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Dual injector factory manifold?


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Good move getting rid of that antique 4-barrel.

 

That manifold will work pretty well if you can stage the injectors with your EMS - Good low speed running on the primary injectors only, increased fuel delivery on both sets.

 

2 possible limitations:

 

1. The stock intake runners have pretty small inner diameters - probably good to 350-400 whp but will limit airflow at the top end.

 

2. Your injector choices are somewhat limited by the hose barb rails and flange mounting arrangement. A conversion to the o-ringed variety will enable a better choice of affordable injectors.

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Interested on info as well, very cool.

 

I ran an 8inj setup on my other car (turbo 4cyl) with lots of success, big fan of these setups. On more modern EFI setups at least, it was great having stock like drivability and reliability off boost with a secondary injector controller picking up the slack when your in boost. I was running 26psi through a holset HX40 on a 2.0L motor on pump gas still using a factory non-turbo ecu and a 034 Motorsports EIC in my other car.

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I won't touch the intake with a 10' pole not because it's not cool, but because the angle of the second batch of fuel injectors is not designed well from a function standpoint, just looks cool. The spray pattern of the nozzle will just rebound and gel on the walls of the intake runners which makes for a rough/crappy idle. Better off running a single bank of 6 injectors sized properly for the target horsepower in mind. If were talking approx 350-400rwhp then we need to be talking 550-600cc fuel injectors of decent quality. Preferably a more modern o-ring interface to clean things up a bit.

 

 

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I won't touch the intake with a 10' pole not because it's not cool, but because the angle of the second batch of fuel injectors is not designed well from a function standpoint, just looks cool. The spray pattern of the nozzle will just rebound and gel on the walls of the intake runners which makes for a rough/crappy idle. Better off running a single bank of 6 injectors sized properly for the target horsepower in mind. If were talking approx 350-400rwhp then we need to be talking 550-600cc fuel injectors of decent quality. Preferably a more modern o-ring interface to clean things up a bit.

 

Not sure about the angle on this specific manifold (never even seen one before), but depending on what your using to control the secondaries, they wouldnt be firing at idle anyways.

 

Secondaries would only come on when needed. For example, in my multi-injector setup, i ran 270cc primaries and 440cc secondaries. The secondaries didnt come on until 3 or 4 psi of boost. At higher rpm or in boost, airflow should help prevent the fuel spray issue from the secondaries, unless the angle is really bad...

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Doesn't it look like the second set of injector bungs is cast as part of the manifold? It doesn't look like a modified stock manifold with welded-on bungs, it looks like a factory casting. Seems like runner size would have been considered to take advantage of the extra fuel.

 

What are the numbers/letters on the top of the manifold that you can almost see in the first picture?

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Very cool set up, I was looking for one of these for ages years ago but couldn't find one. I even thought of giving it a go and making one but never did happen. I first read and saw one in the book by Corky Bell called Maximum Boost.

 

My HP goals have changed now so it's no longer of interest, but great find!! I would have bitten your right arm to own it at one point :)

 

Here's a link to the photo from Maximum boost, courtesy of Atlantic Z clubl28manifold.jpg

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Very cool set up, I was looking for one of these for ages years ago but couldn't find one. I even thought of giving it a go and making one but never did happen. I first read and saw one in the book by Corky Bell called Maximum Boost.

 

That's where I saw that manifold before - thanks for jogging my memory.  The injector angle on the secondaries looks fine to me - right at ~45deg to the airflow and pretty much pointing at the intake port.  What angle did your guy think it should be at?  As was already mentioned you'll only be using the secondaries at high flow conditions anyway, so this should be the best of both worlds.

 

Being able to run stock or near-stock sized primaries does wonders for driveability - that's a really good find!  Now you just need to  convert it to o-ring injectors...

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That is what I thought.  I talked with the p/o and it turns out that he sent the manifold off to Corky Bell years ago and had it modified by him.   So one would think between Corky and the P/o that something would not leave his shop with his name on it without it being a good piece.  

I plan on having MS3 installed on the car to control everything. 

Precision Ball bearing turbo

I will change out the fuel rails and injectors to be of the o-ring variety......

I am also changing to a coil on plug sequincial ignition.  So no dizzy for me!

I will go with how the motor is set up now but a few changes to accomodate for modern technology.  The motor was doing very low 12sec passes in a 280Z back in the day. 

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"1. The stock intake runners have pretty small inner diameters - probably good to 350-400 whp but will limit airflow at the top end."

