SV650 Power Curve
 

Just having a look at this power curve trace, its a before & after with the JHS ignition advance.

My question is, what causes the dip (circled) at 6K? I ruled out the timing retard because the dyno run would be done in a higher gear that doesnt get retarded??

Can anyone who knows their stuff take us through the ins and outs?

http://img.photobucket.com/albums/v6...powercurve.gif

Ahhh having a second look; maybe there isnt much of a dip apart from on the trace with the ignition advance mod.

So it could be that the ignition advance boosts torque lower down the rpm range more, creating an apparent dip at higher rpm where not as much additional torque is made.

Isn't that the point where the noise measurements are taken for EU compliance? I remember reading about this a long while back, that manufacturers retard the ignition at this RPM range to meet noise regulations.

But I could be wrong......

Certainly plausible that. It's not a power dip though, it's a torque dip, all it means is that it's not gaining power as fast as it was before. It's also in the area where the SV's most susceptible to jetting/breathing issues- stick a full system on a stock carbed SV and that's where it goes flat. It seems to be the point where the main jet size has the biggest impact on the needle circuit. You'd need an a/f line as well to see what's really going on though.

Luckypants wrote:

"Isn't that the point where the noise measurements are taken for EU compliance? I remember reading about this a long while back, that manufacturers retard the ignition at this RPM range to meet noise regulations."

I'm pretty sure I've read something similar. Aren't emissions also measured at this speed too? Something to do with TUV type approval and homologation but don't quote me.

Stock exhaust pipework?

Around 5.5-6k is what is called the emissions dip yes. However a race can soon sorts that out.

http://www.renegade-products.com/ren...es/17/1006.jpgMy bike in a former life, with Crank figures and Din corrected...but its the difference between the curves not the power, as this can vary from dyno to dyno

Re: SV650 Power Curve
 

Is that the same the tre mod ?
It made a nice improvement in low rpm torque !!

Nah, it's a different thing- an offset timing pickup that you fit to the flywheel, advances the engine timing. I think the JHS graph's generous for top end, or rather the comparison run's weak, but it's great for low end. Quite cheap too, if you can beg or borrow the flywheel puller. But Burner's run off to Cuba with mine :)