After fitting my K&N Lunchbox, I thought to myself... I wonder how this affects the bikes intake runner length.
Can't say it shortens it that much more than the distance to the airbox, so it wouldn't affect the tune too much in the regard.
Short Intake Runners = Higher top end Horse Power (And you can't get any shorter than a Lunch box whacked on the carbs)
Longer Intake runners = More low down torque
so I was thinking, has anyone tried playing with the runner length on a GS? It would be interesting to see if a longer runner length made any low down performance gains. 8)
This sight could be helpfull:
http://www.rbracing-rsr.com/runnertorquecalc.html
Does anyone know the RPM's at which the GS produces its peak torque?
In my understanding, the intake runner is the portion after the carbs, but I know what you're talking about. You loose those rubber pieces that smooth the airflow into the carb, which would reduce power at all RPMs. In reality, you get enough extra flow through the filter that it dosen't matter, but I bet if you could open up the hole in the stock airbox to allow it to take a filter with a larger opening, you could probally get more power than the clamp on k%N without those pieces.
:cheers:
I was thinking if a new bellmouthed runner was added onto the carbs you could get better airflow than a K&N.
If it was the right length runner, + bellmouth/trumpet end you could end up with a much bigger HP increase (after proper jetting of course) than just a lunch box/pods alone.
Hmmm. O0
Intake runner lenght generally relates to the runner after the throttle plate. When at WOT, longer runners before the throttle plate can help port velocity too, though. Think velocity stacks...
Considering that the stock air box has no true "runners" in it, you have likely not changed the port velocity for your motor. It would be hard to predict the change anyways because of the strange set up of the stock air box.
-Turd.
Quote from: galahs on October 11, 2006, 09:38:43 AM
I was thinking if a new bellmouthed runner was added onto the carbs you could get better airflow than a K&N.
If it was the right length runner, + bellmouth/trumpet end you could end up with a much bigger HP increase (after proper jetting of course) than just a lunch box/pods alone.
Hmmm. O0
Adding runner length and a bell mouth would likely increase port velocity at lower RPM's. The effects of longer runners diminish as RPM increases in nearly all applications though. This is why you will see race engines with single plane intake manifolds and with uber short runners. Many street motors (think of the old 5.0L H.O. engines in Mustangs and Thunderbirds) have longer intake runners to aid in low-end grunt; something that is very important for a street car.
-Turd.
I guess your saying the GS500 operates best in the higher rpm ranges so increased runner lengths wouldn't be a benefit.
Well I suppose that all depends on when the benefits of having a long runner begin to taper off. If you can see the benefits up to 8,000 RPM, then yeah, I suppose it would help out a bit. It also isn't realistic to believe that you'll see a difference on the street. At part throttle, I honestly don't think a longer runner upstream of the throttle plate is going to do a single thing for you. Unless you run WOT all of the time, nah, I don't think it'll help out.
-Turd.
"length" is a pointless worry before the bellmouth. You should worry about volume. Intake runner length and volume are after the butterflies, vortex between the butterflies and bellmouth, and air supply before the bellmouth.
Quote from: makenzie71 on October 11, 2006, 10:57:53 PM
"length" is a pointless worry before the bellmouth. You should worry about volume. Intake runner length and volume are after the butterflies, vortex between the butterflies and bellmouth, and air supply before the bellmouth.
No true.
Cars have had big power differences with different intake lengths prior to the throtte butterfly, but you are correct that most of the performance gains are from differeing te length after the butterfly.
What car has "big power differences" with altered lengths prior to the butterflies?
I don't know that length would have anything to do with it.... (before the butterflies)
And you guys I think are talking about a tuned manifold. (After the butterflies)
A tuned manifold basically lines up pressure pulses so that at a certain flow rate and rpms and a bunch of other crap the pressure wave helps cram more air into the cylinder.
It's obviously a complicated thing.
The change in the Ford Falcon's intake pipe that feeds air into the throttle body was changed from the ED to the EF to improve performance by 4% (6 kW's).
