sports exhaust
06-25-02, 03:20 AM
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an exhaust system rarely 'saves fuel' - don't believe the voodoo about back-pressure. The engineers know what they're doing.
However a less restrictive exhaust can provide a modest (up to 5hp) increase. Usually any perceived change in performance UNDER 5 hp is merely placebo effect (you expect the car to work better so you believe it does) but the little bit of extra grunt is at least good for bragging rights and on a 105hp engine is an almost 5% gain right out of the box.
Mazdatrix has some lovely systems now available.
However a less restrictive exhaust can provide a modest (up to 5hp) increase. Usually any perceived change in performance UNDER 5 hp is merely placebo effect (you expect the car to work better so you believe it does) but the little bit of extra grunt is at least good for bragging rights and on a 105hp engine is an almost 5% gain right out of the box.
Mazdatrix has some lovely systems now available.
06-25-02, 04:52 AM
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What exactly do you mean regarding "the voodoo about back-pressure"? The stock components are there mainly due to emissions reguirements and cost of manufacture.
Extractor-style exhaust systems do improve fuel ecomomy by allowing the engine to work more efficiently while at the same time greatly improving performance.
Rob, a good full exhaust system on a rotary will give you a very noticeable power increase. You're in Australia right? Any decent exhaust shop or rotary specialist should be able to help you out.
Extractor-style exhaust systems do improve fuel ecomomy by allowing the engine to work more efficiently while at the same time greatly improving performance.
Rob, a good full exhaust system on a rotary will give you a very noticeable power increase. You're in Australia right? Any decent exhaust shop or rotary specialist should be able to help you out.
06-25-02, 12:44 PM
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I mean voodoo as in aftermarket propeganda. Mazda, like Honda and other marques, try to produce the best product for the market which, in the case of sporty or sports cars, includes a high bhp rating especially for the North American market.
It irks me when some $250,000 per year in gross sales tuner claims their component can add 30 hp. Mazdas engineers are paid well to figure out the best balance of back pressure and yet all the aftermarket suppliers with their much more limited resources claim to outsmart the manufacturer. as 'proof' they go on about reducing back pressure, without mentioning the engine is designed to function with a certain amount of backpressure in the system (exhaust scavenging timing, etc)
The comments about emmissions and cost are valid; however emissions becomes the responsibility of the owner and regulations keep getting tougher, not easier. In Vancouver BC Canada and several parts of California they're switching to not only the annual smog testing but random testing on cars that look modified - getting busted with illegal emmissions on aftermarket parts can't be considered 'failure of manufacturer's parts - requires repair' but will instead be an expensive ticket, with some agencies talking about confiscating the offending aftermarket bits.
All that said, if you could suddenly turn a 135 hp system into a 165hp system just by bolting on a different exhaust it makes you wonder why the manufacturer didn't, say, offer the higher hp system at a premium, similar to a top-of-the-like corvette? the answer is swapping one component rarely offers such gains. If you visit the Mazdatrix site and look up fb exhaust systems they sensibly claim UP TO 5 hp gains as anything above that would be questionable.
It irks me when some $250,000 per year in gross sales tuner claims their component can add 30 hp. Mazdas engineers are paid well to figure out the best balance of back pressure and yet all the aftermarket suppliers with their much more limited resources claim to outsmart the manufacturer. as 'proof' they go on about reducing back pressure, without mentioning the engine is designed to function with a certain amount of backpressure in the system (exhaust scavenging timing, etc)
The comments about emmissions and cost are valid; however emissions becomes the responsibility of the owner and regulations keep getting tougher, not easier. In Vancouver BC Canada and several parts of California they're switching to not only the annual smog testing but random testing on cars that look modified - getting busted with illegal emmissions on aftermarket parts can't be considered 'failure of manufacturer's parts - requires repair' but will instead be an expensive ticket, with some agencies talking about confiscating the offending aftermarket bits.
All that said, if you could suddenly turn a 135 hp system into a 165hp system just by bolting on a different exhaust it makes you wonder why the manufacturer didn't, say, offer the higher hp system at a premium, similar to a top-of-the-like corvette? the answer is swapping one component rarely offers such gains. If you visit the Mazdatrix site and look up fb exhaust systems they sensibly claim UP TO 5 hp gains as anything above that would be questionable.
