I've been tinkering with my cranking pulsewidths tonight and looking over the settings in the FAQ. It seems to me that 10ms for a priming pulse is a bit on the high side. Is everyone else having pretty good luck with those settings?
I almost fuel fouled another pair of plugs earlier with the FAQ settings. I am sure it's because of the prime pulse. I've since disabled priming pulse and have been trying to get a real solid "hot start" pulsewidth setting, but it still won't start as cleanly as I'd like. The best pulsewidth so far is ~5.5, and I have a REQ_Fuel of 9.6. That also seems really high to me... I may try the table as a source for a priming pulse and see what happens..
Granted, I am not using a FC intake and fuel setup, but seems like the settings should be similar for my setup. I got two 42# injectors which are close to the size of stock FC 460cc injectors, and I assume the primaries are the only ones firing on cranking?

 

Well, no luck.. If I give it a little throttle it starts a lot easier, but even at a shorter pulsewidth it does the same thing, so I don't think it's too rich.. My idle is pretty solid but I have no IAC or equivalent.. Does that effect cranking also? I may try and open the butterfly a little more and retune my idle if noone else has a better idea.

 

what size injectors are you using again? The ones that gave me the settings in the FAQ are 460cc, so if you're using larger injectors, anything that's specified as a pulse-width is going to need to be smaller.

Opening the throttle will probably help... Tofuball and I got around it by using his BAC valve.

 

Also, please remember that the priming pulse is exactly that - 1 (one) injection event, 10 ms in your case. This is very little actual fuel volume. The priming pulse is there in an attempt to make certain that the injector is full of liquid fuel and that any small amounts of air are expelled prior to the actual start event. The Afterstart Enrichment , Warmup Enrichment and Cranking Pulsewidth are the areas that are going to give you the described excessive richness problem. Your idle timing is another not quite so obvious item that can cause these problems - excessive idle advance will cause misfiring which will definitely fuel foul the plugs rapidly.

-Mike

 

I'm using two Lucas 42.29lbs high-Z injectors.
I looked at some of the other areas, AE, WE, priming pulse, etc, but all I wanted to do was get a good "hot start". ie, just turning the car off after it was at full operating temp, and restarting it. None of the other items should be a factor as my AE and warmup enrichment are at 0 at 160 degrees... All the fuel should already be there, so I definitely shouldnt need a prime at that time. Yet I cannot find a good pulsewidth. I shouldnt have to give it any throttle.
My VE is definitely rich. I can't trust my o2 readings because of an exhaust leak that I am trying to work out, but still...
I'm just beginning to think I need more air at startup time... I think I saw a universal IAC setup on DIYautotune awhile back, might get one of those. or I could just remember to tap on the gas a bit. hmmm

BTW, my cranking advance is 10 degrees(I think).. I can't find where to change that. Otherwise I am at -5 advance, and using the table in the FAQ. Like I said once it starts it's real solid..
I tried to lock in the timing at -5 ATC and tried cranking, but same deal. Takes about 5 seconds to start. Getting pretty confused. :-/

Also, it does tend to wanna backfire during cranking if the pulsewidth is too high..

 

Are you using trigger-return cranking? Also, if you set to time-based, and then set cranking timing to 0, then set back to trigger-return, you might get some better results. If you're using the settings I posted that should help. Finally, I think those injectors are actually slightly smaller than the ones I'm using (between 430 and 460 cc's according to the page I looked at).

I can't remember what the rest of your setup is... Are you on a 12a or 13b? Judging from your req_fuel, you're on a 13b with close-to-stock sized injectors. Tofball's S5 NA, and my S4 NA both fire up pretty quick when warm with the settings in the FAQ. It takes about 1 second tofuball's car, and about 2 seconds on mine.

 

I am using trigger return. The 10 degrees is greyed out, but does it still use that for advance? Mine will go to 10 degrees then back down to -5 before it starts.. I will check that out.

