Zongshen ZS200 exhaust length tuning (cam specs anyone?)

bones33 · 09-02-2010, 12:25 PM

Does anyone have information on the exhaust cam timing events for the Zongshen ZS200? In particular I'm looking for degrees before bottom dead center (BBDC) that the exhaust valve opens. This is to plug into an exhaust length tuning formula.

I searched the tw200 and xt200 forums with no success. Available Zong manuals have no information on this.

The FMF silencer is on it's way. While hacking up the exhaust, I'd like to tune the length to about 7000 rpm for the freeway, if it's reasonable.

Thanks in advance!

SpudRider · 09-02-2010, 01:52 PM

I have compared the Zongshen, 200GY-2 camshaft, and the Yamaha, XT200 camshaft; they are identical.

I imagine the Yamaha, TW200 camshaft is also the same.

I don't have the information you seek. However, I encourage you to post your question on the TW200 forum; if those guys don't know the answer, no one does.

Your posts will be welcome on the TW200 forums; however, if you prefer, you don't need to identify yourself as a Zongshen owner.

Spud

bones33 · 09-02-2010, 04:57 PM

Ok thanks I'll give it a try. By the way, Webcams makes a performance cam for the TW that should translate to the Zong, and be interesting to some here. Thier specs only show duration, not timing.

bones33 · 09-02-2010, 06:15 PM

OK well I'm a ding dong. Clicking on the only cam profile ID on the Webcam site for the TW200 gives the timing data.

The Webcam is a mild cam so I'll randomly subtract two degrees from the BBDC number of 44* to approximate stock. Eng-tips.com had a post that gave a formula of Pipe Length = ((850xED)/RPM)-3 where ED = 180*+*exhaust opens BBDC. Plugging in 42* for the BBDC to get the ED, then 7000 rpm results in 11.8 inches for the first harmonic. Seems kinda short.

I still need to find another calculator to validate this as well as a calculator to find the second, third and fourth harmonic lengths. I'm guessing the end of the tailpipe should end up being at about the second or third harmonic.

Then there is the black art of pipe diameter. I'm not going to go there.

bones33 · 09-02-2010, 11:49 PM

I found another site that has a calculator: http://www.mez.co.uk/mezporting/exhaust_length.html

Thiers calculates for the Webcamshafts 40a cam values an exhaust length from the exhaust valve to the first diameter change (muffler) of 24 inches, which is I think more realistic that the other calculation from my experience. The inside diameter of the pipe should be 1.137 inches. The tail pipe (after the diameter change) should be 22.905 inches.

Measuring the stock header I get about 42" to the muffler start. According to the calculator that targets 4250 rpm, not the 7000 I was hoping for.

So, assuming the calculator is approximately right, tuning the exhaust for about 7000 rpm isn't really practical unless I want to make my own header pipe. This is with the Webcamshafts cam 40a cam. As it is a mild cam the stocker is probably not far off, maybe a couple of inches at worst.

You know that fake expansion chaimber heat shield? If the header pipe actually had a diameter change around there to produce a pulse it would be about right for freeway speeds. It might add that extra .612 horsepower we are searching for. Guess those styling guys aren't so crazy after all.

mizke · 09-03-2010, 02:18 AM

Quote:

Originally Posted by bones33

.

You know that fake expansion chaimber heat shield? If the header pipe actually had a diameter change around there to produce a pulse it would be about right for freeway speeds. It might add that extra .612 horsepower we are searching for. Guess those styling guys aren't so crazy after all.

maybe thats why fmf has that power bomb chamber in all of their exhaust systems now.. always wondered if that thing actually did any good or was just a selling thing

FastDoc · 09-03-2010, 12:41 PM

What about something tuneable like a Supertrap?

Weldangrind · 09-03-2010, 01:52 PM

You could tune the exhaust with a pressure guage.

You'd need to weld in a small bung on the header pipe, perhaps just past the first bend and then connect a guage to it. Idle pressure should be around 1.5psi (or less), 2000 rpm should be about 3psi and 4000 rpm could be anywhere between 4psi and 8psi. If the pressure shoots up to an abnormal reading, there is excessive back-pressure in the system, especially if it continues to climb while holding a specific rpm.

I think I found this info in an old Car Craft article.

