Intake design for EFI

[seanm]

Have seen noted here and a few other places that if you use a carb style intake that it is hampering the potential of what EFI is capable of. So you can't compare a carb to EFI swap using the same intake. So how is the right intake design developed? Have seen everything from huge plenum short runner to little plenum long runners used on EFI engines along with converted carb style manifolds. How much is there to be gained with a "proper" manifold?

Have helped a friend get an MSII running with lots of phone help from Wes Kiser. (thankfully, he was willing to spend a few hours on the phone to help us dumb rednecks). But still uncomfortable with it all.

Thanks

[shaun callaway]

EFI manifolds tend to be a single plane manifold, and most street setups out there are dual planes.

As far as power wise it really all depends on your combination.

When comparing EFI to carbureation you have to assume the carb is tuned to the best of its ability. If you have the carb tuned the best it will ever be and the only change you make is the EFI the idealy you should see minimal gains in HP. This is also assuming you tune the VE table really well for the motor combo.

I have never seen a loss by changing over.

The first one is always the most difficult they get easier as you do more of them or just keep on the software.

What is cool is when you take a early EFI engine and eliminate the stock computer and use a megasquirt or any other engine managment system. This is where you will see how unefficient factory tunes really are.

The biggest plus to EFI (in my mind) is drivability and reliability. If you need to make a change you bust out the laptop make your change flash you file to the ECM cycle the power and your done. Carbureation requires you to bust out tools. Im not knocking carbs i just dont believe they are as efficient. Believe it or not one day they will be extinct (just my opinion i am not entertaing other ideas right now)

CDMBill is a fine example of high HP carb to EFI.

[dieselgeek]

Have seen noted here and a few other places that if you use a carb style intake that it is hampering the potential of what EFI is capable of. So you can't compare a carb to EFI swap using the same intake. So how is the right intake design developed? Have seen everything from huge plenum short runner to little plenum long runners used on EFI engines along with converted carb style manifolds. How much is there to be gained with a "proper" manifold?

Have helped a friend get an MSII running with lots of phone help from Wes Kiser. (thankfully, he was willing to spend a few hours on the phone to help us dumb rednecks). But still uncomfortable with it all.

Thanks

The more I ask that same question, the more I find I'm not competent to answer it.

The basics are this: carb's require a minimum vacuum signal to operate, and don't like a lot of reversion of standoff (pressure pulses going backwards up through the intake). But you can get away with lots of that on an EFI combo.


Congrats on your first MS2 !!! Wes Kiser is one of the best there is. The second one is always 10x easier than the first one. Will we be seeing homespun EFI on one of your wicked homebuilt Cadillac combos?

[JeffMcKC]

The simple answer is wave tuning, to use the water hammering effect.

The proper intake is always the proper intake.

Where you mount the injector may be a question, but that seems to be forgiving ...... or not depending on just how much your willing to go thru. A carb is a bigger box of worms to get into, with fuel shear and......

[min301]

...mixture distribution.

[seanm]

Thanks fellas,

Just curious of how much there is to be gained from a custom EFI manifold.

The friends truck (2.3T Ford) with the MSII was a challenge and took a few weeks of every night after work and Wes's help for us to get to running condition. Lots of reading and trying to understand the megamanual, etc, etc. That was over a year ago, he mothballed the truck a few days after getting it running. We plan to get it out this spring and learn the tuning aspect of the MSII.
Short vid of truck: http://www.youtube.com/watch?v=VbzFwNWOQ7s

Using EFI on the Cadillac has never been taboo, I understand the benefits of EFI, just the actual/perceived cost of swapping to MPI to feed the pig has deterred me for now. What do you think a throttle body, injectors, harness, fuel rails, weldable bungs for the intake, regulator etc, would cost to support 1000hp or so?

The simple answer is wave tuning, to use the water hammering effect.

The proper intake is always the proper intake.

Where you mount the injector may be a question, but that seems to be forgiving ...... or not depending on just how much your willing to go thru. A carb is a bigger box of worms to get into, with fuel shear and......

So the compromise forced on the intake by the carb is the problem? An individual runner carb set-up, ala weber, would negate most of these problems?

[min301]

So the compromise forced on the intake by the carb is the problem? An individual runner carb set-up, ala weber, would negate most of these problems?



[/quote]


Most from what I've seen, have too short of runners.

[CTX-SLPR]

Its not water hammer, its Helmholtz wave. Water hammer is the inertia of the water column slamming into the closed valve causing a pressure spike in an incompressable fluid so you need a shock absorbing standpipe to allow the pressure wave to expend its energy not breaking the pipes. Helmholtz is resonant wave that is the foundation (though it was really scienced out after) of organ pipe design. Longer runners produce positive resonant waves at lower rpm because the longer wavelength equals lower frequency, ie rpm. The shorter the length of the tube, which includes the intake runner in the head, the higher rpm the resonance will be at. I am pretty sure the NASCAR guys are using the 4th order waves as tuning in their intakes and without the intake height restrictions you could use a "High and Mighty" tunnel ram like the one on it's name sake which would use even lower order waves which would have a greater pressure difference. Your plenum volume will to a large part determine the responsiveness of the engine since a large plenum will react more slowly at lower rpms to changes in inlet constriction than a smaller one just as a smaller tank on your compressor will require the compressor to run more often with a given tool than a larger one. I'm no engine builder but I am a physicist with friends who do work on this kind of thing so I'm going to qualify this as a well educated opinion but not personally demonstrated fact.

[JeffMcKC]

A carb needs a Plenum!!!!!! any N/A motor does, to use the wave to your advantage

[JeffMcKC]

Its not water hammer, its Helmholtz wave. Water hammer is the inertia of the water column slamming into the closed valve causing a pressure spike in an incompressable fluid so you need a shock absorbing standpipe to allow the pressure wave to expend its energy not breaking the pipes. Helmholtz is resonant wave that is the foundation (though it was really scienced out after) of organ pipe design. Longer runners produce positive resonant waves at lower rpm because the longer wavelength equals lower frequency, ie rpm. The shorter the length of the tube, which includes the intake runner in the head, the higher rpm the resonance will be at. I am pretty sure the NASCAR guys are using the 4th order waves as tuning in their intakes and without the intake height restrictions you could use a "High and Mighty" tunnel ram like the one on it's name sake which would use even lower order waves which would have a greater pressure difference. Your plenum volume will to a large part determine the responsiveness of the engine since a large plenum will react more slowly at lower rpms to changes in inlet constriction than a smaller one just as a smaller tank on your compressor will require the compressor to run more often with a given tool than a larger one. I'm no engine builder but I am a physicist with friends who do work on this kind of thing so I'm going to qualify this as a well educated opinion but not personally demonstrated fact.

Hey its a water hammer, call it what you want, its still a valve closing and a wave being made, and the plenum and runner taper and length have a optimum value, dending on a lot of factors. I pfer Pipemax (made from a organ tuning program)to do the smart work for me.
I am not a engine builder or a physiologist or whatever,by the way bad thing being to smart by half you need to make it so people get the idea who may not be as accomplished as you and your buddies.