Epoxy?

[rosco15]

That run was before I upped the main jet. You can see on the graph it goes lean around 7700. If you ignore the lean part and continue the graph up from 7700 it should have hit around 132. So that was my guess. I'd already made a couple passes and the bike was hot and others wanted on the dyno. So I took it home and changed the jet there. I will say this the bike revved faster and would 60' better with the ported head and bigger valves. Stock head and cams in the heat and sucky air I was running in the 10.30-10.40. With the ported head and megacycle cams I was running in the 10.20's. Stock head and pistons would run 10.60's in the heat.

I like those teeny tiny cams set around 110 110. I'm in mortal fear of blowing up. I used to have a high compression 1260 KZ1000. When I built it and did compression checks it pegged my gauge. It had 420 lift cams and I would use a car starter to fire it up. I promptly blew it up and ended up selling the bike as parts. I decided with this bike to go low compression, small cams, and spend my time racing and not working on it.

 

[Anonymous]

Whats interesting to me is that my fluid mechanics professor was talking about this topic last year. For whatever reason he was down at Indy and talked to a mechanic after looking that the intake. He noticed that they were not polished at all infact were rough and he asked about it. The mechanic told him that a polished intake was the last thing you wanted.

Also we did a lab on flowing a head and during our discussion he talked about whether or not bigger ports were better for intakes.

After looking over mototune, I was pretty impressed with what he was saying. Most people who get porting done also put in piston kits, I would like to see a few other people try something like this to put the theory to the test.He has put a few dyno charts on the website for a R6. How about others who have put larger ports on their bikes?

 

[Nerobro]

Somethign to keep in mind. Turbulant air flows across rough surfaces better than smooth. Intakes are full of turbulant air.

 

[Anonymous]

Porting (unless you're racing)

Unless increasing displacement, I recommend blend the heads - that's all. Take out the casting marks where they are abrupt. Don't remove any excessive material.

Then - glass bead the intake tracts. Hazy finish - gas tends to evaporate off of this surface well

Polish the EXHAUST tracts. Here it is OK because the gas has already been burned. I thought Neobros comment on rough surfaces may still apply here but I believe a smooth exhaust track is good. Question: does flow tend to get more or less laminer as flow speed goes up for a given volume and tract irregularity?

Different cam settings affect the turbulence and intake and "blowdown" velocities as well as the sizes of the intake tracts up to the valves. These affect "mach" speeds. Most critical cam is the intake cam and intake design since normal aspiration is only 14.7 lbs / in sq. and exhaust pressures are much higher.

Going up in piston diameter is the same as reducing the intake runner diameters - I would imagine. If your intake diameters are oversize, then of course putting in larger pistons will offset this. Increasing stroke also will increase intake charge speed.

Matching the upper and lower wall lengths in any radius makes much sense and prevents drag and "tumbling". This may be the biggest point for the epoxy method - that of the improved laminar flow...which is in effect enlarging the intake diameters BUT retaining the SPEED of the mixture. His main advantage is laminar in nature without trading off mach speed.

Speaking of laminar flow, anyone remember the Vance & Hines systems that had a baffle at the 4 into 1 collector. The premise of this baffle was to help the flow stay laminar as the "4" ran into the "1". Not sure if they worked, however the principle is recognized and respected.

And the sum of the cams, head design and displacement must come together to assure a high enough "mach" speed is attained to assure good mixing of fuel and air. It is about that mach speed. Speed too low - poor charging and mixing, too high - probably indicates a restrictive tract.

What I found with "Engine Analyzer" is that I couldn't have it all, midrange and peak HP and had to compromise.

I don't know if stock is too large or not to begin with. Anyone know how to measure mach speed on a complete engine? Good posts by all. - Dieter

 

[Nerobro]

the mach number has to be calculated. I am actually in the process of trying to build my engine in EA. And then we/i can use ea to tell me what is actually going on in the engine.

Anyoen who doubts EA.... My buddy builds his engines in EA first, and in the end comes out with an engine within two or three horsepower of the prediction. And this is on 450hp engines.

 

[Anonymous]

Unless increasing displacement, I recommend blend the heads - that's all. Take out the casting marks where they are abrupt. Don't remove any excessive material.

