Ignition curves

eric82930 · May 4, 2018

I just got done building a KX450 snowbike with reverse using the ATV bottom end. I couldn't run the stock kx cdi because the atv had a dc style 3 phase stator so I put on a programmable one and had to build the curve myself. Right now It likes max advance around 53 degrees! I can only guess because it still has the atv 12:1 piston and I'm running at high altitude. I'm going to rebuild it with high comp piston over the summer and see if I can get a faster more efficient burn so I don't need so much timing.

I know most of the tuners only give + and - degrees and you can't see the real curve or total advance. Does anyone have any actual curves? It would be interesting to see what works on snow bikes under hard loads compared to a dirt application.

eric82930 · May 4, 2018

The first one is where I'm at now. Idles at 15-20 deg. Peak adv 53 at 5700rpm to redline. Its just a little hot in the 3-4 k range I can hear slight knock If I bog it under a big load but never got it to knock at higher rpm yet.

The second is the only other curve i could find on the internet for a wr450

Sadly I don't have a real dyno, so I have to rely on my but dyno. Luckily I can ride 3 days a week which does improve its accuracy.

n16ht5 · May 5, 2018

I would give raze a call and talk to their engineer they are very knowledgable

M5- · May 5, 2018

You have a couple of options here. To really find out what's going on you could mount a wide band O2 sensor in the pipe. If you had access to a dyno you could then data capture and adjust the fuel curve. That part is going to be static based on fuel octane, volume and compression.

I'm assuming you are going to be running pump premium which as we know can be a crap shoot. I'd run as much fuel as I needed to get to about 12.5:1 or 13:1 give or take on the wide band. Once that is dialed throw timing at it until it knocks then pull it back. I don't know of any great way to detect knock on a bike, maybe its out there. I don't think I would concern myself with what the timing number is so much as I would preventing detonation and not getting too lean. 4 strokes can digest more excess fuel than a 2 stroke.

Back when I built my RX1 turbo I had a knock box which I'm not sure really did anything but it did go off once and a while when I got crap fuel or hit the rev limiter which fooled it.

Cool stuff.

M5

boondocker97 · May 6, 2018

I'd give DASA Racing a call and discuss with them. They were going engines for the factory Kawi quad racing program in the mid 2000s. They should have some idea of what you can safely run. https://www.dasaracing.com/Articles.asp?ID=83

eric82930 · May 8, 2018

Mine is running pretty good now. The snow is crotch deep mush right now and loads the heck out of it so I squeezed every last bit of safe hp available. I will wait until the compression goes up before I do anymore fine tuning.. I was more curious as to the range between tunes on fluffy gutless trail bikes like the wr and crx and all the quads that lost 10 hp some where during production. The mx bikes always have the most hp in every given displacement but no one really knows what base timing is even if they have a tuner box they can only say it is +3 more than stock etc...

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Ignition curves

eric82930

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eric82930

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n16ht5

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M5-

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boondocker97

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eric82930

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