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Discussion Starter #1
Hello all. I have searched and read various threads on lobe centers preferred. I have a Gen 2 motor with a gen 3 crankshaft and gen 2 cams. I will, at some point, change the cams when I get set up a little better. I recently rebuilt the engine and am at the cam stage of this build. The application of this engine is in a 4 wheeler that will have more weight than a bike with rider.

I have engine simulator that I use to change variables to help set up exhaust, cam timing, CR, ETC. For what I need, the lobe centers need to make more torque to get off the line (this is a drag racing application). I my simulations the best suited lobe centers seem to be 100 intake and 108 exhaust. As simulators are not perfect, I wanted to get some opinions on this. Do not focus so much on tq/hp at any given RPM, but at the relationship between power output and the lobe center changes. This mock up is with a detailed exhaust at specific lengths not seen in production bikes. Also note the compression ratio changes based on cam timing. The increased torque from cam changes is at the cost of higher cranking compression/static and dynamic.
 

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What an awesome build! Did that quad start its life as a Raptor by chance?

You sir, have made one wicked machine!
 

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well done on the build a lot of work right there :notworthy: But for what i think on G2 lob centres at 100-108 ? if you can get the inlet to 100 with a minimum 0.8mm PTV then try it, engine simulators are a good tool for designing production engines but the more radical and variable the information its feed the less realistic variables itll blert out. For me i would bypass the G2 cams right from the off, see if you can get a G3 kit inlet and swap those steel inlet valves out for G3 ti valves, but then your probably thinking well maybe a G3 head is better.........yes it is much improved platform over the G2 although the exhaust valves are smaller its a head that produces better torque even before porting. But with the set up you have got i would need to be looking at a dyno chart after some base runs to start dialing cams. Others are gonna be along with more useful information shortly :wink2:
 

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Discussion Starter #5
well done on the build a lot of work right there :notworthy: But for what i think on G2 lob centres at 100-108 ? if you can get the inlet to 100 with a minimum 0.8mm PTV then try it, engine simulators are a good tool for designing production engines but the more radical and variable the information its feed the less realistic variables itll blert out. For me i would bypass the G2 cams right from the off, see if you can get a G3 kit inlet and swap those steel inlet valves out for G3 ti valves, but then your probably thinking well maybe a G3 head is better.........yes it is much improved platform over the G2 although the exhaust valves are smaller its a head that produces better torque even before porting. But with the set up you have got i would need to be looking at a dyno chart after some base runs to start dialing cams. Others are gonna be along with more useful information shortly :wink2:
Thank you. It's been a learning experience!

:eek:ccasion1
 

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Discussion Starter #6
OK.. checked the P to V at stock timing @ .018" head gasket
.042"@~10°ATDC @106.5 L.C. Damn that is close for stock!
Simulated clearance
.016" @ 100L.C.
.031" @ 104L.C.


The 2008 cam shaft should yield checked at 8°ATDC.
.070" @ 111L.C.
.043" @ 104L.C.
.027" @ 100L.C.

For this cam there is no point is lowering the lobe center line.
 

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Discussion Starter #8
how did you make that exhaust? custom cut/weld? or other?
I took the right side dual and moved to left and so forth. The header is a 2 step size and I cut the pipes where there is a step change. I cut another section 3 inches lower and raised the pipe and welded it. The other pipe I had to do the aforementioned and cut another section lower down and rotate slightly and weld. This changed the primary length from 22 to 19. This will move the power up, not really what I wanted. The last pic is it mocked up to what I thought I might do as I have not finished the exhaust.
 

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Discussion Starter #11
Made another change a few months back. Wanted to save some weight and get more ground clearance. I added a short muffler to the end so I can romp the neighborhood without upsetting those with sensitive ears! Works great. Just riveted it on, remove rivets for racing, reinstall later!

I really need some help on valve spring choices with the nitrous. I have been spraying 82HP on stock springs. I know, crazy.. But.. I am doing it with a progressive controller, window TPS, speed enabled, window cut out before shift, direct port with 2 maps... DRY shot. I hear APE duals break, don't know why (installation error or other?). The weak link is the aluminum retainers with heavy springs. Some don't like Carpenter, some hate KW, not sure about APE. Gathered spring info:

The KW 40-40500 come with steel retainers and are a single spring, the same for both intake and exhaust.
The KW 40-40250 have Ti retainers, so the pressure is less. Not a fan of this one as the stock Kawi is more with lighter spring retainers.
APE is the same, basically as the KW 40-40500 but with less seat pressure.

Any experience with springs and NOS?

stock kawi 262lbs/"
0.35
1.32 35
0.97 127
92 262.8571429
0.35 1


KW SPRINGS 40-40500 275lbs/"
0.425
1.32 65
0.895 182
117 275.2941176
0.425 1

KW SPRINGS 40-40450 intake DUAL Spring 251lbs/"
0.445
1.35 50
0.905 162
112 251.6853933
0.445 1



KW SPRINGS 40-40450 exhaust DUAL spring 244lbs/"
0.445
1.24 44
0.795 153
109 244.9438202
0.445 1

APE VS1000K 271lbs/"
0.35
1.32 45
0.97 140
95 271.4285714
0.35 1
 

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Just opinions here, but here you go:

Run the minimum amount of spring that you can. Excessively heavy springs eat up parts and don't net you any bonus performance. I've used the APE ti retainers and springs on my turbo build with no problems, but I also run the stainless steel exhaust valves... running extra spring on the thin titanium OE exhaust valves has been rumored to tulip them over time.

The OEM aluminum retainers in the second gens have been known to break, and I would personally change them to a ti retainer for peace of mind in a high performance build. Once you go to the ti retainers, you'll need a little more spring to move that mass. As mentioned, a little more spring and ti valves may not get along. I never ran a spring upgrade with nitrous, but I never ran more than a 40hp shot. Honestly, nothing about nitrous when it's working properly would require more spring... though nitrous induced backfires on either end of the cylinder head can have the nasty side effect of pushing the valve open at a bad time.... by slowly progressing the shot and staying off the limiter you would likely avoid that problem.
 
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