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Old 09-24-2011, 01:14 PM   #1
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Exhaust question!!

I have a 89 5.0 with an x pipe and two flowmasters.no cats nothing.some tell me I need back pressure.and some tell I should take off the flows.what should i do??
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Old 09-24-2011, 02:01 PM   #2
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Your exhaust is a pretty common exhaust setup.I think your fine.maybe someone else can give you specifics but check this out for a little info. http://www.custom-car.us/exhaust/default.aspx
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Old 09-24-2011, 04:32 PM   #3
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Thanks..so I should just take off the flows from what I understood.am I right??
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Old 09-24-2011, 04:42 PM   #4
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Your flows should be fine.I don't fully understand.you are worried they are restricting you? I think your exhaust is fine just the way it is.

---------- Post added at 04:42 PM ---------- Previous post was at 04:38 PM ----------

Your mufflers flow better than stock,but still create sufficient back pressure.if anything you should have a small increase in power .maybe or maybe not noticable.and they sound better.
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Old 09-24-2011, 09:11 PM   #5
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Common misconception is that you need back pressure, you don't. Unless your running high horsepower your flows aren't really hurting you much at all. And here's an article to help you.

http://www.carcraft.com/techarticles...ion/index.html
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Old 09-24-2011, 09:31 PM   #6
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Quote:
Originally Posted by 93slowstang
Common misconception is that you need back pressure, you don't. Unless your running high horsepower your flows aren't really hurting you much at all. And here's an article to help you.

http://www.carcraft.com/techarticles...ion/index.html
Nice article!
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Old 09-25-2011, 05:00 PM   #7
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Re: Exhaust question!!

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Originally Posted by 89 Foxloco View Post
I have a 89 5.0 with an x pipe and two flowmasters.no cats nothing.some tell me I need back pressure.and some tell I should take off the flows.what should i do??
No you do not need more back pressure.
That is an old rodders tale that has been disproved numerous times.
If backpressure made more horsepower don't you think racers would have full exhaust on their cars?
No you do not need to remove your flowmasters.
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Old 09-26-2011, 12:22 AM   #8
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Quote:
Originally Posted by Trojan Horse

No you do not need more back pressure.
That is an old rodders tale that has been disproved numerous times.
If backpressure made more horsepower don't you think racers would have full exhaust on their cars?
No you do not need to remove your flowmasters.
So am good the way it is??
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Old 09-26-2011, 12:43 AM   #9
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Re: Exhaust question!!

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So am good the way it is??
Yes, you are fine the way you are.
I have pretty much the same exhaust on my car and it works just fine too.
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Old 09-26-2011, 10:13 AM   #10
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Quote:
Originally Posted by Trojan Horse

Yes, you are fine the way you are.
I have pretty much the same exhaust on my car and it works just fine too.
Alright..thanks..I'll get back to you on the smog pump..
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Old 09-26-2011, 10:52 AM   #11
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Wait I'm confused(imagine that hahaha). So if I don't need back pressure on my street car then why do I need mufflers? Simply to keep the power in a usable range for street driving?

I've un bolted the tail pipes and ran headers and H-pipe and the car ran like a three legged dog. Especially on the bottom it was gutless. Up top really wasn't that much better.

I know on a race/high HP application pipes and mufflers are restrictive, but on a street car it's "useful"? Excluding the noise of course.

Just removing the tailpipes for turn downs on my first GT took me from launching at idle to well over 2k controlling wheel spin. With turn downs I couldn't just stomp the gas and spin, but when it got above 3k I would smoke the tires.

My point is that if back pressure was useless, the common exhaust set up would not include mufflers on street cars with off road exhaust. Again exclude the noise because if the numbers were far apart people would say screw the noise I want the HP..? Please enlighten me as I have the old school mind set if someone could show me otherwise I'll cut the mufflers off mine this week.
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Old 09-26-2011, 11:19 AM   #12
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Re: Exhaust question!!

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Wait I'm confused(imagine that hahaha). So if I don't need back pressure on my street car then why do I need mufflers? Simply to keep the power in a usable range for street driving?

I've un bolted the tail pipes and ran headers and H-pipe and the car ran like a three legged dog. Especially on the bottom it was gutless. Up top really wasn't that much better.

I know on a race/high HP application pipes and mufflers are restrictive, but on a street car it's "useful"? Excluding the noise of course.

Just removing the tailpipes for turn downs on my first GT took me from launching at idle to well over 2k controlling wheel spin. With turn downs I couldn't just stomp the gas and spin, but when it got above 3k I would smoke the tires.

My point is that if back pressure was useless, the common exhaust set up would not include mufflers on street cars with off road exhaust. Again exclude the noise because if the numbers were far apart people would say screw the noise I want the HP..? Please enlighten me as I have the old school mind set if someone could show me otherwise I'll cut the mufflers off mine this week.
Read the article.
A bit of backpressure will improve your bottom end power, but there is not a huge difference. With a custom configured exhaust they actually picked up some power over wide open exhaust.
The point being he had nothing to worry about with his current exhaust on a street driven car.

Of course your car ran like crap when you removed the mufflers.
It wasn't tuned for that kind of exhaust flow.
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Old 09-26-2011, 01:28 PM   #13
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Exactly my point.
It's important to have the right back pressure and flow for your engine. Which is to say the idea that "you don't need back pressure" is just wrong. Reduced back pressure is ideal for street cars, and for race motors need even less(far less).

Didn't read entire article, but what I did read is pretty good.
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Old 09-26-2011, 01:42 PM   #14
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Re: Exhaust question!!

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Exactly my point.
It's important to have the right back pressure and flow for your engine. Which is to say the idea that "you don't need back pressure" is just wrong. Reduced back pressure is ideal for street cars, and for race motors need even less(far less).

Didn't read entire article, but what I did read is pretty good.
If that is what you tune for (most street cars) then yes, you need a little backpressure.
You could also tune for no backpressure with very similar results.
There is just not enough difference to worry over it either way.

The thing is, unless you can afford a custom tuned/flowed exhaust, the off the shelf varieties will serve very well for street purposes.

Thanks for the discussion, it makes me think and keeps my brain from stagnating.
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Old 09-26-2011, 02:22 PM   #15
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Lol me too, and I'm learning! 
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Old 09-26-2011, 04:53 PM   #16
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Quote:
Originally Posted by 89 Foxloco
I have a 89 5.0 with an x pipe and two flowmasters.no cats nothing.some tell me I need back pressure.and some tell I should take off the flows.what should i do??
For back pressure all you want is about 2-5 psi for back pressure. You can usually get that from the bends in the exhaust.
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Old 09-26-2011, 06:58 PM   #17
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Velocity is often mistaken for back pressure. On most any car now no matter what you do performance wise it needs a new tune. Most cars come tuned to back pressure and taking it away will affect it's low end torque. You can always tune around it and pick up the lost torque and then some.
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