i know theres been alot of opinions about gains and losses with thier banks system yet we still wait for that precious dyno from banks. there were post that banks said their exhuast gains 15 hp, the most from 0-3500 rpms but no dyno. according to them it provides gains at the low end, if you believe them thats up to you, even if they post a dyno its still up to you. the only way to be absolutly sure is to have to dynod yourself.
there seems to be alot of very sensitive butt dynos here. when you add a cat-back, especialy a louder one like banks then it becomes more of a personal expectation thing. im not saying anyone is wrong, just that their butt dyno's may be to personal taste. when adding a cat-back were not talking of huge gains, were talking about 10-15 hp and torque to the wheels. now if anyone actually lost any power it would be very minor, much less then the gain.
10hp doesnt really put a dent on the titans 5000lbs of weight, its so minute that the wind could zap your 10hp/tq + just like that.
usually the greatest hp gains are at upper rpms and if you compared 0-60 times it would be like a .1 improvement lol, reaction time or road conditions or the environment or tire pressure and many other factors will play a bigger role then a cat-back alone. im trying to say that its not a major gain all in itself to actually feel to the normal driver. your only doing 1/3 of the exhaust really need headers to get that last bit of juice out. even then with headers and a cat-back and lets say a intake, you will only shave around .5 sec off. a chip will definantly help out, especially a complete ecu tuner with preprogrammed inj/ing maps that override the stock ecu but will need to run premium for the greatest gains provided the actual chip company spends 100s of hours tuning for the best maps for power gains and the type of ecu tuner.
i just went out and measured our stocker at every point it changed diameter and found some very interisting things. nissan once again has put alot of thought into it design but like the stock intake they had to give in to suiting their target customers. a conical filter will be a bit louder inaddition to the already louder stock exhaust which some think is to loud already. the exhaust is suprising designed well in certain areas. the pipe coming from the passengers side is 2 1/4, the pipe coming from the drivers side to the Y that is longer goes from 2in and then widens to 2 1/4. this is to keep velocity of exhaust gases at the same speed as the enter in the 2 3/4'' choked up Y. this Y is mass produced this way for cost/time efficieny and is the one major point i see choking our system hindering gas velocity. the long pipe from the Y going to the muffler is 2 1/2 keeping velocity nice and smooth , muffler openings are 2 3/8 and the out end pipes opens up t 2 3/4. it then connects to a 3" tailpipe.
one missconception is that backpressure at low loads will help low end torque. on a new engine like ours which can alter a/f conditions accodingly backpressure is our enemy. no i am not crazy lol your engine already has enough backpressure with the cats and stock headers. ill talk about headers soon. backpressure hinders the sacavenging effect and pushes gases in to the combustion chamber making your engine work harder due to loss of cumbustion effieciency = loss of power. what you want is a low backpressure system with good velocity flow, this is where tubing comes into play.
i think it was bestatchess who metioned at lower rpms your exhuast tubing should be only big enough to sufficiently expel gasses (not exact words ) and that there is no gain without a loss at another point, this is true. our stock system has a major flaw and its the Y, this creates a major velocity gas loss. the stock exhaust may be also a cork, both hinder power. adding the banks kit solves these problems by adding a nice Y collector and low backpressure muffler but also adds huge tubing. i was under the impression we has 2 7/8 tubing reading post's till i measure it for myself.
banks's 3'' tubing is quite a bit bigger then stock which will hurt the low end a bit and add to the high end like many are saying. a larger diameter pipe has less backpressure but what we care about is gas velocity flow and since its a larger pipe gas pulses will be further thus slower = the loss if power, so yes backpressure and velocity is related in a way. the question is does the tubing diameter hinder exhaust flow as much as the stock muffler and Y? i doubt it, in fact theres probably a gain because if the extreme low pressure zone created behind the header by the cat-back. you may gain across the whole band but will not have as of a efficient gain if you say cut the stock pipe, added a nice smooth Y collector and a higher flowing muffler like the banks setup if your looking into just adding a cat-back, with gains towards the low end. id do this but getting a safety check is about impossible now here with a mod cat-back so i have to buy a bolt on.
the jba cat-back looks like a very nice setup, it retains similar tubing diameter (2 1/2 to keep velocity a flowing niclely) and corrects the stock setup flaws. i doubt them humps in the piping are there to create backpressure, since we dont really care about it with a cat-back what we care about is gas velocity.(yes im gonna keep on saying it lol) they are probably there to help silence the muffler. i notice they moved the muffler way back towards the tail end and added the Y collector right by the muffler, interisting since placement affect power also. too bad its made of aluminized steel and not SS, itll probably last longer then most will have their trucks anyway lol. the nice thing about it is that JBA is designed for thier header and actually dynod a truck with their header combo which yeilded very nice gains.
not sure about gibson, i havent seen a pic yet.
now headers are a key player in complementing a cat-back. they work in conjunction with each other to help focus power at a certain point or help a few 1000 rpms out where your cat-back may not be so efficient at. they should both be better designed then stock and not cost anypower loss or almost none at any point in addition to adding power across the band if designed correctly.
after taking time to look closely at nissans work i must say im pretty impressed how close to detail they are in areas other cars ive seen are very poor. itll be very hard to gain over what nissan has layed out, jba has done very nicely and im hoping more dynos from other manufacturers will follow.
this should make up for all the post i missed lol hope i everyone didnt fall asleep
now wheres that shaka smilee lol
i need a long
