After market exhaust downside?

I've been doing some reading around, and been thinking of putting a magna flow on my 4 banger for the last few months. My question, which may be stupid, will this have any long term effects on my engine, in a bad way? Just my theory is maybe a lower back pressure than it was designed for will be harder on my engine. Or am I just being protective of it and
Need to set it free? It's an 08 with 65k currently on it... Any information would be much appreciated! Thanks.

 

A Magnaflow won't hurt your engine.

I ran one on my 4 cylinder 5 speed Taco for a week...



...but put the stock muffler back on because the magnaflow resonated at 2,000 rpm which is where I drive most of the time. Opening up the exhaust also reduced the low end torque, so I was happy to go back to stock. Later, I did cut the pipe to just behind the rear axle and installed a tip. This didn't change the sound a bit, and only made the truck look a little neater.

 

I appreciate the pictures, I'm just going to have to keep searching for the right one, I mostly just don't want to lose any power from it. I've heard tons of people using the flow master 40 series with happy results. Other people say they are junk and the rot out. What was the name of the one shown in the picture?

 

the downside is the gas mileage going down due to you being throttle happy because the noise is just so sexy

 

*model of magna flow?

 

I don't think that will be an issue, even with stock I like the sound of the engine haha

 

i did too but then i got the exhaust and all hell broke loose lol

 

Hahaha well ill repost if I get the exhaust and also get pulled over!

 

You might lose some of that important back-pressure that was carefully calculated in the stock setup.

 

I had a flowmaster on my 4.0L for about 4 years.....

Aside from the slight noise in the cab (you get used to it) - the thing rusted and got holes at the joints after 4 years. I put the entire cat-back OEM setup back on.

Unless you get an entire stainless setup.... If you live in the rust belt, expect it to rust out after so many years.

 

It's a #12255 Magnaflow 18 inches long, with a 2.25 inch center opening on one side and a 2.25 offset opening on the other, similar to the stock muffler.

Your stock exhaust pipes are actually 2 3/8 diameter, but every muffler installer has a hydraulic machine that slightly expands the openings in just a few seconds to make a perfect slip fit. So if you're going to install it yourself, you'll want to get the same muffler with 2.5 openings (#12256) so you don't need to take it to someone to get the ends swedged out. Both the 12255 and 12256 have exactly the same 2.5 inch core. Just the ends are a slightly different diameter.

Greg

 

That's why I took the Magnaflow back off. The stock 2.7 exhaust is actually quite well designed for low end pull. The pipe diameter is the same as the stock 4.0 exhaust.

 

I thought after 2008 they went to 2.5" on the 4.0 trucks?

Having an 06 I can't check...... Besides I don't have the stock setup anymore and went to 3".

I can def vouch for claims about opening the exhaust system up too much while n/a can have a large effect on low end tq.
Not sure what had the biggest impact since I installed the 3" cat back, long tubes, and y pipe all at the same time, but it def altered the tq curve.... And not in a way I liked.

 

You could very well be right. I don't even have a 4.0 and just got that info from someone else here.

Greg