mmitchell57 Posted June 16, 2014 Report Share Posted June 16, 2014 I've been digging around looking for exhaust options for the 720. In general, I want it be relatively quite a cruizing speed, but when I get on it I want it to growl some. Also, i'm interested in the performance aspect. So far all I can find is the pacesetter header, bolt on high flow exhuast, and assumably a custom built cat back from a local muffler shop. What options do I have? Is there already a reference here? I appciate the help. Let me know. The exaust is the next part of the project. 1 Quote Link to comment
datzenmike Posted June 17, 2014 Report Share Posted June 17, 2014 If you have no smog testing, loose the cat and run 2" pipe all the way back with the largest muffler you can find that will fit the 2" pipe. If getting custom bent system, maybe go 2 1/4" pipe. There is no magical hidden horse power increase with the exhaust, and headers are a money pit of disappointment. The makers won't tell you that the stock system is pretty good by itself. 3 Quote Link to comment
JoeCool Posted June 17, 2014 Report Share Posted June 17, 2014 I live in NC as well, and while you might be able to sneak by on the visual state inspection, why not keep it legal and help the air we breathe by not only shedding the old catalytic convertor, but replacing it with a high flow model. That is what I did along with a 2.25" thrush turbo muffler. 1 Quote Link to comment
datzenmike Posted June 17, 2014 Report Share Posted June 17, 2014 I ran just the catalytic converter on my Grand Prix... no muffler at all, what a great sound. I imagine the Nissan one is straight through honeycomb and won't muffle very much. Yeah if with a cat, then rum a turbo muffler. Nothing straight through, but packed with sound deadener. 1 Quote Link to comment
Justin Berni Posted June 17, 2014 Report Share Posted June 17, 2014 Does anyone know how it would sound with all stock exhaust but cut the cat off, my cat scrapes on everything and I want it gone but I don't know if it'll sound like garbage or not. 1 Quote Link to comment
datzenmike Posted June 17, 2014 Report Share Posted June 17, 2014 I doubt you will notice anything. They are a series of long very small diameter tubes so more or less straight through. Some of the older cats were packed with pellets and would muffle the sound and you could run with out the muffler. On the Nissan I don't think there will be anything noticeable. 1 Quote Link to comment
Z-train Posted June 17, 2014 Report Share Posted June 17, 2014 If you have no smog testing, loose the cat and run 2" pipe all the way back with the largest muffler you can find that will fit the 2" pipe. If getting custom bent system, maybe go 2 1/4" pipe. There is no magical hidden horse power increase with the exhaust, and headers are a money pit of disappointment. The makers won't tell you that the stock system is pretty good by itself. What Mike said.And Walker Super Turbo's are quiet at idle & cruising but bark when you put your foot into it. 1 Quote Link to comment
Buzzbomb Posted June 18, 2014 Report Share Posted June 18, 2014 Thrush makes a 2 inch inlet/outlet turbo style muffler.. Pretty nice price with an Advance Auto 15% or 20% off coupon too :) 1 Quote Link to comment
_chiefjt Posted June 18, 2014 Report Share Posted June 18, 2014 I run the Thrush Turbo muffler with all stock exhaust with an old ass cat. lol It sounds pretty good but my exhaust wasn't even connected to the OG muffler so I cut it right after it the cab and put an adapter and clamps to the muffler. So my exhaust ends right under the bed cause I never finished it. :P 2 Quote Link to comment
mmitchell57 Posted June 18, 2014 Author Report Share Posted June 18, 2014 Looks like the consensus is that the exhaust is not a location to capture performance. That being the case, make sure it's breathes well and move on. The current cat is all jacked to hell and needs to be replace. I'll do that with a high flow and then take a look at the mufflers referenced here to see what I like best. Sounds like the header is not work the investment at this time, which is cool. There's other place in the truck I can put the money and fix issues like ball joints, bushings, end links, brakes and more. 2 Quote Link to comment
Fat510 Posted June 19, 2014 Report Share Posted June 19, 2014 If you want growl, run a stock l20 manifold into 2 1/2" with a flowmaster all the way back in the middle. I have this on my wagon and it sounds like a small V8. 1 Quote Link to comment
datzenmike Posted June 19, 2014 Report Share Posted June 19, 2014 It's an '85 so Z24 engine. The manifold is 4 into 2 with the dual down pipe into one and then into the cat. 1 Quote Link to comment
Fat510 Posted June 19, 2014 Report Share Posted June 19, 2014 It's an '85 so Z24 engine. The manifold is 4 into 2 with the dual down pipe into one and then into the cat. Oops, wasn't paying attention but I think that would still do what I'm talking about 1 Quote Link to comment