Decent advice. Usually the factory had an idea of what it wanted and cleaning up the casting flaws just achieves the ideal of their design.

Then - glass bead the intake tracts. Hazy finish - gas tends to evaporate off of this surface well

I have thought that this would be the optimal surface finish, but never seen anyone try it or heard of a tuner advocating it. It just seems perfect - rough enough to let any fuel droplets wet out the surface and go away and keep the boundary layer tripped, but smooth enough to not cause large amounts of turbulence that will cause the effective area to go down. Anybody ever tried this, or heard of tests done on this surface finish?

Polish the EXHAUST tracts. Here it is OK because the gas has already been burned. I thought Neobros comment on rough surfaces may still apply here but I believe a smooth exhaust track is good.

Shiny exhast ports are OK, because the flow is dry at this point. The surface roughness needed in the intakes is to prevent fuel droplets forming on the intake port walls and to promote good charge mixture. That is not needed here.

Question: does flow tend to get more or less laminer as flow speed goes up for a given volume and tract irregularity?

It gets less laminar. Port velocities are high enough that the flow will be fully turbulent, with very little laminar flow anywhere.

Matching the upper and lower wall lengths in any radius makes much sense and prevents drag and "tumbling". This may be the biggest point for the epoxy method - that of the improved laminar flow...which is in effect enlarging the intake diameters BUT retaining the SPEED of the mixture. His main advantage is laminar in nature without trading off mach speed.

The big hint of what he is achieving is that he flowbench tested the CBR600F2 head and kept filling in the port with clay until he started losing flow. Until the flow started to drop off, all he was doing was improving the flow characteristics in the port by optimizing the shape of the port. This is a great improvement, because it costs no flow, but is increasing the velocity. This improves charge mixing, turbulence in the combustion chamber and gives more resistance to detonation and faster charge burning. All good things that make more power everywhere.

Speaking of laminar flow, anyone remember the Vance & Hines systems that had a baffle at the 4 into 1 collector.

My ZX-9 OEM header has a vertical splitter that runs from the collector to the end of the header, where the tail pipe attaches. It separates the flow from side to side all the way out of the header. Is this similar to what you are describing?

I don't know if stock is too large or not to begin with.

Judging from Rosco15's results and things seen from other tuners, it would seem to be. The only way to know for sure would be to flowbench a head and do the clay test like Motoman did. If you can add a bunch of clay and keep flow the same, the port is too big. Now whether your valves are the right size is another story completely...

Mark

 

[Anonymous]

Mark M:

I did the glass bead and blending on a GS750 TSCC engine. I didn't do any epoxying.

I used an intake cam off a 1982 for 3 GS1100. So I got a little more lift and duration. Duration was about 232 if I recall..so not a really wild cam.

I piped and rejetted - Kerker header with highly modified FZR600 canister. Worked better than the megaphone - fatter power band and better peak.

Cams set at 107 108 or something..or do I have the numbers reversed for intake and exhaust. Intake opened at about 14 degrees BTDC and exhaust closed at about 46 degrees ABDC...do these numbers sound correct? Duration again was about 232 degrees on the intake cam. Exhaust cam was stock...AND IS THE SAME as the E-cam on the GS1100. So which cam is more important?

Got 60 HP (GS750EZ) at rear wheel at 5500 rpm. 77 RWHP peak at 8500 rpm with stock gearing and wheels. Redline was 9500....so I didn't set the bike up for max HP. Still had 69 RWHP at 11,200 - FYI. Would spin to 11,200 before valve float because I shimmed the valve springs 0.020". Stock springs on GS's are generally set too soft. Look for "cupping" or rounded valve seats when looking in radial direction ---> ( across the valve seat face....this means valves are bouncing which causes cupping. I actually had LESS valve and cam wear when I shimmed the springs.

I thought given the mods, I had much more HP than stock...and the intakes were glass beaded. To date I have not gotten a clear spec on what stock power curve was on the GS750EZ. Anyone know?

Blow a hair dryer across a matt surface finish and a glossy one. Surface tension will cause water to stick and glide across the glossy surface. The matt finish...less surface tension and water evaporates more readily. Didn't do a scientific analysis...but followed sound principles only.

