Runs very poorly/stalls after installing new injectors
 

Hello everyone,

I'm turboing my NB and I'm learning about tuning the ECU myself before that, so I'm messing around with it stock. I've gotten my tune to run pretty smoothly and have a consistent idle(on neutral at least, car is still on jack stands) but ever since replacing the stock injectors to Bosch EV14 640cc injectors it barely wants to start.

My previous required fuel was 11.7 (with the 230cc stock injectors). The calculator changed that to 4.2 when I inputted 640 but the car wouldn't run at all. I saw that at 4 bar which I think the NB creates the value is 753cc instead which would put the required value at 3.6, still nothing.

I've messed around with raising the required fuel value to something like 5 - 5.5 and it seems to start but can't run idle and if you have the foot on gas the AFR and RPM is hunting.

Am I doing something wrong with the calculations? Shouldn't changing the injectors and putting the correct required fuel value be enough and not need to alter the VE Table?

I've attached my tune and a recent log which was running pretty terribly.

BTW I'm running a Speeduino (RM Electronics)
Car is 2003 NBFL 1.6L everything stock.

Changing injectors and updating required fuel isn't enough. You'll need to completely retune your VE table.

It's also critical that you update your injector deadtimes. You'll probably be closer once you do but retuning will be necessary.

Okay thank you. I'll be charging my battery tomorrow since it got drained from cranking it all day trying to tune it and will get back to you in 2 days tops.

What he said. But deadtime first.
I put in 640 cc injectors using the same learning strategy as you, and had a fair amount of trouble getting it to run. I just kept increasing the dead time until it would start and idle.
But it was quite a bit higher than the dead time that the manufacturer claimed.
Once it ran, I dropped the dead time lower and did a VE tune.
Then I dropped the dead time and did a VE tune, then I dropped the dead time and did a VE tune.
And so on, until I had the dead time down close to what the manufacturer said.

Note dead time goes up as fuel pressure goes up. Stock fuel pressure is around 62 psi on the 99-05 models, with no fuel return line.

My MSPnP was pre-set to think it had vacuum referenced fuel pressure (NA version at around 40 psi), and I had tuned it on stock injectors using that pre-set. So I changed that too while I was doing the new injectors, further complicating the adjustment steps.

I ended up with 1.08 ms dead time, where the manufacturer expected about 1.045 or something like that. It worked on less, but was very hard to start when temperatures dropped below freezing, so I jacked it up a wee bit, and did some extrapolations on pressure that suggested 1.07 was actually probably what I needed.

But I had first gone up to around 1.25 (maybe 1.125?) or somewhere near that to get it to start and idle, and then came down in ~0.05 steps with a VE tune between each.

Just an update.

I've followed the advice of both of you and we had some success today!

You are right that I had to completely retune my VE. From starting from 65 at idle it's now at 30-35. I found that I had to work on my acceleration enrichment as well as I found that it would bog down on throttle which I had solved before. Maybe it's cause the VE table is not 100% perfect yet.

My idle was at around 600 in the beginning but working down on the deadtime(it's at 1.4ms now, spec is at 1.26) and adjusting the IAC duty cycle along with the VE I was able to get it to 830-850rpm.

Will need to take it to the road to let Autotune do it's work.

Updating this thread.

I'm running into two issues right now.

Alternator is outputting around 12.2v, battery is charged at 13.2v however the ECU is reading 11.8V. By the end of my 15-20min ride, the battery voltage dropped to 12.8 and the ECU voltage to 11.3V. Didn't check the alternator as the engine bay was very hot.

This is probably not a new issue as the battery has died before when tuning the car. I put that off as being caused by all the cranking but it should be higher voltage when running so something must be up.

Second issue is the acceleration enrichment. I'm still trying to come up with a value to not have the car bog down when getting to the gas quickly, like starting off on 1st gear or going wide open. If i set the value really low like all the other tables I've seen the car is almost ready to stall. If I put the enrichment at almost top(250%) then it's better but still not good enough.

I've attached two logs and my tune, first log is my trip where I let Autotune work on my VE table and the second one is me sitting in neutral blipping the throttle.

The alternator on the NB receives control signals from the ECU. Mine worked fine, so I did not have to do anything to the software settings. As a result, I don't know anything about it. There is a section in the MS3Pro manual that can give you some advice.
But perhaps the alternator is simply not working. When I fear that, I take it out and have a shop bench test it, but if you have a good, around the lead, current meter you might be able to judge it that way.

I had to lean my enrichment out a lot, to avoid large clouds of black out the tailpipe. But I also had to increase the VE at low load and low rpm, so my new injectors seemed to want the opposite direction of what you have needed. Have you checked the % change in throttle position settings? Perhaps they are too high?

This bogging down on accel is happening pretty much no matter the current rpm and/or speed. Just when you blip the throttle. Seems like it's running richer that it should when i'm cruising but not rich enough when I'm on low throttle. That's why I'm getting the impression that perhaps the problem lies on the other parts of the tuning, mostly the Injector characteristics. This is supposed to be the specs for my injectors https://bofiracing.co.uk/wp-content/...40cc-PnP-1.pdf although I'm not able to get it exactly the same without it stalling.

I have attached the alternator control settings that are working on my car.
I also attach the settings I used on accelerator enrichment. They are a first attempt to control the over rich condition on overrun and then re-acceleration. The car does not bog on these settings with my VE table and injectors, but they may be wrong for yours.
You can set the log to display pdotTPS, and AFR and TPS and rpm versus time, and look at how they interact as you tip the throttle slowly, and then more quickly. It could help guide you to some settings. The MS3 Pro manual has a good section on how to work through this.

You see from your injector properties that it is very sensitive to voltage, and you do not have a stable voltage. I think you may need to solve that first. Also, I believe it runs at 62 psi. You should do a linear extrapolation from the two pressure/dead time points you have to see how that changes dead time. I expect it rises to ~1.3 from 1.26. So your 1.4 is a bit high, but should not be terribly off. It might help if you can get it to 1.35, but that should be fairly good. However, the voltage variability and the voltage correction curve might be a bigger problem for you.


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Thanks for sharing your tune! As I'm running a speeduino it's not 100% the same but I will try to replicate the settings.

You are right about having to fix my voltage issue first. I will be contacting my ECU manufacturer to see if I can find out if it's the ECUs fault or it's just that that the alternator suddenly failed.

Was told by the guy that made the ECU that the alternator control unit could be broken. I've ordered an external alternator controller which I would be putting on the car shortly when I receive it.