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

[scottly]

TG, if possible, please post the dyno charts in SAE, rather than DIN form, and with both foot-pound and horsepower scales equal; the torque in N/M confuses me greatly.

[gschuld]

I like the airbox work.

Another note on dyno use.  Often the units are read in kph or mph rather than rpm on dyno graphs.  Rpm is far more useful.

George

[turboguzzi]

after being in lockdown away from home for two and a half month, came back to milan two weeks ago......

Wasn't that 2 1/2 months locked up with the girlfriend TG?  Very small violin.

To the subject at hand.  Looks good TG.   Interested in hearing what kind of results you get.  Are you going to try to simulate higher speed air flow for the ram tubes?

no ram air effect, idea is just fresh, non heated air from the front intended. airbox is not sealed or meant to be pressurized. 

that said, even very serious dynos have usually fans that just cool the engine,
 for ramair testing youd need more of a windtunnel mounted dyno i'd think. At least that what kawasaki used when they started to introduce ramair in their big ZX models. generating 100 mph stream in front of the bike is not that easy

[simon#42]

all serious dynos have fans that are capable of pressurising the airbox  . without this you are wasting your time trying to tune a modern bike .

[turboguzzi]

well, could be well that im not so up to date,
available dynos for testing in my area have dwindled quite a bit in the last few years, the two i used in the past, one a dynojet, one a fuchs,  certainly didnt have the ramair fans, just big fans for general cooling. it's been a few years now since i used them

the one im going now belongs to a team's that does only vintage racing bikes...

agree that you'd need them with modern stuff, so are the ramair fans able to simulate variable speeds in step with rpm?

luckily im not into modern engines

[simon#42]

yes yossef , they used to lag behind speed which was a pain but now you can get a 250mph breeze into the air box faster than the bike can get there .   this is not new technology in the 90s we had a dyno built int the race truck . it was designed so a 250 aprilia would slot in and the air ducts would match up with the bikes air box . although it was mostly used to run engines in the bikes were always power tested before each gp .

[Korven]

Tg, do you think there is any point in going for the v8 brembo behind fork with the stock disc? Want a single disc but don't want a rusty disc for the road. Are those bmw discs you use?

[turboguzzi]

it was designed so a 250 aprilia would slot in and the air ducts would match up with the bikes air box . although it was mostly used to run engines in the bikes were always power tested before each gp .

wow, thats a fair bit of investment! was that for british 250 or world championship?

what kind of wind speed you started to see meaningful increased hp? reason i ask is that i dont think i ever got more than 180 kph from the 500/4 in the tracks we race. for all i know ramair effect would be negligible before 200 kph

@korven, the ones on my bike are stainless, off a 80's suzuki, i think form a GSx750 or something, same diameter as stock, just half the weight... they bolt on to the honda hub. and yes, i think that a bremebo f08 would be better that the stock caliper, and a F05 even better, at least you can find decent compounds for brembos. not easy to mount them to the oem fork though.

[scottly]

all serious dynos have fans that are capable of pressurising the airbox  . without this you are wasting your time trying to tune a modern bike .

I have never heard of a dyno with hurricane force fans? I suppose if the fans outlets were sealed to the ducts, there might be some pressure, but that's more like supercharging than ram air.

[simon#42]

that was world championships yossef , and believe me it was not the best funded team in the paddock !
the ram air has an effect from about 80 mph , it would be difficult for you to make a pressurised box work given the limitations you have within the rules . a twin spar alloy frame and a 30ltr airbox might be hard to sneak past the scrutineers .

scottly you dont need hurrricane fans . in real life only a proportion of the air enters the air box . from live racing data you know the air box pressure for a given speed , throttle opening etc . if you pump the air directly in to the airbox the fans dont have to be 10 foot across . oh and ram air is supercharging just without a mechanical pump .

[Tintop]

"..... i think that a bremebo f08 would be better that the stock caliper, and a F05 even better, at least you can find decent compounds for brembos. not easy to mount them to the oem fork though."

Little confused TG why you would prefer the F05 (with 32mm pad), over the F08 with a 38mm pad.  Space constraints, mounting issues?

[turboguzzi]

"..... i think that a bremebo f08 would be better that the stock caliper, and a F05 even better, at least you can find decent compounds for brembos. not easy to mount them to the oem fork though."

Little confused TG why you would prefer the F05 (with 32mm pad), over the F08 with a 38mm pad.  Space constraints, mounting issues?

yep sorry, my bad, mixed them up... the twin f05 do a fine job on the 500/4, also quite light
on the big Gpz i have twin F08...