I'm running on a 12a, actually. Custom intake manifold, Weber IDF style with a CB Performance TB. Ford F150 high pressure pump, MSD-2222 adjustable FPR, GM sensors, Tweakit surgetank. No IAC or equivalent.. FC fusebox, FC waterpump housing, Taurus Efan, alt relocation, etc.
http://www.mindspring.com/~wilkinsjr/enginebay1.JPG

Not sure if my REQ_Fuel is too high or not, but it works well otherwise so I never went back to retune it.

 

I would suggest lowering your req_fuel first off... second, even though the advance for cranking isn't used for the spark timing on crank, it IS used for setting the cranking dwell... so I'd suggest setting that to 0.

With a 12a, you're definitely going to have to lower all the numbers from what's in the FAQ, although I'm not sure by how much.

 

If most variables are close, like injector size, no crazy porting, etc., and the big difference is 12A vs 13B , I'm thinking that (12Areqfuel = 13Breqfuel*(12Adisplacement/13Bdisplacement)) - reqfuel adjustment factor would be .876 for experimentation purposes.

573/654=.876

573cc and 654cc are the swept volumes per face of the 12A and 13B rotors.... very similar to the .875 produced by using the rotor width difference - 70mm/80mm

-Mike

 

Well, I didnt change my reqfuel, but did reset all the cranking pulsewidths to 10% lower than the FAQ suggested, but no good. I did change the cranking advance to 0, even though I am using Trigger Return. This does seem to help. Maybe it starts in 3 seconds now instead of 5. After it warmed up I began to tinker some more with the pulsewidths. Started at 2.8, but 5.7 still seems to be the best. Anything less is a PITA to start with. Why's it so much higher I wonder.. Cranking angle is -5, but I wonder if 0 isnt better for the 12a, also.
Would it be better to set the Hold Ignition to 0? Think I'll give that a shot next.

 

BTW, on the FC, which are the primaries? The ones on the intake runners, or the ones on the housing? I'm guessing the housings? Maybe that would have something to do with the setting also?

 

I see where you're going with this - how cold is it at your location? My injectors are way back at 17" from the port face and it does take 2 seconds of cranking or so for a start, never more, never less. I'm in Florida; the temp never gets below 40F for more than a couple of hours.

-Mike

 

You can set that to 0 if you want, and it might help, I set it to 1 on tofuball's car because his original test setup was using speaker wire for the CAS wiring, and would have spikes when cranking first started..... It allows the CAS signal to stablize a bit...

We aren't having those spikes anymore because we rebuilt the harness, but we left the settings that way because that's what we tuned for.

Setting it to 0 will probably help you noticably as long as your CAS signal is stable on cranking.

If you're using the trigger/return tooth settings that I have in the FAQ, your return is at TDC (0 degrees), which means your cranking timing is as well.

Ken

 

The primaries are on the housings.

 

I was looking at the manual earlier. When in trigger return mode, it says it's best at 0. I tried that also, but same results. Also, according to the MSnS-E page it says you must use Hold Ignition instead of Trigger Return with VR sensors? Why is that? This applies to the CAS as well, or does the dual VR conditioning circuit take care of this issue?

These settings have made cold starts easier.
Below is a link to my current MSQ file and some log file of some starts I tried. The last two are with my current MSQ file settings.
http://www.mindspring.com/~wilkinsjr/MS%20Files/

My starter is starting to complain a bit, I think it hates me.. heh It better not die if it knows whats good for it..

 

Also, during the few seconds of cranking, seems like it goes above the cranking RPM, then comes back down because the advance I set goes into effect, then it comes back to idle advance, takes a second or two, then starts with effort.. Not a clean "vroom" type start, if you know what I'm saying. I have to really nudge it along.
What is a good cranking advance? -5ATC is still good for cranking as well? I was really hesitant to fool around with it because it may backfire...loudly.

 

I use -5 for crank and idle. No drama at any time. HTH!

-Mike

PS: http://smrmicro.com/re-ky.pdf and http://smrmicro.com/re2.pdf have some interesting data and graphs re rotary timing.

