Here is the motor. Dart 200cc Iron Eagle heads, 218/224 .494/.501, ported MAF, '89 stock intake and runners, plenum is ported with a 52mm TB, SVO injectors, 48 psi, base timming is set at 6d... I know it isn't the best combination, but I'll fix that later.

This thing is runnig very lean. The coarse BLMs are 140-160 with the fine about 132-140. O2 sensor shows 150 mV and lower at steady throttle, however when I accelerate it does reach 600 to 800 mV. Plugs are 3/4s bone white with the rest a dark black.

Any ideas on why this is so lean? I'll try playing with the injector constants by making them smaller to hold the injector open more, along with some fuel pressure adjustments. Also, isn't the computer supposed to try and get things running a bit better, or at least throw a lean code?? I haven't been doing this tunning stuff very long so please bear with me. I know that the computer can only do so much without being told otherwise, but this is really bad.

 

You didn't mention what size SVO injectors...need to know.

What software (broadcast code or aftermarket manufacturer) are you running?

 

read this post:

Need tips on getting idle BLM to 128 on...

https://www.thirdgen.org/techbb2/sho...927#post698927

 

The injectors are 24 lb/hr, and was using ARAP but decided to use APYP ('89 vette with manual) since I read somewhere that it can be easier to start the motor using it. I have Craig Moates software and I am using GMEPRO to modify the .bin.

I looked at that link before I asked my question but at least those guys are fairly close to 128.

I did notice that I had the injector constant set to 25 lbs. because that was working pretty well with my previous setup, well a little rich.

 

Previous to that post i was idling at 160 blm.
Lower your injector constans till your driving range is close to 128
and then check your grams p/s @ idle in drive and park,in MAF table 1 raise those GPS values by the % your blms are from 128.
That method should get you in the ball park,if your gps # fall
between two #s on the table raise them both.

 

Right now I'm thinking there is a major vacum leak somewhere. I tightened up the ball flanges on the headers since I read that was giving someone else trouble too. I'll double check the headers tomorrow, along with intake, and all the TPI stuff. Another clue that there is a leak is that when I give it a good kick of throttle it goes pretty far rich according to the O2 sensor and a fluctuating idle. I saw about 600 to 800 mV.

Also I have a manual tranny, so would I let the clutch out a bit and see what happens?

When you say to adjust the g/s would that only be in the first cell only for idle? Right now it is at 93 then drops to about 35, then 50 and climbs from there. I think I would have to raise it to about 100 and then the next cell would be even higher, so how do I smooth out the cells?

Is this how I would lean out or richen up other rpm ranges too?

 

OK ,
If its a standard then only do it with the clutch in.
Your grams per second at idle should only be like between
4-12 grams per second,I think you are seeing counts not gps.
so if @ idle u r 6.2gps & 150 blm = 17% lean so multiply
6.2 x 1.17 = 7.25
counts gps
0 8.4
64 3.2
128 4.5
192 6.2 - 7.2 = instant fuel.
256 8.4
320 10.9
384 14.0
448 17.7
512 22.3

 

The instant you remove the screens, and do anything to the guts of the MAF you've totally messed up the transfer tables. While folks harp about being able to flow more air, the problem is you can't calibrate the meter to tell the ecm how much air it's really getting.

If you don't want the restriction of the MAF, run MAP.

If you want to stack two MAFs together and data log them then you can possibly work out the errors, and that's just possibly, the high flow numbers are so cramed together it's really hard to get things right.

 

Let me know how that works out for ya slowta,
It worked for the rest of us pretty well.

 

Hey guys thanks for the help. I now see why everything is so far off by porting the MAF. I noticed today (after tightening the loose runner bolts) that it was running a bit richer, around 150 coarse BLMs and 130-140 fine at idle, then a bit rich at tip in and while under throttle. I'll make a few adjustments to the MAF tables tonight and see what that does for me tomorrow.


Once again thanks for the help. I'll let you know how it all works out.

 

Am I supposed to take the coarse or fine BLM values? I used the fine and it didn't seem to help any.

 

Take where?

 

If you have your BLMs "locked" then use the fine (INT), if not, use the coarse (BLM). I prefer to lock my BLM once I get reasonably close because the INT does have an affect, and it has it's greatest effect once you are getting reasonably close to 128/128 say within +/- 10. But if your are further away, leave the BLM unlocked so you can get into the ballpark quicker.

 

Thanks for the help, I am nowhere close to 128. How would I go about locking the BLM anyway? I've heard people talking about it but never understood how or why.

 

You set the BLM Min and BLM Max in the "Constants" to 128 instead of the typical 108/160 (for TPI cars).

If you are close to 108 or 160, do not lock the BLM. You'll just trigger an SES O2 code because the ECM won't have enough range to change the fuel settings. Adjusting the BLM and INT Min/Maxes adjust the operating range of the ECM.

The INT works with the BLM and for initial tuning when you are getting BLM values more tha +/- 10 from 128 (i.e. below 118 or above 138) you should just make "coarse" adjustments based on BLM readings. But once you get in the +/- 10 range, you then are better off to lock the BLM as you can make "finer adjustments" to get 128/128 perfect.

Once you are with +/- 10, the INT can vary as much as +/- 5 before it causes an "update" to the BLM. Thus the BLM looses it's value as a tuning aid unless you consider the INT in the factor. When you are more than +/- 10 away, the BLM is so far out that the effect of the INT is not that meaningful. But once you are getting closer, then the INT is very meaningful if you want to attain 128/128.

 

Now I am to the point to lock my blms.My blm is about 126-130 under normal driving conditions.I just need to know what table to change the fuel for the load/rpm thats lean/rich.I have an 165 ecm w/6E bin.I now understand not to touch the maf tables for fuel delivery.But what table to use when fine tuning?I will be switching to sd soon.But I still would like 128/128 or close.

 

Well I adjusted the MAF rates at idle, and according to the O2 sensor it is idling just a bit rich. But the coarse BLMs are still up around 150 - 160. Fine stays around 125 to 132.

I still have to tackle part throttle since it goes lean when I give it some gas.

 

I guess it's the main spark table.

 

Hey 87_TA, i am trying your formula for 12 gps at blm 108 int 109 on my 87 GTA with the $6e ecu and i am getting way off the chart numbers. What do you think of this???

 

If at 12 gps your BLM's are reaching 108 then you are very rich,
if are using arap bin then on MAF table 1 you would lower the folowing counts by 15%,well actually go half of that being 12 gps
falls between (2) counts and go from there.
UNLESS you are rich everywhere from that gps and higher then use inj. constanst to get you close first.

counts gps


320 10.9 change to 10.1
384 14.0 13.0