A question about CDIs.

[joshstep1]

I'm a little confused about no rev CDIs. Now I believe that the CDI that comes with these buggies limits the engine to 5500 RPMs. I think Mike (from ****) told me that my engine with a no rev CDI would top out at something like 9500 RPMs. If I'm pushing almost twice the RPMs out of the engine, then shouldn't I go twice as fast? Buggymaster told me that I would only gain about 2 MPH on the top end. I'm confused.

[24evanwilson]

uuuuuuuuuuuuummmmmmmmmmm??

idk

[joshstep1]

Hence the reason I was kinda asking someone else lol

[BuggyMaster]

You are not limited to 5500 RPM. I've never bounced a rev limiter in any ASW machines. Some people have said they believe there is a rev limiter but I don't know it for a fact. 2mph is all I have ever gained from a CDI unit. It did not rev twice as high as prior to CDI. Just a little bit but that is probably a matter of a slightly different timing curve or something like that built in that gives it just a little more umph.

So, if you were to rev twice as high you would in fact go much faster but you are not going to rev that much higher.

[ckau]

never heard of a cdi with a 5500 rev limit. Those cdi's that do have a limit fall somewhere in the 7800 t0 8500 limit. your speed is not dependant on rpms as such.Your power comes from operating the buggy in the optimum power band. Speed comes from the C.V transmission and GEARING mostly. A bone stock gy6 reaches maximum power around 6500 to 7500 then the power to rpm ratio fails off. A properly modded and tuned gy6 can turn 10000+.
I use 3 different axle gears- 26 tooth gives me 45 mph average. but is a dog off the line [low torque ] good for pavement or a 1/4 mile round track
A 31 tooth gets average 35 mph [ most stocks fall somewhere around this count] good for general riding around.
A 39 tooth, good for hill climbing, hard pulls [a good rough trail gear]with a 25+top speed.
It's all in the gearing! this is just a general idea of what mine does but my motors are highly moddified. I have only scratched the surface! There are also different internal rear trans gears that can be switched out along with variator and clutch setups that can done to customize your riding style.

[joshstep1]

Thanks for the info guys. But I'm definitely not going to regear it. It's a lot of buggy you have to take apart to do that.

[roysheepdog]

Originally Posted by joshstep1

I'm a little confused about no rev CDIs. Now I believe that the CDI that comes with these buggies limits the engine to 5500 RPMs. I think Mike (from ****) told me that my engine with a no rev CDI would top out at something like 9500 RPMs. If I'm pushing almost twice the RPMs out of the engine, then shouldn't I go twice as fast? Buggymaster told me that I would only gain about 2 MPH on the top end. I'm confused.

i did not get any rpm gains from my cdi4650@36mph,stock was the same.it did make more power but not rpms.rpms come from moving more air the more air you move from one end to the other the more rpms you will get.if you got a bigger header and mufler you will get more rpms.then you will need to rejet again and even more rpms and on and on.air=rpms
blow through a small straw and blow through a big straw and you can see how much more air will go through.

[ckau]

The only thing a advertised "Performance" cdi does is give more advance in the timing curve. Factory stock motors come de-tuned in order to be reliable, dependable and lessen the chance of break downs. Depending on the stock setup, a little timing advance can help alot. There has been some serious testing done to determine if the rumor that there is a rev limit incorporated in some CDI's is true. Non tested were found to have this.

[joshstep1]

Whats the timing curve?

[ckau]

Originally Posted by joshstep1

Whats the timing curve?

it would take the whole space in this reply to try and explain it to you Josh. the best thing to do is go online and research "4 stroke , single cylinder" you will get alot better info than I could give to you. There is tons of info out there and some particular to the gy6.
In a nutshell: as the piston comes up on the compression stroke the plug fires at a certain time to ignite the compressed air/fuel mixture. As the rpms increase the plug has to fire sooner to anticipate the speed and position of the piston. The cdi is just a little computer program in a box. It is programed as to when to send the signal to the plug to fire.The cdi gets it's info from a magnetic pickup on the flywheel. The pickup tells the cdi what the rpms are. As rpms increase the cdi send the single sooner [advance]. This is the timing. If you show the timing points on a graph with rpms along the bottom and piston position up the side, It looks like a gentle curve.[The timing curve] Some cdi's are programed to only speed up the firing cycle only so fast and it stops. Average around 8,000rpms. This is where that idea of a rev limit comes from. The motor designers figure no one would drive that fast! HA!! Jokes on them huh! The "performance"cdi has more program in it to allow even faster timing [more advance]

[BPNWMike]

Some really good info in this thread.

Some buggies do have CDIs that top out at 7500 or so RPMs, as ckau said. My Reaction 150 certainly had one. The performance CDIs don't restrict you at that level and also have the different timing curve, as the other guys have said.

[joshstep1]

Thanks a lot for the info guys

[dbil84]

i've seen online different stages for cdi's stage 1,2,3 whats the difference between these?