 

Hold ignition just tells it not to fire the spark plugs for that many seconds after it gets a signal from the VR sensor(s). It's just like I told you... so the signal can get stable before it starts using it to fire the spark plugs.

 

It has to go above the cranking RPM for a couple seconds before it'll use the cranking advance. As long as you're below the cranking rpm and haven't gone above it for more than 2 seconds (I believe) it'll keep using the returns to fire the plugs on crank.

 

I understand that, what I am asking is why the FAQ setting says use Trigger Return when the msns manual says you must use Hold Ignition with VR sensors. Seems like it doesn't matter?

 

I'm going to take a closer look at the timing and Hold Ignition settings to see what works best. Starts are improving, so I'm making progress. Thanks for everybody's help!

 

hold ignition and trigger return have nothing to do with each other.

trigger return just says to fire the plugs on the return teeth below a certain RPM. Hold ignition just says don't fire the plugs for a certain amount of time. You can have trigger return and hold ignition on at the same time, as the FAQ does. So you ARE using hold ignition with trigger return if you set things up the way they are in the FAQ. Also, you don't HAVE to use hold ignition with VR sensors, it's just recommended.

 

Okay, I am just dense. I got my terms mixed up.
What I meant to say is Time Based vs. Trigger Return, not Hold Ign. vs Trig. Return.. Sorry about that.
Basically, on Time Based, it just waits for the specified amount of ign events, then fires, ignoring an original VR sensor spike or two? And Trigger Return does the same thing with a Hold Ignition value set? Except with Time Based, you can set a cranking angle. Why can you not set a cranking angle with Trig. Return?

 

ahh, time-based is something completely different, and I'd not recommend using that.

It calculates when to fire the plugs based on time from trigger and rpm... It works fine if your battery and starter are in good condition, but has been known to cause problems if either of those dies (kickback, etc... I think it even killed one guy's engine, though he wasn't running a rotary).

Hold ignition is the one that waits for a specified number of seconds, then fires the plugs... time based is what I described above...

You can't set an angle with trigger return because the angle is set by your selection of the return teeth in the wheel decoder settings (if you followed the FAQ, teeth 2, and 8). With the trigger angle set to 60 degrees, and the returns set to 2 and 8, with a 12 tooth wheel, you end up with a trigger angle of 0 degrees, because teeth 2 and 8 are at TDC for rotor 1 and rotor 2 respectively.

If you want to advance/retard the cranking angle, you'll have to set a higher trigger angle, say 65 degrees. Once you readjust the CAS to compensate, you'll get a cranking angle of 5 deg btdc. Also, you could change the trigger angle to 55, readjust the CAS to compensate, and you'll end up with a cranking angle of -5.

Also, for your timing, I believe on a 12a, the mark on the pulley is AT TDC, instead of 5 ATDC like the 2nd gen.... but I could wrong on that one, as I've never worked on a 12a, and I'm just pulling this from something I think I remember hearing a while back...

Last, do you know how to set the timing on the megasquirt?

It's a simple procedure:

1) get the car started and running, preferably warmed up.
2) go to Spark->Spark Settings, and set "Fixed Angle" to -5 (or 0 if that's where your pulley's mark is).
3) Using a timing light on one of the leading plug wires, adjust the CAS until the mark lines up.
4) go to Spark->Spark Settings, and set "Fixed Angle" back to -10 to use the spark table.

That's all there is to it.

 

Great info.. Thanks muythai. I've read the manual and places in the FAQ, but it doesn't go into detail about how these settings are used.
Yeah, the 12a's pulley is marked at TDC. I changed the Trigger Angle to 55 on my setup to compensate. If I don't use that, I don't have enough room to adjust it for a proper set.
I did properly zero my timing when I did my install. It was as dead on as I could get it. I may check it again to be sure, but it will idle great, even when cold with no IAC, and it runs well aside from some VE trouble I am having.