[turboguzzi]

that was world championships yossef , and believe me it was not the best funded team in the paddock !
the ram air has an effect from about 80 mph , it would be difficult for you to make a pressurised box work given the limitations you have within the rules . a twin spar alloy frame and a 30ltr airbox might be hard to sneak past the scrutineers .

scottly you dont need hurrricane fans . in real life only a proportion of the air enters the air box . from live racing data you know the air box pressure for a given speed , throttle opening etc . if you pump the air directly in to the airbox the fans dont have to be 10 foot across . oh and ram air is supercharging just without a mechanical pump .

interesting that you saw effect already at 80mph but indeed, would also be illegal for my class. my research on airboxes, which was more on hellmoholtz resonance effects showed that current airboxes are rather small compared, way less than 30L, more like 8-10L even for superbikes. aligns with what you've seen recently?
scottly, in real life flowing air would reach stagnation at the duct entrance, and "non used air" spill over.... so for me it makes sense not to seal the fan to the fairing if you are trying to simulate real life condition. the charging effect is just the dynamic pressure due to velocity, IMHO

[scottly]

I'm not buying that a fan blowing on the intake ducts would generate a real-world ram air effect on a static bike.  It would take a wind-tunnel to duplicate the air-flow around the whole package at speeds over 100 MPH, where ram air starts to have any appreciable effect...   

[turboguzzi]

I'm not buying that a fan blowing on the intake ducts would generate a real-world ram air effect on a static bike.  It would take a wind-tunnel to duplicate the air-flow around the whole package at speeds over 100 MPH, where ram air starts to have any appreciable effect...

no problem, just tell it to these guys
https://www.dynapro.co.uk/RAM-Air%20System.htm
just retraced a previous post by simon....
thought like you too, that a wind tunnel would give a true simulation, but looks like this could be a good practical approximation

[simon#42]

yes yossef bikes unfortunately cant physically fit a 30ltr airbox . this is the size i would use where room is not so critical . have done some work on suzuki bike engines fitted to small cars and this size works well .  dynapro dynos are basic but very good value and well made . i have worked on a few others that are more advanced , scottly  would not believe these exist either .

[scottly]

Oh, I believe that someone touts a dyno with a BFF, but I don't see any evidence of it's effectiveness, at least on the link TG provided. Show me some real data, like a graph with and without the fans, what is the airspeed at the duct opening etc. I've got some magnets that when applied to the fuel lines line up the forces in the molecules of the fuel, resulting in a 5% HP increase as well as a 10% increase in fuel economy.

[slikwilli420]

gschuld wanted me to post an article on some Ram Air testing for some Kawi ZX bikes. Worth a read on the subject.

[simon#42]

an interesting enough article but it was published 25 years ago and things have moved on along way since then . he did have the right idea though . now it is possible to alter the airbox pressure with speed , load , gear , revs ,  etc  and factor in air density , temperature and humidity .

[gschuld]

 Yes, it was a caveman level approach at best.  The overall ram air conclusions left more of an impression on me than the methods used to attain them.

George

[scottly]

In terms of "boost", 10 millibars is .145 PSI. This is about the same as the change in static barometric pressure with an elevation change of 300 feet or so..

[simon#42]

that was with a 25 year old airbox design scottly . and as you know a non pressurised airbox works at negative pressure so the gain is much higher than you have calculated .

[HondaMan]

well, here's the offending bastard of a dog... this is one of three passing the power of 3rd gear, means it's the one most banged about when up-shifting/accelerating out of slow turns, i.e. most likely to break according to tuner flavio crispi.
not surprisingly, in most spares sites it shows as "no longer available".
following Flavio's advice i went for a new one rather than the used brent offer. logic being at least to start with a fresh one.  Managed to find a new gear in a little shop in a forgotten corner of europe, really by chance...

That looks like a C2 gear from a 750 I have around here...the circlip next to it climbed out of the groove because it was installed backward, letting the gear slide over far enough to engage with another one out-of-sequence.

[turboguzzi]

while the ramair discussion is reaching new heights, i'm still waiting for my date at the dyno. while speaking with the owner, he strongly suggested i weld a lambda probe bung to the 4-1. He has a wide band sensor and said it will speed up the jetting process. 

was thinking about welding it in the red sport in the pic of my marving 4-1  sys, if anyone has other ideas, will be great to hear, even if latitude for install is not that great actually.

@hondaman. that post is from 2.5 yrs ago... problem solved a while back
In any case, it's a C4 gear, PN 23471-286-010 from a 500/4, it's shared with the 350 twin, cant think it's a shared part with a 750, but who knows. the circlip was installed ok, nothing jumped it's just a well known weakness of the 500/4 box.

[Ramrod_Racing]

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.