The V & H exhaust had a baffle that was a cross + design and the four "quadrants" tapered to a point downstream. Each quadrant collected the individual pipe and helped straighten and transition the flow before coming together. Wasn't sure if the baffles had a little twist to cause the gas to swirl.

Shoot for maximum intake box and exhaust canister volume. It quiets the backpressure pulses created from the transition at the openings to "atmosphere" at either end. For example, when I put a larger canister volume on the exhaust end than the original megaphone, both midrange and peak jetting leaned out.....2 jet sizes. (Main jets affect needle mixture too). I got a jump of 7 HP peak with this mod. (and both the megaphone and FZR600 modified canister were set up for flow. Kerker HEADER is EXCELLENT though. Large 4 into 1 collector pipe and header pipe lengths are set very well. When I tried a tapered collector pipe reduced to 2 1/2 from 3 " original diameter, bike ran much worse and richer....so large collector pipe diameter and volume are very helpful. AND it's always how it all works together.

Very good post - you confirm my thoughts. - Dieter

 

[Jethro]

Woha, all this gearhead, greasemonkey, racer tech talk is making my head spin.

 

[Anonymous]

Got 60 HP (GS750EZ) at rear wheel at 5500 rpm. 77 RWHP peak at 8500 rpm with stock gearing and wheels. Redline was 9500....so I didn't set the bike up for max HP. Still had 69 RWHP at 11,200 - FYI

77rwhp @ 8500 rpm equates to a BMEP (Brake Mean Effective Pressure, a measure of efficiency) of 160psi. That is certainly respectable for an 80's air-cooled bike at the HP peak. 60rwhp @ 5500rpm equates to a BMEP of 192psi. This is a VERY good number for your engine at its torque peak. You must have done a good job with your tuning.

Kerker HEADER is EXCELLENT though. Large 4 into 1 collector pipe and header pipe lengths are set very well.

Good to hear you like the Kerker header. I currently have a Kerker canister system on my 1100. It is obnoxiously loud and I am in the process of fabricating a new megaphone tail pipe for it. I hope to fill in a hole in the torque curve between 3500-4500rpm with the meg and make it a bit quieter at the same time. The existing canister is also very small (3.5"OD x 12" long) and the core pipe is only 1"ID. My new muffler section will be 4"OD with a 2.5" core and should flow much better. We'll see...

Mark

 

[duaneage]

Tony brought up a great point in that the pulses from the intake tract are a problem to be dealt with. The stock airbox is set back and the carb boots are really velocity stacks that isolate the carbs from each other so that pulses from one carb do not affect another. Somthing to think about if using pods, the lack of a velocity stack can cause problems.

A larger airbox ahead of the carbs offers more compliance and dampening of intake pulses. It is also important to straighten the air flow ahead of the stacks as much as possible to fill them completely and a airbox helps.

I like to think that those contorted shaped boxes and filters may have a purpose, those engineers designed them that way for a reason.

 

[Anonymous]

Filling in Midrange Hole

Filling in Midrange Hole

Mark:

To fill in your midrange hole - I found increasing the exhaust canister VOLUME to be most important. I fiddled with both megaphones and canisters.....read on......

(I KNOW....theory says the tapered megaphone reduces backwards "reflected" pressure pulses.)

The problem is the VOLUME is so small on the megaphones......and if you make the megaphone volume larger....the tapered cone grows so big on the end that people think you have your pets head in there. OK....it's a stretch.

Get a large exhaust canister - steel if possible so you can braze , weld , modify brackets and adaptors on it.

I modified a steel 1993 FZR600 canister so the smaller outlet pipe within the large tip diameter "floated" within the larger diameter. Most came stock with just the small pipe flowing and a steel wall between the smaller pipe and the larger canister tip. The floating (used an internal tri-pod) allowed exhaust gases rushing out the tip to create a vacuum on the smaller pipe.

I also added additional internal pipes between the canister chambers (there are 3 chambers typically) and connected all the chambers with these internal pipes. Cut both ends off to do it then re-attached the ends.

