how would i go about upgrading the torque on an acura rsx or a toyota celica?

If u mean increasing the amount of Torque.
In general (you can tune super/turbochargers to give what u want)
Supercharger (for more low end torque)
Turbocharger (for more high end torque)
TwinTurbo etc.
N/A (doesn't give much torque, only HP).

What would be most cost efficient? How do supercharger and turbocharger differ?

N/A - gains HP through:
1 - compression ratio
2 - air flow
3 - oil-cooling, air cooling

typical parts: racing cams, cold air intake, high flow exhaust, spark plugs, valve springs, high flow headers. MASSIVE weight reduction (e.g. take out A/C).
there are other parts, hopefully someone else will add to this list

Honda engines are all N/A, S2000, is a prime example the orignial S2000 had 9000 redline.

Turbos work by channeling exhaust to a turbine that forces more air into ur engine.
Note: Exhaust only turns the turbine. the turbine forces air from the intake into ur engine. The air ususally goes through an intercooler (cools the air, cooler air = more air since density is higher).

Supercharge , same as turbo, but instead of exhaust channeling the turbo, it uses the engine RPM (similar to the A/C using the timebelt to connect to the engine)

RSX and Celica are both N/A engine cars. but if u want TORQUE...
I think you should see if there are super/turbo charge kits for those cars.
try going on rsx/celica forums.

KEEP in mind that (if u drive manual) u probably have to replace ur clutch and other componements to handle the power.

Dont put a turbo on a rsx :'( You will have the same car but with a tremendous "kick" up in redline that will make you car more dificult to control.

If you want to stay N/A, the only way to significantly increase your torque is to bore/stroke your engine (i.e. bigger displacement).

If you don't care about N/A the best choice would either be a turbo- or a supercharger.

These are all expensive silly answers, play around with your cam duration and lift, you'll lose hp but gain torque if done well not much lost. Azu, N/A engines can give all kinds of hp and torque different levels, idiot. Jim, for torque you stroke your engine ie increase capacity down, if you bore out your engine (increase your capacity sideways across for bigger pistons) you'll lose a small amount of torque and gain hp.

If you bore your engine and keep the same stroke, you'll still have bigger displacement ==> more torque
(I think...)

And btw, playing with cams will increase your torque only moderately (not more than 10%, I believe). You want to drastically increase torque (like 40-50+%) use a turbo, or swap the engine!

Ok, turbos work at HIGH REVS when there is enough gasflow to spin them which means they will improve top end performance ie. horsepower. Torque is gained at low revs so something that will give immediate power is what you want ie. supercharger. Cam lift and duration cn do amazing things to an engines power, i wouldn't trust statistics.
Now how stroking works is quite simple. When the piston has to travel further it carrys more energy up and down so theres your torque. But the problem is its still getting blasted with the same force so therefore it will take longer to go from top to bottom ie. less revs flat out.
Thank you and goodnight, try the chicken.

Longer stroke = longer piston rod

Torque = (force) x (distance)

When you stroke the engine, the force remains the same (force is a function of how much fuel is injected into the cylinder, which is a function of how much you press the gas) BUT the distance is longer, therefore you have more torque.

Well, force might also be affected because of the slightly bigger displacement (again, more fuel injected).

I have done my physics class, thank you.

Now about turbos and stuff...
Turbos basically slam more air into the cylinder, which means that more fuel is injected (the ECU controls all that stuff), therefore --> more power (significantly)
THEREFORE, MORE TORQUE.

Horsepower = (Torque) x (engine speed)

Now you have a point that the gain is mostly in high revs, but if you use a small turbo, you will also have significant gain in low revs. The guy was asking for torque, he didn't mention if he wanted it in low or high revs.

Longer stroke = longer piston rod

Torque = (force) x (distance)

When you stroke the engine, the force remains the same (force is a function of how much fuel is injected into the cylinder, which is a function of how much you press the gas) BUT the distance is longer, therefore you have more torque.

Well, force might also be affected because of the slightly bigger displacement (again, more fuel injected).
Boring an engine takes away torque, it doesn't give it. Now turbos work at high revs where the engine isnt using torque so wouldn't it be smarter if you wanted torque to get something that boosted peak torque.

1. Boring? I was talking about stroking.

2. Most engines have their peak torque at high revs anyways (like 4000). What are you trying to say? I don't understand you. The engine gives torque throughout the whole rpm range...

Sorry, im very tierd its like 12:07 here. Anyway more fuel cant be injected unless you play with your jets, we're just talking about increasing displacement so when you stroke it has no effect on the heads.
2.Engines that give peak torque at 4000 would be pretty rev happy which most engines are not, i take it the good doctor doesn't have a performance car or he wouldnt be asking us. The engine gives horsepower throughout the whole rpm range as well but we don't really use ultra low end horsepower that much do we. You don't need to wait a hell of a long time to get peak torque, at least alot less than horsepower and torque is what gets you moving so i'd rather have it down low thanks.

Yes, I'd rather have it down low, but I'd have it up high as well. Anyway...

Btw, most new N/A engines make peak torque anywhere between 3000-4500 rpm. Make a search and you'll see for yourself (it's all about emissions and stuff...)
For example, my engine in the golf is a 1.6 N/A and makes peak torque at around 4000 rpm, if not more. And the redline is at 6500.

Increasing displacement offers slightly more power and torque, but its generally quite an expensive option and not worth it. As said, Turbo-Charging is usually the best way to go, but u can also considering putting in a revised inlet maifold and lighter camshafts, this offers about 15% of the engines toque.

Just get a super, you have torque where you want it, its MUCH more reliable and no lag giving much better low end and similer high end torque.
And 4000 is still well shy of 6500 so my point stands.

I still think that a very well worked out turbocharger set-up is better than a super-. Anyway that is slightly off-topic.