Hello, I'm trying to get my NA miata running after doing a bunch of work, mainly installing a new built motor and new injectors. At this point the car cranks mostly freely when I have the throttle pinned, but when cranking normally the engine will crank for a moment then backfire and pause before continuing to crank sluggishly. I can see that my battery voltage is dropping significantly so I am doing my testing with jumper cables connected to another car which is idling.

I am running a MS3 PNP Pro.
Log of cranking attached.
Tune attached.
The motor is 12:1 CR, 10mm 264 degree cams, +1 valves, AE101 ITBs, in case any of that is relevant. Injectors are ID1000s.

Thanks in advance. Any help is much appreciated. So far it seemed like I was getting better results by reducing fuel, but that didn't really get me far.

 

Try changing your cranking advance in ignition options to -5 instead of 5. With flood clear activated, it disables fuel and (I think) spark, so it cranks freely. When not active, it's trying to ignite in a way that stalls the rotation.

If it doesn't work, try -10. If it does work, do another cranking log and make sure you're not dropping under 10v. You went as far as 8.5v in that cranking log, but that's most likely due to the extra load during the "stall".

 

I will give that a try shortly. Any danger with my current VE table? 10 seems extremely low, but I'm not sure how the injectors, cams, and higher compression all play together.

 

So -5 didn't do much, but at -10 it started to catch for just a moment, but failed most likely due to voltage dropping too low. I did not have the donor car hooked up and it's a bit too late to do that where I am now.

 

What trigger wheel are you using and what did you set the trigger angle to?

 

I didn't look at much else beyond the cranking advance, since that and/or low batt v seemed to be the issue. But looking at it now, your VE table is actually 20-25, idle ignition is 10. You can easily idle at 18-24 degrees, but 10 is fine. Once you enable idle advance correction to stabilize idle, 10 degrees could turn in to 0, so I like to idle around 16-18.

The rest of the tune looks ok, although you don't have EGO enabled, your rev limit is 4000, and your ignition table could easily go up 2 degrees minimum, but it's plenty safe for now.

Actually, you do have idle advance correction enabled, so it'll pull up to 12 degrees if you happen to be 300rpm or more over target, so you'd be idling at -2 degrees. I'd fix those settings (increase idle adv. and decrease timing correction to ~-10).

I'm sure there's more, but that's what I see for now.

He's using a 36-2 trigger wheel, should be +/- a couple degrees from zero, and he's at 2.

 

tried checking for vacuum leaks? sometimes they can cause weird starting issues.

 

This is intentional. With the lightened valvetrain and light weight 1.6 clutch and flywheel this thing revs like a sport bike. I had throttle cable issues when I first started a build once which revved the car to 5k RPM almost immediately so I figured I would put some guard rails in place.

Thanks for the tips, I will make those changes, do some testing and tweaking, and report back.

 

No vacuum leaks at the moment. I am running a vacuum block with limited connections so it's a pretty simple system.

Also as far as idle goes. I do have an IACV rigged up, I believe the idle correction was used by my previous tuner who used it in place of an IACV to tune the previous iteration of this car before the motor went (junkyard engine VVT that was apparently in bad shape). I'll make those changes as well as it looked like my IACV wasn't enabled, which I will fix.

 

It's alive! Turns out it was a pretty stupid ID10T error. I re-wired all of the engine controls from scratch, and it turns out I had the front coil wired as coil A, when it fires cylinder 2 and 3 so therefore should be coil B. I flipped those two around and it fired right up (with a jump starter). My battery is only 2 years old so I thought it was odd it would be gone already, I guess I should have listened to the car trying to tell me there was something else going wrong. What clued me in was a bit of smoke wafting out from the throttles, which is a common sign of ignition issues.

It now idles, but dies immediately when I give it throttle. Now I can play around with tuning the car, at least until I run into the next road block and need some more help. I very much appreciate everyone's assistance here.

Oliver says thank you.

 

Maybe I need to make a new post at this point, but I'll just keep everything in one place for now. I have achieved a stable idle that is able to react to changes decently, but I am now having trouble getting the engine to react to changes in throttle without either dying or spiking too lean. When I carefully apply ~5% throttle over the course of around a half a second everything goes well, but blips from idle tend to go poorly. Once I'm at a steady 5% throttle blips tend to cause a lean spike, but otherwise don't cause a shutdown or much knock.

My research so far has led me to believe that my next avenue should be to look into tuning my acceleration enrichment. Would this be a good place to start? I still have a lot of work left to do tuning my VE table, but I am concerned at this point because throttle application from idle is causing a bit of knock unless I am very careful and I'd rather not cause any damage.

Thank you again. Tune and log attached in case anyone wants to look into it.

 

Your accel enrich looks in the ball park, I would start by adding fuel to the VE table. I ran the above log through MLV's VE analyzer, and it added a decent amount of fuel above 0% throttle. You may want to add a 2 or 3% row. I would start by hitting every RPM column and manually adjusting VE to match target. I would also expect increasing advance to help accelerate the engine to higher RPM. Your ignition table stays around 10-12 degrees in the lower RPMs.

On a completely untuned engine, you shouldn't have any cylinder trims active, but you do. Select all of those tables in the fuel settings tab an zero them all out.

 

I have not yet touched the ignition table, but I'll bump that up by one or two degrees to see how that helps next time I touch the car. Cylinder trims have been zeroed out, thanks for that tip.

The tune is a bit better at reacting to throttle input, but I keep running into a situation where something seems to be blocking the engine from recovering its idle. I took a video and attached a log demonstrating this situation. You can see that from idle the first time I blip the throttle everything works great, but the second time the engine is locked around 650 rpm and runs poorly. timing is about 21 degrees here. The third press of the throttle kills the car. What might be causing this? I don't really have a clue at the moment.

 

Do you have an idle valve plumbed in? I know sometimes ITB setups don't. This idle/return to idle/off idle accel issues you're struggling through are going to be your main hurdle. Past this, cruise and WOT is fairly easy to tune, the rest is typically the hard part on any setup, but ITBs make it that much more difficult.

 

I have an idle valve I believe from an NB plumbed into the vacuum block. In test mode I was seeing some response from the engine when sweeping from 30-90%, but not much. Maybe it's not plumbed correctly, I'll check up on that.

I'm very much looking forward to the point where I can drive around tuning, this is definitely the part I was most concerned about from my experience with this a couple of years ago.

 

Correction: I THOUGHT I had it wired up, but it looked like I had not yet terminated the connection to the ECU. Working on that now, because that should be a huge help.

 

Wow, ok now that did something. I am maintaining a steady 14.7 AFR idling and the tune quickly responds to disruptions without any issue. I even was able to drive up and down the alley 50ft without a fuss. Now I should be able to get to work, thank you so much.

 

There you go! Sometimes it's the little things.

 

Maybe not such a little thing. I very much do have an interference engine, and I did not mention but I actually mistakenly wired the VVT solenoid control to the IACV location for about half of my testing. I believe I should be fine based on my measurements during assembly, but I'll have to add a leak down test to my todo list. Either way, I very much appreciate everyone's support. I spent all day yesterday getting the car prepped to drive around letting VEAL do it's thing all week.

But as of yesterday the car idles beautifully. Cold start in the morning was perfect as well. In the words of my brother, "it sounds like a normal car."