Also the length of intake trumpets on race cars change their power out put, and they too are located prior to the throttle body butterfly.
Ford Pinto motors are know to have lower RPM power increases of upto 30% with different trupet lengths.
Same goes for trumpets fitted to the V8 Supercars intake systems.
Quote from: galahs on October 12, 2006, 01:05:29 AM
The change in the Ford Falcon's intake pipe that feeds air into the throttle body was changed from the ED to the EF to improve performance by 4% (6 kW's).
I would like to see back to back dynos of the Falcon with the only change being the "pipe that feeds air to the throttle body"...because I'm sure that the different intake manifold, crankshaft, electric fans, and engine control didn't have anything to do with the power increase ED and EF bodies.
QuoteAlso the length of intake trumpets on race cars change their power out put, and they too are located prior to the throttle body butterfly
Ford Pinto motors are know to have lower RPM power increases of upto 30% with different trupet lengths.
Same goes for trumpets fitted to the V8 Supercars intake systems.
First, they're called "velocity stacks"...we've already discussed how the bellmouth does stuff. Velocity stacks have an effect similar to their name sake; their length alters the flow rate of the air from the air supply.
It's the air supply we're discussing. Pay attention.
And how does that differ to what I'm talking about!
The test on the Falcon was done first with NO other Change to the engine. JUST the air intake pipe. They did prototypes first with mandrel bent pieces of pipe before tooling up a plastic moulded piece. People can get the same gain by replacing the pipe on their ED by adding the EF pipe.
And are you trying to say a velocity stack/intake runners length prior to the throttle butterfly has no effect?
If so, are you saying the research I have sitting infornt of me is wrong,
If not, then we agree? Whats the problem?
I'm confused. :icon_confused:
Are you saying its just the bellmout and strightness of the intake tube that produces the increase in airflow.
If so I would like to argue you are incorrect, and that length of the intake runner prior to the throttle butterfly does pay an important part in the type of power delivered and I have dyno figures of the Ford Escort to back up my case.
Quote from: galahs on October 12, 2006, 02:46:14 AM
The test on the Falcon was done first with NO other Change to the engine. JUST the air intake pipe. They did prototypes first with mandrel bent pieces of pipe before tooling up a plastic moulded piece. People can get the same gain by replacing the pipe on their ED by adding the EF pipe.
Like I sad...back to back dynos.
QuoteAnd are you trying to say a velocity stack/intake runners length prior to the throttle butterfly has no effect?
If so, are you saying the research I have sitting infornt of me is wrong,
If not, then we agree? Whats the problem?
I'm confused. :icon_confused:
You need to pay attention to what you write:
QuoteCan't say it shortens it that much more than the distance to the airbox, so it wouldn't affect the tune too much in the regard.
You made no alterations to the bellmouth. The only thing you changed is supply.
I'm still confused as to the point your making?
Do you think changing the legth of the intake runners prior to the gs's butterfly will or will not make a difference? and why
The dyno graph I have infront of me is of an Escort run back to back with three different length trumpets before the butterfly flap. They are all the same diameter, with the same bellmouth.
Trumpets 12 inches long produced a power peak of 98kw's with a dip or power at mid-high rpm range
Trumpets 13.5 inches long produced 100kw's with no dip in power along the power curve
Trumpets 14.5 inches long produced only 88kw's. Much lower than the other trumpets results.
so the difference of 2.5 inches of runner length before the carbs could make a huge difference.
Here's me thinking out loud again....
currently a lunch box filter or twin seperate pods are the least restrictive intake availalble for the GS500.
What if one developed a y pipe intake.
(http://www.burnsstainless.com/Ypipe_std.jpg)
If you imagine, it would be smilar to this picture. The two out let ends attatched to the carbs and the large single opening would have a large pod filter clamped to it.
This could benefit the air intake by using the momentum of air sucked into the single opening created by the opposite cylinder.
The momentum would continue after one cylinder intake valve shuts, but this air would then change path down into the other cylinder.
this process works in car engines so I see why it couldn't provide a small gain to the ol GS500.
