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]

Re: Intake design for EFI

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]

Re: Intake design for EFI

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]

Re: Intake design for EFI

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]

Re: Intake design for EFI

...mixture distribution.

[seanm]

Re: Intake design for EFI

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]

Re: Intake design for EFI


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]

Re: Intake design for EFI

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]

Re: Intake design for EFI

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

[JeffMcKC]

Re: Intake design for EFI

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.

[seanm]

Re: Intake design for EFI

The resonant frequency effect makes sense for the most part, there also needs to be a taper to the runners. This is something that has never been explained. I assume this increases the velocity some, but why, and how much is the correct taper and how is this value determined?

Then are any of these values of any use in a blown application?

[CTX-SLPR]

Re: Intake design for EFI

I don't pretend to know the math behind the taper though the pipe diameter is governed by boundary layer effects causing an effective decrease in the diameter of the pipe. My assumption is its a venturi effect type mechanism to increase air speed through the runner while decreasing the pressure differential at the mouth of the runner but again this is all guess and assumption on my part.
On a blown application I have known people who have practically tried it both ways and swear it made a difference but without some sort of back to back testing with bolt in intake tubes I don't think it makes a difference on turbo motors at least. I would think the air flow is so chaotic in the plenum that it would virtually cancel out all the runner pressure waves from the blower pulses in anything but a CSc or Rotax system where the boost would have a smoother character to it. I'd love to be able to test this out but short of them trying it at AFRL on the small engine test stands its probably never going to happen.

Jeff, I could understand the first half of what you said as it relates to the technical part but once you got into the personal part of it you lost me. Everything is built off of some sort of scientific process but as they say in advertising "Individual Results May Vary", the practical implementation takes a bit more fine tuning to a specific engine. I bet if you ask Tom Hoover, you know the father of the Hemi and designer of the first tunnel ram, about what is going on and he's going to agree me on the phenomenon behind how a tunnel ram works. Don't go dismissing me because I understand what your black box "Pipemax" is doing inside though it's going a bit deeper than I have ever done by hand.

The wikipedia quote on Intake Resonance tuning:
Pressurization - A tuned intake path can have a light pressurizing effect similar to a low-pressure supercharger due to Helmholtz resonance. However, this effect occurs only over a narrow engine speed range which is directly influenced by intake length. A variable intake can create two or more pressurized "hot spots." When the intake air speed is higher, the dynamic pressure pushing the air (and/or mixture) inside the engine is increased. The dynamic pressure is proportional to the square of the inlet air speed, so by making the passage narrower or longer the speed/dynamic pressure is increased.

[91xcabpro]

Re: Intake design for EFI

Let me see if I can take a pass at this resonance thing in a way that everyone can understand and agree upon.

1.  When the intake valve closes a pressure wave travels up the runner.
2.  We want to get the runner length to be a multiple of the wavelength of this wave.
3.  Wavelength is the velocity of this wave divided by the frequency (or RPM).
4. When one of these pressure waves reaches the plenum, it can be used by another runner to speed up its flow.

That seems to be the basics of it, minus a lot of fudge factors, namely because the velocity of the wave is going to have a lot of variables, and minus the theory behind how many multiples of the wavelengths you want to use for the runners.

Oh yeah, and not knowing what a part on a car is called, has never kept me from understanding how it works.  ;);D

[JeffMcKC]

Re: Intake design for EFI

You get the idea just like the washing machine water shutting off, the noise you hear in the pipe is a "water hammer" or wave effect. It takes a total package to make full use or just be dumb and lucky

By the way, its not ment to be personal, just a word picture makes it a lot easier for some to understand it faster. A "Rose by any other name" this will be a good link to follow on your "Everything is built off of some sort of scientific process " I do warn this board takes no prisoners

http://www.yellowbullet.com/forum/showthread.php?t=105138

This would be Chris's web page http://www.ure-racing.com/

He builds motor's that make lots of Onions!!!!

[CDMBill]

Re: Intake design for EFI

This is why building headers/exhaust and intake manifolds/heads are interrelated topics.

But coming back to the original question as budget conscious builders we are typically constrained by available production manifolds which are overwhelmingly biased towards the fat part of the aftermarket which is still carburated.

I think that's why we see more carb flanged manifolds for LS and Ford Mod mototrs than their native EFI applications.

I have Hogan's sheet metal intake catalog that has a lerge number of crossram, tunnel ram and other EFI specific manifolds pictured in it which shows the design elements mentioned here by Jeff and others which supports the Helmhotlz reasonace tuning concept. The SOTA engines form BMW and others have variable cam timing and and manifold volume to create a much larger usable power band for theri production engines.

I can't wait for the day when we'll be able to use direct injection on our after market stuff with variable cam timing, talk about power!