I've been working on tuning my 12A turbo setup and I'm running into an interesting issue in regards to the VE table. Idle, low rpm, etc. are all pretty well sorted, but up in boost I can't get enough fuel (VE table maxed at 255). I've logged the fuel pressure and it's not dropping, so I'm not really sure what's going on. I'll attach the tune and a log below, but please keep in mind that it's a work in progress. Also this is running on a Speeduino V0.3.7, so I figured you MS guys would be my best bet as it has similar functionality and uses TunerStudio.

Relevant specs are:
- FIC1000 injectors x4
- Areomotive 13136 FPR
- Custom TBI setup
- Walbro 255HP with surge tank
- dizzy ignition, DFI leading

It's an odd setup, but so far everything is working well enough, with the exception of fuel in boost - seeing 13-14 on the AFR gauge where I should be in the 12s, and I can't seem to add more fuel. Secondary injectors are on full time due to the quirky TBI setup.

In the next couple days I'll redo my FPR boost line so that it sees vacuum as well instead of just boost. I had it run that way before with the carb since it would pull too much fuel at idle, but with EFI that's not an issue. Once I have that I can bump up the fuel pressure a little since idle pressure will be lower, but I don't feel like that's the main issue, although admittedly I'm not sure what else it would be. Note that ~34psi is the warm reading, cold it's at 46psi.

Curious if anyone has some thoughts.

 

Step 1, STOP driving the car until you read the following

On the current tune file, you are locked timing to 0 degrees, so are not using the timing table.

Your cranking, running dwell is 0. Spark duration is also 0. Your spark, if it is even firing is likley extremely weak

Cold advance is set to -15 degrees @ -40 degrees, across the board meaning it stays at that all the time, as you have nothing to remove the advancement as temps go up. It holds the last setting off the end of the scale

It sounds like the car is stuck at -15 degrees of advance, so it idles and can drive, but your dwell settings make the spark extremely weak, and the unburnt fuel in the exhaust means that there is still a lot of air that has not reacted in there too, meaning the 02 sensor is reading lean because combustion is not happening and it reads the oxygen. The log displays 0 for ignition advance during the entire log, confirming that you are still locked on timing to 0. The cold advance is then removing another 15 degrees from that. Your telemetry is recording the advance, but not total advance, would need to set up datalogging to record that value to see how the cold advance is effecting it too.

I am not sure about the physical 12A throttle body, but you have the primary and secondary's sharing 50% of the total pulsewidth across the board. With the 2nd gens we wait until the second set of throttle plates open so there is airflow in those intake runners. The reason I bring this up as running 1000cc injectors, trying to get those to fire for such a small pulse width will make it harder to tune at lower RPMs, so once all the other above gets sorted, might want to only have the primaries running at lower RPM before then splitting the load between the primary and secondary's. You will see this once you fix the other stuff. I am using MS3x on my Miata as well, with 1000cc injectors, and it had its own low pulsewidth settings because of how the physical properties of the pintle open and closing is much different the shorter PW you are commanding.

You are likley going to have to retune the entire VE map as those things are going to make combustion start happening in the engine and not pumping out raw fuel and unused air that the O2 sensor reads as lean.

 

Thanks for the input, but as I mentioned, I'm using the dizzy for ignition still. Any ignition related value in TS is doing nothing on the car (unless there are some background calcs I am unaware of). The car runs and drives fine, although it wants to be a little richer in cruising since I have no ability to get ignition advance there (other than mechanical advance in the dizzy). At some point here I'll get some IGN1A coils or something, but until then this is working well enough, with the main caveat being poor fuel efficiency at low load.

As for the injectors and why they are running full time. The TBI setup is a single throttle body, and due to this air is flowing down all runners at all times. I had originally tried with the injectors staged like normal, but what ends up happening is I have to run extra rich to compensate for all the air coming in through the secondary runners. This issue was avoided by running them all full time, although the pulsewidth is small (1.7ms at idle). At the other end of the spectrum, if I do run out of duty cycle with semi-sequential (which is possible since it is split 50/50 right now), I can simply switch to batch and flip the two secondary injector wires on the ECU, but that's an aside. The car runs and drives well enough, so these quirks are not something I am concerned with, nor are the point of this thread.

Anyway, I believe I figured out the issue (or a likely solution) last night - I've been tuning without multiply by map enabled. That would explain why my VE values get so high up top and are very low at idle. In fact, I halved the req fuel a while ago because I couldn't get enough resolution at idle (doubling all VE values). Now I see why and I can go back and fix that. I'll update again once I've worked on it some more.

 

Well the Multiply by Map option did in fact fix my VE table running out of numbers, so all is well there. I think that's about all there is to say so... off to fix other issues