Gen 1 Main Pickup Coil Signals, Ignition, Timing Data from the VMax Guru

[hubeerjw]

I e-mailed Tim (the VMax Guru) a while back with a few questions on the gen 1 pickup signals. What I was hoping for was an easier way to get a 4 to 8 cylinder tach to work with the VMax. My idea was quickly shot down, but Tim did provide some nice data that I asked him if I could share with the group.

Tim recommended that I get a few diodes and basically make a t-boost setup for the tach. Since coils 1 and 3 fire 180 degrees from one another (as do cylinders/coils 2 and 4) I think we can make this work.

I called Autometer and talked to one of their techs and he said their tachs use a 0-12 volt square wave signal with a 50% duty cycle. The guy I talked to actually knew about the Vmax and the problems with adapting their tachs.... I was very surprised! He seemed very interested in hearing if we can get this to work. I'm not exactly sure what Lankee uses or how he gets the tachs to work, but if you can still read this Lankee... maybe you should contact Autometer and let them know what you are doing... maybe you can get some free gauges out of them?unk:

Thanks again Tim!

 

[vmaxguru]

Your welcome. Here is a better version that I just finished.

Tim Nash
VMaxGuru.com

 

[pegscraper]

What does "pause before neg" mean?

 

[TURBOVMAX]

That is THE BEST INFORMATION! I've ever seen explaining the VMAX engine ignition and combustion cycle. The oscope info I've wanted to see forever. Don't know about anybody else, but getting that timing thing straight in my head without this info is nearly impossible.:ummm:

Jeff..Thanks for the thread! and Tim You are the man!

 

[Birdoprey]

Yep, WONDERFULL information. Those charts are what helped me to finally understand the firing sequence as well as put me on the right path to grasping which pickup does what!

Hey Tim, your first version of the crank events was MOST helpful to me. Looks like you may have replaced it with the one above?

 

[Birdoprey]

What does "pause before neg" mean?

With a VR type pickup, it produces a positive pulse then an negative pulse(normally immediatly after). You can look at the pickup pulses at the bottom of the chart he posted and see that all events have a positive then immediatly go negative, EXCEPT for the event for cyl #1 where there is a pause as the crank turns some before it goes negative.
I just dunno WHY it would do this.

 

[Rusty McNeil]

Using diodes to make the autometer tach work does just fine......

I ran an autometer for a while and that is exactly how I did it.

I think i ran across the wiring diagram originall on vmax outlaw or the lvlhead site.....

The circuit is just about identical to the t-boost setup that simply switches it from 6000rpm to 3000rpm.....but instead of fooling the Vboost controller your fooling the autometer......you can buy the parts at radio shack......

 

[pegscraper]

With a VR type pickup, it produces a positive pulse then an negative pulse(normally immediatly after). You can look at the pickup pulses at the bottom of the chart he posted and see that all events have a positive then immediatly go negative, EXCEPT for the event for cyl #1 where there is a pause as the crank turns some before it goes negative.
I just dunno WHY it would do this.

Ah, I see. Thanks. As to why, I think I can answer that one. The longer trigger point for #1 orients the ignition module to the crank position. If the #1 trigger was the same 5* length as all the rest of them, the trigger pattern around the rotor would be symmetrical. The ignition module wouldn't know if piston #1 was at TDC or at BDC. It wouldn't know if it should be firing #1 or #3. Cylinder #1 will fire every time the piston comes to TDC. There's always a wasted spark. But if it tried to fire #1 180* off, at BDC instead of TDC, the engine wouldn't run at all.

 

[Birdoprey]

Ah, I see. Thanks. As to why, I think I can answer that one. The longer trigger point for #1 orients the ignition module to the crank position. If the #1 trigger was the same 5* length as all the rest of them, the trigger pattern around the rotor would be symmetrical. The ignition module wouldn't know if piston #1 was at TDC or at BDC. It wouldn't know if it should be firing #1 or #3. Cylinder #1 will fire every time the piston comes to TDC. There's always a wasted spark. But if it tried to fire #1 180* off, at BDC instead of TDC, the engine wouldn't run at all.

Yeah, i was'nt thinking about the single pickup of the 93-up V-max's. It would need a reference for cyl #1

 

[pegscraper]

What I'm curious about is why there are two dummy trigger points, one between #2 and #3, and one between #4 and #1. It seems to me that all it should need are the four that fire the cylinders, and some way to orient the ignition module to the rotor (which it has in trigger #1). So why the extras? Any ideas anyone? Guru?

I'm going to throw this drawing up here for the sake of it. Some of the info is the same, but mine locates a few other things on here, like T1 and T2, the keyway, and the length of the trigger points. It's not a fancy computer generated thing, just a pencil drawing I did last summer when I was working on a project. It might be a little light, but hopefully it's readable.

For a VMX, ignore the trigger point marked X and imagine a solid line for #1.

I actually drew this up for my Royal Star to compare the trigger points on my bike to those on a VMX. Many of you probably know that the Royal Star has basically the same engine with a few differences. The Royal Star rotor has a trigger point at X and has just a standard length trigger at #1, with all else being the same. Y already had a rotor trigger pattern and ignition setup that worked. Why they had to design a different one for another bike with the same basic engine, I don't know. I drew this up because last summer I was trying to adapt a VMX ignition module to my bike because it has a much better spark advance curve and a higher rev limit available than my stock one does. So far I haven't had any luck getting it running. But I digress...