Question on more torque... Options

[dabazied]

Well this actually there are two diff questions I have.

First, does anyone know how to get some more torque and low-end power out of this thing to where it will still be semi cost effective and not a total pain in the a**? I know I have the st and it is slow. I don't wanna turbo it because I'm still doing my homework on doing either the all too common 3sgte swap or a v6 swap n adding a turbo to that. I was just wondering if there was anything I can do for some more low end power.


Also, has anyone tried doing the custom gears to get the car less than 3500 rpm @ 80 mph, or anything else that has worked(i.e., new tranny that'll bolt up with the 7afe engine ....) because it's really annoying to have my car going that high in rpms when highway driving, especially when I wanna pass someone I still need to drop to 3rd or 4th to actually get it to go lol

I've been looking around on here for answers to these questions but haven't really been too successful. The first question is prob total newb question, but I am not going to deny that title lol.

Thanks guys.... and gals.

[Bitter]

search around a little

[DaveQB]

This has me curious as well. although I am no "revhead", I am curious for a little more power out of my '99 Celica.

bump

[GTS13]

As you well know, there isn't a lot to do with an ST, but so far after my tune-up, header, and exhaust my ST is pretty peppy. After all my suspension mods it makes a pretty funny daily driver. If I wanna really pass someone I still have to drop to 4th most of the time but I can do so rather quickly. Just put an aftermarket clutch on there and do all the normal mods and that should keep you happy until you finish your homework. Also, as far as being cost effective...do as much of it yourself as you can.
Good luck.

[frosty]

nothing to my knowlegde would be cost effective for the 7a.

Right off, if you really need to do something before you start your turbo project, do like gts13 said and get a header. I suggest a larger throttle body for better response.

[Bitter]

timing advance!

[Rusty]

this from celicatech

Gutted cats by definiton are not smooth -- and having a section of your exhaust pipe widen and then neck back down is a guarantee for backpressure.

That said, backpressure is bad. No, it does not help deliver torque. Basic logic -- backpressure means exhaust gases do not easily escape the combustion chamber. Burnt fuel and oxygen-poor air do not improve combustion. Exhaust gas in the combustion chamber is bad for performance.

If we could build exhaust systems with zero backpressure at all RPMs -- in other words, for all volumes of gas flow -- we'd improve performance.

Unfortunately, we don't have exhaust systems capable of changing their flow capacity as the amount of exhaust created changes. So we pick a compromise size.

This is where the myth of backpressure being necessary for torque or acceleration or throttle response comes from. Larger pipes have greater flow capacity, and therefore seemingly will generate less backpressure. Strapping larger pipes onto an engine reduces its response at lower RPMs, which is when torque is felt.

Funny thing is, bigger pipes mean more backpressure at lower RPMs. It's actually the reverse of the myth. Bigger pipes give the exhaust gases room to expand, which means they cool down -- and temperature is another way of measuring kinetic energy, which is to say the exhaust gas slows down. Cooler gases do not flow as well as hot gases (just as icy water does not flow as well as hot water). Now you've got a mass of slow-moving exhaust gases sitting in the pipe, with the engine trying to cram hotter, faster moving exhaust gas out of the combustion chamber. The cooler exhaust gases impede the ability to remove exhaust gases from the combustion chamber, and therefore foul the mix resulting in less efficient combustion.

Having to pick one exhaust pipe size means you are picking a system which is most efficient at only one RPM number -- it is efficient when producing X amount of exhaust, but not X+Y or X-Y.

Smaller pipes are going to be most efficient at low RMPs, when torque is emphasized, because they are better matched to the volume of exhaust produced. Bigger pipes moves the efficiency point up the RPM dial. For the same reason, engines using turbos or nitrous oxide need larger pipes -- they squeeze in more air per cycle and produce more exhaust gases at the same RPM as their naturally aspirated brethern.

The short of it is, torque is not maintained by restricting your engine. The way to get the most out of the car is to figure out at what RPM you'll spend the most time, and match the exhaust pipe to that level of exhaust output. That said, short of FI, 2.25" is about as large as you'd want to go on the 5SFE.

[TRD_GT]

Are larger throttle bodies available for the celicas? i didnt know that, where can u get them from..?

[frosty]

Are larger throttle bodies available for the celicas? i didnt know that, where can u get them from..?

As far as I know, no.

I know some buy mustang tbs' and a smigde of custom fitting. Not really a huge problem. (this being done by those who have a 3sgte, I see no reason for it to not work with our 5s/7as' ...anyone?)