Ok guys here is the question....................

Ive got a 3.0 with everything stock, intake-air filter, all of it.
I just had a Flowmaster 50 Series muffler and Car Sound High-Flow cat with 2.25" exhaust pipes connecting all of it.
NO Headers or anything.

So here it is, has anyone experienced a loss in low end torgue with a similar set-up.
Im not sure if Im nuts or what-but it feels like I lost power in the low end from idle to about 3000 rpm????

The high end is better and the Runner will get to 4000 rpm much quicker, which is ok- but I wanted low end.
I'm thinking that the motor has lost too much back pressure, and therefore low end torque. Perhaps due to the high-flow cat?
Any ideas?

Aside from that the Flow is to loud for me, and I need a suggestion on a quieter muffler- not silent- but quieter?

 

Well, I know there are these places that have silencers for sale. Probably at a local car performance or customs shop they'd have them. That's all I can tell you though about it. A friend of mine told me about it once because he thought mine was too loud, but I like the loud throatiness of my exhust, except when I'm trying to talk to the girl in the passenger seat...:pat:

Zach

 

i lost low-end too, i think most have.

 

Ryan- you only did the cat back right?

The Dynomax is what I was thinking about putting on there and replacing the Flow.........hmmm

Oh ya, nice ride.

 

Your correct on the back pressure theory. Thats why I left the stock piping and cat in. I just wanted a deeper tone, I knew I wouldn't get much of a power boost, so why spend the money. I figure I will go all out with a real exhaust if I ever go forced induction (then its worth the loss in back pressure) and I would have the tire mounted on the roof by then and I could run Duals. As for the muffler, I'd go with a dynomax. Its mosly louder in the lower RPMs and its never too loud. I took my gf home with me this weekend to NC and those are the times (in my opnion) that you want the exhuast quietest, and I never thought it was too loud. Also, your muffler will get slightly louder over time and espically when its hot (on long trips). Many have liked the magnaflow as well. Check out Corey's exhaust page. Though, you really can't tell how loud the thing is b/c thats all dependent on how hi the volume is on your computer. The only thing you can really tell is the tone. Get either a dynomax (I love mine) or a magnaflow and you should be happy. The dynomax is cheap to. $40 I believe at summit... I can't remember the exact model #, but I'm sure someone will chime in soon with it

Good luck,

 

Not me.

I have lots of torque down low. I have trouble avoiding wheelspin, especially when it's wet.

My .02
Dr. Z

 

thanks.

i have only the dynomax muffler, stock pipes.

 

So, from what I've seen cat back for the 3.0 isn't that good, so what if I were to buy a free flow cat and a free flow muffler?

 

Well thats what I did, Free-flow cat and Muff.
Lost low end, might have to go back to stock cat and just free flow muff.
Still thinking this out.

 

I've heard that the longer the muffler the quieter it will be too, although you probably don't want to fork out that money again.

By the way, what do you guys think the best (highest flow rate) cat is on the market? I've heard of Magnaflows, Extremeflow, Car Sound, and I don't know which flows the best. Anyone?

Chris

 

Probaly any and pretty inexpensive way to regain some if not all or more low end is to get the Perfect Power SMT-5 or 6, because you can probably advance the timing more now that you have a more free flowing exhaust.

Chris

 

SMT-5 or 6 ??? Is this available for the 2Gen 3.0 Runners.
Can you explain what this is, as I thought it was only for the 3.4 motors?
Yes- I'll search for the info too.
Just was wondering about you opinion because you have it?

Thanks

 

DrtRunner;

This is the thread you're looking for:

https://www.yotatech.com/forums/show...&threadid=5130

 

I just found this interesting bit of info on the N.W.O.R. site. This is their justification for using 2-1/4" tubing on their exhaust systems.

 

Sounds like NWOR might have it backwards?
I thought the larger tubes would decrease back pressure?
Therefore reducing low-end?

Wierd

 

NWOR has it correct (as do many other companies also). If you use too large of exhaust tubing for your engine setup, you will lose top-end HP and Torque because the exhaust gasses cool too rapidly, losing velocity in the process. Too large of primary (header) tubes causes a loss of low-end power.