06-25-02, 05:02 PM
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No engine needs backpressure. For the best performance, an exhaust system should be as free flowing as possible for a pre-determined primary length and pipe diameter. Any added restriction or backpressure is of no benifit in any way.
I agree that putting an aftermarket system on an otherwise stock engine won't result in massive gains... probably around 10hp. But, a performance exhaust system is critical if you further modify your engine. Intake mods and engine porting are pretty much pointless unless you have a free flowing exhaust.
As for emissions testing, we Aussies rarely have to worry about things like that. I really couldn't care less about emissions.
I agree that putting an aftermarket system on an otherwise stock engine won't result in massive gains... probably around 10hp. But, a performance exhaust system is critical if you further modify your engine. Intake mods and engine porting are pretty much pointless unless you have a free flowing exhaust.
As for emissions testing, we Aussies rarely have to worry about things like that. I really couldn't care less about emissions.
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06-25-02, 05:16 PM
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Manntis,
I think you're missing the point. Engineers at car manufacturers design exhaust systems to meet a wide range of criteria. Power isn't the top of the list
Noise control, emissions control, etc, are usually the most important. Maximum power comes secondary.
What Racing Beat, et al, do is say "Forget about emissions and loud noise, let's not worry about those. What can we do to make an exhaust system that will make maximum power?"
They aren't "outsmarting" the engineers - they're creating a different product relating to a different set of objectives and a more select type of customer.
See the difference?
And BTW, you're misquoting the Mazdatrix figure. They're talking about *mufflers*, not full header/presilencer/muffler systems. The full system absolutely does add 15-20 horsepower. If you say otherwise, that is because you haven't driven an RX-7 with a full header exhaust. Anyone that has knows exactly what they're talking about. Period.
I think you're missing the point. Engineers at car manufacturers design exhaust systems to meet a wide range of criteria. Power isn't the top of the list
Noise control, emissions control, etc, are usually the most important. Maximum power comes secondary. What Racing Beat, et al, do is say "Forget about emissions and loud noise, let's not worry about those. What can we do to make an exhaust system that will make maximum power?"
They aren't "outsmarting" the engineers - they're creating a different product relating to a different set of objectives and a more select type of customer.
See the difference?
And BTW, you're misquoting the Mazdatrix figure. They're talking about *mufflers*, not full header/presilencer/muffler systems. The full system absolutely does add 15-20 horsepower. If you say otherwise, that is because you haven't driven an RX-7 with a full header exhaust. Anyone that has knows exactly what they're talking about. Period.
Last edited by SilverRocket; 06-25-02 at 05:18 PM.
06-25-02, 05:26 PM
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Thanks REVHED!
One other thing...
The reason is that these systems are not emissions legal, they are for "offroad purposes only" and this is clearly stated by Racing Beat, etc. Those of us who run these on the street are on our own, taking responsibility for the potential consequences. Mazda can't get away with this kind of thing for cars that are sold to be driven on public roads.
It isn't one component, it's the whole exhaust *system*. You have to remember that early 1980's exhaust/catalytic converter technology was not very good. Those original exhaust systems are terribly restrictive! Why do you think the Japanese spec 12A engines made more horsepower than the ones we got here? That's part of it.
I agree that there aren't very many easy 'bolt-on' mods that add 20% horsepower on very many cars - but for our cars this is a nice exception. How about the FC turbos? Did you know that adding a full exhaust system to those cars (as well as fuel cut defenser, boost controller) can net gains on the order of 50-60 horsepower?
How about the Dellorto carburator I have installed on my car? Combined with my Racing Beat exhaust system and electric fan, I estimate I have on the order of 150 horsepower. RB claims 155 for my system. You may argue with that by your logic, but I'll tell you that one spin in my car will change your mind forever
One other thing...
makes you wonder why the manufacturer didn't, say, offer the higher hp system at a premium
the answer is swapping one component rarely offers such gains
I agree that there aren't very many easy 'bolt-on' mods that add 20% horsepower on very many cars - but for our cars this is a nice exception. How about the FC turbos? Did you know that adding a full exhaust system to those cars (as well as fuel cut defenser, boost controller) can net gains on the order of 50-60 horsepower?
