morpheus Posted November 15, 2009 Share Posted November 15, 2009 (edited) So I've decided to start my build of a complete custom exhaust on my R50, including headers, high flow cats, etc... I'm going to start ordering parts in december, and start to put it together once I've got everything. I'm starting with: Pacesetter headers, listed for 1995 Pathfinder: I have already ordered exhaust manifold gaskets for both the 1995 and 1998, and have verified that all the exhaust ports and studs line up, the only thing I will need to do is drill out the stud holes to the larger 1998 size vs the smaller 1995 size. Then I will run custom 2.25" dual pipes to dual magnaflow catalytic converters: Then again, custom pipes into a dual input/output magnaflow muffler: And then out to a dual tailpipe.. Anyone with comments/suggestions feel free to add them, as this is a completely custom job, as far as I can tell no one has successfully done it yet, at least not what I can find by googling.. Edited November 15, 2009 by morpheus Link to comment Share on other sites More sharing options...
tekazgtr1984 Posted November 15, 2009 Share Posted November 15, 2009 Awesome plan!!! Keep us posted on this build. It'll be nice to see what kind of gains you'll get from this. Cheers! Link to comment Share on other sites More sharing options...
180sx Posted November 16, 2009 Share Posted November 16, 2009 Only Suggestion I have would be to use 2" piping instead of 2.25" if your gonna be dual all the way. Well, 2" piping to the muffler. Then 2.25" out if you want. I say this because it will hurt your low end a lot if you go that big. Nissan used 1.5"-1.75" piping on these things. And the motor is not that big. And running 2.25" piping for 3 cylinders at only 150WHP is crazy! You'll lose all the velocity and scavenging the exhaust needs to make that low end. Just my thought. Also...Have you thought about using VG30 Cams? Jose Link to comment Share on other sites More sharing options...
180sx Posted November 16, 2009 Share Posted November 16, 2009 Another thought I had! What about using the heads from a NA Z31 300ZX? Or even from the WD21 pathy? Hmmm....I'm gonna have to investigate this path! Link to comment Share on other sites More sharing options...
morpheus Posted November 16, 2009 Author Share Posted November 16, 2009 I originally was thinking 2.5", but some of the stuff I was reading included pipe diameters for engine HP. 2.25 seemed like the next logical step. I was going to measure up the current pipe diameter next time I've got the truck on the hoist and use that as a judgement tool. As for the cylinder heads, I came across a lot of maxima guys doing head swaps for power gains, but my goal is not to increase HP, it's to increase torque and for free-flowing exhaust for better fuel effency, and also to sound better. Link to comment Share on other sites More sharing options...
MY1PATH Posted November 16, 2009 Share Posted November 16, 2009 (edited) Since your going all custom I would start with the pre-90 thorley headers. they are true long tubes and IMO much better. However you do it, cool project have fun and I agree with 2.25" Edited November 16, 2009 by MY1PATH Link to comment Share on other sites More sharing options...
shift220 Posted November 16, 2009 Share Posted November 16, 2009 I say use what comes off the headers. 2 or 2.25" will be good either way. This sounds like a great project and something I would like to do also. Thanks for being the guinea pig! Any way you could get a baseline on a dyno? Then after the exhaust get another at the same place? It would be really handy to compare before and after. Link to comment Share on other sites More sharing options...
morpheus Posted November 16, 2009 Author Share Posted November 16, 2009 I priced the thorley headers, and at double the price, I can't justify it. I'd love to do a dyno run, but I'm not even sure where there is one around here, nor do I have any concept on what it would cost to do it. Link to comment Share on other sites More sharing options...
new4x4r Posted November 16, 2009 Share Posted November 16, 2009 Nice work Morpheus! Can't wait to see how it works for ya :-) Link to comment Share on other sites More sharing options...
BowTied Posted November 16, 2009 Share Posted November 16, 2009 Neat project. I really suggest doing a before and after dyno. The "butt-dyno" can be mis-leading - you can feel like you gained something in one spot but overall have a net loss. There must be dynos near you, call the guys at Legendary Motor Cars they should know who has one nearby. There is one in London right near the airport (Chandler). If you want a simple baseline run or two to establish what you have (no tuning) I'd think it would be well less than $100. There is also a guy in Woodstock that is into building perforamnce Mustangs and other Fords but I didn't really like the guy (he did the dyno for my Chevelle) but he did have an impressive set-up. Mike, I am inclined to agree with the comments about 2.25 being on the large side. It is over twice as large (2.25 times actually) as 1.5" pipes. Even if the OE pipes are 1.75", that is still 1.65 times larger - I think that is significant - particularily as you say you are looking to build torque not HPs. The best bet to build torque is the long tube header that is designed for the engine in question as it will 'tune' the exhaust for best scavenging. The pipe size afterward is also important. Although this is a completely different animal, I think it illustrates my point: My Chevelle made 10HP more with open headers - but lost 12ft.lbs. For me, that didn't really matter as I started out with over 400ft.lbs, but I think opening the pipes up that much will have a similar effect. If the original pipe is 1.5 going to 1.75, or orginal 1.75 going to 2 - those are approx 1/3 larger and may get you what you need and be easier to bend and tuck up in the body. I am not an expert by any means. If your research shows otherwise, cool, I am intersted to hear about it. Link to comment Share on other sites More sharing options...
morpheus Posted November 16, 2009 Author Share Posted November 16, 2009 ok, you all talked me into it I guess... I found a guy to do a dyno run for $50 cash, so what's another $100 bucks on top of the existing project, right?? lol.. Link to comment Share on other sites More sharing options...
Pezzy Posted November 16, 2009 Share Posted November 16, 2009 Link to comment Share on other sites More sharing options...
Precise1 Posted November 16, 2009 Share Posted November 16, 2009 I have to agree with the smaller piping. My 3.0 liter stock diameter was 1.75, the Thorleys I just installed are 2.25" into a 2.0" magnaflow cat, then back to 2.25" through a magnaflow muffler and out the end. This is for all 6 cylinders, not 3!! 1.75-2.0" each seems plenty large... One other note, my set up is fairly loud at 2500-3000 rpm and sounds suspiciously fart cannish. I'm going to talk to th exhaust shop in the next few days to get their input, but I'll probably go with something like the Flowmaster Quiet series, or something. B Link to comment Share on other sites More sharing options...
BowTied Posted November 17, 2009 Share Posted November 17, 2009 ok, you all talked me into it I guess... I found a guy to do a dyno run for $50 cash, so what's another $100 bucks on top of the existing project, right?? lol.. I suggest asking the dyno guys what they think of the pipe sizing - their real world experience will be worth more than my anecdotal comments, lol. Link to comment Share on other sites More sharing options...
morpheus Posted November 17, 2009 Author Share Posted November 17, 2009 Ya, the more I think about it, and research around, the more I think 2" is probably a better idea. The only thing that might change that is if I measure the stock front pipes and find they're bigger than 2", but I doubt they are. I didn't pay attention to the size of the pipes last time I looked, I was more paying attention to if there was enough clearance for the headers. Link to comment Share on other sites More sharing options...
180sx Posted November 17, 2009 Share Posted November 17, 2009 Yup, like I stated, 2" would be the biggest size you want to run. And thats becuase of the scavaging effects. You want that velocity pull on the exhaust side. this also helps pull in more air from the intake side. More air equals more power! It also helps make the air/fuel mixture more clean, which burns easier, which equals more power! It may also lean it out just a tick, Which may let you advance the timing a bit, which could be even more power! Don't chain reactions make you want to scream in joy! Jose Link to comment Share on other sites More sharing options...
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