Lastly, I grew the larger tip diameter from 1 3/4 inches to about 2 1/4 inches. This gave me a substantial boost in HP (+7 peak)

Bike had a deep sound and fairly quiet around town. When I got on it I got a little of the "ripp" that racer pipes have but MUCH less noise.

For anyone who knows 1982 GS750EZ- they come stock with 112 mains. I was running 130 mains with this setup and the primary intake box inlet opened up to about 3.6 square inches - up from stock and CO was about 3 to 4% - spot on for reliable street bike. Whoo hoo.....

I am pleased to hear my BMEP or output per liter was good. My figures were dyno'ed by the way.

Another key is that IF you open up your primary airbox inlet this much - you WILL have to run a more agressive taper on needles. THAT needle change gave me +15 HP in the midrange and finally allowed me to have lean enough crack off idle mixture and aggressive midrange acceleration. Gas mileage was about 43 to 48 MPG. You learn alot in 4 years of errors. Your setup and results may vary.... and require different changes -Dieter
PS: Compliments to the "duaneage" on velocity stacks and contorted box shapes.etc..etc.....his whole post is exactly right.

 

[Anonymous]

To fill in your midrange hole - I found increasing the exhaust canister VOLUME to be most important. I fiddled with both megaphones and canisters.....read on......

Ah, but did you fiddle with a true megaphone or just the V&H street meg system? Both the V&H and the Kerker megaphone systems are really just tapered core mufflers, as far as I know. They do not have a true megaphone followed by a muffler core, which is the best way to set it up. This means they behave like a typical straight tailpipe system, with a very small volume muffler, as you noted. Not really that good for performance. Mine will be a true megaphone with reverse cone on the end, followed by a small plenum chamber, then the muffler section.

On a straight tail pipe system, the muffler volume is very important to performance, as you found.

I am pleased to hear my BMEP or output per liter was good. My figures were dyno'ed by the way.

Your peak torque BMEP was excellent. Even the best current sportbikes are only making 195psi or so at their torque peaks, so you are in very good company.

Another key is that IF you open up your primary airbox inlet this much - you WILL have to run a more agressive taper on needles. THAT needle change gave me +15 HP in the midrange and finally allowed me to have lean enough crack off idle mixture and aggressive midrange acceleration.

My airbox was modified by the shop that the PO bought the bike from. The rear half is removed, with a large single K&N filter in its place. The jetting was reworked to suit this and the pipe. The bike dyno'd at 102rwhp @ 8500rpm and 69ft*lb @ 6500rpm. Not nearly as good as your effort... :? But I plan to improve on some of that. I don't know what the jetting specs are, aside from a note on the dyno chart that gives the main jet size as 132. I plan to tear the carbs down this spring to clean them and see what is going on inside them. I expect to have to increase the mains when I add my new tail pipe, as well, since I will be increasing the flow area by a factor of 6 or so... Depending on the carbs, I may look for a Dynojet kit to get the adjustable needles if the stock ones are still in there.

I never got much time on it last year (about 150km) because the fork seals are shot and the front brake pads are contaminated with fork oil, but it seemed to run pretty good, with maybe a slight lean surge at part throttle cruising. So, hopefully not too much sorting before I can start wearing it out.

Mark

 

[Anonymous]

Mark:

Yep - at 77 peak rear wheel this is like 112.9 for an 1100 motor.

HOWEVER - frictional losses in an 1100 motor might be higher and account for your 102 rwhp figure. Remember the 750 is a plain bearing motor as well. Do you agree? Your thoughts?

Next 60 at 5500 rpm is an estimate for the rpm, not the hp. The graph looked like it occurred at 5000 rpm but that is impossible. It was probably closer to 6000 rpm so I picked 5500 in the middle. If you see some variations in my postings-that is where that comes from. What would the BMEP be if it were 60 rwhp @ 6000rpm? List the formula too please.

Lastly, the 77 rwhp for a BMEP of 160 was a compromise. Running my lobe centers at 107 / 108 or thereabouts was not a setup for peak horsepower but rather for peak torque. If I had shifted my cam timing up around 110's I would have gotten peak horsepower. I would guestimate I could have gotten maybe 80 to 82 rear wheel horsepower. What do you think?

