[Gmecm] Tuning a larger MAF on L98

[Mike Poore]

Excellent point. I would have to calibrate the sensor to reach max 
voltage at some expected max air flow. The sensor seems to be responding 
properly, albeit with lower voltages than normal. I haven't graphed it yet.

The ecm is an '870. I increased injector size from 20# to 42# and 
lowered pressure about 10 lbs. I should mention that the hesitation was 
present before replacing the injectors. I thought injectors might 
improve it, but it didn't.  I need a healthy squirt of fuel when that 
throttle opens. I may need to raise the fuel pressure eventually, but I 
think the hesitation should be addressed differently. I am going to have 
to start experimenting and see what works. It takes a lot of time to 
burn chips.

Here are the some of the options that can be changed from the programs I 
am using:

GME:
1. Injector flow rate
2. Base injector pulse width vs load. The load table runs 0 to 160 
incrementing by 10.
3. Power enrichment vs rpm
4. WOT TPS enable

Mastertune:
1. % change to AFR at AFR vs rpm
2. Injector pw vs. load values These load values go from 0 to 256.

Can anyone define the load values these programs use? Is it a calculated 
value based on multiple inputs? While some or all of these parameters 
might need adjusting, what do you see that might prevent that hesitation?

Rick McLeod wrote:

>IMHO, you would be better to modify the fuel parms
>than the output of the sensor, as when you reach the
>top of the output, you may not be at the top of the
>full flow of air, hence a flat line from near WOT to
>WOT. Have you graphed the flow of the new MAF sensor,
>to make sure the output is relative to flow? Before
>modifying anything, I'd make sure the sesor is
>performing the way you expect it to.
>
>BTW, what ECM and code are you using, I would assume
>some variant of '165 code?
>
>Also, have you increased the size of injectors to
>match the air flow, etc? What about fuel pressure
>increase. It all works as a system. 
>
>--- Mike Poore <mp at FlowersByValerie.com> wrote:
>
>  
>
>>I have a heavily modified 85 L98 engine. I
>>fabricated a new MAF housing 
>>and ducting from the throttle body to the air
>>cleaner. I removed the oem 
>>sensor from its housing and installed it in my
>>fabricated one. I don't 
>>have the exact measurements handy, but the new MAF
>>will flow about 
>>double the stick unit. The engine idles well, but
>>has a severe 
>>hesitation when opening the throttle. The faster you
>>open the throttle 
>>the worse the hesitation. Obviously, it needs more
>>fuel, but what is the 
>>best way to compensate?
>>
>>1. Increase fuel enrichment, or
>>2. Modify the MAF to better reflect actual flow.
>>
>>I have Mastertune and GME for editing. I am trying
>>to figure out what 
>>exactly I need to change to get more fuel when the
>>throttle opens. Any 
>>advice?
>>
>>I looked at modifying the output of the MAF. My
>>understanding is that as 
>>airflow increases, so does voltage. If the new MAF
>>housing has fifty 
>>percent more area than old, how much do I raise the
>>voltage? Any 
>>suggestions on how to send a voltage to the ecm that
>>more accurately 
>>reflects air flow. Ideally, something adjustable
>>would be great. I wish 
>>I knew more about electronic circuits because this
>>is probably very 
>>easy. I also think that this would the better
>>approach because it should 
>>not require so many other prom agjustments.
>>
>>Thanks for any input,
>>
>>Mike
>>_______________________________________________
>>Gmecm mailing list
>>Gmecm at diy-efi.org
>>http://lists.diy-efi.org/mailman/listinfo/gmecm
>>
>>    
>>
>
>
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>
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