Can someone take a look...

[foxspy]

Hey guys,

I was wondering if someone can take a look at a couple data logs and whole files and see what you guys think.

The setup is:

502 BBC
1000cfm TB
FAST b2b w/ WB
40lb/hr injectors
48psi fuel pressure

I also have a NX plate kit. That's where I'm getting stumped. The air/fuel is going WAY rich w/ the nitrous.

Thanks.

Lee

 

[norbs]

where are the logs?

 

[foxspy]

You have mail.

 

[norbs]

Well, i got the logs. You have something funky going on at top end. The rpm and looks like a saw tooth the last portion of the track. The o2 correction is flatlined at -13%, and its probably to rich on the NOS jet still for sure. But you need to check what is causing your pulsations at top end, valve springs ok?Seems on the NOS log the pulsations are more.

 

[foxspy]

The valve springs should be okay. They have about 3k miles on them. The motor sounds fine going down the track. I had the logging on 15 frames/pec. On the NA run I reved alittle high and started to get valve float on the 1-2 shift, but the nitrous runs were fine.

The IATs were higher on the nitrous run just because there wasn't that long of a cool down.

Any suggestions for the gct?

 

[ski_dwn_it]

I too would like to take a look at the logs.

What system are you using....I have Gen 7, and my RPM are also VERY sawtooth looking through the entire run.

Not sure what I have my Data log sample rate on, I suppose it is stock setting. The other parameters look nice and smooth, but the RPMs area all over the place. I have seen other logs that looked like this and assumed it was just the software....but sure would like to find a way to smooth it out, or find out if its something on the car doing it.

Could it be the distributer pickup?

 

[norbs]

Its either 20 or 10 frames per sec on the Gen 7 , but if your using the lm-1 connected to the gen 7, i am not getting good clean results either. Once i get a 2nd o2 bung welded in i will compare it to the brick from accel. Ski you may have to go the brick, just it hurts in the wallet!

 

[ski_dwn_it]

Norb....

I seem to be getting real good results with the lm-1 - the fuel is VERY close to my commanded A:F.

I have gone to a different track this past weekend, and in 3500-4000 DA weather ran 10.58s. Went 4 rounds till a crash at the top end with two other cars, made them call the race - the remaining cars split the purse - and I came home with a nice check.

The car ran VERY VERY consistant. First two runs were within .002 through every interval, and as the humidity came in VERY heavily, the fuel seemed to adjust accordingly. At least as good as I could expect it to.

The one thing I did see is the "correction" for the A:F, seems to slightly occillate above and below the target A:F....

On the initial hit the car goes rich, perhaps a decrease in pump shot would help, then it goes to a little lean, and then as the run goes on, the devatiation from target gets less and less. I will try to post some logs.

When I say deviate, I should also clarify this is a change of about .2 A:F, which I doubt is causing much of any problems.

Norb, very interested in seeing what you find with the different WBs.

Regard...

 

[BoostKillsStres]

Ski,
The correction is basically a give and take kind of thing. It needs to be able to correct fast enough for the lower gears since your only in them for a blink of an eye and not correct too fast for the higher gear for the upper end. Correct too fast and the correction occilates across the target too fast and too far and creates a big sawtooth graph you mention but correct too slow and you might have prolonged lean or rich spots as it can't get to the target quickly enough. So, give and take.

I don't have any idea how the afteramrket FI systems do their timing loops for this correction, would be interesting. I was thinking the timing loops could change based on mph rate of change that way during quick accel it would react fast and on the top end charge it would react slower for better accuracy in staying on the A/F target.

Fun stuff...

 

[norbs]

The gains are very difficult to set up as on the gen 7 dfi you have three settings of PID gains, proportional, integral, and Differential. Gain is based on estimated engine airflow, and you can watch the airflow as you drive on the charts. But These charts i noticed are very sensitive, so you may only want to do small changes.

 

[bobc455]

Originally posted by foxspy Hey guys,

I also have a NX plate kit. That's where I'm getting stumped. The air/fuel is going WAY rich w/ the nitrous.

Whoa!!!

I will warn you right now! I had the same problem, and it wound up costing me a motor (really stupid).

My WB was showing pig rich on nitrous (9.1:1 with -10% correction), and actually the motor was fine. Well, stupid me says "the motor is too rich" and I turned down the nitrous fuel pressure a few runs, until I got it down to 10.8:1 and cracked my cylinder wall.

DON'T MAKE MY MISTAKE!!!!

I don't trust the WB on nitrous at all. When I looked at the plugs, I was dead lean, even though my log showed 10.8:1.

I don't know why the readings went to hell on nitrous, but they did.

My recommended procedure:
1) Tune the motor dead-nuts (<3% correction if you can) without nitrous.

2) Verify by reading the plugs.

3) Go into open-loop when running nitrous (or change your WB settings to have zero percent maximum negative correction).

4) Tune by reading your plugs ONLY, and forget what the WB says when you are running nitrous.

Some people have had success with a WB on nitrous- it cost me a motor.

-Bob Cunningham

 

[foxspy]

Will the plug readings still be accurate after driving down the return road back to the pits, or do I need to stop at the end of the track and pull of the return road and check them?

 

[ski_dwn_it]

Best thing to do is shut it off as you go through the traps, coast to a return road and pull off to the side, and pull a plug. I have done it both ways, running back the pits, dependind on how bad the car is running in cruise, shouldn;t effect it much - but you do introduce the possibility of masking a lean condition by running back to the pits.

 

[norbs]

it is very strange for the a/f to go flaky on the n20 i wonder if its the extra o2 doing it