Prairie633;

Did you see the chart for the stock CDI on dyna site,

does it match what your finding?

 

Prairie333,
I'm guessing you are correct about the existing modules (based on speed sensor input) not affecting the new dyna cdi as it probably has only 1 standard timing map ( with no retarded timing map based on speed of vehicle or reverse). However, the new cdi's advanced timing chart seems to indicate it starts off with the same or similar retarded timing as the stock cdi and gradually increases along with rpms until reaches 33 degrees before remaining there until reaching rev limit.

However, I am now guessing that it MIGHT BE POSSIBLE to create a new module for the new cdi that fools it into thinking it is operating at a higher rpm range so that it immediately starts off at 33 degrees and stays there until you reach rev limit. What do you think about my idea? Is this possible and would it add the same kind of performance gains to the new cdi as the existing modules make for the stock cdi???

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

With the modifications that a lot of us already have do we really need the extra advance on the bottom (on top of what the new CDI is projecting)? As it is I can't go full throttle off the line for at least ten feet without loosing to much traction.

On the top end, those of us with cams are going to fly!

 

MIKEY... Thats what I was thinking, hence my thoughts of using one of the existing modules... I don't doubt PRAIRIE633, that the existing modules won't work... ???? more to think about now... does anyone know why the new CDI doesn't start out strong ( similar to the module equiped stock CDI ???

 

Newbeatle,
I'm guessing that Dyna made the timing start off with weak timing for the same reason that Kaw/Mitsubishi made the stock cdi start off with weak timing...that is to avoid lawsuits from inexperienced folks who hurt themselves from pulling a big wheelie. Its just a guess mind you and I could be wrong here.

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

My understanding is that the new CDI does not use the speed sensor. It is also correct that it only has the single map.

I was thinking about the base timing on my ride to work this morning. The idle is supposed to be around 1,100 RPM, but I run about 1,400 RPM because my belt is tight - no shims. So I'm over 10* almost immediately after I get on the throttle. My thought is that the ride-ability would suffer if the ramp up wasn't there - specifically, it would be more difficult to keep the front end down and to deal with low speed obstacles. That’s not to say that a steeper ramp up wouldn’t be an improvement, but I think it comes to a point of balancing raw performance with control. Just a thought.

Just a clarification – the link I posted and the curve are NOT the Dyna site. They are on my personal web page. It may be on the Dyna site as well but I haven’t checked.

Peace,
Sgt_Rock

 

I'm guessing it's the law suit issue as Mikey says.

simples and least expensive way to over come the time lull on the bottom is to go with the red spring and heavier weights, which engages at 1700-1800 rpm. when it engages you'll already be into the timing advance.

I've used the red for years, yes it is an harst engagement, but workable.

 

I think that 5 degrees makes it easier to start if you have a big bore with high comp, or if you try to pull start it. Not that the reason isn't what you guys said too. I just think 5 degrees helps out with ease of starting.

 

I am really glad to see so many of you are more interested in this stuff beyond the normal "where can I get it". Between all of us here, maybe we can figure a few things out. Most companies I call for product information never let me talk to anyone technical, except DG. Usually I can only talk to the sales reps so you really have to do your own work to get at the facts.

Shotgun, yes it is really close, the only difference being that the top end 20 deg. limit happens at 8000 RPM. The only exception being the V-Force igniter part# 21119-1629. It measured at 28 degs. from 4000 RPM to it's rev limiter set at 8650 RPM.

MikeyBoyesq, from what I was told, the RPM is calculated from the same pulses that are the base reference for the spark timing. If you alter them around, the processor would also loss its proper reference. I don't think you would want 33 degs at low RPM anyway. I am not a Mechanical Engineer so don't hold me to this, but I think the reason for the linear ramp up is so that the combustion flame front, which burns at a relatively narrow range of speeds, applies the force on the piston at the proper time, for a large range of piston speeds. Too soon on combustion would tend to try to slow the rising piston down, and too late will not apply as much force as it could, and will have to disipate the remaining energy as excess heat. Just my guess? Even a stock Prairie with a module runs the curve shown as stock on the graph posted by SgtRock. The modules add power because they keep the stock igniter off of the retarded/reverce map which tops out at only 10 degs. I verified this when I mapped the igniters with the modules attached. A Prairie with a module vs. the new cdi should run nearly equal up to the 28 deg. stock igniter RPM, and then the added benefit of the new cdi will probably improve with the degree of mods you have. They will both pull off the line hard. I have tested this with a V-Force Igniter on a 2002 Prairie 650. I plan on finding out for sure once I have one and do so accelerometer runs for comparison.

SgtRock, did you say you have a Tazzo accelerometer? If so,could you set it for some 10-60 MPH timed runs for a (stock) vs. (stock with module) vs. (new cdi). I use 10 MPH as a starting point so that I can eliminate any differences in launch technique and traction errors, and I run from the same starting point in case there are variations in grade along the course. I also do some 10-30MPH and 30-60MPH to focus on gains in the different RPM ranges. Once the real tests are done, it is always fun to do the 0 to whatever tests just for fun. The Tazzo uses a two-axis accelerometer and has very good software for accuracy. I prefer "real world" repeatable tests like these even over dyno runs, but both would be even better.

 

As soon as we get a break in the weather, I'll definately do some Tazzo runs to compare both the stock and the new cdi. I pulled my Holeshot out and I'm not inclined to pull the wire harness apart again to put it back in. I'm going to put the FST 765 in over the next few weeks and the weather should break by then.

Someone asked what booth Dyna is at in Indy - it's supposed to be 3446.