trd6209

I have been looking at the exhaust system that Downey Offroad offers on their website and I was curious as to whether or not anyone has had any experience with this. I am referring the 4WD HIGH PERFORMANCE 2 ½" EXHAUST SYSTEM, with Cat that they offer for $340.00.


I have also noted that a lot of you guys have been talking of reducing the pipes from the catback to 2 1/4 from 2 1/2 stock. How much improvement could I stand to gain by doing this?

SoCal4Running

We were going to get the Downey exhaust, and in fact it was on order till we found out that it was going to take 2 months to get it.

So we had it done locally for 1/2 the cost with the muffler of our choice.

Rugby10

Are you are asking about an exhaust diameter REDUCTION = Better performance? I just want to clarify as I have always thought that the reverse is true.

BTW - I'm moving to Tucson on the First of July, maybe we could meet up.

SoCal4Running

By having a smaller diameter pipe you create some backpressure which helps make torque.

Larger pipes belong on bigger motors that see extended high rpm use where you dont need/want back pressure

AznSky

it depends, the whole point of reducing the diamater would be to create more back pressure, with FI vehicles you would want to force out more gas so that's why a greater diamater exit = better performance. However there are some cases where backpressure is good too. I'm not an expert on this so I will let the pros explain.

Corey

iTrader: (1)

http://www.dynomax.com/techsupport.stm

On a 3.0 V6 I used 2.25" as recommended by the chart below.
To big of pipe you hurt low end performance, but gain top end.

Big pipes belong on rigs that see a need for high speed.
4x4s going to be going slow on trails need low end torque.
Smaller pipes are favored here.

SoCal4Running

Backpressure is a very good thing for smaller motors. Its all about TORQUE.

Rugby10

Thanks for clearing that up guys.

trd6209

That sounds good. Shoot me an email with your number when you get settled in and I will give you a call.

trd6209

I think that's the way that I will go. Thanks for the info.

trd6209

So what did you go with for the muffler? I see some guys go with the Flowmaster 40 series and some go with the 50 series. I need to do research to find out what I need.

Also did you drop in a High flow CAT or stick with the standard? Just curious. This is all pretty new to me since I am just getting into the whole thing.

jksuperstar

If you're aiming for backpressure, why pay the $$ for hi-flo parts?

bulldog-yota

exhaust systems are similar to inlet systems, it is not about the diameter but creating the right air/gas speed for the right application. That's why lots of manufacturers today have dual or multitrack inlet systems, to create the right flow and air velocity. This principal also applies to the exhaust system, although it is less sensitive (easier to push a gas out than suck it in)

a very simple way of experiencing why different sizes of engines, and different performance categories (normal vs racing, etc) require different diameters, is do the following. Get pipes from 1/4" to about 3" in diameter and at least 3 feet long. Now take a deap breath and blow through each pipe. WHich once could you create the best sense of exhaling quickly and with some force, was it the biggest one? Nope probably somewhere in the middle. Now imagine doing this a couple of thousand times a minute to simulate cylinders of on engine.

Thats why tuners spend huge amounts of time on a flow bench for heads, inlet and exhaust systems.

SoCal4Running

I didnt get a Flowmaster at all, its too "poser" out here in sothern california. I had a Dynomax Superturbo installed, its far quieter than a Flowmaster and doesnt draw attention from the wrong people.

As for the cat we didnt change it because the one in the truck is newer and was 2 1/4 to match the rest of the system.