[BPNWMike]

Often, it's just the dealer's own marketing. There may be no significant difference in overall performance between the products. You should contact the dealer directly for an explanation of what makes them all different and see if they even have an answer!

I've got a Level 1, 2, 3, etc package, but that's really just a numbering differentiation more than anything. The level 1 and 2 CDIs are operationally similar, with a heat sink cooling fin assembly on the Level 2 CDI. Level 4 is an adjustable CDI, so that's clearly a different product. (Level 3 is the Level 2 CDI with a coil added to the package.)

Basically, as the guys have said earlier in the thread, the CDIs will be functionally similar with different timing curves in the higher RPMs, and no artificial RPM ceiling.

[ckau]

Originally Posted by ****Mike

Often, it's just the dealer's own market

True that! this is the business side of this sport that really puts my shorts in a bunch! I have seen alot of stuff come and go over time. Most of which is hyped up by a manufactor who can't or won't offer data and info to back up their claims. You can ask the venders questions but they can only give you an educated guess to the best of their abilities. It's not the venders fault, they are left in the dark as much as we are.
It's frustrating, it is the venders that has to put their neck out, not the manufactor.
A perfect example of this: I asked for some pertanant specs for a water cooled head in this forum. This is a costly item. I need to know EXACTLY what it will achieve before I hand over the cash. Is this too much to ask? The seller either did not read my questions correctly or he didn't have answers. I have asked one of the worlds largest supplyers of performance parts, to his face! about some data to back up his claims on a particular product. he looked like a deer caught in the headlights. Either way, both lost a sell. If you are considering a purchase. NEVER pay attention to the advertising hype. Ask someone who has used the stuff before such as mike or the other venders on the forum. These guys try just about everything that comes through the door. they have the skills, knowledge and experience to give you an honest ,straight up answer.What I like respect most about these guys, they are not afraid to say " I don't know

[BPNWMike]

95% of the products I sell I have tested myself, and the rest have been tested by someone I trust - or they don't even make it onto the site.

One example is that I've been sitting on this new 250cc CDI/Coil combo for about 2 weeks now and not putting it on the site because I couldn't test it myself and no one I knew had tested them.

I knew they worked and are better than the adjustable CDI + a coil that they replaced in my product lineup from the manufacturer's info, but that still doesn't mean I can honestly tell a customer that I personally know for a fact they are better.

It wasn't until I was able to farm one out to a regular customer who was happy with it that I put them on the site (just last night!) I've got a waiting list of 5 people who waited for months that wanted an adjustable 250cc CDI - I still wouldn't list it until I knew more about it.

I never want to be in the position of "Oops, I should have tested that more" and having an unhappy customer.

[bige]

I do the same as Mike. its alot more work but in the end the customers knows what they are getting and we have information that is correct.

A good example is the cable operated choke I have. I tried it on my wifes buggy and sent two out to customers for their review before I even thought about adding it to my product line

[SYCARMS]

Stock CDI's do have rev limits in them. However on a stock engine the only way to hit it is under no load conditions. Stock CDI's are also retarded to meet EPA. My 2004 Blade timming with stock CDI was 10deg. ATDC and some manufacturers run more retard on the 2007 and up. The new buggies that come with an EGR or Converter will sometimes run 2deg.-3deg. BTDC, this is why some buggies are quick out of the crate and some are dogs. When I rebuilt my sons engine I ran it on a stand with a stock CDI and could only pull 8300 RPM, but when I installed the performance CDI it went to 10,000RPM and would have gone higher. A heavy moded engine stroked, with larger displacement cam and head work will acheive up to 12,000 RPM, however a stock or slightly modified will not due to the lack of total output. TOM

[rich1]

Originally Posted by ****Mike

Some really good info in this thread.

Some buggies do have CDIs that top out at 7500 or so RPMs, as ckau said. My Reaction 150 certainly had one. The performance CDIs don't restrict you at that level and also have the different timing curve, as the other guys have said.

Mine topped out at 7,500 stock. I replaced it with a no limit CDI and got 8,500 rpm .CDIs max was listed as 9,000 from Standard Racing Parts. The gearing limited it from reving any further. I am working on getting the motor tuned better and then will re- gear it to run in the higher power band. The RPM was verified by a Digital Mac timing light hooked to the CDI. So they do work but need tuning and gearing changes for max performace.

[Johnny 5]

I put a orange performance cdi on our 2004 baja dune 150. With the stock cdi I have run our dune 150 down a wash and at top speed I could hear a ratling/popping noise. I would say the valves were floating? With the orange cdi no rev and advance same top speed . The idle had to be turned down a quarter turn with the orange cdi. The take off performance was better but climbing with my son was not as good with the stock cdi. I weigh 200lbs and my son weighs 175lbs. Our engine is stock 150 gy6 valves set to .003
intake and .005 exhaust jetting 115 main 34 pilot. I guess that if you modify your engine you arer best to go all the way. Best money spent so far is 10 gram sliders and 1500 torqe spring as far as low cst upgrades. I do recomend 91 unleaded for advance cdi.