09-02-2010, 12:25 PM	#1
bones33 Join Date: Aug 2010 Location: Olympia, WA Posts: 36	Zongshen ZS200 exhaust length tuning (cam specs anyone?) Does anyone have information on the exhaust cam timing events for the Zongshen ZS200? In particular I'm looking for degrees before bottom dead center (BBDC) that the exhaust valve opens. This is to plug into an exhaust length tuning formula. I searched the tw200 and xt200 forums with no success. Available Zong manuals have no information on this. The FMF silencer is on it's way. While hacking up the exhaust, I'd like to tune the length to about 7000 rpm for the freeway, if it's reasonable. Thanks in advance! __________________ Member: Zongshen world domination plot.
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09-02-2010, 01:52 PM	#2
SpudRider Join Date: Jul 2008 Location: Idaho Posts: 25,054	I have compared the Zongshen, 200GY-2 camshaft, and the Yamaha, XT200 camshaft; they are identical. I imagine the Yamaha, TW200 camshaft is also the same. I don't have the information you seek. However, I encourage you to post your question on the TW200 forum; if those guys don't know the answer, no one does. Your posts will be welcome on the TW200 forums; however, if you prefer, you don't need to identify yourself as a Zongshen owner. Spud __________________ Spud "Never argue with an idiot. He will drag you down to his level, and beat you with experience." Mark Twain 2015 Zongshen ZS250GY-3 (RX3) 2006 Zongshen ZS200GY-2 (Sierra 200) 2005 Honda XR650L 2004 Honda CRF250X 1998 Kawasaki KDX220 Mods made to my Zongshen ZS200GY-2: http://www.chinariders.net/showthread.php?t=6894
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09-02-2010, 04:57 PM	#3
bones33 Join Date: Aug 2010 Location: Olympia, WA Posts: 36	Ok thanks I'll give it a try. By the way, Webcams makes a performance cam for the TW that should translate to the Zong, and be interesting to some here. Thier specs only show duration, not timing. __________________ Member: Zongshen world domination plot.
	0

09-02-2010, 06:15 PM	#4
bones33 Join Date: Aug 2010 Location: Olympia, WA Posts: 36	OK well I'm a ding dong. Clicking on the only cam profile ID on the Webcam site for the TW200 gives the timing data. The Webcam is a mild cam so I'll randomly subtract two degrees from the BBDC number of 44* to approximate stock. Eng-tips.com had a post that gave a formula of Pipe Length = ((850xED)/RPM)-3 where ED = 180+exhaust opens BBDC. Plugging in 42* for the BBDC to get the ED, then 7000 rpm results in 11.8 inches for the first harmonic. Seems kinda short. I still need to find another calculator to validate this as well as a calculator to find the second, third and fourth harmonic lengths. I'm guessing the end of the tailpipe should end up being at about the second or third harmonic. Then there is the black art of pipe diameter. I'm not going to go there. __________________ Member: Zongshen world domination plot.
	0

09-02-2010, 11:49 PM	#5
bones33 Join Date: Aug 2010 Location: Olympia, WA Posts: 36	I found another site that has a calculator: http://www.mez.co.uk/mezporting/exhaust_length.html Thiers calculates for the Webcamshafts 40a cam values an exhaust length from the exhaust valve to the first diameter change (muffler) of 24 inches, which is I think more realistic that the other calculation from my experience. The inside diameter of the pipe should be 1.137 inches. The tail pipe (after the diameter change) should be 22.905 inches. Measuring the stock header I get about 42" to the muffler start. According to the calculator that targets 4250 rpm, not the 7000 I was hoping for. So, assuming the calculator is approximately right, tuning the exhaust for about 7000 rpm isn't really practical unless I want to make my own header pipe. This is with the Webcamshafts cam 40a cam. As it is a mild cam the stocker is probably not far off, maybe a couple of inches at worst. You know that fake expansion chaimber heat shield? If the header pipe actually had a diameter change around there to produce a pulse it would be about right for freeway speeds. It might add that extra .612 horsepower we are searching for. Guess those styling guys aren't so crazy after all. __________________ Member: Zongshen world domination plot.
	0

09-03-2010, 12:41 PM	#7
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	What about something tuneable like a Supertrap? __________________ Happy to serve.
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09-03-2010, 01:52 PM	#8
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	You could tune the exhaust with a pressure guage. You'd need to weld in a small bung on the header pipe, perhaps just past the first bend and then connect a guage to it. Idle pressure should be around 1.5psi (or less), 2000 rpm should be about 3psi and 4000 rpm could be anywhere between 4psi and 8psi. If the pressure shoots up to an abnormal reading, there is excessive back-pressure in the system, especially if it continues to climb while holding a specific rpm. I think I found this info in an old Car Craft article. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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