Well in that case, just keep it stock till November or December. Give your self a nice Christmas present with some boost. Whats up with fellow DSM owners getting SC's? I've seen 3 or so threads recently were the OP's were DSMers? You guys get tired of breaking things? Cuz thats the same boat I'm in, in the process of selling mine.

Anyways good luck on your build

 

Lol my dsm is a stock 94 that I use as a daily...I did notice a few of us flocking over though. Must be some connection that just cant be seen

 

its true i build exhaust systems for a living.
http://www.magnaflow.com/07techtips/faq/question10.asp
its science not butt dynographs

 

very classy, maybe you should go back to dsm forums where idiots like you belong.

 

I agree.... My car felt faster with a full 3" exhaust in NA form than it did with the stock exhaust...

 

thats the problem, just because it makes bunch of noise dosent mean its faster did you actually got from the factory dual system with free flowing mufflers and no cats to straight through 3" system? probably not. There is alot of things that will make a difference.

 

Well free speech on a forum goes both ways. if you want to talk down to people new to these cars/motors who are trying to learn you should learn how to take it. back on topic, if someone were to get a full exhaust, and not go catless whatdiameter piping would be best for an na car? I know v6 mustangs and cameras like some back pressure and lose a bit of low end power going 3in exhaustbeing n /a is the same true for our 2jz motors

 

Ok so you build exhausts, thats irrelevant to hard evidence. And that link does nothing but make suggestions. Im talking about hard factual proof that a 3'' exhaust on a stock SC300 actually loses power in the low range..i.e- 1/4mi times, dynographs, 0-60 times, 60-100 to show possible mid-range gains, a straight run from a dig with 2 stock SC's, one with a 3'' exhaust and nothing else.


And just for note, my car didnt make alot of noise, it was actually fairly quiet. So again, and irrelevant comment. And I would say that being able to break traction from a dig with the stock auto AFTER getting the 3'' exhaust, vs. slow ugly acceleration with the stock exhaust is simple significant proof of a gain in the low end.


It could be that Im at/below sea level, thus a more dense air charge than those of you up north..so I may actually see a gain here where those in the higher altitude/lower oxygen areas may see a loss. So yes it is science, but just like in science, until proof is shown its simply a theory and not true until actually proven.

 

youre right because 2jz is a super duper engine that dosent need back pressure in N/A form...honestly this will be my last attempt to prove my point but it seems like you already have your mind set. I guess somehow i need to install 2 different exhaust systems on my stock GE motor and dyno 2 times to prove to someone on the interwebs that i'm correct.
http://speedtalk.com/forum/viewtopic.php?t=3100

 

its a gas engine they are essentially are all the same in n/a form, all n/a engines need some type of back pressure to make trq which is what gets you off the line.

 

and another good paragraph or two out of chevy hightech
Big pipes flow more, so is bigger better? Answer: absolutely not. Primary pipes that are too big defeat our quest for the all-important velocity-enhanced scavenging effect. Without knowledge to the contrary, the biggest fear is that the selected tube diameters could be too small, thereby constricting flow and dropping power. Sure, if they are way under what is needed, lack of flow will cause power to suffer. In practice though it is better, especially for a street-driven machine, to have pipes a little too small rather than a little too big. If the pipes are too large a fair chunk of torque can be lost without actually gaining much in the way of top-end power.

At this point determining primary tube diameters is starting to look like a tight wire act only avoidable by trial and error on the dyno. Fortunately, a little insight into what it is we are attempting to achieve brings about some big-time simplification. Our goal is to size the primary pipes to produce optimum output over the rpm range of most interest. The rate exhaust is dispensed with, and consequently, the primary pipe velocity, is strongly influenced by the port's flow capability at the peak valve lift used. From this premise it has been possible to develop a simple correlation between exhaust port-flow bench tests and dyno tests involving pipe diameter changes. This has brought about the curves shown in the graph Fig. 4 which allow primary sizing close enough to almost eliminate the need for trial-and-error dyno testing.

Read more: http://www.superchevy.com/technical/...#ixzz1WlYGRGOQ

 

I dont see why you have to get an attitude about it. Im simply saying there is no SOLID FACTUAL proof of your statements directly related to a 2JZ. You can posts links all day long that blab on about fuel ratio's, collector length and placement, muffler differences, etc..You want me to think otherwise, please by all means prove me wrong and stick your car on a dyno. Until then, I dont buy it. So keep getting frustrated and relying on google to try and prove your point, but in the end until I see solid significant FACT in loss of power on an n/a SC from a 3'' exhaust Im sticking to what I and several others had witnessed in my SC.


I know that a major loss in BP can lower hp/tq number in the low end of the power band, and yes it has been proven from time to time in certain cars. But explain to me how it is that some F-Bodies make better HP numbers with 3'' cutouts directly after the collector pipe? And how is it that some older n/a "brick" Volvo's run just as efficient as the Turbo Volvo's both with open DP's? Cause of something and the main thing most people, including yourself are missing. Cam timing. Different cars/engines will react differently with a larger diameter exhaust depending on cam timing/lsa/lft/drtn. That in balance with the proper sized exhaust based off of (and not science) fluid mechanics...I think you should know this...? Here just in case:

Q = v*A



Thats how you determine proper sized exhaust. Cam specs specifically timing/duration, exhaust flow rate and pressure rates, velocity rates, and sectional volume...If I went over your head let me know.

Want to shut me up, put your car on a dyno and get some graphs. Ive been doing this crap since you were probably in diapers. All I am saying is there is no hard evidence that the 2JZ actually loses tq/hp in stock na form due to an exhaust with a 3'' diameter..and all your links are pointless cause they are not talking about 1 specific engine or taking into account the specs of said engine, where its being tested (different elevations, different results...been proven time and time again), weather, temperature, humidity, etc., etc.

 

Just as a heads up, that article applies to header design. The scavenging effect is LOOONG gone by the time it reaches your catback.


edit: Also makes me cringe when people use "backpressure" as a good concept. Its always bad. Its gas velocity that needs to be accounted for. Not backpressure itself.

 

Was just about to add to that.


For those of you who are lost, and still consider back pressure to be a helpful thing, here is a link with a very good explanation on fluid mechanics and back-pressure..figure since google seems to be the main point of defense here tonight, might as well...read on:

http://www.3sgto.org/f2/billowing-ho...tems-5171.html

 

dont know about all that i build a low 9 sec lt1 fbody 10 years ago that has been long gone by now.
As far as the fbody i have plenty of experience with lsx/ltx engines. Most of the time those cars will make more power with cutouts after headers due to very strict exhaust design too much backpressure. Exhaust system makes 180 degree bend over the axle then a 90 degree bent into a muffler then another 2 90 degree bends out of the muffler. I've also made more power with dual 3" pipes off the collector 2 magnaflow mufflers and dumps over fully mendral bent 3" into 4" y pipe and 4" single y pipe back medral bent exhaust.
What i'm trying to say is yes every car is different but theres absolutly no reason an engine that makes less then 180rwhp needs 3" exhaust...i'm sorry but its true. You might feel gain over your stock system with cats but if you ran lets say a 2.5" system for example youre more then likely would make more power.