90TGP Posted March 30, 2003 Report Share Posted March 30, 2003 Well I want to race in the street legal shoot-outs at my local track, and they require that your car has to have mufflers. Well I'm currently running without mufflers [sounds great], and I'm looking for a good straight-through muffler. I was flipping through my summit catalog to see what they had to offer. Well Dynomax has Race Bullet mufflers for $32 a peice [2 1/2" in and out]. I'm guessing they are as good or probably better then glass-packs. What do you guys think of these mufflers? Here's a picture Quote Link to comment Share on other sites More sharing options...
JS91Z34 Posted March 30, 2003 Report Share Posted March 30, 2003 if they consider it a muffler, Use it I would. Some mufflers can actually increase HP rather than a straight pipe. Quote Link to comment Share on other sites More sharing options...
RebelGT Posted March 30, 2003 Report Share Posted March 30, 2003 if they consider it a muffler, Use it I would. Some mufflers can actually increase HP rather than a straight pipe. mufflers don't make horsepower, what are you smoking?...... Quote Link to comment Share on other sites More sharing options...
Redfox340 Posted March 30, 2003 Report Share Posted March 30, 2003 mufflers don't make horsepower, what are you smoking? No, they don't make it... you're right, but an optimized exhaust system needs a little bit of back-pressure to make the best gain out of any engine. Straight piping cause the motor to not accelerate at low speeds but has benificial attributes with greater mass flow rates @ high RPM's. So, technically, 'yes' a muffler can give you horsepower: it's the horsepower that you've lossed from a poor exhaust system and giving the engine the "room" it needs to pump out the power it was made for. - RedFox340 Quote Link to comment Share on other sites More sharing options...
RebelGT Posted March 30, 2003 Report Share Posted March 30, 2003 mufflers don't make horsepower, what are you smoking? No, they don't make it... you're right, but an optimized exhaust system needs a little bit of back-pressure to make the best gain out of any engine. Straight piping cause the motor to not accelerate at low speeds but has benificial attributes with greater mass flow rates @ high RPM's. So, technically, 'yes' a muffler can give you horsepower: it's the horsepower that you've lossed from a poor exhaust system and giving the engine the "room" it needs to pump out the power it was made for. - RedFox340 you need to do more research, backpressure is never a good thing. http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm Quote Link to comment Share on other sites More sharing options...
Redfox340 Posted March 30, 2003 Report Share Posted March 30, 2003 So, RebelGT, are you telling me you're strappin' on a 5" system to run 10 second quaters with your N/A car? - RedFox340 Quote Link to comment Share on other sites More sharing options...
RebelGT Posted March 30, 2003 Report Share Posted March 30, 2003 thats not what i'm saying at all, if you had read the link i posted it explains everything clearly. Quote Link to comment Share on other sites More sharing options...
Redfox340 Posted March 30, 2003 Report Share Posted March 30, 2003 So clear things up; I did read the link and that's why I posted my comment. So, if that link is true, why are the private and home parts providers from these forums (who make parts / systems at home) aren't creating them that big... or even better, why not the engineers who designed the car run that? There's more fluid / thermo - dynamics and optimization of internal combustion engines involved that what is said in that link. Plus, every manufactures' engines have different properties for tuning ...overall there's some basic guidelines, but there's always something to tweak and something to brag about. - RedFox340 Quote Link to comment Share on other sites More sharing options...
