DaleClark

iTrader: (55)

Haltech just posted up a new video with rotary tuning tips -

10 Things You Need To Know About Rotary Tuning | Haltech - Engine Management Systems

That link is the video and the content typed out. The one that interested me is tip #9 -

9. Most rotary engines should be happy with an injection angle of 270 degrees under cruising conditions and 330 degrees at the rev limit.

Does the PowerFC have a similar feature?

Dale

TRRAPLN

Not a Power FC guy. I have a Haltech PS1000.

Engine runs well and makes plenty of power. Always looking for tuning tips.

My Inj Firing Angle is 132 - 141 @ 3 - 3.5k RPM. Quite a way off from the 270 suggested and 202 degrees @ 7k RPM. S/b 330 degrees!
Also my Inj Angle Split is 0 degrees across the RPM range. Can that be right?

Engine was tuned by our local "rotary" guy but I question these setting especially in light of the Haltech tech article.

Can anyone shed some light on these parameters?

Is there more power/efficiency in making these changes?

arghx

iTrader: (3)

If the Power FC can adjust injection timing, nobody has identified how.

The other thing to keep in mind is that you need to know exactly how injection timing is calculated. You need to know

1) What is the reference point? If it's TDC, is that TDC compression (like spark timing) or TDC gas exchange (like on port timing/valve timing). With injection staging it could be something else.

2) Does the firing angle refer to the end of injection timing or the start of injection timing? Injection timing either counts backwards (end of injection timing) or forwards (start of injection timing). It depends how the ECU calculates it.

I can't find definitive answers for Haltech in regards to either question. I suspect it is start of injection timing, referenced to TDC compression (similar to spark timing).



If it's start of injection, you locate the crank angle degrees (assuming it's BTDC firing like spark timing) listed. Then you move to the right in the chart based on how long the injection pulsewidth is (pulsewidth must be converted to eshaft degrees). If it's end of injection, you move to the left. The stock 3rd gen ECU is a little different, but it's old. Rx-8 ECU is more modern.

Typically on a port injected engine the biggest thing that injection timing affects is smoothness of combustion at part throttle and idle. That's going to vary with the porting more than anything. When you get to full load injection timing doesn't even matter much, because the duty cycle is so high. If you are at 90% duty cycle, your injection duration is 720 * 0.9, which is 648 degrees. It doesn't really matter when you start or end the firing of the injector at that point, because the injector is hardly ever off.

Direct injection is a whole different animal.

arghx

iTrader: (3)

if injection timing is 132 degrees BTDC firing, start of injection, it means that you spray fuel after the port closes. The mixture vaporizes in the port and is drawn in during the next cycle, assuming it's lower load and you're at low duty. On a piston engine this is called closed valve injection.

if injection timing is 270 BTDC firing, start of injection, you are spraying into an open intake port. On a piston engine this is called open valve injection.

gxl90rx7

iTrader: (1)

dumb question.. i dont understand why that pic shows two TDC events per intake opening? the injector for rotor #1 only fires once per spark, which would be once per e-shaft rotation, right? why is it over a 720 degree window and not 360 degrees?

edit: nm i think i understand.. the spark is happening every 360 degrees, but that diagram shows how many degrees before TDC that the intake was open, which could be more than 360

i have haltech ps1k, which appears to set end of injection time in degrees before TDC. A setting of around 95 degrees seems to result in most rich idle, with 2200cc primaries (only 1 ms injection time), but it did have a pretty large window of variance where it didnt seem to affect anything. I have it ramped up to 180 degrees at redline. looking at that diagram, that seems too late..

i had based it off this diagram:

gxl90rx7

iTrader: (1)

so this is for the FD:



if i read that correctly, then the primary port opens 45+360 = 405 degrees before that combustion TDC, and closes 180-50 = 130 degrees. so it seems you wouldnt want end of injection to be set any less than 130 degrees. so the injection diagram in my previous post, is that showing 95 degrees (less than 3000rpm) as in 95+360 = 455 degrees BTDC? or is it actually injecting after port closes? or maybe it is showing start of injection instead of end..

arghx

iTrader: (3)

I'll admit, after over 10 years I still get a little confused because of the differences between piston and rotary. This post of mine goes really deep into the FD (and I think FC is similar) after I thought about it really hard:

https://www.rx7club.com/3rd-generati.../#post12054168

I mislabeled the diagram in the previous post of this thread. I spend most of my time tuning piston engines these days, and each increment is 180 degrees, so that numbering would be for a piston.



