Im an idiot

[400exrules]

This is a dumb question, but what is a CDI, just an aftermarket starter? What are its benefits?

And should i get a revbox? i do some drag racing on 300ft dirt, and i usualy dump the clutch on the revlimiter in 1st, and someone said i would do better with a revbox:confused:

thankx

[Rip_Tear]

Okay, the Rev box, changes the max RPM that your motor allows (basicly). I'm not sure exactly what/how to explain a CDI... It's not a starter, it is part of how the engine electrical is controlled.

[PunkA$$]

The CDI (capacitor discharge ignition) replaced the points and condensor system for controlling ignition timing.

The advantage being fewer moving parts to wear out and fail.

An aftermarket CDI could allow you a different ignition timing curve and allow you to bypass the engines governor.

Not sure if that helps you or not.

[400exrules]

Do either give any kind of performance, or reliability gain for drag racing? I was just wondering if i would need a revbox since im on the revlimiter for like a 1 or 2 seconds at the start line.......OR if it would help my starts off the line.

[PunkA$$]

Originally posted by 400exrules
Do either give any kind of performance, or reliability gain for drag racing? I was just wondering if i would need a revbox since im on the revlimiter for like a 1 or 2 seconds at the start line.......OR if it would help my starts off the line.

I'm not sure as I've never used one myself. You'd have to be careful riding it like that without a rev limiter though.

[400exrules]

Originally posted by Punk*****
I'm not sure as I've never used one myself. You'd have to be careful riding it like that without a rev limiter though.

im confused now....i thought stock, they have rev limiter that kicks in at like 9,000rpm preventing you from over revving and doing damage, and when you get a rev box it lets it rev higher. Wouldnt a rev box be more dangerous since its revving higher?

IDK, a guy at the races told me i should get a revbox then i can just hit the rev limiter and dump the clutch....i thought you could do that without one..?:confused:

im rarely on the rev limiter for over 1 second....just when im on the line, im in 1st gear, and when were both fully staged and the top light comes on, i just give it full throttle for a sec then dump it when it gets to the third yellow light

[underpowered]

a CDI and a revbox are one in the same. the CDI has teh revlimiter in in, as well as the ignition curve. and aftermarket CDI A.K.A revbox raises the revlimiter and can alter the timing curve.

[bradrenea]

As stated above, CDI and "revbox" is the same thing. And an aftermarket one should not hurt your quad. That's the way I take off, only I take off in second gear instead of first. It's faster that way.

[phildogg]

I have a question. how do oyu take off so hard without the front end standing staight up?
phil

[400exrules]

Originally posted by bradrenea
As stated above, CDI and "revbox" is the same thing. And an aftermarket one should not hurt your quad. That's the way I take off, only I take off in second gear instead of first. It's faster that way.

I know alot of people who shatter several clutch baskets every season due to starting in 2nd. I start in 1st cuz its safer for your clutch plus its a hell of a lot faster, for me atleast....i get off the line like a rocket

[underpowered]

Originally posted by phildogg
I have a question. how do oyu take off so hard without the front end standing staight up?
phil

it is an aquired skill. when i first got my 400, a while ago i could not take off quickly without wheelying, now i can take off in first or second with the front end only coming up 8-10 inches and carry it to the first corner. Just put your weight as far forward as possible and slip the clutch alittle, dont just dump it.

[400exrules]

Originally posted by phildogg
I have a question. how do oyu take off so hard without the front end standing staight up?
phil

i have a wheelie bar:devil:

ill try to get some pics with the wheelie bar on soon and get them on here, its badazz. I just lean as far back on the seat as i can so i can get all my weight on the rear tires, give it full throttle and dump the clutch in 1st gear, and im off like a bat outta hell!!!:devil: And i run pro wedge 2's at the drag races, with like 3-4 pounds in them, so they hook up awesome

[bradrenea]

Originally posted by phildogg
I have a question. how do oyu take off so hard without the front end standing staight up?
phil

I dump the clutch on mine. The key is to commit yourself to it. If you rev it and dump the clutch it will spin for a couple feet and then your gone. Most people can't get over the fear of flipping over so they either hesitate or don't give it full throttle and guess what happens, it flips over. Just hammer it and dump the clutch.

That is the technique I used at the dirt drags last year with american racers. They hooked like crazy, but it would spin just enough to keep the front end down and still launch. I have a picture of me all the way in front of the tree with the green light still on. You will never leave that hard slipping the clutch.

[wilkin250r]

Ok, I'll give you the end-all definitive answer. Here is everything you need to know about ATV ignition for your level of knowlege. Listen up, because everyone will tell you, info like this from me is dead-on accurate.

Ignition starts with your stator and flywheel. In simple terms, your stator is just a bunch of coils of wire, and your flywheel is just a bunch of magnets. So your flywheel is spinning these magnets around these coils of wire, and that produces electricity. The amount of electricity changes depending on how fast the magnets are spinning, which is determined by engine RPM.

With me so far? It's fairly simple.

Now, the stator has dedicated coils. Electricity from most of the coils goes to the lights. However, the stator has a couple dedicated coils that generate electricity for your ignition spark. Let's forget about the lights, they're not important.