RebelGT Posted March 30, 2003 Report Share Posted March 30, 2003 i guess you didn't read the whole thing. Pipe Sizing We've seen quiet a few "experienced" racers tell people that a bigger exhaust is a better exhaust. Hahaha… NOT. As discussed earlier, exhaust gas is hot. And we'd like to keep it hot throughout the exhaust system. Why? The answer is simple. Cold air is dense air, and dense air is heavy air. We don't want our engine to be pushing a heavy mass of exhaust gas out of the tailpipe. An extremely large exhaust pipe will cause a slow exhaust flow, which will in turn give the gas plenty of time to cool off en route. Overlarge piping will also allow our exhaust pulses to achieve a higher level of entropy, which will take all of our header tuning and throw it out the window, as pulses will not have the same tendency to line up as they would in a smaller pipe. Coating the entire exhaust system with an insulative material, such as header wrap or a ceramic thermal barrier coating reduces this effect somewhat, but unless you have lots of cash burning a hole in your pocket, is probably not worth the expense on a street driven car. Unfortunately, we know of no accurate way to calculate optimal exhaust pipe diameter. This is mainly due to the random nature of an exhaust system -- things like bends or kinks in the piping, temperature fluctuations, differences in muffler design, and the lot, make selecting a pipe diameter little more than a guessing game. For engines making 250 to 350 horsepower, the generally accepted pipe diameter is 3 to 3 ½ inches. Over that amount, you'd be best off going to 4 inches. If you have an engine making over 400 to 500 horsepower, you'd better be happy capping off the fun with a 4 inch exhaust. Ah, the drawbacks of horsepower. The best alternative here would probably be to just run open exhaust! Other Rules A lot of the time, you'll hear someone talking about how much hotter the exhaust system on a turbo car gets than a naturally aspirated car. Well, if you are catching my drift so far, you'll know that this is a bunch of BS. The temperature of exhaust gas is controlled by air/fuel mixture, spark, and cam timing. Not the turbo hanging off the exhaust manifold. When designing an exhaust system, turbocharged engines follow the same rules as naturally aspirated engines. About the only difference is that the turbo engine will require quite a bit less silencing. Another thing to keep in mind is that, even though it would be really super cool to get a 4 inch, mandrel bent exhaust system installed under your car, keep in mind that all of that beautiful art work won't do you a bit of good if the piping is so big that it gets punctured as you drag it over a speed bump! A good example of this is the 3 inch, cat back system sold by Thermal Research and Development for the Talon/Laser/Eclipse cars. The piping is too big to follow the stock routing exactly, and instead of going up over the rear suspension control arms, it hangs down below the mechanicals, right there in reach of large rocks! So when designing your Ultimate Exhaust System, do be careful! Quote Link to comment Share on other sites More sharing options...
skalor Posted March 31, 2003 Report Share Posted March 31, 2003 I would get those to use as Dynomax is a real good quality for the price. I was considering getting them as well for my car...or my new TGP that I should be getting this week I have a question though...I know that some tracks are very particular about the whole "mufflered car" deal, but what are they going to do about the new turbo Neons as they don't come with mufflers :? Quote Link to comment Share on other sites More sharing options...
90TGP Posted March 31, 2003 Author Report Share Posted March 31, 2003 Most of the muffler rules pertain to the older muscle cars. But since the new Neon is factory without mufflers, I'm pretty sure they would be allowed. Quote Link to comment Share on other sites More sharing options...
RebelGT Posted March 31, 2003 Report Share Posted March 31, 2003 the neons are still running a cat, thats just as good i think. Quote Link to comment Share on other sites More sharing options...
RedZMonte Posted March 31, 2003 Report Share Posted March 31, 2003 N/A motors need backpressure. Turbo motors like as little back pressure as possible. open downpipe will allow FASTER spoolup time and more boost. No mufflers and 3" piping from the turbo back is going to be the best setup in most cases. The turbo itself creates more then enough backpressure for the motor to work properly, then when it spools the larger DP will allow the gasses to get out faster. the ammount of airflow out of the trubo is much more then a N/A motor because the turbo forces more air into the motor so it has more air coming out of the motor. RedZ Quote Link to comment Share on other sites More sharing options...
RebelGT Posted March 31, 2003 Report Share Posted March 31, 2003 Exhaust gases leave the engine under extremely high pressure. If we allowed exhaust gasses escape to the atmosphere directly from the exhaust port, you can well imagine how loud and cop-attracting the noise would be. For the same reason gunshots are loud, engine exhaust is loud. Sure, it might be cool to drive around on the street with that testosterone producing, chest-thumping, 150 decibel roar coming from your car… for about 5.3 seconds. (Not 5.2 or 5.4 seconds… 5.3.) Even the gentleman's gentleman has gotta use a muffler, or system of mufflers, on their exhaust. Again, you may hear a few SPMT's tell you that "Borla mufflers make horsepower!" Or "An engine needs some backpressure to run properly!" Nonsense. A muffler can no more "make" horsepower than Wile E. Coyote can catch roadrunners. Any technician with any dyno experience will tell you that the best mufflers are no mufflers at all! and if thats not enough, we can go in depth here: http://www.hondalife.com/articles/BackpressureandCrosssectional%20Area.htm Quote Link to comment Share on other sites More sharing options...
