bradyzq
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Posts posted by bradyzq
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It seems like this is no longer putting the cart before the horse to ask these questions:
What are your plans for engine management, and do you plan to run it in and tune on an engine dyno, or in a car?
Well done, sir!
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You could always get a thread-in O2 bung extender with a 90 degree bend, and angle it wherever you want so that water can never sit on the sensor.
http://s13.postimg.org/iju3yrhmf/689_73_popup.jpg
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Have you checked your grounds?
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Depending on how that head achieved its 38.4cc combustion chamber size, and how your pistons are shaped and positioned, you could still have piston-valve contact if you try the big cam in your engine.
Whitehead has been building and racing Z's for over 30 years. I thnk it's safe to say they know what they are doing.
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I love that kind of solution! You feel stupid for awhile, but the fix is easy and cheap, so that part's a win.
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You could check the spark plugs and see if they're more or less equal in colour. That would point out any cylinder-to-cylinder differences, maybe due to injectors, or not...
Next, and I seem like a broken record to myself regarding this (and I actually do have a turntable that won't go to the end of a record and lift, so it skips and repeats), make sure you have good voltage to the pump. This means good wiring on both power and ground sides, ideally straight from the battery, with the original wiring being used only to trigger a relay near the pump. This is especially important when the wiring in question is over 30 years old!!
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Since your advance curve is programmable, when you next visit the dyno, why not try adding or removing advance and see what happens to power or torque?
It is safer when dealing with an unproven curve to first remove a couple of degrees then test. If torque drops everywhere, then advance the timing on the next test pull. If it _doesn't_ drop, you were overadvanced.
Repeat until you have determined the optimum curve for best torque.
You may, depending on the type of dyno, be able to dial in the vacuum advance curve in a similar way. If the dyno is not able to, then Chickenman's suggestions for doing the vacuum advance tuning on the road should work great.
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Are you also NapaBill, the guy who contributed so much to the Weber thread?
If so, thank you and welcome back!
If not, welcome!
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There are many plug'n'play ECU options for the RB...
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Fifiddy shipped?
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Oh, I know what the answer is. Just stirring it up a bit.lol
Me too, sorta kinda.
I just didn't bite!
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JSM, you may be right, but who knows how many electromotives should have been electramotives?
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Bernardd, I'm sure Tony D could answer that question in a complete and entertaining way.
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Lol, yeah I guess I do!
I'm guessing that some people think they are one company.
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Hi All,
I've got to get this off my chest!
Electramotive with an "a" built and raced Datsuns in the 1980s.
Electromotive with an "o" makes and sells crank triggered ignition and engine management systems.
These constantly get mixed up here, mostly by erroneously spelling the race engineering company's name with an "o."
Electramotive owns a large chunk of Datsun racing history. Let's at least try to spell their name correctly.
EOR. (End of rant.)
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Quick question. You state you have the hose off on your FPR. Does the z31 not use a vacuum/boost source to raise/lower the fuel pressure in accordance with pressure?
I _hope_ that is was off only for base fuel pressure verification.
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It depends how you have your fuel pressure regulator plumbed.
Regardless, though, you should be able to install the gauge immediately before or after that fuel rail. Other places may or may not work depending or regulator placement/plumbing.
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Try free revving to say 3000rpm and measure timing advance. That will give you an idea if things are OK off idle.
Also, if you have an exhaust leak between the head and the O2 sensor, the ecu will add fuel to correct the perceived lean condition.
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Disclaimer: I've never played with a Z31 ecu. Having said that, if you threw a knock sensor code due to it not being connected, it is very possible you're running on a timing map for when the engine is knocking. This would of course kill fuel economy.
Can anyone confirm that these ecus do or don't work this way?
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I don't think TEP or Electromotive have ever been accused of selling crap, so I don't think you can go wrong there.
Buuut, if you are getting the ecu tuned by somebody else, make sure the tuner is comfortable with the ecu.