How about the Dellorto carburator I have installed on my car? Combined with my Racing Beat exhaust system and electric fan, I estimate I have on the order of 150 horsepower. RB claims 155 for my system. You may argue with that by your logic, but I'll tell you that one spin in my car will change your mind forever
Last edited by SilverRocket; 06-25-02 at 05:32 PM.
06-25-02, 07:08 PM
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The original question was "will the new exhaust system give better fuel economy?" The answer to that will be NO. You've all mentioned how it will increase HP. It doesn't increase Hp, it just frees up the Hp that was previously being used to push air through the restrictive pipes. Removing the water pump and adding an electric pump will free up about 5Hp, (i know someone who dyno tested so that is an accurate number). To truely produce MORE power, you have to mix more air and fuel. This does not lead to better fuel economy. Everything else, like replacing exhaust systems, only lets the engine more efficiently apply the power it already makes to the rear tires and the road. Hope that all makes sense.
06-25-02, 07:39 PM
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That logic seems a little strange to me Project84. Not about the fuel economy, but about your "increasing hp" bit. Does not the more efficient exhaust improve the flow capability of the system, and thus allow for more air and fuel to be burned? For example, it is a good idea to jet up some more fuel after you move to a better exhaust. Isn't the intuition behind it that you are now capable of flowing more air, and thus have the ability to burn more mixture?
It's the same on the other end - moving to an aftermarket carburator allows more air to flow into the engine. Taking advantage of that increased flow, you also dump a whole bunch more fuel in as well.
By your logic, it appears to me that no modification could be seen to "add horsepower"! I understand your point about the parasitic hp losses such as water pump, clutch fan, air pump, air conditioning, etc. But I don't believe that exhaust systems fall into that category.
Those are just my thoughts, feel free to correct me if there's something wrong with my logic.
It's the same on the other end - moving to an aftermarket carburator allows more air to flow into the engine. Taking advantage of that increased flow, you also dump a whole bunch more fuel in as well.
By your logic, it appears to me that no modification could be seen to "add horsepower"! I understand your point about the parasitic hp losses such as water pump, clutch fan, air pump, air conditioning, etc. But I don't believe that exhaust systems fall into that category.
Those are just my thoughts, feel free to correct me if there's something wrong with my logic.
06-25-02, 10:33 PM
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Think about how the rotory engine, (or even a piston engine) forces exhaust out of the combustion chamber. The piston or rotor has to apply force to the exhaust gases to push it out of the hole. It takes less pressure to push the gases out of a hole 1 inch in diameter than a hole that is only 1/4 inch in diameter. Take two stock engines, both with the same cc displacement, and same air/fuel ratio, but put stock pipes on one and a bigger exhaust system on another, the one with bigger pipes will be able to put more hp to the flywheel because the engine with smaller pipes has to dole out a little more power to pushing exhaust out the smaller pipes. Its like sucking a milkshake through a garden hose as compared to that little thing you stir coffee with. The exhaust system size has nothing to do with the amount of air and fuel you can mix. You can only mix as much as will fill one cylinder, or rotor chamber. If the exhaust ports are not larger enough to handle the gases expelled by the engine, you will have compression on the exhaust stroke which could hinder or stop all of your moving parts form moving. Think about the trap in the bottom of your tub. It doesn't have to be fully seated closed and still restrict water flow. So the trap can be open slightly, (like a small exhaust port) and with the water running at wide open (lets say a wot on the carb) the intake will over come the exhaust and create a backup condition. The water building up in the tub is exhaust in the engine, which makes the piston or rotor work harder to push out. Too much exhaust could build up more pressure on the exhaust stroke than on the power stroke. (engines aren't designed with exhaust ports that small, because of how inefficient this is.) Does this illustration make sense? Even if you totally remove an exhaust on an otherwise stock engine, that alone won't increase air/fuel mixture. It is just removing a component that used to require power from the engine. Now that power goes elsewhere, like the flywheel.
Another example is an stock engine coupled to a manual tranny, as exposed to an automatic tranny. The automatic has more moving parts and requires more power from the engine to turn all that stuff. Manual tranny has fewer moving parts and requires less energy to turn. So more power at the drive wheels can be obtained by putting the same motor on a manual tranny than by putting the same motor to an automatic.
