1994 Nissan Sentra SE-R going VEMS, then turbo.

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When cranking you're firing all injectors at once, then when it catches the injectors fire sequentially, so you're getting a 1/4 of the fuel the moment you go from cranking to afterstart.

[BenFenner]

It feels like maybe I'm firing fuel on two closed valves, and two open ones. Except... That can't be right...

I had a feeling I wasn't getting enough fuel during the transition... =]


Well... With this new knowledge, what would you suggest? I guess I need 4 times more fuel (you sure it's 1/4th and not 1/2?) during afterstart to just match the amount I'm getting during cranking, correct?

I'll make it give way more fuel after the threshold and see what happens... =]

[Tcal]

Try even bigger values in those...
I have:
Crank cold PW 10.0
         warm    2.9

Threshold 300
Crank adv 17

Added 160
Scaling 3.5
Duration 300

I have all injectors firing when starting...

[Tcal]

And is Coil chargetime 6v in ignition settings  set ok?

[BenFenner]

And is Coil chargetime 6v in ignition settings  set ok?

I was told to put that value at 0.0 by Rob, and I think it forces 0.0 in my firmware anyway... So that's what's going on with that.

Thanks for the good info. I've got similar values to you except the Added and Scaling values. Yours are quite different.
Mine look like:

Crank cold PW 15.0
         warm    2.5

Threshold 400  (for now to get it running)
Crank adv 19

Added 65
Scaling 5.9
Duration 700


I never really understood both of the values fully. I know changing the "Added" value will add or take away fuel during afterstart, but what does the "scaling" factor do, and what exactly does the "Added" value do?

[Tcal]

Take a log where this problem appears, it would help a bit.

[[email protected]]

I would start off with setting cranking to alternate and increasing the cranking PW significantly so that you can get the car to start - that will give you the starting point for where you need to be.  When you get it firing with the cranking PW I'm betting that you'll see a massive drop when the afterstart enrichment amount comes in.

Not sure why I'd have said that coil charge at 0 would be a good idea, although I have been up late some nights figuring it all out!
Try setting it to 2.

I spent AGES on the first car I set up getting the cranking and afterstart sorted out, initially I had the cranking threshold at 1200rpm so that I could work out my various target Pulsewidths, which gave me an idea of what the engine required where.

[BenFenner]

Thanks for all the good help folks. I've got things to play with now. Hopefully I don't hit the pw cap (25.5 ms) before I get enough fuel to start this thing with alternating banks...

On a side note, anything above 24 seems to be misinterpreted by the ECU as 0.0 or similar (I found this out a while ago trying to give more fuel at some point).

I'll set 6v dwell time to 2.0 (v12 dwell time is set to 1.98 right now and ignition is working perfectly).

[BenFenner]

First attempt at getting cold start working with new settings failed (flooding I think). I gave it a few weeks and tried again.

I got the car to start just as well as it used to, but this time with cranking threshold at 300 rpms, and firing on alternating banks while cranking. I even got the car to start right up (once) this way while at 6C.

I've since worked with the 6v dwell time, and lowered the cranking timing advance to 15 (after taking a look at the AEM settings in DanMartin's SR20DET powered Sil-eighty). The car started right up this morning at 8C and I'm pretty sure I've got cold start licked.

I'll be tweaking things a bit, but it seems like I've got all of my drive-ability issues taken care of. I'll be posting settings of everything (VE table, spark table, idle, cold start, etc.) after I do a little bit more work on a few things. Sometimes I can't believe I've overcome all the hurdles I've ran into. I'm happy with my first stand-alone experience, and very glad I did it.

Cheers!

[[email protected]]

Nicely done Sir.

Don't let anyone tell you fitting a stand-alone is easy, especially on an engine thats not been done before.

If it was easy it wouldnt be worth doing

[BenFenner]

Car was misbehaving when letting off the throttle (needs decel enrichment). Problem was visited and solved in the fuel section:
http://www.vems.co.uk/forum/index.php?topic=412.0

[BenFenner]

Just got back from a 2,000 mile road trip. On the highway I averaged 33.5 mpg which is right in line with stock. I'm getting a bit less fuel efficiency than I used to around town (19 vs. 22 mpg), but I'm not too worried as the turbo install will change all that. It could also be due to the winter weather which causes longer warm-up times, meaning longer warm-up enrichment. I'll see how this changes as the summer comes.

The trip was free of major events as far as VEMS is concerned. The LCD display is getting worse (used to not corrupt on the highway, but messes up even then now) and since plugging my front audio amplifier in, I've got what seems like injector feedback causing popping in my audio speakers. I'm going to remove both horrible, analog (Jensen) 2-channel front and rear amps and replace with one, digital (Alpine) 4-channel in the rear which should solve the problem. I've got some grounding issues... Oh well. Not VEMS's fault.

Next up is either larger injectors/fuel pump, or clutch/pp/flywheel install. We'll see.

Look for screen caps of my VEMS settings soon, as they should be the current starting point for the USDM FWD SR20DE engine. One of the things I wanted to accomplish was a configuration that takes most of the guesswork out for anyone following in my footsteps. I'll make comments on most of the settings as well. It should make for good reading, and it should make obvious which settings I'm confident with, which I'm not, and which I still have questions about.

[[email protected]]

Cool, your configs and tables are your property but if you care to share them then they're the best way to make the settings available.

[BenFenner]

Yah, I'll make the config and table files available as well. Don't you worry.
I just like screen caps better for some reason (have had trouble loading configs in the past, yet entering values manually worked a charm).

[BenFenner]

I know I've been a ghost here for a while. I graduated from college (7 years of it for a 4 year degree) and I'm working on getting a place with my GF. The car work has kept going, but not so much on mine. My car has seen some suspension installs and some suspension problems, etc.
As for VEMS news; I got the car to a dyno and was able to do some meaningful tuning. Just in time too, as the warmer weather had brought on some detonation. It turned out I was about 6-8 degrees too advanced at WOT. Can't get blood from a stone they say, but I apparently was trying.
So, the timing was brought back to reality. I was running leaner than I'd planned, so that was fixed as well. After working out the bugs, the 4th pull resulted in somewhat of a record for a stock SR20DE. Not official or anything, but it takes most people a cold air intake, headers, exhaust and in some cases mild cams to reach the output I've got.



That's 150 WHP and 129 WTQ if you missed it at the bottom. This is a mustang dyno as well; expect a dynojet to read 15 HP higher. I'm some 31 - 46 HP over stock with engine management as my only modification and I believe there's another 5 hp or so left on the table. The power delivery isn't as perfect as either of danmartin's cars but the two issues have been taken care of since the last dyno pull. A new pull should result in a beautiful curve. The first minor hump is a lean condition I've taken care of, and the tiny dip in the torque peak was detonation that I've taken care of as well.

Anyway, that's the news. Since the tune (the tables at least) are about perfect now, you can plan on seeing the tune posted up here soon.

Cheers.