 

OK, let's be correct here... The stock manifold is not good to " probably" 350-400HP, it's been proven at over 650HP (At various RPM levels with boost of 17, 21, and 25psi)

 

Yeah n they're small, but they DO flow at 190CFM, BETTER THAN ANY STOCK UNPORTED HEAD!

 

So can we PLEASE stop blaming the MANIFOLD in turbo applications when it's the HEAD PORTS that are the problem????

 

L-Head Power has ALWAYS been "in the head"-this doesn't change when huffing the engine!

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  • 2 weeks later...

 

OK, let's be correct here... The stock manifold is not good to " probably" 350-400HP, it's been proven at over 650HP (At various RPM levels with boost of 17, 21, and 25psi)

 

 

Back in the day, with a mildly ported head, I picked up around 25whp with the use of a Thagard intake and retuning to correct the leaner AFRs, with no other changes. This was at the 380--390 whp/20Psi level. I could be wrong, but it looked to me that the stock manifold was beginning to limit flow. If 600+ hp numbers were achieved with the stocker I'm sure we're talking extreme porting to make more than 190 cfm.

 

Looking at the Electramotive 280Zx Turbo GTO car, at 580 SAE net hp, That intake mani is definitely not stock.

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The stock intake, at 32mm ID, is definitely a feature that needs to be addressed. It's not so much the flow rate, as it is the acoustic tuning that is the problem, in my opinion. Torque peak RPM is seriously impacted by the diameter of the runner, and to a little lesser extent the length of the runner. By playing with the runner diameter, peak torque can be moved around, and then once you decide where you want peak torque to occur, you can set the runner diameter based on that. (Hint: for a 176 cubic inch 6-cylinder engine, peak torque will occur around 5300RPM with a 1.76" average runner area, or 5850 RPM for a 1.95" average runner area.) Once runner diameter is set, you can reinforce that by adjusting the runner length from valve head to plenum to narrow or widen the torque band. 5300 RPM would be 2nd wave tuned with an intake length of fifteen and a half inches, valve to plenum.

 

The stock L28 fuel injection intake, with 32-34mm runners, is set up for peak torque to occur between 4000 and 4200 RPM. I seem to recall a characteristic torque curve for turbocharged L28's being mentioned before. The problem is that now the runners should be about twenty inches long to match the length to the torque peak. It is possible to fit this into the bay...that's 16" from the cylinder head to the plenum. Wrap them around an LD manifold or the P65 casting and I bet you're pretty close. I've got a hunch that this length-to-diameter mismatch results in the "5500RPM out of breathness" for the L28ET that is often mentioned. The stock cam is probably engineered to match up pretty well to these characteristics, too.

 

By placing peak torque low in the relative capabilities of the engine, you are sacrificing horsepower for torque. Without making a single foot pound more peak torque, move the peak up 1000RPM and gain horsepower. You can adjust for the move with gearing, if needed.

 

On the other hand, if you are going to stick with the stock gearing...a 4200RPM torque peak would be rather appropriate.

Edited by Xnke
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The stock intake, at 32mm ID, is definitely a feature that needs to be addressed. It's not so much the flow rate, as it is the acoustic tuning that is the problem, in my opinion. Torque peak RPM is seriously impacted by the diameter of the runner, and to a little lesser extent the length of the runner. By playing with the runner diameter, peak torque can be moved around, and then once you decide where you want peak torque to occur, you can set the runner diameter based on that. (Hint: for a 176 cubic inch 6-cylinder engine, peak torque will occur around 5300RPM with a 1.76" average runner area, or 5850 RPM for a 1.95" average runner area.) Once runner diameter is set, you can reinforce that by adjusting the runner length from valve head to plenum to narrow or widen the torque band. 5300 RPM would be 2nd wave tuned with an intake length of fifteen and a half inches, valve to plenum.

 

The stock L28 fuel injection intake, with 32-34mm runners, is set up for peak torque to occur between 4000 and 4200 RPM. I seem to recall a characteristic torque curve for turbocharged L28's being mentioned before. The problem is that now the runners should be about twenty inches long to match the length to the torque peak. It is possible to fit this into the bay...that's 16" from the cylinder head to the plenum. Wrap them around an LD manifold or the P65 casting and I bet you're pretty close. I've got a hunch that this length-to-diameter mismatch results in the "5500RPM out of breathness" for the L28ET that is often mentioned. The stock cam is probably engineered to match up pretty well to these characteristics, too.

