Topic: CB500/4 racer resurrection - airbox finished, didnt quite work....

[turboguzzi]

if anyone has other ideas, will be great to hear, even if latitude for install is not that great actually.

When we see special headers for development engines here at work, the bungs are on the individual head pipes rather than down on the collector. Can't find any to take a picture of, but about 75mm from the flange if i had to guess off of memory. They want to know the a/f ratio of each individual cylinder in case there's some imbalance.

Would be good information to have, but you'd likely be creating a lot more work for yourself.

wow, you caught me off guard here, not even sure he has 4 A/R channels, he said one sensor... am always changing same jets for all four cyls...
if it's still one, any recommendations regarding position?
Sounds like a nice job, what type of dev work you do on engines?

[simon#42]

the ones we get are 100mm from the exhaust valve which is probably similar .

[simon#42]

here is an exhaust from a yamaha m1 motogp bike , the sensor is slightly further away from the exhaust valve . this is a racing exhaust rather than a testing exhaust .

[Ramrod_Racing]

I’m a test engineer for Yamaha ROV’s and ATV’s. Engine development and production is still handled by Japan, but they supply us the units to build our prototype vehicles with and often send engineers to collect data and tune at various riding areas here in the US.

I would guess that Simon’s 100mm figure is more accurate than my estimation, but they’re set to the same position based on some standard from YMC (our internal short-hand for the mothership in Iwata).

[turboguzzi]

so you work for big Y and ride a Honda for fun? Wait till your boss hears about it...

tnxs for the info, some decisions to make

[MRieck]

here is an exhaust from a yamaha m1 motogp bike , the sensor is slightly further away from the exhaust valve . This is a racing exhaust rather than a testing exhaust .

That's where you want them especially for race use. I am not an engineer BUT good friends are in the area internal combustion.

[slikwilli420]

so you work for big Y and ride a Honda for fun? Wait till your boss hears about it...

tnxs for the info, some decisions to make

And he shades his bike between rounds with a Yamaha canopy. 😃

[scottly]

if anyone has other ideas, will be great to hear, even if latitude for install is not that great actually.

Located aft of the joint of the tail pipe and collector may give false readings from air leaks?
My dyno has the sensor mounted on the rear in an aluminum block, with the business end in a cavity. There is a 30" long 1/4" diameter copper "wand", or "probe" that is inserted into the tailpipe, and a vacuum that sucks exhaust gases through the wand and past the sensor. No welding of bungs required, and you are not tuning a fuel injected engine.    

When we see special headers for development engines here at work, the bungs are on the individual head pipes rather than down on the collector. Can't find any to take a picture of, but about 75mm from the flange if i had to guess off of memory. They want to know the a/f ratio of each individual cylinder in case there's some imbalance.

Would be good information to have, but you'd likely be creating a lot more work for yourself.

wow, you caught me off guard here, not even sure he has 4 A/R channels, he said one sensor... am always changing same jets for all four cyls...
if it's still one, any recommendations regarding position?
Sounds like a nice job, what type of dev work you do on engines?

[johno]

Just to be different , firstly I would only have one sensor for your level of competition, secondly I would ask the dyno operator where he wants it as different manufacturers of them give specifications as to where they go and he will know that.

[johno]

re the sensor position Yossef, u normally move faster than greased lightening so what are u thinking ?
I run a NGK system and their instructions were between 100mm to 200mm after the collector so I placed mine on the side of pipe at 150mm.    Approx 50mm or so closer to collector than your red dot.

I guess not too close to collector to give the individual gasses time to mix but not too far to allow cool down of gasses and introduce undesirable chemicals ie water etc

[simon#42]

one of the the reasons the manufacturer recommends placing the sensor further away from the engine is for longevity . you will get a much more accurate reading  100mm from the exhaust valve but the temp will drastically reduce the life of the sensor . not a problem if its only to be used on the dyno  and there will be no condensation or bleedback to mess up the results .  having said this i am sure either position would work well enough for yossefs needs . he can decide how accurate he needs to be .

[turboguzzi]

someone sent me a link to this pdf, essentially what's written in point 4.3.1... but he also added that having heating internally, not a show stopper...

[turboguzzi]

well, back from a very sweaty afternoon, and in case you were holding your breath, then here's the bottom line: both the "double stacks" as well as the complete airbox idea just didnt work, best results was always with the stock CR stacks.... so much for nice theories applied.

Problem started with choosing the worst day possible to dynoing, we are having a serious heat wave here, like 33C / 92F, humidity in high 70% and on top barometric pressure was low (dont ask me how many millibars...) So even if i arrived with the jetting i used in the past (like 10 yrs ago..), it took a long time to arrive to a baseline jetting, it was running completely rich.
After running a light run-in program to bed the rings, with engine sounding quite odd even after all these years we lost some time discovering that one main jet undid itself so it was running on 3.5 cyl.
That sorted, lambda kept showing rich-rich-rich and it took two main jet changes and one needle height drop for the curve to clean up and the engine to start pulling cleanly.
We did more runs to nail the ign timing as thats one area were my marks on the plate couldnt be trusted. Need to check now with the timing gun to see where we ended up...
Time to try the double stacks, and the engine just didnt like it, pulling but hesitating from mid revs to the top, even if it didnt quite hurt max hp which was just 1HP down. Adding the complete Airbox, was more of the same.... wasnt a weak run, but you could hear that the engines was not liking it, graph zigzaging and rough, rather than smooth and showing wonderful gains across the range. Can the idea be made to work? maybe with a new design and a lot of development time.
Still need to work on the graphs, but the actual results were not that good, seen these numbers 13 years ago when i first dynoed the bike and before much of the development work... but dyno operator said that the conditions were so severe that even correction factor cant really make up for them. will give it another try after the summer in the name of science..
here's one of the runs for you guys

