Landracing Forum
Tech Information => EFI Questions => Topic started by: Dr Goggles on July 06, 2007, 06:36:25 PM
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Hi all .
I've been toying with the idea of making an injector stack style manifold for our V6 for a while now.....oh , oh .I know that getting the injectors themselves close to the valves will help, that there will be "some" tuning involved in getting the length of the stacks right but what I want to know is .....does anyone know of a good way of working out what size butterflies will get me into the "ballpark".......I'm currently battling a too large throttle body on my road car that runs LPG...goes great on limited openings but that's it , but that's a side line and not important right now .Are there some "sums" I can do that will say "six of these will flow X and get you near where you want to be".......
Why ???..........just because :wink:
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You can try this at home :
Depending on the angle of the dangle, you can do a lot to slow the opening and with it the airflow at mid throttle or anyplace else with the geometry of the flap in relation to the actuator.
So to with a racer, if you wish to maintain slow speed driveability and flow the max at WOT, the plates might not want to open directly as the as the pedal is pinned to the floor.
You can make a model to prove the concept with your degree wheel as the central point and an indicator pinned at the middle to record the result in degrees.
Now off to the side, establish various hinge points in a vertical line next to it.
Those will represent the various test hinge points of the actuator.
Now make an actuator arm to hinge on those points that has multiple points for the link to the Flutterbye shaft.
At WOT the Flutterbyes need to consider the flow rate (mostly the size) of the port + whatever losses occur around the hinge shaft and possible nozzle projection that might disturb the flow.
There is a formula floating around that speaks to stack diameter and length that is every bit as important as exhaust science. :wink:
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Dahlgren will probably pipe in soon. In the meantime there is a website that you can find more information than you care to read. www.speedtalk.com Quite a few engine guys post on the site including Darrin Morgan from Rehr Morrison and other top engine builders/designers. Use the search function to narrow down the multitude of posts.
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................I know that getting the injectors themselves close to the valves will help, ................
...............does anyone know of a good way of working out what size butterflies will get me into the "ballpark".......I'm currently battling a too large throttle body on my road car that runs LPG................
Why ???..........just because :wink:
Some of the F1 engines and others are moving the injectors away from the valves and further up the intake tracks, so I wouldn't be afraid of that. I think a recent Hot Rod magazine explained why they were doing that and if you are interested I'll try and find it.
Usually the cfm of the throttle body for an EFI engine is not as critical as getting the size of a carb right and can be a lot larger than a carb as it is not handling the fuel. What is the engine size on the road car??? and what size body are you using?? and how is the LPG injected??
c ya,
Sum
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OK to either clear this up or muddy it worse.. you can pick.. The flow response from a butterfly type system is 1-cosine of the opening last I looked but taking it from memory. What you need to remember is it is an s shaped curve with a large change initially fairly linear in the center and slow at the end per degree of change. So your linkage and tps sensor needs to have a similar response in order to maintain some drive-ability and tune-ability as well. A good modern ECU can do this or you can do it with a linkage to the TPS if the ECU is a bit more modest and won't let you define the sensor response curve.. As far as butterfly size typically the same area as the valve area will work OK 99% of the time. Size matter size always matters if you want to make some torque and if you have no torque you have no hp period underline exclamation point. The typical engine drops 15% torque between max torque and max hp over what is usually around 1500 to 2000 rpm.. so torque is your pal. Too large a runner and butterfly equals lost torque, not your pal at any time..
Injector placement is a matter of desired driving style. Smooth off idle good mileage and emissions is close to the valve big power is see if you can shoot it across the room and still get it in the top of the stack.. real life a compromise but further up the stack will make power as long as it stays there and does not have tons of reversion because you either made the stacks too short too large in diameter or the cam timing is very off the wall..
See clear as mud read it twice and the light will blink on..
Dave
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SEE LONG FORM ABOVE ^ :wink:
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The further you get the injectors from the Valves, the better the Air/Fuel mix you will have.
As for your Question of Diameter and length figuring,
Here is a spreadsheet I made after reading a few books on the subject, and planning mine out: http://www.riley-music.com/BowsStuff/TunedIntakeandExhaustdesigns.xls
Some of the information is for my setup, like Velocity Stack length... but the basic idea is that you are tuning for the air pulses.
