Leon

Best answer ever.

No problem! I've been working on a resonance tuning spreadsheet based on Heywood's book, all I need to do at this point id take accurate measurements of my actual setup to see if the numbers come out right. I think the Cannon manifold is as long as it gets, as far as triple carb manifolds go. Long air horns will give you more low- and mid-range but make sure you don't shroud them.

I wish they were fictional losses! Yes, I understand the relationship of velocity to momentum. My point is that people tend to focus completely on velocity, not realizing that frictional losses are present, not to mention that they increase with the square of velocity. I mentioned this in the exact line that you quoted. Here's how it works, in a nutshell. The engine is essentially a pump with the air (and fuel) as the working fluid. When talking about frictional and velocity effects, we must speak in the same units of measure (e.g. don't compare momentum to pressure). A good way to go about this is using Bernoulli's energy equation. Pressure losses depend on V2, with the rest of the numbers being constants (pipe length, diameter, friction factor). Dynamic pressure, i.e. the pressure contribution from velocity, is also dependent on V2, with the constant being density. In fact, frictional losses is what our engine (pump) must fight against. These are the so-called pumping losses, and they're responsible for preventing 100% VE at all engine speeds. Clearly, the effect is greater at higher engine speeds, and actually overshadows the ram effect even at high speed. Heywood's "Internal Combustion Engine Fundamentals" has a fantastic graphic showing this, Figure 6-9. The air filter, throttle valve and intake valve are the big losses, but don't disregard the friction in the runners. Plus, the throttle valve size is dependent on runner diameter! There is also an interdepenence of resonance tuning and pipe length, and thus friction. To take the biggest advantage of resonance, you'd have to tune to the first harmonic, giving you in the range of 5 foot long intake runners. This clearly increases frictional losses, especially if there are bends in the 5 foot long intake pipe. Friction is always a consideration and is not to be tossed aside as if its contribution is "magnitudes" less than dynamic pressure. This is simply not true. In fact, this is the biggest design challenge to an engine designer. Fuel and spark are easy, but getting as much air into the cylinder as possible is what's difficult. Another key point you must realize is that resonance tuning is not the same thing as "ram" (intake inertia) tuning! The principles on which these phenomena operate are entirely different. Resonance tuning uses pressure waves (as I discussed in some detail), and ram tuning utilizes momentum/dynamic pressure. What you are talking about (ram tuning) depends on air mass, and how much of it rests in the intake runner waiting for the intake valve to open. In my highway analogy, ram tuning depends on the amount of cars and resonance tuning depends on how long the line is. Summing this up, resonance tuning drives runner length and ram tuning drives runner volume. It is imperative to have a solid understanding of this. One last caveat on resonance vs. ram tuning is that ram tuning only has an effect at high rpm, where there is enough air velocity. This means that in order to take advantage of ram tuning, valve duration must be increased, which then hinders low-speed opertion. Resonance tuning can be tailored to any valve timing/duration without that compromise. In regard to your taper questions, I'll answer in the same format that you used: I've basically answered this earlier. That is not true, a taper does not and cannot "fight" frictional losses. Not really, a straight runner would prevent flow separation as well. Somewhat, yes. This is one of the compromises of a "wet" intake runner. A direct-injected or port-injected engine design does not have to worry about fuel in the runners, thus you can go bigger (and more creative: think BMW's variable-runner systems of the past, a prime example of using resonance tuning!) without having the side-effect of more wetted runner area (larger Tau layer). Having to keep fuel atomized presents a compromise only when speaking about TBI or carbureted engines. As far as theory goes... As mentioned, a wave gets reflected at a discontinuity (diameter change). A straight, open pipe has one discontinuity, which is located at its exit. Now, if we add a step in the pipe such that the diameter changes to a bigger pipe before exiting, we have 2 discontinuities. The pressure wave will still travel the length of the pipe, but now there are two reflections at two distinct lengths (at step and at end). However, these reflected waves will now be smaller in amplitude. This decreases the magnitude of the resonance effect, but now stretches it out to 2 distinct engine speeds. Look at the taper as an infinite series of steps. At each point, the diameter is getting bigger in infinitely small steps. The wave travels the length of the pipe, but gets reflected at each point along the taper. The longer your taper (more steps) the more you decrease the amplitude, but broaden the range. As with anything, it's a trade-off! Your overall goals determine whether you value amplitude (peakier torque curve) or range (wider, but less pronounced torque curve) more. Yes, 7 degrees of taper is close to maximum before you get flow separation in the intake, thanks for mentioning that. The overall goal of a properly designed intake is to minimize losses while extracting as much performance as possible. Resonance tuning and ram tuning both aim to achieve this, while working against flow reversion, charge heating, and friction. References: (1) Internal Combustion Engine Fundamentals by Heywood (2) Introduction to Fluid Mechanics by Fox, McDonald and Pritchard

Dangit, Bill! I'm in the area tomorrow, and you're going skiing? Glad to hear you guys found the issue, I'm looking forward to seeing your Z sometime!

