high altitude exhaust

[j99xj]

The $64,000 question:
Will altitude affect the optimum exhaust diameter?

After looking at Dino's new page on exhaust http://www.angelfire.com/my/fan/Exhaust_Pipe_Size.htm I realized that I may have "overshot" on my exhaust mods because I forgot about the 3% horsepower loss for every 1000 feet.

To the best of my knowledge, all my bolt ons should be good for 215 hp at SEA LEVEL. But that number diminishes to 176 hp where I live (6,000 feet), to as little as 138 horsepower where I like to four wheel (9,000-12,000 feet). As you would imagine, every last horsepower is a good thing here in Colorado.

My current exhaust setup is a stock manifold, 2.5" downpipe, 2.5" converter, and a 2.25" muffler/tailpipe.

Would I have any benefit swaping my current system for a mandrel bent 2" system from the header to the tail pipe?

Any ideas/suggestions are welcome.

 

[Dr. Dyno]

Don't bother 'cause I have a better idea. You could put a valve in the tailpipe and keep it partially closed to add a little restriction when running at low revs. Then when you're running the engine at higher revs or at sea level, you can open it up again. Think of it as being like a throttle but for the exhaust instead of the intake.
Even if you don't do this, your engine should make ample torque at low revs anyway.

 

[j99xj]

Even if you don't do this, your engine should make ample torque at low revs anyway.

I never said I didn't have enough low end torque. I was just wondering about the possibilites of an exhaust change. My Jeep 4.0 I6 has far more low rev torque than any other 4.0 v6 I know of like the 4.0 sohc Ford, and 4.0 dohc rice burner v6's (Nissan, Toyota). These v6's simply run like crap below 3000 rpm, the rpm where my Jeep pulls very strong.

Dino, I'm a performance nutcase. I'm sure you can relate. :roll: I got mod fever from your website. It's contagious.

Anyway back to your point, an exhaust valve sounds like it would work. I could run two parallel tailpipes from the muffler back. The larger one being my current 2.25 mandrel bent pipe for high revs, and a 2" regularly bent pipe for 4 wheeling.

But before I get my hacksaw out, I think it would be wise for me to do a tune up. I need to make sure I'm not losing performance elsewhere like in worn out plugs, dirty throttle body, dirty K&N, etc.

Thanks for the idea, I will consider it.

 

[sjx40250]

You might consider injector swap and get them matched. I don't believe your 2.5 does you any good with the tail being at 2.25. The highest restrictiction rules. I have a Borla header through tail with high flow cat. it is all 2.25 but has made a significant difference.

 

[tealcherokee]

You might consider injector swap and get them matched. I don't believe your 2.5 does you any good with the tail being at 2.25. The highest restrictiction rules. I have a Borla header through tail with high flow cat. it is all 2.25 but has made a significant difference.

not true, as the exhaust gets closer to the end, it cools, there for getting more dense, and "smaller"

 

[Russ Pottenger]

Don't bother 'cause I have a better idea. You could put a valve in the tailpipe and keep it partially closed to add a little restriction when running at low revs. Then when you're running the engine at higher revs or at sea level, you can open it up again. Think of it as being like a throttle but for the exhaust instead of the intake.
Even if you don't do this, your engine should make ample torque at low revs anyway.

Im not sure if I agree with the Dr. on the valve idea, but make sure you have 18 inches or so of tailpipe behind the muffler.

 

[Sniggs]

Just put a Banana in yo tailpipe!

maybe putting back to stock isn't a bad idea afterall?

 

[j99xj]

Just put a Banana in yo tailpipe!

Yea that will work. I'll be sure to also replace my muffler bearings, and top off my turn signal fluid while I'm at it. lol

 

[badron]

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Just put a Banana in yo tailpipe!
==============================
I been putting bananas in my tailpipe for years. Love then fried bananas!

 

[Beej]

I been putting bananas in my tailpipe for years.

:laugh2:

Oh man, that's gonna make an excellent signature for someone...