Redfox340 Posted March 31, 2003 Report Share Posted March 31, 2003 and if thats not enough, we can go in depth here: http://www.hondalife.com/articles/BackpressureandCrosssectional%20Area.htm First, link doesn't work. Second, again out of curiosity, why are you using import based I4's bulletin as a correct source for 'tuning' domestic V6's? And third, how can you say that N/A vehicles are not needing back pressure when a respected creator of W-Body parts (thanks RedZ) and my own personal GM mechanics (certified for over 17 years) says it true? You're not making a convincing arguement to me... I need more info to prove... and so do these people on these sites. So, RebelGT, are you telling me you're strappin' on a 5" system to run 10 second quaters with your N/A car? Plus, you still haven't given me an answer. What's your girth on your downpipe? - RedFox340 Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted March 31, 2003 Report Share Posted March 31, 2003 I will completely agree. N/A motors NEED some backpressure. My own 3.1L will attest to that. When I first got my exhasut done, (went from single to y pipe with duals), I cut the cat completely, and went with a straight pip into the y pipe with two small mufflers after that. It sounded great, but at low rpms, I could feel it was lackin some pep. Plus, you could hear the power being blown out the tips. Loud does not necessarily mean more power, sometimes it means all the gas isnt gettin burned up and actually exploding in the exhasut piping...making it loud. Anyway, went back a few months later, but a turbo tube in, to create some back pressure, and man, I could feel the extra torque around 2K rpms, plus it had more torque up top. It is not near as loud, but performs better, which is what I was looking for. Bottom line.......Some backpressure is essntial on N/A motors. Robby Quote Link to comment Share on other sites More sharing options...
Vegeta Posted March 31, 2003 Report Share Posted March 31, 2003 You would be wise to listen to rebelGT. Backpressure is not a good thing, ever. Imagine a perfect exhaust system? I hope you included variable length everything because the exhaust needs change at EVERY RPM. So, peak torque may come with a 2.25" exhaust and peak HP with a 2.5", but to have both you would need a "stage" exhaust just like SHOs have 2 stage intakes. Backpressure is not the key, tuning for sound and pressure waves is. Those have NOTHING to do with backpressure, but a vacuum at the ehxuast valve and port when the exhaust is opening to compliment the HIGH pressure area inside the cylinder. Why quote import sites? Cause it doesnt matter who makes the engine. Theory works for them all. Sure, firing order will come into play for the details of each system perfect for the application and price range. Quote Link to comment Share on other sites More sharing options...
90TGP Posted March 31, 2003 Author Report Share Posted March 31, 2003 So, ugh, back to the muffler. Good deal? Quote Link to comment Share on other sites More sharing options...
Vegeta Posted March 31, 2003 Report Share Posted March 31, 2003 I think it will work out pretty well for you as long as you have 2.5" exhaust. Quote Link to comment Share on other sites More sharing options...
GnatGoSplat Posted March 31, 2003 Report Share Posted March 31, 2003 Backpressure is not a good thing in engines designed for optimal conditions. Sometimes engines are designed and tuned from the factory to run optimally with a certain level of backpressure in mind. The cam is timed in such a way that proper exhaust scavenging occurs with a certain amount of backpressure (exhaust velocity high enough that there is sufficient exhaust scavenging). Scavenging is when the exhaust velocity is high enough to pull all exhaust out of the combustion chamber, allowing the intake air/fuel mixture to be full strength. Sometimes the cam overlap in these engines is such that, remove the backpressure, and the exhaust velocity will suffer, causing exhaust reversion, which is the opposite of scavenging... the exhaust gets partially sucked back in through the exhaust valve, reducing the strength of the intake air/fuel mixture. Exhaust velocity is what matters. IF you could somehow design an exhaust with little to no backpressure that ALSO doesn't reduce exhaust velocity, that would be ideal. The problem is that simply going to larger diameter exhaust pipe will decrease backpressure, but also decrease exhaust velocity as well. On a turbocharged engine, the exhaust from the cylinders only sees the velocity going into the turbine. After the turbine, it doesn't really matter much. That's why you can use much larger exhaust pipe after the turbine and exhaust velocity isn't a big concern. So basically backpressure is always bad, exhaust velocity is always good, but there's a tradeoff because sometimes decreasing backpressure also decreases exhaust velocity. If you can eliminate backpressure while maintaining or increasing exhaust velocity, that would be ideal. And as Ben says, what is ideal at one RPM range isn't ideal at another. Cam timing also comes into play as well. Of course, I also may be totally off so correct me if I'm wrong. Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted March 31, 2003 Report Share Posted March 31, 2003 yeah shawn thats what I was imaging myself sayin...just couldnt put into words. I think the cam timing and scavenging has a lot to do with these 60* motors and their exhaust systems Actually, I do have varying diameters. I have 2.25" until it hits the y pipe where it splits into 2" piping to the mufflers then dual outlet tips after each muffler Robby Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.