I don't understand why people think that 4-stroke engines need a lot of backpressure to produce Torque. 2-strokes do, but not 4-strokes. The stock manifolds and Catalytic converters are going to provide all the backpressure you'll need for low-end torque and power. They also cost you some top-end power as well.

Well designed Headers for street use provide good power improvements over the stock manifolds all across the RPM range.

The same goes for a properly designed exhaust system. My Jardine gave me more torque down low along with more power everywhere else, too.

Talk to a qualified Exhaust specialist. Someone who is highly respected in your area, someone who does real hot rods, not ricers, and ask them about this stuff...

My .02
Dr. Z

 

I put the 2 1/4" pipe on mine from the cat-back with a Magnaflow and it's been my best mod yet!

My 3.0 finally felt like it could breathe and it actually came alive, ALIVE I TELL YOU!

Maybe my cat's so clogged it provides the back-pressure.

Warren

 

Ok, I need some help figuring this out. Perhaps my situation is different due to the mods of the heads on my 3.0, or maybe theres really something to this stock diameter tubeing thing. Heres my situation. Stock 3.0L with stock exhaust, A/T, 30" tires geared for 28". Yea, its slow, no real low end torque to speak of, but it gets you there. Muffler rusts out, so I have a 2.25" Dynomax and 2.25" tailpipe welded on. Sounds perfect. I even "think" I feel a little more response with it. Still a dog off the line, but I feel better about it though. So I live with it. That muffler starts to get a crack in it a few years later, but I have a bad valve also so I need head work. I have the heads rebuilt, ported and polished and the cams reground by DOA. Once that all is put back on and its running good, I drive it for a few months. There was some improvement in power from 3k and up. Off the line, its still dogish. I do a test drag race between points a, b and c near my house. Not sure of the distance, but I get up to 53mph and 60mph at points b and c. I then get a full 2.5" exhaust welded on to the stock down pipe as close to the manifolds as I can get. Includes a free flow cat and another dynomax muffler and tailpipe. All 2.5". Now I "think" I have more low end torque, but its still not what I wanted, but it pulls hard at right at 3k and keeps pulling up to redline. On my test drag strip I can now reach speeds of 55mph and 68mph for points b and c.

Conclusions: If I did not gain any low end torque, I dont think I lost any either. But I did gain mid and upper end power. It can be felt for sure, but you have to get to 3K to really feel it kick. I can also at this point, spin the tire on wet pavement, whereas before I could not. On a hill, one day when had rained, I punched it from a stop, spun the tire, and it kept spinning as the rpms rose past 3500rpm, then it actually shifted into 2nd gear while it was spinning and spun the tire for a second, but I had to let off cause I was comming to an intersection. I dont know how long it would have spun if I had not let off.

Questions: Since the kick is not really where I needed it, if I added backpressure, could I maybe gain low rpm torque beyond what I had with the stock exhaust system? Im sure upper rpm kick will die, but I could live without it if I had the lower rpm kick, to a point maybe.
Also, how does the quote about 2.5" pipe slowing the velocity and killing the 2000 to 4500 rpm range apply to me? Like I said, I did not lose any low rpm torque, but I did gain speed at both test points. It has more kick at 3000 now than it did with a stock system with 2.25" catback.
Can I add a small diameter tailpipe in place of the 2.5" off the muffler and gain any velocity in exhaust flow?
Im not trying to dispute anything, just trying to understand what is happening and why so if I need to tweak on it a little I can.
Maybe the percieved loss of low rpm torque is really just that you have the same on the low end, but you get an extra boost when you get to 3K. Maybe the trick is to time it doing 30 or 60 foot runs with stock exhaust, 2.25" catback and so on and so fourth. But then again, a few runs on a chassis dyno will tell the tale also. Any thoughts anybody?

 

hmmmm now im kinda scared. i have a hiflow cat coming for my 1990 3.slow as well, but everything else is stock save the FIPK and bosche 4+ plugs. With my current, 13yr old, clogged, OEM cat, the FIPK gave me better pulling from 3k-5k....

 

OK, I'm seeing what every one is saying. I'm just wondering what is the best setup that I can go with on my 3.0. Should I get a free flow cat and keep the stock muffler, or visa versa? What about both? Headers are not in the question right now, so what would you suggest?