94 RX-7 Twin Turbo (FD)

[13BeastREW]

Using MSnS-E v. 029q...

Doing a little work on this now. Usually I've been warming my engine on the stock ECU then switching to MS to tweak settings while I have O2 readings. Right now however I've decided to get cranking working like it should.

I've been looking over the FSM and noticed the FD ignition settings for cranking and idle. While cranking the FSM specifies that igintion timing on both leading and trailing is fixed a 5* BTDC. While idling, the FSM states leading should be 5* ATDC and trailng should be 20* ATDC. I went ahead and configured MS to reflect that.

Thinking about that I started questioning my req_fuel and VE Tables. I recalculated my req_fuel to 9.1 using 2616cc displacement, 550cc injectors, and 12.8 fuel ratio. The VE Table was regenerated using 2616cc displacement, and idle of 700 rpm @ 20kPa, peak torque of 217 ft. lbs. @ 5000 rpm/100kPa, peak horsepower of 255 bhp @ 6500 rpm/100kPa, and redline of 8000 rpm @ 100kPa per mazdausa.com specs (kPa values were unmodified from their default values).

Per the megamanual, cranking pulse widths were set with -40*F being 88% of upper req_fuel value, and 180* F was set to 23% of the upper req_fuel value. This came to 8.0 ms @ -40*F and 2.0 ms @ 180*F.

None of these settings get the engine even trying to start but I should atleast be able to be confident that my mixture is very rich and should be leaning the settings out right?

I'll be trying this on my own if I'm not making progress soon but would it be helpful to set the cranking and idle areas of my VE table to 100% until I'm able to get the engine to catch while cranking? Right now those areas are 41% to 64% range.

[MegaScott]

I admit I don't have much experience with the rotary, but i imagine it's not that much different from any other engine as far as cold start.

In my experience, the engine will start when really rich, but won't start at all if lean even just a little, if it's too rich you'll know by the black smoke out the tailpipe, or of it's excessively rich you may see fouled wet plugs, I imagine not a good thing for a rotory to have ~liquid fuel running around with the rotor scuffing up the seals.

So what I do when I have hard starting cold, richen up the cranking enrichments until it catches, then richen up the ASE until it idles good until warm up enrichments kick in. Some amount of tweeking is going to be required based on the outside temperature, but once you get it close it's not that hard to get colder temps dialed in.

Of course all that assumes your timing scheme at starting is good enough, I assume you have that figured out though by the fact it starts fine when warm.

[13BeastREW]

So what I do when I have hard starting cold, richen up the cranking enrichments

I kinda figured calculating req_fuel with a 12.8 ratio would make it very rich. Provided I'm not fouling my plugs, if its still not catching you'd suggest increasing cranking enrichments? My aim was to start rich and lean out.

Of course all that assumes your timing scheme at starting is good enough, I assume you have that figured out though by the fact it starts fine when warm.

Actually I'm not sure how it behaves when warm anymore since I've started hacking away at the spark tables to get them to reflect what the Factory Service Manual suggests for cranking and idle. I started off with spark tables from an older N/A model RX-7 engine for lack of an msq file or settings from a turbo model. I figure while the engine isn't boosting, except for the turbo engine having lower compression (9.0 vs 10.0), behaving around idle should be able the same for both engines.

I still have my tables and msq files from before the modifications I made today so I can always go back. The problem from the start however has just been trying to get this thing running on MS. Runs fine on the Mazda ECU.

[MegaScott]

Yes, if 8.0ms is not enough to get it to start, then try perhaps 10ms and see if that's better, remember the way the injectors fire when cranking is different than when running. As the manual say's, these calculated values are just suggestions, variations from the calculated values are going to be required, or else you could just calculate everything in advance, and not have to tune anything.

Once you get it started, ASE kicks in first for a time, then WUE, so you need to tune each step accordingly as per the Megamanual.

When starting from scratch, your timing might be off some, which creates two sets of problems. Is it not starting because of fuel or timing? A quick check with your timing light should rule out the timing problem. I don't think leading or lagging has much of an effect when starting, I would think it should start on just one plug or I may be wrong.

edit - I looked at JCKreuger's .msq posted on his success story, he has a Req fuel at 4.0, and the cranking PW at 16ms and 4ms respectively. so one would think with a 6.5 Req fuel that it would not be u nreasionable to have a PW of 14 to 3ms for cranking enrichment.