[johno]

Its always good to leave the dyno room TG, even if things don't go well it gets rid of a lot of anxiety 

[Sam Green Racing]

Hey TG, don't worry mate, if we don't experiment, we get nowhere.
OK, you picked the wrong day but like the dyno man said, even with the correction factor taken into account, they can't be 100% sure of an accurate figure.
All my experience at tuning was with small Honda twins from the 60s and it went on for years, right through to when I was racing the big 4s in America.
I was at Mike Reicks one day when a guy brought in a CB160 motor converted to 200cc as that was the class he was running in, and he wanted mike to port the head
He was a bit pissed off with running at the back of the field and finishing last all the time.
I looked at the motor and told him to change the cam and throw away the 200 pistons and to replace them with CB175 ones plus 1mm over size.
He got the parts that I told him to get and Mike ported the head and built the motor and first time out, he went from finishing last to finishing first with no problems.
There is no substitute for experience and experimentation but you must try to book dyno time when the weather is similar to your last dyno pull or the temps that you would normally race in.
Take care mate and stay safe.

Sam.

[scottly]

TG, rule-of-thumb is that you lose 1% power for every 10* F increase in temp. The power loss for humidity has much less effect, and the barometric pressure has the greatest effect. I found a calculator that shows that every decrease of 1" of mercury reduces power by about 4%, which more or less jives with my dyno results. (Leave the altitude at 0 feet; the engine only cares about the actual barometric pressure.)
Your conditions were not so severe that the dyno software could not calculate the correction factor? What did the chart show? I think the worst case I've seen was an SAE CF of 1.18 or so?
http://www.csgnetwork.com/relhumhpcalc.html

[turboguzzi]

Scottly, i will definetely will post them, its just the printed graphs i got have km/h as horizontal scale, I need to translate through gearing to rpm. more important, I asked for the data file, as the printed charts make it really difficult to analyze the torque curve vs. rpm, not to mention putting graphs one over the other...

so needs time which between work and preparing for first race i simply dont have.... race is in two weeks, still need to do quite a bit of work on the bike, organize my stuff, go fo r ashake down or two, etc.

to satisfy your curiosity, best run yesterday was 55.6 hp, but like i said, i have a graph from 2008 when the bike was just at the beginning of development, with 27mm VM carbs rather than the current 29 CRs, less compression, etc. and it is also 55 hp! that dyno was inertial, yesterday's one magnetic brake, which one is "more right"? cant say...

[simon#42]

probably the magnetic one , inertia dynos are not very good . they are cheap though and thats why people use them . you should always try to use the same dyno  . i have seen huge variations between them .  dont be downhearted because you didnt see big numbers yossef sometimes the only way to go forward is to find out what doesnt work . most of the work gp teams do makes the bike worse !

[scottly]

I was wondering what type of dyno when the operator rolled on the throttle so slowly. Did he have ignition pick-ups connected?

[turboguzzi]

it's this one, double roller, magnetic brake.

not really clear from the description, but seen the magnetic coil array with my own eyes..

https://www.bapro.it/en/motorcycle-dynos/2-rollers-bpm-2r-hp

[johno]

Its interesting stuff TG, the new double stacks and air box evaluation. Considering it was a rebuilt engine and on different dyno in different air I don't think you should be disappointed in the numbers yet.
Re the double stacks, Given the % increase offered by Yoshimura and the Captain which were likely done on an engine dyno and the increase was minuscule in real terms.
 Also Given your goal was to provide clean air to carbs while racing the dyno was no place to test that , no temperature and airspeed past the engine, I reckon you should persevere with them at a track practice, with and without, ya never no until the big girl sings they say 

[turboguzzi]

johno, was having a beer with Ricardo the other day and when he saw the graphs he suggested that maybe the rough running with the double stack/airbox was simply because the engine was now getting more air and needed to be made richer again...
would have chased it, but it was almost 6 PM, so day ended there. owner has a family, etc. so no all nighters...
i just noted that as a plain bolt-on, the idea didnt work, but another day at the dyno could bring more insight, it's just another 200 euro...
ill do a shake down track session this week, and then race is coming up  fast, quite a lot to organize till then. further inquire will be after it.



 

[scottly]

johno, was having a beer with Ricardo the other day and when he saw the graphs he suggested that maybe the rough running with the double stack/airbox was simply because the engine was now getting more air and needed to be made richer again...

What did the dyno AFR read?

[turboguzzi]

the channel was directly in millivolts from the probe, owner said it had to be a certain value to be right and to go down in jets. told you it was a bit complicated.... just dont have time to process the graphs now, will do after the first race in two weeks, patience needed....

[scottly]

someone sent me a link to this pdf, essentially what's written in point 4.3.1... but he also added that having heating internally, not a show stopper...

Read page 7 of that pdf; the wide-band sensors use milliamps, not millivolts, and have to have a "controller" to convert to a voltage. Why didn't the dyno software do this? Why is it so complicated? I think you need to find a different dyno operator.