Quote from: galahs on October 12, 2006, 03:51:22 AM
I'm still confused as to the point your making?
Go back and read your first post, since quoted text eludes you. You said alteration to the bellmouth was minimal. You made NO alteration to the bellmouth. You didn't alter intake runner length or anything remotely similar.
And a y-pipe isn't the best idea as then you'll have two cylinders charing a common supply.
I know I didn't make any alteration to or even add a belllmouth. I'm talkig possibilities, not actuals. Maybe a diagram of my thinking is required.
As for sahring a comon supply, that shouldn't be a problem as long as the supply entry is large enough.
Tuned manifolds are a black art.
DIY's fiddle with such an item and end up porking something.
Shorter runers give more top end HP. Longer runners give more low end torque. It goes back to whoever made the 5.0 reference. On motorcycles, the carbs are almost on the head. This is because they are tuned to operate in the 6000+ rpm range. Notice a lot of your V-twins have a longer intake, partially because of design and partially they operate in a lower power band. As far as putting trumpets in front of your butterflys... that's some voodoo science. Same with runner length. It's lots of experimenting on a dyno that produces results.
Of course, me personally, I've done plenty of seat of the pants experiments on bikes and cars I've owned. Stuff doesn't aways work. Have fun, try stuff out but don't kill your budget.
I just think it could be worth experimenting with, and could be done fairly cheaply too.
I know on most race engines the entire air intake system is the 'black art' of making more horse power. Just think the GS500 could possibly benefit from a few R&D projects.
Intake system design is no more a black art than cutting somebody open to transplant a heart. Most people just don't understand it.
If you're truly interested in intake design I suggest reading "Scientific Design of Exhaust and Intake Systems" by Philip H. Smith and John C. Morrison. Both the authors did years of research on the design of induction systems for racing applications. Their reference papers are good too, but good luck finding them!
Fluid flow aside, what you're trying to achieve is "organ pipe" tuning of the intake manifold. The effect of carburetor throttle plates, runner length before the carb, trumpet, and the design of test gear are all discussed.
The problem for a street bike is designing a system that will both increase usable power in the cruising to full throttle area, but not sacrifice bottom end torque. I suggest that you do some reading on the Bessel horn and it's application to music. Musical instruments have evolved some interesting ways to alter the tuning of a long pipe that could be applied to a mechanical system.
BTW: The V&H exhaust system is textbook Morrison. I got curious one afternoon in the shop and measured it. It's specifications are right out of chapter 5.
Champion!
I' getting really interested in this sort of stuff.
Will have to chase this up for a read when I've got alittle more spare time :thumb:
I am planning to convert my GS500 to electronic injection (and run it with ethanol). I need to have an estimate of the length of intake which is inside the cylinder head (my "blue mare" is in another city and I don´t know when I´ll be with it). Did somebody measure that?
I already know the carburettor length is around 95-100mm.
I´ll make some acoustic calculations in order to know I may put off the air filter box and use smaller sports conic air filters. I need space for put electronic injection and ignition modules (there is not enough space on the under rear seat toolbox area). As there will be no acoustic interaction between cylinders due to the plenum, it is need to recalculate some things ad maybe project my double throttle body with some connecting pipe.
Quote from: laranjatomate on December 16, 2010, 10:42:03 AM
I am planning to convert my GS500 to electronic injection (and run it with ethanol). I need to have an estimate of the length of intake which is inside the cylinder head (my "blue mare" is in another city and I don´t know when I´ll be with it). Did somebody measure that?
I already know the carburettor length is around 95-100mm.
I´ll make some acoustic calculations in order to know I may put off the air filter box and use smaller sports conic air filters. I need space for put electronic injection and ignition modules (there is not enough space on the under rear seat toolbox area). As there will be no acoustic interaction between cylinders due to the plenum, it is need to recalculate some things ad maybe project my double throttle body with some connecting pipe.
The distance from the center of the intake valve face where it meets the combustion chamber to the center of the intake valve port where the throttle body attaches is almost exactly 3".
