Souless

iTrader: (2)

Ok I have a new 408 with 39.82lb/hr @ 58PSI injectors. I am trying to tune with an LM1 WB which is hooking into my HPT in SD mode (MAF unplugged) When I start the car it surges is running REALLY rich. About 11.5 to 13.1 from time to time as it surges. I have dropped my VE into the low 20's at the KPA its trying to idle and the surrounding cells, but it still is running really rich.

We started to look at the injectors and as I increased the values from about 39 to 54, my car started to idle alot better and the AFR got to the high 14's low 15's which is where i want it.
BUT
As soon as i pulled it out of the drive way the car wont go 10ft without trying to stall out. The AFR goes WAY lean into about 32 or so, and the car just wont move much.

I have been using the Inj. spreadsheet from Marcin found here:
http://www.transamws6.net/HPTuners/injectors.xls
to try and calc the lb/hr, but when i plug these values in the car starts going really Rich again.

Any ideas? Are we tackling the right issue with the injectors?

Thanks

ZL1Killa

iTrader: (17)

have you used the injector sheet on hptuners or on here under the fuel and injector sticky thread? are you using the proper values?

what exact injectors are they so we can kind of help here

jimmyblue

iTrader: (11)

You want to adjust the injector numbers based on the
"normal" operating regions and idle ain't one of them.
Too many nonideal things at play, like short-pulse
effects, cam effects on airflow and so on. You should
measure fuel pressure, calculate up the delivery-at-
said-pressure from the mfr numbers, populate the table
and call it good.

New injectors are going to have different offsets etc.
but there's little or no data to be had there. Unless
yours are used on some GM platform. If so then you
go find a stock tune and rip off the info.

VE table is the likeliest "handle" for idle mixture
problems. But also realize that in closed loop with a
big cam your O2 sensors are getting spoofed by the
overlap air and 14.7:1 in the hole is not going to
"read" 14.7:1 out the pipe. Reading being a stackup
of assumptions and calibrations based on complete
internal combustion, not a mix of before and after
products. To this end you might want to push down
down the O2 sensor switchpoints until you get a
reasonable agreement between the meter and the
commanded (14.7) AFR, or maybe a bit to the lean
side on the meter if you have a "big" cam to give
some windage for the shot-through air.

Souless

iTrader: (2)

I think my values are right. I am using the injector spreadsheet i got from the stickies, and I am going off the info I got from my previous post, since i couldnt remember what the injectors where:
https://ls1tech.com/forums/pcm-diagnostics-tuning/972231-l76-w-40lb-inj-fuel-rails-psi-question.html

I inputed my values into RHS sheet and get the following values:
39.80748 40.05551 40.30353 40.55155 40.79957 41.04759 41.29561 41.54364 41.79166 41.97767 42.22570 42.47372 42.72174 42.90776 43.15578 43.40380 43.65182

Which look about right, however, i am still running rich on startup and when I take off from a stop, it goes REALLY REALLY lean, and almost dies, then catches back up. I am thinking this is a problem with the VE and looking at the STFT which showing -35 when I stop, i think that the PCM is not having enough time to catch up when i push the pedal and get the rush of air.

Not sure, this is all in theory but its all i got for now.

white01ss

iTrader: (37)

Like jimmyblue just said...

Had the same problem a while back and it turns out the narrowband O2s were causing rich idle when used with headers. Check out the last few post of this thread. The O2 Switch Point table is very sensitive so only make small adjustments. Dan

http://forum.efilive.com/showthread.php?t=7574&page=4

Souless

iTrader: (2)

im working on tweaking my O2s, but just curious how the O2's cause the rich condition if you run in open loop? Also, i want to say thank you for all the help, this problem has been killing me!

Souless

iTrader: (2)

Well i have been messing with the O2s and the VE table all afternoon and still no solution. Still running really really rich 12.80-13.1 and when i give it throttle it goes really lean then spits! Damn it!

Souless

iTrader: (2)

I am attaching my tune and the last scan I did, in case anyone wants to take a look. Its just getting aggravating.

Billiumss

iTrader: (11)

What brand injectors?

Souless

iTrader: (2)

The are the GM factory injectors that came with the LS2s.
Here is the link from Scoggin Dicky:

http://www.sdparts.com/product/12576341/INJECTOR.aspx

Here is the assembly i got:

http://www.sdparts.com/product/12590...L76L92Car.aspx

DrkPhx

iTrader: (15)

Are you actually seeing 58 psi at the fuel rail? For accurate IFR numbers, you need the actual fuel rail pressure.

Souless

iTrader: (2)

I dont have a fuel pressure gauge, so i cannot say that for sure, that is just what they are rated at.

DrkPhx

iTrader: (15)

You need to buy a cheap fuel gauge that screws onto the fuel rail and monitor fuel pressure. Then input that value into the calculator for new values for your tune. I'm not saying this is the cause, but it certainly would give you a more accurate IFR for those injectors on your car making it easier to tune.

Souless

iTrader: (2)

Ok i bought a gauge, and it is reading 58-60 at the fuel rail. The input value i was using before for the IFR was 58. I have adjust the IFR table from 58 to 60 and still seeing the same issues. Oh BTW i am still tuning in SD so no fuel trims.

Any ideas guys?

Souless

iTrader: (2)

well i think i FINALLY got part of it figured out. I was only reducing the primary VE tables not the secondary tables. Big NewB screw up on my part. Once i droped the 2ndary tables about 15% it finally started to lean out to high 14's low 15's.

However, since I am tuning with my MAF unplugged when does the car acutally use the primary tables instead of the secondary?

HUGGER ORANGE SS

iTrader: (2)

The reason the Secondary VE table is working is that table is used under certain conditions like a MAF un Plugged. 2001+ has only 1 VE Table. When you plug the MAF back in it will revert to the Primary VE Table.

Also you should set the Injector table to where it should be, too rich or too lean just to offset your initial start up will cause havoc on the rest of the drivability.

OK

Another table you forgot to look or alter is the
Open Loop F/A VS ECT vs MAP Table. Need to lean this out, (lower numbers by about 10 to 15%, or just play with it till it becomes right) This is under The FUEL CONTROL / OPEN AND CLOSED LOOP.


Also Alter the Afterstart Enrichment Tables, In the FUEL CONTROL / GENERAL FUEL

2 other things you can play with is the VE (which you have done), and MAF tables,on the low side of the scale, then poll smooth..



Good luck.

Clint

Souless

iTrader: (2)

THanks for all the great info. Although I am curious, what is the difference between editing the Open Loop F/A VS ECT vs MAP and editing the VE table? If i get the VE table at the right AFR do i still need to edit this table. Just trying to understand a little more.

HUGGER ORANGE SS

iTrader: (2)

The VE table works in conjunction with the maf table to deliver Fuel at certain loads and rpms. Yes you can lower the VE tables in these areas to lean or richen you up. Funny as it may seem but the VCM looks at VE/MAF/OPEN LOOP A/F Tables and others, lots of different tables to deliver proper A/F. But when you 1st fire up a car it runs in open loop until you reach around 149 deg Engine Coolant Temps, then it goes closed loop. If your having trouble with it being too rich as startup, I would alter the mentioned tables only 1st in my previous posts. Once it does go into closed loop, if you have the VE/MAF tables altered too much in these idle cells the Ltrims will compensate for it anyway.

Take care.

Clint