SV650 Power Curve - SV650.org

glade · 06-11-06, 03:59 PM

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?

glade · 06-11-06, 04:02 PM

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.

Luckypants · 06-11-06, 04:02 PM

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......

northwind · 06-11-06, 04:38 PM

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.

06-11-06, 04:54 PM

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.

johnnyrod · 07-11-06, 01:05 PM

Stock exhaust pipework?

Viney · 07-11-06, 01:59 PM

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

My 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

07-11-06, 02:11 PM

Quote:

Originally Posted by glade

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

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

northwind · 07-11-06, 02:54 PM

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

06-11-06, 03:59 PM	#1
glade Member Join Date: Aug 2005 Location: Leeds Posts: 431	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?

06-11-06, 04:02 PM	#3
Luckypants Moderator Mega Poster Join Date: Jul 2003 Location: Nr Ruthin Posts: 7,079	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...... __________________ "Your Viffer sounds like it is raising hell! Spot on." - Witchery 17/4/08 Snow Plough Appreciation Society - Member #3

06-11-06, 04:38 PM	#4
northwind Moderator Mega Poster Join Date: Jan 2004 Location: In the garage where I belong Posts: 17,083	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. __________________ "We are the angry mob, we read the papers every day We like what we like, we hate what we hate But we're oh so easily swayed"

07-11-06, 02:54 PM	#9
northwind Moderator Mega Poster Join Date: Jan 2004 Location: In the garage where I belong Posts: 17,083	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 __________________ "We are the angry mob, we read the papers every day We like what we like, we hate what we hate But we're oh so easily swayed"

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06-11-06, 04:54 PM	#5
glsuk1970 Guest Posts: n/a	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.

07-11-06, 01:05 PM	#6
johnnyrod Member Mega Poster Join Date: Jul 2003 Location: Doncaster, oop norf Posts: 2,128	Stock exhaust pipework?

07-11-06, 01:59 PM	#7
Viney Member Mega Poster Join Date: Jul 2003 Location: In the shadows to the left Posts: 7,700	Around 5.5-6k is what is called the emissions dip yes. However a race can soon sorts that out. My 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