intake mani and atomization

[d_money1]

i was just killin' some time this mornin' readin' some different posts and whatnot and got to thinkin' about an old Dsport article i read on that pro fwd drag racer Bisi Esiorah (sp?) and how he preferred carbs to FI. Now, i know he recently made the switch to FI in his new car, but his big reason was the ability of a carburetor to atomize fuel. Fuel Injection we all know is used because of it's ability to keep a/f ratios wherever you want them, and keep them very consistent. That's all well and good, less engine damage opportunity, a bit easier to tune if you're comfortable with electronics and/or computers. One thing that is really standing out was a little test that they had in the article about fuel injector location and distance from the port. He found that it would take about a 3 foot runner to atomize fuel with a fuel injector as well as a carburetor does naturally. So, after all this jabbering, my question is, with all these intake mani. tests goin' on and chit-chat about it, is anyone selling an aftermarket manifold with the injector bungs up in the runner? i'm not tryin' to say, lets put it three feet away from the intake port, but i was just curious if anyone has moved their injectors farther from the port or if there is any actual support of this?

 

[TunaTalon]

You did indeed dig up some olde motor head articles. Ah yes I remember it well.

First there were carburetors that used the venturi effect of the air stream to "suck" gasoline out of the bowl and into the intake manifold. Like the 1951 Hemi in my 1948 coupe. At such low pressure the air had to be turbulent to evenly distribute the fuel in the air stream. It was never perfect since there were so many variables affecting the need for fuel and only the non-linear venturi effect to control the fuel flow. Even with high rise manifolds and rough finishes some cylinders always got more/less fuel than others.

Then came single port fuel injection like on my 1981 Escort in the dark years of OPEC and gas shortages. Single port fuel injection used injectors in the place of the carburetor. The quantity of fuel could be better controlled but it had the same shortcomings as carburetors in distributing fuel to the cylinders.

Now the 4G63 uses multi-point fuel injection, with an injector for each cylinder. Atomization is improved by using higher fuel pressure across the injector and with each injector serving only one cylinder fuel delivery is consistent for all cylinders.

After living through the evolution of fuel delivery systems I have to say that my 4G63 is just the way I like it.

 

[91-gsx]

Very interesting information in this thread. Here is a bit more about the vaporization theory and acetone, read this it is very interesting Acetone In Fuel Said to Increase Mileage

This website sells these kits, now I am not saying this stuff works, but they do guarantee a 50% in gas mileage. I would imagine higher boost and timing with a more complete burn...
Hydro Assist Fuel Cell short description
More specifically watch these videos, a bit long but pretty interesting.
View video
View video

 

[d_money1]

i am definitely not sayin' strap on a carb or a DI/TBI setup. I agree with you in the fact our MPI setup is great, i personally love it as well, but, i was just curious if anyone's tried movin' the injector bung back a few inches, or better yet, can anyone think of anyway to actually test this?

 

[brute]

First there were carburetors that used the venturi effect of the air stream to “suck” gasoline out of the bowl and into the intake manifold.

Well that's not exactly what the Venturi Effect does, but it isn't really relevant to this discussion.

d_money, usually stuff that doesn't make sense has a way of working out. My prime example is when one is trying to tune runner length for an intake manifold. There is a certain length that will be perfect for personal goals, but it becomes absurd (like 1'4" - 16in). However, you can just divide this by 4 and get a more reasonable amount of 4" runner length. So instead of one trip through a 16" runner, the air will go through a 4" runner, hit the valve, bounce back 4 times, and enter with the velocity you've intended.

This is fairly off-subject, and you can read up on this in another thread or PM me, but the fact of the matter still exists: I trust Mitsubishi. What I mean by that is that I trust they did their homework and placed injectors accordingly. As TunaTalon said, the fuel pressure is much higher in FI than carburetors, so you shouldn't have anything to worry about.

On a side note, Shep runs 10 (weird, I know) injectors via intake manifold. Also, water injection is generally on the intercooler pipe, and it atomizes just fine. And finally, there are intake manifolds produced with nitrous bungs before the flange.

 

[gixrman]

If you look at most modern engines they are starting to use direct port injection with the injectors almost on top of the valves. My new GSXR1000 has 2 injectors per cylinder with the primaries in the ports and the secondaries over the top in a "shower" setup that come on under high engine loads. I remember that old Chevy engine builder Smokie somthing had a concept motor (4 banger)that actually heated up the fuel before it went into the carb, and under the carb the mixture passed through some sort of screen to help atomize the fuel even better. I believe it got some outragous MPG and made good HP, and that was back in the early 70's or 80's. I wish I could find it now.

