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How to change blm at part throttle?

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How to change blm at part throttle?

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Old 08-10-2018, 10:11 PM
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How to change blm at part throttle?

Hi, I have an 89 camaro with a 165 ecm. I replaced the original 5.7 with a gmpp 350 H.O. I reused the tpi. Has the vortec heads and ford 24# injectors. I have 128 blms at idle and 128 blms at WOT. But at part throttle cruising ( about 10% to 25% throttle and between about 1200 rpms and 2500 rpms im running between 108 and 114 blms. Any suggestions on changing those using the 6E mask? Thank you
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Old 08-11-2018, 08:54 AM
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Re: How to change blm at part throttle?

Need to work on the MAF airflow tables. Hit the tuning guide book sticky, lots on information on the '7165 ECM.

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Old 08-11-2018, 12:23 PM
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Re: How to change blm at part throttle?

I assume your injector constant is already set to 24lb?

are the injectors Bosch III type?
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Old 08-11-2018, 10:44 PM
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Re: How to change blm at part throttle?

At WOT, shouldn't your BLM's be lower than at idle? At WOT, the engine needs more fuel than normal. So you need to enrich at WOT. Someone please correct me if I am wrong. I agree with RBob that your airflow tables need to be edited.
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Old 08-13-2018, 12:56 AM
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Re: How to change blm at part throttle?

BLM is locked to 128 under WOT as the fuel mixtures are way outside the range of the narrow band sensor. The ECU is blind at WOT and these BLM's mean nothing. 128 idle is good, but you can expect the part throttle AND WOT to be off. You need a wideband to do proper tuning at WOT.

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Old 08-13-2018, 12:33 PM
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Re: How to change blm at part throttle?

Not always, many GM code bases will use the current BLM at WOT if it is greater then 128.

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Old 08-13-2018, 03:04 PM
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Re: How to change blm at part throttle?

Good point - it's either 128 or it's higher than 128 - the use of the last BLM at WOT if it's got a perceived lean condition does make sense as a failsafe. At any rate you can't really trust a reading of exactly 128 at WOT because it may or may not be indicating what's actually happening. The ECU is still guessing and blind under WOT. Generally you want around 12 AFR at WOT and you're not going to read anywhere close to that with a narrow-band. Looks like the injectors and this engine are running rich at part throttle cruise so when he goes into WOT the BLM is locked to 128 which may be too lean for this engine..... but there's literally not way to tell without a wideband or maybe reading the plugs to get a rough idea. Wideband is much less work.

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