Why are you measuring the carb length? If you're doing electronic injection, you're not going to be using the stock carbs in any shape or form... you're going to have to switch to a throttle body designed for this use(well, unless you're not planning on doing direct injection, but still doing this with the stock carbs would be way counter productive.
Why are you planning on running a plenum?
Thanks for the 3" measurement.
I am fearous to build the throttle body with the same pipe length of the carburettor's one because I'll have no interaction between cylinders through the air filter box.
I still did not understand the phenomena [I have a book on intake and exhaust manifold acoustics, but it's complicated :{) ], but I know they exist and have strong influence on volumetric efficiency.
If I discover I need longer lengths, I accept even to design a corner and point part of the length downwards.
Once I want to have more than one ECU program (gasoline, ethanol economic and ethanol "nervous") I perhaps have attachable pipe parts for better torque in low or igh range. Maybe I do that.
I need do retire it because the programmable electronic ignition modules I'll use need this space and to be as nearest as possible the coils and spark cables.
Design Techniques for Engine Manifolds: Wave Action methods for IC engines.
DE Winterbone; RJ Pearson.
ISBN 186058179X
Theoty of engine Manifold Design: Wave Action methods for IC engines.
DE Winterbone; RJ Pearson.
ISBN 1860582095
Textbooks? Here's a summary:
84000/RPM = intake length in inches from carb bell mouth to intake valve.
Where the carb sits between the ends (bell mouth to intake valve) affects how peaky the power comes on. Dead center = highly tuned to length. Off center = less so.
Bell mouth design affects this as well, with a straight cutoff being (again) the most peaky and a gradual taper less so.
Two stokes are 42000/RPM=intake in inches, between reeds and bell mouth, BTW.
QuoteWhere the carb sits between the ends...
So it means I need to choose carefully the lontigudinal position of the fuel injectors?
Yesterday I was looking for some drawing or photography of the crankshaft. It means the cranks are opposite. So, one cylinder realizes work through gas expansion, the other does so, and the next two strokes without any fuel explosion.
Meditating about it I concluded the plenum (air filter box) volume is not important for resonance, due to this asymetry. If there is any acoustic interaction when some wave comes out the bell mouth of some cylinder, which could affect the other one; the opposite would accour at different times and with different intensities, affecting the vacuum equalization fo the carburettor bodies.
Finally I can concentrate my calculations on the pipe length without think on connections among them im my throtle body design. :{)
The texbool I cited points 2 phenomena in its 2nd chapter: The "organ pipe" in which length and diameter of both cylinder and intake pipe are taken into account and the pressure/rarefaction waves which occour when intake valve opens or closes (because this I required the camshaft phasing in anither topic), which travels towards the intake pipe until its entrance (the bellmouth), retunrning in the opposite sense (rarefacion returns as pressure waves and vice versa), while it may also reflects in the same sense when it reaches the coldsed valve. There is the possibility of some of these waves reach the intake valve about to close. If a pressure wave reaches the "close-to-close" valve, there is a little more of air intook.
If I have LaTeX installed on my computer I would put the formulae exported to some figure format. :{)
Wow, you drug up a old post.
QuoteSo it means I need to choose carefully the lontigudinal position of the fuel injectors?
I don't know about choose carefully, but the longitudinal position along the intake tract will affect things. This is usually a pretty easy thing to play with on the dyno or street... just get some diffferent length hoses.
Air box volume is as much about intake noise control as anything. It's easier to do the figuring on a straight pipe (which has easy acoustic equations) than a box, which is more like a helmholtz resonator.
I can tell you from experience with automotive tuning, that even now this is mostly done manually, cut and try, by OEMs. You basically start with the biggest volume box you can fit (bigger = quieter) and then play with it with heat tools / plastic welders until you get something that sounds and performs as you want it to. There's some analytical work (computer models) with the basics set by equations (what you're talking about) but at some point you'll just need to build it and run it and make changes to suit. That last bit is the "tuning" and it makes the difference between something that runs sweet vs. stubborn.