Jdm exhaust muffler

[ajmcforester]

I can't wait to see it on your car take pictures of the installation, I've looked at this header it is so nice (you better not scratch it). If I ever find my rear resonators for my vintage Supersprint exhaust will haft to compare exhaust tones.

By the way it was mentioned a triple carb setup are you going to run stock carbs or a different setup. You are going to be able to push more volume with that setup. If you are going stock intake don't go over 2.25" pipe the car will not scavenge properly at low RPMs and you will louse some low end power if you go larger.

[LeonV]

If you are going stock intake don't go over 2.25" pipe the car will not scavenge properly at low RPMs and you will louse some low end power if you go larger.

Not true, this is not documented to have ever happened and is just internet myth. People love repeating "backpressure" and "lose low end" but no one actually reasons why that would be true or false.

Here is one thread that discusses this: http://forums.hybridz.org/index.php/topic/81941-exhaust-tube-sizing-i-did-your-arithmetic-for-you/

[ajmcforester]

OK their are a lot of miss under standing out their on how exhaust systems work. I even heard that tuned headers use the sound waves to aid in the flow of air.

A well laid exhaust will help in flow, diameter can have an effect on power. lets look at nothing which acts like maximum diameter you will loose power exhaust leaks do the same thing the closer to the engine you are. The ideal setup is to have the pipe expand and gets wider over its length at a set radius. This will help create a flow dynamic that aids in moving the exhaust. This is something I experienced using an exhaust manifold and 2.75" pipe it was slow off the bottom end as the car got into the higher RPM it was faster. I reduced the pipe diameter to 2.25 and the car started faster, but didn't accelerate faster at the higher RPM. Weather this is scavenging or some other affect it is the case.

[surfer.tech]

Ok to clear everything for everyone. This will be my plan. I did talk to another member who does have the fujitsubo Super EX header and it WILL fit a USDM Z. I will combine that with the Legalis-R muffler. So it will be a complete exhaust unit.

I will be keeping my L24 unit and want to use a triple mikuni setup.

The piping will be whatever size the fujitsubo supplies.

Edited December 9, 2010 by surfer.tech

[LeonV]

OK their are a lot of miss under standing out their on how exhaust systems work. I even heard that tuned headers use the sound waves to aid in the flow of air.

A well laid exhaust will help in flow, diameter can have an effect on power. lets look at nothing which acts like maximum diameter you will loose power exhaust leaks do the same thing the closer to the engine you are. The ideal setup is to have the pipe expand and gets wider over its length at a set radius. This will help create a flow dynamic that aids in moving the exhaust. This is something I experienced using an exhaust manifold and 2.75" pipe it was slow off the bottom end as the car got into the higher RPM it was faster. I reduced the pipe diameter to 2.25 and the car started faster, but didn't accelerate faster at the higher RPM. Weather this is scavenging or some other affect it is the case.

This is all anecdotal evidence from your "butt dyno." There is no concrete evidence here. I'm not sure if you read that link, but removing the exhaust pipe will gain power! Look at TonyD's dyno test results in that thread. There's no denying actual proof.

FYI, exhaust and intake tuning is done by pressure pulses, you can call them sound waves, it's really all in the thread I linked. I don't want to clutter up this thread, I just want to point out the myth and that people should not limit their exhaust diameter because of internet anecdotes. The smaller the diameter and the higher the velocity, the more frictional losses you have which equals a loss in power.

OP, post up a vid when you're done, it should sound nice!

Edited December 9, 2010 by LeonV

[ajmcforester]

Look the first thing I mentioned about sound is example of how confused people can get, not fact.

Second I stated you do get higher power on the top end, so yes you can get more. Yet he did not give from start so it is hard to comment on that part and what other mods did he have from stock. I'm sorry you think my test was out of my butt. I might not have had HP and torque numbers and I didn't mention we had set distances with stop watches. That might not be the most accurate, but it can give you a general idea if you went backwards.

The reason I went down to a 2.25" is several people that had worked on these cars since the early 70's had found that out with the 240Z and they had a higher diameter recommendation for the 280Z. This is not exact and their are things you can do to improve flow in the pipe design.

Those guys from that sight you posted explained a point I also made that a pipe that expands in diameter can help flow. That is what the horn like exhaust systems do. The exhaust does need some length, but not the length of the car. That is to aid and vector the exhaust away from the engine. A great example of needing some length is the Ford GT40, they could have dumped it straight out the side, but they made what was later called the web exhaust do to how tangled it was to cram the piping in.

[ajmcforester]

Ok to clear everything for everyone. This will be my plan. I did talk to another member who does have the fujitsubo Super EX header and it WILL fit a USDM Z. I will combine that with the Legalis-R muffler. So it will be a complete exhaust unit.

I will be keeping my L24 unit and want to use a triple mikuni setup.

The piping will be whatever size the fujitsubo supplies.

What size Mikuni's are you looking at? That is an expensive and really nice setup. I wish I could ask more but the time tells me I need to leave to meet the Chinese delegates at work.

[Matt K]

I though Nissan discovered the optimum exhaust size on an L24 was something like 4" back in the early 70's...one reason the BRE cars had twin pipes with trumpets.

Edited December 9, 2010 by Matt K
added link

[LeonV]

Look the first thing I mentioned about sound is example of how confused people can get, not fact.

Second I stated you do get higher power on the top end, so yes you can get more. Yet he did not give from start so it is hard to comment on that part and what other mods did he have from stock. I'm sorry you think my test was out of my butt. I might not have had HP and torque numbers and I didn't mention we had set distances with stop watches. That might not be the most accurate, but it can give you a general idea if you went backwards.