datzenmike Posted June 19, 2014 Report Share Posted June 19, 2014 I think the Z24 uses a 2" down pipe already and going much larger slows down the exhaust speed. You want the gas speed to be as fast as possible and the pipe size just short of restrictive. Faster gas speed means it has higher inertia as it exits the engine and tends to draw out more of the exhaust at higher RPMs. In fact during the overlap period when the intake is also open it helps suck in some fuel and air or at least start it moving. This reduces the work load on the engine and increases efficiency and also why putting a large pipe on often drops bottom end torque. The Z series are not big revving motors and for the most part the exhaust size is more than adequate. A 2" pipe is 3.14 square inches in cross section. Going to 2.25" makes it 3.53 square inches an increase of 12.5%!!!! More than enough. 2 Quote Link to comment
Fat510 Posted June 20, 2014 Report Share Posted June 20, 2014 I think the Z24 uses a 2" down pipe already and going much larger slows down the exhaust speed. You want the gas speed to be as fast as possible and the pipe size just short of restrictive. Faster gas speed means it has higher inertia as it exits the engine and tends to draw out more of the exhaust at higher RPMs. In fact during the overlap period when the intake is also open it helps suck in some fuel and air or at least start it moving. This reduces the work load on the engine and increases efficiency and also why putting a large pipe on often drops bottom end torque. The Z series are not big revving motors and for the most part the exhaust size is more than adequate. A 2" pipe is 3.14 square inches in cross section. Going to 2.25" makes it 3.53 square inches an increase of 12.5%!!!! More than enough. Oh, I was going off how to make it sound cool more than the efficiency side of it. But a Z24 might sound different than a L20 with the same setup. 1 Quote Link to comment
mmitchell57 Posted June 26, 2014 Author Report Share Posted June 26, 2014 Boom. I'm sold. Seriously, this is good info. On another note, finally had a chance to go in and start checking out the exhaust to see what I was dealing with. I had one manifold bolt missing. I went to pull another to see thread and length. It was finger tight. I started to check all the others.... finger tight. Went through and applied some torque to tighten them up. There is a tiny different, but it's enough to be noticeable. I figure I'll end up keeping the manifold and look at doing work from the cat back. Suggestions on cleaning up the manifold and making it look presentable? Also, I am possibly going to replace all exhaust studs with something nicer and newer. 1 Quote Link to comment
datzenmike Posted June 26, 2014 Report Share Posted June 26, 2014 Replace the exhaust to down pipe studs/nuts with stainless steel and you'll never have trouble removing them again. Remove and sand blast the manifold. Spray paint with high heat silver or white to reduce under hood temps. 2 Quote Link to comment
mmitchell57 Posted June 27, 2014 Author Report Share Posted June 27, 2014 Done deal. I'll get it knocked out. Is this a standard lowes purchase? 1 Quote Link to comment
Justin Berni Posted July 25, 2014 Report Share Posted July 25, 2014 I cracked my muffler, and it kinda got ripped off, so now I'm running stock exhaust, with a cat, except from the muffler and back is ripped off, anyone know if this is bad to run? I understand a muffler gives back pressure, so without my muffler am I doing harm to my engine? 2 Quote Link to comment
crimsoneclipse Posted July 25, 2014 Report Share Posted July 25, 2014 I cracked my muffler, and it kinda got ripped off, so now I'm running stock exhaust, with a cat, except from the muffler and back is ripped off, anyone know if this is bad to run? I understand a muffler gives back pressure, so without my muffler am I doing harm to my engine? Might change your performance higher or lower but it's not likely noticeable. I don't think the pipe is short enough to cause any problems. How does it sound? 1 Quote Link to comment
datzenmike Posted July 25, 2014 Report Share Posted July 25, 2014 Well it's illegal to dump exhaust in front of the rear end unless it's to the side. No one really cares but if you piss a cop off he may look for it. 1 Quote Link to comment
Justin Berni Posted July 25, 2014 Report Share Posted July 25, 2014 It sounds alright, my friends say it sounds awesome and want me to leave it. For now I might just weld some pipe going all the way back and have it come out under the tailgate, cuz I don't care for the exhaust fumes filling my cab. 2 Quote Link to comment
Justin Berni Posted July 25, 2014 Report Share Posted July 25, 2014 Also does anyone know the diameter of the stock exhaust on an 86 720 z24 1 Quote Link to comment
Z-train Posted July 25, 2014 Report Share Posted July 25, 2014 More then likely 1.75 inches 1 Quote Link to comment
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.
Note: Your post will require moderator approval before it will be visible.