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Injector bung location on custom manifold


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#1 KidandhisCar

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Posted 07 September 2016 - 11:02 AM

Hoping to soon be building an intake manifold.(l28 P90 head) My question is how detrimental is it that the injector bungs
Be made into the flange?

If i can get away with using 1/2 plate as the flange and just placing the bungs on the runners as close to the flange as possible, will this severely affect performance?

If needed ill buy 1in aluminum bar,and have the edge milled down so that the injectors will we still sit right over the intake valves.

Thanks guys

#2 jthom5147

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Posted 07 September 2016 - 11:23 AM

As far as detrimental, or severely affecting performance... I can't comment as your definition of detrimental or severe would likely be different than mine.

 

Manifold design affects performance... runner length, flow dynamics, etc. On carb'd cars the runner length changes performance aspects in the amount of time the air-fuel mixture has to atomize/homogenize before entering the cylinder. I would imagine that longer atomization  time > more homogenous intake charge = different performance to the effect of better ignition / burn rates. I would call that improved performance. Longer runners might have tradeoffs.... like decreased throttle response. Or if such principles would apply to an injection system which inherently atomizes the fuel?... I don't know.

 

However, there are many examples of engines with injectors away from the cylinder head / valves: there are ITB EFI manifolds available for L series engines with such a design. There are other motors which use single or batched injection of the fuel charge near the throttle body.


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#3 KidandhisCar

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Posted 07 September 2016 - 11:58 AM

The only thing i can think that would need to be different is when the injecotrs fire in relation to when the intake valve opens.
They would have to "fire" earlier,to make up for the time it takes the fuel to travel the longer distance to the intake valve correct?

#4 Josh280z

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Posted 07 September 2016 - 12:35 PM

My thought on the subject(maybe wrong) if you are using the stock efi it won't matter too much because the stock efi runs the injectors in batch. However, if you are using a standalone you may have to get them to open on earlier as kid has mentioned.

 

As far the plate goes I believe the stock flange is something like 10mm. So, it wouldn't be that much further away than if you were to leave it stock, however the 1/2in is still bigger than the stock flange.

 

Why not places the holes on the flange and eliminate some headache or heartache.

 

Also you have to make the intake flange thickness match the exhaust flange thickness otherwise you will get leaks(vacuum, exhaust or both).

 

Hope this helps. I've maybe not ripped apart as many as some people here, though I've read enough and done enough stupid things to not listen to people who have been there before me.


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#5 KidandhisCar

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Posted 07 September 2016 - 01:05 PM

As far as i can tell i cant place the bungs directly on the flat bar flange bc they with interesect to much with the runners if im trying to maintain factory injector location (where the pintle points into the notch at the top of the intake port on the head.)

I will be using ms3pro when the time comes.

The bar would be milled down to match the exhaust where the bolts that a hold down both intake and exhaust sit.

The only reason reason for wanting to put the bungs on the runners is simplicity,and cost.

A 1 inch think bar 2 ft long is 52$ average,while a half inch bar 2 ft long is 20$,both not including shipping. And the 1inch bar with have more machineing costs to put the angles face on it,and have the injector seats cut.

#6 Josh280z

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Posted 07 September 2016 - 02:33 PM

Can you weld the bungs on the runners and cut around? I would think that wouldn't be too hard.... Or you could always use the stock flange with injector bungs already in place.

 

Up to you, you are the one fabricating, it's your money.


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#7 jthom5147

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Posted 07 September 2016 - 02:35 PM

Timing of the injectors to the valve events will affect performance. But many standalone fuel control systems use batch firing (megasquirt 1 & 2, 3 if not configured, and others).... which inherently fire fuel based on RPM at controlled pulses relative to the needed fuel charge. Fuel delivery is not instantaneous, and  may overlap valve events on one, but not all cylinders in the batch. MS3 and other standalone control systems with individual fuel delivery timing.

 

Does the stock system independently control the injectors anyway?


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#8 Josh280z

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Posted 07 September 2016 - 02:39 PM

Stock system uses batch fire.


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#9 KidandhisCar

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Posted 07 September 2016 - 03:56 PM

Josh,im an idiot,and dont know why didnt think of that.
I was too caught up in the idea of cutting the bungs to a wedge shape at the end,and tring to figure out the correct geometry to place them where the flange and runner meet.
Your idea is excellent and that is what ill go with, welding the bungs on then cutting to mate mate to flange.ordering flange plate tomorrow so i can get to work,thanks much.

Edited by KidandhisCar, 07 September 2016 - 03:57 PM.


#10 Sam280Z

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Posted 07 September 2016 - 05:10 PM

There is some good discussion of injector placement in this thread and others:

http://forums.hybrid...g/?fromsearch=1

#11 skirkland1980

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Posted 20 September 2016 - 08:28 AM

My bungs are 3" from the head at a 45 degree angle.https://youtu.be/ROpeT76j0lA
:1983 280zx turbo, L28ET, custom cam grind, 96 saab 900 intercooler w/2.50" piping, 3" mandrel bent exhaust, megasquirt II v3.57, 540cc injectors, walbro gsl392 255lph fuel pump, aeromotive regulator, -6 supply lines, custom fuel rail, MSD ignition wires, MSD 8202 coil, homemade boost controller, Garrett TC4305 turbo, 70mm throttle body, Godzilla BOV, Turbonetics wastegate, custom intake, custom turbo header, Cooling Mist H2O/meth injection, 20psi boost, all stock body, stock interior and weld draglite wheels, TH350 trans 4000 stall with B&M 'street stick' shifter and hughes trans brake, nitto nt555R drag radials, best 1/8 mile of 7.53@ 98 mph




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