I also read somewhere that reversing the injectors so they point upstream my help with atomization.

 

[TunaTalon]

Gasoline Direct injection (GDI) is the next step in the evolution of fuel delivery.
GDI uses high pressure to inject fuel directly into the cylinder near TDC of the compression stroke when it's time for ignition.

There can be no preignition because there is no fuel present until there should be ignition.

Very lean conditions with high compression ratios are possible for improved efficiency.

See Gasoline direct injection - Wikipedia, the free encyclopedia for a teaser on GDI.

(Also see Venturi effect - Wikipedia, the free encyclopedia for the venturi effect and it's use in automotive carburetors.)

 

[d_money1]

Direct Injection systems atomize fuel better because they use 1000-1500psi fuel pressure. At that pressure, the fuel will atomize perfect every single time, but we don't see over 100psi, there's a big difference. The idea behind moving the injector farther away was more chance or time to atomize the fuel. Mitsubishi and i do not have the same goals. I agree with you in the fact that the company produces great equiptment and definitely does do it's research. But, i'm talking about power and power production alone. Not mpg, durability, or any other factors that a company like them would be forced to put into their equation. This is all based on theory, and isn't something i have any need to do, my goals aren't that high at this point. On sheps setup, where are the secondary and i guess pair of 'third'ary injectors located? The last couple years i've been doin' the rotary thing, and have seen some awesome ITB setups where the injector is placed a few inches outside the venturis into the TBs. With the amount of turbulence, i am guessing they get great atomization. But they still run the stock primary injector location in the TB, it's the larger secondary injectors they put out in front of the venturys.

 

[dsm-onster]

Direct Injection systems atomize fuel better because they use 1000-1500psi fuel pressure. At that pressure, the fuel will atomize perfect every single time, but we don't see over 100psi, there's a big difference.

Just to add you have to subtract the psi of the COMPRESSED aircharge at TDC. It's alot of psi, BTW .

 

[bmoha2]

yeah it's weird and a little alarming to see fuel injectors actually outside the intake manifold spraying fuel directly into the itbs. I'd be afraid of setting the engine bay on fire.

 

[tkelly27]

Fuel atomization is based on temperature of the fuel, the amount of heat transfered to it, and the pressure it's under. Higher pressures don't cause better atomization. Atomization is basically the fuel boiling. Higher pressures require higher temperatures for any liquid to boil. Higher fuel pressures force the fuel out in a more distributed pattern and take the liquid from a high pressure condition to a low pressure condition. The spray pattern exposes more of the fuel to the surrounding air to help it mix. The injectors are aimed at the back of valves for two reasons, #1, the valves are hot, and the fuel will boil on them, #2, the valves are hot and the fuel will cool them down.

RWSabstract

"Pooling" can occur with the injectors further away. It's either the surface is rough enough, or not hot enough, one way or another the fuel can collect on the runners in liquid form. I don't believe that carburetors atomize better, there is fuel that pools up everywhere when you run them. A good aftermarket carb'd intke will have fins to act as a heat exchanger to boil the pooled up fuel under the carb. Many factory ones did this with exhaust heat while the car was starting up. Carburetors do induce low pressure for the fuel, but it literally comes out as a stream, not a nice fine spray.

I've heard of race cars spraying back up into the intake to help with atomization. It might be worth experimenting with.

 

[Mr Peepers]

Very interesting information in this thread. Here is a bit more about the vaporization theory and acetone, read this it is very interesting Acetone In Fuel Said to Increase Mileage

This website sells these kits, now I am not saying this stuff works, but they do guarantee a 50% in gas mileage. I would imagine higher boost and timing with a more complete burn...
Hydro Assist Fuel Cell short description
More specifically watch these videos, a bit long but pretty interesting.
View video
View video

Oh...my...god... I just finished watching the first video. The best part was them saying "you don't have to change your oil anymore." I'll grab some pizza and watch the second The cool 90's special effects makes me want to buy their product.

So many tests that had nothing to do with the product... I don't know what to say WTF

 

[TunaTalon]

Just to add you have to subtract the psi of the COMPRESSED aircharge at TDC. It's alot of psi, BTW .