Like you said, I made it seem like no mod can be seen to "add hp". Not many add horse power, its all about make the engine you have more efficient by sending the power it makes to the road. Adding more fuel and air (through boost and bigger ports, or bigger carbs and injectors) is the only way to truely "add" power. I have to get ready for work, but I will be back in the morning. I'll get back on here and see what y'all still think.
Another example is an stock engine coupled to a manual tranny, as exposed to an automatic tranny. The automatic has more moving parts and requires more power from the engine to turn all that stuff. Manual tranny has fewer moving parts and requires less energy to turn. So more power at the drive wheels can be obtained by putting the same motor on a manual tranny than by putting the same motor to an automatic.
Like you said, I made it seem like no mod can be seen to "add hp". Not many add horse power, its all about make the engine you have more efficient by sending the power it makes to the road. Adding more fuel and air (through boost and bigger ports, or bigger carbs and injectors) is the only way to truely "add" power. I have to get ready for work, but I will be back in the morning. I'll get back on here and see what y'all still think.
06-26-02, 01:03 AM
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the exhaust system is considered one 'component'. Not one part, one component of the powertrain. Just as engine/transmission are considered a 'power pack' though non-mechs rarely use that term. Let's not reduce this to bickering about semantics - in fact let's not reduce this to bickering, period.
Horsepower can be calculated as torque (in lb-ft) multiplied by RPM and divided by 5252. Is it logical to think that the exhaust component can change engine torque to up the product of this equation by 30?
The point of my original post is to point out the hyperbole-ridden sales job many companies perform with aftermarket parts. Some (modest) gains are obviously available component-by-component, but no one thing will suddenly create a land rocket. (unless that one thing is a rocket engine)
And yes, some engines do require backpressure for proper operation, and others merely perform better with proper pressure balances on either side of the ports/valves/magic thingies used in their respective configurations.
In a 6V53 silver-series, for example, backpressure helps build up adequate combustion chamber pressure for proper detonation, something the quench area and stroke cannot do fast enough in that engine configuration. Decrease backpressure and it runs like a bag of hammers.
In most passenger cars exhaust gasses are recirculated. The backpressure, in concert with an EGR valve in some engine configurations, keeps a certain amount of exhaust in the combustion chamber to (a) assist in creating proper detonation pressures [less air to suck in during a given measure of time] (b) reduce emmissions [unburned fuel particles are recirculated a second time to properly go boom] and (c) help improve fuel economy [again the unburned fuel recycled].
By 'tweaking' your exhaust component you may 'free up' some horsepower, which is good. But by overreducing your backpressure in a quest for a herculean gain you may be negatively effecting emissions, compression, and fuel economy, to say nothing of noise ordinance laws should your car let out a Harleyesque fart on average streets.
Too much of a 'good thing' can soon turn bad.
Horsepower can be calculated as torque (in lb-ft) multiplied by RPM and divided by 5252. Is it logical to think that the exhaust component can change engine torque to up the product of this equation by 30?
The point of my original post is to point out the hyperbole-ridden sales job many companies perform with aftermarket parts. Some (modest) gains are obviously available component-by-component, but no one thing will suddenly create a land rocket. (unless that one thing is a rocket engine)
And yes, some engines do require backpressure for proper operation, and others merely perform better with proper pressure balances on either side of the ports/valves/magic thingies used in their respective configurations.
In a 6V53 silver-series, for example, backpressure helps build up adequate combustion chamber pressure for proper detonation, something the quench area and stroke cannot do fast enough in that engine configuration. Decrease backpressure and it runs like a bag of hammers.
In most passenger cars exhaust gasses are recirculated. The backpressure, in concert with an EGR valve in some engine configurations, keeps a certain amount of exhaust in the combustion chamber to (a) assist in creating proper detonation pressures [less air to suck in during a given measure of time] (b) reduce emmissions [unburned fuel particles are recirculated a second time to properly go boom] and (c) help improve fuel economy [again the unburned fuel recycled].
By 'tweaking' your exhaust component you may 'free up' some horsepower, which is good. But by overreducing your backpressure in a quest for a herculean gain you may be negatively effecting emissions, compression, and fuel economy, to say nothing of noise ordinance laws should your car let out a Harleyesque fart on average streets.
