I'll start this new post with some quick comments. Ideally you want the same air/fuel ratio in each cylinder for each combustion event. Most people think about fuel distribution, but I've found with EFI the air distribution plays a much bigger part in most cases, especially wiht port fuel injection. Most injectors flow around +/-6% of each other, so from a fueling standpoint, you start there.

The design of the intake, and surprising the throttle body, have a lot to do with how much air each cylinder recieves. More surprisingly is this is very prevelent at low airflows, even at idle.

We have 8 widebands on our dyno, have had them for quite a few years now, and the results are always surprising.

I'll post more later.

The other thing too is this is all VERY dynamic based on load and RPM. Meaning you can't just put in an 8% correction into one lean cylinder and have it "fix" it all the time. That will probably only "fix" it at one very small RPM and load point.

thanks for the confirmation Doug. I've suspected this for a while, especially when I have to go richer at idle to make it happy, to cover up a lean cylinder or two. Interesting point about the conditions changing by rpm and/or load also, makes total sense.

Jody

What role does a dual plane vs single plane play in air distribution on a MPFI setup and why do you see mostly single planes?

Or is better air distribution with a single plane the whole point of the matter?

Thx

What role does a dual plane vs single plane play in air distribution on a MPFI setup and why do you see mostly single planes?

Or is better air distribution with a single plane the whole point of the matter?

Thx

Good question. I know Doug runs a tunnel ram. Does the large plenum of the Stealth Ram even out the air better than a single plane?

Mark

Good point about air distribution... firing order can make a big difference in air distribution too. This is where IR systems with equal length runners come into play. So long as the runners are long enough to seperate cylinder events and the connecting plenum volume is adequate. It does not take much to introduce variance, just a plenum that ends too close to the runner is enough to drop flow in that runner.

I have gotten the impression that some of the OEMs with sequential injection are timing the read of the O2 sensors to synchronize with cylinder firing events. They then use this as a feedback to tweak individual cylinders. All you need is a fast enough sensor response and enough CPU power. And CPU power is really NOT an issue anymore.

A dual plane intake is completely optimized/compromised to the nature of the carburetor. It is about dividing up the intake pulses evenly between two sides of a carburetor so fuel metering sees a relatively clean signal. In the process of doing this the intake runners become different lengths and sometimes bend in flow restricting ways. The different lengths optimize at different RPMs and thus imbalance flow.

A single plane intake is about the most direct path from carb to port. There are still some differences between runner lengths but not quite to the extent as in a dual plane. Thus flows tend to be higher on the mid and top ends. And since with EFI we are not dependent on even draw for fuel metering signal, we do not have the typical downside of a single plane used with a carburetor.

The real reason may well be the fact that single plane intakes just look cooler :thumbsup: Do not underestimate the power of marketing or customer perception.

This issue is where advanced engine management can really be a benefit. I know that Big Stuff 3 has individual cylinder control and I believe AEM may as well. Do any of you happen to know if megasquirt has this function?

This issue is where advanced engine management can really be a benefit. I know that Big Stuff 3 has individual cylinder control and I believe AEM may as well. Do any of you happen to know if megasquirt has this function?
Simple answer is no.

More involved answer is MS generally does not do sequential injector control. That is something in the development pipeline. Being an open system though some folks have hacked stuff together for smaller engines to do sequential as well as COP. And of course once you have done that you can get into the code and start doing whatever you want.

That is you are a programmer type :D

This issue is where advanced engine management can really be a benefit. I know that Big Stuff 3 has individual cylinder control and I believe AEM may as well. Do any of you happen to know if megasquirt has this function?

BS3 has individual fuel and timing controls, but it's just a set % everywhere, not by rpm range and/or load. As Doug mentioned, while you may need one thing at idle it'd almost never be the same requirement at all rpms and loads, so it's pretty basic at best. Most guys just use it to tune the wot areas; damage to be done will likely occur there.

Jody

EFI still lives by the rules of air velocity in the intake tract. Dual planes usually have longer runners with smaller CSA's that promote lower RPM cylinder fill. Most single planes have shorter runners and largers CSA's and are intended for higher RPM.

The EFI is advantageous over a carb as you don't have to worry about signal like you do wiht a carb. But you still need the correct CSA and runner length for your engine with EFI or a carb.

BS3 has individual fuel and timing controls, but it's just a set % everywhere, not by rpm range and/or load. As Doug mentioned, while you may need one thing at idle it'd almost never be the same requirement at all rpms and loads, so it's pretty basic at best. Most guys just use it to tune the wot areas; damage to be done will likely occur there.

Jody

Yes, from low to high load and low to high RPM, air distribution is all over the place on some engines.

The best plan bar none is a properly designed intake.

That is what is so nice about IR intakes. If the idle air is balanced, you have the best chance possible for very uniform air distribution.

Throttle body design and throttle angle have a huge affect on air distribution at low air flows on a typical 4bbl style MPFI manifold. IR's don't have this problem.

