Hi Guys,

Been trying for a while to get a good start on my little 12a, and not having really any luck. ONCE it has kicked and revved to around 3500rpm for a few secs then died (I came off the gas and had no idle control) but I haven't had a fire since. The setup is....

12a Bridgeport
4AGE silvertop ITBs
550cc injectors (one per runner/port)
Coil on plug using LS2 coils
GM CLT and IAT sensors
14point7 WBO2

Spark works, I've confirmed base timing at TDC. At first I think my "Required Fuel" was too low, no firing but flooding (I assume due to no firing) I reset my "Required Fuel" and it pretty much doubled my pulse width, this is when I got that "decent" fire described above but I've had no luck after that. I suppose my main concerns are:
- fueling (how accurate do I need to be to get a good enough mixture to fire???)
- cranking RPM, really it tends to crank around 200rpm until the battery gets a bit tired and the starter gets hot. I have an 830cca battery

Any and all help/insights are available attached is an .MSQ I couldn't upload a log for some reason??.

Thanks,
Karl

 

Is this a new build? Engine ran before the Megasquirt?

Without a datalog it's hard to see what might be wrong as your MSQ looks OK.

However based on your description, it is not enough fuel.

If you think you have enough fuel to start a bridgeport, double it, then try again. Especially with injectors high up in ITB runners.

Assuming about 40 PSI fuel pressure, you should see about 12 mS on those 550CC injectors during starting.

 

Yup it's a new build, never run beforehand.
Fuel pressure is high, like 55psi, injectors are pretty high in the runners, about 200mm from the ports. I'l keep cranking the gas then

I've attached a few logs, as .zip, just rename them to .mlg

 

Looking at the "kinda ran" log, try lowering your cranking RPM setting to around 200.

You don't have anywhere near the amount of injector time necessary, so not enough fuel. I'm setting around 3-4mS. Double or triple that.

Bridgeports need a lot of fuel to start as vacuum is low.

 

OK so I have had a better start since this all but have been unable to replicate it, in this start I have just under 12ms pulse width which aligns with what you are saying Aaron. it gives me a little more confidence. I'm now a tad stumped, I still feel like maybe my starter isn't quite getting the RPM I need?
Is crash starting a better option? Do I just persist with what I'm trying here?

Attached a different log showing the "better" start, again it's had the extension changed to .zip so I can attach, it'll need to be renamed to .mlg to open.

THANKS in advance
Karl

 

What are you using for timing?

 

13b CAS setup attached...
The log does show some sync errors (error 11 too few teeth before secnd trigger??) but I'm getting well timed spark on both 1 and 2 leading plugs so I don't know if that's material?

 

Turn fixed timing off and try that. do you have all your grounds go to the same place? Are you using noise filtering?

 

nah all my grounds are seperate, I turned on fixed timing just to remove some variables, I figure it shouldn't matter for just a start up??
I don't think I'm using noise filtering, can you expand on that??

 

first make sure that your ground and power go straight the the battery,change the skip pulse to 5 your ignition input to falling edge and your fix advance to use table.

 

Happy to do all of this, for my own learning can you describe why I would use:

• skip pulses of 5
• falling edge triggering
• the advance table as opposed to a fixed number?

not questioning any of it just for my own knowledge

 

1.will ignore X amount of ignition capture pulse before start syncing
2.thats what i always use and work great for me
3.will use your timing table and not your fix timing (lock timing).

 

Sorry yeh I understand what the suggected settings would do "mechanically", I'm more interested in the reasoning behind them, for instance:

1. Why do I want to ignore the first 5 pulses before syncing?
2. This is fine haha
3. Why use the table as opposed to a known fixed value? I intentionally went to fixed so I could remove an extra variable when trying to get a start. I was intentding to go back to the table once I had fuel figured out and it started. Is this not the right thinking??

Thanks for you help, I really need to get some time to get back out to the garage and try some of this stuff

 

Hey Guys,
Back at this again, I've made a few changes but still not getting a start. What I've changed:

• RX8 starter lifting my cranking RPM to around 240
• Hopefully resolved my sync issues, I'm getting a clean Comp log now

Log (renamed as a .ZIP again :/ ) and MSQ attached, cranking pulse is lilk 11-12ms I've dicked around will all kinds of cranking ign numbers between 0-20 deg BTDC and nothing seem to make a difference.

Help

 

If your cranking RPM is 240rpm (wow! I gotta get me one of those!) you need to set your cranking RPM setting to something higher like 300-350, otherwise you will be cranking on the main VE table and not the fixed cranking pulsewidth.

I'm not near my laptop with TunerStudio to look at your msqs, but I've had 22 degrees BTDC fixed timing (leading and trailing) and GSL-SEs had 5ATDC/20ATDC idle timing, so it should still start with timing anywhere in that range. I like to idle my bridge ported engines down around 0 degrees to cut idle vacuum down for a smoother idle. Could get a dead smooth 900-1000rpm idle at about 85kpa.