Too much of a 'good thing' can soon turn bad.
Last edited by Manntis; 06-26-02 at 01:10 AM.
06-26-02, 01:24 AM
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Project84,
I've consulted with a car-guy friend much wiser than myself, and thought it over... and... although I hate to admit it, you good sir are correct! I was wrong, in that the exhaust system is not "part" of the engine, but an accessory component that is not required for the engine to run properly. A reduction in exhaust restriction is in fact not allowing the engine to burn any greater volume of air/fuel mixture, but simply allowing it to burn the same amount over a lesser time period. In other words, the engine is able to 'push' the same amount of mixture out the exhaust pipes more easily, resulting in faster reving and the appearance of "more power" to the guy in the driver's seat. But, no greater volume of air and fuel actually flows through the engine. In order to do this, the actual intake (carburator or intake ports) and exhaust ports on the engine must be modified. Thus, an exhaust system does not "add" horsepower, it does in fact "free up" horsepower.
Now, I don't know much about this backpressure argument, but according to my wise friend a rotary engine will produce its maximum power with no pipes hooked up to the exhaust at all. I didn't say torque at low rpms or a wide and flat powerband, I don't know about that. However, as I now understand it, any pipes hooked up to the exhaust ports constitute restrictions and are *not* capable of increasing the maximum power of the engine. What's the reason? Because, no more air and fuel is actually admitted through the engine, because that has nothing to do with the exhaust. The amount of air/fuel actually burned is limited by the port sizes and carburator, and *cannot* change by altering the exhaust pipes! The only thing that can be altered is the speed at which the air and fuel is expelled from the engine. So, while exhaust scavenging makes up a little for bolting restrictive pipes to your engine, it still isn't ideal from a max power perspective.
Manntis,
A good exhaust system "frees up" approx 20% power on an otherwise stock 12A RX-7 engine. This is a dyno proven fact, known to rotary enthusiasts since way back when. Not quite sure how you can argue with that.
So, to sum this up, Project84 is right, and I thank him, because today I learned something interesting!
I've consulted with a car-guy friend much wiser than myself, and thought it over... and... although I hate to admit it, you good sir are correct! I was wrong, in that the exhaust system is not "part" of the engine, but an accessory component that is not required for the engine to run properly. A reduction in exhaust restriction is in fact not allowing the engine to burn any greater volume of air/fuel mixture, but simply allowing it to burn the same amount over a lesser time period. In other words, the engine is able to 'push' the same amount of mixture out the exhaust pipes more easily, resulting in faster reving and the appearance of "more power" to the guy in the driver's seat. But, no greater volume of air and fuel actually flows through the engine. In order to do this, the actual intake (carburator or intake ports) and exhaust ports on the engine must be modified. Thus, an exhaust system does not "add" horsepower, it does in fact "free up" horsepower.
Now, I don't know much about this backpressure argument, but according to my wise friend a rotary engine will produce its maximum power with no pipes hooked up to the exhaust at all. I didn't say torque at low rpms or a wide and flat powerband, I don't know about that. However, as I now understand it, any pipes hooked up to the exhaust ports constitute restrictions and are *not* capable of increasing the maximum power of the engine. What's the reason? Because, no more air and fuel is actually admitted through the engine, because that has nothing to do with the exhaust. The amount of air/fuel actually burned is limited by the port sizes and carburator, and *cannot* change by altering the exhaust pipes! The only thing that can be altered is the speed at which the air and fuel is expelled from the engine. So, while exhaust scavenging makes up a little for bolting restrictive pipes to your engine, it still isn't ideal from a max power perspective.
Manntis,
A good exhaust system "frees up" approx 20% power on an otherwise stock 12A RX-7 engine. This is a dyno proven fact, known to rotary enthusiasts since way back when. Not quite sure how you can argue with that.
So, to sum this up, Project84 is right, and I thank him, because today I learned something interesting!
06-26-02, 01:35 AM
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To be fair, I wouldn't know specifically about the 12a and its dyno history. Given that its stock output is 105 hp, a 20% gain represents about 18 hp and seems high - The only way I can see such gains being made are ripping out the late 70's, early 80's overaggressive emmissions control chokers called catalytic converters. But real-world facts win over book computations anytime (remember the old saw about bumblebees flight characteristics violating the laws of physics?) and if this dyno testing proves your point in the real world I can admit that I may be wrong about my 5hp projection.
