GOT2B GM Posted June 20, 2005 Report Share Posted June 20, 2005 I just got a new catback exhaust put on my Z34. It consists of a 2.5" Magnaflow Cat, 2.5" piping to a 2.5" Vibrant straight thru 12" resonator, 2.5" piping to the Y, 2.25" piping from the Y to the 2.25" Magnaflow mufflers with 04 GP tips. Its very raspy between 2000-2500 rpms. If I switched to a baffled resonator would that help? Any input would be appreciated, especially anyone with a system on their 3.4. Thanks. Quote Link to comment Share on other sites More sharing options...
chadz34 Posted June 20, 2005 Report Share Posted June 20, 2005 All 3.4's are very raspy in that range there is no real way to get rid of it. It's the engine that makes that noise. No matter what exhaust system you put on it WILL always be there. Does it only rasp when you first drive the car? does it eventually go away or get quieter when the car warms up? It should. Quote Link to comment Share on other sites More sharing options...
GOT2B GM Posted June 20, 2005 Author Report Share Posted June 20, 2005 I quietens slightly when warm but I'm pretty sure I've heard that a good resonator will reduce it alot. I just don't think that my straight thru resonator works as good as a baffled one. Quote Link to comment Share on other sites More sharing options...
Aaron Posted June 20, 2005 Report Share Posted June 20, 2005 I'm surprised your car does this. That is why the Magnaflow components have a good reputation with the 3.4 crowd, becuz with a full system you shouldn't hear the rasp. My Z34 never did it with my system on. I bet it is the resonator you are using, I used a Magnaflow one of those, and it never had the low RPM rasp. Quote Link to comment Share on other sites More sharing options...
GOT2B GM Posted June 20, 2005 Author Report Share Posted June 20, 2005 Do you have a part number for the Magnaflow resonator? Is it a straight thru design or baffled? Quote Link to comment Share on other sites More sharing options...
Aaron Posted June 20, 2005 Report Share Posted June 20, 2005 It's straight through, I don't have the number, search their website. Quote Link to comment Share on other sites More sharing options...
topless94style Posted June 21, 2005 Report Share Posted June 21, 2005 I used basically the same setup as Aaron, it sounds great and I have not had a problem with rasp. I got rid of my cat and now have a 3" DP, so we will see how that sounds soon. Quote Link to comment Share on other sites More sharing options...
GOT2B GM Posted June 21, 2005 Author Report Share Posted June 21, 2005 Hmm...Looks like I'll have to switch resonators. Quote Link to comment Share on other sites More sharing options...
Aaron Posted June 21, 2005 Report Share Posted June 21, 2005 I'd try that. If that doesn't work, you may be SOL, but that should work becuz your one now doesn't sound like a high quality one made to eliminate rasp, no offense. Quote Link to comment Share on other sites More sharing options...
z34Phoenix Posted June 29, 2005 Report Share Posted June 29, 2005 im looking to throw on an exhaust cut out, will i get the raspy sound when it is open? i am probably going to put the cutout right after the cat so i dont have to deal with o2 sims and junk.... and i may end up with 2 cut outs one before and one after the cat... so i got one for the street and one for the track. but will i hear that raspy sound when i open it up? Quote Link to comment Share on other sites More sharing options...
Aaron Posted June 29, 2005 Report Share Posted June 29, 2005 im looking to throw on an exhaust cut out, will i get the raspy sound when it is open? i am probably going to put the cutout right after the cat so i dont have to deal with o2 sims and junk.... and i may end up with 2 cut outs one before and one after the cat... so i got one for the street and one for the track. but will i hear that raspy sound when i open it up? Yes it will sound terrible, and you won't gain much--if any, power. Quote Link to comment Share on other sites More sharing options...
z34Phoenix Posted June 30, 2005 Report Share Posted June 30, 2005 what do you mean i wont gain much. the cut out will eliminate the majority of the exhaust system. i know the factory cat is restictive, but the rest of the system is still a restriction aswell.... so do you think i should just put it on the down pipe then for the max gain and call it a day? Quote Link to comment Share on other sites More sharing options...