A 4G63 with 8.5:1 compression ratio and 3 bar of boost has a charge pressure of about 860 PSI near TDC before ignition. And that's with a moderately efficient intercooler.

GDI needs the 1000 PSIG just to keep the hot compressed air from backing up into the fuel line.

 

[Mr Peepers]

Another really good resource for GDI(and the rest of the technical school is a gold mine of info too)

AutoZine Technical School - Engine

 

[d_money1]

the explanation of fuel going from a high pressure situation to a low pressure situation and how it effects "boiling" of the fuel is a great example of exactly why DI atomizes fuel better. It works exactly like your cooling system, when you open it, the water boils all over the place when it's hot. As far as fuel spraying on the back of the valves, in a direct injection engine, there is no fuel hitting those valves. Do they use a different material for the valves in those cases? The combustion pressure i think is gonna have less effect in this situation that we're talking about, or i don't think it actually relates to each intake setup. The pressure is gonna be the same assuming the same engine with each setup. But, great discussion, great info. I'm still not sure how i feel about it. I think a big part of the atomization difference is based on high rpm "race" situations. I don't think any carb is gonna pool at 6000rpm, i think that's enough velocity and turbolence that dumpin' fuel is gonna make more power.

 

[dsm-onster]

A 4G63 with 8.5:1 compression ratio and 3 bar of boost has a charge pressure of about 860 PSI near TDC before ignition. And that’s with a moderately efficient intercooler.

GDI needs the 1000 PSIG just to keep the hot compressed air from backing up into the fuel line.

That' great info. Considering almost all GDI sytem employ MUCH higer CR, then it seams that 1000psig is definately needed to overcome the compression stroke pressure. The net pressure is not super high by todays standards.

 

[Defiant]

Those of us who spent twenty years dicking with carburetors couldn't be happier to see fuel injection and feedback engine management come of age. And then, of course, there were SUs and Strombergs. Just effing shoot me.

Now, when we get rid of camshafts and start using FI-type intelligence to actuate valves, we'll be in a modern age.

 

[dsm-onster]

Or we could at least employ a beyond-19th-century valve design: Coates Spherical Valve System.

 

[d_money1]

BMW produced an engine that used solenoids to control valves with motors ( i would think something like a stepper motor in IAC valve ) and so they literally could have ANY cam profile they wanted at any given time they wanted. Expensive motor, but an awesome idea. I personally think BMW is gonna rule the auto industry. Between hydrogen powered super cars and just the r & d they put in, the different ideas they're willing to try...they've got the right ideas.

 

[Defiant]

Willys-Knight sleeve valves for the win.
and Willys Overland Knight Registry - Willys Knight Engine
Still, we have to get rid of cams. BMW's electronics are the right idea, but the better path would be engine oil against the stem of the valve, controlled the way fuel injection is: variable duration, lift, timing and everything. You'd also probably have less parasitic loss in an oil pump for it than you do driving cams (although that may be a wash).

Then there's Butterworth valves, which are apparently so obscure not even Google knows about them: instead of a valve stem, the valve head (fairly normal, kind of like a valve with its stem cut off) is mounted on a sort of hinge arrangement that lets the valve swing open. They have both wear and cooling problems, as they don't rotate on their seats as normal valves do, and don't have the stem to carry the heat away from the head to the (non-existent) valve guide.

 

[d_money1]

i don't think using a hydraulic setup like that would work very well. it would be harder to control how much "lift" you ended up with, and i don't think you'd have as much control over different "cam profiles" and i don't know if it would work fast enough either. I really think BMW had the right idea with the stepper motor/solenoid setup. As for swinging open valves, i can see exactly how it would have wear and cooling problems, plus i think the back of the valve itself really helps with the whole atomization effect, i think it's just one more thing to help keep the fuel in suspension.

 

[Defiant]

i don't think using a hydraulic setup like that would work very well. it would be harder to control how much "lift" you ended up with, and i don't think you'd have as much control over different "cam profiles" and i don't know if it would work fast enough either.

Funny, it seems to keep up with fuel supply just fine. It'll only take development.

 

[d_money1]

yeah, i'm sure it'll happen, even if it doesn't end up being the standard, i'm sure someone can get it to work. I just think that you would have a lot more precision and control with the solenoid setup. I'm sure that soon someone will come up with an idea that doesn't involve either of those ideas and works with more precision, efficiency and control than both of them. Can only try to imagine where it might go...