I have Eibachs on my 260Z and get some kickback if I hit a bump mid-corner when driving spiritedly. However, the early 260Z gets a slightly bigger front drop with the Eibachs (unique front strut housing). You won't notice a thing in everyday driving.

Then, the next thing to do would be to verify float level using clear tubing attached to the bowl outlet as a gauge.

The water pump intake is also right above the alternator, check that as well.

Some shiny wheels, or some sweet poly bushings, or, or an air dam! Then strip the car and have it sit on jackstands, indefinitely. In all seriousness, my point is don't get caught up in appearances or "performance" parts. Figure out what it needs the most and get it done.

My bet is on the nozzles sticking in the down position, allowing too much fuel past the needle. Remove the nozzles, clean them up and they should be okay, unless something is seriously wrong.

Bingo...

Your post adds some info that I purposefully left out of my post in the other thread I linked above. Otherwise, I'd start to approach dissertation status. I didn't go into harmonics, and yes, the third harmonic is the one we usually go for without having bosuzoku intake pipes. Our posts make for a good match, a nice combo of theory and application!

Maybe the long post I just made in another ITB thread will help! It probably would've gone here anyway, if I saw this post first. http://forums.hybridz.org/index.php/topic/105783-ideal-intake-runner-taper/page__view__findpost__p__989770 I guess I might as well copy/paste some of it over here... So, why taper the runners? It's all about resonance tuning. Well what the hell is resonance tuning, you may ask! When your intake valve opens, the mixture begins to flow into the cylinder. This propogates an expansion wave up the intake tract. Think of it this way: the intake runner is a 4-lane highway, the valve is a traffic signal, and the cylinder is a mall parking lot after the signal. The cars on the highway waiting for the light represent the air-fuel molecules. When the traffic signal turns green (valve opens), cars begin to flow into the parking lot (cylinder). Looking down at the highway (intake runner) with a bird's-eye view, you can see the front-most cars moving first and creating a gap between themselves and the cars behind them. Keep looking down and you'll see that this gap travels down the line of cars on the highway until it reaches the last car and the last car begins to move. This is your expansion wave propogating up your intake tract! Wave dynamics state that if a wave travels through a pipe and hits a discontinuity (a change in diameter, like the end of a pipe) then it is reflected back down that pipe with the opposite effect (negative to positive - an expansion wave gets reflected/inverted as a compression wave). Let's get back to our traffic analogy where we left off, imagine that the reflection happens when the wave hits the last car in line on the highway and it begins to move. The line of cars has now expanded after the light turned green, so the last car in line will work to compress it. So, the last car in line gasses it and rams the car in front! They now go down the line, ramming each car in front of them until they've compressed themselves into a big hunk of metal upon reaching the parking lot (cylinder). This is the compression wave reflecting down the runner and squeezing back into your cylinder! This compression wave increases intake pressure, which fills more of the cylinder (an increase in "volumetric efficiency"), which is what ultimately increases engine torque. Silly analogies aside, those are the fundamentals. Back to our intake and cylinder, we can see that it takes time for the expansion wave to travel up the intake, reflect, and travel back down as a compression wave. In order for our intake to be "tuned", the compression wave must reach the valve just before it closes so that we can squeeze in that last extra bit of air-fuel mixture without reversion of the mixture back into the intake. You can see now, the connection of intake tuning to valve timing and intake length. The longer the intake runner, the longer it takes for the compression wave to travel back to the valve. This means that when you increase runner length, your tuned rpm drops to a slower engine speed, where the wave has enough time to get back to the valve. If you change your valve timing, e.g. closig the intake valve later, then you raise your tuned rpm to a higher engine speed since the wave now has extra time to get back to the valve before closing. What does this have to do with intake taper? Think back to the expansion wave hitting a discontinuity in the pipe. A discontinuity causes an inverted reflection of the wave. If your intake is straight from air filter to valve, you get one big, fat reflection but only at one discrete engine rpm. At other engine speeds, the timing of the reflection will be off. This gives your torque curve a pronounced peak but no benefit from intake tuning off that peak. What a taper in the pipe does, is introduce a bunch of tiny, little discontinuities along its length. Meaning, as the wave travels through the taper, the diameter is continuously changing. This allows some of the wave to be reflected back down the intake, while the rest of it keeps moving out. What you have now is a series of smaller reflections but at a broader range of engine speeds. This results in a less peaky but more flat and robust torque curve. From what we've discussed here, it can be seen that a short, agressive taper will make the reflection stronger but last for a shorter span of rpm. The opposite goes for a shallower, longer taper (broader tuned range, but with a smaller bump in performance). Taper location also plays a role, once you think about it. Since the wave takes time to travel up and down the intake runner, the further you space the taper away from the valve, the longer it will take for the expansion wave to reach the discontinuity. This allows you to "activate" your taper at different rpm. If you start the taper further out from the valve, then you delay relfection, which then shifts your torque curve down. At higher rpm, the compression wave simply won't have the time to reach the valve before it closes. In conclusion, there is no ideal intake taper! You must figure out your design intent (peaky or flat torque curve; low, mid or high end torque) from which ideal runner size can be found. Sorry for the long post, but I felt compelled to give a more thorough answer. Hopefully, you can get some benefit out of it!

