I logged a few 0-100mph runs and some at idle today using Craig's software. I must say, my confidence is going way up on this tuning stuff, once I dived in. When I look at all the variables in the .csv file not all of them mean anything to me at this point. I did see 3 knock counts on each run at the same 3700 rpm spot. Each time the knock retard was about 20d and recovered by 4800 rpm. I think I'll retard my base timing 2d and see what happens. Comments?? My WOT 02 readings were ~875-900. The BLM fine always stayed at 128 and the BLM coarse was mostly 135 at part throttle and as much as 149 at idle. Comments?? How do the fine and coarse work? What should I look for as far as the air/fuel ratio and injector BPW ms? Does anyone have a similar setup as mine that can give me rough numbers for the .csv variables on a "tuned in" car?

I realize I can't make big changes until I start burning proms...thats next, but I want to understand this end of things first. I feel like I've came a long way in a couple days and can now see how I will continue to learn and move into programming. My goal is to clean up any problems I have control over this week and take the car to a dyno for a baseline. I'd like to be able to look back in 6 months and reflect on what I learn. Thanks...please be patient, I'm sure I'll have a ton of ??? for you guys.

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'87 Formula WS6 - ZZ4 Crate TPI, ported heads, LT4 hot cam, 1.6RR, Accel runners, Accel lower, ported plenum, Edelbrock 58mm TB, pulleys, SLP cold air, headers and full exhaust, gutted cat, Walbro 255, Koni yellows, aftermarket panhard & LCA's.

[This message has been edited by Steve10 (edited July 14, 2001).]

 

Never put all your tuning eggs in one basket.
NEVER
Always look at datalogging, as one element of gathering info.. Read the plugs, if you don't know how then learn, it's critical.

A stopwatch or GTech will give you more good data then dyno time. The Dyno does not have the airflow that the car does at 50 MPH. There are lots of things to effect a cars performance, and using a dyno masks may of them. For the $$$$$$$$$$$$ you spend on a dyno you can buy equipment for doing more meaningful stuff on your own.

 

Regarding all variables in Scanning Software....

To begin to understand these, IMHO, buy a book. These three are a great start...

Ben Watson's "How to Repair and Modify Chevrolet Fuel Injection" (Motorbooks International)
Howell Engine Developments, Inc. "Tuned Port Fuel Injection Service Manual"
Jeff Hartman's "Fuel Injection Installation, Performance Tuning, Modifications" (Motorbooks International)

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Good suggestion, I'll try to get the book this week. Any comments on my question about the BLM? I've been searching past posts and I see alot about the BLM INT, but nothing on BLM fine & coarse. If my coarse is 135 and the fine is staying at 128 does that mean I'm rich and it's leaning me back to 128, or is it the other way around? Actually, should I be posting these kind of scanner interpretation ??? on the TPI board? I guess it has little to do with burning my prom.

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'87 Formula WS6 - ZZ4 Crate TPI, ported heads, LT4 hot cam, 1.6RR, Accel runners, Accel lower, ported plenum, Edelbrock 58mm TB, pulleys, SLP cold air, headers and full exhaust, gutted cat, Walbro 255, Koni yellows, aftermarket panhard & LCA's.

 

I've been looking for the answer on the blm,s also. Can't seem to find it. MAYBE some one will tell us. Thanks Guys.

 

There is no such thing as BL fine and coarse, I don't know who's yacking about that, but there have been several posts about these terms.
ANYWAY:
You have BL and Integ, as far as fueling corrections. BL is long term, Integ is short term.
If you BL is 135, and Int 128 then your just a shade lean, and a minor correction has corrected it. You **usually** fin the Int at 128 once things have stabilized, if not then you probably at the BL full correction, and just totally out of any more fuel correction.

The fueling corrections are short term, Int, and long term, BL (Terminology wise).
HTH

 

The BLM variable labels in Craig's software .csv file are "coarse & fine" and since that's all I've been exposed to, I asked the question. Thanks for clearing it up.

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'87 Formula WS6 - ZZ4 Crate TPI, ported heads, LT4 hot cam, 1.6RR, Accel runners, Accel lower, ported plenum, Edelbrock 58mm TB, pulleys, SLP cold air, headers and full exhaust, gutted cat, Walbro 255, Koni yellows, aftermarket panhard & LCA's.

 

I've been searching for info on the blms for days. Reading a lot of posts, very confused NOW! I'm using Craigs software for scanning and it shows coarse and fine. I guess I don't understand. Does the coarse control the fine? I'm running a modified arap chip, my car seems to run real good once in closed loop. But the blms are all over the place. The coarse 128 fine 128 and then,the coarse may go to 130 132 140 and the fine will follow. I have a data file, if someone would be so kind to look at it and see if I'm going in the right direction? Thanks. I finaly got this car on the road after a year.

 

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87 GTA 355/700r4
ported&polished 083 heads
xe268h comp cam
1 5/8 blackjack alumicote
homebuilt y pipe,pasesetter 3in mandrel cat back.
ported/manifold,upper plentum, tpis maf.
airfoil, 24# svo injectors, home programed chip, underdrive pulleys, erson roller rockers, chromemolley pushrods,2100 stall, shiftkit, 373 10 bolt.