The reason I went down to a 2.25" is several people that had worked on these cars since the early 70's had found that out with the 240Z and they had a higher diameter recommendation for the 280Z. This is not exact and their are things you can do to improve flow in the pipe design.

Not only do you get power in the top end with a bigger pipe, you get it everywhere along the curve. ITS guys with essentially stock engines run 3 inch pipes, they don't lose anything. Look at Tony's dyno results. Properly sized exhaust pipes will not lose any power, but the proper exhaust diameter for an engine is a lot bigger than people think. From Tony's example, proper diameter for his 2L engine were twin 2.5 inch pipes. This is for a 2L engine!

Those guys from that sight you posted explained a point I also made that a pipe that expands in diameter can help flow. That is what the horn like exhaust systems do. The exhaust does need some length, but not the length of the car. That is to aid and vector the exhaust away from the engine. A great example of needing some length is the Ford GT40, they could have dumped it straight out the side, but they made what was later called the web exhaust do to how tangled it was to cram the piping in.

Collector tuning is a completely different subject and exactly what I am getting at. Yes the exhaust does need to be a certain length, I'm not debating that point.

This tuning is dependent upon valve timing, exhaust temps, and tube length. It is done by calculating the time it takes for pressure waves to reflect at discontinuities in the piping and return before the valve closes, effectively scavenging more gases than otherwise possible. The pressure wave reflection bandwidth is increased with a megaphone placed at the right spot in the system, thus expanding the rpms in which an extra scavenging effect occurs.

Now, with a properly done collector for your system, you need to size an exhaust to go all the way to the back of the car and release the gases. This size is bigger than 2.25 inches on a 240Z as shown by many people that have actually dyno tested and compared results.

Here is a dyno sheet from zhome showing a comparison of a 2.5 inch and 3 inch exhaust on an essentially stock L24 revving to 6500rpm. Notice there is no difference between the two. This means that the pipe has been sized correctly. Especially put your attention to the fact that there are NO low end losses when going to a bigger pipe.

The Ford GT40 is totally different subject altogether and apples to oranges if you're trying to compare to a Z. The GT40 has a dual plane crankshaft, where the firing order is uneven (2 from one bank, then 2 from the other. In order to aid scavenging, it utilizes "180 degree" headers which switch the collectors into which one cylinder from each bank route to. Thus the pulses in the exhaust system were even from left to right, and the next cylinder that releases it's burned gases is scavenged properly. The L6 does not need this as it has one bank of cylinders which also fires evenly from the front three to the rear three.

[ajmcforester]

Now I was using a stock non-emissions exhaust manifold, wasn't Tony using headers. Maybe the headers provide the proper distance and diameter needed for the engine to get proper flow. looking at the difference from 2.5-3" their is none on his graph they pulled the same. Now I would not say from two different sizes that their is no impact based on size, I'd say on 2L engine that their would be no impact from size 2.5"-3". I hope you would agree that you can't make an inferences on the differences diameters create on power with only two data points to compare. All I can confer, understanding that if we went infinitely small the car won't run so their would be some type of curve, maybe it peaks maybe not their is not enough data to confer that.

[LeonV]

Now I was using a stock non-emissions exhaust manifold, wasn't Tony using headers. Maybe the headers provide the proper distance and diameter needed for the engine to get proper flow.

The manifold you use has no effect on what the rest of the system does. That's a moot point.

By the way, the results I posted are from a stock 240Z with stock exhaust manifold.

If you have a long exhaust pipe hooked up to your manifold after the collector, you will be losing torque unless the pipe is big enough. What the headers will do is increase power over the stock manifold as they generally scavenge a bit better. There are dyno results on this as well.

looking at the difference from 2.5-3" their is none on his graph they pulled the same. Now I would not say from two different sizes that their is no impact based on size, I'd say on 2L engine that their would be no impact from size 2.5"-3". I hope you would agree that you can't make an inferences on the differences diameters create on power with only two data points to compare. All I can confer, understanding that if we went infinitely small the car won't run so their would be some type of curve, maybe it peaks maybe not their is not enough data to confer that.

Exactly! No difference going from 2.5 inch to 3 inch. That means there is no loss of low end when going with a bigger pipe. Why does it matter whether it's a 2L or a 2.4L? How else can you analyze those results? I don't understand why you can't accept the truth that dyno testing lays out, running the same car, same dyno, and only changing exhaust diameter.

As shown in many dyno tests that once you choose the proper size, you don't gain (or lose!) anything from going bigger. Well you do lose something going bigger than necessary, and that is ground clearance.

Two data points? There are two curves generated, one with 2.5 inch and the other with 3 inch pipe. Plus, other dyno results point to the same thing. This is a heck of a lot more than "two data points."

Two data points would be, say, torque at 4000rpm and 6000rpm. Yes, I agree that if we only had two points to work with then more testing needs to be done. But we have two dyno curves (large collection of data points) from the same car and dyno. I don't see why you or anybody else should still be in denial about this. I understand it is hard to accept something that is contrary to your beliefs, but this is hard evidence. If you can point me to valid dyno results that prove your point, then I will say that it may have some truth to it. But I have never seen results that show that, with everything else held constant, a smaller pipe makes more torque anywhere in the torque curve.

I've discussed many aspects of engine design with a former Formula 1 engineer and he would corroborate the points that I am making, if that makes any difference to anyone. Yes, it's not a Z engine, but it's a 4-cycle engine operating on the same exact principles.

I hate to be cluttering up this thread, but I hope that this is informative to at least one person so that I'm not just listening to myself talk (type?).

[SSS-S30]

That's the one! It definitely is sweet sounding, especially with the triples.

I would love to hear how it sounds. Is there a youtube video anywhere on the web of the Legalis-R system or where you able to hear it in person?