Anyone done a tuned runner intake?

[ChromeRhino]

Tuned intake runner length is only effective at certain RPM levels, the correct length can be adjusted as shown above for this big block Chevrolet fuel injection set up. The correct length goes along with the maximum peak hp which is determined by the camshaft profile, valve diameter, etc, along with primary exhaust tube length and tubing size. The longer the intake runner length the more effective the intake reversion is at high RPM. Notice the different lengths in the injection system velocity stacks, why is that? because a big block Chevy has different lengths of intake ports in the cylinder head, the long velocity stacks feed the short ports in the cylinder head and the short ones feed the long ports in the cylinder head so that all the intake runner lengths will be the same for this engine. When everything comes together like it should be figured out in an engine only then can the maximum power level be achieved at a certain rpm so if our camshaft profile is supposed to make peak hp say at 6800 rpm then the intake and exhaust should be most effective at that rpm level. You don't adjust the length of the intake or the exhaust just because. There is a science behind the reason why.

That's actually not at all what I was talking about. That pic was a joke put up by someone else

 

[ChromeRhino]

Ahhhh....but keep in mind...when you start comparing those intakes to a small engine, the parameters ARE different!!!!

While theory may be the same....mechanics aren't. In the case of intake runners: well, you wouldn't think that air / fuel separation could occur in such a short distance....and that what you posted up has as little relevance as it does....

Now, I know. you're a fart smeller...lol...but you have to consider this: SCALE!

Those big block engines are moving HUGE amounts of air...(and 6" of extra runner there = maybe 1" on a small engine. (if that...!)

So the volume and velocity are going to negate some of the air/fuel separation...

Now.....the other shoe! Those engines can deal with a variance in A/F much better than a small engine. The A/F change is going to be more critical in the small engine.

Soooo...here's the thing: that separated fuel is going to find it's way into the combustion chamber with catastrophic results....(I'm not talking about damage or anything....but TUNING! )

I'm just throwing something out there for you to think about as you design this thing.

Not trying to be negative...just pointing out a couple of obstacles to keep in mind

Thanks Valve Spring Nazi... I mean, Poboy
I was looking forward to your thoughts and comments being that you might be more of a fart smeller than I am lol

Ok... I'm not sure what you are talking about when you say fuel separation. If you are referring to the fuel breaking up into smaller droplets, that actually helps makes the air/fuel mixture explode more efficiently. Its a good thing. As long as the ratio stays the same then there is no difference in tuning, it just makes slightly more power. A fatter fuel drop takes longer to burn than a smaller one and smaller drops allow much more air around it as a catalyst to get as big of a bang as quick as possible. A fine mist of fuel that's allowed to mix well with oxygen is what you aim for when tuning an engine.

I'm not sure why you think the air/fuel ratio is going to change. A carburetor works off from the air flowing through it by the vacuum that's caused in the intake runner. It's designed to give a certain amount of fuel depending on the vacuum that's pulling air through the carburetor. As long as you don't go past the limitation of the venturi and jet capabilities then there will be no problem. The air fuel mixture from the carb will continue to give the right amount of fuel to keep the ratio that you originally tuned it for.

I have used this setup in a real world environment back in the mid to late 90's and it actually worked better than I expected. We did fine tune the carb and we ran the choke for a bit to get it to fire up but other than that, I don't remember any special things we had to do.

I will build another one for the old 80's B&S I have now. I want to see if I can get a base dyno pull, one with a adapter and fancy filter and then one with the full tuned setup. I will not be taking the governor off or doing any other mods to this engine. When snow hits, it will be going back on the old snowblower again lol

If you could elaborate on the things I responded about that I may have misunderstood you on to give some clarity I would appreciate it.

 

[Poboy kartman]

Yes...what you are saying is all correct.

What I'm saying is that a long runner allows the fuel to do the exact opposite! The droplets get bigger and can settle to the bottom of the runner. Now, you have less gas than you started with. And at the least, an A/F mixture that performs differently because of the A/F change in characteristics.


Granted , we're talking minute differences here...but on a small engine, they can be a little more pronounced.

As you may well know...just on the short distance of an intake runner on an automotive head...you do not polish the intakes...for the very reason I'm alluding to.

 

[Toycrusher]

Same reason injectors are mounted at the end of the runner, pointing at the valve. You most certainly get fuel condensing and dropping out of the air mix quite quickly. I did something similar with hose to adapt an eBay slide carb to a 2-stroke 250 Honda Odyssey. It worked but after a little while it would load up on fuel and stall when coming back to an idle. Then I would need to wait for the engine flood to clear before it could be restarted. Not fun when it happens out in a muddy field.