I have tuned Electromotive ecus and they work well. But so do many others, such as Link (which must be well known in NZ).
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Remember that the K20A2 is an iVTEC motor. Unless you go all out and make your new 6 cylinder K-series head iVTEC, you won't have the wonderful wide torque band they have. They only look peaky because the torque just doesn't fall off, seemingly ever. Check out this dyno graph of that motor with boltons and a tune. 90% or greater of max torque between 4500 and 8000RPM. 80% or more for the whole dyno pull. Heck, the torque PEAK is 1000RPM wide!!
With conventionally timed cams, I would guess you can still get a nice torquey motor, but it won't be as flat a curve.
http://www.av-engineered.com/site/news/224whp160tq-stock-k20a2-dyno-tuned
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I wish 40's were adequate for all applications!
Assuming the carbs are jetted, adjusted, and operating correctly, the extra fuel should be drawn in by pressure delta due to extra airflow. Are you suggesting that the air speed in the center of the venturi, where the fuel is drawn in, keeps increasing, but the overall air volume decreases due to non-laminar flow towards the outside?
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I understand all the improvements in engine breathing are breathtaking. Pun intended.
But what Steve and I are trying to say is that you're running too rich because of too much fuel, not due to a lack of oxygen (air).
For example, in a modern, EFI'd spark ignition gasoline piston engine, if you're cruising along the highway at an AFR of 10:1, would you say that the engine needs more oxygen and you must therefore turbo/blower/nitrous it? Unlikely. You would say that it needs less fuel and remove some in the fuel table.
I was suggesting measuring MAP at WOT to see if pressure starts dropping where you think the choke/stall point may be.
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One or more of us are barking up the wrong tree, no doubt! Haha. Good stuff, learning is underway!
No, I'm not saying the carburetors provide more fuel as the demand for air volume remains the same -- I'm saying the carburetors provide a constant amount of fuel, but when severely restricted, the *mass* flow rate of oxygen doesn't keep up with increasing demands for volumetric flow rate of air. I'm saying the more an intake system is restricted, the less laminar the airflow through a wider operating range. Less laminar fluid flow is less dense, which means less O2 is available for combustion. Same volume of "air" carrying less O2 mixed with the same amount of fuel, and the engine goes measurably rich.
Let's take a step back. The carburetors come in different housing sizes (40, 45, 50) and offer different venturis. The manufacturing and performance industries both recognize that the airflow requirements to realize 150hp through 2.4L are different than realizing 300hp through 3.1L, both in terms of peak power and drivability. The airflow adjustments are with our intake shape and size, the venturis in the case of sidedraft carburetors, do we agree? None of us are talking about having to upgrade our fuel pumps or fuel lines, we only make fuel adjustments with jets. (The air corrector jet is not a "corrector" but a fine, last-stage adjustment; it cannot provide adequate adjustment range if the wrong venturi is selected.)
Practically, if we had a fully-tuned race engine running 50 DCOEs and we were to then place 40 DCOEs on this engine and severely restrict it, I'm here to argue that there is no collection of jets that allow this 40 DCOE engine to have a remotely flat or stoichiometric A/F line ~5000 RPM and above, because the carburetor body does not allow proper venturi selection. It tapers way rich no matter what, making jet selection simply a matter of how early or late (RPM) you want to cross the stoichiometric line (main jet) and at what angle (air correctors). I choose to enter the region lean, and split the difference, knowing it will be going way rich unavoidably.
Why this limit exists is another discussion, and here's my take. Fluid is of course any composition of gas and liquid, a good example being "air." Mixed composition fluid flow through an open system is very, very complex. It isn't simply water through a hose (same in, same out) and it isn't a wing moving through the fluid, or air. It's both and neither. In addition to its static variance in composition, pressure and temperature, fluid does all sorts of hard-to-control things: it can compress and expand, it can speed up and slow down, it can be laminar and dense or turbulent and unpredictable. In subsonic fluid flow, the faster a fluid travels, the more head loss or parasitic loss is encountered (drag or friction, essentially). As velocity and its associated losses continue to increase, the laminar layers of fluid flow are further separated from one another and the fluid flow becomes more and more turbulent and less dense. This means that above and below the one and only one ideal speed (the one speed with the fewest losses for a given set of conditions), as speed diverges further from the sweet spot, *mass* flow rate continues to decrease.