What fun. Incidently, I left the primary airbox on and ran a cone shaped large K & N filter - probably the same filter as you. The 750 and 1100 airboxes are identical - so I get a little "advantage" since my airbox size is larger relative to the swept volume of 1 cylinder. Heh heh.

My guess is if I opened the inlet orifice to 3.6 in sq. to match the outlet orifice of 3.6" sq. - that was the best I could do for orifice flow. The outlet size max limit prevented any additional gain by increasing the inlet side of the airbox over the 3.6 figure. To me it seemed intuitively better to keep the primary airbox for "quiet air" instead of removing completely. All of this assumes that the secondary air box (the 1 into 4 with velocity stacks) was untouched. Give me the formula and an answer on friction and so on questions. (6000 rpm vs 5500) and cam timing etc .....

 

[Anonymous]

HOWEVER - frictional losses in an 1100 motor might be higher and account for your 102 rwhp figure. Remember the 750 is a plain bearing motor as well. Do you agree? Your thoughts?

I wouldn't think that the losses would be much different. Maybe 1-2%, but not the 10% difference we see here. Don't forget, you have also cleaned up the head and added bigger cams and degreed them, while mine is stock aside from the intake and pipe. I want to degree the cams this spring and I hope to get another 3-4hp from that alone. If I was to assume another 5% gain from a port clean up, I would be right at the 112rwhp number. It just shows how good the basic GS four valve design was to achieve these sorts of numbers with very basic tuning.

What would the BMEP be if it were 60 rwhp @ 6000rpm? List the formula too please.

For 60hp @ 6000 rpm the BMEP is 176psi. Still pretty good for an old air-cooled beast, but not as amazing as the 192psi number...

The formula is:

HP = (Displacement x RPM x BMEP) / 793,000

Displacement = in^3 (this is total engine displacement)
RPM = RPM (obviously...)
BMEP = psi

I have also reworked it to get:

Torque = (BMEP / 151) x Displacement

Torque = ft*lb

These are both useful forms, since the twp places you are usually interested in bmep are at the torque and HP peaks. The bmep is maximum at the torque peak, since this is where your engine efficiency is maximum.

If I had shifted my cam timing up around 110's I would have gotten peak horsepower. I would guestimate I could have gotten maybe 80 to 82 rear wheel horsepower. What do you think?

I can't say. I have no experience with changing lobe centers and dyno testing the results. It certainly sounds like a reasonable estimate, given the effects I have seen elsewhere from changing lobe centers.

My guess is if I opened the inlet orifice to 3.6 in sq. to match the outlet orifice of 3.6" sq. - that was the best I could do for orifice flow. The outlet size max limit prevented any additional gain by increasing the inlet side of the airbox over the 3.6 figure. To me it seemed intuitively better to keep the primary airbox for "quiet air" instead of removing completely. All of this assumes that the secondary air box (the 1 into 4 with velocity stacks) was untouched.

I would enlarge the primary inlet more, to keep the airbox pressure as close as possible to atmospheric. I would think a ratio of 2:1 for the primary to seconday openings would be enough. You may be right about keeping the primary box and increasing the inlet area. Mine was done when I got it, so I will never know. Having a reservoir of still air is a good thing for carburation and performance. I figure I am not too badly off, as the filter is pretty well sheltered by the side panels and seat.


Mark

 

[Anonymous]

Thanks Mark.

When I talked about the airbox - I did not mean "sheltered air. Quiet air term meant that I have a sealed volume between the carb intake and the opening to the outside. This sealed volume acts as a damper to the inevitable shock waves that occur at any transition point. Your transition point would be at the filter.

Airboxes act like mufflers, or electrically, capacitors. I don't know all the theory, just that it is important to have quiet air unless running a tuned intake system which naturally has an RPM range for best performance.

I once had a fish tank with one of those vibrating pumps for the air in the fish tank. The tank buzzed all day long. I finally took a piece of aluminum pipe I had, cut a foot length and spliced it between the pump and the air tank. Immediately the noise stopped. The pipe acted as a reservoir or muffler and completely damped out the pumps noise. An airbox does the same thing which allows the bike to have better midrange since it quiets the intake pulses and assures intake air pressure is a constant. This is why it helps jetting too, since it is easier to find correct jetting related to a more linearly proportional intake vacuum instead of adding tuned pressure pulses to the mix.