 

[ChromeRhino]

Yes...what you are saying is all correct.

What I'm saying is that a long runner allows the fuel to do the exact opposite! The droplets get bigger and can settle to the bottom of the runner. Now, you have less gas than you started with. And at the least, an A/F mixture that performs differently because of the A/F change in characteristics.


Granted , we're talking minute differences here...but on a small engine, they can be a little more pronounced.

As you may well know...just on the short distance of an intake runner on an automotive head...you do not polish the intakes...for the very reason I'm alluding to.

Ahhh... gotcha. Ok. Very well. I will keep that in mind. I didn't think/notice it came into play on the other builds.

Yeah, I know you shouldn't polish the intak potrs on automotive heads for that reason... or atleasr be strategic about how and where you polish.

Thanks for the advise. I will keep a lookout for that possibility.

---------- Post added at 08:00 AM ---------- Previous post was at 07:40 AM ----------

Same reason injectors are mounted at the end of the runner, pointing at the valve. You most certainly get fuel condensing and dropping out of the air mix quite quickly. I did something similar with hose to adapt an eBay slide carb to a 2-stroke 250 Honda Odyssey. It worked but after a little while it would load up on fuel and stall when coming back to an idle. Then I would need to wait for the engine flood to clear before it could be restarted. Not fun when it happens out in a muddy field.

Oh, ok. Good stuff. I did mount the other ones above the original carb mounting height and to be honest, it was so long agi I can't remember if there was a symptom simular to whar you are describing or not. And to top it off, im not sure i would have recognized the symptoms or not. Its highly unlikely the guys that drove/used the engines would have even had a clue to what would have been going on had that circumstance come into play. It doesn't seem like there was but you know how rosey those hindsight glasses can be. Thanks for the insight and personal experience.

Thanks again, Toycrusher. I will try to design it in a way to avoid that issue.

 

[Poboy kartman]

Yeah...I played around with porting and polishing heads a little...and something I was playing around with was twisting the intake port. Also, grinding down around the valve stem hump at an angle so that the swirling charge would be directed towards the spark plug and follow the swirl pattern I'd set up


I even considered putting "rifling" in . The whole idea being keeping the fuel suspension agitated without restricting it. So , the basic idea is to keep the intake runners rough to create turbulence to keep the fuel in suspension.

The exhaust, on the other hand, smooth, and I polished those mirror smooth. Unfortunately, I got greedy and hit the water jackets....and never built the engine anyway, but I'll bet those heads would have performed well above normal expectations.

It was going to be a very different build for sure, because even with smog heads, I was going to have to increase volume to keep compression down...so I was going to dish the Speed-Pro hypers on the non quench side.

 

[ChromeRhino]

Yeah...I played around with porting and polishing heads a little...and something I was playing around with was twisting the intake port. Also, grinding down around the valve stem hump at an angle so that the swirling charge would be directed towards the spark plug and follow the swirl pattern I'd set up


I even considered putting "rifling" in . The whole idea being keeping the fuel suspension agitated without restricting it. So , the basic idea is to keep the intake runners rough to create turbulence to keep the fuel in suspension.

The exhaust, on the other hand, smooth, and I polished those mirror smooth. Unfortunately, I got greedy and hit the water jackets....and never built the engine anyway, but I'll bet those heads would have performed well above normal expectations.

It was going to be a very different build for sure, because even with smog heads, I was going to have to increase volume to keep compression down...so I was going to dish the Speed-Pro hypers on the non quench side.

Yeah. It would have been interesting to have seen flow and real world dyno numbers for that head.

What was the thinking on dishing the non-quench side? I guess it might make more sense to me if I knew better of the engine, head and style of piston you were working on.

I usually didn't tinker too much with the ports other than a little "cleaning up", D-porting on bends and port matching. I always thought it made more sense to keep up velocity. Well, that, and my dad knew one of the top guys in the country that did head work. I can't remember his name but I guess he is a legend. I learned a lot from my dad and him. I learned enough to not screw with ports unless you knew what you were doing! lol And I also knew enough to realize that I didn't know enough to go screwing around with the ports. Not much has changed since then. I still leave the majority of the port stuff up to the pros

 

[B.M.800]

I even considered putting "rifling" in . The whole idea being keeping the fuel suspension agitated without restricting it. So , the basic idea is to keep the intake runners rough to create turbulence to keep the fuel in suspension.

Ive been giving slight thought to setting up the lathe to cut rifling for a tater cannon and whatnot.
I wondered if it was worth the effort to build a rifled intake for a small engine.

If anything "Yeah, its got a rifled intake." for cool points. Right?



Question though, how would one determine the size and length of the intake? If I remember, I read something saying the intake ought to be the same volume of the cylinder. To my inexperienced mind, that seem reasonable...

