Maximum RPM ??

deaks · May 3, 2004

Me and Mr 3Nanner are doing some noise testing on our 470 and 650 motards tomorrow.

We have a very accurate noise meter and also a clip on tacho so we can acurately make the engine rev to a certain RPM.

For UK static noise test we have to hold the engine at 50% of max RPM.

I'm guessing that Bergs are good for about 8,000 rpm?????

Can anyone let me know what the correct figures are?

We have a strict 98db limit to comply with. I tried an enduro can at our last race meeting, which was plenty quiet....BUT it really killed the top end on my 470 not allowing it to rev out properly.

We are trying to find ways of making the bikes quieter but still having the punch that a 2" bore zorst gives you.

I've been experimenting with creating a kind of swirl effect in the end can by creating a series of three swrils ( abit like an archimedies screww) by using a load of 1/2" self tappers on the perforated core. So far I've done half the length by putting a screw in every other hole, the other (first) half I have put a screw every six holes.

Any other ideas that dont involve spending loads of money are very welcome.

Any ideas??

Deaks

Any ideas??

maichusa · May 3, 2004

I don't know if it works but I have seen perforated sheet being twisted over a lenght and the placed thought the inner corepipe. So that the exhaust gas needs to flow along this twist but for some amount also can go through the perforated sheet. I hope you know what I mean.

LINEAWEAVER · May 3, 2004

4500 rpm is most often considered the US standard regarding stationary sound testing of large displacement singles.

Hope this helps.
Best Regards,
Dale

BundyBear · May 4, 2004

Deaks
A mate thought that the reason virtually all silencers are similar shape was that the 20 degree or so bend in the middle was significant in making them quiet. When I rebuilt & extended mine (it had been chopped virtually straight) I put another 80 degree short radius bend at the end & pointed it downwards. This bend is perforated like the rest of the tube. The muffler has 50 then 45mm full bore right through and is nice and quiet from the rider's position. I'm not sure how noisy it is from the side though as the noise the rider hears is surprising when you ride alongside a wall.

deaks · May 7, 2004

Thanks for the replies guys

Just to give you an update......I found out that we have to comply with FIM & ACU Noise testing regulations, which mean that you have to rev your bike to a mean piston speed of 11metres per second.

Luckily I found a really neat mean piston speed calculator on this fangled internet thing (ain't the web great :lol: ) My 470 with a stroke of 60.01mm has to rev at 5500 rpm to acheive the 11 metres per second. A 650 has to rev to 4050 rpm.

The good news is that the self tappers in a spiral seemed to have worked to some extent. It easily shaved 4-5db of the noise levels. I also repacked with stainless wire wool and e-glass. Before the mods my end can never got really hot. Now the alloy outer seems to get much hotter. This must mean that the gases are going into the sound muffling stuff more than before.

I have almost finished adding some more screws to make the 3 spirals run the length of the inner core.

I can post some pics tomorrow. I'm gonna retest for noise levels as well, and if I'm really lucky I'll get to go for a blast to check that the lovley top end hit is still there !!!

Deaks

Taffy · May 7, 2004

11 metres per second hey! how you going to keep the engine that slow?

:lol: :lol:

Taffy

LINEAWEAVER · May 7, 2004

Hi Deaks,
I was under the impression that the FIM encouraged dynamic (under load @ speed) sound level testing?

Here, the AMA to some degree has adopted a similiar approach in that during qualifying sound testing is performed on a fast section of the course.

Please keep us posted.
Regards,
Dale

Simon · May 8, 2004

LINEAWEAVER said:
Hi Deaks,
I was under the impression that the FIM encouraged dynamic (under load @ speed) sound level testing?

Here, the AMA to some degree has adopted a similiar approach in that during qualifying sound testing is performed on a fast section of the course.

Please keep us posted.
Regards,
Dale

Dale,

The FIM probably do, the ACU doesn't. The ACU stipulates a static test at approx. 50% of max. revs of the engine taken at around 3 meters behind and 1 meter to the side of the exhaust exit (on non tacho dorned singles at least).

Or something like that........

So all that is needed is some careful tuning :wink: :wink: :wink:

One good point about this process of testing I suppose is it avoids the sort of stuff where on dynamic track side testing you can just modify your silencer to point down and away from the measuring equipment......

What I have to wonder is....... are the Honda and Yamaha 450s being tested and how on earth are they getting through the test? Are any bikes actually being tested and failing or is this sound rule just another bogus rule not being applied? Lets face it, the previous 102db was never tested now was it?

Last time we tested a yzf450 it was shovelling a nice 136db on stock system.

Deaks, have you actually been tested at Pro-SM?

Simon

deaks · May 11, 2004

We will be doing static testing to ACU regs :cry: at the next meeting (blyton) as long as my mate Bob has got the clip on tacho in time.

Until then we are being monitored on the track and 'offenders' being told that they are too loud (or louder than the others at the very least).

And suprise suprise, the main offenders are CRF's and YZF's. Interestingly two of the quietest bikes were Rob Cross's 650 & 450, add to that the fact that Rob dominated both classes, it proves that noisy does NOT equal fast.

On the 650 Rob runs a full FP system and on the 450 he had standard headers and some unknown aftermarket end can.

I've now managed to get mine very close to 98db, just need to make sure that the power has not been hit much (tonight all being well).

Deaks

deaks · May 12, 2004

Yeee Haaaa

The Likle Berg breathes again.........

I rushed home from work last night. Quickly put number plate and lights on, and took her out for a blast and a run on the 'seat of the pants' dyno.

Well, the results were good. Unlike with the enduro end can fitted, the mid and top end pull is very strong.

The blunt term that we tend to use in my locality is 'she revs like a bast*rd'.

A good result for racing, noise level now within (just) limit of 98db and no big powerloss which is important when your racing in the open class on a little 470 !!

Here are a few pics of the mods I done to the inner core of the end can.

Deaks

Taffy · May 12, 2004

plagurism is rife throughout this site!

it's a terrible thing!

so it goes like f***!
warp factor 7!
screemin baby!

well done though!

Taffy

deaks · May 12, 2004

Taffy said:
plagurism is rife throughout this site!

it's a terrible thing!

so it goes like f***!
warp factor 7!
screemin baby!

well done though!

Taffy

I had to look that word plagurism in the dictonary

still not quite sure wot you meant though.

If it was a compliment......Thanks mate I'm flattered

If it was a dig......Then I'll choose to ignore it :wink:

The well done bit I understood so thanks for that.

Deaks :lol:

Taffy · May 12, 2004

out and out copying.... :twisted: :twisted:

Taffy

deaks · May 13, 2004

Taffy said:
out and out copying.... :twisted: :twisted:

Taffy

Has someone else done the spiral jobbie before then?

Works great on my 470, but was ***** on my mates 650.

Deaks.

I know what you mean about the copying bit, I did a google search yesterday on FP zorsts and stumbled across a site with a project 650 bike.....Bugger me at the bottom of his page is my little animated sig pic I created for the visordown motard forum.

I dont use it here cos it's a bit rude for our 'merikan friends.

Maximum RPM ??

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