I do, however, stand by my backpressure 'arguements' as valid across a spectrum of engines, based not on opinion or supposition but on studying mechanical engineering (vehicle specialist). My profs made a huge stink about backpressure, the fundimental importance of, and how huge gains in performance of any combustion engine configuration in a wheeled vehicle requires tweaks to several components.
Change the pipes, sure - but don't assume bigger is always better. After all, if that were true the little elegant rotary we hold so dear would pale in comparison to a big block chunk of Detroit iron, yeah?
I do, however, stand by my backpressure 'arguements' as valid across a spectrum of engines, based not on opinion or supposition but on studying mechanical engineering (vehicle specialist). My profs made a huge stink about backpressure, the fundimental importance of, and how huge gains in performance of any combustion engine configuration in a wheeled vehicle requires tweaks to several components.
Change the pipes, sure - but don't assume bigger is always better. After all, if that were true the little elegant rotary we hold so dear would pale in comparison to a big block chunk of Detroit iron, yeah?
06-26-02, 01:43 AM
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The only way I can see such gains being made are ripping out the late 70's, early 80's overaggressive emmissions control chokers called catalytic converters
I do, however, stand by my backpressure 'arguements' as valid across a spectrum of engines, based not on opinion or supposition but on studying mechanical engineering (vehicle specialist). My profs made a huge stink about backpressure, the fundimental importance of, and how huge gains in performance of any combustion engine configuration in a wheeled vehicle requires tweaks to several components.
(remember the old saw about bumblebees flight characteristics violating the laws of physics?)
But now I gotta go to bed... job interview tomorrow!
06-26-02, 01:47 AM
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Way off topic comment, but the thing about bumblebees is supposedly their wing surface area is far too small to support their weight in flight - because no one took into account certain characteristics of a quad-winged insect's flapping technique that creates microvortices that increase lift blah blah blah...
In the same useless info dept, the first ship to cross the atlantic under mechanical power (steam) had abord it a book that proved it was impossible for a mechanically powered ship to cross the atlantic. The author had performed all the calculations based on wood as a fuel, ignoring the 'new' power source, coal.
Shows I read way too many geeky books in my early teens.
In the same useless info dept, the first ship to cross the atlantic under mechanical power (steam) had abord it a book that proved it was impossible for a mechanically powered ship to cross the atlantic. The author had performed all the calculations based on wood as a fuel, ignoring the 'new' power source, coal.
Shows I read way too many geeky books in my early teens.
06-26-02, 02:01 AM
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Interesting! Important lesson that I draw from those examples (and lots of other things I've thought about lately)... Never get too sure about something being impossible or things in the world being any certain way. Innovation and expansion of knowledge are, ironically, products of maintaining an attitude of doubt, ignorance and detachment. Nothing is 100% certain, just varying degrees of likelyhood. In fact, if you really want to figure things out, the best strategy is to detach yourself completely from the answers. That way, you can just be pleased you found out how it works, instead of being upset it wasn't the way you thought it was.
Hey I'm 22 and I'm just getting into all the fun of geeky books... these last 2 months I've read "The Elegant Universe" (Brian Greene), "The Pleasure of Finding Things Out" (Richard Feynman), and "E=MC2" (can't remember, not Einstein lol).
Right now I'm starting into "nothingness: the science of empty space" by Henning Genz.
If you like this stuff, you can always check out www.physicsforums.com... just like this forum, but all about science! I haven't even registered there yet, cause I got nothing to contribute lol.
Hmmm... now I really got to get to bed...
Hey I'm 22 and I'm just getting into all the fun of geeky books... these last 2 months I've read "The Elegant Universe" (Brian Greene), "The Pleasure of Finding Things Out" (Richard Feynman), and "E=MC2" (can't remember, not Einstein lol).
Right now I'm starting into "nothingness: the science of empty space" by Henning Genz.
If you like this stuff, you can always check out www.physicsforums.com... just like this forum, but all about science! I haven't even registered there yet, cause I got nothing to contribute lol.
Hmmm... now I really got to get to bed...