For what its worth, Ide like to do some mild work to a vertical shaft briggs opposed twin. Dual carb "custom" intakes and whatnot.

 

[ChromeRhino]

Ive been giving slight thought to setting up the lathe to cut rifling for a tater cannon and whatnot.
I wondered if it was worth the effort to build a rifled intake for a small engine.

If anything "Yeah, its got a rifled intake." for cool points. Right?



Question though, how would one determine the size and length of the intake? If I remember, I read something saying the intake ought to be the same volume of the cylinder. To my inexperienced mind, that seem reasonable...

For what its worth, Ide like to do some mild work to a vertical shaft briggs opposed twin. Dual carb "custom" intakes and whatnot.

I came up with a varied set of formulas for the small engine runner design. Those papers are long gone now. I took some knowledge from when I build custom tuned ported boxes for subs, fluid dynamics formulas, and what I read and was taught about intake runner; intake; plenum, combustion chamber, cam, exhaust and cold air intakes to come up with my own formula. It was labor intensive just feeling comfortable to decide on the proper length and diameter. To be honest, I can't remember if the volume was close to the bore/stroke or not. I know the intake runner was pretty small and the intake tube was bigger than the venturi in the carb but I can't remember specifics.

That's funny that you mentioned a twin carb. I was planning a ratkart build with an old looking engine with twin carbs and even dreamed up a build with a "six pack" type set up using three carbs with an extended carb relocation tube.

 

[Poboy kartman]

Yeah....all this is above my pay grade....

Not that I can't do math....just too ignorant of the parameters to even start to figure volume for intakes....

Now...given the formula, I could do it forwards and backwards....but I have to bow out to the man that's toyed with it....(and I can relate...if I could remember half of what I knew at 20, I'd be a Mensa member....now...I'm just happy if I find the Mensa restroom!

 

[ChromeRhino]

Lol I hear ya Poboy.

If I knew half of what I THOUGHT I knew when I was 20 I'd be a f*ckin' genius! Lol

I understand where your coming from, Poboy.

I have kind of the same problem deciding where to start, but my problem is an initial overload of information. I have to slow down and sort it all out. And then if I don't write down my final results I have to repeat parts of the process to remember better what I was thinking. I think with a certain amount of feeling because my artistic and logical brain synopsis work in conjunction in a weird way. Its really difficult to explain.

My path of thinking is probably different than many others. Its hard to relate the how and why of my process. I have a very high functioning form of Autism, called Aspergers Syndrome, so I start with a innocent little thought and end up reading and calculating conditions and variations down to such a fine detail that I end up in quantum mechanics/physics lol To top all of that off, all of what I learned is stored in a RAM type memory cache to where I can get into a hyper-focused imagination type of meditation or trance where I can run real time tests to understand how everything works. I can tear ecerything down, run diagnostics, switch parts, redesign... anything that I have learned or have a grasp of that's retained in my RAM or ROM cache. On top of that it seems like I get a download of information that I have not ever encountered before. (I think Nikola Tesla had Aspergers syndrome because he described a gery simular thought process when trying to convey the way he thought) For instance, I was running imaginary diagnostics on a personal wind turbine generator you could build out of everyday modern items in a SHTF situation, when all of a sudden the coje can turbibe blades started vibrating and under load conditions at approximately a 26mph wind force. The blades started ripping apart and the whole thing flew apart. Somehow I got the knowledge that the wind caused a catastrophic harmonic imbalance due to the material composition and thickness and the pitch and cup angles (trim) were too aggressive for the application so it caused velocity choke. Now watching your creation fail in your own imagination due to tolerances, forces and variables you hadn't even consideredn or even known about, is a trip! P.s. I used plastic 2 liter pop bottles to construct the blades, adjusted the trim/cup angles down, added a ribbed reinforcement along the backside of the blades and everything worked very well. I built one and it put out a nice constant charge between 5.1 abd 5.4 volts at about 4.6-5.4Ma while mounted on the handlebars on my mountain bike at cruising speed in high gear (about 17mph or so). Perfect for charging smart phones

Every situation is different and its hard for me to relate all of the specific details of a process from years ago. I usually start another process for every challenge because there are so many variables to consider that will be different. I can't recall if I adjusted the design to prevent fuel seperation or not but a lot of the design process is kind of on an unconscious level where I just let my mind work the problems out.

I'm sorry. I went off on a tangent. Its hard to stay directly on topic when I encounter sleep deprivation.

 

[Poboy kartman]

I don't have Aspergers, but I basically do the same thing....to the point I do trial runs and testing in my head and make design adjustments.

