That's what it boils down to, George.  After the open pulse terminates and the injector should close in less than a millisecond, a diode causes the injectors'  magnetic field to hold open the pintel up to several milliseconds longer than it should.  Therefore the mixture actually ends up richer than the EC2 intended. 

 

Now, what is not clear to me, is if you tune using an Air/Fuel Ratio indicator and then program that value into the EC2 via the program mode does that compensate for the longer open period by making the pulse shorter until you get the A/F mixture you want.  I suspect that it does at least to some extent. 

 

About the only place you would ever really notice it is at idle - because at higher rpms - the extra fuel just burns on through - but at idle more fuel can make a big difference as there is so little air to begin with in the manifold.

 

It sounds like the "hold" period is not constant therefore, one correction factor won't work for all the different injector pulsating duration.

 

But, Tracy will develop a fix for sure.

 

Ed

----- Original Message -----

From: George Lendich

To: Rotary motors in aircraft

Sent: Saturday, March 10, 2007 3:48 PM

Subject: [FlyRotary] Re: The truth??? / Injector flow rate mystery solved

Is Tracy saying that the injector stays open longer - putting in more fuel and making the inlet charge richer?

George ( down under)

Still refining the exact numbers but here is the basic cause.

 

The diode clamp on the injector drivers (in EC2) serves 3 purposes.  It limits the inductive flyback voltage to protect the driver transistor.  It recovers some of the energy used to open the injector thus reducing the current consumption of the system.  It eliminates arcing at the A/B injector switching relay that can cause noise problems with the processor chips.

 

Unknown to me until recently, it also significantly increases the closing time of the injector after the driver pulse ends.  I thought the delay would be negligible.  The actual delay depends on several factors but may be as much as 5 ms (!)  Ed will know what a big deal this is.  The factors that go into this and how much it is magnified by the diode clamp is still under investigation.

 

The good news is that there is a very simple fix.  (Note, Do NOT go out and remove the diode clamps! That isn't the fix!

 

Tracy

----- Original Message -----

From: Ed Anderson

To: Rotary motors in aircraft

Sent: Friday, March 09, 2007 7:13 AM

Subject: [FlyRotary] Re: The truth??? / Injector flow rate mystery solved

I certainly don't know, Rusty.  Like I said the only thing that Tracy and I could conclude was that Mazda was under-rating their  injectors - I wondered whether it might have something to do with the way an engine is taxed in Japan.

 

In any case, Tracy is clearly ignoring our pleas for more information - poor guy is undoubtedly working furiously getting orders completed before Sun & Fun.  But, he really shouldn't tease like that {:>)

 

Yes, I understand what you mean about measured flow rates - I suspect there is something subtle about this matter.  Perhaps the current profile used to open the injectors plays some role in this as Tracy indicated he was working on a Fix.  Perhaps a two stage or progressive flow rate profile - opens and provides normal flow for typical automobile usage but, when wide open (like ours are at cruise) perhaps the flow rate is more.  Who knows - Tracy Crook that's who.

 

Ed

----- Original Message -----

From: Russell Duffy

To: Rotary motors in aircraft

Sent: Friday, March 09, 2007 12:19 AM

Subject: [FlyRotary] Re: The truth??? / Injector flow rate mystery solved

Tracy and I have been discussing this injector flow rate anomaly for years -  

 

For some reason, I was certain that the Mazda injectors flowed more than they were rated for, but after sifting through some old logs, that's not true for all Mazda injectors.   I sent 4 slightly used 550's to RC Engineering, and they tested them at 547, 549, 551, and 551.  If that ain't 550, I don't know what is :-)  

 

I guess I'm baffled now.  Does Mazda operate them at 5 volts or something, rather than 12V?  That would slow down the response time.   

 

 

Hey the HKS is a good little engine in my opinion - not as good as a light weight rotary (which we don't have yet - Richard! get a move on {:>)), but it'll get you  flying again. 

 

Thanks for the comments.  It can't hurt much to try it, because I've already got people who want to buy it if it doesn't work out.  Still, it's as much trouble to install as the rotary, so it really comes down to a weight issue, and perhaps whether I'll ever get my redrive from Autoflight...  

 

Rusty