Your cranking pulsewidths seem high to me if you are using all four injectors when cranking. IIRC my cranking pulsewidths were in the 7ms range with two 680s at 35psi rail pressure.

 

Yeh the RX8 starter has made a massive difference. It's a Auto starter I got from Rock Auto, and modified the housing to bolt to my engine....


I am using all 4 injectors at all times so I'll try with a lower cranking PW (I have my cranking RPM set at 350 already I think). my rail pressure is a lot higher as well (liek 50psi) and I haven't experimented with getting it lower. I'm definitely getting a lot of fuel in the engine, in fact a lot is coming out the exhaust as well.

It sounds a lot like a fueling issue rather than an ignition one so I'll set ign to something like 10 BTDC and forget it, focus on fuel. Is there any secret with spark plugs?? I'm currently running an NGK B7ES, which is a single electrode plug, are there other options that are better for this???

 

I can't view your log, I might be doing something wrong on my end.

Looking at your MSQ, my main thought is, what is your injector pulsewidth when cranking? If I'm reading it right, you have it set to fire all four injectors at every ignition event, and your req_fuel looks twice as large as it should be. This is a comedy of too much fuel. The linked msq also has cranking RPM at 200 which is too low if your engine is cranking at 240, so you'll be cranking on the main VE table.

You also have the engine size wrong, but that isn't a gross enough error to keep the engine from running.

Another note, with a bridge port, you really need to have the throttle open when cranking or the engine will mainly pull air from the exhaust, not the intake manifold. Not so much a problem on an engine that hasn't run but a big problem on an engine that was just shut off.

My advice? Disconnect the injectors, clear-flood it, and try starting it on starting fluid. That will eliminate an ignition problem as your issue.
Also, I really REAAAALLY suggest you get air filters on that. The fastest way to kill a rotary is to run without air filters. Dirty air destroys everything: side housings, side seals, apex seals, rotor grooves. Ever see apex seals worn .4mm thinner than spec? I also have a half dozen 12As with unusable side housings because people ran them without air filtration. The carnage is depressing.

 

Perfect thank you,
yeh i had been messing around with a bunch of stuff last year and forgotten I had changed a few of those things, the Cranking RPMs was only set that low for a small period, (obvs when I pulled that MSQ) it's 350 now.

I'll reset my base fuel and change to every other event, that should effectively halve my fuel I assume. I'm absolutely still learning basically all of this haha. In regards to staring fluid do I just spray a shitload into the throttles??

Air filters are on the list, I def won't be driving it filter-less.

Cheers,
Kahl

 

Morning,

I had a small success on the weekend, got the car to fire, it "idled" for about a second then died and I couldn't get it to light again. Still it's progress, I want to understand what things might have caused it to stop running, I have attached a log (again renamed as a .zip), any insights you can provide are welcome. You can see it fired then I went to 0 throttle, it sat there for a little bit and died. I have my throttle stops on the ITBs wide open, hence the high idle.

Cheers,
Karl

 

What do you have your MAP input as? It looks strange. It doesn't follow anything when the engine is running.

Usually if you can get it to fire, and then it dies, that is because your fuel table needs to be adjusted. It runs on cranking fuel and afterstart enrichment, which tapers off to nothing after a short time.

 

Great questions, I noticed the MAP was outputing some regular cycle but figured it didn't matter because I don't have a MAP and am running Alpha-N? Anyhow I have attached a pic of the MAP sensor config.


Also in General settings I have "MAP Sensor Input Port" set to "MAP", if I change that to Off/None I get an error also attached. Do I also have to change the "Multiply MAP" setting??



I'd assume if I could turn this off then we wouldn't see any for MAP in the logs but equally I had also been assuming that none of this mattered anyway becauser I am running Alpha-N???

Also I really appreciate all the input I'm getting, this is amazingly helpful and I am learning HEAPS

 

SUCCESS!!!

I had a couple of good starts today, held idle and didn't just die on me. I'm pretty happy if I'm honest I turned the MAP off and maybe that helped? I dunno.

Anyway it's not like it was easy to start, in fact each time it took a bit of fiddling around, what I was finding was I'd get little half ignitions I would see RPM slowly rise from 250 up to 280 over the course of 10 secs of cranking, then I'd drop the cranking PW and try again, I'd see RPMs at 280-290. Then stop, drop the cranking PW and try again seeing RPM between 290-300 RPM, continue for about 5 rounds then it'd catch after cranking around 400rpm.

It seemed to me like it was needing a bit of heat in the block maybe??? I'm hoping this will settle after a decent run?? Also AFRs are all over the shop any advice on that would be great. Again a log is attached.

Cheers