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I supported Toymods
Location:
Perth
Registered:
May 2002
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 Torque building..
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Thu, 07 November 2002 01:47
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Just curious, apart from the obvious increasing of displacement, are there any other ways to increase the torque of an engine?
Also excluding raising the compression ratio cos its a turbo engine.
Thanks,
Nathan
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Location:
Adelaide
Registered:
May 2002
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Re: Torque building..
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Thu, 07 November 2002 02:15
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As torque is a function of cylinder pressure, the way to increase torque is to stuff it with more air.
And/Or
Have the air (+ fuel, of course) burn at a slightly earlier piston location (advance ignition) so it expands while the cylinder is at higher compression (yet more pressure) thus ramming it down harder (torqueing the crankshaft)
The problem with torque building is when you get to the upper limits for a given engine combination/configuration.... knock, knock, knock 
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Location:
West Aust
Registered:
October 2002
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Registered:
June 2002
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Re: Torque building..
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Thu, 07 November 2002 03:03
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Boost!!
But that almost counts as raising the compression.
As rex said, advance the timing, but this leads to detonation city if your running high boost also, so then you'll have to look at 1. Using higher octane fuel (or additves ie.methanol 10%)
or 2.Water injection (which you can also mix with methnol).
The down fall of stroking an engine is they don't like to rev as much, you usually end up with a crappy rod ratio.
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Location:
Adelaide
Registered:
May 2002
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Re: Torque building..
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Thu, 07 November 2002 04:34
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Stroking will increase torque but in a differnt way.
Increasing stroke produces increased leverage against the crank. While this is good for strong bottom end. Remember that because the pistons are travelling further they are also tarvelling at a much higher acceleration and deceleration speeds/rates. This greatly increases stress on internal components. The result is a far less rev-happy engine.
as ae101 said, increasing runner length. this increases air speed into the engine which helps to fill the cylinder better (more air = more torque).
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Location:
Ulladulla
Registered:
October 2002
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Re: Torque building..
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Thu, 07 November 2002 05:47
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My Rover heads have got narrow but tall ports, and stock valve sizes (Dont know them off hand).
The little cow revs off its nut and makes 530nm @ the wheels @ 3300 RPM.
Maybe a good head port job or even talk to someone who knows thier stuff when it comes to cams can help.
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I supported Toymods
Location:
Brisbane, QLD
Registered:
May 2002
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Re: Torque building..
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Thu, 07 November 2002 11:29
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First off all, since you mentioned that this is a turbo motor,
to the best of my knowledge, the intake runner technique will not be of significant use.
Basically, what a longer intake runner achieves is known as intertial supercharging. If your engine breathes a certain amount of air per combustion cycle, by having a longer intake runner, the air will have to travel faster (to get to the combustion chamber) and thus, will create a greater inertia in the air flow. Due to the greater inertia of the airflow, there will be a natural supercharging effect (basically, the inertia of the airflow will fill more air into the cylinder, than it would had the airflow been slower, and in any case, more than what the just pressure difference, i.e. the vacuum would dictate), raising the volumetric efficiency of the engine, inturn producing more torque (more air/fuel combusted, hence more chemical energy converted to mechanical energy, which manifests as torque). However, at higher rpms, due to the lower valve openning times and higher breathing requirements of the engine (per unit time), long intake runners of relatively small cross section can be insufficient to provide the required air and therefore, would result in lower volumetric efficiency of the engine and hence, less torque.
One thing that I must mention is that the whole torque versus horsepower arguement. Horsepower is a direct linear function of the torque generated per revolution and the engine rpm (ignoring mechanical and other losses). So how come an engine make more horsepower at the top end of the rp band even with the torque beinf reduced? simple, higher rpm. Had the volumetric efficiency of the engine being maintained at peak (where peak torque occurs), you would have a flat torque curve and even higher high rpm horsepower.
Increasing the stroke increases the torque (longer stroke converts more mechanical power into torque, but the pistons would travel a longer distance), and would result in a more toquey, but lower reving engine. You can neither create nor
destroy energy (and in case of an engine, you can't escape the thermodynamic laws that govern the power generation) and hence, by creating a longer stroke, you are reducing piston velocity and thus reducing the revability of the engine. What this means is that even though you'd have more torque, you'd have an rpm limited engine. The problem with an rpm limited engine is that at higher rpm, even with reduced volumetric efficiency, you can generate power and by increasing the stroke, you'd reduce that ability. The other thing is, loner the stroke, more time it will take for the engine to rev-up (hence the 1JZ-GTE reving up faster than the 2JZ-GTE).
As the others said, stuffing more air into the cylinder (higher boost pressure) is the reasonable way to increase torque in your case (and maybe increase the bore, but that is increasing displacement). But yes, detonation and mechanical stress at high rpm's is an issue that would need to be addressed. Advancing the ignition timing and higher octane rating fuel would increase the torque through more chemical energy and more thorough complete combustion process.
Another thing that could possibly help you is sequential fire injection (to get a more homogenized mixture of air and fuel) and porting the head so that you could achieve the best possible airflow characterestics (making your turbo charging effort more efficient). It must be noted that the highest cfm flow bench approach does not necessarily translate into the most appropriate airflow characteristics.
Hope this helps... Just my two cents... Please correct me if I am wrong.
Cheers
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Torque building..
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Thu, 07 November 2002 11:58
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methanol/water injection an easy way of managing detonation with advanced timing and over compression. hook a black box and relay up to a knock sensor, and run that sucker through your intake.
a) cools the caharge, reducing predetonation
b) increases octane, improving detonation characteristic (slower burn)
cheers
ed
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