06-26-02, 08:16 AM
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I see Y'all had an interesting conversation last night . Someone mentioned that they didn't want to bicker about semantics. I hope I didn't come across sounding like I wanted to argue. I myself don't know much about the backpressure characteristics of engines, but I'm glad everyone understands how the exhaust is restrictive as far as flow, and how that restriction can impede (how ever great or slight) engine performance. That performance may just be in the form of noise, pollution, or poorer fuel economy, but those are the things we trade off in our never ending quest to go from point A to point B as quick as possible. As long as the lack of plumbing for the exhaust doesn't cause the engine to run like a "bag of hammers" (I loved that one) it is a worthy trade, though it may not be "street legal".
Manntis, bringing up the formula for the definition of Hp was impressive. I have seen that formula since I was in Aircraft Fundamentals, learning to be a jet mechanic for Uncle Sam. Well, I just got off of work so its time to go to the gym and then hit the sack. Does anyone else work the graveyard shift?
I'll see y'all around the forum. ZOOM ZOOM!!!!!!!!!!!!!!
. Someone mentioned that they didn't want to bicker about semantics. I hope I didn't come across sounding like I wanted to argue. I myself don't know much about the backpressure characteristics of engines, but I'm glad everyone understands how the exhaust is restrictive as far as flow, and how that restriction can impede (how ever great or slight) engine performance. That performance may just be in the form of noise, pollution, or poorer fuel economy, but those are the things we trade off in our never ending quest to go from point A to point B as quick as possible. As long as the lack of plumbing for the exhaust doesn't cause the engine to run like a "bag of hammers" (I loved that one) it is a worthy trade, though it may not be "street legal". Manntis, bringing up the formula for the definition of Hp was impressive. I have seen that formula since I was in Aircraft Fundamentals, learning to be a jet mechanic for Uncle Sam. Well, I just got off of work so its time to go to the gym and then hit the sack. Does anyone else work the graveyard shift?
I'll see y'all around the forum. ZOOM ZOOM!!!!!!!!!!!!!!
06-27-02, 03:41 AM
#22
you guys read to much. to put this into laymen terms, yes you should see better gas mileage be it: you don't lay into the throttle. its goes like this. you have freed up power so that now to reach a certain speed takes less effort for your car. example: acceleration at half throttle would now take, say, 1/4 throttle, but generally you'll be happy with the power gain and keep your foot into it more thus making your gas mileage go down.
manntis: how in the hell does recirculating exhaust gas help mpg? you've lost me there, need advil. also i always heard the backpressure was used to scavenge exhaust gases at lower rpms to help torque. a good example is hondas with 3" piping loosing what little torque they had.
. to put this into laymen terms, yes you should see better gas mileage be it: you don't lay into the throttle. its goes like this. you have freed up power so that now to reach a certain speed takes less effort for your car. example: acceleration at half throttle would now take, say, 1/4 throttle, but generally you'll be happy with the power gain and keep your foot into it more thus making your gas mileage go down.manntis: how in the hell does recirculating exhaust gas help mpg? you've lost me there, need advil. also i always heard the backpressure was used to scavenge exhaust gases at lower rpms to help torque. a good example is hondas with 3" piping loosing what little torque they had.
06-27-02, 08:27 AM
#23
Open up! Search Warrant!
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Thats with a lot of performance mods. If it makes the car faster, or more powerful (or more efficient use of the power it does make), you want to drive faster. The faster you go, the more fuel you need to consume, which results in lower mpg. That is something that all after market producers know, and they print it in small print, if they print it at all. I've read that and it make perfect sense. If you change your care performance and keep your driving habits the same, you would be more likely to see better mpg, or what ever gain you were after. But who spends $$$ on after market performance parts and keeps their driving habits the same? You buy performance parts to do just that. Perform.
What I'm saying is that I agree with Jeremy
What I'm saying is that I agree with Jeremy
06-27-02, 09:18 AM
#25
Admitted 'rexaholic'
So, you guys are saying that the 1 1/2 inch (no kidding) tailpipe coming out of my sons's hon-duh is impeding the engine? Makes sense to me, but why put on a pipe that small? He's embarrassed about it! What new muffler would you guys recommend for it? (I promise, I'm not trying to change this into a honda forum, but there really isn't one like this forum).