That is plain wrong and frankly, terrible advice. Why retain a restriction? A restriction is just that, something that hinders flow. So many people develop a vexing fixation on velocity, but I just don't get it. Why? Frictional losses increase proportionally with the square of velocity! This is bad. Rather, look at pressure. The more pressurized the intake, the better your cylinder is filled (higher volumetric efficiency), which boosts the amount of torque your engine can make, therefore we want to maximize intake pressure. Now, velocity does affect pressure (dynamic pressure), but with the side-effect of increasing frictional losses (pressure drops) in the intake. As you can see, there is a fine balance between the two where optimization is needed. Trial and error can determine the balance, but that involves making many iterations of intakes varying runner diameter and testing to see which one best matches your goals. However, changing runner diameter also changes your tuned rpm, so you're playing with multiple intertwined variables here. Let's forget about the restriction nonsense, and focus on intake design and taper. Your idea on tapering down to the head is better than putting a restrictor into the intake. The head port is still a restriction (not a good thing!) but there are compromises there that we cannot avoid (packaging). So, why taper the runners? It's all about resonance tuning. Well what the hell is resonance tuning, you may ask! When your intake valve opens, the mixture begins to flow into the cylinder. This propogates an expansion wave up the intake tract. Think of it this way: the intake runner is a 4-lane highway, the valve is a traffic signal, and the cylinder is a mall parking lot after the signal. The cars on the highway waiting for the light represent the air-fuel molecules. When the traffic signal turns green (valve opens), cars begin to flow into the parking lot (cylinder). Looking down at the highway (intake runner) with a bird's-eye view, you can see the front-most cars moving first and creating a gap between themselves and the cars behind them. Keep looking down and you'll see that this gap travels down the line of cars on the highway until it reaches the last car and the last car begins to move. This is your expansion wave propogating up your intake tract! Wave dynamics state that if a wave travels through a pipe and hits a discontinuity (a change in diameter, like the end of a pipe) then it is reflected back down that pipe with the opposite effect (negative to positive - an expansion wave gets reflected/inverted as a compression wave). Let's get back to our traffic analogy where we left off, imagine that the reflection happens when the wave hits the last car in line on the highway and it begins to move. The line of cars has now expanded after the light turned green, so the last car in line will work to compress it. So, the last car in line gasses it and rams the car in front! They now go down the line, ramming each car in front of them until they've compressed themselves into a big hunk of metal upon reaching the parking lot (cylinder). This is the compression wave reflecting down the runner and squeezing back into your cylinder! This compression wave increases intake pressure, which fills more of the cylinder (an increase in "volumetric efficiency"), which is what ultimately increases engine torque. Silly analogies aside, those are the fundamentals. Back to our intake and cylinder, we can see that it takes time for the expansion wave to travel up the intake, reflect, and travel back down as a compression wave. In order for our intake to be "tuned", the compression wave must reach the valve just before it closes so that we can squeeze in that last extra bit of air-fuel mixture without reversion of the mixture back into the intake. You can see now, the connection of intake tuning to valve timing and intake length. The longer the intake runner, the longer it takes for the compression wave to travel back to the valve. This means that when you increase runner length, your tuned rpm drops to a slower engine speed, where the wave has enough time to get back to the valve. If you change your valve timing, e.g. closig the intake valve later, then you raise your tuned rpm to a higher engine speed since the wave now has extra time to get back to the valve before closing. What does this have to do with intake taper? Think back to the expansion wave hitting a discontinuity in the pipe. A discontinuity causes an inverted reflection of the wave. If your intake is straight from air filter to valve, you get one big, fat reflection but only at one discrete engine rpm. At other engine speeds, the timing of the reflection will be off. This gives your torque curve a pronounced peak but no benefit from intake tuning off that peak. What a taper in the pipe does, is introduce a bunch of tiny, little discontinuities along its length. Meaning, as the wave travels through the taper, the diameter is continuously changing. This allows some of the wave to be reflected back down the intake, while the rest of it keeps moving out. What you have now is a series of smaller reflections but at a broader range of engine speeds. This results in a less peaky but more flat and robust torque curve. From what we've discussed here, it can be seen that a short, agressive taper will make the reflection stronger but last for a shorter span of rpm. The opposite goes for a shallower, longer taper (broader tuned range, but with a smaller bump in performance). Taper location also plays a role, once you think about it. Since the wave takes time to travel up and down the intake runner, the further you space the taper away from the valve, the longer it will take for the expansion wave to reach the discontinuity. This allows you to "activate" your taper at different rpm. If you start the taper further out from the valve, then you delay relfection, which then shifts your torque curve down. At higher rpm, the compression wave simply won't have the time to reach the valve before it closes. In conclusion, there is no ideal intake taper! You must figure out your design intent (peaky or flat torque curve; low, mid or high end torque) from which ideal runner size can be found. Sorry for the long post, but I felt compelled to give a more thorough answer. Hopefully, you can get some benefit out of it!

