Kevin91Z

iTrader: (1)

I've tried lowering the VE tables but that just causes the BLM's to go up to compensate. I have 24lb injectors and the car is too rich at idle with a pulse width of 1.8 to 1.9. I'd like to see more like 1.5 to 1.6. What can I do?

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

TRAXION

Kev,

This is somewhat confusing. The BLMs go up to compensate because the O2 is saying that the car is running LEAN at idle. So, I think that there are some other questions that need to be addressed....

1) Why is the O2 reporting LEAN (causing the BLMs to go up) when you believe it is running rich?
2) Along with #1 above - WHY do you think you are running rich at idle?

Answering those questions is a great start. I'll jump back in with more info.

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

Kevin91Z

iTrader: (1)

Just by the sound of it. It "blubbers" and "stutters" like it was getting too much fuel, and the O2 sensor is staying more in the 6-800mv range than it is under 500mv. Like, out of ten O2 samples, 7 of them are above 600mv and the other 3 are below 500mv. Make sense? But the BLM is running in the 146 range at idle, indicating the computer things its lean and is adding fuel.

Kevin91Z

iTrader: (1)

Back to the top....

The weird thing is, if I raise my injector constant to cut some of the fuel, then the BLM value goes up. If I lower the injector constant, the BLM goes down, but the car sounds like it runs richer and blubbers worse. Help!

leirch

Kevin,
I'm having the same problem with my MAF system!! I'm gonna keep an eye on this post to see if i can figure out my problem also.

Brendan

NickG

Guys,

It sounds like your fueling is okay, but maybe your spark timing is retarded. Try adding a few degrees at idle and see if it helps.

Nick

TRAXION

Kev - I don't understand. What you described is completely normal and expected. What is wrong?

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

Kevin91Z

iTrader: (1)

After playing around with injector constants today, I found that telling the computer my 24lb injectors are really 21.5lbs made the BLM and INT the happiest near 128. But I dont know how that will affect WOT yet.

What I was asking above is why when I tell the computer that my injectors are 24lbs, the BLM value would shoot up in the 145 range. When I changed the value to 25.5lbs, the BLM went to 150+. When I changed it again to 23lbs, the BLM went down to 138, and so on, down to 21.5lbs where it settled at about 127-130. This is all at idle, and the injector pulse width was steady at 1.8-2.0 each time. Why does the computer try to add fuel (BLM value above 128) when I tell it the injectors are larger?

Pablo

iTrader: (1)

Because your main fuel tables are probably lean (provided you are sure your injectors are 24 lb injectors)
btw expect some burble.. thats what happens with a larger cam. Its also called lope. STart disregarding sounds as your only tuning aids unless you wanna waste alot of time. Just because you think it sounds a certain way doesnt mean it IS a certain way so you always need another way to check your sound hypothesis. What NickG said is probably right too.

and if you have 24 lb svo injectors bear in mind they actually flow more at the pressures found in TPI systems.

[This message has been edited by Pablo (edited April 17, 2001).]

GregWestphal

iTrader: (1)

Hmmmm, that kind of flow rate is close to what the SVO 19# injectors would flow at the GM pressure. Unless your 24# injectors (and/or your fuel filter) are seriously clogged, you might have smaller injector than you think. One question I just thought of: Are the BLM values you're giving just at idle, or for a few or more BL cells? If it's just at idle, then never mind what I said above. In this case, I think you'd need to work on you VE table; Tim or Glenn can help you figure out what you need to do to what cells of the VE table...

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Greg Westphal
'87 IROC 305TPI/A4

Kevin91Z

iTrader: (1)

The number on the injectors has been verified to be 24lbs LT1 injectors, but they werent cleaned before installation. I changed the fuel filter at the same time I put this engine in, February.
I'm not using only the sound of the car to tune it in, we have Diacom and reading spark plugs too and everything else. The timing according to Diacom is in the 21 to 26 degree range, it keeps changing. The block learn values above are all at idle.

Yelofvr

Kevin, Lets say you do nothing to your engine and you just tell the ecm that you now have larger injectors, from 22lb to 24lb(approx 10%) You do this by burning the chip with the new injector constant. So, the computer says ok at idle I have the same air coming in, but I have larger injectors, so I will REDUCE the pulsewidth by 10%. SInce you really didnt add bigger injectors, the car will run lean, the O2 sensor sees this and the ecm says ADD fuel. It does this until the O2 is happy. Adding fuel is indicated by larger BLM's, so everything is working as it should. In the end, the pulsewidth will be the same in each case

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Dave Zelinka

TRAXION

Yelofvr is absolutely correct. That is why I said that everything is behaving as it should be. If you LIE to your ECM and say you have smaller injectors then the computer will increase the pulse width across the board. This will make your car run rich. When the ECM goes into closed loop the BLMs will go down because the ECM is trying to adjust. If you LIE to your ECM and tell it you have bigger injectors then the ECM will DECREASE the pulse width across the board. You will run leaner. When the ECM goes into closed loop the computer will respond by increasing the BLMs so that more fuel is supplied.

Set your injector constant to 24lb/hr. Start the car and allow it to enter closed loop. Follow the outline previously posted under the P730 post for adjusting part throttle fuel.

The ECM is reacting normally. You need to set the injector constant and leave it alone. Then adjust the VE tables to solve any fueling issues.

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