If you can, pick up the book, "Scientific Design of Intake and Exhaust Systems". Much information in there, INCLUDING about megaphones and reverse megaphones.

Another thought....if you ran the stubby competition baffle in the Kerker systems, this allowed the start of the muffler to truly act as a megaphone AND the tip of these baffles had a small "reverse megaphone shape as well. The book I mentioned talks about muffler design AND optimum taper angle.

I believe done right, you can get as much flow AND a fatter power band with a properly setup airbox as with pods. - Dieter.

 

[Anonymous]

When I talked about the airbox - I did not mean "sheltered air. Quiet air term meant that I have a sealed volume between the carb intake and the opening to the outside. This sealed volume acts as a damper to the inevitable shock waves that occur at any transition point. Your transition point would be at the filter.

I understand. It does help to have the box if you can use it to tune for the resonances you want. New sport bikes are doing a great job of this.

If you can, pick up the book, "Scientific Design of Intake and Exhaust Systems". Much information in there, INCLUDING about megaphones and reverse megaphones.

I will take a look for it locally.

I believe done right, you can get as much flow AND a fatter power band with a properly setup airbox as with pods.

No question. The Jap bikes are doing really well in this regard, making tremendous power with super smooth torque curves and no noise. It is simply amazing that the current liter bikes make 150+rwhp, run on pump gas and come with a warranty. All while being as quiet as your neighbour's Taurus.

The only kink in this is that the airbox's put onto our bikes were not nearly as well refined and more power can be had simply by adding pod filters and freeing up the breathing. You may have found a very good compromise by modifying the airbox to increase flow, while retaining most of the benefits. After the many discussions here about jetting with pods, I am certainly going to keep going with my current set up until I feel there is no more to be had elsewhere. And next winter I may pull the head and have a go at cleaning the ports and trying the bead blast finish on the port walls for the finishing touches to a great motor.

This has been a great discussion, Tony.

Mark

 

[duaneage]

When I talked about the airbox - I did not mean "sheltered air. Quiet air term meant that I have a sealed volume between the carb intake and the opening to the outside. This sealed volume acts as a damper to the inevitable shock waves that occur at any transition point. Your transition point would be at the filter.

I understand. It does help to have the box if you can use it to tune for the resonances you want. New sport bikes are doing a great job of this.

If you can, pick up the book, "Scientific Design of Intake and Exhaust Systems". Much information in there, INCLUDING about megaphones and reverse megaphones.

I will take a look for it locally.

I believe done right, you can get as much flow AND a fatter power band with a properly setup airbox as with pods.

No question. The Jap bikes are doing really well in this regard, making tremendous power with super smooth torque curves and no noise. It is simply amazing that the current liter bikes make 150+rwhp, run on pump gas and come with a warranty. All while being as quiet as your neighbour's Taurus.

The only kink in this is that the airbox's put onto our bikes were not nearly as well refined and more power can be had simply by adding pod filters and freeing up the breathing. You may have found a very good compromise by modifying the airbox to increase flow, while retaining most of the benefits. After the many discussions here about jetting with pods, I am certainly going to keep going with my current set up until I feel there is no more to be had elsewhere. And next winter I may pull the head and have a go at cleaning the ports and trying the bead blast finish on the port walls for the finishing touches to a great motor.

This has been a great discussion, Tony.

Mark

The air in the airbox is reactive in nature and has impedance. THe air has compliance, meaning it can be compressed and it will expand at a given rate, forming a mechanical capacitor, but it also offers resistance to this effort. This gives it a reactive value.

The intake ports entering the airbox pull air from the space and the frequencies at which this occur varies greatly. At higher frequencies the airbox compliance falls and allows flow but at a price. If shockwaves develop into harmonics there will be standing waves inside the box, where an oscillation will occur. smooth corners, curves and unequal walls prevent development of standing waves.

At lower speeds the air volume becomes more reactive and that is where the damping comes in. Pods have almost no air volume so your on your own. The close proximity to the other carbs means they WILL be affected by the pulses from the adjacent carb.