I know Doug runs a tunnel ram. Does the large plenum of the Stealth Ram even out the air better than a single plane?

Mark

I'm sorry if I missed this answer. Someone might have explained it, but I didn't catch it.

Maybe I'm just too dumb for fuel injection at this point in time. Heck, I don't even know what CSA's are, and I assume IR means Individual Runner.

Maybe "71 Chevy" is right; just go do tons of research on the Mega Squirt website to learn about this stuff. Maybe they have a beginners section.

I know what I want to do, but I just want the best way to get there without making too many MORE expensive mistakes. That's what scares me about Mega Squirt, so I guess I'll have to spend a bunch of my time learning how to assemble piecemeal EFI from them.

I should have just bought a fully assembled carbureted 502 crate motor and been done with it! Sorry for the rant, but I thought that this stuff would be easier than it is.

Mark

I'm sorry if I missed this answer. Someone might have explained it, but I didn't catch it.

Maybe I'm just too dumb for fuel injection at this point in time. Heck, I don't even know what CSA's are, and I assume IR means Individual Runner.

Maybe "71 Chevy" is right; just go do tons of research on the Mega Squirt website to learn about this stuff. Maybe they have a beginners section.

I know what I want to do, but I just want the best way to get there without making too many MORE expensive mistakes. That's what scares me about Mega Squirt, so I guess I'll have to spend a bunch of my time learning how to assemble piecemeal EFI from them.

I should have just bought a fully assembled carbureted 502 crate motor and been done with it! Sorry for the rant, but I thought that this stuff would be easier than it is.

Mark

Once you understand EFI it actually is "easy". The problem is people are looking at 500 things and only need to concentrate on 5.

The Holley Commander 950 manual, as far as how to tune EFI (you can download it) is pretty good at a step by step tuning.

All my talk about CSA and IR, blah blah blah isn't any more complicated than it relates to carbs.

Heck, if a REAL carb guru got on here and talked about emulsification and droplet size and how to alter those two items though carb design, nobody would run a carb, but 99.9% of people don't worry about that because they just bolt it on. Similar to that, get an EFI system that has a lot of this work already done by the company that designed it. The new EFI system I'm doing has a self tuning fuel map. The fuel map is 80-90% the most important part of EFI. I'm taking that out of the hands of the end user if they want. The rest of the tuning has been performed on many dyno enignes and vehicles so most of it shoud be very close for many. The last 3 sentences I just wrote are key to a new person having success with EFI.

People use PC's. Do most know now they work inside? Of course not, but the PC industry has made it SOMEWHAT simple to use the basics. This is what needs to be done and is being done with EFI.

Good question. I know Doug runs a tunnel ram. Does the large plenum of the Stealth Ram even out the air better than a single plane?

Mark

I think it more relates to the entry angles of how the runners intersect with the plenum but the size contributes as well too.

If you look at the entries to a LSx intake, it is really an upside down tunnel ram. The did what they did to get packaging and the runner lengths they wanted.

I'm sorry if I missed this answer. Someone might have explained it, but I didn't catch it.

Maybe I'm just too dumb for fuel injection at this point in time. Heck, I don't even know what CSA's are, and I assume IR means Individual Runner.

Maybe "71 Chevy" is right; just go do tons of research on the Mega Squirt website to learn about this stuff. Maybe they have a beginners section.

I know what I want to do, but I just want the best way to get there without making too many MORE expensive mistakes. That's what scares me about Mega Squirt, so I guess I'll have to spend a bunch of my time learning how to assemble piecemeal EFI from them.

I should have just bought a fully assembled carbureted 502 crate motor and been done with it! Sorry for the rant, but I thought that this stuff would be easier than it is.

Mark
For a complete bolt-in and go you would want to look at the GM Ramjet crate :yes:

I am going to say something similar to what Doug said... as in many things it depends on how deeply you want to get into it. There is still a law of diminishing returns in the land of EFI. You could run just about any of the EFI systems on the market and have a pretty good ride. It might not be the ultimate ride but it would be pretty good. We do not all build and drive cars like Jody's :cool:

This topic of air distribution is a good example of a more advanced topic. You could drive two cars, one with good distribution and one without and you would probably not be able to tell the difference. It really only comes into play when you are tuning to 10/10s rather than 8 or 9/10s. Very much like tuning of air bleeds in a carburetor that very few folks do.

And FWIW CSA == Cross Sectional Area or a fancy way to say how big the ports are.

I have wandered around the MS forums. And spent a lot more time here on TC. Between the two I would tend to ask questions here first ;) You will find a lot more, shall we say, alternative applications over there besides our american V8s. Besides now we have a forum just for these kinds of questions. So ask away. :beers:

For a complete bolt-in and go you would want to look at the GM Ramjet crate :yes:

I am going to say something similar to what Doug said... as in many things it depends on how deeply you want to get into it. There is still a law of diminishing returns in the land of EFI. You could run just about any of the EFI systems on the market and have a pretty good ride. It might not be the ultimate ride but it would be pretty good. We do not all build and drive cars like Jody's :cool:

This topic of air distribution is a good example of a more advanced topic. You could drive two cars, one with good distribution and one without and you would probably not be able to tell the difference. It really only comes into play when you are tuning to 10/10s rather than 8 or 9/10s. Very much like tuning of air bleeds in a carburetor that very few folks do.

