trying to get info on back pressure
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Doesn't exhaust back up in between strokes because of atmospheric pressure? I think that's what they are talking about.
Too big or too open of exhaust on lower RPM long stroke engines will make an engine have to "push" exhaust through the atmospheric pressure every cylce.
Whereas a system that doesn't allow the pipes to equalize as quickly or at all in between strokes will get in increase in power because the engine won't be fighting the atmospheric pressure.
My .02 on the thought process behind that statement.
Too big or too open of exhaust on lower RPM long stroke engines will make an engine have to "push" exhaust through the atmospheric pressure every cylce.
Whereas a system that doesn't allow the pipes to equalize as quickly or at all in between strokes will get in increase in power because the engine won't be fighting the atmospheric pressure.
My .02 on the thought process behind that statement.
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Theres a few things in that write up I disagree with. For the most part he's generalizing and it sounds plausible,.. but when you think about it,.. it makes absolutely no sense.
About 20 years ago I read an article written by a GM engineer. He was on the team that designed the TPI intakes. He specifically stated that in order for the engine to run at optimum efficiency, that some back pressure is needed. The induction system was design for it.
The guy in the article is talking about exhaust gas velocity. Once the exhaust passes the manifolds why the hell would it NEED velocity anymore? Using a 4" exhaust would kill power,.. yet open headers will not? Come on. I can see velocity being needed in the induction. Yes.,. I agree 100%. And with a forced induction engine,.. I can understand where velocity is crucial. But I dont see where it plays that big of a deal with an NA engine,.. well at least once its passed the manifolds as long as the exhaust is not restricting anything I dont see where it would lose anything by virtue of lost velocity at the mufflers. It goes against so many other articles written by experienced well known engine builders.
Smokey Yunic wrote a book book on the subject a while back. I dont have it anymore. I'm trying to find it online. You guys cant argue with old Smokey,.. he is a legend.
Hurst
About 20 years ago I read an article written by a GM engineer. He was on the team that designed the TPI intakes. He specifically stated that in order for the engine to run at optimum efficiency, that some back pressure is needed. The induction system was design for it.
The guy in the article is talking about exhaust gas velocity. Once the exhaust passes the manifolds why the hell would it NEED velocity anymore? Using a 4" exhaust would kill power,.. yet open headers will not? Come on. I can see velocity being needed in the induction. Yes.,. I agree 100%. And with a forced induction engine,.. I can understand where velocity is crucial. But I dont see where it plays that big of a deal with an NA engine,.. well at least once its passed the manifolds as long as the exhaust is not restricting anything I dont see where it would lose anything by virtue of lost velocity at the mufflers. It goes against so many other articles written by experienced well known engine builders.
Smokey Yunic wrote a book book on the subject a while back. I dont have it anymore. I'm trying to find it online. You guys cant argue with old Smokey,.. he is a legend.
Hurst
Manufacturers are hunting for that perfect solution, where they can retain low end power and still have great high rshared_pm power. They are using the technologies that I mention to achieve this. Unless we use the same technologies, we simply have to install the parts that lean towards the cars intended use...been this way for a LONG time
So for this guy (and most street cars), a full exhaust will give him more torque in the RPMs where he spends the most time. Yes, he will sacrifice some peak HP for this compared to longtubes and open exhaust.
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Jeff
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93 Coupe - check out my blog - http://www.93coupe.com
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68 Coupe PROJECT <- Been in the family for 25 years!
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It is truely about backpressure and velocity. Velocity helps scavenge exhaust gases - and if this can be achieved (higher velocity) at lower RPMs, then you will increase your power/torque in those RPMs. At some point (higher RPM), the exhaust size that provided that higher velocity down low will become a restriction, limiting peak HP. Because drag cars go for peak HP and typically have a narrow target RPM that they achieve that HP - they just go uncapped and do not worry as much about velocity except for what they can tune with their collectors.
Manufacturers are hunting for that perfect solution, where they can retain low end power and still have great high rshared_pm power. They are using the technologies that I mention to achieve this. Unless we use the same technologies, we simply have to install the parts that lean towards the cars intended use...been this way for a LONG time
So for this guy (and most street cars), a full exhaust will give him more torque in the RPMs where he spends the most time. Yes, he will sacrifice some peak HP for this compared to longtubes and open exhaust.
Manufacturers are hunting for that perfect solution, where they can retain low end power and still have great high rshared_pm power. They are using the technologies that I mention to achieve this. Unless we use the same technologies, we simply have to install the parts that lean towards the cars intended use...been this way for a LONG time
So for this guy (and most street cars), a full exhaust will give him more torque in the RPMs where he spends the most time. Yes, he will sacrifice some peak HP for this compared to longtubes and open exhaust.
Oh for Wes yes I agree.
The difference between mufflers and no mufflers,.. or even open headers on a stock motor will be so negligible that it doesnt matter. Put the mufflers on,.. keep the man from pulling you over,.. save yourself the hassles and just do it.
Hurst
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Originally Posted by Tiffiny
"We all heart the Hurst"
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flowmaster 40's are nice
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nah didnt read it dont care.....I have mufflers.....my statement was in general...
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Bondsman
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Because as proven before....not everything you goggle hunt is golden...you combine 2 different topics in same thread......tuneable collecter is for an open exhaust set up, not a muffler set up...not going to read a book of BS
Last edited by GNs-r-slow; Oct 14, 2010 at 01:46 AM.
lol