93cuttysupreme Posted June 30, 2005 Report Share Posted June 30, 2005 I think the car needs some back pressure to run correct. :?: Quote Link to comment Share on other sites More sharing options...
Aaron Posted July 1, 2005 Report Share Posted July 1, 2005 The car not only needs some back pressure, but that exhaust isn't very restrictive. So all it will do is make your car sound embarrassingly bad at the track, and make it really annoying. Your best bet is to work on the intake side, or just do headers. Quote Link to comment Share on other sites More sharing options...
z34Phoenix Posted July 1, 2005 Report Share Posted July 1, 2005 everything i have read says that the cat on my 96Z is very restictive. i have plenty work on intake fwi ported throtle body and ported manifolds. everyone says that a full exhaust system will increase power. the power is created by lowering the amount of restiction. So, as long as i leave the correct amout of back pressure for the engine, i will be gaining power by doing a cutout Quote Link to comment Share on other sites More sharing options...
Aaron Posted July 1, 2005 Report Share Posted July 1, 2005 Then do it, but you won't see any gains. Quote Link to comment Share on other sites More sharing options...
z34Phoenix Posted July 1, 2005 Report Share Posted July 1, 2005 what ever. im an engineering student, i know about flow and restirctions. aslong as i get the right diameter for the cut out i can match any back pressure needed. and with less restiction. less restiction = more flow=more power. i can see why you or anyone else would be against this mod cause it is cheep. yes i wont sound great, but i dont care about sound i care cause i can just close the cutout. i just want the it for the power by the way do your home work! "The purpose of the exhaust cutout is to bypass the remaining exhaust system after the point at which the cutout is installed. When you bypass the remaining exhaust system you are making it easier for the engine to get rid of the exhaust. Therefore, you will gain horsepower and torque by making it easier for your engine to work. The factory exhaust system is restrictive and holds back the full potential of it." refference: http://www.installuniversity.com/install_university/installu_pages/freshman_year/exhaust_cutout_explanation.htm Quote Link to comment Share on other sites More sharing options...
Aaron Posted July 1, 2005 Report Share Posted July 1, 2005 Thanks for telling me what an exhaust cutout is and does, I would have never known otherwise, you know I just build my own tuned equal length headers, I have no idea about exhaust flow really. FYI I also am an engineering student... The reason it won't gain you anything is becuz the factory exhaust is sized perfectly, the mufflers are decent, the cat is good unless it is clogged, and the resonator is good. The problem lies in the manifolds. The exhaust system is only as strong as the weakest link, in our case, the manifolds. And I don't think you can fix that juding from what your mod list. Quote Link to comment Share on other sites More sharing options...
joey b Posted July 1, 2005 Report Share Posted July 1, 2005 Sonyman has a cutout and had some rather large gains from it. Quote Link to comment Share on other sites More sharing options...
z34Phoenix Posted July 2, 2005 Report Share Posted July 2, 2005 the research i have done says that unless you are doing some type of induction IE Turbo or Supercharger the factory headers are fine. And NO the factory cat is restictive. yes i know the factory headers are restictive, but there are bigger restictions else where. this is just a cheep effective way to gain power. yes, from what you say it will sound like crap, but what you are saying about the "lack of gain"? makes me even question your basic reasoning skills. i dont see how you are an engineering major. maybe computer ngineering or maybe you are studing to be a comercial waist engineer Quote Link to comment Share on other sites More sharing options...