 

[ChromeRhino]

Cool

 

[chancer]

Uh... huh, huhuhu "Assburgers!" huhuh

 

[Poboy kartman]

Uh... huh, huhuhu "Assburgers!" huhuh

What y'all eat in California is your business.....we don't need to discuss it here!

 

[ChromeRhino]

Lol You guys crack me up

 

[chancer]

What y'all eat in California is your business.....we don't need to discuss it here!

Hey! You said it there Whataburger guy.

 

[Poboy kartman]

Hey! You said it there Whataburger guy.

Nuff said....I see where this is going....a bottle of Whataburger mustard and a roll of Charmin headed your way....just remember....we use ground up cows here in Texas.

On a totally different subject: I like to eat calf fries...but lately they've been hard to find. Come to find out....Texas has been importing a lot of California steers...and it seems like nothing male from that state has much in the way of testicles anymore.

This trend of disappearing testicles in Californians was first noted in 1953 by the (semi) man and woman scientific team of Jimmy Aguy and Anita Hump. It was first attributed to an anomaly in the water supply....but later just decided that Californians were whimps.

The correlation between the decline in both cattle and humans in testicle size was harder to ascertain...and took much more in depth study. It was finally determined that of all things...it was DIET...both the cattle and humans were on a heavy grass diet...and that was the key!

 

[Denny]

You guys are forgetting history, in particular Chrysler racing history. A car called The High And Mighty was the very first vehicle with a tunnel ram. The car was built by a group of Chrysler engineers who had formed a drag racing team called the Ram Chargers. How the whole tunnel ram thing got started was because they were looking for a way to use the intake pulses from the other cylinders to stop reversion and help charge the other cylinders. Reversion happens at higher engine speeds where basically what happens there is no flow through the intake and then the flow actually turns around and starts coming back up through the carb. Their solution was longer tuned length runners. On these small and low rpm industrial engines you guys are looking for a solution for a problem that does not exist. Now if they were multi- cylindered, common intake manifold and carb engines then I would say you are on the right track. You all remind me of my personal hero Wile E. Coyote, using the wrong stuff for the wrong problem. On small engines at low rpm you can almost see the reversion but at high rpm not so much. As for multi carb set up No Freaking Way, you would kill the signal to the carbs they would not flow at all.

Denny

 

[ChromeRhino]

You guys are forgetting history, in particular Chrysler racing history. A car called The High And Mighty was the very first vehicle with a tunnel ram. The car was built by a group of Chrysler engineers who had formed a drag racing team called the Ram Chargers. How the whole tunnel ram thing got started was because they were looking for a way to use the intake pulses from the other cylinders to stop reversion and help charge the other cylinders. Reversion happens at higher engine speeds where basically what happens there is no flow through the intake and then the flow actually turns around and starts coming back up through the carb. Their solution was longer tuned length runners. On these small and low rpm industrial engines you guys are looking for a solution for a problem that does not exist. Now if they were multi- cylindered, common intake manifold and carb engines then I would say you are on the right track. You all remind me of my personal hero Wile E. Coyote, using the wrong stuff for the wrong problem. On small engines at low rpm you can almost see the reversion but at high rpm not so much. As for multi carb set up No Freaking Way, you would kill the signal to the carbs they would not flow at all.

Denny

Thank you, Denny, for that insightful information. That's precisely how I learned about this. My dad raced against them back in the day. He explained how it worked to me when I was about 10, which led me to further research and learn about how it worked several times since then. It's very interesting and more complicated then what I'm trying to do with an old 5hp single cylinder B&S. I figure I can try to use some of the same properties and design to improve efficiency. I think it's worth a shot. I could probably continue to argue with myself on whether it works or not or I can throw something together and see it works in a real world environment.

My thinking was only in using the pulse to "ram" the air/fuel into the combustion chamber. I thought with having just one path of air/fuel charge and a one cylinder configuration it would be possible to use some of the same properties to produce this effect. We were trying to improve off idle and mid range torque on two of the applications. From what I was told we did improve off idle and midrange performance. On the other application we tried to improve efficiency and performance near the rpm range at the limit of the governor and just above the governor allow for. I think we adjusted the governor to allow a little extra rpm's. Its hard to know for certain if we improved the power since we built the runner for the governor limit and then raised the rpm limit. It performed better at it's task but I was left to wonder if it was only from the increased rpm or from the runner. The owner of the engine was convinced that the runner improved the performance.

I figure I will try to repeat the procedures to see if I can gain performance on my own engine by tuning a runner in a similar fashion as before. If it doesn't work then it's not a big deal. I will tinker with it until I'm convinced it either does or does not help and then I will know for sure whether this is worth the effort in the future.