Holstebro Denmark

 

is running without snorkel and MCM safe on EFI or should i get a power commander first?

 

MCM should not affect your current setup as it neither increases displacement nor RPM nor duration of intake stroke. Like the Nike ads say, "Just Do It".

 

Wow. This thread got way off track

 

Discussions on interesting subjects can lead off track numerous times in areas that may relate originally. Part of what makes a good discussion is trailing off a bit then cycling back.

 

The cam timings listed by the manufacture are at zero lift, and the stock cam profiles favor a slow ramps for durability of the valve train. To really understand the timings you need to see the timing at 1mm lift. When you check that out ( I did) you'll find this cam mod has the motor running with zero overlap, not conductive to performance. The cams just aren't ground with enough duration to make the change in lobe separation work. Any felt gain would be from the earlier intake closing time which results in more dynamic compression. At expense of killing its ability to breathe at high rpms. Maybe more of a concern with the carb'd bike than the rpm limited efi euro bikes. my 02, I couldn't put it back fast enough.

 

Concerning overlap: The exhaust valve stays open past the standard close point(retarded), and the intake opens/unseats earlier (advanced) with MCM. So at the top of the exhaust stroke/beginning of the intake stroke, overlap in increased. (This is the aspect of the MCM that gives a "power boost" on top..)

Whatever the stock overlap measures, the MCM increases it. How could it not? Whether your measuring @ .050 or not, you are opening the intake valve earlier and closing the exhaust valve later - increasing the amount of time both are unseated (overlap) around TDC on the intake stroke..

Visually, the MCM rotates/repositions the cams toward each other.. Now if, somehow, a MCM was done backward - repositioning/rotating the cams away from each other - you certainly would loose overlap with, no doubt, lousy performance.

 

thanks I may have mathematically calculated the OL wrong for the mod. I did however have them positioned correct. The 1st time I did the int cam only, 2nd time both. FWIW the stock .050" spec is. intake 2.5/37.5, exh 37/5, zero OL, duration 215/212 measured by webcam. The intake closing time is the most important timing event. Stock it is about where it should be. Modded it moves too far, closing to soon for good fill. That's exactly how it runs too, despite any increase in OL. The increase in dynamic compression from the early closing gives it some more felt power down low, but in my case takes away the strong pull at redline on top. This was more noticeable when I put it all back stock. Where I did think it helped was in slow trails, maybe using a gear higher roll on. just my 02, has been a few years since messing with it.

my bike is a 06 250, here's what it looked like new, rejetted with a kdx snorkle and 300 exh system. Sort of my baseline as I played with K&N filter, lid off, big gun pipe, cam phasing, offset timing key later.

 

You should know that, best I can tell from a few years of researching performance modded non-MCM KLX's, they seem able to make about the same peak HP, but 2 lb.ft. LESS torque.

Since the TRQ curves on non-MCM and MCM bikes is a nice bell shape, this +2 lb.ft. at peak creates a HUGE difference in performance.

Also, you should know that a measurement of TRQ @ 9500 RPM between your chart above and my latest run shows you almost to 11 lb.ft. and me at 13 lb.ft.

Since you are looking for power level increases around redline (10,500 rpm) and a TRQ ramp-up closer to redline, I can understand why you could prefer standard timings even though the dyno charts indicate otherwise. The "earlier" MCM midrange "hit" is so strong that it "masks" the fact that more power is also being carried to redline.

 

Thanks for posting your chart. I'm having a great time analyzing it.. It looks like a DJ128 does a pretty good job of fueling with a snorkel below 8200 rpm. That "lean-out" 8200 - 9200 hurts - probably a lotta MOPOWAH could be created there with an proper AFR.