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Old 12-30-2003, 07:13 AM
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Backpressure = Bad.... Right??

Ok what exactly does backpressure do?? I know what it is (where exhaust has to work harder to leave the cylinders) and i know car sound better with headers and and open exhaust with little backpressure. What are side-effects of having backpressuere?? (i have heard that backpressure is good for lowerend torque, is that true?)

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Old 12-30-2003, 07:42 AM
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Take a look at this:
http://hotrodders.com/showthread.php...hlight=exhaust

More than you ever asked for and covers it all!

Chris
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Old 12-30-2003, 03:44 PM
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on newer vehicles you need some back pressure for your egr to work properly . the egr cools the cyl temp to prevent spark knock and to lessen nox emissions
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Old 12-31-2003, 07:52 PM
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dont bother clicking that link, its worthless. it will make you more ignorant about exhaust systems.

Use he header size that fits your needs. Backpressure is worthless, it hurts torque, and kills HP. Get long tube headers, they have more TUNING LENGHT. if you have a motor of 350 cubes, and smaller go w/ 1-5/8"headers. if it has more go w/ 1-3/4" tubes. use atleast 2-1/2" pipes out to free flow mufflers. Check your exhaust system for back pressure when you are done, if it has back pressure, try better mufflers. back pressure is NEVER A GOOD THING.
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Old 12-31-2003, 07:55 PM
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one of the reason i was asking is in my desicion over turbocharging or supercharging. I heard that back pressure (which turbos create) makes it so turbos have good torque in the bottom end and in the high end.
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Old 12-31-2003, 08:08 PM
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Quote:
Originally posted by D M N
one of the reason i was asking is in my desicion over turbocharging or supercharging. I heard that back pressure (which turbos create) makes it so turbos have good torque in the bottom end and in the high end.
Backpressure is worse for a turbo car.. ever wonder why people put huge down pipes after the turbos?? thats why.. back pressure is not your turbos friend.. it will spool up slower, and produce less boost.
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Old 12-31-2003, 08:10 PM
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you sound like you know alot about turbos, how do you put a single turbo system in a V8 engine??
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Old 12-31-2003, 08:17 PM
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Quote:
Originally posted by D M N
you sound like you know alot about turbos, how do you put a single turbo system in a V8 engine??
EFI or Carbed?

I would start by making room, probably locate the turbo in the front of the motor, and have the two exaust pipes join togather, into one pipe, then go into the turbo. Ofcourse you are going to have to go throught the normal plumbing for oiling, and cooling for the turbo unit, and then the ducting for the carb/ throttle body.
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Old 01-01-2004, 12:14 AM
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Quote:
Originally posted by D M N
one of the reason i was asking is in my desicion over turbocharging or supercharging. I heard that back pressure (which turbos create) makes it so turbos have good torque in the bottom end and in the high end.
Supercharging is much more easy than setting up a turbo and you'll get alot more out of it.
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Old 01-01-2004, 09:03 AM
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Quote:
Originally posted by L98vette1986
dont bother clicking that link, its worthless. it will make you more ignorant about exhaust systems.

Use he header size that fits your needs. Backpressure is worthless, it hurts torque, and kills HP. Get long tube headers, they have more TUNING LENGHT. if you have a motor of 350 cubes, and smaller go w/ 1-5/8"headers. if it has more go w/ 1-3/4" tubes. use atleast 2-1/2" pipes out to free flow mufflers. Check your exhaust system for back pressure when you are done, if it has back pressure, try better mufflers. back pressure is NEVER A GOOD THING.
HMMM, I would suggest you are ignorant if you did not get anything out of the link. It has everything you need to know about Naturally aspirated engine exhaust systems included in all the links of that post along with the information there. But, I bet you did not take time to read the whole post based on your response to it, and you basically said what the post ended up concluding after some debate.

BUT,

Quote:
Originally posted by L98vette1986
Backpressure is worse for a turbo car.. ever wonder why people put huge down pipes after the turbos?? thats why.. back pressure is not your turbos friend.. it will spool up slower, and produce less boost.
Not absolutely right. Turbo systems should use a smaller diameter tube than NA engines pre turbo. Put simply this is to maintain EG velocity to the turbine. A typical turbo engine will see two to three times the pressure on the exhaust side than the intake. That means around 30 to 45 PSI on a 15 psi engine. This is just a byproduct of the energy needed to drive the turbine. Now post turbo, the bigger the better.

Quote:
Originally posted by D M N
you sound like you know alot about turbos, how do you put a single turbo system in a V8 engine??

<-----------------------See my album---------

Quote:
Originally posted by L98vette1986

I Ofcourse you are going to have to go throught the normal plumbing for oiling, and cooling for the turbo unit, and then the ducting for the carb/ throttle body.
Most modern turbo are oil cooled only. Water cooling is just to idiot proof the turbo for those who will kill it when hot causeing coking.

Quote:
Originally posted by 87442lover
Supercharging is much more easy than setting up a turbo and you'll get alot more out of it.
Nope! A turbocharged engine will always make more power at the same boost level as long as compressor efficiency is decent. You loose about 10 percent of the superchargers power in mechanical losses driving the unit itself. Additionally, turbo engines will make more power under the curve due to wastegate control giving consistantly higher boost levels in the lower RPM range provided the turbo is properly sized and will spool early.

Chris

Last edited by TurboS10; 01-01-2004 at 10:08 AM.
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Old 01-01-2004, 04:48 PM
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thansk that helped alot
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Old 01-01-2004, 06:34 PM
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Quote:
Originally posted by TurboS10
Nope! A turbocharged engine will always make more power at the same boost level as long as compressor efficiency is decent. You loose about 10 percent of the superchargers power in mechanical losses driving the unit itself. Additionally, turbo engines will make more power under the curve due to wastegate control giving consistantly higher boost levels in the lower RPM range provided the turbo is properly sized and will spool early.
Chris
Hi Chris ,
I'm not being pedantic here I'm genuinely curious and know diddly about Turbo engines

If a turbo engine produces more power than a supercharged engine at the same boost why don't they use them on Top Fuel dragsters and the like ? .

Ron
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Old 01-02-2004, 01:31 AM
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I love it when Turbo S-10 replies to something, its always dead-on and well organized... Well said!

K
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Old 01-02-2004, 01:44 AM
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I hate to just jump in on someone elses topic---- BUT, they did build a prototype top fuel dragster many years ago 80's? The thing made so much H.P. at boost that it got squirrelly and scary from mid track on! In those days, they weren't sure how to tame the combination! I bet someone could these days though, Very Interesting!!
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Old 01-02-2004, 02:20 AM
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how can backpressure be bad for a turbo? isnt that how a turbo works? it produces more airflow because of the backpressure? isnt that why a turbo wont kick in from the start but after ur rpm's are up and ur backpressure is building up ur turbo really kicks in? from my experience with turbos i have observed that they work best after u get the engine to a higher rpm. backpressure has to affect that
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