Ah, that sucks. I was planning on asking them about that, if I ever needed a new one. Looks stock to me, all stock downpipes I've seen have the piping sticking out from the flange. Now whether it's stock for a 240Z manifold, or 260Z, or 280Z, etc. I'm not sure.

IMO, the biggest reasons for the discrepancies on what "fits" and what doesn't is that it depends on what front valence is used and what exact tire you're using. The Xenon air dam allows for more tire up front compared to the stock valence. Also, there is a fairly considerable variation in size when comparing what seems to be the same tire between multiple manufacturers. Some will be wider, some will be taller, and some will be the opposite or a combo of those. Having said that, I thought I saw a thread before detailing exactly what works and what doesn't with the 16X8 Rotas. FWIW, I had 225/60-14 on a zero-offset 14X6 wheel and now have 225/50-16 on a 16X7 wheel with zero offset (maybe a tiny positive offset, not 100% sure). I've had no rubbing issues on either one, fenders are not rolled.

You could find a used one in the classifieds or the small Z-parts businesses (Z-barn, zparts, Z-Specialties, etc.). A quick search says you can get a brand new, billet spray bar from Larry Hassler at 626-358-2885. From: http://forums.hybridz.org/index.php/topic/102501-spray-bar-mia/

You NEED a new spray bar if you want that engine to run ok much longer! Do not try to repair the one you have if that's what you're thinking.

True, but only if the car is running VERY rich all the time. If you only get soggy at a certain condition, your plugs, exhaust, etc. will appear perfectly fine. My point is, you could be lean or rich, don't assume one way or another without hard evidence. Check all possibilities. My triples are jetted too rich right now. There is no black smoke and plugs look great, but I cruise at about 11-11.5 AFR. Sometimes I even drop below 11 AFR but I wouldn't know it without a wideband. WOT mixture is a bit leaner, maybe 12 AFR and there are no issues with bogging at that AFR.

I'm not sure on how you determined that it is "definitely going lean". Do you have a wideband? If not, then my first thought is that you're flooding the engine with fuel. The SM needles and 5 psi of fuel pressure are the likely causes. The fuel shooting out of the float bowl is a clear sign of this. Make sure your floats are set correctly as well, some SUs had different float heights front-rear depending on year.

There is no "best". Take a look at the exhaust sticky if you want detailed information, but if you want more low end torque then use longer primaries (collect further down) and vice versa for efficiency at higher rpm. I'm doubt there is a huge difference between the factory manifolds, but I don't have enough experience with those to verify. You can play with the 2-1 merge for minor gains at lower or higher rpm, depending on where you put the merge. Exhaust Design Sticky

I believe MSA sells new downpipes with some of their exhausts. I would call and ask, and you have the luck of being local and being able to save on shipping.

$50? I'd give him $20 and hang it on my wall.

No problem, glad to hear that. Nice job!

You're probably not getting enough voltage to the starter solenoid from your wiring. Measure voltage at the spade on the solenoid with a multimeter and have someone turn the key. I don't remember the exact excitation voltage needed at the solenoid, but over 10V should get it going. The solutions are to either clean all connections for the starter circuit or install a "starter relay" (search this). The flywheel has nothing to do with idle quality. Torque = Inertia X angular acceleration If the engine isn't changing speeds (accelerating), e.g. at idle, then it doesn't care how much the flywheel weighs. Everything else points to a vacuum leak. Do the spray test before anything else.

Care to post the answer, to archive for the search engine?