What I don't know, is how far into the turbulent regions of fluid flow we are going. Reversion is a specific form of turbulence. This discussion is much of why I would like to dyno the 40 DCOEs "fully tuned" and then 45/50 DCOEs fully tuned. ("Fully tuned" meaning the best I can do with the limitations of my jets, venturis, emulsion tubes, timing, etc.) The dyno plots would offer some of the data this discussion currently lacks.
Though not quite comparable, similar fluid limitations are also present in pumps, propellers and wings. Cavitation occurs when a liquid can't move as fast as the conditions are asking it to (pressure difference is too great). An aircraft wing also "stalls" when the pressure difference is too great, and the airflow goes from laminar to turbulent. You could think of stalling is to gases what cavitation is to liquids if it's helpful, I certainly do. Liquids and gases are both fluids, and both fluids respond unfavorably to excessive pressure differentials.
I submit that with small enough straws and big enough slugs at a high enough RPMs, the airflow stalls / cavitates as the flow goes from laminar to turbulent. This stall would be occurring I suppose in a toroid shape across the plane of the venturis and the stall would probably extend for several centimeters downstream before recovering to more laminar flow, but that's just theory of course. The molecules simply can't get into the hole fast enough, and since a gaseous mixture is compressible they end up fighting each other on the way in. This allows fewer total molecules through the door, just like a panicked room full of people relative to an orderly group. No really, it's for your health, people: try and stay calm.
It's like the opposite end of peeling out, but through your air intake system (the first molecules from world to car) rather than mechanical power output (the first molecules from car to world). You tried to access/wield more force than physics would accommodate. "You suck too fast, you drive slow now."
When fluid flow can't keep up, all bets are off. In supersonic fluid flow this manifests by all relationships becoming inverted (venturi principle is inverted). I'm not suggesting supersonic velocities are reached in our intake systems, I'm simply highlighting that you can't put fluid into a single conceptual box, or it will find a way to spring a leak and remind us that we're still figuring fluid out more and more every year. That's why fluid is also a verb; nothing else behaves like it. The moment we make a rule for it, we need to provide rules for its exceptions, which we normally haven't discovered yet.
Sounds a lot like the laws of man, but let's leave the politics out of it! Haha!
Cheers, fellas. However this fog lifts, let's clear the air!
Wow, had to read that one a few times!
We will learn whatever is hidden up in those trees.
I suggest that ALL the principles behind a working carb are volume, not mass, based, at all times. So, density changes are not directly tunable without changing parts (jets, etc.). I also suggest that you will not be able to strip the oxygen out of the air under any conditions encountered in a carb.
Air volume flow will remain proportional to mass air flow for any given set of atmospheric conditions at the carb inlet.
And mass air flow should be proportional to power.
And since the venturi is not changing size, power is proportional to air speed though the venturi.
And air speed will be proportional to pressure drop through the venturi.
Pressure drop at the venturi should be proportional to fuel flow if there was only one jet and nozzle.
So, based on that, kinda sorta, if the engine keeps one getting richer and richer, it's because more and more fuel is getting drawn into the carb by higher and higher airflow. Have you measured vacuum in the intake manifold at WOT at higher engine speeds? That would help tell you if the carbs were really a "severe restriction."
EDIT: Basically, this is stating what steve260z said a couple of posts up, but in a much less efficient way....
EDIT#2: Errr, it's my description that's the less efficient of the 2.
Twin cam head for the L6 from Derek at Datsunworks
in Nissan L6 Forum
Posted
Wow that is elegant! Inspired by mechanical injection systems?