 

This tread is a very valuable thread. It is quite long, and if you really get down and dirty with it, has some awesome information in it. In my opinion, it doesn't matter if you are running SD or MAF...realizing how both systems work will help any tuner out.

https://www.thirdgen.org/messgboard/...ML/000637.html

I think you will find the info you are looking for in there. -Matt-

 

In a nutshell...
You start your car up. Since the O2 isn't at its active temperature, it would provide erroneuos data to the ECM. Therefore the ECM does not use the O2 sensor. It runs off of inputs from the IAT, ECS, TPS, MAP/MAF and RPM. Assuming the RPM is over 400, the EST is active and the ECM controls the timing. The output from the ECM is for the fuel injectors and the EST. Notice that since the O2 isn't active, the computer can not do anything regarding fuel trim. It uses tables in the calibration to *guestimate* what the engine needs to run correctly based on the previously mentioned sensor inputs.

Now, the O2 gets hot enough. It starts to proviode useful info to the computer. The O2 toggles at stochiometric A/F ratio and then the computer starts adjusting. At 128 BLM, 128 INT (Blm would probably be coarse), the computer is saying quit your day job and start tuning full time, because your calibration is so good, no adjustments need to be made.

As the BLMs go lower, the O2 is telling the computer that you are rich. The computer will try to lean the fuel out.

Imaging BLMs and INTs like this. Say you have to measure out a cup of flour for a cake. You get out around a 1 cup measuring cup (representing BLMs or *coarse* trim) and a 1/2 teaspoon measuring spoon (representing INTs or *fine* trim). You have a lab-calibrated 1 cup exactly container that you are going to put the flour in to. You don't have a lot of time, so you dig in to the flour with the 1 cup measuring cup and quickly dump it into the container. You were in such a hurry that you realize that you need to take some flour out. To take the extra flour out, you use the 1/2 teaspoon measuring spoon until you get it perfect. It would take a lot of time to get the mix exactly right if you kept using the 1 cup measuring cup.

Now say your wife/GF came in and didn't know what you were doing. She dumped the whole bag of flour into the container. Now it is not feasible to use the 1/2 teaspoon so you have to use the 1 cup teaspoon. Therefore, your BLMs will change again and then the INTs will kick in. Get my drift?

 

Thanks for the quick reply, and link. I've read alot of these post. Unfortunalty maf and sd don't seem to tune alike to me. I'll spend the next several days going through old posts. Maybe I'll be able to learn the answers. Thanks


Well let me see if I understand this correctly. This is what I have.
rpm= 3800
throttle=45.31
maf=79.125 gm/s
t spark=31.99
02= 857
blm coarse=132
blm fine=128
lv8=209
pulse=3952.34
a/f=12.35
with these numbers I think I'm running rich and the puter is trying to lean so I can get an a/f of 14/7 correct? Thanks

[This message has been edited by cp87GTA (edited December 01, 2001).]

 

With those numbers at THAT moment, yes...you are running rich and the BLMs are over 128 meaning your ECM is trying to lean things out. Look at the broad scope of things. Hold it steady at the same throttle opening and the same RPM long enough for that value to stabilize. That is where the best BLM and INT results will be found. Cheers, -Matt-

 

Thanks Matt. I just wanted to make sure I was looking at it the right way. My car seems to run pretty good in closed loop, but I am only getting about 15mpg. Not bad but I was hopeing for much better.

 

You should find all the info you need if you do a search for posts on MAF stuff. Look for posts from GregW or PJ. If you can get your BLMs (course) to vary +-10 from 128, then you are doing good. I don't think you are too far off. I tweaked my MAF tables to get the BLMs 122-134 over a wide operating range. I wouldn't worry too much about the INT numbers yet.

Getting your BLMs nailed down should be your first priority, since these numbers affect many other conditions, IE open loop and highway mode.

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Best ET 14.413 @95.57 without
pulling valve covers or manifolds.
Also with stock 2.77 rear end!!!

 

There is one more level of complexity you should be aware of. There isn't one single BLM, there are actually 16. These appear in the log file as BLM cells 0 to 15. The ECM uses these as a 4x4 table with engine speed increasing to the right and engine load increasing going up, ie. the lower left (cell 0) is idle BLM while the upper right (cell 15) is high load, high RPM.

Make a log with widely varying throttle and RPM, then sort on BLM cell in a spreadsheet, then graph vs RPM and MAF rate and you'll see what's going on.

I'm assuming the '87 WS6 is a MAF system - MAP takes a different approach.

The closed loop BLM values you reported are on the lean side. I'm wondering whether you went to higher flow injectors to match the other mods? Maybe you just need to get a bit richer at WOT to suppress the knock. Wide band O2 measurement would probably be helpful. I'm assuming the dyno test will provide this.

Jim
Red '86 4+3

 

With the RPM and LV8 value you have, I'd say you were in Power Enrichment mode at that point, which is why your a/f ratio is that low. In PE mode, your BLM and INT values (BLM is the coarse, INT is the fine) are not updated, but with the numbers you have, your tune is pretty good at the airflow range.

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Greg Westphal
'87 IROC 355TPI/A4

 

I think I may have been in pe there too. I've burned a couple of differant chips since then. I richened it up the first one by 1 point, and it started to blubber at 30mph intown. int was constantly 138 to 145. So I leaned it down 2 points, car runs much better. Int is between 126 140, blm is all over the place. I do have a tpis modified maf. I think I'm going to put my stock on back on, and see what happens. I'm trying to use arap.bin. I maybe trying a differant code soon, altough it seems to run realy good with the arap bin. Underdrive pulleys may be having an effect too, I noticed pump voltage to be less than 12vdc sometimes. Thanks for the replys, I've got a lot to learn but I'm glad I kept the mfi.