EDIT:
Link Fixed
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Linky no worky.
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http://riley-music.com/BowsStuff/Tuned%20Intake%20and%20Exhaust%20designs.xls
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Linky no worky.
You gotta love Microsoft and the ability to easily put spaces in a file name.
(signed, a Unix weeny)
;-)
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http://riley-music.com/BowsStuff/Tuned%20Intake%20and%20Exhaust%20designs.xls
Thanks. Above about 13,850 rpm we need a negative length intake port and stack, according to your sheet. I can't figure out how to fabricate such.
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http://www.riley-music.com/BowsStuff/TunedIntakeandExhaustdesigns.xls
Thanks. Above about 13,850 rpm we need a negative length intake port and stack, according to your sheet. I can't figure out how to fabricate such.
No, I did say that the Velocity stack section may not apply to your application, didn't I?
Also, you need to know the distance front the face of the Head to the center of the valve stem....
mine is 3.25"
If yours is 3.25", then your total intake length front the lip of the Velocity Stack to the head side of the flange should be around, depending on what pulse you tune for:
Second Pulse Length: 4.58 In. 116.2 mm
Third Pulse Length: 3.78 In. 96.0 mm
Forth Pulse Length: 2.11 In. 53.7 mm
Fifth Pulse Length: 0.66 In. 16.8 mm
Look at the Motorcycle setups that run at 13800 rpm, the entire intake is about 4" long
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I did say that the Velocity stack section may not apply to your application, didn't I?
Sorry, missed that! Your TB is 7.8" long, I take it.
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From the Head side of the intake flange to the intake side of the Throttle body, without out the Velocity Stack, mine is 7.75"... yup
This is not exact, but it does get you in the ballpark, according to my Engine Analyzer Pro Software.
It should give you a good, close starting point. If you take the Total length needed, then subtract the length of the Intake Valve port (in the head), Intake Manifold runner, and Throttle body, you will get the required length of your velocity stack.
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runner length does not work like a musical instrument..
way more going on than that.
think in terms of injector placement air velocity and inertia..
Dave
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Doc Goggles,
Ever think of making your injectors "slide valve" style? I worked with a slide valve injector for a Mazada rotary back in the 80s and the slide valve set up always made better hps than a butterfly set up, and if your port spacing is equal with some room in between the ports it is not a hard part to make. Miss all the "cosine pie are square three bag full" B.S. on the throttle opening too. Do not work well with blowers or turbos though.
Rex
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very interesting Rex and I guess in the application we're using it that the excess wear that slides suffer ( in comparison to 'flies)isn't really too much of a concern,....right now I'm side stepping the "stack" idea and am concentrating on a twin throttle body manifold . I just sawed the top off the stock manifold and put a kind of pent-roof top on it to add a bit of plenum volume and top it off with two of the standard TB's chimney style on top .We had a single unit on the motor in a similar config' and purely on the reasoning that there was room for two I'm doing it .
Now , another question for the gallery. This motor is a 3.8litre and the stock throttle body is 60mm, I'm thinking I'll set the throttles up so that the second one goes from 0-100% after the first one reaches about 40% , too early ?, too late ?....... any comments
In another realm , my road car is making a fool of me ........the old straight six got a set of lifters and a head the other day , now it won't even start , it'll backfire occasionally and the local dogs are hoarse from barking ,but run ? not on your Nellie!............Sick of staring at it , and having nearly scratched my scalp off it's all coming apart again , I know it'll be something silly , really silly and you know what?.....you're not gonna hear about it!!!! :-D :-D
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No sweat "Old Timer" We will look 180 deg away while you figure it out. :wink:
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No sweat "Old Timer" We will look 180 deg away while you figure it out. :wink:
give me a bit of credit....my stuff ups are more complicated than that.....let's just say in more modern terms ...." i needed closure".......lashings and lashings......it was to do with a miss match( that's right she wasn't married) of some rockers and the "push" ........now , I don't know how many of those hollow rods I've thrown out over the years ....and now I just need one :? :? :? :?yeah you can all laugh.
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So it seems that your motor didn't measure up to the trust you placed in it.
Doncha hate that ?