And FWIW CSA == Cross Sectional Area or a fancy way to say how big the ports are.

I have wandered around the MS forums. And spent a lot more time here on TC. Between the two I would tend to ask questions here first ;) You will find a lot more, shall we say, alternative applications over there besides our american V8s. Besides now we have a forum just for these kinds of questions. So ask away. :beers:

VERY, VERY well said... :)

I deal with a lot every day of things that show "not ideal" or heck even "poor" data, but without seeing that data, or understanding it, you usually can not tell "seat of the pants" that something is not as good as it should be. Trust me, engines are VERY forgiving.

On the other hand, drive a new C6 vette. It doesn't do what it does by accident. Millions of dollars of development effort.

On any EFI engine I've owned, I usually have no more than 1 hour tuning time on it. My datalogs aren't "perfect" looking, but they drive fine.

Any this year with the new EFI bracket racing, my car was unreal consistent. I had one night two runs in a row were identical to the .000, with the incrementals almost the same and the runs around that one were within .005 or so. That was within my "1 hour" tuning on this engine. My car was able to run pretty much within .005-.01 of what I thought it would run every run all year long!

.....
Heck, I don't even know what CSA's are, and I assume IR means Individual Runner.

....
Mark

CSA=cross sectional area

Andrew

Doug,
What do you think of those throttle bodys that just have one large barrel rather than the typical 2 or four barrels?


http://static.racingjunk.com/63/ui/8/94/4585582357757-BBC-EFI-Throttle-Body.jpg

One of my previous cars a few years ago was an '87 Buick Grand National. These cars are a prime example of air distribution problems. You have a turbo generating up to 15-18psi feeding the throttle body. The trottle body is sitting at the front of this doghouse shaped plenum on top of the intake manifold. In theory, all the intake runners should see the same air pressure inside the plenum. But the reality is the air velocity shoves air into the rear intake runners, sort of a ram air effect. The result is the rear cylinders tend to run a bit lean. Lean mixtures can cause preingition knock, which is bad news.

Just as I got out of the turbo Buicks, there was some guys that came out with a plate that mounted between the doghouse plenum and the intake manifold. This plate had holes, or triangular shaped slots that opened to the individual intake runners. Supposedly this simple device evened out the air distribution to all cylinders.

Doug,
What do you think of those throttle bodys that just have one large barrel rather than the typical 2 or four barrels?


http://static.racingjunk.com/63/ui/8/94/4585582357757-BBC-EFI-Throttle-Body.jpg

I'm not Doug ;) but I'd think those could have part throttle tuning issues due to the amount of air increase versus small throttle movements.

Jody

I'm not Doug ;) but I'd think those could have part throttle tuning issues due to the amount of air increase versus small throttle movements.

Jody

Sum of a &$##. Not that thing on a street car. OEM monoblades usually have both a "cam" lever that slows initial opening AND a "contoured bore" or a part riveted on the back of the plate to not have 1000 CFM of air enter at 10% opening!

When designed right, or have a moderate bore size, they are ok, but like Jody said you might as well put an on-off switch on that thing.

There's a lot of force/pressure on something like that one too which is not good. If you don't have the shaft offset right, you can have sticking throttles, etc.

One thing about a large TB is the reduced air flow velocity through the TB at full throttle. The decreased velocity helps the air flow turn into the runners with reduced turbulence, which helps total airflow into the individual cylinders. In effect, it should reduce runner to runner A/F variablility.

I agree, the one shown would be a pain in the A** to tune at part throttle, but I've talked to other people with monoblades and they haven't noticed any major issues. Who knows?

I'm hoping that my Holley 2000 cfm TB won't be a pain, but I'm far too involved with trying to get the body of my Camaro in shape to worry about getting my engined tuned.

John

One thing about a large TB is the reduced air flow velocity through the TB at full throttle. The decreased velocity helps the air flow turn into the runners with reduced turbulence, which helps total airflow into the individual cylinders. In effect, it should reduce runner to runner A/F variablility.

I agree, the one shown would be a pain in the A** to tune at part throttle, but I've talked to other people with monoblades and they haven't noticed any major issues. Who knows?

I'm hoping that my Holley 2000 cfm TB won't be a pain, but I'm far too involved with trying to get the body of my Camaro in shape to worry about getting my engined tuned.

John


A progressive 2000 4bbl Holley will have a much more linear airflow than that monoblade shown with its linkage.

ooohhh, the fabulous flying toilet.

mostly good for cars that have only 2 throttle positions, closed and WOT.