Aaron Posted July 2, 2005 Report Share Posted July 2, 2005 the research i have done says that unless you are doing some type of induction IE Turbo or Supercharger the factory headers are fine. And NO the factory cat is restictive. yes i know the factory headers are restictive, but there are bigger restictions else where. this is just a cheep effective way to gain power. yes, from what you say it will sound like crap, but what you are saying about the "lack of gain"? makes me even question your basic reasoning skills. i dont see how you are an engineering major. maybe computer ngineering or maybe you are studing to be a comercial waist engineer They aren't headers, they are manifolds, and how you say they are not the most restrictive part of the exhaust shows your ignorance. I believe I've done more research on this than you. I have ran a 3.4 with more exhaust combinations than you can dream of, up to and including tuned equal length headers. The factory manifolds are fine, they do their job, but they suck compared to a set of headers, and they are very restrictive. The cat is not restrictive unless it is clogged. I put a full 2.5" exhaust system on my car, straight through mufflers, the best cat/resonator Magnaflow offered, etc. It is the best exhaust that can be had, and I noticed no power gains. In fact it felt quicker than when I ran it without an exhaust. When I put the headers on, it ran well, but still ran better with an exhaust. I see perfectly well how I am an engineering major, and OSU agrees, and pays for quite a bit of my schooling for it. Quote Link to comment Share on other sites More sharing options...
z34Phoenix Posted July 2, 2005 Report Share Posted July 2, 2005 well your perception is incorrect then. many people have seen gains by switching out cats and mufflers on the 3.4. i wasnt saying that factory headers were better then custom! i agree if you got the $$$ go for it. but for the normal guy they arent worth the cost. the fact that you have tried more combinations then i can dream of doesnt impress me. actually i think less of you for it. someone who claims to know so much wouldnt have had to try countless combinations to get it right. and correction for the record! the cat is restrictive. this whole discussion is about flow. a cut out on the down pipe will out flow any full exhaust system " . " more flow equals more power. end of story! Quote Link to comment Share on other sites More sharing options...
gp90se Posted July 2, 2005 Report Share Posted July 2, 2005 the stock cat isnt that restrictive on a 60v6 motor, not by a long shot. The biggest clog in a w-body exhaust is the manifolds, but since they are big $ to make/ have made, the best suggestion I can give a 3.4 owner is a complete 2 1/2 mandrel bent exhaust, magnaflow resinator and mufflers, the cat is up to you, but it really doesnt make a world of difference unless its clogged. Quote Link to comment Share on other sites More sharing options...
z34Phoenix Posted July 2, 2005 Report Share Posted July 2, 2005 im sorry, but all my resources say. on my 96 monte carlo Z-34 the cat is most restictive. i've even read where people have done pressure tests that show this. Quote Link to comment Share on other sites More sharing options...
Aaron Posted July 2, 2005 Report Share Posted July 2, 2005 Flow doesn't equal power. I agree a cutout will flow more than the full exhaust, but flow doesn't equal power. Just becuz your exhaust flows more doesn't mean it will make more power. This is a conception from the 60s, remember when they were using 2.5 INCH intake valves? The heads would flow upwards of 450cfm at full lift, yet the motors still made just 300-350hp. Today's small blocks are making 500hp and more on heads that barely crack 300cfm, if that much. If it was all about flow, than Milzy's 2" primaries are good right? Sorry, but a 200hp V6 doesn't need 2" header primaries. My intake manifold will outflow any intake that has ever been used on a 60* V6 before, end of story. This in no way, shape, form, or stretch of the imagination means mine will make more power. But with the built motor, where the heads can handle it, the cams can take advantage of it, etc, it will make power. Put this intake on a stock motor, you might see a 10hp gain, along with a 35 ft/lb loss. You havn't done research. You think woah, it is press bent, and OE, it must suck. The reality is it doesn't. My combinations weren't done so I could "get it right." They were done to see how the motor reacted with different exhaust combinations. I ran it with stock, converted to the full 2.5" system mentioned above (gains were nonexistant). In between this I ran the car with no exhaust, and hated it, and it lost power over the full exhaust. Then I went out on a header build. It was expensive, very much so, but it was also worth every penny. The best setup I found was the tuned equal length headers with the full exhaust. You're right, your cat is more restrictive than a straight pipe. But for a motor as lightly modified as yours, that is good, it needs the restriction. And it isn't a big enough restriction to worry about. You will need to modify your car a lot more to be able to take advantage of a cutout or a full system. Quote Link to comment Share on other sites More sharing options...
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