Kick it again for me too. :wink:
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very interesting Rex and I guess in the application we're using it that the excess wear that slides suffer ( in comparison to 'flies)isn't really too much of a concern,....right now I'm side stepping the "stack" idea and am concentrating on a twin throttle body manifold . I just sawed the top off the stock manifold and put a kind of pent-roof top on it to add a bit of plenum volume and top it off with two of the standard TB's chimney style on top .We had a single unit on the motor in a similar config' and purely on the reasoning that there was room for two I'm doing it .
Now , another question for the gallery. This motor is a 3.8litre and the stock throttle body is 60mm, I'm thinking I'll set the throttles up so that the second one goes from 0-100% after the first one reaches about 40% , too early ?, too late ?....... any comments
Dr Goggles--Your Twin throttle bodies sound like a good idea to me. The progressive linkage has got my curiosity active. If you are using a throttle position sensor to send information to an ECU for injector control are you going to be able to able to compensate in your fuel tables to keep the fuel/air ratios proper? oops! I just got it. Of course you are! Are you going to run two throttle body injectors or is it set up for individual injectors in the runners?
I'm going to try and run my Saturn on the injectors that it came with (close to the intake valve) AND the injectors that came with the Hayabusa throttle bodies. :-o. It's good to hear someone else is dreaming up things to try. There is no doubt some one else has tried both of these ideas. I hope they worked. Please carry on! :-D :-D
harv
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Quote from: JackD
No sweat "Old Timer" We will look 180 deg away while you figure it out.
Quote from:Dr Googles give me a bit of credit....my stuff ups are more complicated than that.....let's just say in more modern terms ...." i needed closure".......lashings and lashings......it was to do with a miss match( that's right she wasn't married) of some rockers and the "push" ........now , I don't know how many of those hollow rods I've thrown out over the years ....and now I just need one :?yeah you can all laugh.
I'm just wandering if I am sworn to secrecy
G
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I'm just wandering if I am sworn to secrecy
G
meanwhile I'm wondering if you're wandering or wondering about wandering or just wondering :?
....no , not yet , no-one has them in stock .......... :roll: :?, yeah I'm wondering too.
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Maybe you could try the tip (translation tip = rubbish dump)
Or take one out of the EH (translation EH = 1964 holden van)
G
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Maybe you could try the tip (translation tip = rubbish dump)
got some...from mad Bill ,..now it sounds just like it did .........before I pulled it down ....I fear it may have suffered a "Lobe-otomy"......why ,as you asked Sunday, DID I BOTHER :oops: :x
So it seems that your motor didn't measure up to the trust you placed in it.
Doncha hate that ?
Kick it again for me too. :wink:
kicking it and using words you won't find in the dictionary.
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we're not hijacking this thread like that one on DLRA are we
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we're not hijacking this thread like that one on DLRA are we
"HIJACKING"
I kinda like the sound of that. :wink:
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Uh oh
Now I'm on a watch list somewhere
G
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Re: injector placement
An injector up in the runner will have less effect on airflow at the short turn radius (than one at the manifold-head interface) since the charge has some time to "re-laminate" a bit; IIRC you need 10 × the throttle disc diameter to accomplish as much of this as will happen.
It will also vaporize more, but is that what you want? An engine with very efficient intake ports can suffer a bit of VE loss, but remember that the 12.5:1 (or whatever) air:fuel is by weight. By volume completely vaporized gas is hundreds of times larger volume than liquid and displaces air in the charge. The balance of combustion efficiency (low and consistent maximum droplet size, homogeneous mix, etc.) vs. VE (maximum charge mass) is very complex, and definitely not always in favor of complete vaporization unless maximum fuel efficiency is a high priority. Read Vizard on this.
Re: IR vs. staged or single throttle bodies.
Individual throttles can be slightly larger than the largest known-effective runner ID for a carbureted manifold since you don't need the .5-1" Hg vacuum for nozzle response. My guess would be that it's almost always between the port size and valve size + 20%. A single throttle need not total the area of the IRs since there will always be plenum volume available.
IR will always have, IMHO, better manners with high overlap than a plenum, and stronger wave tuning since superposition waves are minimized. You can still use Helmholtz by adding an air box over the stacks.