 

By placing peak torque low in the relative capabilities of the engine, you are sacrificing horsepower for torque. Without making a single foot pound more peak torque, move the peak up 1000RPM and gain horsepower. You can adjust for the move with gearing, if needed.

 

On the other hand, if you are going to stick with the stock gearing...a 4200RPM torque peak would be rather appropriate.

 

I've not heard of that method of intake tuning.

 

Length is the critical feature here, with diameter being secondary. Wave tuning depends on tract lengths, because it's the wavelength (and travel time) that determine a "tuned" rpm. I'm not sure what you're going off of, but a tuned length at 5300rpm would be more like 27 inches for the 2nd harmonic! Because of size constraints, intakes (and exhaust manifolds) are typically tuned for the 3rd or 4th harmonic. I've dumped a bunch of info on tract tuning on this site if you want to delve deeper.

 

Once you have a tuned length, set the diameter big enough as to not choke the flow but small enough as to maximize the kinetic "ram effect" at high RPM.

 

Valve timing changes the amount of time the wave has to travel inside the intake. Longer valve open times give the wave more time to travel down, reflect and come back to the intake valve, so the resonance tuning gains are realized at higher RPM, and vice versa for shorter duration.

 

Oh, got a bit off-topic didn't we...

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Just a bit. The problem with your theory of length being the predominate factor doesn't jive with the results I have seen, both in the Z and in dozens of other cars. The manifold lengths seem to be whatever packaging constraints demand, with a trend towards longer runners, but universally the runner diameter-engine displacement method predicts the torque peak with much greater consistency. I'll have to do more research. As for the runner length, I've been using a simplified version of the Chrysler formula, which is supposed to generate a second-wave reflection length based on torque peak desired and intake valve timing.

Edited by Xnke
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Back in the day, with a mildly ported head, I picked up around 25whp with the use of a Thagard intake and retuning to correct the leaner AFRs, with no other changes. This was at the 380--390 whp/20Psi level. I could be wrong, but it looked to me that the stock manifold was beginning to limit flow. If 600+ hp numbers were achieved with the stocker I'm sure we're talking extreme porting to make more than 190 cfm.

 

Looking at the Electramotive 280Zx Turbo GTO car, at 580 SAE net hp, That intake mani is definitely not stock.

More bad or misleading information!

 

The manifold I'm referring to is stock, with extrude honing ONLY. Diameter of the runners isn't even the FIA-Homogolation Legal 35mm, rather a polished 32 mm stocker diameter. The power quoted was at the rear wheels, and was achieved between 6800 to 7200 rpms, depending on the boost being used.

 

The quoted Electramotive numbers are publicity-only figures, nowhere near what it made. That car utilised a Nissan Comp Triple Manifold (so did the head above using the stock manifold, it's how the inferences were quantified...same porter who did the Electramotive Head in the GTO car, did this head as well...) the Electramotive car made 1,100hp with around 30psig using first generation fuel and ignition controls. For most races it was runnin closer to 740 HP, depending if they needed to make time.

 

If you actually PORT the stock manifold, it flows more than 190cfm per runner. The 190 was an extrude-honed stock diameter, and it's not a limitation at 650/72~7,400 rpms... Other than it could flow as much as the port (225 CFM)... But when you're making 650hp at 17psi of boost it ones your eyes to some paradigms that aren't necessarily true!

 

(EDIT) Oh, and to address something stated above, during low-boost setting testing, this engine had a torque reading of 380ft-lbs at 4,500 with 8.39psi boost... The 5,500 "out of breath" phenomenon is PURELY a CAMSHAFT FUNCTION!

Edited by Tony D
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Just a bit. The problem with your theory of length being the predominate factor doesn't jive with the results I have seen, both in the Z and in dozens of other cars. The manifold lengths seem to be whatever packaging constraints demand, with a trend towards longer runners, but universally the runner diameter-engine displacement method predicts the torque peak with much greater consistency. I'll have to do more research. As for the runner length, I've been using a simplified version of the Chrysler formula, which is supposed to generate a second-wave reflection length based on torque peak desired and intake valve timing.

 

Both length and diameter play a role. I've helped design and test intake and exhaust pipes and the results corroborated the theory. Length is a great predictor of torque peak. I can see diameter playing a larger role if you're using Helmholtz theory which is based on overall volume (length and diameter dependent). Generally speaking, altering runner lengths to change torque peak and altering diameter to maximize the ram effect but minimize pumping losses is the more logical way to design the system, to me at least. However, as always, there's more than one way to solve a problem.

 

What exactly is the "Chrysler formula", out of curiosity? My model is based on simple wave physics.

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