So, this electricity for ignition gets fed to your CDI. It stands for Capacitor Discharge Ignition. A capacitor holds electricty (almost like a battery), but it is able to dump all that electricity very quickly.

So, in a nutshell, the stator and flywheel charge up this capacitor to several hundred volts. THe next stage is in the next post.

[wilkin250r]

Ok, so right now, the capacitor in your CDI is charged up to a few hundred volts.

On the outside of the flywheel is a little bump. The location is very specific, and your flywheel is attached to your crankshaft with a key, so it's also in a specific spot. So every time your crankshaft goes around, this little bump also goes around. There is a small sensing coil next to the flywheel, and it senses each time this bump goes around. The piston is in the exact same place each time this bump passes the sensing coil.

This is the timing trigger, and this information is also sent to the CDI. So by counting each time this bump goes around, the CDI calculates the RPM of the engine, and it knows where the piston is at.

This way, your CDI knows when to fire the spark plug. Too early, and you blow your engine. Too late, and you lose power.

This is a lengthy explanation, but it gives you all the info you need to know right now. Next post.

[wilkin250r]

So, our capacitor inside our CDI is at several hundred volts, and the timing trigger pulse just came through.

At the right time, the CDI dump all the electricity in the capacitor to the ignition coil.

Without getting into detail about how transformers work, the ignition coil bumps the voltage from several hundred volts all the way up to several THOUSAND volts.

These several thousand volts are fed directly through the spark plug wire to the spark plug itself, and creates the spark that ignites the fuel inside your cylinder.

That is your entire ignition system. Stator, flywheel, pulse trigger (also part of the stator), CDI, ignition coil, and spark plug.

[wilkin250r]

So, your CDI calculates engine RPM by counting the trigger pulses coming from the flywheel. If RPM gets too high, the CDI cuts the spark, no more power until RPMs drop a little. This is your rev limit.

This is beneficial because if your engine can damage itself if it revs too high. On a STOCK machine, your engine doesn't make much power at those high RPMs anyways, so it's no loss. However, with a modified engine, you still might have usable power at high revs, so an aftermarket CDI with a higher rev limit might be beneficial.

[PunkA$$]

Very informative, well put!

[400exrules]

wow.........thanks man, how do you know so much lol.
Your like that commercial with the easy button, you make it all make sense:D

i didnt know a rev box and cdi were so closely related, but now i do:cool: , thanks

[Warrioreater400ex]

wilkins..... so since we are on the subject of timing... explain how the sparks 6 degree timing key works... i mean i know it physically advances the flywheel... how does advancing or retarding the timing increase power/performance?

[PunkA$$]

Originally posted by Warrioreater400ex
wilkins..... so since we are on the subject of timing... explain how the sparks 6 degree timing key works... i mean i know it physically advances the flywheel... how does advancing or retarding the timing increase power/performance?

I read every thread about this before I bought my timing advance key. Here's what you're looking for \/ (by wilkin250r)

The timing of the spark is an important part of the power characteristics of your engine. Think about HOW it happens. I'm sure you know the theory, the piston is moving upwards compressing the fuel/air mixture, the spark fires, the fuel explodes, and it pushes the piston downwards.

Now, think about slowly, in full detail. Nothing happens instananeously. Imagine that the spark occurs right at Top Dead Center. The spark fires, and the fuel around the spark plug begins to ignite. Meanwhile, the piston has already started to travel downwards. Because the fuel has not fully ignited, and the piston is traveling downwards, the pressure is actually DROPPING inside the cylinder, instead of increasing like it should. The higher the pressure, the better the fuel/air burns, but your cylinder pressure is actually dropping. So the flame front moves outwards away from the spark plug, igniting more fuel/air as it goes, but it's moving slowly because the pressure is dropping and the fuel/air doesn't ignite as easily. Eventually, enough fuel/air will ignite that cylinder pressures increase and push the piston downwards, but you don't get a really efficient burn and not much power out of it.

Now, imagine that you install the advance timing key, so the spark fires 6 degrees BEFORE top dead center. The flame front travels outwards much faster because your cylinder pressures aren't dropping. The piston can still travel upwards because you haven't ignited all that much fuel yet, so cylinder pressures aren't too high. But the important thing is that your flame is traveling much faster. The piston reaches top dead center and starts moving downwards, but cylinder pressures don't drop. Why? Because you are already igniting fuel, you already have a high flame speed, to the cylinder pressures continue to rise and already begin to push on the piston, creating output power right away, instead of 10 degrees after TDC. You get a clean, efficient burn, and much more power output.

This is the basic theory. In reality, the spark doesn't actually occur at top dead center, but you get the idea and how it works.

The spark timing is controlled by a little trigger on the outside of the flywheel. By physically advancing the flywheel with the Sparks Key, you advance the timing.

Now, because the fuel is igniting quicker, and more efficiently, it will also create more heat. If you are running high compression to begin with, you could have detonation issues.

[Trevor]

lots of good info here you guys realy seem to know your $hit.

[Warrioreater400ex]

Thanks! i used the search button but never found wilkins info on it...

[wilkin250r]

I remember that post. That was a while ago...