So that's a diagram of a piston engine crank angle vs valve lift, in this case with a bunch of overlap because of variable valve timing. The numbering in that case is ATDC firing rather than BTDC (sorry, try not to get confused)

Now If we consider a single chamber on a single rotor, it goes through all 4 cycles, but each cycle is 270 degrees, no? so 270 * 4 is 1080 degrees.



That diagram shows the port timing then, with the correct crank angle durations of each stroke (270 on rotary vs 180 on piston).

Usually those timings, at least on piston engines, are relative to TDC intake (beginning of intake stroke) and BDC intake (after intake stroke) for intake port opening timing and exhaust closing timing. Exhaust opening is BDC firing (end of expansion stroke). And we can see a similar thing if we look at that port opening area vs crank angle diagram I lifted out of the FC training manual. I think those timing specifications you pulled are actually typo'd (I remember digging into this years ago and coming to that conclusion). Look at the diagram. The spec lists the secondary port as opening at 32 BTDC, which is actually a really early opening, but it is clearly 32 ATDC in the diagram.

Primary port opens at 45 ATDC intake. Intake stroke is 270 degrees, so 270 - 45 is 225. Add another 270 degrees to account for the compression stroke, and the intake opens at 495 BTDC firing.

So when Haltech is saying that 270 degrees is the preferred injection timing, what they are saying is that they want the end of injection to be near the end of the intake stroke. Basically, they want open-port injection (analogous to an open valve injection on a piston engine). The confusing thing is that based on my own reckoning the stock FC and FD ECU is based on fixed start of injection timing. So you can't really compare them easily to an aftermarket system. This is why knowing the reference point in the software is important, because it is often based on the waveform of the crank angle sensor you are using, and there could be some kind of crank angle degree offset between that and true TDC/BDC.

For reference, the Rx-8 stock ECU uses an end-of-injection based calculation. The baseline point is 270 BTDC firing (end of intake stroke), and it advances based on an engine speed look up table. The Rx-8 has much more modern code and a much more accurate crank angle sensor than an FC or FD. I think the "fast" and "slow" nomenclature used in the Rx-8 diagram is a crude translation from Japanese or something. I think the point is that at high rpm, the end of injection timing is advanced.

DaleClark

iTrader: (55)

Interesting. Might be worth an email to Haltech to get more tech info on how the Haltech does the injector angle - how the degree they are speaking of is related to the degree of the engine.

Wondering if one of those mystery settings in the Datalogit would do something with the angle. But, it IS an older technology ECU, most likely it isn't something that can be changed. Also may be part of why they call that out in the video, showing that Haltech has that flexibility.

Dale

gxl90rx7

iTrader: (1)

i was messing around with injector angle today with the haltech.. at idle, i confirmed there is a rich spot at around 285 degrees and again around 480 degrees, with about 0.5 AFR swing between. i suspect the 480 degree rich spot is due to fuel banging off a closed port, probably helping mix with air. im probably going to just use 280 degree at idle and linearly advance it to 310 degrees to redline

Skeese

iTrader: (11)

In for the subscription so I'll remember to read through it again later when I can afford to take in the detail.

Barry Bordes

This is the only Mazda document that I can remember that indicates injector timing.
Not very specific... but at the end of the exhaust cycle just before the intake port opens.
Barry

cewrx7r1

iTrader: (2)

Settings 5: Injector Primary > Secondary Transition Overlap

From the FD3S Datalogit Manual

During the injector transition period, the secondary injectors start before the primary injectors reduce.

As boost increases, secondary injectors start earlier.

Settings are in 1/12 of a revolution of the eccentric shaft.


This is the only injection angle parameter for the PFC.