Leon

I swear to god, I'm gonna pistol whip the next person that says "back pressure"! Read the exhaust sticky. FWIW, I like the first video after he added the resonator. Nice, crisp sound. My next exhaust is going to be a 3" single, have 2" duals now (L24).

Right, although that's without taking d into account.

You did the math wrong, again.

Donate $20 to the site and list it in the classifieds here. A good body shouldn't be too hard to sell, probably fetch $400-500 or so depending on condition.

Just a little bit of algebra... You're using: f=nv/2(L+.3d) You have a known frequency (f), speed of sound (v), pipe diameter (d), and the harmonic you're shooting for (n). You want a length of pipe that accomplishes this. This means solve for L: Multiply both sides by (L+.3d): f(L+.3d)=nv/2 Divide both sides by f: L+.3d=nv/2f Subtract .3d from both sides, and voila: L=(nv/2f) - .3d Then as they say, "plug and chug". n=1 is 1st harmonic n=2 is 2nd harmonic n=3 is 3rd harmonic ... [edited typo]

FWIW... Flow=571.3CFM @ 7000RPM As I thought, you were using the percent value for VE instead of actual VE (decimal).

The higher the rpm, the higher the CFM, the LOUDER the sound. There is no formula relating CFM to frequency, as we've said, that doesn't make sense. The amount of air flowing through the pipe will change its volume (or "amplitude" as zero already mentioned), not frequency. You make it sound easier than it really is. There are a bunch of waves interacting with each other, especially in a multi-cylinder engine. How are you going to deduct a given frequency from before the X-pipe to after? In other words, how are you going to relate what the engine is doing to what's coming out of the end of the pipe? As zero already mentioned, differing lengths of primaries will cause the waves to reach each other at different times thus resulting in a different (average) frequency. I covered this in my first reply. N represents the harmonic that you're calculating, e.g. N=2 to calculate the 2nd harmonic. I don't really get what you're doing here. Aren't you trying to solve for frequency (f=261Hz)? In that case, to get the middle-C frequency of 261Hz, the length of pipe needed in your example would be 25.5 inches (.65m). Secondly, I think you made an error in the calc you did. With speed=343m/s, L=1m, and d=0.0254m, f=170Hz. Since N=1, this is all based on the first harmonic.

Nice, I was just about to post that. Fifty-seven thousand CFM would be a pretty good flowing engine... I bet vega used VE% instead of actual VE in decimals since the calculated number is two orders of magnitude too big, i.e. VE=90 instead of VE=0.90. Vega, I'm not sure if you're approaching this problem from the correct angle. CFM and pipe composition are not directly tied into the natural frequency of the air passing through the pipe, meaning that changing the CFM through the pipe is going to change the volume of the sound but not the frequency at which it resonates. As zero mentioned, the composition of the pipe is tied into the natural frequency of the pipe itself, e.g. a tuning fork. What matters more, in terms of exhaust design at least, is pipe length, valve timing, RPM, and exhaust temperature. This is the same thing as discussed in the sticky: exhaust resonance. It looks like you're looking for a specific sound instead of a performance gain. The concepts are the same, except now you're going from known specs to a required frequency rather than the other way around. [EDIT: Damn! Took too long to post, zero covered some of this already.]

Oh man, that is freakin' fantastic!!!

As an aside, I'd recommend Megajolt for spark control since you're wanting to run Webers. MS only makes sense if you plan to go EFI later.

There are tons of old L-series in the Sacramento area, and Bay Area as well. It will be easier and cheaper in the long run to just swap an L in. A cheap, wonky, hastily-done V8 conversion probably won't fetch much from what I've seen.

Nicely laid out, zero.

What are you trying to accomplish? In the given formula, n (the integer) represents the "resonance node" as they called it. A lower number means a lower frequency, i.e. harmonic. n=1 is the "base" resonant frequency, aka the first harmonic. Also, temperature has a fairly large effect on the speed of sound through air, but there are tables and formulas that are easily available to calculate that.

Look around on CL, there are often people cutting up their cars. See if you can find someone with a good panel, or even post a WTB ad here. If you're worried about valves sealing to the seat, you can lap them yourself. Just be gentle, there's no need to remove a ton of material. Verify straightness and you're set. Shoot, 65deg is beach weather. I heard that the temps were a record high for Long Beach, you valley-dwellers are nuts! I was dripping sweat just standing there. I did get it clayed, buffed and waxed and the paint looks so much better. I got lucky in that I called up an auto detail shop in SLO (Central Coast Auto Spa; loved these guys. If you need a detail in SLO, go to them ) and got it in that same day, on the Friday before the show. Still haven't had time to look at my photos, I'll try to make time tonight...

Unfortunately, I don't have that lower body piece. Maybe Tabco makes on? I do have stock L24 valves from my E31 head, but I'm not sure if I'll need them or not. I could possibly pull some from my extra heads, but time is not on my side right now! You may be able to find some pretty cheap, there are bound to be some sources online. JCCS was awesome, even though it was hotter-than-hell (~100deg)! I just haven't had a chance to post my pics up, let alone look at them yet. The 260Z miraculously took 3rd in "Best Z" (exc. 240Z) category!

I remember a guy getting his 280Z painted at a shop in the Easy Bay somewhere, sounded reputable and his car looked good even though it was done on a lower budget. Search around for local body shops, I bet you'll find one that fits your needs. Found the one I was thinking of: http://www.classiczcars.com/forums/thread41992.html

Nice job, Matt! Looks like you are on your way.

Nice, is it driveable now?

Beautiful work, it's coming together very nicely!

Ray, The ones with the tab on top are likely 280Z 5-speeds and the ones with the tab below (6 o'clock) are the ZX units. There are other clues like the exhaust hanger ears underneath the shifter (2 means 280Z), the shifter bushings (ZX shifter has big, yellow plastic insert), and fill plugs (right side is late ZX, AFAIK).

Thanks Brady! Your turn!

Might as well post a dyno vid! This was the first run of the day, to set the new baseline comparing the old and new exhaust.

Thanks again Ben, it's been an absolute pleasure dealing with you! I finally used the lights at night a few days ago and what a difference. I'll see you on Saturday at JCCS!

It went well! Picked up about 10lb-ft and 10hp peak, and gains across the board! I ran it for about 2 hours and was heat soaked towards the end, so we shut it down. I really need a heat shield. I'll have to plot the results up in Excel later. Probably the biggest advantage of the MJ is the part-throttle cruise torque. I picked up gobs of torque at partial-throttle, gas mileage will considerably increase and throttle transitions have gotten crisper. Cruise and around-town driving requires less throttle. The other advantage of MJ is setting up idle. By slightly retarding timing at idle, and advancing it at lower and higher RPM, the idle has become more stable. I love the MJ, nothing like sitting in the car, on the dyno, pressing CTRL UP and seeing torque increase as you up the advance. Centrifugal weights, springs, advance slots, spark scatter? What's that?

The '72 110 cars were available with either black or white interior, not just white. White interiors are definitely less common than black.