst doing so you cannot recover ANY of the energy stored by the flywheel.

As an aside:

Seeing as you are an engineering student you would remenber that the energy of a rigid body in rotation is described by the equation:

T=05xIxwxw. (read as Tee eqauls half I omega squared)

So lets assume our new flywheel is 80% of the rotational inertia of the heavier,older one. It means you need an extra 826 rpm (ie an increase of 7000 to 7826rpm) to store an equivalent amount of energy in the flywheel. Unfortunately you will also be storing much more energy in the crank, pistons, conrods, cams, pumps, drives etc etc. So the difference in stored energy is more likely to be down near a couple of hundred rpm.

[Eug]

ohh it gets all juicey and technical... nice!

here's what a few minutes searching came up with:

http://www.skylinesaustralia.com/forums/in...t&p=2475963

http://www.skylinesaustralia.com/forums/in...=102395&hl=

http://www.skylinesaustralia.com/forums/in...st&p=886217

http://www.skylinesaustralia.com/forums/in...t&p=1191873

seems like all positive results.

[MBS206]

djr, seriously, have you put a lightened flywheel in your car, and taken it for a drive.

I have, the change is ENORMOUS!

Acceleration IS affected when going up the hills.

If you haven't physically put a lightened flywheel, in your car, and taken it for a drive back to back to compare, then don't spout that I'm wrong. I HAVE a lightened 5KG Chrome Moly flywheel IN my car RIGHT NOW. And you need a fair amount of throttle to get it up a hill, compared to running a stock flywheel.

And in 5th gear, a change in 786RPM, approx is a change in 30km/h.

So trying to get the same amount of energy up there, in that flywheel, you need to be running 30km/h faster. That's a fair wack more speed needed, even if you take into account everything else like pistons etc.

It is proven, day in, day out, in race cars, road cars, all the way through history, the lighter flywheel will be able to accelerate, unmassed alot more quickly, BUT, it will also SLOW a lot more quickly.

A larger flywheel, requires more energy to get moving, but once at that RPM, it takes a fair bit more energy to slow down that flywheel.

And your 1500KG of weight your trying to PULL, is different to the flywheel you're trying to turn.

And if you want to attempt to prove me wrong, firstly go fit a light weight flywheel to your car and you'll find that it isin fact correct what I've said.

And within regard to the other message, that was a mixture of bad day + being annoyed with people who've never actually attempted any of this stuff talking from "thought". So I do have to apologise there.

I know, I sound agro in some of this, but me = tired, and I'm not trying to be, just difference is I've ran lightened flywheel, and have physically experienced it.

[Eug]

just throwing an idea out there...

but i dare say the effects of a lightened flywheel would be different from turbo to NA applications... no?

[djr81]

djr, seriously, have you put a lightened flywheel in your car, and taken it for a drive.

I have, the change is ENORMOUS!

Acceleration IS affected when going up the hills.

If you haven't physically put a lightened flywheel, in your car, and taken it for a drive back to back to compare, then don't spout that I'm wrong. I HAVE a lightened 5KG Chrome Moly flywheel IN my car RIGHT NOW. And you need a fair amount of throttle to get it up a hill, compared to running a stock flywheel.

And in 5th gear, a change in 786RPM, approx is a change in 30km/h.

So trying to get the same amount of energy up there, in that flywheel, you need to be running 30km/h faster. That's a fair wack more speed needed, even if you take into account everything else like pistons etc.

It is proven, day in, day out, in race cars, road cars, all the way through history, the lighter flywheel will be able to accelerate, unmassed alot more quickly, BUT, it will also SLOW a lot more quickly.

A larger flywheel, requires more energy to get moving, but once at that RPM, it takes a fair bit more energy to slow down that flywheel.

And your 1500KG of weight your trying to PULL, is different to the flywheel you're trying to turn.

And if you want to attempt to prove me wrong, firstly go fit a light weight flywheel to your car and you'll find that it isin fact correct what I've said.

And within regard to the other message, that was a mixture of bad day + being annoyed with people who've never actually attempted any of this stuff talking from "thought". So I do have to apologise there.

I know, I sound agro in some of this, but me = tired, and I'm not trying to be, just difference is I've ran lightened flywheel, and have physically experienced it.

I will try to explain why I disagree with you. Please don't crack the sh!ts if some of it sounds condescending, but I guess other people may read it also.

Anyway we have basically two forms of energy of motion.

Potential energy.

Kinetic energy.

Now potential energy is simply energy stored by gaining height. It is equal to mass times height times gravity. ie E=mgh.

Believe it or not we can largely ignore it, but we wont.

Kinetic energy is the energy stored in motion of a moving body. For a linear case (ie straight line) it is equal to half the mass times the velocity squared. For a rotational case it is equal to half the moment of rotational inertia times the angular velocity squared. As you can see the linear & angular equations are expressed in a very similar way - basically because they are very similar equations & are derived the same way.

Now to our case of going up a hill.

Assume we are in 4th gear going, say 100km/h. We go 10 metres up the hill (vertically) & accelerate to 110km/h going from 3000rpm to 3100rpm at the same time. The numbers aren't particularly important, but they make it easier to understand. So what happens to our three types of energy?

Well if we go up 10 metres we gain 10 metres worth of potential energy. So 1500kg times 10 metres times 9.81 which is the gravitational constant. So that increases by whatever the sum works out to be.

What happens to our linear kinetic energy?

We have gone from 100 km/h to 110km/h. So we now have 0.5 times 1500 times (110 squared - 100 squared). Technically it should be expressed as metres per second, not km/h but I am not going to work it out, so it doesn't matter.

We have a gain in linear kinetic energy because we are now going faster.

What happens to out rotational kinetic energy?

We have gone from (say) 3000rpm to 3100rpm. So we now have 0.5 times the rotational inertia of the whole drivetrain times (3100 squared - 3000 squared). Again angular velocity should be measured in radians per second but I am not going to do the sum. We have a gain in rotational kinetic energy.

This energy is provided by the power of the motor, obviously. This will equal the potential energy gain + the linear kinetic energy gain + the rotational kinetic energy gain + whatever frictional losses we have (eg aero drag etc)

So how does a lightened flywheel effect the three sums?

Potential energy. Well the gain in potential energy is slightly less because the mass is less.

Linear kinetic energy. Well the gain in linear kinetic energy is slightly less because the mass is less.

Rotational kinetic energy. The gain here is less because the rotational inertia is slightly less.

What does this mean?

Simply that the car with the lightened flywheel needs less power to accelerate up a hill than the same car with a heavier flywheel. Less power = less throttle.

Why it may feel different.

Simply because as you said when you drop rpm on the motor (eg when you launch) there is less rotational kinetic energy to turn into linear kinetic energy. So the motor feels more "gutless" on launch. Which is where I think alot of people get a bit confused.

Lastly.

My new car is due to be unloaded Monday. When it gets to the workshop I am going to fit a lightened flywheel - and use less throttle getting up the hills around home!